首页 | 官方网站   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   1074篇
  免费   21篇
  国内免费   3篇
工业技术   1098篇
  2021年   9篇
  2019年   9篇
  2017年   8篇
  2016年   19篇
  2015年   17篇
  2014年   30篇
  2013年   36篇
  2012年   41篇
  2011年   43篇
  2010年   35篇
  2009年   36篇
  2008年   39篇
  2007年   45篇
  2006年   33篇
  2005年   38篇
  2004年   33篇
  2003年   32篇
  2002年   19篇
  2001年   18篇
  2000年   19篇
  1999年   26篇
  1998年   26篇
  1997年   17篇
  1996年   17篇
  1995年   17篇
  1994年   12篇
  1993年   13篇
  1992年   12篇
  1991年   15篇
  1990年   18篇
  1989年   10篇
  1988年   9篇
  1986年   9篇
  1984年   14篇
  1983年   11篇
  1982年   11篇
  1981年   11篇
  1980年   8篇
  1979年   11篇
  1978年   13篇
  1977年   13篇
  1976年   8篇
  1975年   14篇
  1974年   11篇
  1973年   18篇
  1972年   11篇
  1971年   10篇
  1970年   16篇
  1969年   9篇
  1968年   8篇
排序方式: 共有1098条查询结果,搜索用时 15 毫秒
91.
Project management in plant construction. Project management is a management concept increasingly employed in project execution both by industry and administration. There are variants to this management concept allowing it to be readily adapted to individual applications. Engineering companies are typically confronted with multi-project management tasks, i. e. they handle concurrently a great variety of projects differing in size, complexity, and duration. For each project, specialists from various disciplines of the company have to be coordinated across department lines and their performance channelled under project management leadership. Matrix project management lends itself particularly well to this task, the personality of the project manager playing a central role.  相似文献   
92.
93.
It is still a matter of debate at which time point faces are recognized as familiar, with some studies claiming a relatively early face recognition and others later effects of familiarity. The authors report on effects of famousness of depicted persons and stimulus repetition on intracranially recorded event-related potentials. Famousness resulted in an increased latency of the N200 component, as well as in an increased amplitude of a later long-lasting potential (N700). In contrast, repetition led to an increased amplitude of the N200 but no increase of its latency. They suppose that the recognition of faces becomes observable within the N200 latency range and that the increased N200 latency reflects a feature processing additional to the holistic face processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
•  Markets and central planning are alternative mechanisms for coordinating economic activity within economies and firms. A multi-level economics literature describes and contrasts the coordinating characteristics of markets and planning. While it assumes these characteristics reflect the perceptions and decisions of economic actors, this behavioural assumption has not been tested.  相似文献   
95.
Scanning transmission X-ray microscopy was used to investigate the speciation and spatial distribution of Co in a Co(II)-doped cement matrix. The aim of this study was to improve the understanding of the heavy metals immobilization process in cement on the molecular level. The Co-doped cement samples hydrated for 30 days with a Co loading of 5000 mg/kg were prepared under normal atmosphere to simulate conditions used for cement-stabilized waste packages. Co 2p(3/2) absorption edge signals were used to determine the spatial distributions of the metal species in the Co(II)-doped cement. The speciation of Co was determined by collecting near-edge X-ray absorption fine structure spectra. On the basis of the shape of the absorption spectra, it was found that Co(II) is partly oxidized to Co(III). The correlation, respectively the anticorrelation with elements such as Al, Si, and Mn, show that Co(II) is predominantly present as Co-hydroxide-like phase as well as Co-phyllosilicate, whereas Co(III) tends to be incorporated only into a CoOOH-like phase. Thus, this study suggests that thermodynamic calculations of Co(II)-immobilization by cementitious systems should take into consideration not only the solubility of Co(II)-hydroxides but also Co(III) phases.  相似文献   
96.
Diffracted image patterns from volume holograms that are used in volume holographic imaging systems (VHISs) are investigated. It is shown that, in VHISs, prior information about the shape and spectral properties of the diffracted patterns is important not only to determine the curvature and field of view of the image, but also for image registration and noise removal. A new methodology to study numerically and analytically the dependence of VHIS diffraction patterns with the hologram construction parameters and the readout wavelength is described. Modeling and experimental results demonstrate that, in most cases, VHIS diffracted shapes can be accurately represented by hyperbolas.  相似文献   
97.
The resolution dependence of spatial-spectral volume holographic imaging systems on angular and spectral bandwidth of nonuniform gratings is investigated. Modeling techniques include a combination of the approximate coupled-wave analysis and the transfer-matrix method for holograms recorded in absorptive media. The effective thickness of the holograms is used as an estimator of the resolution of the imaging systems. The methodology, which assists in the design and optimization of volume holographic simulation results based on our approach, are confirmed with experiments and show proof of consistency and usefulness of the proposed models.  相似文献   
98.
99.
An overview of existing approaches on assessing and evaluating the radiological situation in the late phase of a nuclear accident is given in this paper. Special attention is paid to the weak points of existing approaches and to problems to be solved in the future. Assessment of the radiological situation can be based on both monitoring data and model predictions. Approaches have been developed for many years in both categories and have meanwhile reached some kind of maturity and also operational applicability. Nevertheless, some areas exist where significant improvements could be achieved in the near future, e.g. by combining monitoring data and model predictions, by improving the modelling of urban areas or by improving existing radioecological models.  相似文献   
100.
Nitrogen organic compounds constitute a large class of aqueous pollutants. These compounds include not only azoic structures, nitrogen heterocycles, and nitrous groups but also amides and amines. This work consisted in studying the OH* induced oxidation of simple primary amines in dilute aqueous solution with special attention to mineralization of the nitrogen group as a function of the nature of the alpha-carbon. H2O2/UV and gamma-irradiation processes were used for the production of OH* radicals, and the molecules studied were one alpha-amino acid i.e., glycine (HOOCCH2NH2), and two primary amides i.e., acetamide (CH3CONH2) and oxamic acid (HOOCCONH2). It was shown that the oxidation of glycine leads to the formation of ammonia, whereas the acetamide molecule is first oxidized into oxamic acid ending in complete mineralization with production of nitrates. Reaction mechanisms are proposed which account for the observed inorganic nitrogen end product depending on the oxidation degree of the carbon atoms of the molecules. It follows that the present study will allow for prediction of the fate of nitrogen resulting from the oxidation of primary amino groups by OH* radicals.  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-23

京公网安备 11010802026262号