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   368462篇
  免费   33662篇
  国内免费   13578篇
耳鼻咽喉   2642篇
儿科学   6836篇
妇产科学   4556篇
基础医学   63807篇
口腔科学   6522篇
临床医学   26105篇
内科学   61637篇
皮肤病学   5481篇
神经病学   28883篇
特种医学   7682篇
外国民族医学   101篇
外科学   25735篇
综合类   50783篇
现状与发展   50篇
一般理论   11篇
预防医学   20290篇
眼科学   3976篇
药学   51121篇
  72篇
中国医学   14232篇
肿瘤学   35180篇
  2024年   642篇
  2023年   5862篇
  2022年   8414篇
  2021年   17030篇
  2020年   13571篇
  2019年   13253篇
  2018年   12686篇
  2017年   12745篇
  2016年   12816篇
  2015年   15094篇
  2014年   22510篇
  2013年   25074篇
  2012年   22632篇
  2011年   26250篇
  2010年   22110篇
  2009年   21716篇
  2008年   20843篇
  2007年   18794篇
  2006年   16960篇
  2005年   14526篇
  2004年   12377篇
  2003年   10673篇
  2002年   8388篇
  2001年   7067篇
  2000年   5963篇
  1999年   5350篇
  1998年   4711篇
  1997年   4314篇
  1996年   3853篇
  1995年   3354篇
  1994年   2981篇
  1993年   2551篇
  1992年   2161篇
  1991年   1973篇
  1990年   1641篇
  1989年   1379篇
  1988年   1278篇
  1987年   1010篇
  1986年   972篇
  1985年   1618篇
  1984年   1644篇
  1983年   1141篇
  1982年   1221篇
  1981年   966篇
  1980年   826篇
  1979年   693篇
  1978年   513篇
  1977年   416篇
  1976年   385篇
  1975年   251篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的:研究脑缺血后脑片[Ca2+]i变化。方法:采用新型Ca2+荧光指示剂Fura-2双波长法测定兔大脑中动脉阻塞(MCAo)局灶脑缺血后脑片细胞内游离钙([Ca2+]i)。结果:脑缺血后脑组织[Ca2+]i显著升高。结论:[Ca2+]i在脑缺血损害中起重要作用。  相似文献   
992.
Although cardiac arrhythmias remain a serious clinical problem in many patients with heart disease, the exact role of antiarrhythmic drug therapy is currently under intense evaluation. Within the last several years it has become clear that there are significant risks as well as potential benefits associated with existing agents. Ongoing studies in large patient populations should help determine the benefit/risk ratio of traditional therapy. Regardless of the outcome of these trials, current electrophysiological dogma will have to be re-evaluated and newer concepts evolve for drug development to make further progress. The goal of this symposium is to exchange information among basic and clinical investigators so as to facilitate the emergence of novel electrophysiological concepts that will form the basis for future generations of antiarrhythmic drugs.  相似文献   
993.
Summary Serum high density lipoprotein (HDL) subfractions HDL2 and HDL3, apolipoproteins, and plasma antipyrine clearance (AP-CL) rate, an index of liver microsomal enzyme activity, were determined in 21 healthy subjects. High HDL cholesterol and HDL2 cholesterol concentrations and HDL cholesterol/cholesterol and HDL2/HDL3 cholesterol ratios were associated with high AP-CL. Phenobarbital enhanced antipyrine elimination and increased the apolipoprotein A-I/A-II ratio. Subjects who had high AP-CL had a more antiatherogenic HDL subfraction and apolipoprotein profile than those with low AP-CL.  相似文献   
994.
Summary The effects of 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (R-THBP) on the central cholinergic and dopaminergic systems in the Rhesus monkey brain were investigated by positron emission tomography (PET) with the muscarinic cholinergic receptor ligands (N-[11C]methyl-benztropine) and dopaminergic receptor ligands selective for D1 D2, and D3 subtypes ([11C]SCH23390, N-[11C]methyl-spiperone, and (+)[11C]UH232, respectively). None of the doses (3, 10, and 30 mg/kg i.v.) of R-THBP used significantly affected the regional cerebral blood flow (rCBF as determined by Raichle's H2 15O method), and 10 mg/kg of R-THBP had little effect on the regional cerebral metabolic rate of glucose (rCMRglc) in the Rhesus monkey brain, as assessed by the graphical [18F]fluoro-deoxyglucose method. The effect of R-THBP on the muscarinic cholinergic system was dose dependent; while 3 mg/kg of R-THBP did not significantly alter the uptake ratio of N-[11C]methyl-benztropine in several brain regions to that in the cerebellum, 10 and 30 mg/kg of R-THBP significantly reduced the uptake ratio in the thalamus, as well as in the frontal and temporal cortices. None of the doses (3, 10, and 30 mg/kg i.v.) of R-THBP tested affected [11C]SCH23390 (dopamine D1 receptor) binding. However, the k3 value for N-[11C]methyl-spiperone (dopamine D2 receptor) binding, which represents the association rate × Bmax value, was significantly decreased in the striatum. The uptake ratio of (+)[11C]UH232 (dopamine D3 receptor) in the striatum to that in the cerebellum was also decreased by administration of R-THBP (3 and 30 mg/kg i.v.). These findings suggest that R-THBP acts on dopamine D2 and D3 receptors selectively without markedly affecting dopamine D1 receptor binding. Furthermore, the changes in cholinergic and dopamine D2 and D3 receptors in vivo can not be attributed to a change in rCBF but may depend on the action of R-THBP.Abbreviations R-THBP 6R-L-erythro-5,6,7,8-tetrahydrobiopterin - PET positron emission tomography - rCBF regional cerebral blood flow - rCMRglc regional cerebral metabolic rate of glucose  相似文献   
995.
We attempted to find out the role of α2-adrenoceptors of the medullary lateral reticular nucleus (LRN) in antinociception in rats. Spinal antinociception was evaluated using the tail-flick test, and supraspinal antinociception using the hotplate test. Antinociceptive effects were determined following local electric stimulation of the LRN, and following microinjections of medetomidine (an α2-adrenoceptor agonist; 1–10 μg), atipamezole (an α2-adrenoceptor antagonist; 20 μg) or lidocaine (4%) into the LRN. The experiments were performed using intact and spinalized Hannover-Wistar rats with a unilateral chronic guide cannula. Electric stimulation of the LRN as well as of the periaqueductal gray produced a significant spinal antinociceptive effect in intact rats. Medetomidine (1–10 μg), when microinjected into the LRN, produced no significant antinociceptive effect in the tail-flick test in intact rats. However, following spinalization, medetomidine in the LRN (10 μg) produced a significant atipamezole-reversible antinociceptive effect in the tail-flick test in the hot-plate test, medetomidine (10 μg) in the LRN produced a significant atipamezole-reversible increase of the paw-lick latency in intact rats. Microinjection of atipamezole (20 μg) or lidocaine alone into the LRN produced no significant effects in the tail-flick test. The results are in line with the previous evidence indicating brat the LRN and the adjacent ventrolateral medulla is involved in descending inhibition of spinal nocifensive responses. However, α2-adrenoceptors in the LRN do not mediate spinal antinociception but, on the contrary, their activation counteracts antinociception at the spinal cord level. The spinal aninociceptive effect of supraspinally administered medetomidine in spinalized rats can be explained by a spread of the drug (e.g., via circulation) which then directly activates α2-adrenoceptors at the spinal cord level.  相似文献   
996.
人力资源管理信息系统的设计与分析   总被引:3,自引:0,他引:3  
人力资源管理是企业管理的重要基础工作,提高人力资源管理工作的科学性、有效性和效率,是当前人力资源管理工作的客观要求。结合企业人力资源管理的现状,本文讨论了人力资源管理信息系统的设计与开发。本系统能够完成企业员工信息的存储、备份、恢复、添加、删除、查询以及各类相关报表的打印。  相似文献   
997.
鼻息肉上皮细胞凋亡与bcl-2的表达及意义   总被引:4,自引:0,他引:4  
梁传余  田爱民 《四川医学》2003,24(12):1214-1216
目的 了解细胞的凋亡和癌基因bcl 2在鼻息肉的发病机制中的作用。方法 应用免疫组织化学的方法检测 45例鼻息肉细胞凋亡早期蛋白 (M3 0 )和bcl 2的表达 ,用下鼻甲粘膜作自身对照。结果 鼻息肉上皮和下鼻甲粘膜上皮的M3 0指数分别为 0 482± 0 3 2 ;1 0 62± 0 5 47,其差别有统计学意义 (P <0 0 1)。bcl 2阳性细胞在鼻息肉表层上皮和腺上皮均有表达 ,在下鼻甲中未见表达 ,其指数为 14 5 1± 4 46。结论 鼻息肉的发病机制及其生长过程与上皮细胞的增殖和凋亡的失平衡有关。bcl 2的表达可能是鼻息肉上皮凋亡抑制的原因 ,在鼻息肉上皮细胞增殖和凋亡失平衡的过程中起重要作用  相似文献   
998.
The effect of Panaxatriol Ginsenoside (PTGS) on Immune functions in bone marrow suppressed mice induced by injection of cyclophosphamide (CY) has been studied. Bone marrow suppressed mice were made by injection of CY (150 mg/kg) parenterally. Subcutaneous injection of PTGS three days earlier partially restored the number and the activity of bone marrow cells, significantly enhanced the production of IL-1, IL- 3 and IL- 6 like substances and promoted the reactivity of murlne spleen cells to Con-A In bone marrow suppressed mice.  相似文献   
999.
应用放射免疫分析法测定慢性活动性肝炎(CAH)和慢性迁延性肝炎(CPH)病人及健康人血清中游离白细胞介素2受体(fIL2R)水平,CAH和CPH病人的cpm分别是2326±617及1277±397,健康人仅为343±213。结果发现:CAH和CPH病人血清中fIL2R水平均显著高于健康人(P<0.01);CAH病人血清中fIL2R水平高于CPH病人(P<0.01)。提示,慢性乙型肝炎病人血清中fIL2R水平升高可能与其免疫应答异常及炎症活动性有关。  相似文献   
1000.
The core sequence of the enhancer of murine leukemia virus (MuLV) long terminal repeat is highly conserved in a large number of MuLV strains and appears to play an essential role when SL3-3 or Moloney strains induce T cell lymphoma in mice. We found by using the electrophoretic mobility shift assay that a polyomavirus enhancer core-binding protein, PEBP2, bound to this core motif of MuLV. We also noted that PEBP2 in several hematopoietic cell lines derived from B lymphocyte, macrophage and myelocyte lineages migrated significantly faster than the authentic PEBP2 detected in NIH3T3 (ibroblasts. Interestingly, PEBP2 detected in the cell lines of T lymphocyte lineage appeared to contain both types, which were indistinguishable in electrophoretic mobility from those of NIH3T3 and of B lymphocyte, macrophage and myelocyte lineages. The treatment of the nuclear extract containing PEBP2 with phosphatase generated PEBP3, which is a subcomponent of PEBP2 and retained the same DNA-binding specificity as PEBP2. The altered mobility of hematopoietic cell-derived or T lymphocyte-derived PEBP2 was found to be due to the alteration of the mobility of PEBP3. Based on the distinct mobility of PEBP2/3 of T lymphocytes from those of other hematopoietic cells, we discuss the implication of PEBP2 in MuLV-induced T cell leukemia and T cell-specific gene expression.  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