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   8773篇
  免费   144篇
  国内免费   10篇
电工技术   89篇
综合类   5篇
化学工业   1221篇
金属工艺   162篇
机械仪表   228篇
建筑科学   280篇
矿业工程   55篇
能源动力   164篇
轻工业   693篇
水利工程   69篇
石油天然气   20篇
武器工业   1篇
无线电   748篇
一般工业技术   1338篇
冶金工业   3009篇
原子能技术   81篇
自动化技术   764篇
  2022年   48篇
  2021年   54篇
  2020年   40篇
  2019年   56篇
  2018年   78篇
  2017年   72篇
  2016年   85篇
  2015年   78篇
  2014年   99篇
  2013年   355篇
  2012年   193篇
  2011年   250篇
  2010年   252篇
  2009年   236篇
  2008年   254篇
  2007年   250篇
  2006年   213篇
  2005年   237篇
  2004年   175篇
  2003年   192篇
  2002年   191篇
  2001年   158篇
  2000年   172篇
  1999年   164篇
  1998年   821篇
  1997年   580篇
  1996年   422篇
  1995年   310篇
  1994年   265篇
  1993年   278篇
  1992年   115篇
  1991年   109篇
  1990年   122篇
  1989年   128篇
  1988年   122篇
  1987年   91篇
  1986年   80篇
  1985年   112篇
  1984年   113篇
  1983年   86篇
  1982年   75篇
  1981年   72篇
  1980年   86篇
  1979年   79篇
  1978年   88篇
  1977年   135篇
  1976年   222篇
  1975年   60篇
  1974年   63篇
  1973年   57篇
排序方式: 共有8927条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
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   
5.
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   
6.
7.
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   
8.
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   
9.
Boron is observed to diffuse very slowly in germanium, as opposed to its behaviour in silicon where it exhibits Transient Enhanced Diffusion effects in implanted samples. As a result of this slow diffusion, boron is a very stable dopant, allowing devices to be created with very well-defined doping regions. To understand this superior performance, calculations were performed on a variety of boron diffusion paths, within vacancy and interstitial mediated methods. It was found that the vacancy mediated diffusion which is associated with the fast diffusion of many other species in germanium exhibits a total barrier of 5.8 eV. Interstitial-mediated diffusion had a total barrier for migration of 3.4 eV in the neutral and singly negative charge states, 3.2 eV for the positive charge state, but a formation barrier of 4.1 eV. Thus the barrier for interstitial-mediated diffusion is dominated by the formation energy of the self-interstitial.  相似文献   
10.
A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.  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