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   109229篇
  免费   17451篇
  国内免费   2745篇
电工技术   4108篇
技术理论   5篇
综合类   4517篇
化学工业   28775篇
金属工艺   4171篇
机械仪表   4650篇
建筑科学   6525篇
矿业工程   1600篇
能源动力   2343篇
轻工业   13059篇
水利工程   1735篇
石油天然气   4047篇
武器工业   546篇
无线电   13369篇
一般工业技术   21348篇
冶金工业   4780篇
原子能技术   1542篇
自动化技术   12305篇
  2023年   898篇
  2022年   1741篇
  2021年   2595篇
  2020年   3237篇
  2019年   4623篇
  2018年   4883篇
  2017年   5416篇
  2016年   5744篇
  2015年   6341篇
  2014年   6931篇
  2013年   8717篇
  2012年   6868篇
  2011年   6892篇
  2010年   6594篇
  2009年   6394篇
  2008年   5913篇
  2007年   5437篇
  2006年   4992篇
  2005年   4226篇
  2004年   3458篇
  2003年   3116篇
  2002年   3165篇
  2001年   2757篇
  2000年   2409篇
  1999年   1793篇
  1998年   1076篇
  1997年   952篇
  1996年   812篇
  1995年   698篇
  1994年   562篇
  1993年   456篇
  1992年   426篇
  1991年   396篇
  1990年   351篇
  1989年   372篇
  1988年   330篇
  1987年   292篇
  1986年   323篇
  1985年   288篇
  1984年   311篇
  1983年   285篇
  1979年   291篇
  1978年   360篇
  1977年   337篇
  1976年   359篇
  1975年   335篇
  1974年   396篇
  1973年   375篇
  1972年   359篇
  1971年   329篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
分析了BC-480支架在综采工作面使用中液压系统配置低的原因,提出了系统的改造原则和方案,比较了改制前后支架的动作速度.  相似文献   
82.
83.
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
84.
85.
Mixtures of Cr and Mo elemental powders, with the nominal compositions Cr25Mo75, Cr50Mo50, and Cr75Mo25, are processed by high-energy ball milling at ambient temperature. Milling is observed to force the mixing of the immiscible bcc elements Cr and Mo into solid solutions. The lattice parameter of these solid solutions, measured by X-ray diffraction (XRD), displays the expected positive deviation from Vegard’s law. These deviations are compared to the ones predicted by Eshelby’s inclusion model for dilute alloys. The conventional Williamson-Hall approach is shown to fail to determine the grain size in as-milled samples, probably due to the high density of dislocations. Annealing at 700 °C for 10 hours under argon leads to a large reduction in structural defect density, without inducing any significant decomposition. The mixing measured in Cr-Mo is discussed in the broader context of the mechanical mixing forced by ball milling in moderately immiscible systems.  相似文献   
86.
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007.  相似文献   
87.
关于本地传输网网络优化的探讨   总被引:2,自引:0,他引:2  
根据长期工作经验,对现有网络存在的问题进行分析,提出对本地传输网网络优化的有关建议。  相似文献   
88.
Parallel multilevel fast multipole method for solving large-scale problems   总被引:1,自引:0,他引:1  
The Multilevel Fast Multipole Method (FMM) is a well-established method and can be applied to solve electromagnetic (EM) scattering problems. Compared with other traditional methods, it requires less computational time and memory. However, constrained by a single processor's speed and memory limitations, the problem size that can be solved by serial implementation is still relatively small. For a million-unknown target, the computational time on a single processor is intolerable, and memory could be easily exhausted. Parallel-computing technology, which can utilize multiprocessors, provides an efficient way to solve electrically large-scale EM problems. This paper will focus on discussing the parallel methodologies applied to a multilevel FMM code, as well as demonstrating the computational efficiency of the parallel approach.  相似文献   
89.
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry  相似文献   
90.
Liquid–liquid two‐phase epoxidation from cyclohexene and cyclooctene in aqueous potassium peroxymonosulfate (commercially available as Oxone®) solution was studied as an application in pollution prevention. To avoid potential emissions of volatile organic compounds an aqueous solution was employed to replace the usual chlorinated solvents used in epoxide production. A droplet column reactor and stirred tank reactor were used to investigate two‐phase synthesis of epoxide. An aqueous Oxone® solution was used to oxidize a dispersion of alkene droplets and form epoxide. The study of aqueous epoxidation in both reactors showed that the epoxidation of alkenes can be represented as a first order reaction with respect to alkene. The salting out effect of Oxone® concentration was studied in both reactors and found to be very similar at optimal conditions. In comparing the two reactors, it was found that the droplet column reactor produces larger quantities of product per unit reactor volume for the same reaction time. The objective of this study is to provide an alternative reactor design and synthesis route that can meet pollution prevention goals. Copyright © 2004 Society of Chemical Industry  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