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   81011篇
  免费   1400篇
  国内免费   693篇
电工技术   1475篇
综合类   50篇
化学工业   12646篇
金属工艺   3560篇
机械仪表   2766篇
建筑科学   1904篇
矿业工程   523篇
能源动力   1997篇
轻工业   8086篇
水利工程   909篇
石油天然气   2336篇
武器工业   41篇
无线电   7554篇
一般工业技术   17823篇
冶金工业   12486篇
原子能技术   2652篇
自动化技术   6296篇
  2022年   663篇
  2021年   1122篇
  2020年   890篇
  2019年   974篇
  2018年   1876篇
  2017年   1896篇
  2016年   2067篇
  2015年   1170篇
  2014年   1864篇
  2013年   4253篇
  2012年   2805篇
  2011年   3264篇
  2010年   2730篇
  2009年   2959篇
  2008年   2984篇
  2007年   2885篇
  2006年   2454篇
  2005年   2071篇
  2004年   1994篇
  2003年   1944篇
  2002年   1855篇
  2001年   1793篇
  2000年   1766篇
  1999年   1647篇
  1998年   3725篇
  1997年   2642篇
  1996年   1979篇
  1995年   1569篇
  1994年   1365篇
  1993年   1370篇
  1992年   1016篇
  1991年   1068篇
  1990年   1089篇
  1989年   1064篇
  1988年   955篇
  1987年   880篇
  1986年   888篇
  1985年   951篇
  1984年   800篇
  1983年   785篇
  1982年   689篇
  1981年   696篇
  1980年   670篇
  1979年   654篇
  1978年   625篇
  1977年   774篇
  1976年   935篇
  1975年   582篇
  1974年   553篇
  1973年   547篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Water Resources Management - This paper aims to evaluate the possibility of using non-utilized hydraulic energy in urban water distribution systems. For this purpose, the viability and possible...  相似文献   
32.
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor...  相似文献   
33.
Zhang  Xi  Wang  Xianhai  Zhao  Hongke  Ordóñez de Pablos  Patricia  Sun  Yongqiang  Xiong  Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with...  相似文献   
34.
Refractories and Industrial Ceramics - Results of studying the rheotechnological properties of moldable refractory mixes based on bauxite suspensions plasticized with refractory clay are presented....  相似文献   
35.
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes.  相似文献   
36.
Journal of Inorganic and Organometallic Polymers and Materials - This work aimed to investigate the impact of Lead-fluoride based glasses via theoretical and simulation techniques on mechanical and...  相似文献   
37.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  相似文献   
38.
Protection of Metals and Physical Chemistry of Surfaces - In this work, a universal sorbent has been obtained that works according to the mechanisms of chemisorption and adsorption by impregnating...  相似文献   
39.
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades.  相似文献   
40.
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included.  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