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   5625篇
  免费   139篇
  国内免费   16篇
电工技术   107篇
综合类   13篇
化学工业   955篇
金属工艺   132篇
机械仪表   93篇
建筑科学   254篇
矿业工程   23篇
能源动力   136篇
轻工业   640篇
水利工程   27篇
石油天然气   26篇
无线电   429篇
一般工业技术   695篇
冶金工业   1548篇
原子能技术   41篇
自动化技术   661篇
  2022年   46篇
  2021年   57篇
  2020年   52篇
  2019年   46篇
  2018年   71篇
  2017年   59篇
  2016年   89篇
  2015年   82篇
  2014年   114篇
  2013年   259篇
  2012年   150篇
  2011年   204篇
  2010年   158篇
  2009年   160篇
  2008年   177篇
  2007年   192篇
  2006年   183篇
  2005年   143篇
  2004年   135篇
  2003年   148篇
  2002年   126篇
  2001年   102篇
  2000年   103篇
  1999年   116篇
  1998年   335篇
  1997年   231篇
  1996年   163篇
  1995年   108篇
  1994年   132篇
  1993年   135篇
  1992年   83篇
  1991年   67篇
  1990年   66篇
  1989年   83篇
  1988年   70篇
  1987年   62篇
  1986年   47篇
  1985年   69篇
  1984年   74篇
  1983年   73篇
  1982年   51篇
  1981年   55篇
  1980年   63篇
  1979年   47篇
  1978年   58篇
  1977年   69篇
  1976年   101篇
  1975年   47篇
  1973年   44篇
  1972年   47篇
排序方式: 共有5780条查询结果,搜索用时 7 毫秒
1.
2.
3.
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap.  相似文献   
4.
5.
6.
The present work describes quantitative digital particle image velocimetry measurements of a full-scale water model of a thin slab mold. Different casting speeds and two submerged entry nozzles with one and two outlet ports have been investigated. The flow pattern of the single-port nozzle shows a counterclockwise-rotating double vortex that is nearly steady-state but leads to high stationary surface waves. The flow jets out of the two-port nozzle oscillate and produce a transient flow pattern with low wave amplitudes. The amplitudes for the one-port nozzle show a linear variation with the volumetric flow rate. The experimental results lead to a good interpretation of the flow phenomena and are used to validate steady-state numerical simulations with the commercial program, CFX, on the basis of the Reynolds equations. To describe anisotropic turbulence effects, the Reynolds stress model (RSM) is used for the flat single-port nozzle and the standard k-ɛ model for the mold flow. The calculated mean velocities and wave amplitudes, predicted from pressure distribution at the water surface, are generally in the consensus of the experimental data. An erratum to this article is available at .  相似文献   
7.
8.
Filtering algorithms are well accepted as a means of speeding up the solution of the consistent labeling problem (CLP). Despite the fact that path consistency does a better job of filtering than arc consistency, AC is still the preferred technique because it has a much lower time complexity. We are implementing parallel path consistency algorithms on multiprocessors and comparing their performance to the best sequential and parallel arc consistency algorithms.(1,2) (See also work by Kerethoet al. (3) and Kasif(4)) Preliminary work has shown linear performance increases for parallelized path consistency and also shown that in many cases performance is significantly better than the theoretical worst case. These two results lead us to believe that parallel path consistency may be a superior filtering technique. Finally, we have implemented path consistency as an outer product computation and have obtained good results (e.g., linear speedup on a 64K-node Connection Machine 2).  相似文献   
9.
The vicissitudes of the Israeli-Palestinian peace process since 1967 are analyzed using attitudes and related concepts where relevant. The 1967 war returned the two peoples' zero-sum conflict around national identity to its origin as a conflict within the land both peoples claim. Gradually, new attitudes evolved regarding the necessity and possibility of negotiations toward a two-state solution based on mutual recognition, which became the building stones of the 1993 Oslo agreement. Lacking a commitment to a final outcome, the Oslo-based peace process was hampered by reserve options, which increased avoidance at the expense of approach tendencies as the parties moved toward a final agreement. The resulting breakdown of the process in 2000 produced clashing narratives, reflecting different anchors for judgment and classical mirror images. Public support for violence increased, even as public opinion continued to favor a negotiated two-state solution. Reviving the peace process requires mutual reassurance about the availability of a partner for negotiating a principled peace based on a historic compromise that meets the basic needs and validates the identities of both peoples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
重馏分油加氢脱氮反应动力学模型的研究   总被引:10,自引:1,他引:9  
简要地介绍了一些典型的模型氮化物的HDN反应规律。根据胜利VGO在3722B催化剂上的大量HDN实验数据,提出了如下的HDN基本反应动力学方程:dCNdt=-k1+K*CNCNPH2为了扩大上式的应用范围,详细分析了各种因素(如原料油种类和馏程及H2S等)对HDN的影响,并开发了相应的经验关联式,从而得到了一个较完整的馏分油HDN反应动力学模型。验证实验表明,该模型是成功的。  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