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   285308篇
  免费   5992篇
  国内免费   1886篇
电工技术   5846篇
技术理论   5篇
综合类   1321篇
化学工业   46311篇
金属工艺   11684篇
机械仪表   8292篇
建筑科学   7268篇
矿业工程   1802篇
能源动力   6002篇
轻工业   29173篇
水利工程   3095篇
石油天然气   6108篇
武器工业   255篇
无线电   29051篇
一般工业技术   53758篇
冶金工业   53421篇
原子能技术   5754篇
自动化技术   24040篇
  2021年   2969篇
  2020年   2066篇
  2019年   2458篇
  2018年   4141篇
  2017年   4067篇
  2016年   4474篇
  2015年   3499篇
  2014年   5381篇
  2013年   12895篇
  2012年   8868篇
  2011年   11351篇
  2010年   9128篇
  2009年   9643篇
  2008年   10533篇
  2007年   10602篇
  2006年   9130篇
  2005年   7983篇
  2004年   7103篇
  2003年   6608篇
  2002年   6586篇
  2001年   6608篇
  2000年   6186篇
  1999年   6252篇
  1998年   14808篇
  1997年   10715篇
  1996年   8088篇
  1995年   6036篇
  1994年   5481篇
  1993年   5312篇
  1992年   4086篇
  1991年   3897篇
  1990年   3946篇
  1989年   3909篇
  1988年   3655篇
  1987年   3156篇
  1986年   3165篇
  1985年   3595篇
  1984年   3483篇
  1983年   3220篇
  1982年   2809篇
  1981年   3057篇
  1980年   2793篇
  1979年   2942篇
  1978年   2830篇
  1977年   3037篇
  1976年   4116篇
  1975年   2532篇
  1974年   2360篇
  1973年   2419篇
  1972年   2015篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied...  相似文献   
104.
105.
106.
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.  相似文献   
107.
C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75?×?103 Ω?1 cm?1) were obtained for GIZO films with In/Zn ratio ≥?1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85–0.90 for the GIZO films.  相似文献   
108.
Among the thermoplastic elastomers that play important roles in the polymer industry due to their superior properties, styrene-based species and polyurethane block copolymers are of great interest. Poly(styrene-ethylene-butadiene-styrene) (SEBS) as a triblock copolymer seems to have the potential to meet many demands in different applications due to various industrial requirements where durability, biocompatibility, breaking elongation, and interfacial adhesion are important. In this study, the SEBS triblock copolymer was functionalized with natural (Satureja hortensis, SH) and synthetic (nanopowder, TiO2) agents to obtain composite nanofibers by electrospinning and electrospraying methods for use in biomedical and water filtration applications. The results were compared with thermoplastic polyurethane (TPU) composite nanofibers, which are commonly used in these fields. Here, functionalized SEBS nanofibers exhibited antibacterial effect while at the same time improving cell viability. In addition, because of successful water filtration by using the SEBS composite nanofibers, the material may have a good potential to be used comparably to TPU for the application.  相似文献   
109.
Journal of Computer and Systems Sciences International - We consider a controlled mechanical system with one degree of freedom described by an angular coordinate. The system is under the action of...  相似文献   
110.
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved.  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