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   5515篇
  免费   96篇
  国内免费   24篇
电工技术   297篇
综合类   8篇
化学工业   1087篇
金属工艺   162篇
机械仪表   108篇
建筑科学   90篇
矿业工程   2篇
能源动力   109篇
轻工业   311篇
水利工程   9篇
石油天然气   20篇
无线电   570篇
一般工业技术   1050篇
冶金工业   1289篇
原子能技术   181篇
自动化技术   342篇
  2023年   27篇
  2022年   57篇
  2021年   107篇
  2020年   44篇
  2019年   58篇
  2018年   62篇
  2017年   61篇
  2016年   81篇
  2015年   58篇
  2014年   89篇
  2013年   194篇
  2012年   169篇
  2011年   241篇
  2010年   163篇
  2009年   166篇
  2008年   179篇
  2007年   192篇
  2006年   163篇
  2005年   176篇
  2004年   146篇
  2003年   148篇
  2002年   111篇
  2001年   120篇
  2000年   116篇
  1999年   141篇
  1998年   542篇
  1997年   299篇
  1996年   224篇
  1995年   168篇
  1994年   134篇
  1993年   122篇
  1992年   87篇
  1991年   81篇
  1990年   63篇
  1989年   73篇
  1988年   54篇
  1987年   59篇
  1986年   64篇
  1985年   61篇
  1984年   64篇
  1983年   42篇
  1982年   50篇
  1981年   49篇
  1980年   45篇
  1979年   42篇
  1978年   34篇
  1977年   35篇
  1976年   79篇
  1975年   17篇
  1974年   16篇
排序方式: 共有5635条查询结果,搜索用时 15 毫秒
131.
The pulse responses of magnetically coupled pulse transformers of arbitrary turn ratio n:1 are considered in the framework of a distributed parameter theory. Equivalent circuits for the calculation of pulse risetime and flat-top responses are introduced for inverting- and noninverting-type transformers, respectively. With these equivalent circuits, the pulse risetime responses are calculated more precisely than with the lumped-parameter circuit theory. Measured responses of pulse transformers agree well with the theoretical predictions  相似文献   
132.
The effects of molybdenum, phosphorus and of microstructure on creep were studied at 550°C utilizing the model alloys Fe—3 Cr—0.05P, Fe—3 Cr—1 Mo—0.05P and Fe—3 Cr—1 Mo. The heat treatments were varied to obtain a ferritic or bainitic structure, the effect of a preheat treatment of 300 h at 550°C was investigated. Both Mo and P increase the creep strength by different mechanisms which lead to four types of creep curves, with 1 to 3 minima. The results are discussed using microstructural information from transmission electron-microscopy.  相似文献   
133.
This paper presents a novel parallel processing system for image synthesis using ray tracing. An object space is divided into parts (subspaces), each of which is allocated to a processor. The processor detects, simultaneously the intersections of the surfaces of each object and a fixed number of rays over the whole space, and calculates the local intensity on an object in each subspace. The global intensities of pixels on a screen are calculated by the other kind of processors simultaneously. We also present the optimal data structure, based on an adaptive division algorithm, for parallel processing of the object space.  相似文献   
134.
135.
The tetragonal-to-monoclinic phase transformation of yttria partially stabilized zirconia by low temperature annealing in air was investigated in the temperature range 100 to 650° C using a sintered body of zirconia containing 2 to 4 mol% Y2O3. The amount of monoclinic phase formed was maximum at about 200° C. Both the decrease in grain size and increase in the yttria concentration were effective in decreasing the critical temperature below which the monoclinic phase was formed. The relationship between the critical temperature (T c) and the grain size was experimentally determined.  相似文献   
136.
Intracarotid injection of a low dosage of amobarbital (75 mg, 5% solution) was studied in 30 temporal lobectomy candidates while naming achromatic, incongruously, and congruously colored pictorial objects and reading real, nonsense, and embedded words. Semantic errors and phonological alexia followed the left injection, while the right injection induced visuoperceptual errors. When the contralateral hemisphere was anesthetized, the left brain formulated supraordinate categories for words and objects, while the right brain applied concrete labels. The basic language proficiency of patients influenced recovery and outcome; left temporal patients who were interictally anomic performed especially poorly after both injections. Codifying phonological and perceptual changes during the intracarotid amobarbital procedure can improve interpretations about language laterality and organization.  相似文献   
137.
138.
139.
140.
Degradation mechanism of H2 permselectivity under atmosphere of steam/N2 = 3 at 773 K was investigated among amorphous silica membranes on γ-Al2O3-coated α-Al2O3 or Ni-doped γ-Al2O3-coated α-Al2O3 synthesized by counter diffusion chemical vapor deposition. Helium and H2 permeance drastically decreased during the first few hours of hydrothermal exposure. On the other hand, N2 permeance fluctuated during hydrothermal treatment in silica membrane on γ-Al2O3-coated α-Al2O3. The degree of N2 permeance change depended on the hydrothermal stability of the intermediate layer. Hydrogen permselectivity was affected by both the densification of amorphous silica and the sintering of the intermediate layer during hydrothermal exposure.  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