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   1324865篇
  免费   103412篇
  国内免费   2174篇
耳鼻咽喉   19028篇
儿科学   45653篇
妇产科学   35966篇
基础医学   188246篇
口腔科学   34444篇
临床医学   115861篇
内科学   267472篇
皮肤病学   28660篇
神经病学   105187篇
特种医学   52865篇
外国民族医学   664篇
外科学   204815篇
综合类   27760篇
现状与发展   2篇
一般理论   440篇
预防医学   99990篇
眼科学   28905篇
药学   97727篇
  2篇
中国医学   2479篇
肿瘤学   74285篇
  2019年   9905篇
  2018年   14142篇
  2017年   10653篇
  2016年   11674篇
  2015年   13248篇
  2014年   18596篇
  2013年   28379篇
  2012年   39144篇
  2011年   41468篇
  2010年   24724篇
  2009年   23605篇
  2008年   39750篇
  2007年   42493篇
  2006年   42692篇
  2005年   41740篇
  2004年   40880篇
  2003年   39420篇
  2002年   38726篇
  2001年   64395篇
  2000年   66802篇
  1999年   56903篇
  1998年   15801篇
  1997年   14326篇
  1996年   14704篇
  1995年   13941篇
  1994年   13201篇
  1993年   12171篇
  1992年   44854篇
  1991年   43780篇
  1990年   42471篇
  1989年   40354篇
  1988年   37110篇
  1987年   36458篇
  1986年   33817篇
  1985年   32515篇
  1984年   24535篇
  1983年   20549篇
  1982年   12130篇
  1981年   11086篇
  1979年   21517篇
  1978年   15047篇
  1977年   12741篇
  1976年   11861篇
  1975年   12792篇
  1974年   14855篇
  1973年   14255篇
  1972年   13081篇
  1971年   11842篇
  1970年   11133篇
  1969年   10092篇
排序方式: 共有10000条查询结果,搜索用时 76 毫秒
81.
Background: Breast cancer is a multifactorial disease that affects women worldwide. Its progression is likely to be executed by oxidative stress wherein elevated levels of reactive oxygen and nitrogen species drive several breast cancer pathologies. Spider venom contains various pharmacological peptides which exhibit selective activity to abnormal expression of ion channels on cancer cell surface which can confer potent anti-cancer activities against this disease. Methods: Venom was extracted from a Philippine tarantula by electrostimulation and fractionated by reverse phase-high performance liquid chromatography (RP-HPLC). Venom fractions were collected and used for in vitro analyses such as cellular toxicity, morphological assessment, and oxidative stress levels. Results: The fractionation of crude spider venom generated several peaks which were predominantly detected spectrophotometrically and colorimetrically as peptides. Treatment of MCF-7 cell line of selected spider venom peptides induced production of several endogenous radicals such as hydroxyl radicals (•OH), nitric oxide radicals (•NO), superoxide anion radicals (•O2−) and lipid peroxides via malondialdehyde (MDA) reaction, which is comparable with the scavenging effects afforded by 400 µg/mL vitamin E and L-cysteine (p<0.05). Concomitantly, the free radicals produced decrease the mitochondrial membrane potential and metabolic activity as detected by rhodamine 123 and tetrazolium dye respectively (p>0.05). This is manifested by cytotoxicity in MCF-7 cells as seen by increase in membrane blebbing, cellular detachment, caspase activity and nuclear fragmentation. Conclusion: These data suggest that the Philippine tarantula venom contains peptide constituents exhibiting pro-oxidative and nitrosative-dependent cytotoxic activities against MCF-7 cells and can indicate mechanistic insights to further explore its potential application as prooxidants in cancer therapy.  相似文献   
82.
Jahn  P. 《Der Onkologe》2020,26(11):1040-1046
Die Onkologie - Die Pflegepersonaluntergrenzen als rote Linien zur Abgrenzung einer gefährlichen Pflegepraxis sind nicht geeignet, die dringend benötigte Trendwende einzuleiten und...  相似文献   
83.
84.
85.
86.
87.
88.

Background

Arterial vascular anomalies in patients undergoing kidney transplantation (KT) are correlated with a higher incidence of early surgical complications, potentially causing graft loss. Arterial reconstruction allows patients to overcome these surgical challenges, thus minimizing the risk of poor outcomes. The aim of the present study is to retrospectively investigate the safety and effectiveness of the multiple arterial reconstruction technique with a Teflon patch in case of an unavailable aortic patch: to do so, surgical complications, graft function, and patient survival were evaluated.

Methods

During the period January 2009 to August 2016, 202 adult deceased-donor KTs were performed at our center. Group A (n = 27; reconstruction of multiple arteries) and Group B (n = 175; control group) were compared.

Results

No differences were observed between the 2 groups in terms of early postoperative course, with no vascular complication observed in Group A. No vascular patch infections were reported, nor longer cold ischemia time rates. Similarly, long-term survival rates were similar between the 2 groups.

Conclusions

The Teflon-patch arterial reconstruction technique appears to be safe and effective, with an acceptable balance of benefits and potential risks of using a prosthetic material. Studies based on larger series are needed to further validate this approach.  相似文献   
89.

Objective

Arch obstruction after the Norwood procedure is common and contributes to mortality. We determined the prevalence, associated factors, and practice variability of arch reintervention and assessed whether arch reintervention is associated with mortality.

Methods

From 2005 to 2017, 593 neonates in the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort underwent a Norwood procedure. Median follow-up was 3.7 years. Multivariable parametric models, including a modulated renewal analysis, were performed.

Results

Of the 593 neonates, 146 (25%) underwent 218 reinterventions for arch obstruction after the Norwood procedure: catheter-based (n = 168) or surgical (n = 50) at a median age of 4.3 months (quartile 1-quartile 3, 2.6-5.7). Interdigitation of the distal aortic anastomosis was protective against arch reintervention. Development of ≥ moderate tricuspid valve regurgitation and right ventricular dysfunction at any point was associated with arch reintervention. Nonsignificant variables for arch reintervention included shunt type and preoperative aortic measurements. Surgical arch reintervention was protective against arch reintervention, but transcatheter reintervention was associated with increased reintervention. Arch reintervention was not associated with increased mortality. There was wide institutional variation in incidence of arch reintervention (range, 0-40 reinterventions per 100 years patient follow-up) and in preintervention gradient (range, 0-64 mm Hg).

Conclusions

Interdigitation of the distal aortic anastomosis during the Norwood procedure decreased the risk of arch reintervention. Surgical arch reintervention is more definitive than transcatheter. Arch reintervention after the Norwood procedure is not associated with increased mortality. Serial surveillance for arch obstruction, integrated with changes in right ventricular function and tricuspid valve regurgitation, is recommended after the Norwood procedure to improve outcomes.  相似文献   
90.
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