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   312718篇
  免费   17121篇
  国内免费   293篇
电工技术   4930篇
综合类   107篇
化学工业   62145篇
金属工艺   15958篇
机械仪表   11342篇
建筑科学   6590篇
矿业工程   3829篇
能源动力   5171篇
轻工业   20703篇
水利工程   4609篇
石油天然气   13141篇
武器工业   33篇
无线电   27764篇
一般工业技术   78348篇
冶金工业   39573篇
原子能技术   11243篇
自动化技术   24646篇
  2021年   3642篇
  2020年   4180篇
  2019年   6520篇
  2018年   9366篇
  2017年   9930篇
  2016年   10783篇
  2015年   7591篇
  2014年   9949篇
  2013年   16998篇
  2012年   11500篇
  2011年   12580篇
  2010年   10997篇
  2009年   11558篇
  2008年   11177篇
  2007年   10646篇
  2006年   8650篇
  2005年   7481篇
  2004年   7348篇
  2003年   7098篇
  2002年   6836篇
  2001年   6366篇
  2000年   6308篇
  1999年   5084篇
  1998年   9300篇
  1997年   7246篇
  1996年   5322篇
  1995年   4211篇
  1994年   3851篇
  1993年   4115篇
  1992年   3396篇
  1991年   3546篇
  1990年   3623篇
  1989年   3509篇
  1988年   3425篇
  1987年   3384篇
  1986年   3270篇
  1985年   3442篇
  1984年   3366篇
  1983年   3240篇
  1982年   3113篇
  1981年   3168篇
  1980年   3206篇
  1979年   3322篇
  1978年   3562篇
  1977年   3690篇
  1976年   4418篇
  1975年   3247篇
  1974年   3337篇
  1973年   3398篇
  1972年   3005篇
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
101.
102.
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified.  相似文献   
103.
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage.  相似文献   
104.
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders.  相似文献   
105.
106.
This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications.  相似文献   
107.
108.
109.
Shevkunov  S. V. 《High Temperature》2015,53(2):259-271
High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of...  相似文献   
110.
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