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   365076篇
  免费   4451篇
  国内免费   1048篇
电工技术   6069篇
综合类   845篇
化学工业   55690篇
金属工艺   16851篇
机械仪表   11097篇
建筑科学   7956篇
矿业工程   2951篇
能源动力   7473篇
轻工业   25830篇
水利工程   4677篇
石油天然气   10845篇
武器工业   18篇
无线电   34508篇
一般工业技术   71043篇
冶金工业   75725篇
原子能技术   10407篇
自动化技术   28590篇
  2021年   2797篇
  2019年   2709篇
  2018年   5240篇
  2017年   5531篇
  2016年   6236篇
  2015年   3837篇
  2014年   5758篇
  2013年   13891篇
  2012年   10335篇
  2011年   13431篇
  2010年   9596篇
  2009年   10971篇
  2008年   10845篇
  2007年   10745篇
  2006年   9203篇
  2005年   11287篇
  2004年   10198篇
  2003年   9292篇
  2002年   8068篇
  2001年   7961篇
  2000年   7234篇
  1999年   7444篇
  1998年   21613篇
  1997年   15078篇
  1996年   11145篇
  1995年   8087篇
  1994年   6897篇
  1993年   6934篇
  1992年   4836篇
  1991年   4845篇
  1990年   4857篇
  1989年   4764篇
  1988年   4660篇
  1987年   4224篇
  1986年   4217篇
  1985年   4558篇
  1984年   4231篇
  1983年   4005篇
  1982年   3772篇
  1981年   4047篇
  1980年   3798篇
  1979年   3891篇
  1978年   4042篇
  1977年   4802篇
  1976年   6635篇
  1975年   3623篇
  1974年   3599篇
  1973年   3708篇
  1972年   3310篇
  1971年   2962篇
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
101.
102.
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   
103.
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature.  相似文献   
104.
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   
105.
International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...  相似文献   
106.
Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L−1). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway.  相似文献   
107.
Theoretical Foundations of Chemical Engineering - A choline chloride–sulfosalicylic acid deep eutectic solvent (DES) is proposed for dissolving the oxides Co(II), Cu(II), Zn(II), Fe(III),...  相似文献   
108.
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with...  相似文献   
109.
High Temperature - Experimental findings suggest that a strongly ionized, arc He plasma of atmospheric pressure does not exist in the state of the local thermodynamic equilibrium (LTE) expected for...  相似文献   
110.
Russian Engineering Research - Improvement in the wear resistance of plunger-pump rods is considered. Hardening by high-frequency current is proposed.  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