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   192082篇
  免费   2478篇
  国内免费   1341篇
耳鼻咽喉   1289篇
儿科学   6820篇
妇产科学   3166篇
基础医学   18565篇
口腔科学   1884篇
临床医学   14672篇
内科学   33028篇
皮肤病学   831篇
神经病学   17301篇
特种医学   9489篇
外国民族医学   15篇
外科学   30286篇
综合类   5399篇
现状与发展   1篇
一般理论   2篇
预防医学   19406篇
眼科学   3255篇
药学   11217篇
  22篇
中国医学   1564篇
肿瘤学   17689篇
  2024年   35篇
  2023年   234篇
  2022年   544篇
  2021年   872篇
  2020年   640篇
  2019年   552篇
  2018年   22444篇
  2017年   17864篇
  2016年   19958篇
  2015年   1702篇
  2014年   1686篇
  2013年   1621篇
  2012年   8212篇
  2011年   22456篇
  2010年   19708篇
  2009年   12342篇
  2008年   20530篇
  2007年   22709篇
  2006年   1474篇
  2005年   3154篇
  2004年   3931篇
  2003年   4797篇
  2002年   2871篇
  2001年   633篇
  2000年   829篇
  1999年   556篇
  1998年   467篇
  1997年   426篇
  1996年   261篇
  1995年   273篇
  1994年   251篇
  1993年   189篇
  1992年   158篇
  1991年   203篇
  1990年   209篇
  1989年   155篇
  1988年   115篇
  1987年   101篇
  1986年   71篇
  1985年   68篇
  1984年   33篇
  1983年   32篇
  1982年   33篇
  1980年   42篇
  1938年   60篇
  1937年   25篇
  1935年   22篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
加锌对大鼠脑内微量元素的影响   总被引:1,自引:0,他引:1  
用SD雌性成年大鼠20只,随机分为实验组和对照组各10只。加锌40d后,用原子吸收分光光度计(日本津岛)分别测定了两组大鼠大脑皮质感觉运动区和海马CA3区的微量元素Zn、Cu、Fe和轻金属Mg的含量。结果表明:在大脑皮质感觉运动区,两组大鼠的诸元素含量无显著变化;在海马CA3区,两组大鼠的微量元素Zn、Cu、Fe的含量也无显著变化(P>0.05),但轻金属Mg的含量却发生了显著的变化,表现为对照组明显高于实验组(P<0.05)。  相似文献   
42.
43.
44.
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences.  相似文献   
45.
原发性甲状腺功能亢进症合并甲状腺癌18例分析   总被引:1,自引:0,他引:1  
目的:探讨原发性甲状腺功能亢进症(甲亢)合并甲状腺癌(甲癌)的诊断和治疗。方法:回顾分析1990年1月于2000年1月手术治疗18例甲亢合并甲癌患者的临床资料,结果:微小癌占83%(15/18)。术前彩超检查15例,14例发现可疑结节;13例行癌侧叶全切除和对侧叶次全切除术,5例行双侧叶次全切除术,其中3例同时行颈淋巴结清扫术,1例二次行颈淋巴结清扫术。随访16例,平均随访7年,1例死于癌肺转移,余者仍存活,结论:术前常规彩超检查发现可疑结节有助于术中冰冻切片病理检查,手术治疗应兼顾甲亢和甲癌。  相似文献   
46.
47.
The treatment of deep cartilage defects in load-bearing joints is a problem that still has no satisfactory solution. Full-thickness defects of the articular cartilage rarely heal spontaneously, usually leaving damage that can lead to early arthrosis. Techniques currently available for the treatment of chondral defects include abrasion, drilling, micro-fracturing, transplantation of tissue autografts and allografts, and cell transplantation. Osteochondral autograft transplantation is currently the only surgical cartilage repair technique known to lead to the formation of genuine hyaline articular cartilage and its retention at least in the medium term. The Draenert method, in which a water-cooled diamond bone-cutting system is used, is an effective procedure for resurfacing the joints affected by localised cartilaginous defects, even when there is also severe bone loss. Donor-side morbidity can be kept to a minimum by filling the defect caused by harvesting with a press-fit cylinder of cancellous bone covered with periosteum for protection.  相似文献   
48.
Ischemic injury plays an important role in chronic renal transplant failure (CRTF). Down-regulation of ecto-adenosine triphosphatase (ATPase) in combination with up-regulation of ecto-5'-nucleotidase is a hallmark of ischemic injury. We studied the expression of renal ecto-5'-nucleotidase and ecto-ATPase in experimental renal transplantation. Fisher 344-to-Lewis allografted rats were either treated with an angiotensin-converting enzyme inhibitor (ACEi) or left untreated. Lewis-to-Lewis syngrafted rats served as controls. Untreated allografted rats developed proteinuria, glomerulosclerosis, and mild intimal hyperplasia. ACEi completely prevented focal and segmental glomerulosclerosis (FGS) and proteinuria, but significantly enhanced intimal hyperplasia. Untreated allografted rats revealed marked vascular ecto-5'-nucleotidase activity, which increased with ACEi. Vascular ecto-5'-nucleotidase activity was absent in syngrafted animals. Ecto-5'-nucleotidase activity correlated well with intimal hyperplasia. Glomerular ecto-ATPase expression was significantly reduced in untreated allografted rats compared to syngrafted rats and correlated well with the extent of FGS. ACEi prevented reduction in glomerular ecto-ATPase. We found de-novo expression of ecto-5'-nucleotidase at sites of renal intimal hyperplasia. Glomerular ecto-ATPase expression was markedly reduced in allografted rats and was prevented by ACEi. These enzyme expression patterns suggest local ischemic damage in experimental CRTF.  相似文献   
49.
Contemporary discourse contains numerous examples of use of the concept of culture by social and behavioral scientists. Simple reification, where the speaker makes culture into a thing capable of action exemplifies one usage in public discourse. Some quantitative social scientists attempt to characterize people’s cultural identities by means of a single categorical variable, which often “lumps” people into categories such as “Hispanic” or “Black” that in fact have numerous culturally bounded subcategories. Approaches that emphasize cultural process are preferable to those who attempt to categorize; more complex measures of acculturation help investigators to make convincing analyses of circumstances in which health disparities occur. Examples in which investigators make appropriate use of cultural characterizations demonstrate their utility in investigating health disparities in Haitian American women, injecting and noninjecting drug users, Hispanic youth, and adult Hispanics at risk of HIV infection. Focus on culture in the study of health disparities can identify entanglements between structural factors such as poverty and lack of education and cultural factors such as beliefs about health. Qualitative methods coupled with quantitative methods have great potential to improve investigators’ grasp of cultural nuance while capturing the distribution of qualitatively derived behaviors.  相似文献   
50.
目的:观察按阴阳辨证分类组方联合拉米夫定治疗慢性乙型肝炎(CHB)的临床疗效。方法:90例CHB患者,随机分治疗组及对照组各45例,对照组除一般保肝、对症治疗外,加用拉米夫定抗病毒治疗,疗程6个月。治疗组在对照组用药基础上,按阴阳辨证法则分类组方治疗。口苦、便干、尿黄、苔黄腻、舌尖红、脉弦数或滑数均为有热属阳,用肝炎I号方治疗(茵陈,栀子,滑石,公英,二花,连翘,贯众,虎杖,柴胡,赤芍,郁金,当归,川芎,枳壳,甘草),无阳热征象即按阴湿类用肝炎II号方治疗(党参,白术,茯芩,黄芪,仙灵脾,山药,熟地,山萸肉,柴胡,升麻,干姜,甘草,虎杖),疗程与对照组相同,前3个月每天1剂,后3个月隔日1剂,水煎2次取汁400ml,分早晚服。疗程结束时,观察两组患者肝功能、乙肝病毒标志物及HBVDNA的变化。结果:治疗组与对照组患者血清谷丙转氨酶(ALT)正常率分别为91%与75.5%,两组相比,差异有显著性(P<0.05);HBeAg、HBVDNA阴转率分别为29%、14%及31%、21%,两组相比差异有显著性(P<0.01或P<0.05);未见明显不良反应。结论:按阴阳辨证分类组方联合拉米夫定治疗CHB有改善肝功能和抑制乙肝病毒复制的功效,且辨证指标明确,易于在临床推广。  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