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   6243篇
  免费   140篇
  国内免费   2篇
电工技术   68篇
综合类   3篇
化学工业   802篇
金属工艺   117篇
机械仪表   122篇
建筑科学   180篇
矿业工程   11篇
能源动力   100篇
轻工业   528篇
水利工程   41篇
石油天然气   20篇
无线电   653篇
一般工业技术   792篇
冶金工业   2382篇
原子能技术   64篇
自动化技术   502篇
  2021年   40篇
  2020年   45篇
  2019年   50篇
  2018年   56篇
  2017年   61篇
  2016年   76篇
  2015年   49篇
  2014年   63篇
  2013年   248篇
  2012年   108篇
  2011年   171篇
  2010年   122篇
  2009年   133篇
  2008年   158篇
  2007年   150篇
  2006年   136篇
  2005年   120篇
  2004年   156篇
  2003年   146篇
  2002年   125篇
  2001年   126篇
  2000年   113篇
  1999年   171篇
  1998年   668篇
  1997年   412篇
  1996年   280篇
  1995年   189篇
  1994年   197篇
  1993年   197篇
  1992年   98篇
  1991年   94篇
  1990年   100篇
  1989年   83篇
  1988年   76篇
  1987年   84篇
  1986年   78篇
  1985年   84篇
  1984年   65篇
  1983年   75篇
  1982年   75篇
  1981年   73篇
  1980年   60篇
  1979年   55篇
  1978年   55篇
  1977年   108篇
  1976年   185篇
  1975年   50篇
  1974年   42篇
  1973年   36篇
  1970年   25篇
排序方式: 共有6385条查询结果,搜索用时 546 毫秒
91.
Acute graft rejection and delayed function are considered to be the major risk factors of short-term as well as long-term graft survival. We studied the impact of these factors on graft outcome among 109 renal transplant recipients. All recipients were treated with triple drug protocol. The recipients were divided into two groups: I group included 57 patients with delayed graft function (DGF), II group included 52 patients with immediate graft function (IGF). We studied graft survival, incidence of acute rejection, serum creatinine levels and the cause of graft loss for patients in both groups. Acute rejection episodes occurred in 49% of patients from DGF group and 45% of patients from IGF group. Graft survival in IGF group was better than in DGF group. Actuarial graft survival at 1, 2, 3 and 4 years in examined groups was 84%, 82%, 72%, 65% vs. 92%, 86%, 84%, 84%, respectively. One-year graft survival in patients with acute rejection from DGF group and IGF group was significantly lower than in patients who remained rejection free (69%, 74% vs. 94%, 96%). We concluded that delayed graft function decreases long-term graft survival, while immediate graft function has an excellent impact on graft outcome. Acute graft rejection is the strongest risk factor of graft loss.  相似文献   
92.
Oxidation protection for carbon fibre composites   总被引:7,自引:0,他引:7  
Carbon fibre-reinforced ceramic matrix composites are promising candidate materials for high-temperature structural applications such as gas turbine blades. In oxidizing environments at temperatures above 400°C, however, carbon fibres are rapidly oxidized. There is, therefore, a need to coat the composite in order to protect it against oxidation. This review identifies the requirements of an effective oxidation protection system for carbon fibre-reinforced ceramics and summarizes the work which has been carried out towards this goal over the last 50 years. The most promising coatings are those composed of several ceramic layers designed to protect against erosion, spallation and corrosion, in addition to possessing a self-healing capability by the formation of glassy phases on exposure to oxygen.  相似文献   
93.
94.
This paper describes a fixed-weight Hamming binary neural classifier chip suitable for applications where high-speed operation is required. The circuit uses switched current-mode techniques throughout and achieves classification in one forward pass through the network. The chip was realized in 2.4-μm n-well CMOS technology and was designed to recognize the integers 0-9. It achieved a classification rate of 10 MHz without any observable tendency to misclassification or instability  相似文献   
95.
The rate of nosocomial respiratory syncytial virus (RSV) infection was measured in a large pediatric hospital using an incidence density method. The at-risk days for nosocomial RSV were summed during a defined winter period in which there were 54 admissions with community-acquired RSV infection giving a rate of 2.9 cases per 1,000 at-risk days (95% confidence interval, 0.3-5.4 per 1,000).  相似文献   
96.
This 533-MHz BiCMOS very large scale integration (VLSI) implementation of the PowerPC architecture contains three pipelines and a large on-chip secondary cache to achieve a peak performance of 1600 MIPS. The 15 mm×10 mm die contains 2.7 M transistors (2M CMOS and 0.7 M bipolar) and dissipates less than 85 W. The die is fabricated in a six-level metal, 0.5-μm BiCMOS process and requires 3.6 and 2.1 V power supplies  相似文献   
97.
98.
99.
100.
Mechanisms for the abnormal copper (Cu) accumulation in the liver of LEC rats were examined using primary cultured liver parenchymal cells prepared from mutant LEC rats and those from control LEA rats (original strain). The Cu and metallothionein (MT) mRNA levels in the liver of LEC rats were caused to decrease to the same levels as those of LEA rats by removing Cu in vivo selectively with tetrathiomolybdate. Cu was taken up by LEC rat cells to the same extent as LEA rat cells by exposure to low medium Cu and to a higher extent by exposure to high medium Cu, while the MT mRNA level in LEC rat cells increased dose-dependently at a much higher rate than that in LEA rats. MT mRNA levels in both cells were comparable by exposure to cadmium, zinc and dexamethasone. The results indicate that expression of MT mRNA is selectively enhanced by Cu in LEC cells despite the fact that uptake of Cu is comparable with normal cells.  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