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   450302篇
  免费   6987篇
  国内免费   1408篇
电工技术   7870篇
综合类   352篇
化学工业   68417篇
金属工艺   17188篇
机械仪表   14355篇
建筑科学   9815篇
矿业工程   2244篇
能源动力   12421篇
轻工业   35217篇
水利工程   4720篇
石油天然气   8091篇
武器工业   23篇
无线电   51769篇
一般工业技术   90868篇
冶金工业   86247篇
原子能技术   9380篇
自动化技术   39720篇
  2022年   2985篇
  2021年   4924篇
  2020年   3814篇
  2019年   4698篇
  2018年   8273篇
  2017年   8219篇
  2016年   8755篇
  2015年   5629篇
  2014年   8803篇
  2013年   23319篇
  2012年   14137篇
  2011年   17717篇
  2010年   14178篇
  2009年   15524篇
  2008年   16103篇
  2007年   15626篇
  2006年   13734篇
  2005年   12178篇
  2004年   11540篇
  2003年   11338篇
  2002年   10622篇
  2001年   10266篇
  2000年   9657篇
  1999年   10167篇
  1998年   27818篇
  1997年   18878篇
  1996年   14216篇
  1995年   10353篇
  1994年   9077篇
  1993年   9108篇
  1992年   6291篇
  1991年   5937篇
  1990年   5925篇
  1989年   5561篇
  1988年   5268篇
  1987年   4610篇
  1986年   4515篇
  1985年   5064篇
  1984年   4623篇
  1983年   4151篇
  1982年   3837篇
  1981年   3938篇
  1980年   3616篇
  1979年   3464篇
  1978年   3456篇
  1977年   3994篇
  1976年   5365篇
  1975年   2938篇
  1974年   2741篇
  1973年   2811篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
992.
The use of schungite as a partial replacement for coke is practiced in Russia at a number of metallurgical plants, both in the production of foundry iron (its primary use) and in making conversion pig iron. The largest amount of coke is replaced when foundry iron is being made, the replacement coefficient in this case having a value within the range 0.8–1.3. Studies that included continuous monitoring of the temperature of the carbon blocks in blast furnaces with volumes of 1719, 3200, and 5580 m3 unambiguously demonstrate that the thickness of the slag crust in blast furnaces increases with the use of schungite. Protecting the lining of the hearth through the use of schungite is also accompanied by a decrease in coke consumption. __________ Translated from Metallurg, No. 8, pp. 53–57, August, 2007.  相似文献   
993.
994.
Radioimmunoassay was employed to examine distribution of antigenic structures of bovine serum albumin (BSA), absorbed by the gastrointestinal tract, in the blood serum and organs of intact rats. It was shown that 3 h after administering 3H-BSA an appreciable amount of its antigenic structures could be identified in the blood serum, liver, spleen, and carcass of the animals. The total amount of antigenic determinants of BSA which got into the internal environment of the body from the intestine amounted to about 0.2% of the dose administered. The highest specific content of antigenic structures of BSA supplied via the intestinal barrier was detected in the spleen.  相似文献   
995.
Comparative studies on Ar and He closed-cycle MHD power plants combined with fossil fuel are performed. The sizes of a regenerative heat exchanger and a boiler are expected to be smaller for He than for Ar. The pressure loss of a working gas in a regenerative heat exchanger is reduced for He. The purification subsystem for He is expected to be more compact and economical than that for Ar; but a larger compressor is required for He than for Ar.  相似文献   
996.
997.
998.
Surface tension of pure copper and its alloys with Sn has been measured at 1000°C in a hydrogen atmosphere. Surface tension of a free surface equaled 1.81 N/m for pure copper, and 1.55, 1.38, and 1.28 N/m for the alloys with 0.05, 0.22, and 0.33 at % Sn, respectively; surface tension at grain boundaries equaled 0.5 N/m for pure copper, and 0.36, 0.3, and 0.23 N/m for the alloys, respectively. Based on these data, the concentration dependence of tin absorption at a free surface and grain boundaries has been calculated. Parameters of Sn absorption at grain boundaries and a free surface of copper have been compared with those of Sb and Bi.  相似文献   
999.
PIII is a powerful method to obtain hard and wear resistant surface on Ti alloys and NiTi by oxygen or nitrogen implantation. By adjusting the temperature, treatment time and heating regime, different phase compositions and layer thickness can be obtained. Depending on the specific system, a strong influence of the resulting microstructure on the wear and fatigue properties was observed. By considering these restrictions, successful animal tests can be designed and executed, as shown in this review article.  相似文献   
1000.
The present study examines the concurrent and predictive relationships between therapist psychodynamic-interpersonal activity and therapist-rated alliance. Ratings from 45 patient and therapist dyads engaged in short term psychodynamic psychotherapy from a point early (3rd or 4th session) and late (the session at which 90% of the treatment was completed) in treatment were used. The results suggest that therapists who have positive views of the alliance early in treatment also have positive views of the alliance later in treatment. Therapists who used psychodynamic-interpersonal activities early in treatment also made use of psychodynamic-interpersonal activities later in treatment. Moreover, the use of psychodynamic-interpersonal activities early in treatment was positively related to both global and specific aspects of therapist-rated alliance late in treatment. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  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