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   734677篇
  免费   9359篇
  国内免费   2365篇
电工技术   13598篇
综合类   623篇
化学工业   110726篇
金属工艺   27386篇
机械仪表   22702篇
建筑科学   18000篇
矿业工程   2890篇
能源动力   20218篇
轻工业   63357篇
水利工程   6772篇
石油天然气   9390篇
武器工业   30篇
无线电   91218篇
一般工业技术   142249篇
冶金工业   138232篇
原子能技术   13472篇
自动化技术   65538篇
  2021年   5977篇
  2020年   4412篇
  2019年   5686篇
  2018年   9364篇
  2017年   9439篇
  2016年   10157篇
  2015年   7050篇
  2014年   11485篇
  2013年   35513篇
  2012年   19145篇
  2011年   26592篇
  2010年   20783篇
  2009年   23651篇
  2008年   24629篇
  2007年   24644篇
  2006年   22143篇
  2005年   20079篇
  2004年   19376篇
  2003年   19034篇
  2002年   18276篇
  2001年   18152篇
  2000年   16996篇
  1999年   17930篇
  1998年   43254篇
  1997年   30848篇
  1996年   23988篇
  1995年   18318篇
  1994年   16313篇
  1993年   16025篇
  1992年   11782篇
  1991年   11174篇
  1990年   10866篇
  1989年   10324篇
  1988年   9927篇
  1987年   8549篇
  1986年   8419篇
  1985年   9899篇
  1984年   9210篇
  1983年   8133篇
  1982年   7539篇
  1981年   7587篇
  1980年   7088篇
  1979年   6883篇
  1978年   6618篇
  1977年   7795篇
  1976年   10353篇
  1975年   5613篇
  1974年   5340篇
  1973年   5295篇
  1972年   4362篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
Malignant bone pain: pathophysiology and treatment   总被引:1,自引:0,他引:1  
2-acetyl aminofluorene (AAF) reacts in acidic conditions with nitrous fume yielding N-nitroso-AAF (N-NO-AAF), as previously described, that exerts more toxic and mutagenic effects than its parental compound. In this study, the effect of sodium nitrite (NaNO2) on the tumorigenicity of AAF in rats fed with AAF and NaNO2 was observed. Wistar rats were divided into five groups: group I served as control; group II were treated with NaNO2 (0.3%); group III was given 0.02% AAF alone; groups IV and V received both AAF and NaNO2 (0.2 and 0.3% respectively) in their diet for 12 weeks. At the end of the experiment, all rats in groups III, IV and V developed early stage phenomena of hepatocellular carcinoma, including hepatomegaly with variable-sized foci and neoplastic nodules. Severe damage was observed in the rats treated with AAF and NaNO2. Feeding of AAF (0.02%) for 3 months elevated the levels of c-Fos, c-Jun and c-Myc proteins in the rat livers. The AAF-induced c-Jun, c-Fos and c-Myc expressions were significantly magnified (P < 0.001) by NaNO2. These data confirmed that the strengthening of AAF-induced hepatocarcinogenesis by NaNO2 should be associated with its enhancing effect on the AAF-induced increases in the expressions of c-Jun, c-Fos and c-Myc.  相似文献   
92.
The physical widths of reference features incorporated into electrical linewidth test structures patterned in films of monocrystalline silicon have been determined from Kelvin voltage measurements. The films in which the test structures are patterned are electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide provided by SIMOX (Separation by the IMplantation of OXygen) processing. The motivation is to facilitate the development of linewidth reference materials for critical-dimension (CD) metrology-instrument calibration. The selection of the (110) orientation of the starting silicon and the orientation of the structures' features relative to the crystal lattice enable a lattice-plane-selective etch to generate reference-feature properties of rectangular cross section and atomically planar sidewalls. These properties are highly desirable for CD applications in which feature widths are certified with nanometer-level uncertainty for use by a diverse range of CD instruments. End applications include the development and calibration of new generations of CD instruments directed at controlling processes for manufacturing devices having sub-quarter-micrometer features  相似文献   
93.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications  相似文献   
94.
95.
The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency  相似文献   
96.
Canny  J. 《Computer Journal》1993,36(5):409-418
  相似文献   
97.
98.
99.
100.
Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 172–176, May–June, 1994  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