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   28884篇
  免费   1840篇
  国内免费   753篇
耳鼻咽喉   126篇
儿科学   458篇
妇产科学   373篇
基础医学   6791篇
口腔科学   557篇
临床医学   1696篇
内科学   3950篇
皮肤病学   704篇
神经病学   1398篇
特种医学   360篇
外国民族医学   4篇
外科学   2629篇
综合类   4165篇
现状与发展   1篇
预防医学   1546篇
眼科学   258篇
药学   3240篇
  8篇
中国医学   1573篇
肿瘤学   1640篇
  2024年   66篇
  2023年   377篇
  2022年   607篇
  2021年   919篇
  2020年   920篇
  2019年   991篇
  2018年   839篇
  2017年   933篇
  2016年   900篇
  2015年   989篇
  2014年   1717篇
  2013年   2013篇
  2012年   1621篇
  2011年   2085篇
  2010年   1649篇
  2009年   1720篇
  2008年   1493篇
  2007年   1482篇
  2006年   1410篇
  2005年   1118篇
  2004年   1045篇
  2003年   892篇
  2002年   669篇
  2001年   490篇
  2000年   506篇
  1999年   412篇
  1998年   398篇
  1997年   304篇
  1996年   337篇
  1995年   306篇
  1994年   281篇
  1993年   202篇
  1992年   164篇
  1991年   121篇
  1990年   74篇
  1989年   52篇
  1988年   35篇
  1985年   156篇
  1984年   189篇
  1983年   135篇
  1982年   170篇
  1981年   136篇
  1980年   105篇
  1979年   115篇
  1978年   70篇
  1977年   53篇
  1976年   45篇
  1975年   53篇
  1974年   29篇
  1973年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A low intake of selenium is associated with increased cardiovascular mortality. This could be reduced by supplementation with selenium and coenzyme Q10. D-dimer, a fragment of fibrin mirroring fibrinolysis, is a biomarker of thromboembolism, increased inflammation, endothelial dysfunction and is associated with cardiovascular mortality in ischemic heart disease. The objective was to examine the impact of selenium and coenzyme Q10 on the level of D-dimer, and its relationship to cardiovascular mortality. D-dimer was measured in 213 individuals at the start and after 48 months of a randomised double-blind placebo-controlled trial with selenium yeast (200 µg/day) and coenzyme Q10 (200 mg/day) (n = 106) or placebo (n = 107). The follow-up time was 4.9 years. All included individuals were low in selenium (mean 67 μg/L, SD 16.8). The differences in D-dimer concentration were evaluated by the use of T-tests, repeated measures of variance and ANCOVA analyses. At the end, a significantly lower D-dimer concentration was observed in the active treatment group in comparison with those on placebo (p = 0.006). Although D-dimer values at baseline were weakly associated with high-sensitive CRP, while being more strongly associated with soluble tumour necrosis factor receptor 1 and sP-selectin, controlling for these in the analysis there was an independent effect on D-dimer. In participants with a D-dimer level above median at baseline, the supplementation resulted in significantly lower cardiovascular mortality compared to those on placebo (p = 0.014). All results were validated with a persisting significant difference between the two groups. Therefore, supplementation with selenium and coenzyme Q10 in a group of elderly low in selenium and coenzyme Q10 prevented an increase in D-dimer and reduced the risk of cardiovascular mortality in comparison with the placebo group. The obtained results also illustrate important associations between inflammation, endothelial function and cardiovascular risk.  相似文献   
92.
93.
94.
95.
凝血酶对人重组内皮细胞衍生IL—8融合蛋白转换作用   总被引:3,自引:0,他引:3  
本文报道利用基因工程技术在大肠杆菌中表达出入内皮细胞衍生IL-8(EDhIL-8)与细菌蛋白lacZ 的融合蛋白lac-hIL-8和lac-T-hIL-8,后者含有一个人工合成凝血酶切点。EDhIL-8上含有一个凝血酶切点,凝血酶可以将lac-hIL-8及以前表达的MS2-hIL-8水解为有生物活性的天然IL-8,而对含有两个凝血酶切点的lac-T-hIL-8无水解作用。这些结果提示凝血酶的功能不仅依赖于所识别的氨基酸,而且依赖于这些氨基酸形成的构象。  相似文献   
96.
The ability of LAK cells and/or IL-2 to affect the course of an established T cell response was examined in a delayed-type hypersensitivity (DTH) model. IL-2 greatly increased the magnitude of the response at 24 h, while LAK cells alone had no effect. The administration of LAK cells and IL-2 together also had no effect on the magnitude of the DTH response, demonstrating that LAK cells were able to remove the enhancement seen with IL-2 alone. The presence of LAK cells reduced the serum half-life of IL-2 significantly, but not to an extent able to account for the observed loss of IL-2 induced DTH enhancement. IL-2 administration influenced cell phenotypes in the spleen and draining lymph nodes (DLN), as well as increasing splenic weight; the additional presence of LAK cells markedly altered these effects of IL-2 in the spleen (but not the DLN). Taken together, these results suggest that LAK cells interact with activated T-cells within the immune system and modulate their function.  相似文献   
97.
Summary The therapeutic efficacy and toxicity of three biological response modifiers,Corynebacterium parvum (Cp), Chinese blister beetle extract (CBBE), recombinant human IL-1 (rhIL-1), used alone or in combination with chemotherapy or radiotherapy, were investigated in the intracerebral (ic) rat 9L brain tumor model. Used alone, Cp (2mg/rat, ip plus 70g/rat, ic), CBBE (5l of an ethanol extract, ic), or IL-1 (lg/rat, ic or 1g/rat × 3, q 3 d, ic), had no effect on animal survival compared to the untreated or saline treated controls. When combined with chemotherapy or radiotherapy, the three immunotherapeutic agents did not show any additive effects on survival compared to that observed with systemic BCNU (12mg/kg), local ic bleomycin (0.25 unit), or local radiotherapy (16 Gy). While ic IL-1 did not produce evident toxicity, there was fatal toxicity caused by ic Cp or CBBE treatment in a few animals. The combination of Cp and bleomycin produced severe neurotoxicity, resulting in the early death of animals. This study demonstrates a lack of efficacy of the nonspecific immune adjuvants IL-1, Cp or CBBE, used either alone or combined with cytotoxic chemotherapy or radiotherapy, in this rat brain tumor model.  相似文献   
98.
急性胰腺炎患者IL-6、TNFα水平测定及临床意义   总被引:1,自引:0,他引:1  
目的研究急性胰腺炎患者IL-6、TNFα分泌情况及其临床意义。方法选择30例急性胰腺炎患者和28例健康对照,用生物学方法检测血浆中IL-6、TNFα的水平。结果急性胰腺炎患者血浆中IL-6、TNFα分别为(76.4±10.1)k u/L、60.7%±12.3%,均高于正常对照组(20.8±6.1)ku/L、12.4%±4.7%,随疾病的恢复逐渐趋于正常(28.5±9.1)ku/L、18.8%±6.4%。结论急性胰腺炎患者血浆中的IL-6、TNFα水平均高于正常组,说明二者参与这一炎症过程。  相似文献   
99.
Purpose The aim of our study is to elucidate whether human oocyteslembryos secrete IFN and/or IL-10 and whether the fertilization process depends on the balance between these cytokines.Methods A total of 142 embryo culture media from 24 patients were collected and the cytokine levels were tested with ELISA.Results IFN and IL-10 were detectable in 40.1% and 29.6% of culture media respectively. The difference of IFN and IL-10 levels in media from fertilized oocytes between day 1 and day 2 are significant (0.46 vs. 1.47 and 34.2 vs. 12.7, respectively). However there was no significant difference between the IFN levels of the media from fertilized and nonfertilized oocytes 0.46 vs. 0.85 at day 1 and 1.47 vs. 1.49 at day 2, as well as IL-10 levels 34.2 vs. 30.9 at day 1 and 12.7 vs. 9.58 at day 2 respectively.Conclusions Human preimplantation embryos secrete the cytokines IFN and IL-10. No effect of these cytokines on fertilization process could be shown.Presented at the IXth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction, April 3–7, 1995, Vienna, Austria.  相似文献   
100.
We perform systematically amino acid analysis of the CSF before and after strong acid hydrolysis in children with unexplained neurological disease. By comparing the amino acid pattern before and after hydrolysis, defects can be traced in the metabolism not only of amino acids but also of purines, peptides, N-acetylated amino acids and peptides, and probably other compounds. This method has yielded important information such as the identification of two new diseases, GABA transaminase deficiency and adenylosuccinase deficiency, and the discovery of a peculiar, acid-labile double peak in the CSF of patients with the transient neonatal hyperammonaemia syndrome and with urea cycle defects. This substance was subsequently identified by others as -glutamylglutamine. As a consequence, we strongly recommend incorporating of this approach in the investigation of all children with unclear neurological disease.  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