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   24621篇
  免费   2114篇
  国内免费   595篇
耳鼻咽喉   66篇
儿科学   558篇
妇产科学   429篇
基础医学   2755篇
口腔科学   349篇
临床医学   2630篇
内科学   3507篇
皮肤病学   243篇
神经病学   691篇
特种医学   383篇
外国民族医学   2篇
外科学   1500篇
综合类   3300篇
现状与发展   4篇
一般理论   1篇
预防医学   4572篇
眼科学   184篇
药学   3529篇
  17篇
中国医学   1317篇
肿瘤学   1293篇
  2024年   53篇
  2023年   325篇
  2022年   739篇
  2021年   1005篇
  2020年   816篇
  2019年   832篇
  2018年   766篇
  2017年   845篇
  2016年   882篇
  2015年   980篇
  2014年   1520篇
  2013年   1804篇
  2012年   1378篇
  2011年   1570篇
  2010年   1210篇
  2009年   1029篇
  2008年   1024篇
  2007年   1035篇
  2006年   996篇
  2005年   808篇
  2004年   724篇
  2003年   672篇
  2002年   556篇
  2001年   442篇
  2000年   395篇
  1999年   275篇
  1998年   302篇
  1997年   301篇
  1996年   266篇
  1995年   255篇
  1994年   269篇
  1993年   235篇
  1992年   224篇
  1991年   192篇
  1990年   170篇
  1989年   172篇
  1988年   146篇
  1987年   159篇
  1986年   119篇
  1985年   353篇
  1984年   270篇
  1983年   235篇
  1982年   206篇
  1981年   183篇
  1980年   137篇
  1979年   91篇
  1978年   84篇
  1977年   67篇
  1976年   48篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Interaction of immunoglobulin with actin   总被引:8,自引:0,他引:8  
Actin can form specific, direct associations with immunoglobulin resulting in soluble complexes or cross-linked matrices. This interaction can be detected by four in vitro assays using purified components: (1) actin enhances the cytophilic activity of guinea pig IgG2; (2) in solutions of low ionic strength, actin and IgG2 co-precipitate: (3) soluble complexes exist in 0.1 M KCl as revealed by the displacement of actin from its expected sedimentation pattern in a gradient of sucrose when in the presence of IgG 1, IgG2, or IgM; (4) immunoglobulin (IgG1, IgG2, BGG)‡: increases the viscosity of F-actin solutions, presumably by crosslinking F-actin filaments. These data suggest that direct interaction of a cytoskeletal protein with a cell surface receptor is possible.  相似文献   
72.
Receptors for IgM were detected on peripheral blood human eosinophils by a rosette technique with ox red blood cells coated with the IgM fraction of the specific immunserum. Between 14 % and 43 % (mean 27 %) FcµR positive cells were found after an overnight incubation period at 37°C by using this technique. The specificity of the receptors for IgM was assessed by studying the inhibitory capacity of purified human IgM in the rosette assay. From an ultrastructural point of view, the EAM rosette-forming cells are mature eosinophlic granulocytes characterized by a nucleus with a variable number of lobes and a certain number of «first type» granules partially or totally devoid of their content.  相似文献   
73.
74.
The immunosuppressive effect of kidney graft recipient sera was studied on T-lymphocyte alloreactive line (4H) proliferation and compared to native cyclosporin A (CyA) and CyA metabolite concentrations determined by radioimmunoassay (RIA) using specific or nonspecific monoclonal antibodies. Three clinical groups were studied: (1) patients experiencing acute renal rejection episodes (CyA-R), (2) patients experiencing CyA-dependent nephrotoxicity episodes (CyA-TOX) and (3) patients in a clinically steady state (CyA-ST), according to their therapeutic regimen i.e., monotherapy (CyA alone) or polytherapy (CyA associated with prednisolone and/or azathioprine). Regardless of the clinical state, sera of patients in polytherapy displayed more inhibitory activity than those of monotherapy patients (24% and 40% inhibition of 4H proliferation, respectively, at sera dilution of 1:2), something which was no doubt due to the inhibitory activity of prednisolone on T-lymphocyte growth. In the two therapeutic regimens, CyA-ST patient sera exhibited the lowest inhibitory activity on the 4H line (45% and 65% inhibition of 4H proliferation in mono-and polytherapy, respectively, at sera dilution of 1:2). Sera from CyA-TOX patients were highly inhibitory (74% and 86% inhibition of 4H proliferation in mono-and polytherapy, respectively, at sera dilution of 1:2), in agreement with RIA assays showing increased native circulating CyA and CyA metabolites and daily CyA intake in this group as compared to CyA-St. Surprisingly, CyA-R patient sera were no less inhibitory than those of CyA-ST patients on 4H-line, antigen-induced proliferation. This clinical group did not differ from others for CyA intake or level of circulating immunosuppressive molecules, suggesting that rejection could be associated with a state of interindividual variation in sensitivity to CyA. In addition, a polytherapeutic regimen seemed to modify CyA bioavailability in CyA-ST group patients, with a decreased CyA metabolite level as compared to their monotherapy counterparts (native CyA plus metabolite/native CyA ratio being 2.73 and 3.73, respectively). In contrast, in the CyA-R patient group, polytherapy appeared to be associated with an increase in CyA metabolite circulating levels (ratio 4.79). In view of the low inhibitory activity of CyA metabolites, this profile might lead to rejection.  相似文献   
75.
Summary The need for further information on drug utilization patterns during pregnancy in different countries was assessed by reviewing literature obtained by hand and computer searches for the years 1960–1988.The 13 identified studies showed that pregnant women used an average of 4.7 drugs. The most commonly ingested medications were vitamins and iron preparations (almost all women), analgesics, antiemetics and antacids.However, the important variables taken into account differently in each study, such as date of surveillance, country, size of population, personal habits, and physiopathological and demographic characteristics, may it impossible to construct a comprehensive, detailed, up-to-date picture of drug utilization during pregnancy.The evaluation confirmed the need for systematic permanent surveillance of drug utilization in pregnancy, so as to avoid the use of data based on widely differing contexts, times and methods, in a field where knowledge is often derived from scanty information.This study was supported in part by the National Research Council (CNR, Rome, Italy), Convenzione Farmacologia Clinica  相似文献   
76.
目的:探讨大鼠中脑导水管周围灰质(PAG)内内源性强啡肽对神经降压素(NT)镇痛作用的影响。方法:以钾离子透入法引起大鼠甩尾反应的电流强度(mA)为痛行为反应的指标,观察向PAG内注入NT,抗神经降压素血清和抗强啡肽A1-13血清对动物痛阈的影响。结果:PAG内注入NT后,大鼠痛阈明显升高;注入抗神经降压素血清后,大鼠痛阈则明显降低,而注入抗强啡肽血清后,对NT的镇痛效应无显著影响,结论:PAG内NT在痛觉调制中发挥着重要的作用,且其作用不依赖于PAG内的内源性强啡肽。  相似文献   
77.
78.
慢性特发性荨麻疹患者血清组胺释放活性的检测   总被引:7,自引:0,他引:7  
目的 检测慢性特发性荨麻疹患者血中组胺释放活性。方法 自身血清皮肤试验和嗜好性粒细胞组胺释放试验。结果 自身血清皮肤试验和嗜碱性组胺释放试验的阳性率分别为37.5%和43.75%。结论部分慢性特发性荨麻疹患者血中组胺释放活性增高,揭示该类病人具有特殊的肥大细胞和嗜碱性粒细胞激活机制,很可能与自身免疫有关。  相似文献   
79.
We have investigated the T cell receptor (TCR) repertoire in the inflammatory infiltrates of T line-transferred experimental autoimmune encephalomyelitis (EAE) of the Lewis rats. Using a panel of TCR V-specific monoclonal antibodies (mAbs) and immunocytochemistry, we studied the nature of the T cells entering the central nervous system (CNS) after transfer of either myelin basic protein (MBP)-reactive, or MBP-reactive but non-encephalitogenic T cell lines. All the MBP-specific T cell lines predominantely used the V8.2 TCR chain. T cell lines specific for the tuberculin purified protein derivative (PPD), using TCR V genes different from V8.2, served as controls. We first studied the time course of T cells entering the CNS. In all recipient rats, small, but significant numbers of -TCR-expressing infiltrate cells appeared in the CNS within the first 24 h after T cell transfer. In animals injected with either type of MBP-reactive T cells, the early infiltrate cells were preferentially located within the parenchyma of the spinal cord, while in PPD T lineinjected rats, the lymphocytes were mostly found in the meninges. TCR V gene usage was examined on the peak of clinical disease. Six days after T cell transfer, the TCR repertoire used by infiltrating lymphocytes in general seemed to be highly diverse. None of the V isotypes examined (i.e. V8.2, V8.5 or V10) was used by a major population of the -TCR-positive T cells. A more detailed, quantitative analysis of individual infiltrate compartments revealed, however, a preferential accumulation of V8.2-positive T cells within the parenchyma. In contrast, perivascular infiltrating cells used V genes randomly. Our results confirm first that activated T lymphocytes enter the brain rapidly irrespective of their antigen specificity. Second, the data show that most of the perivascular infiltrate T cells in the acute EAE lesion are host-derived, recruited presumably from the recirculating T cell pool, while the encephalitogenic, V8.2-positive T cells preferentially persist within the parenchyma.Abbreviations EAE experimental autoimmune encephalomyelitis - MBP myelin basic protein - TCL T cell line Supported by the Brazilian Research Council (CNPq)  相似文献   
80.
本文作者对汕头卫生检疫局1993年从19129名入出境人员疾病监测体检中发现的1809名HBsAg阳性者进行HBV标志物(抗-HBs、HBeAg、抗-HBe、抗-HBc)测定结果的分析,提出今后继续加强开展乙型肝炎“二对半”检测,做好乙型肝炎预防工作的意见。  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