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   8297篇
  免费   515篇
  国内免费   324篇
耳鼻咽喉   26篇
儿科学   96篇
妇产科学   102篇
基础医学   801篇
口腔科学   363篇
临床医学   748篇
内科学   1550篇
皮肤病学   76篇
神经病学   337篇
特种医学   133篇
外国民族医学   2篇
外科学   561篇
综合类   1757篇
预防医学   345篇
眼科学   85篇
药学   1411篇
  4篇
中国医学   553篇
肿瘤学   186篇
  2023年   26篇
  2022年   123篇
  2021年   208篇
  2020年   229篇
  2019年   94篇
  2018年   96篇
  2017年   217篇
  2016年   330篇
  2015年   300篇
  2014年   612篇
  2013年   786篇
  2012年   933篇
  2011年   861篇
  2010年   732篇
  2009年   630篇
  2008年   530篇
  2007年   278篇
  2006年   244篇
  2005年   232篇
  2004年   214篇
  2003年   168篇
  2002年   176篇
  2001年   128篇
  2000年   125篇
  1999年   107篇
  1998年   70篇
  1997年   55篇
  1996年   52篇
  1995年   47篇
  1994年   41篇
  1993年   45篇
  1992年   42篇
  1991年   35篇
  1990年   21篇
  1989年   24篇
  1988年   30篇
  1987年   24篇
  1986年   20篇
  1985年   23篇
  1984年   27篇
  1982年   21篇
  1981年   19篇
  1980年   15篇
  1979年   15篇
  1978年   15篇
  1977年   16篇
  1976年   20篇
  1975年   13篇
  1974年   13篇
  1973年   18篇
排序方式: 共有9136条查询结果,搜索用时 15 毫秒
21.
目的探讨血管紧张素Ⅱ对单核细胞趋化蛋白1受体CCR2表达的影响及氯沙坦的干预作用。方法人单核细胞株与血管紧张素Ⅱ(10-7mol/L)孵育,加或不加氯沙坦(10-7、10-6和10-5mol/L),检测上清液中单核细胞趋化蛋白1水平、单核和内皮细胞粘附情况以及CCR2mRNA的表达。结果与对照组比较,血管紧张素Ⅱ明显增加单核细胞培养上清液中单核细胞趋化蛋白1水平(26.46±3.58ng/L比10.56±2.34ng/L,P<0.01),增加单核内皮细胞间粘附(596±27比268±16,P<0.01)。血管紧张素Ⅱ刺激细胞后明显上调CCR2mRNA表达,氯沙坦能显著抑制血管紧张素Ⅱ的作用,降低单核细胞趋化蛋白1的水平,减少单核内皮细胞间粘附,下调CCR2 mRNA表达。结论氯沙坦通过下调单核细胞趋化蛋白1受体CCR2基因表达抑制单核细胞活化。  相似文献   
22.
目的评价采用非离子低分子对比剂行冠脉造影和介入治疗对于肾功能的影响,并比较单纯冠脉造影和冠脉介入治疗手术前后肾功能的差异;评价氯沙坦对于冠脉介入治疗前后肾功能(血肌酐)和尿微量白蛋白的影响。方法根据冠状动脉造影的结果将我院收治的171例患者分3组,第1组为造影阴性组(CAG,73例),第2组为常规介入治疗组(PCI,52例),第3组为介入治疗 氯沙坦组(46例);研究对比剂对3组肾脏功能和尿微量白蛋白的影响。在检查前及术后的第1、3、7天分别测试尿微量白蛋白和肾功能(血肌酐),然后比较对比剂碘佛醇应用前后各组的差异。结果各组血肌酐均无明显变化,而PCI组尿微量白蛋白比CAG组的患者高(P<0.05);在氯沙坦干预后,PCI后尿微量白蛋白有明显下降(P<0.05)。结论CAG和PCI时,非离子低分子对比剂对肾功能(血肌酐)无明显影响,而尿微量白蛋白在术后有不同程度的升高,在PCI组中更明显;氯沙坦能降低PCI术后的尿微量白蛋白,可能具有预防对比剂肾病的作用。  相似文献   
23.
Ramipril blocks the conversion of angiotensin I to II. The literature indicates that diabetes is often associated with mild impairment of learning and memory. The study reports the effects of ramipril on memory retention in diabetic and non-diabetic mice. Mice were made diabetic by an injection of streptozocin. After overt signs of diabetes were present, diabetic or vehicle-treated mice were partially trained on a footshock active avoidance task. Immediately after training, ramipril (0.5–1.5 mg/kg s.c.) was administered and retention was tested by continuing training one week later until mice avoided footshock on five out of six trails. The results indicate that ramipril enhanced retention of both diabetic and control mice but it required about 5 times as much ramipril in diabetic as control mice to achieve the same effect on retention. Increased sensitivity to angiotensin II may play a role in cognitive impairment in diabetes.  相似文献   
24.
目的 :了解活化血小板葡萄糖摄取过程及血小板膜整合素对其影响 ,探讨整合素与血小板能量代谢的关系 ,旨在研究血小板能量代谢涉及的信号传导 ,并为目前临床应用血小板膜糖蛋白Ⅱb/Ⅲa(GPⅡb/Ⅲa)单抗抗血小板活化提供新的理论依据。方法 :用液态闪烁计数方法检测在血小板膜糖蛋白Ⅱb/Ⅲa单抗 10E5及血小板整合素αυβ3 单抗 6 0 9干预与否情况下凝血酶激活后血小板摄取氚标 2 脱氧葡萄糖 ([3 H]2 DG)率。结果 :在生理浓度范围内活化血小板 [3 H]2 DG摄取率较静息时明显升高 ,单抗 10E5可充分阻断活化血小板葡萄糖摄取 ,单抗 6 0 9可部分阻断。结论 :整合素家族单抗可抑制血小板激活后葡萄糖摄取 ,提示其可能参与血小板能量代谢信号传导过程 ,并可能以GPⅡb/Ⅲa为主  相似文献   
25.
目的 研究全麻诱导以及手术对肥胖患者血浆抵抗素 (resistin)和肾素、血管紧张素Ⅱ及血糖的影响。方法 选择 4 0例全麻手术患者 ,根据BMI指数分为两组 :A组 (BMI>2 5 ) 2 0例为肥胖者 ;B组 (2 1 相似文献   
26.
Two experiments were performed to investigate the relationship between the expression of sodium appetite and the appearance of Fos-like immunoreactivity (Fos-IR) in the brain of rats. In the first experiment, rats were depleted of sodium by treatment with furosemide 24 h prior to sacrifice and without access to either food or sodium solution. Some rats had access to distilled water, and others had no fluids available during the 24 h. All of the furosemide-treated rats showed Fos-IR in both the subfornical organ (SFO) and around the organum vasculosum laminae terminalis (OVLT). Rats with access to distilled water during the depletion period showed no Fos-IR in the supraoptic (SON) or paraventricular hypothalamic nuclei (PVN) and, in parallel behavioral studies, comparably-treated rats consumed only 0.3 M NaCl solution at the end of the 24 h. In rats that had no fluids during the deprivation period, only about one half showed Fos-IR in SON and PVN and, in parallel behavioral studies, comparably treated rats consumed both water and 0.3 M NaCI solution at the end of 24 h. In a second experiment, cerebroventricular administration of renin stimulated short latency intake of 0.3 M NaCI and water. The relative intakes of water and NaCl were comparable at a low dose of renin, but intake of water exceeded that of NaCl after higher doses. Renin induced Fos-IR in SFO, MnPO, peri-OVLT region, SON and PVN. Both Fos-IR and fluid intake were antagonized by administration of losartan, an angiotensin 11 type 1 receptor antagonist. Thus, only the circumventricular organs of the lamina terminalis showed Fos-IR during each natriorexigenic regimen in these studies. These data support the view that Ang 11 of both central and peripheral origin activates the SFO and/or peri-OVLT region and contributes to sodium appetite.  相似文献   
27.
Summary Bradykinin (BK) initially produced concentration-related relaxations of human basilar artery in vitro. Concentration-effect curves constructed at 2 h intervals to BK over an 8 h period were reproducible. The rank order of potency of three kinins on the human basilar artery was found to be BK > methionyl-lysyl-BK > des-Arg9-BK. The B2-receptor antagonist Thi5,8 d-Phe7-BK but not the B1-receptor antagonist des-Arg9-Leu8-BK selectively blocked BK-induced relaxations of the human basilar artery.The relaxant effects of bradykinin and acetylcholine but not papaverine were attenuated after removal of the endothelium or treating the tissues with BW755C. Indomethacin was without effect. Concentration-effect curves to angiotensin I were markedly attenuated by captopril at a concentration which had no effect on BK, angiotensin II or 5-hydroxytryptamine responses. It is concluded that BK induced relaxations of the human basilar artery are mediated via activation of a B2 receptor and the response is dependent upon the release of a factor present in the endothelium. Angiotensin converting enzyme is present in the human basilar artery and is important for the conversion of angiotensin I to angiotensin II but apparently not for the degradation of BK. It is likely that other kininases are present and active in the tissue. Send offprint requests to E. T. Whalley at the above address  相似文献   
28.
心包肽类激素免疫组织化学及免疫电镜的研究   总被引:3,自引:0,他引:3       下载免费PDF全文
采用免疫组织化学、免疫电子显微镜及高效液相结合放射免疫学方法,研究人和 Wistar 大鼠心包,结果表明:心包组织中存在 ANF 和 AngⅡ样物质。在采用兔抗 ANF 为抗体时,心包组织的间皮细胞存在明显的金粒子标记颗粒,间皮细胞是主要的内分泌细胞。心包组织存在 Ang Ⅱ和3种分子形式ANF.本研究提示.心包除已知功能外,尚存在重要的内分泌功能.  相似文献   
29.
Rats with impaired active avoidance induced by chronic (9 weeks) administration of ethanol were studied. Angiotensin II (ANG II) administered (ICV, 2.0 g) 12 h after the withdrawal of the alcohol not only neutralized the toxic effect of ethanol but also improved learning. When administered on the 5th day after ethanol withdrawal, the effect of ANG II was weaker. Tests of stereotypy and catalepsy were used to study the possible role of the dopaminergic system in this action of ANG II. It was shown that both chronic alcohol treatment and ANG II alone increased apomorphine (1 mg/kg) and amphetamine (7.5 mg/kg) stereotypy but the effects of ANG II were greater. ANG II did not change the stereotypy induced by amphetamine but increased the stereotypy induced by apomorphine in the group of animals chronically treated with alcohol. Haloperidol — induced catalepsy was reduced in these rats. ANG II alone intensified catalepsy and eliminated the effect of ethanol. Both ANG II and alcohol increased striatal dopamine (DA) concentration. This effect of ANG II was significantly greater in the animals chronically treated with alcohol. The above changes were not observed after the DA level had been reduced by alpha-methyl-p-tyrosine (250 mg/kg), nor were changes observed in the striatal DOPAC. The results suggest involvement of the central dopaminergic system in the effect of ANG II on the ethanol — induced impairment of acquisition of active avoidance but, however, the results of the biochemical determinations of DA turnover do not provide an explanation of these changes.  相似文献   
30.
背景 退行性腰椎管狭窄症(DLSS)是一种老年多发,严重影响患者正常生活且医疗费用负担较重的疾病。DLSS治疗方法较多,开发高质量的临床实践指南和临床医生应用高质量指南是提高DLSS诊疗水平的重要途径。目的 采用AGREEⅡ及RIGHT评价DLSS相关指南的方法学及报告质量,为DLSS指南制订及报告提供参考依据。方法 计算机检索中国生物医学文献数据库(CBM)、中国知网(CNKI)、万方数据知识服务平台(Wanfang Data)、维普网(VIP)、PubMed,补充检索医脉通数据库(Medlive)、世界卫生组织(WHO)、英国国家临床优化研究所(NICE)、国际指南协作网(GIN)、美国国立指南文库(NGC)和苏格兰院际间协作网(SIGN)等指南库中有关DLSS的临床实践指南、共识或规范,检索时限均为2010-01-01至2022-01-01。由两位评价员独立对纳入文献进行方法学质量及报告质量评价,并在文献中推荐意见等级统一前提下进行比较。结果 共纳入6篇文献,其中4篇指南,2篇共识;1篇指南为中医指南,3篇指南为循证指南。AGREEⅡ评价结果显示纳入6篇文献的实际总得分/总最高可...  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