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   1516035篇
  免费   117830篇
  国内免费   3601篇
耳鼻咽喉   19918篇
儿科学   49660篇
妇产科学   43495篇
基础医学   214933篇
口腔科学   41421篇
临床医学   132589篇
内科学   310095篇
皮肤病学   36742篇
神经病学   125114篇
特种医学   56185篇
外国民族医学   464篇
外科学   223395篇
综合类   33330篇
现状与发展   3篇
一般理论   521篇
预防医学   120530篇
眼科学   33830篇
药学   105835篇
  1篇
中国医学   3853篇
肿瘤学   85552篇
  2021年   13225篇
  2019年   14259篇
  2018年   20800篇
  2017年   15125篇
  2016年   16488篇
  2015年   18503篇
  2014年   25488篇
  2013年   37837篇
  2012年   53155篇
  2011年   56188篇
  2010年   32381篇
  2009年   30047篇
  2008年   50897篇
  2007年   53855篇
  2006年   53777篇
  2005年   52168篇
  2004年   49363篇
  2003年   46932篇
  2002年   45163篇
  2001年   75499篇
  2000年   77478篇
  1999年   63769篇
  1998年   17408篇
  1997年   15690篇
  1996年   15834篇
  1995年   14991篇
  1994年   13558篇
  1993年   12723篇
  1992年   46691篇
  1991年   44203篇
  1990年   42199篇
  1989年   40117篇
  1988年   36648篇
  1987年   35822篇
  1986年   33354篇
  1985年   31684篇
  1984年   24128篇
  1983年   20261篇
  1982年   12325篇
  1981年   10886篇
  1979年   20984篇
  1978年   14754篇
  1977年   12255篇
  1976年   11533篇
  1975年   11848篇
  1974年   14253篇
  1973年   13836篇
  1972年   12884篇
  1971年   11747篇
  1970年   11171篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
971.
972.
973.
We developed a homogeneous fluoroimmunoassay for detecting amphetamines in urine. Only fluorescence intensity need be measured because the emission of non-protein-bound fluorescein-labeled amphetamine is preferentially quenched by detergent micelles. In a previous reported prototype assay system for measuring gentamicin in serum we used fluorescein and dodecyl sulfate (Anal Chem 1985; 57:1928-30). We have found that favorable hydrophobic and (or) ionic character of the analyte and unfavorable polar and (or) ionic character of the fluor are important determinants of the desired interactions. An anionic detergent and fluorescein, therefore, should be appropriate for apolar of cationic analytes, such as gentamicin and amphetamines. A greater [H+] at the anionic micelle surface is important for quenching emission from the fluor moiety. Millimolar concentrations of dodecyl sulfate rapidly denature immunoglobulin unless hapten is bound with sufficiently high affinity. Affinity was sufficiently high for the antibody used in the prototype gentamicin assay but not for the amphetamine antibody. Thus for the amphetamine assay, we used a non-denaturing detergent, dodecyl(oxyethylene)12 sulfate. The assay requires 30 microL of specimen in 2 mL of total assay volume. Amphetamine(d-,dl-, and meth-), at a concentration of 1 mg per liter of urine, is readily detected.  相似文献   
974.
This analysis applies methods of screening to the problem of psychosis. A probability sample of 810 individuals from the Eastern Baltimore Mental Health Survey was interviewed in the self-report modality with the Diagnostic Interview Schedule and shortly thereafter by a psychiatrist. It is shown that a configuration of responses in the self-report modality can screen moderately well for psychosis, as measured by psychiatrists in the clinical modality.  相似文献   
975.
976.
A technique for arthrodesis of small joints of the hand is described that uses a tenon to secure apposition that has good intrinsic stability as well as a large surface area of cancellous bony contact. A minimum of postoperative immobilization is required. The tenon arthrodesis method has been employed in 85 joints. The literature shows pseudoarthrosis rates of 0 to 33%. This technique had a 2.3% failure rate that compares favorably with those in other published series.  相似文献   
977.
C Krausen  K F Hamann 《HNO》1987,35(7):270-273
Postural changes of body equilibrium on a moving force plate were examined for sinusoidal movements, saccades and frequency whilst different stimuli were applied under various visual conditions. If a dynamic stimulus was used, the stabilization of vision shows a distinct visual-vestibular conflict which provokes postural disequilibrium. This is the cause of motion sickness during car driving. This disequilibrium is also the cause of the motor insecurity experienced during walking and reading at the same time.  相似文献   
978.
Fetal beta-endorphin release has been associated with fetal hypoxia. The purpose of this study was to assess the degree of uterine blood flow reduction needed to elicit fetal beta-endorphin release in the sheep since there is a large reserve of oxygen supply to the fetus. Uterine blood flow was reduced by 26 +/- 2, 46 +/- 3 and 66 +/- 2%, producing fetal oxygen content concentrations of 5.7 +/- 0.6, 4.4 +/- 0.7 and 2.6 +/- 0.3 ml/dl, respectively. Although fetal oxygen concentrations were significantly decreased in the groups with a reduction in uterine blood flow of 46 and 66%, beta-endorphin was elevated only in the latter group. It is speculated that fetal beta-endorphin is released at a level of hypoxia which leads to a decrease in fetal oxygen consumption. A reduction in uterine blood flow of 66% appears to produce a stressful environment for the fetus as measured by fetal plasma beta-endorphin levels.  相似文献   
979.
PURPOSE: Current treatment for febrile neutropenia (FN) includes hospitalization for evaluation, empiric broad-spectrum antibiotics, and other supportive care. Clinical trials have reported conflicting results when studying whether the colony-stimulating factors (CSFs) improve outcomes in patients with FN. This Cochrane Collaboration review was undertaken to further evaluate the safety and efficacy of the CSFs in patients with FN. METHODS: An exhaustive literature search was undertaken including major electronic databases (CANCERLIT, EMBASE, LILACS, MEDLINE, SCI, and the Cochrane Controlled Trials Register). All randomized controlled trials that compare CSFs plus antibiotics versus antibiotics alone for the treatment of established FN in adults and children were sought. A meta-analysis of the selected studies was performed. RESULTS: More than 8,000 references were screened, with 13 studies meeting eligibility criteria for inclusion. The overall mortality was not influenced significantly by the use of CSF (odds ratio [OR] = 0.68; 95% CI, 0.43 to 1.08; P = .1). A marginally significant result was obtained for the use of CSF in reducing infection-related mortality (OR = 0.51; 95% CI, 0.26 to 1.00; P = .05). Patients treated with CSFs had a shorter length of hospitalization (hazard ratio [HR] = 0.63; 95% CI, 0.49 to 0.82; P = .0006) and a shorter time to neutrophil recovery (HR = 0.32; 95% CI, 0.23 to 0.46; P < .00001). CONCLUSION: The use of the CSFs in patients with established FN caused by cancer chemotherapy reduces the amount of time spent in hospital and the neutrophil recovery period. The possible influence of the CSFs on infection-related mortality requires further investigation.  相似文献   
980.
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