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   287610篇
  免费   3531篇
  国内免费   815篇
电工技术   5033篇
综合类   162篇
化学工业   45461篇
金属工艺   11897篇
机械仪表   8608篇
建筑科学   6872篇
矿业工程   1834篇
能源动力   6750篇
轻工业   25929篇
水利工程   3192篇
石油天然气   7087篇
武器工业   16篇
无线电   31484篇
一般工业技术   56998篇
冶金工业   51562篇
原子能技术   7541篇
自动化技术   21530篇
  2021年   2097篇
  2018年   3676篇
  2017年   3624篇
  2016年   3909篇
  2015年   2468篇
  2014年   4235篇
  2013年   12046篇
  2012年   6837篇
  2011年   9225篇
  2010年   7572篇
  2009年   8655篇
  2008年   8943篇
  2007年   8826篇
  2006年   7847篇
  2005年   7321篇
  2004年   6816篇
  2003年   6562篇
  2002年   6635篇
  2001年   6506篇
  2000年   6180篇
  1999年   6245篇
  1998年   14800篇
  1997年   11057篇
  1996年   8597篇
  1995年   6535篇
  1994年   5933篇
  1993年   5800篇
  1992年   4485篇
  1991年   4451篇
  1990年   4290篇
  1989年   4308篇
  1988年   4263篇
  1987年   3602篇
  1986年   3600篇
  1985年   4167篇
  1984年   3968篇
  1983年   3622篇
  1982年   3425篇
  1981年   3560篇
  1980年   3427篇
  1979年   3370篇
  1978年   3448篇
  1977年   3927篇
  1976年   5050篇
  1975年   3162篇
  1974年   3012篇
  1973年   3028篇
  1972年   2652篇
  1971年   2475篇
  1970年   2104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation.  相似文献   
82.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
83.
84.
The failure of frontline antibiotics in the clinic is one of the most serious threats to human health and requires a multitude of novel therapeutics and innovative approaches to treatment so as to curtail the growing crisis. In addition to traditional resistance mechanisms resulting in the lack of efficacy of many antibiotics, most chronic and recurring infections are further made tolerant to antibiotic action by the presence of biofilms. Herein, we report an expanded set of 5-benzylidene-4-oxazolidinones that are able to inhibit the formation of Staphylococcus aureus biofilms, disperse preformed biofilms, and, in combination with common antibiotics, are able to significantly reduce the bacterial load in a robust collagen-matrix model of biofilm infection.  相似文献   
85.
86.
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection.  相似文献   
87.
88.
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   
89.
90.
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   
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