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   268013篇
  免费   2832篇
  国内免费   1238篇
电工技术   4766篇
综合类   183篇
化学工业   40811篇
金属工艺   12902篇
机械仪表   9164篇
建筑科学   5399篇
矿业工程   2557篇
能源动力   6258篇
轻工业   18587篇
水利工程   3652篇
石油天然气   9320篇
武器工业   61篇
无线电   27507篇
一般工业技术   58451篇
冶金工业   44941篇
原子能技术   8673篇
自动化技术   18851篇
  2021年   2763篇
  2019年   2615篇
  2018年   4858篇
  2017年   4947篇
  2016年   5389篇
  2015年   3037篇
  2014年   5042篇
  2013年   11759篇
  2012年   7568篇
  2011年   9547篇
  2010年   7790篇
  2009年   8685篇
  2008年   8820篇
  2007年   8648篇
  2006年   7388篇
  2005年   6648篇
  2004年   6158篇
  2003年   6016篇
  2002年   5777篇
  2001年   5873篇
  2000年   5629篇
  1999年   5557篇
  1998年   13435篇
  1997年   9454篇
  1996年   7196篇
  1995年   5467篇
  1994年   4775篇
  1993年   5009篇
  1992年   3804篇
  1991年   3860篇
  1990年   3769篇
  1989年   3711篇
  1988年   3622篇
  1987年   3201篇
  1986年   3254篇
  1985年   3590篇
  1984年   3315篇
  1983年   3167篇
  1982年   2847篇
  1981年   2814篇
  1980年   2863篇
  1979年   2879篇
  1978年   2861篇
  1977年   3112篇
  1976年   3678篇
  1975年   2639篇
  1974年   2505篇
  1973年   2603篇
  1972年   2316篇
  1971年   2115篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 31–32, February, 1990.  相似文献   
992.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 9, pp. 34–35, September, 1990.  相似文献   
993.
Artificial Intelligence Review - Attribute weighting is a task of paramount relevance in multi-attribute decision-making (MADM). Over the years, different approaches have been developed to face...  相似文献   
994.
Programming and Computer Software - This paper investigates the implementation of virtual networks on the SDN data plane modeled by a graph of physical connections between network nodes. A virtual...  相似文献   
995.
Microsystem Technologies - The quantitative analysis of microwave noise available in the double gate (DG) high electron transistors of mobility (HEMT) is reported in this paper. For this analysis,...  相似文献   
996.
997.
Conclusions The eutectic in the Co-VC system corresponds to the composition with 14% VC and a temperature of 1340 ± 20°C and the maximum solubility of vanadium carbide in cobalt is 6%. The Co-VC section is not a quasibinary section of the Co-V-C phase diagram.The eutectic in the Co-NbC system melts at 1360°C and contains 11–12% NbC.The as-cast alloys of the Co-VC-NbC system are in the metastable two-phase condition and the only carbide phase is a carbide of complex composition which is a three-component solid solution of vanadium and niobium monocarbides.The fusibility diagram of the equilibrium phase diagram of the Co-VC-NbC system is characterized by the four-phase eutectic equilibrium L Co + VC + NbC with the point of the ternary eutectic at 1330 ± 20°C and a composition of 11% VC, 4% NbC, and 85% Co. The Co-VC-NbC equilibrium phase diagram does not contain ternary compounds and the equilibrium phases are cobalt- and vanadium- and niobium carbide-base solid solutions. The total volume share of the carbide constituents of the ternary eutectic somewhat exceeds the share of carbide phases in the boundary eutectics Co-VC and Co-NbC.The total solubility of the carbides in cobalt does not exceed 2–3%.Translated from Poroshkovaya Metallurgiya. No. 3(315), pp. 80–87, March, 1989.  相似文献   
998.
1.  The method of infrared spectroscopy allows one to record, visualize, and measure the stress state of exposed surfaces of metallic structures of small thicknesses (the studies were carried out on samples of thicknesses up to 10 mm). The proposed method can be used to study the stress concentrations in the plastic range, including conditions of complex loading.
2.  Noncontacting measurements, good reproducibility, and high resolution indicate that the proposed method should be of practical interest in determining the stress state of engineering structures.
Odessa Institute of Marine Engineering. Translated from Problemy Prochnosti, No. 8, pp. 80–85, August, 1989.  相似文献   
999.
We derive the Laplace transform of the joint distribution density of the number of jobs and of the vector of their flow time in a GI/GI/1/ queue with a constant constraint on job flow time.Translated from Kibernetika, No. 1, pp. 78–81, January–February, 1889.  相似文献   
1000.
1.  During operation of large multipurpose reservoirs their unsatisfactory sanitary and engineering state, ineffective use of their water and biological resources, and unfavorable ecological conditions were revealed, which requires their immediate improvement.
2.  There are real ways of improving these sanitary state and use of the water and biological resources of reservoirs, which were established when drawing up the schemes.
3.  A thorough elaboration of ecological problems of the examined reservoirs aimed at an improvement of the ecological conditions on each reservoir and on the territories adjacent to them is required.
4.  To solve the stated problem it is necessary to implement a number of coordinated measures. For this purpose, a scientifically founded approach based on a prediction of the results of their accomplishment is required. The interrelatedness and interdetermination of these measures with respect to increasing the effectiveness of using water, land, and biological resources should be based on scientific approaches of aquatorial regionalization and planning of reservoirs. Such an approach, unfortunately, is absent in many schemes.
5.  The investments and expenditures being provided for the indicated purposes should be aimed at achieving priority goals on improving the sanitary state of reservoirs, water quality, and effective use of their resources. The investments provided for in the schemes should be based on real sources of financing and should be coordinated with the plan of the concerned organizations, which are the title holders of the objects planned for construction.
Deceased  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