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   3613篇
  免费   53篇
  国内免费   3篇
电工技术   50篇
化学工业   766篇
金属工艺   47篇
机械仪表   61篇
建筑科学   153篇
矿业工程   18篇
能源动力   67篇
轻工业   316篇
水利工程   33篇
石油天然气   8篇
无线电   372篇
一般工业技术   444篇
冶金工业   868篇
原子能技术   34篇
自动化技术   432篇
  2022年   21篇
  2021年   56篇
  2020年   33篇
  2019年   41篇
  2018年   46篇
  2017年   36篇
  2016年   34篇
  2015年   43篇
  2014年   57篇
  2013年   180篇
  2012年   86篇
  2011年   149篇
  2010年   115篇
  2009年   115篇
  2008年   117篇
  2007年   149篇
  2006年   98篇
  2005年   92篇
  2004年   88篇
  2003年   90篇
  2002年   93篇
  2001年   63篇
  2000年   67篇
  1999年   74篇
  1998年   181篇
  1997年   135篇
  1996年   93篇
  1995年   83篇
  1994年   73篇
  1993年   70篇
  1992年   57篇
  1991年   53篇
  1990年   52篇
  1989年   40篇
  1988年   53篇
  1987年   62篇
  1986年   50篇
  1985年   53篇
  1984年   42篇
  1983年   48篇
  1982年   37篇
  1981年   53篇
  1980年   36篇
  1979年   41篇
  1978年   36篇
  1977年   55篇
  1976年   57篇
  1975年   52篇
  1974年   26篇
  1973年   32篇
排序方式: 共有3669条查询结果,搜索用时 15 毫秒
141.
142.
143.
Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented.  相似文献   
144.
This article introduces a new problem called the Capacity and Distance Constrained Plant Location Problem. It is an extension of the discrete capacitated plant location problem, where the customers assigned to each plant have to be packed in groups that will be served by one vehicle each. The constraints include two types of capacity. On the one hand plants are capacitated, and the demands of the customers are indivisible. On the other hand, the total distance traveled by each vehicle to serve its assigned customers in round trips plant–customer–plant is also limited. The paper addresses different modeling aspects of the problem. It describes a tabu search algorithm for its solution. Extensive computational tests indicate that the proposed heuristic consistently yields optimal or near-optimal solutions.  相似文献   
145.
146.
147.
148.
There is an urgent need for new drugs for the treatment of tropical parasitic diseases such as human African trypanosomiasis, which is caused by Trypanosoma brucei. The enzyme trypanothione reductase (TryR) is a potential drug target within these organisms. Herein we report the screening of a 62 000 compound library against T. brucei TryR. Further work was undertaken to optimise potency and selectivity of two novel‐compound series arising from the enzymatic and whole parasite screens and mammalian cell counterscreens. Both of these series, containing either a quinoline or pyrimidinopyrazine scaffold, yielded low micromolar inhibitors of the enzyme and growth of the parasite. The challenges of inhibiting TryR with druglike molecules is discussed.  相似文献   
149.
A new ceramic for capacitors, which exhibits flat dielectric curves with relative permittivity values (ɛ) as high as 3000 (Y7R or X7R class), has been synthesized. Use of a niobate, K0.2Sr0.4NbO3 (KSN), with a tetragonal tungsten bronze structure (TTB), as a major phase for the fabrication of such ceramics is shown for the first time. Nevertheless, the addition of perovskites as minor agents—PbMg1/3Nb2/3O3 (PMN)—is necessary to obtain stable temperature. Moreover, the use of lithium salts as sintering agents has been shown to be important for the fabrication of these ceramics.  相似文献   
150.
The cooling power of aqueous solutions of ethylene oxide-propylene oxide copolymers are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. For temperature T>400°C, the viscosity plays the predominant role; for T<400°C, the cooling is controlled by the polymer precipitation and the cooling rate decreases by lowering the cloud point of the polymer solution. This work demonstrates the possibility of adjusting the cooling curves by taking into account the thermodynamical properties of the polymer.  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