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   17668篇
  免费   582篇
  国内免费   30篇
电工技术   185篇
综合类   8篇
化学工业   3145篇
金属工艺   302篇
机械仪表   414篇
建筑科学   888篇
矿业工程   75篇
能源动力   479篇
轻工业   1514篇
水利工程   176篇
石油天然气   47篇
武器工业   1篇
无线电   1432篇
一般工业技术   3247篇
冶金工业   3742篇
原子能技术   115篇
自动化技术   2510篇
  2023年   84篇
  2022年   180篇
  2021年   263篇
  2020年   213篇
  2019年   262篇
  2018年   307篇
  2017年   301篇
  2016年   334篇
  2015年   298篇
  2014年   428篇
  2013年   996篇
  2012年   741篇
  2011年   1023篇
  2010年   743篇
  2009年   702篇
  2008年   832篇
  2007年   755篇
  2006年   638篇
  2005年   613篇
  2004年   500篇
  2003年   495篇
  2002年   464篇
  2001年   302篇
  2000年   326篇
  1999年   278篇
  1998年   804篇
  1997年   637篇
  1996年   476篇
  1995年   392篇
  1994年   326篇
  1993年   328篇
  1992年   189篇
  1991年   164篇
  1990年   191篇
  1989年   183篇
  1988年   155篇
  1987年   144篇
  1986年   129篇
  1985年   162篇
  1984年   165篇
  1983年   152篇
  1982年   120篇
  1981年   110篇
  1980年   117篇
  1979年   116篇
  1978年   117篇
  1977年   148篇
  1976年   230篇
  1975年   82篇
  1974年   77篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
3.
If you don't know the current productivity rates, usage volumes, and other quantitative baseline data for your software operations, then software might not be a key component of the company's core business. The evaluation criteria in this article can help the IS executive determine the outsourcing options for software operations.  相似文献   
4.
Current cementing techniques of distal plugging, pulsatile water cleaning of the canal, and retrograde filling with PMMA in a low-viscous state prepared using porosity reduction techniques and then pressurized have been shown to give excellent results at 10 or more years after operation. However, physical and aging characteristics of PMMA do not guarantee that those results will hold up in the 20- to 30-year time frame. Fifteen-year experience with bony ingrowth systems indicate the development of a durable interface without PMMA, although the interface does appear more vulnerable to attack by the biologic reaction to HMWPE debris. Bone remodeling appears more favorable around proximally fixed bone ingrowth prostheses than around distally fixed prostheses. Softening of the physical characteristics of the stem tip may reduce the incidence of thigh pain. Patients with high activity potential and a life expectancy of greater than 25 years should be strongly considered for a proximally fixed bone ingrowth or ongrowth prosthesis.  相似文献   
5.
Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused by either variations in cooling rate during casting or the addition of grain refiners.  相似文献   
6.
This paper derives the governing equations for the thermomechanical behaviour of composites. When the basic equations for the thermoelastic behaviour of solids were first derived in the nineteenth century several approximations were made. The effect of these assumptions are discussed and illustrated by the results of a simple laboratory test. The implications of this work on the analysis of impact damaged laminates are then discussed.  相似文献   
7.
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   
8.
9.
Multimedia data from two probability-based exposure studies were investigated in terms of how missing data and measurement-error imprecision affected estimation of population parameters and associations. Missing data resulted mainly from individuals'refusing to participate in certain measurement activities, rather than from field or laboratory problems; it suggests that future studies should focus on methods for maximizing participation rates. Measurement error variances computed from duplicate-sample data were small relative to the inherent variation in the populations; consequently, adjustments in nonparametric percentile estimates to account for measurement imprecision were small. Methods of adjustment based on lognormality assumptions, however, appeared to perform poorly.  相似文献   
10.
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