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   1449篇
  免费   12篇
化学工业   110篇
金属工艺   8篇
机械仪表   13篇
建筑科学   15篇
矿业工程   4篇
能源动力   6篇
轻工业   33篇
水利工程   14篇
无线电   52篇
一般工业技术   56篇
冶金工业   1095篇
原子能技术   4篇
自动化技术   51篇
  2021年   3篇
  2019年   3篇
  2018年   6篇
  2016年   4篇
  2014年   7篇
  2013年   24篇
  2012年   12篇
  2011年   16篇
  2010年   10篇
  2009年   12篇
  2008年   13篇
  2007年   20篇
  2006年   13篇
  2005年   15篇
  2004年   15篇
  2003年   14篇
  2002年   12篇
  2001年   7篇
  2000年   12篇
  1999年   34篇
  1998年   299篇
  1997年   159篇
  1996年   141篇
  1995年   78篇
  1994年   53篇
  1993年   67篇
  1992年   21篇
  1991年   27篇
  1990年   29篇
  1989年   26篇
  1988年   17篇
  1987年   21篇
  1986年   20篇
  1985年   28篇
  1984年   20篇
  1983年   6篇
  1982年   11篇
  1981年   11篇
  1980年   13篇
  1979年   9篇
  1978年   14篇
  1977年   32篇
  1976年   57篇
  1975年   11篇
  1974年   8篇
  1973年   3篇
  1971年   3篇
  1970年   4篇
  1962年   2篇
  1959年   2篇
排序方式: 共有1461条查询结果,搜索用时 306 毫秒
211.
Arterial hypertension in rural societies   总被引:1,自引:0,他引:1  
  相似文献   
212.
213.
The flavonol glycosides, quercetin-3-glucoglucoside and kaempferol-3-rhamnoglucoside, have been separated from crushed, delinted cottonseed (kernel and hull) by extensive use of paper chromatography, ultraviolet spectrophotometry, and qualitative and quantitative analysis of their hydrolysis products. Details of the separation and identification are described. Aided by a Fellowship from the National Medical Fellowship Inc. through funds appropriated by the National Foundation for Infantile Paralysis.  相似文献   
214.
215.
Using a new rating system (Innsbruck Knee-Sports Rating Scale) 75 patients 5 to 6 years after ACL-injury have been compared to their sports activity (47 patients with ACL reconstruction and 28 conservative treated patients). Under the viewpoint of knee load and especially the demand on stability sports activities have been divided into 3 categories: High Risk, Low Risk and Non Risk Pivoting Sports. Operative therapy shows an advantage in High Risk Pivoting sports (e.g. soccer, basketball) and in Low Risk Pivoting (e.g. running, hiking) sports, expressed by fewer knee related symptoms and higher participation levels. In the Non Risk Pivoting category (e.g. swimming, cycling) good results could also be achieved by conservative therapy. The careful evaluation of each patient's sports activities is therefore an important factor in the decision for the right therapy on one hand, and for comparing the results of different therapy programs or patient collectives on the other.  相似文献   
216.
Reading impaired first graders were given daily tutoring as a "first cut" diagnostic to aid in distinguishing between reading difficulties caused by basic cognitive deficits and those caused by experiential deficits. Reading achievement in most of these children was found to be within or above the average range after one semester of remediation. Children who were difficult to remediate performed below both children who were readily remediated and normal readers on kindergarten and first-grade tests evaluating phonological skills, but not on tests evaluating visual, semantic and syntactic skills. The results are consistent with convergent findings from previous research suggesting that reading problems in some poor readers may be caused primarily by phonological deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
217.
218.
219.
BACKGROUND: Patients who have inducible ischemia after acute myocardial infarction (AMI) generally undergo coronary angiography with the intent to revascularize. Whether this approach is superior to intensive treatment with anti-ischemic medications is unknown. METHODS AND RESULTS: We performed a prospective, randomized pilot study comparing intensive medical therapy with coronary angioplasty (PTCA) for suppression of myocardial ischemia in 44 stable survivors of AMI. Myocardial ischemia was quantified with adenosine 201Tl tomography (SPECT) performed 4.5+/-2.9 days after AMI. All patients at baseline had a large total (>/=20%) and ischemic (>/=10%) left ventricular perfusion defect size (PDS). SPECT was repeated at 43+/-26 days after therapy was optimized. The total stress-induced PDS was comparably reduced with medical therapy (from 38+/-13% to 26+/-16%; P<0.0001) and PTCA (from 35+/-12% to 20+/-16%; P<0.0001). The reduction in ischemic PDS was also similar (P=NS) in both groups. Cardiac events occurred in 7 of 44 patients over 12+/-5 months. Patients who remained clinically stable had a greater reduction in ischemic PDS (-13+/-9%) than those who had a recurrent cardiac event (-5+/-7%; P<0.02). Event-free survival was superior in the 24 patients who had a significant (>/=9%) reduction in PDS (96%) compared with those who did not (65%; P=0.009). CONCLUSIONS: In this small pilot study, intensive medical therapy and PTCA were comparable at suppressing ischemia in stable patients after AMI. Sequential imaging with adenosine SPECT can track changes in PDS after anti-ischemic therapies and thereby predict subsequent outcome. Corroboration of these preliminary findings in a larger cardiac-event trial is warranted.  相似文献   
220.
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