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   1232篇
  免费   14篇
  国内免费   10篇
综合类   5篇
化学工业   25篇
金属工艺   10篇
机械仪表   7篇
建筑科学   11篇
矿业工程   2篇
能源动力   4篇
轻工业   12篇
石油天然气   8篇
无线电   13篇
一般工业技术   7篇
冶金工业   1129篇
原子能技术   7篇
自动化技术   16篇
  2022年   3篇
  2021年   2篇
  2020年   4篇
  2017年   2篇
  2016年   1篇
  2015年   6篇
  2014年   3篇
  2013年   4篇
  2012年   14篇
  2011年   11篇
  2010年   15篇
  2009年   8篇
  2008年   5篇
  2007年   10篇
  2006年   5篇
  2005年   9篇
  2004年   2篇
  2003年   5篇
  2002年   8篇
  2001年   7篇
  2000年   1篇
  1999年   31篇
  1998年   312篇
  1997年   208篇
  1996年   130篇
  1995年   65篇
  1994年   71篇
  1993年   73篇
  1992年   9篇
  1991年   13篇
  1990年   13篇
  1989年   7篇
  1988年   17篇
  1987年   12篇
  1986年   10篇
  1985年   8篇
  1983年   3篇
  1982年   3篇
  1981年   17篇
  1980年   19篇
  1979年   1篇
  1978年   4篇
  1977年   30篇
  1976年   70篇
  1975年   1篇
  1955年   4篇
排序方式: 共有1256条查询结果,搜索用时 15 毫秒
21.
22.
CI-994 (acetyldinaline) is an orally active anticancer drug currently in Phase 1 clinical trials. To assess its preclinical toxicity, CI-994 was administered orally as suspensions to Wistar rats (10/sex/dose) and in capsules to beagle dogs (3/sex/dose) once daily for two weeks. Doses were 1.5, 5, and 15 mg/kg for rats (9, 30, and 90 mg/m2, respectively), and 0.5, 2, and 5 mg/kg for dogs (10, 40, and 100 mg/m2, respectively). Systemic exposure was dose-proportional based on toxicokinetic analysis in dogs. Severe clinical signs and mortality occurred at the highest dose in both species beginning on Day 10. Neutropenia, lymphocytopenia, thrombocytopenia, lymphoid depletion, bone marrow hypocellularity, and testicular degeneration were observed in both species, primarily at the mid- and high-doses. Despite continued treatment, neutrophil counts in dogs returned to control levels in Week 2. Other microscopic findings in rats included splenic hematopoietic depletion at all doses and epithelial cell necrosis in various tissues at 15 mg/kg. Additional bone marrow changes in dogs involved myeloid and megakaryocyte hyperplasia at 2 mg/kg and abnormal myeloid and megakaryocyte maturation at 2 and 5 mg/kg. Except for the testicular effects in both species, all changes were reversible within a 4-week (rat) or 9-week (dog) recovery period. The results of these studies show that target organ effects of CI-994 principally involve tissues with rapidly dividing cell populations and that bone marrow suppression is the dose-limiting toxicity. CI-994 also seems to interfere with the release and/or maturation of cells in the bone marrow.  相似文献   
23.
24.
A simple commercially available compression device allowed intermittent ultrasound scanning of the compression site during compression repair of a femoral artery pseudoaneurysm in six patients. All six of the pseudoaneurysms (five superficial femoral and one common femoral) were compressed without compression of the underlying vessels. The procedure was successful in four of the six patients, without complications. Use of this device may decrease operator fatigue during compression repair of pseudoaneurysm.  相似文献   
25.
Hemodynamics and left ventricular myocardial contractility in 170 patients who underwent surgery of prostatic adenoma were examined in preoperative period and 16 days after single-stage transvesical adenomectomy. The age of the patients varied from 52 to 85 years. Echocardiography and the dilution method were used for the evaluation. The increase of end-diastolic and end-systolic volumes, stroke volume, cardiac index, was registered. The combined pharmacological treatment made it possible to decrease the number of operative and postoperative cardiovascular complications.  相似文献   
26.
27.
28.
29.
Deletion of PHR1, a pH-regulated gene of Candida albicans, results in pH-conditional defects in growth, morphogenesis, and virulence evident at neutral to alkaline pH but absent at acidic pH. Consequently, we searched for a functional homolog of PHR1 active at low pH. This resulted in the isolation of a second pH-regulated gene, designated PHR2. The expression of PHR2 was inversely related to that of PHR1, being repressed at pH values above 6 and progressively induced at more acidic pH values. The predicted amino acid sequence of the PHR2 protein, Phr2p, was 54% identical to that of Phr1p. A PHR2 null mutant exhibited pH-conditional defects in growth and morphogenesis analogous to those of PHR1 mutants but manifest at acid rather than alkaline pH values. Engineered expression of PHR1 at acid pH in a PHR2 mutant strain and PHR2 at alkaline pH in a PHR1 mutant strain complemented the defects in the opposing mutant. Deletion of both PHR1 and PHR2 resulted in a strain with pH-independent, constitutive growth and morphological defects. These results indicate that PHR1 and PHR2 represent a novel pH-balanced system of functional homologs required for C. albicans to adapt to environments of diverse pH.  相似文献   
30.
The primary purpose of this investigation was to compare tissue fixation security by simple sutures versus mattress sutures in transosseous rotator cuff repair. These two repair techniques were each performed in 17 human cadaver shoulders, with two bone tunnels being used for the repair by two simple sutures and two other bone tunnels being used for the repair by one mattress suture. The repairs were loaded to failure in a servohydraulic materials test system. Rotator cuff repair by simple sutures was found to be significantly stronger than repair by mattress sutures (P = .0007). The average ultimate load to failure for the simple suture construct (189.62 N) was 39.72% greater than that for the mattress suture construct (135.71 N). Most of the failures occurred by suture breakage at the knot. Load-sharing by multiple suture tails and multiple knots in the simple suture configuration likely contributed to its superior strength characteristics compared with the mattress suture configuration.  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