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   1410075篇
  免费   115890篇
  国内免费   3332篇
耳鼻咽喉   18380篇
儿科学   46648篇
妇产科学   41099篇
基础医学   200993篇
口腔科学   37722篇
临床医学   126196篇
内科学   284666篇
皮肤病学   33375篇
神经病学   117014篇
特种医学   53854篇
外国民族医学   464篇
外科学   210648篇
综合类   32784篇
现状与发展   3篇
一般理论   496篇
预防医学   110259篇
眼科学   31535篇
药学   98638篇
  1篇
中国医学   3349篇
肿瘤学   81173篇
  2021年   10882篇
  2019年   11700篇
  2018年   16593篇
  2017年   12697篇
  2016年   14290篇
  2015年   16027篇
  2014年   22595篇
  2013年   33448篇
  2012年   45468篇
  2011年   47990篇
  2010年   28203篇
  2009年   27105篇
  2008年   44399篇
  2007年   46907篇
  2006年   47455篇
  2005年   45936篇
  2004年   43827篇
  2003年   41741篇
  2002年   40253篇
  2001年   73034篇
  2000年   74568篇
  1999年   61580篇
  1998年   17011篇
  1997年   15448篇
  1996年   15592篇
  1995年   14799篇
  1994年   13410篇
  1993年   12592篇
  1992年   45861篇
  1991年   43503篇
  1990年   41503篇
  1989年   39573篇
  1988年   36208篇
  1987年   35372篇
  1986年   32873篇
  1985年   31303篇
  1984年   23848篇
  1983年   20050篇
  1982年   12221篇
  1981年   10799篇
  1979年   20719篇
  1978年   14597篇
  1977年   12100篇
  1976年   11377篇
  1975年   11633篇
  1974年   14004篇
  1973年   13550篇
  1972年   12652篇
  1971年   11480篇
  1970年   10924篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Bulletin of Environmental Contamination and Toxicology - Elevated metal concentrations occur throughout the coastal zone due to urbanization and various anthropogenic activities. The lethal...  相似文献   
982.
983.
BACKGROUND: The recent amalgamation of data by users of the Perinatal Problem Identification Programme (PPIP) throughout South Africa has culminated in the publication of the Saving Babies report. OBJECTIVES: To determine the absolute rate of death from intrapartum-related birth asphyxia, and the contribution of intrapartum-related asphyxia to total perinatal mortality in South African hospitals, and to identify the primary obstetric causes and avoidable factors for these deaths. METHODS: The amalgamated PPIP data for the year 2000 were obtained from 27 state hospitals (6 metropolitan, 12 town and 9 rural) in South Africa. In PPIP-based audit, all perinatal deaths are assigned primary obstetric causes and avoidable factors, and these elements were obtained for all deaths resulting from intrapartum-related birth asphyxia. RESULTS: There were 123,508 births in the hospitals surveyed, with 4,142 perinatal deaths among infants > or = 1,000 g, giving a perinatal mortality rate of 33.5/1,000 births. The perinatal mortality rate from intrapartum-related birth asphyxia was 4.8/1,000 births. The most frequent avoidable factors were delay by mothers in seeking attention during labour (36.6%), signs of fetal distress interpreted incorrectly (24.9%), inadequate fetal monitoring (18.0%) and no response to poor progress in labour (7.0%). The perinatal mortality rates for metropolitan, town, and rural areas were 30.0, 39.4 and 30.9/1,000 births respectively. The contribution of intrapartum-related birth asphyxia to perinatal mortality in these areas was 10.8%, 16.7% and 26.4% respectively. CONCLUSION: The high rates of perinatal death from intrapartum-related birth asphyxia in South Africa are typical of those in underdeveloped countries, with the most serious deficiencies in rural areas. Most of these deaths are avoidable and the reduction of these rates presents an important challenge to providers of perinatal care in this country. Areas worthy of research and action include provision of mothers' waiting facilities in rural regions, improvements in fetal monitoring, partogram-based labour management, and the establishment of midwifery staffing norms for South African labour units.  相似文献   
984.
Mammalian fatty acid synthase (FASE) overexpression has been shown in a number of human malignancies including colonic adenocarcinoma. Since FASE synthesizes only saturated fatty acids, we hypothesized that cancer cells have a greater proportion of long-chain saturated fatty acids. We studied and found an unequivocal increase in saturated C18 fatty acid (stearic acid) in colonic adenocarcinoma compared to adjacent normal colonic mucosa. The increase is even more striking when measured as a ratio of stearic acid to the unsaturated C18 fatty acids (oleic acid and linoleic acid). This change in fatty acid composition of the cancer cells should significantly alter their physical and biological properties. The increase in relative proportion of saturated fatty acids should make the cancer cells more susceptible to cryodamage and measurement of fatty acid composition of cancer cells may help individualize the temperature for cryotherapy. Also, the lipid alterations may affect the structure and functions of lipid rafts, which may enable the cancer cells to affect signaling mechanisms such as those involved in cell growth and apoptosis. Dietary or therapeutic interventions targeting lipid rafts may thus be an option for cancer treatment.  相似文献   
985.
986.
Résumé: La rémission du cancer peut être l’occasion pour certains patients d’une réelle détresse émotionnelle ainsi que d’une désadaptation psychologique appelées: syndrome de Lazare. Nous émettons trois hypothèses explicatives quant à la survenue de tels troubles. La première confronte l’issue du cancer aux concepts psychanalytiques de dette et de masochisme. La deuxième envisage les symptômes sous l’angle d’une réaction de sevrage. Et la dernière évoque le contrecoup traumatique des traitements.Dossier: «Cliniques du cancer»  相似文献   
987.
988.
989.
Static analysis with finite element of a realistic femur nail bone-implant system in a typical proximal femoral fracture under physiological load bearing situations provides results for stress, displacement and strain. The question to be answered is, if simulation with the finite element analysis is able to explain biomechanically clinical observed patterns of failure. Surface-Reconstruction with CT database of a proximal femur and reconstruction with CT based density data was done. Next steps were to unite the bone structure with the Proximal Femoral Nail and to model two relevant fractures (31-A2.2 and A2.3 according AO). After modelling of geometry, isotropic material behaviour and load application numeric calculation of the femur-nail system with FE-software was performed. FE simulation mainly shows an axial dislocation of the femoral head screw with nearly no dislocation of the antirotation screw. This so-called z-effect therefore means: (1) Tilting of the proximal main fragment around the sagittal axis between the screws and (2) relative movement of both screws in the frontal plane. Relative movement of the two screws against each other could be the reason for implant failure, the so called cut out. Furthermore simulation shows different gliding of the screws explaining the so called z-telescoping. The analyzed stress patterns have to be relativized, because isotropic material behaviour of cancellous bone was assumed. Further examinations for this issue are necessary.  相似文献   
990.
OBJECTIVE: To determine the safety and the long-term results of primary stent placement for localized distal aortic occlusive disease. DESIGN: Retrospective observational study. PATIENTS AND METHODS: From July 1998 to July 2005 17 patients (14 female and 3 men, mean age 57 years (39-80)) were treated for intermittent claudication. Five of these patients underwent additional endovascular treatment of focal iliac lesions. RESULTS: Technical success defined as residual stenosis of less than 50% or a trans-stenotic systolic pressure gradient <10% was achieved in 14 of 17 (82%) patients. Major complications included dissection at the puncture site in one patient and thrombosis of additional iliac stents in another patient. Both of these complications were successfully treated. During a mean follow-up of 27 months (range 1-86), four patients had recurrence of symptoms due to in-stent restenoses (n=2), femoral (n=1) or iliac occlusion (n=1), respectively. By Kaplan-Meier analysis, primary aortic hemodynamic patency was 83% at 3 years. Secondary aortic hemodynamic patency was 100%. The primary clinical patency was 68% at 3 years. CONCLUSION: Primary stent placement for distal aortic stenoses is an alternative to surgical treatment because of its high patency and relatively low complication rates.  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