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   15541篇
  免费   828篇
  国内免费   28篇
电工技术   166篇
综合类   43篇
化学工业   3346篇
金属工艺   308篇
机械仪表   315篇
建筑科学   685篇
矿业工程   45篇
能源动力   503篇
轻工业   1233篇
水利工程   124篇
石油天然气   51篇
无线电   1115篇
一般工业技术   2970篇
冶金工业   2249篇
原子能技术   117篇
自动化技术   3127篇
  2023年   165篇
  2022年   359篇
  2021年   574篇
  2020年   374篇
  2019年   380篇
  2018年   496篇
  2017年   461篇
  2016年   533篇
  2015年   465篇
  2014年   594篇
  2013年   1061篇
  2012年   973篇
  2011年   1158篇
  2010年   807篇
  2009年   749篇
  2008年   790篇
  2007年   776篇
  2006年   582篇
  2005年   504篇
  2004年   372篇
  2003年   381篇
  2002年   339篇
  2001年   213篇
  2000年   186篇
  1999年   207篇
  1998年   215篇
  1997年   186篇
  1996年   186篇
  1995年   177篇
  1994年   154篇
  1993年   150篇
  1992年   119篇
  1991年   74篇
  1990年   122篇
  1989年   116篇
  1988年   80篇
  1987年   93篇
  1986年   101篇
  1985年   100篇
  1984年   88篇
  1983年   76篇
  1982年   96篇
  1981年   90篇
  1980年   71篇
  1979年   70篇
  1978年   62篇
  1977年   74篇
  1976年   61篇
  1975年   45篇
  1974年   41篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
A model has been proposed to explain the failure of the original BMS10-39 epoxy paint on upper vertical surfaces in B-52 fuel tanks. The model involves interaction of the paint with DIEGME, a fuel system ice inhibitor (FSII) in jet fuel, that is distilled from the liquid fuel. In this communication, distillation experiments used to support the model are refined to better match the mass transfer of vapor from fuel in a B-52 fuel tank at close to room temperature. The interaction of these lower temperature distillates with the paint affirms the earlier model. On the basis of these experiments it is proposed that paint failure may be controlled or eliminated by reducing the level of DIEGME in the fuel. Proposed changes in military jet fuel composition are detailed.  相似文献   
3.
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   
4.
Comments that a critical element in the final report of the American Psychological Association (APA) Task Force on the Victims of Crime and Violence may be lost simply because of the enormity and complexity of the issues involved. The real nature of the victim's emotional experience is often not directly addressed by researchers or service providers in the mental health community. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
6.
A 1% Pd catalyst (38% dispersion) was prepared by impregnating a γ-alumina with palladium acetylacetonate dissolved in acetone. The behaviour of this catalyst in oxidation and steam reforming (SR) of propane was investigated. Temperature-programmed reactions of C3H8 with O2 or with O2 + H2O were carried out with different stoichiometric ratios S(S =[O2]/5[C3H8]). The conversion profiles of C3H8 for the reaction carried out in substoichiometry of O2 (S < 1) showed two discrete domains of conversion: oxidation at temperatures below 350°C and SR at temperatures above 350°C. The presence of steam in the inlet gases is not necessary for SR to occur: there is sufficient water produced in the oxidation to form H2 and carbon oxides by this reaction. Contrary to what was observed with Pt, an apparent deactivation between 310 and 385°C could be observed with Pd in oxidation. This is due to a reduction of PdOx into Pd0, which is much less active than the oxide in propane oxidation. Steam added to the reactants inhibits oxidation while it prevents the reduction of PdOx into Pd0. Compared to Pt and to Rh, Pd has a higher thermal resistance: no deactivation occurred after treatment up to 700°C and limited deactivation after treatment up to 900°C, provided that the catalyst is maintained in an oxygen-rich atmosphere during the cooling.  相似文献   
7.
8.
9.
In this article, we present a detailed theoretical analysis and a prototype implementation of a family of cameras designed with the explicit goal of detecting and removing interfering dynamic occluders in real time, during live capture, as opposed to fixing the resulting artifacts a posteriori. Such an early-acquisition approach improves efficiency: more valid samples are acquired faster without worrying about moving occluders. One option for designing a camera to be unaffected by moving occluders is to sample through the occluder, but true x-ray-like vision is technically impractical. Another option is to sample around the occluder using a camera with a large effective aperture, but such an approach requires a bulky acquisition device. Yet another possibility of sampling around an occluder is to rely on second and higher order reflected rays that indirectly sample surfaces not directly visible. However, devising an acquisition device sufficiently sensitive and efficient to capture large environments using reflected rays will remain challenging for the foreseeable future.  相似文献   
10.
We study a 3-band model of CuO2 with “bare bones” interactions: hopping from copper ions to nearest-neighbor oxygenst pd only, a two-body interaction on the copper ionsU dd only, and an overlap copper-oxygen parameter λpd. In the limitt pdU dd 1/2→∞, t*=t pd 2/2U dd is the unit of energy with 8λpd 2 as the only parameter of significance. If the two-body interaction is invariant under particle-hole interchange, the low-lying states (energy O(t*)) can be described by conserved particles and can all be classified. They are quite distinct from the high-lying states (energies O(U dd)). The dynamics of the conserved fermion-like elementary particles are well described by a modifiedt-J model with extended hopping and nearest-neighbor superexchange attraction. This is a scenario known to be favorable to high-temperature superconductivity, but it must be noted that both the hopping range and the exchange are functions of 8λpd 2. Moreover, if the Hamiltonian isnot invariant under particle-hole interchange the dynamics becomes much more complex and possibly more inimical to high-temperature superconductivity. This may provide an explanation for the deleterious effect on superconductivity of very small concentrations of certain impurities.  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