首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5977篇
  免费   694篇
  国内免费   7篇
耳鼻咽喉   37篇
儿科学   141篇
妇产科学   223篇
基础医学   950篇
口腔科学   135篇
临床医学   738篇
内科学   1055篇
皮肤病学   70篇
神经病学   521篇
特种医学   284篇
外科学   628篇
综合类   177篇
一般理论   2篇
预防医学   712篇
眼科学   168篇
药学   400篇
中国医学   149篇
肿瘤学   288篇
  2021年   96篇
  2020年   55篇
  2019年   71篇
  2018年   95篇
  2017年   70篇
  2016年   72篇
  2015年   76篇
  2014年   111篇
  2013年   182篇
  2012年   239篇
  2011年   260篇
  2010年   147篇
  2009年   136篇
  2008年   196篇
  2007年   247篇
  2006年   265篇
  2005年   267篇
  2004年   224篇
  2003年   234篇
  2002年   223篇
  2001年   240篇
  2000年   224篇
  1999年   242篇
  1998年   106篇
  1997年   95篇
  1996年   88篇
  1995年   108篇
  1994年   74篇
  1993年   91篇
  1992年   168篇
  1991年   153篇
  1990年   144篇
  1989年   154篇
  1988年   141篇
  1987年   138篇
  1986年   113篇
  1985年   117篇
  1984年   89篇
  1983年   70篇
  1982年   47篇
  1981年   55篇
  1980年   63篇
  1979年   58篇
  1978年   69篇
  1977年   50篇
  1976年   46篇
  1973年   32篇
  1972年   52篇
  1971年   43篇
  1970年   40篇
排序方式: 共有6678条查询结果,搜索用时 212 毫秒
61.
Abstract During 1988, more than 40 state health departments conducted telephone surveys to obtain state-specific population estimates of the prevalence of adult health behaviors and health practices. However, the comparability of estimates obtained from these telephone surveys with more expensive in-person surveys has not been assessed in an applied setting. This study compared the prevalence estimates of smoking and binge drinking obtained from a telephone survey (N = 1,492) with an in-person survey (N = 2,802) which were conducted by the state of Michigan during 1982-1983. Although the standard errors for the differences in the estimates for the two surveys were relatively large, the actual differences were consistently small within most age-, sex-, and education-specific groups. Despite certain limitations, telephone surveys provide a reasonable alternative to in-person surveys for estimating the prevalence of health behaviors. The data obtained from these surveys are being used to set state health objectives, to plan state-wide health promotion programs, and to support public health legislation.  相似文献   
62.
The parents of all children attending the Royal Brompton National Heart and Lung Hospital cystic fibrosis paediatric clinic were asked to complete an anonymous postal questionnaire addressing attitudes towards prenatal diagnosis and population carrier screening for cystic fibrosis (CF); 65% (170/261) of parents responded. Of the respondents, 92% would support the introduction of a population screening test to detect carriers of CF and 19% felt such a test should be mandatory. A total of 64% of CF parents felt they would choose not to have any further children in the knowledge that they were both carriers, 74% would choose to have a prenatal test if they became pregnant, 44% would consider terminating an affected pregnancy, 33% would not, and 23% were unsure. Overall, 72% of respondents indicated they would choose to avoid having a further child with CF either by not having further children or by terminating an affected pregnancy.  相似文献   
63.
In preparation for assessment of percutaneous biopsies in our clinical pancreas transplant program, a working knowledge of the histopathologic changes after transplantation was obtained in a longitudinal open biopsy study of 16 dogs receiving bladder-drained whole pancreas allografts. Edema, extravasation of polymorphs, and lymphocytes associated with focal parenchymal injury were early, invariable, and probably nonspecific findings. The initial feature of unmodified rejection was the appearance of capillary and small vein endothelial changes with mainly perivascular inflammatory cell infiltration. Acinar cell loss occurred early and was progressive, whereas islets and ducts were relatively preserved, indicating that acinar tissue may be more vulnerable to lytic necrosis when damaged. Functional rejection, determined by fasting urinary amylase levels, was at a stage of extensive and irreversible necrosis. Functioning grafts in immunosuppressed dogs had minor and transient endothelial changes with absence of class II antigen staining of parenchymal cells.  相似文献   
64.
65.
66.
Two DNA restriction fragment length polymorphisms show genetic linkage to the Duchenne muscular dystrophy locus on the short arm of the X chromosome. Examples are given of families in which these polymorphisms can be used in the prediction of genotype for this disorder.  相似文献   
67.
The effects of dopamine on spontaneous excitatory postsynaptic currents (sEPSCs) and inhibitory postsynaptic currents (sIPSCs) in three different classes of neurones within the optic lobe of cuttlefish were investigated using whole-cell voltage clamp techniques in a slice preparation. The neuronal types were centrifugal and amacrine neurones, located in the inner granular cell layer, and medullar interneurones, located within the central medulla of the optic lobes. The results demonstrate that bath application of dopamine (50 microM) reversibly reduced both the frequency and amplitude of sEPSCs and of sIPSCs in these optic lobe neurones. The inhibitory effects of DA were dose-dependent and neither D1- nor D2-like receptors appear to be implicated, but probably D4-like receptors are involved in these actions. By pre-applying tetrodotoxin (TTX, 0.5 microM), to block action potential-dependent EPSCs and IPSCs, it is shown that dopamine has no effect on the amplitude, frequency or decay time constant of the mEPSCs or mIPSCs. The results are the first to identify a specific physiological action of dopamine on cephalopod brain activity, they indicate that this effect is probably presynaptic to the specific classes of cells recorded from, and they provide information on the pharmacological profile of the receptors involved. The widespread inhibitory effect of dopamine on the activity of cuttlefish optic lobe neurones is discussed in the context of comparable data from vertebrate preparations and the actions of other neuromodulators in the cuttlefish brain.  相似文献   
68.
Centromeres remain the least characterized regions of human chromosomes because they have a very high content of repetitive DNA. Here, we describe a micro-dissection library from the centromeric region of human chromosome 7 and its use for generating sequence tagged sites (STSs). The library contains about 1500 clones with an average insert size of 150 bp and only about 15% of the clones harbour repetitive human DNA. Seven clones hybridizing to alphoid DNA were found to correspond to a fragment of the D7Z2 alphoid array on chromosome 7, thus confirming the origin of the library. A number of clones not containing known repetitive DNA were used to generate STSs that identified yeast artificial chromosomes (YACs) and in turn allowed the STSs to be placed on the physical map. One STS is located between the two Genethon genetic markers closest to the centromere on the q side. Another STS was located 3–4 cM away in 7q11.2, while a third identified YACs containing both low-copy and alphoid sequences that are not yet mapped but are clearly centromeric. The library therefore comprises a collection of sequences from the centromeric region of chromosome 7 that can be used to generate STSs and to map the entire centromeric region.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   
69.
Schizophrenic subjects performed significantly worse on neuropsychological tests of frontal lobe function but not on tests of non-frontal lobe function when compared to a matched group of normal subjects. Correlations expected between frontal lobe neuropsychological test performance and negative symptoms were not found.  相似文献   
70.

Background  

Recruiting and retaining GPs for research can prove difficult, and may result in sub-optimal patient participation where GPs are required to recruit patients. Low participation rates may affect the validity of research.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号