which one is not the characteristics of epidemiology ?
what is the fundamental difference between observational and experimental methods in epidemiological studies ?
what is the difference between epidemiology and clinical medicine ?
please describe the major function of epidemiology
the relationship between numerator and denominator in rate
the relationship between incidence and prevalence
is it correct that the mortality rate of hydrophobia is 100%
what are the two parts of da?
what is the study to compare the history of oral contraceptives between patients with cervical carcinoma and other patients hospitalized at the same time in order to explore the relationship between oral contraceptives and cervical carcinoma ?
what is the numerator of incidence in an exposed population during a certain period ?
the definition of prevalence is
a approach to comprehensively describe the distributions of time, population, and region for a disease is
which of the following characteristics do descriptive studies have?
what are the advantages of the prevalence survey study?
which is the method of yzing and researching in groups without inidual data?
which is the characteristics of the sampling survey that are not included?
which is the way to early detection and treatment of patients?
in order to ensure that the sample can reflect the overall situation, what should be considered in the ysis?
to test the cause of a hypothesis, who should be included in a cohort study?
regarding the historical cohort study, which is wrong with the statement?
from the methodological point of view, what type of research does the cohort study belong to?
which is the most common bias in cohort studies?
describe the factors influencing the sample size.
what is the nested case-control study?
the advantages and disadvantages of using prevalent case
what are the advantages and disadvantages of matching
can you distinguish the matched and unmatched case-control
what are limitations of case-control studies?
a case-control study is characterized by all of the following except:
which of the following is a case-control study?
state the main advantages and disadvantages of case-control studies
which feature cannot be found in randomized controlled trials
the difference in epidemiological experimental studies compared with prospective cohort studies is
describe the characteristics of clinical trials.
the incorrect statement about screening test is
when the consequences of misdiagnosis are serious, the test is required to have a higher
the indicator that can be used to evaluate the accuracy of the diagnostic test method is
carry one screening test, which principle should be followed?
which one is correct about necessary cause ?
one factor and a disease are both related to another factor.the resulting statistical asssociation between the disease and another factor is called
describe the hill's guidelines briefly.
农业按照环节划分包括：
农业生产仅面对自然风险。
农业的市场贡献包括工业品市场和农产品市场。
农业所具有的非商品产出功能包括：
农业经营体系包括：
农业按照环节划分包括：
农业按照产业划分可分为：
农业生产在空间上具有：
农业经营体系包括：
动物饲养业仅包括家畜、家禽的养殖。
农业生产仅面对自然风险。
农业具有消除贫困和替代社会福利保障的作用。
农业生产要素包括劳动、土地、资本、技术等要素。
农业最基本的贡献是外汇贡献。
农业的市场贡献包括工业品市场和农产品市场两个方面。
农业按照环节划分包括： a. 产前环节 b. 产中环节 c. 产后环节 d. 生产环节
农业经营体系包括： a． 家庭经营 b． 合作经营 c． 集体经营 d． 产业化经营
农业的市场贡献包括工业品市场和农产品市场两个方面。
农业所具有的非商品产出功能包括： a.环境功能 b.社会功能 c.粮食功能 d.经济和文化功能
生产者对农产品价格的预期会导致供给量与价格反方向变动。
农产品生产要素价格上升，将引起农产品供给：
农产品需求是指在某一特定时间内，在一定价格水平下消费者愿意并能够购买的数量。
替代品价格上升时，该农产品需求量：
供给缺乏弹性是指：
农产品供给价格弹性是指农产品的市场供给量对其价格变动反应的灵敏程度。
某种农产品替代品数量越多，可替代程度越大，需求弹性越小。
当需求不变时，供给增加，均衡价格和均衡数量：
增产不增收，对不同的用户影响不同。
当某一农产品价格下降时，该农产品供给量会：
替代品价格上升时，该农产品需求量：
供给完全无弹性是指：
当供给不变时，需求增加，均衡价格和均衡数量：
农产品供给表达方式包括：
农产品供给指在某一个价格水平下，生产经营者愿意供给的数量。
需求不变的情况下，农产品大丰收，数量增加，价格下降，收益增加。
某种农产品替代品数量越多，可替代程度越大，需求弹性越小。
在其他条件不变的情况下，农产品供给量与价格同方向变动。
农产品供给会受自然环境和调控的影响。
农产品供给表达方式包括： a． 供给表 b． 供给曲线 c． 供给函数 d． 供给图
供给完全无弹性是指： a. es=1 b. es>1 c. es=0 d. 0 某种农产品替代品数量越多，可替代程度越大，需求弹性越小。
to spell the past form of the following words when used as verbs, to which one should we first add –k- then -ed?
guests ______ and screamed when the bomb exploded.
of the following words, the underlined part of which one is pronounced differently in american english and in british english?
how is the word schedule pronounced in american english?
the discovery of penicillin, famously, was a happy ______.
they are looking for a happy ______: a house that is not too big but that has lots of storage space.
i wish you many happy ______ of the day.
until his appointment becomes official, ted is keeping a low ______.
a tiger ______ but a wolf ______.
to clean the water bottle which has been used for a long time, white vinegar can be used to remove ______ from the inner surface of the bottle.
the map is drawn to the standard ______ of 1/100,000 so there is not much detail.
nuclear weapons cause destruction on a massive ______.
the sails ______ themselves with wind.
the book is ______. you should have returned it to the library last week.
he had lived illegally in the united states for five years after his visitor's visa ______.
he tried to keep a(n) ______ between work and relaxation.
she ______ her balance and fell.
the cost needs to be balanced ______ its benefits.
the garden is overgrown with ______, so i have to ______ it now.
both parents and children should try to______ the generation gap between them.
monkey king ______ his eyes and looked afar.
what is the meaning of the word sharp in the sentence “there is a sharp contrast between the lives of the poorest and the richest members of society”?
what is the meaning of the word sharp in the sentence “there is a sharp turn on the road ahead”?
what is the meaning of the word sharp in the sentence “she is a very sharp dresser”?
______ and simple clothes are appropriate for school wear.
surely you can see what's wrong; it's as plain as the ______ on your face.
every girl in town admires her for her ______ figure.
look at the lovely ______ cheeks of the baby!
works of art and priceless ______ records were ruthlessly destroyed in the war.
their inventions have contributed to the development of ______ engineering.
we bought a all car for ______ reason.
there is nothing in the world ______ teaches us some lessons.
he is nothing ______ a singer.
i'm not going to _______ his signature for you! what do you take me for?
the term ‘cardboard city’ was ______ to describe communities of homeless people living in cardboard boxes.
determined to live ______ someday, he managed to get trained in iron molding.
the reality star and her boy-friend have officially ended their five month romance. she claimed yesterday that they parted ______.
13. the boxer beat his wife _______ at home and was then caged for life.
every morning she ______ her huand’s shirt before he goes to work.
sure, you convinced mom to stop those boring violin lessons! but that makes it easier for her to send us to sunday school. don't you realize we've jumped out of the frying ______ into the fire?
______ is a unit for measuring length which equals to 10 meters.
a _______ is a cycle with three wheels, two at the back and one at the front or sometimes otherwise. a. monocycle b. bicycle c. tricycle d. car
20. ______ is the state or custom of being married to only one person at a particular time.
the two sides of a coin are known as ‘______’ and ‘tail’.
i've always been good at math—i guess i just have a ______ for numbers.
when the boss learned tom had been lying, he fired him _______ the spot.
i have to set numerous alarms for the morning because i sleep like a _______ every night!
kim is staying for dinner, and he eats like a _______, so you’d better make some extra food.
vast sums of money were ______ up in the stock market.
those books were normally kept under______ and key in the library.
it's not a(n) ______ that none of the directors are women.
______ is used as a default form of address for women regardless of marital status.
it is not a good idea to miss meals and ______ them with snacks.
in greek mythology, narcissus fell in love with his own ______ in the lake.
darwin's theories about evolution were ______ by many people who believe in god.
mahatma gandhi, the leader of the indian independence movement, ______ the use of violence.
human beings have ______ noses and ears.
good ________ make good neighbors.
he has hired one of the uk’s top lawyers to ______ him against the allegations.
he should think before he speaks, or else he will ______ others.
our boss is not willing to pay the standard wage for the help in our office. so we have to scrape the bottom of the ______ and end up hiring secretaries who can't type or spell.
a ______ of birds flew towards us slowly from far away.
she does the ______ teaching jobs but nothing permanent.
he's always at ______ with his father over politics.
we have an edge over the other team in height, so i'd say the ______ are in our favor.
the police are keeping the suspects under ______.
the word “babysit” comes from its noun form “babysitter” via ______.
the term “mooc” is a(n) ______ for “massive open online course”.
dad still has a bit of his cold, but ______ all are well.
i have no ______ for jane. it's all her own fault.
mr. smith died of cancer in 1996. his wife ______ him by 10 years and passed away in 2006.
the safety voltage for continuous contact with human body is not higher than () v, and the safety current is not higher than () ma.
the main causes of electric fires include: ()
which of the following shall be used for extinguishing electric fire: ()
what factors shall be considered when selecting instruments? ()
which methods could be used for measuring signal amplitude with a digital oscilloscope? ()
using digital oscilloscope to observe the waveform of dc signal, which coupling method shall be selected for the measurement channel? ()
the signal output of the function signal generator can be short circuited. ()
when using proteus software, it is necessary to check the electrical rules after connecting the circuit. ()
during the "common-emitter amplifier" simulation test, dynamic parameters shall be measured while ensuring the output waveform is not distorted. ()
when testing the voltage tranission characteristics of ttl nand gate (74ls00), the input signal is 500hz (), and () mode shall be selected when observing the oscilloscope waveform. ()
since the minimum voltage is 2.4 v when the 74ttl outputs high level and 3.5 v when the 74hcmos inputs high level, ttl cannot directly drive cmos. ()
the basic component of a combinational logic circuit is: ().
sequential logic circuit has an output signal that depends only on the current input signal and is independent of the state of the circuit. ()
the preset terminal and reset terminal of d flip-flop can be valid at the same time. ()
the phase difference between the input voltage and the output voltage of the common-emitter amplifier is: ().
which of the following feedback can increase the input resistance? ()
which of the following feedback can reduce the output resistance? ()
negative feedback can increase the amplification of the amplifier. ()
555 timer is a ().
the application of 555 timer does not include ().
under the effect of the trigger signal from the monostable flip-flop the circuit turns over from the steady state to the transient stable state where it stays for some time, and then automatically returns to the steady state. ()
when the 74ls90 chip qa is connected to input b and the counting pulse is input from input a, which counting system does the chip employ? ()
in the following serial input-parallel output circuit, the input data d0 to d6 are connected to "1 0 1 0 1 0 1" in sequence. after inputting low level to the reset terminal for reset, the reset terminal is restored to high level. after 7 clock periods, the state of the output terminals q0 to q7 is: ()
which of the following operational amplifier circuit has feedback? ()
which type of filter is generally selected for signal demodulation? ()
what type of filter is shown in the following figure? ()
the rotation direction of an asynchronous motor is related to: ()
the efficiency of the power amplifiers refers to: ()
the amplifier works in class a, class b, class a&b and other modes. the conduction angle of amplifier tube in class b amplifier is: ()