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   4424篇
  免费   337篇
  国内免费   8篇
耳鼻咽喉   46篇
儿科学   161篇
妇产科学   107篇
基础医学   560篇
口腔科学   83篇
临床医学   480篇
内科学   841篇
皮肤病学   58篇
神经病学   489篇
特种医学   81篇
外科学   593篇
综合类   42篇
预防医学   577篇
眼科学   111篇
药学   226篇
中国医学   8篇
肿瘤学   306篇
  2024年   5篇
  2023年   64篇
  2022年   100篇
  2021年   206篇
  2020年   105篇
  2019年   181篇
  2018年   183篇
  2017年   129篇
  2016年   138篇
  2015年   151篇
  2014年   245篇
  2013年   273篇
  2012年   371篇
  2011年   383篇
  2010年   210篇
  2009年   190篇
  2008年   272篇
  2007年   292篇
  2006年   266篇
  2005年   243篇
  2004年   219篇
  2003年   173篇
  2002年   146篇
  2001年   22篇
  2000年   21篇
  1999年   16篇
  1998年   23篇
  1997年   9篇
  1996年   8篇
  1995年   7篇
  1994年   7篇
  1993年   8篇
  1992年   11篇
  1991年   7篇
  1990年   12篇
  1989年   12篇
  1988年   9篇
  1987年   13篇
  1986年   8篇
  1985年   4篇
  1983年   5篇
  1982年   2篇
  1979年   3篇
  1976年   2篇
  1971年   1篇
  1970年   3篇
  1968年   2篇
  1966年   1篇
  1957年   1篇
  1936年   1篇
排序方式: 共有4769条查询结果,搜索用时 62 毫秒
11.
12.
13.
Federal and state codes exist regarding administering and dispensing medications and there is variation between the two. Recognition of the differences is imperative for the athletic trainer, who has traditionally dispensed these agents in compliance with established legal and professional guidelines. Statutes that apply to classifying, documenting, prescribing, dispensing, labeling, and housing medications by athletic trainers are presented as a baseline for this article. State and local regulations should be consulted to clarify differences existing at various governmental levels. These guidelines are provided to assist athletic trainers in properly dispensing medications.  相似文献   
14.
In a study of cytokine production ex vivo by Borrelia burgdorferi-stimulated peripheral blood mononuclear cells from 27 patients with culture-positive erythema migrans, production of inflammatory cytokines predominated, particularly gamma interferon and, to a lesser degree, tumor necrosis factor alpha. In contrast, with the exception of interleukin-13, anti-inflammatory cytokine production was negligible. Thus, B. burgdorferi antigens in early Lyme disease often induce a strong inflammatory response.  相似文献   
15.
BACKGROUND: Genetic influences have been shown to play a major role in determining the risk of attention-deficit hyperactivity disorder (ADHD). In addition, prenatal exposure to nicotine and/or alcohol has also been suggested to increase risk of the disorder. Little attention, however, has been directed to investigating the roles of genetic transmission and prenatal exposure simultaneously. METHOD: Diagnostic telephone interview data from parents of Missouri adolescent female twin pairs born during 1975-1985 were analyzed. Logistic regression models were fitted to interview data from a total of 1936 twin pairs (1091 MZ and 845 DZ pairs) to determine the relative contributions of parental smoking and drinking behavior (both during and outside of pregnancy) as risk factors for DSM-IV ADHD. Structural equation models were fitted to determine the extent of residual genetic and environmental influences on ADHD risk while controlling for effects of prenatal and parental predictors on risk. RESULTS: ADHD was more likely to be diagnosed in girls whose mothers or fathers were alcohol dependent, whose mothers reported heavy alcohol use during pregnancy, and in those with low birth weight. Controlling for other risk factors, risk was not significantly increased in those whose mothers smoked during pregnancy. After allowing for effects of prenatal and childhood predictors, 86% of the residual variance in ADHD risk was attributable to genetic effects and 14% to non-shared environmental influences. CONCLUSIONS: Prenatal and parental risk factors may not be important mediators of influences on risk with much of the association between these variables and ADHD appearing to be indirect.  相似文献   
16.
Adult Long-Evans rats, exposed prenatally to 1 of 4 doses of cocaine (0.0,0.5,1.0, or 3.0 mg/kg iv), were tested on a 3-choice visual attention task with an olfactory distractor presented unpredictably on one third of the trials. The performance of all 3 cocaine-exposed groups was significantly more disrupted than that of controls by the presentation of distractors. Results demonstrate that prenatal cocaine exposure increases susceptibility to distractors, using a task specifically designed to measure this function. In addition, the present study revealed that individuals exposed to cocaine in utero exhibit greater performance disruption after an error than controls, in certain types of tasks. Both areas of dysfunction, impaired selective attention and impaired arousal regulation, have important functional consequences in humans, possibly affecting the school performance and social development of cocaine-exposed children.  相似文献   
17.
The CD45 antigen is a haemopoietic cell specific tyrosine phosphatase essential for antigen receptor mediated signalling in lymphocytes. Expression of different patterns of alternatively spliced CD45 isoforms is associated with distinct functions. We recently identified a polymorphism in exon 6 (A138G) of the gene encoding CD45 (PTPRC) that results in altered CD45 splicing. The 138G allele is present at a high frequency among Japanese (23.7%), with 5.1% individuals homozygous for the G allele. In this study we show that the A138G polymorphism is the cause of altered CD45 isoform expression, promoting splicing towards low molecular weight CD45 isoforms. We further report that the frequency of A138G heterozygotes is significantly reduced in number in cohorts of patients with autoimmune Graves' disease or hepatitis B infection, whereas G138G homozygotes are absent from a cohort of Hashimoto's thyroiditis patients. We also show that 138G individuals exhibit altered cytokine production in vitro and an increased proportion of memory T cells. These data suggest that the 138G variant allele strongly influences these diseases by modulation of immune mechanisms and may have achieved its high frequency as a result of a natural selection probably related to pathogen resistance.  相似文献   
18.
Streptococcus pyogenes protein H (sph) is an immunoglobulin-binding protein present in the Mga regulon of certain M1 serotype isolates. Although sph is present in many strains, it is frequently not expressed. In this paper we show that protein H was highly expressed after bacteria were injected into the skin of mice and were recovered from the blood, kidney, or spleen at various times postinfection. The percentage of protein H-positive colonies increased with time, reaching 100% in the spleen and kidney within 24 to 72 h postinfection. The up-regulation of sph expression was also observed in a mga mutant.  相似文献   
19.
Six multipurpose contact lens solutions [All-in-One, All-in-One (Light), ReNu MultiPlus, Optifree Express, Complete, and Solo-care soft] were tested for their efficacies against Acanthamoeba castellanii trophozoites and cysts by using a most probable number (MPN) technique for amoebic enumeration. Against trophozoites, All-in-One, ReNu Multiplus, and Optifree Express achieved total kill (log reduction of >3) after the manufacturer's minimum recommended disinfection time (MMRDT), with the remaining solutions failing to reach a log reduction of 1. After 24 h of exposure, all solutions proved trophozoiticidal, achieving, with the exception of Complete (log reduction of 3.13), total kill. Against cysts, All-in-One gave a log reduction of >3 within the MMRDT, with all other solutions failing to achieve a log reduction of 1. After 24 h of exposure, All-in-One achieved total kill of cysts (log reduction of 3.74), ReNu MultiPlus gave a log reduction of 3.15, and the remaining solutions reached log reductions of between 1.09 and 2.27. The MPN technique provides a simple, reliable, and reproducible method of amoebic enumeration that depends on simply establishing the presence or absence of growth on culture plates inoculated with a series of dilutions and determining the MPN of amoebae present from statistical tables. By use of this technique, two of the multipurpose solutions tested, ReNu MultiPlus and Optifree Express, demonstrated effective trophozoiticidal activities within the recommended disinfection times; however, only All-in-One proved effective against both trophozoites and cysts over the same time period. This MPN technique, which uses axenically produced trophozoites and mature, double-walled cysts, has the potential to form the basis of a national standard for amoebicidal efficacy testing of multipurpose contact lens disinfecting solutions.  相似文献   
20.
Saccharomyces cerevisiae ATS1 (-tubulin suppressor 1) was originally identified as a high-copy suppressor of class two -tubulin mutations and was proposed to have a regulatory role in coordinating the microtubule state with the cell cycle. Here, we show that Ats1p interacts with Nap1p, a cytoplasmic protein that regulates the activity of the Cdc28p/Clb2p complex. Loss of Nap1p results in a delayed switch from polar to isotropic bud growth. The delayed switch results in elongated buds. Nap1p and Ats1p interact in two-hybrid and co-immunoprecipitation assays. Both nap1 and ats1 cells have a Clb2p-dependent elongated bud morphology. Deletion of ATS1 partially suppresses the elongated bud morphology and benomyl resistance of nap1 mutants. Our results suggest Ats1p might regulate coordination of the microtubule state with the cell cycle through an interaction with Nap1p.Communicated by S. Hohmann  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