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   51112篇
  免费   3138篇
  国内免费   266篇
耳鼻咽喉   475篇
儿科学   1425篇
妇产科学   1410篇
基础医学   6656篇
口腔科学   1110篇
临床医学   5248篇
内科学   11075篇
皮肤病学   1005篇
神经病学   5394篇
特种医学   1811篇
外科学   6694篇
综合类   306篇
一般理论   24篇
预防医学   3810篇
眼科学   906篇
药学   3187篇
  1篇
中国医学   96篇
肿瘤学   3883篇
  2024年   73篇
  2023年   535篇
  2022年   1034篇
  2021年   1869篇
  2020年   1123篇
  2019年   1589篇
  2018年   1816篇
  2017年   1289篇
  2016年   1437篇
  2015年   1628篇
  2014年   2264篇
  2013年   2844篇
  2012年   4179篇
  2011年   4233篇
  2010年   2143篇
  2009年   1979篇
  2008年   3388篇
  2007年   3265篇
  2006年   3000篇
  2005年   2971篇
  2004年   2498篇
  2003年   2228篇
  2002年   2008篇
  2001年   442篇
  2000年   384篇
  1999年   398篇
  1998年   347篇
  1997年   271篇
  1996年   263篇
  1995年   229篇
  1994年   196篇
  1993年   140篇
  1992年   196篇
  1991年   213篇
  1990年   197篇
  1989年   160篇
  1988年   141篇
  1987年   148篇
  1986年   153篇
  1985年   137篇
  1984年   122篇
  1983年   93篇
  1982年   88篇
  1981年   60篇
  1980年   60篇
  1979年   67篇
  1978年   57篇
  1977年   55篇
  1974年   48篇
  1972年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Background Optic disc anomalies are frequently associated with Alagille syndrome. We report here the first case of a patient with Alagille syndrome combined with optic pit and serous macular detachment. Methods A male patient with Alagille syndrome was referred from the pediatric hepatology department for investigation of visual loss in the right eye. Anterior segment examination showed evidence of posterior embryotoxon, confirmed by gonioscopic evaluation. Dilated fundus examination revealed serous macular detachment and optic pit. Results OCT 3 scans confirmed the clinical findings. Conclusions Optic pit is uncommon and should prompt a search for genetic disorders or development abnormalities. The association between the two syndromes in this patient might be due to failure of correct neuroectodermal development, for which a common genetic pathway is likely.  相似文献   
82.
Twenty patients with AIDS who had intracranial lesions underwent both brain biopsy and cerebro-spinal fluid (CSF) examination to compare histological diagnosis with the polymerase chain reaction (CSF-PCR) for the identification of infectious agents. CSF-PCR was performed for herpes simplex virus, varicella zoster virus, cytomegalovirus (CMV), JC virus (JCV), Epstein-Barr virus (EBV), Toxoplasma gondii and Mycobacterium tuberculosis. A definitive diagnosis was obtained by brain biopsy in 14 patients (2 with astrocytoma, 12 with brain infection). CSF-PCR was positive for EBV DNA in 3 of 3 cases of primary cerebral lymphoma, positive for JCV DNA in 6 of 7 biopsy-proven (and one autopsy-proven) cases of progressive multifocal leukoencephalopathy (PML). CSF-PCR was positive for CMV DNA in one biopsy-proven and one autopsy-proven case of CMV encephalitis (the former also had PML) and positive for M. tuberculosis DNA in one case of tuberculous encephalitis. None of the five toxoplasmic encephalitis cases (one definite, four presumptive) were T. gondii DNA positive. There was close correlation between histology and CSF-PCR for CMV encephalitis, PML and PCL. Antitoxoplasma therapy affected the sensitivity of both histological and CSF-PCR methods. Received: 8 November 1995 Received in revised form: 9 July 1996 Accepted: 19 July 1996  相似文献   
83.
Diabetic rats display changes in opioid pharmacology and brain regional levels of opioid peptides and prodynorphin mRNA. Previous investigations of opioid receptor binding, carried out in whole-brain homogenates, have, however, failed to detect changes. In the present study, quantitative autoradiography was used to measure μ and κ opioid receptor binding in discrete brain regions of streptozotocin-treated diabetic rats. Measurement was limited to regions that previously displayed opioid binding changes in chronically food-restricted rats, since our primary aim is to identify brain mechanisms that mediate adaptive responses to persistent metabolic need and adipose depletion. Diabetics displayed strong trends or statistically significant changes which matched seven of the thirteen binding changes observed in food-restricted rats. In no case did diabetics display changes in the opposite direction. The two statistically significant changes common to food-restricted and diabetic rats are increased κ binding in the medial preoptic area and decreased μ binding in the lateral habenula. The possible functional significance of these changes is discussed.  相似文献   
84.
The spatial and temporal pattern of expression of the protein products of immediate early genes (IEGs) c-fos, fos B, and egr-1 were mapped in medial preoptic area (MPOA) and ventral bed nucleus of stria terminalis (VBST) during maternal behavior in rats. Immunocytochemical analysis indicated significant increases in the number of cells expressing c-Fos after 2 h of pup exposure, while Fos B levels showed a delayed response, reaching maximal levels after 6 h.  相似文献   
85.
86.
87.
In the course of a phase I trial, in which recombinant IL-2 (rIL-2) was infused intraperitoneally (i.p.) in patients with peritoneal carcinomatosis, we evaluated the effect on "tumor-associated lymphocytes" (TAL) isolated from the ascitic fluid. No major changes in the percentages of cells expressing the CD3, CD4, CD8, Leu-7, OKM1 and WT-31 antigens were detected either in TAL or in peripheral blood lymphocytes (PBL) after 7 days of rIL-2 infusion. In contrast the percentages of TAL (but not PBL) expressing surface IL-2 receptor (Tac), or LAK-1 antigen were sharply increased. Analysis of cytolytic functions showed a potentiation of the lytic activity against natural-killer (NK) sensitive K562 target cells and the de novo appearance of lytic activity against fresh melanoma cells. In one patient IFN-gamma was detected in the ascitic fluid following rIL-2 infusion. T-cell clones derived from the patient were analyzed for the IFN-gamma production. While only approximately 40% of PB-derived control clones produced medium to low amounts of IFN-gamma, all of the TAL-derived clones produced medium to high amounts of the lymphokine.  相似文献   
88.
Sex-based differences in CD4 T-cell (CD4) counts are well recognized, but the basis for these differences has not been identified. Conceivably, homeostatic factors may play a role in this process by regulating T-cell maintenance and repletion. Interleukin (IL)-7 is essential for normal T-cell production and homeostasis. We hypothesized that differences in IL-7 might contribute to sex-based differences in CD4 counts. Circulating IL-7 levels were analyzed in 299 HIV-1-infected women and men. Regression analysis estimated that IL-7 levels were 40% higher in women than in men (P = 0.0032) after controlling for CD4 count, age, and race. Given the important role of IL-7 in T-cell development and homeostasis, these findings suggest that higher IL-7 levels may contribute to higher CD4 counts in women.  相似文献   
89.
90.
Information production and its communication being a key public health activity, developing modern information systems is a precondition for its fulfilling these assignments. A national public health information system (NPHIS) is a set of human resources combined with computing and communication technologies. It enables data linkage and data coverage as well as undertaking information production and dissemination in an effective, standardized and safe way. The Croatian Institute of Public Health LAN/WAN modules are under development. Health Safety System, Health Workers Registry, and Digital Library are among the Institute's developmental priorities. Communication between NPHIS participants would unfold over the Internet by using every relevant data protection method. Web technology-based applications would be run on special servers. Between individual applications, use would be made of the transaction module of communication through an exchange of the HL7 standard-based xml messages. In the conditions of transition, the health system must make an optimal use of the resources, which is not feasible without applying modern information and communication technologies.  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