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   208099篇
  免费   15287篇
  国内免费   5089篇
耳鼻咽喉   1644篇
儿科学   2839篇
妇产科学   3311篇
基础医学   25033篇
口腔科学   4059篇
临床医学   15143篇
内科学   29087篇
皮肤病学   2380篇
神经病学   12661篇
特种医学   7705篇
外国民族医学   4篇
外科学   23013篇
综合类   28780篇
现状与发展   25篇
一般理论   8篇
预防医学   15781篇
眼科学   2397篇
药学   27318篇
  102篇
中国医学   13139篇
肿瘤学   14046篇
  2024年   335篇
  2023年   2847篇
  2022年   4796篇
  2021年   9110篇
  2020年   7634篇
  2019年   7373篇
  2018年   7366篇
  2017年   7895篇
  2016年   8134篇
  2015年   7651篇
  2014年   9610篇
  2013年   13361篇
  2012年   11045篇
  2011年   13046篇
  2010年   8503篇
  2009年   8406篇
  2008年   9702篇
  2007年   10629篇
  2006年   9918篇
  2005年   9060篇
  2004年   7750篇
  2003年   6834篇
  2002年   5419篇
  2001年   4809篇
  2000年   4042篇
  1999年   3422篇
  1998年   2688篇
  1997年   2762篇
  1996年   2529篇
  1995年   2199篇
  1994年   2136篇
  1993年   1772篇
  1992年   1639篇
  1991年   1535篇
  1990年   1320篇
  1989年   1078篇
  1988年   1047篇
  1987年   942篇
  1986年   869篇
  1985年   1251篇
  1984年   995篇
  1983年   752篇
  1982年   781篇
  1981年   635篇
  1980年   607篇
  1979年   488篇
  1978年   311篇
  1977年   267篇
  1976年   246篇
  1975年   189篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
971.
经对292例正常胎儿枕额径和双顶径的外测量,结果表明,枕额径和双顶径都随着胎龄的增长而增大,但其生长速度则随着胎龄的增长而逐渐减慢。经回归分析原理,分别得出预测方程。枕额径增长的速度和双顶径增长的速度没有明显差异(P>0.05)。  相似文献   
972.
本文介绍正常人113名,肺部恶性病变49例及肺部良性病变33例的血清LSA测定结果,正常人血清LSA含量平均值为0.1243±0.0358g/L。特异性97.40%,男女间无差异,48例肺癌血清LSA平均值0.2698±0.0915g/L,敏感性85.40%;33例良性病变LSA平均值0.1712±0.0767g/L,特异性78.79%。肺癌患者血清LSA较良性病变明显升高,故测定血清LSA对鉴别良恶性病变有一定价值。  相似文献   
973.
The chemokines, macrophage inflammatory protein-1 (MIP-1) and its subunit MIP-1β, induce an intense fever in the rat when they are injected directly into the anterior hypothalamic, pre-optic area (AH/POA), a region containing thermosensitive neurons. The purpose of this study was to compare the central action on body temperature (Tb) of MIP-1β with that of interleukin-6 (IL-6), which also has been implicated in the cerebral mechanism underlying the pathogenesis of fever. Following the stereotaxic implantation in the AH/POA of guide cannulae for repeated micro-injections, radio transmitters which monitor Tb continuously were inserted intraperitoneally in each of 15 male Sprague-Dawley rats. Each micro-injection was made in a site in the AH/POA in a volume of 1.0 μl of pyrogen-free artificial CSF, recombinant murine MIP-1β, or recombinant human IL-6. MIP-1β in a dose of 25 pg evoked an intense fever characterized by a short latency, a mean maximum rise in Tb of 2.4 ± 0.21°C reached by 3.7 ± 0.42 hr, and a duration exceeding 6.5 hr. Injected into homologous sites in the AH/POA, IL-6 induced a dose dependent fever of similar latency and a mean maximal increase in Tb of 1.2 ± 0.25°C, 1.8 ± 0.15°C, and 2.1 ± 0.22°C and duration of 6.2 ± 1.28 hr, 6.7 ± 0.49 hr, and 6.8 ± 0.65 hr when given in doses of 25, 50, and 100 ng, respectively. These results show that MIP-1β and the highest dose of IL-6 induce a fever of comparable intensity, but MIP-1β exerts its action in a much lower concentration. Thus, the de novo synthesis and subsequent action of the MIP-1 family of cytokines on neurons of the AH/POA in response to a pyrogen challenge apparently play a functional role in the pathogenesis of fever. Further, the endogenous activity of IL-6 in the hypothalamus which is enhanced in response to a lipopolysaccharide also may reflect its essential part in the acute phase response to a bacterial challenge. Copyright © 1994 Wiley-Liss, Inc.  相似文献   
974.
The indications, contraindications and complications of percutaneous laparoscopic cholecystectomy (PLC) were established from a group of 308 patients referred for cholecystectomy. Of the 308 patients 86% underwent PLC, 5% were commenced laparoscopically, but converted to open cholecystectomy and 9% were performed as open cholecystectomy from the outset. Complications included two bile leaks from the gall-bladder bed, one cystic duct stump leak and three retained stones. Pre-operative rather than intra-operative duct imaging was used so that common duct stones could be removed before operation. PLC is a safe procedure that has now become the standard technique for cholecystectomy.  相似文献   
975.
本实验采用小剂量、长期给药的方法观察了人参总甙对正常家兔血液流变学的影响。结果表明人参总甙具有降低正常家兔血液粘度和血小板聚集性的作用,这可能是人参增加组织血流量、防治心血管疾患的重要依据。  相似文献   
976.
采用人外周血淋巴细胞非程序DNA合成(UDS)试验和人胚肺成纤维细胞转化试验,测试了煤焦沥青烟雾提取物(ECTPF)对人体细胞的细胞毒性和遗传毒性。UDS试验结果表明,ECTPF可使淋巴细胞UDS值明显增加,并有剂量一反应关系。引起半数淋巴细胞死亡的浓度(LC50)为33.8μg/ml。细胞转化试验表明,ECTPF能诱发人胚肺成纤维细胞明显的形态学转化,且转化细胞具有部分恶性转化细胞的特性。引起半数人胚肺成纤维细胞生长抑制的浓度为41.3μg/ml。实验结果提示,ECTPF是一种具有细胞毒性和遗传毒性的物质。  相似文献   
977.
Pellets formed from isolated bovine growth plate chondrocytes were grown in various capacitively coupled electrical fields. The signals chosen were 0, 10, 100, 250, 500, 750, 1,000, and 1,500 V peak-to-peak, 60 kHz. The effect on cell proliferation and matrix production of these different voltages was determined by [3H]thymidine and [35S]sulfate uptake, respectively, Cyclic AMP assays were done to determine if increases in either thymidine or sulfate uptake were associated with changes in cAMP levels. Significantly increased cell proliferation occurred at 500, 750, and 1,000 V peak to peak. The calculated electric fields were 1.5 to 3.0 x 10(-2) V/cm. Proliferation was significantly inhibited at 1,500 V peak-to-peak with a calculated field of 4.5 x 10(-2) V/cm. Little if any change was seen in cAMP levels at 30 or 60 min following application of the appropriate electric signals.  相似文献   
978.
Summary An unusual case of chronic myelocytic leukemia (CML) is described that presented leukocytosis at onset (720×109/l), symptoms of stasis, organomegaly, and a conspicuous infiltration of leukemic cells from the pelvis to the right popliteal cavity. As initial therapy and in addition to chemotherapy, six therapeutic leukapheresis treatments (TL) were performed and the patient showed dramatic symptomatic improvement with reduction in leukocytosis (97×109/l), organomegaly, and tissue infiltration.  相似文献   
979.
In human cortex and hippocampus area, [3H]5-HT (5 nM) labels 5-HT1A, 5-HT1D and 5-HT1E sites. After masking 5-HT1A receptors by 0.1 μM 8-OH-DPAT, the binding displaced by 0.1 μM 5-CT presumably represented 5-HT1D sites and the remaining binding 5-HT1E sites. In frontal cortex, 5-HT1A receptors represented the main binding in layers II and VI and a lower fraction on other layers. 5-HT1D and 5-HT1E sites, were more homogeneously distributed in layers II to VI (21–34% of specific [3H]5-HT binding). 5-HT1E sites were of similar affinities (KD close to 6–8 nM) in the cortical layers II to VI. In CA1 field of hippocampus, (pyramidal layer, stratum radiatum, molecular layer), CA2 and dentate gyrus, 5-HT1A receptors represented the major fraction, 5-HT1D sites a significant fraction and 5-HT1E a minor fraction of the specific [3H]5-HT binding. In CA3–CA4 fields, 5-HT1A receptors were less densely present, 5-HT1D sites were predominant and 5-HT1E sites represented a significant fraction (27%). The highest densities of 5-HT1E sites have been measured in subiculum, where 5-HT1A, 5-HT1D, and 5-HT1E binding sites were equally represented and in entorhinal cortex where 5-HT1E sites represented the major binding in layer III. They were also present in layers II and IV (29 and 24%) and, to a lesser extent, in layers V and VI. 5-HT1A sites were predominant in layer VI, II and V and were less abundant in other layers. 5-HT1D were homogeneously present in layers II, III, IV and were present in low amounts in other layers. No 5-HT1E were detected in choroid plexus, where [3H]5-HT was dramatically reduced by mesulergine (5-HT2C receptors). No significant displacement of [3H]5-HT by mesulergine was measured in other structures.  相似文献   
980.
A review is presented about fagaronine, a benzophenanthridine alkaloid responsible for antitumoural activity. Plant source, extraction, biosynthesis, medicinal properties, especially antileukaemic activity, are described.  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