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   569013篇
  免费   6874篇
  国内免费   1020篇
电工技术   10556篇
综合类   473篇
化学工业   90775篇
金属工艺   23392篇
机械仪表   18584篇
建筑科学   12598篇
矿业工程   4320篇
能源动力   14642篇
轻工业   45974篇
水利工程   6973篇
石油天然气   14996篇
武器工业   39篇
无线电   60582篇
一般工业技术   116663篇
冶金工业   95690篇
原子能技术   14698篇
自动化技术   45952篇
  2021年   5641篇
  2020年   4141篇
  2019年   5425篇
  2018年   9403篇
  2017年   9554篇
  2016年   10000篇
  2015年   6141篇
  2014年   10390篇
  2013年   26377篇
  2012年   15932篇
  2011年   21280篇
  2010年   17113篇
  2009年   18934篇
  2008年   19156篇
  2007年   18820篇
  2006年   16353篇
  2005年   14780篇
  2004年   14044篇
  2003年   13719篇
  2002年   13278篇
  2001年   12868篇
  2000年   12339篇
  1999年   12026篇
  1998年   27683篇
  1997年   20060篇
  1996年   15650篇
  1995年   12018篇
  1994年   10871篇
  1993年   10627篇
  1992年   8343篇
  1991年   8109篇
  1990年   7997篇
  1989年   7774篇
  1988年   7486篇
  1987年   6758篇
  1986年   6537篇
  1985年   7396篇
  1984年   6706篇
  1983年   6439篇
  1982年   5780篇
  1981年   5902篇
  1980年   5637篇
  1979年   5737篇
  1978年   5667篇
  1977年   6184篇
  1976年   7693篇
  1975年   5109篇
  1974年   4903篇
  1973年   4982篇
  1972年   4281篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
2.
3.
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.  相似文献   
4.
5.
6.
Because of heat amount is different from peripheral to central of friction welding interface, which is leaded to vary the characterizations along that interface. Current study, respectively, focused on the effect of different friction pressure on micro-structural and mechanical properties of that friction welding joint interface. Presently, these friction pressures are 110, 130, 150 and 170 MPa while kept all other conditions constant. The effects of different friction pressure on welding interface characterization were investigated by EDX, SEM, tensile, compression, impact and hardness tests. The tensile tests carried out on the standardized test piece with diameter 6 mm and 8 mm, thus, compression tests were extracted from the positions of 0°, 45° 90° with test specimen of 4 mm diameter and 6.5 mm length at weld center. Whereas, the impact test pieces were picked up in two positions, the first one is symmetrical, which it obtained to the respect of the rotation axis and the interface, on the other hand, the second one is non-symmetrical with the axis of rotation and symmetrical to the interface, for making the notch head coincide with the center of the welded joint, The obtained results showed that with reducing of friction pressure will present lack of bonding increasing from peripheral toward the welding center, which will responsible on reducing of the mechanical properties such as tensile, compression and impact strength.  相似文献   
7.
8.
9.
10.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  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