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   3516篇
  免费   262篇
  国内免费   5篇
工业技术   3783篇
  2023年   41篇
  2022年   35篇
  2021年   111篇
  2020年   96篇
  2019年   117篇
  2018年   182篇
  2017年   163篇
  2016年   166篇
  2015年   156篇
  2014年   219篇
  2013年   454篇
  2012年   216篇
  2011年   253篇
  2010年   272篇
  2009年   202篇
  2008年   134篇
  2007年   89篇
  2006年   48篇
  2005年   15篇
  2004年   27篇
  2003年   28篇
  2002年   33篇
  2001年   26篇
  2000年   37篇
  1999年   22篇
  1998年   23篇
  1997年   24篇
  1996年   24篇
  1995年   26篇
  1994年   21篇
  1993年   27篇
  1992年   23篇
  1991年   14篇
  1990年   13篇
  1989年   17篇
  1988年   14篇
  1986年   13篇
  1985年   22篇
  1984年   31篇
  1983年   20篇
  1982年   22篇
  1981年   39篇
  1980年   29篇
  1979年   23篇
  1978年   27篇
  1977年   23篇
  1976年   33篇
  1975年   25篇
  1974年   21篇
  1973年   25篇
排序方式: 共有3783条查询结果,搜索用时 734 毫秒
81.
82.
Widespread use of GPS and similar technologies makes it possible to collect extensive amounts of trajectory data. These data sets are essential for reasonable decision making in various application domains. Additional information, such as events taking place along a trajectory, makes data analysis challenging, due to data size and complexity. We present an integrated solution for interactive visual analysis and exploration of events along trajectories data. Our approach supports analysis of event sequences at three different levels of abstraction, namely spatial, temporal, and events themselves. Customized views as well as standard views are combined to form a coordinated multiple views system. In addition to trajectories and events, we include on-the-fly derived data in the analysis. We evaluate our integrated solution using the IEEE VAST 2015 Challenge data set. A successful detection and characterization of malicious activity indicate the usefulness and efficiency of the presented approach.  相似文献   
83.
Structural optimization based on the shakedown theory is a powerful and promising technique. However, due to the nonlinearities of physical materials and the number of variable loads in real structures, it is computationally complex and time-consuming. To simplify the occurring non-linear, non-convex optimization problems, the paper suggests reducing the number of yield conditions. The so-called a yield criterion of the mean (integral yield condition) is analysed and explained in detail, which allows taking into account one yield condition for the entire finite element instead of multiple point-wise conditions. This approach shows promising results in numerical application to the optimization of a circular plate, considering a possibility of employing the yield criteria of the mean or pointwise yield conditions in different areas of the plate in particular. The methods applied are based on the assumptions of perfect plasticity and small deformations.  相似文献   
84.
Slow and fast diffusion effects in image processing   总被引:3,自引:0,他引:3  
A mathematical model for a nonlinear image multiscale analysis is studied. Processing of an image is based on a solution of the strongly nonlinear parabolic partial differential equation, which can degenerate depending on values of the greylevel intensity function. The governing PDE is a generalization of the regularized (in the sense of Catté, Lions, Morel and Coll) Perona-Malik anisotropic diffusion equation. We present numerical techniques for solving the suggested initial-boundary value problem and also existence and convergence results. Numerical experiments are discussed. Received: 6 May 1998 / Accepted: 27 July 2000  相似文献   
85.
In the paper we introduce a relation on the class of monounary algebras by means of -homomorphisms. It is a quasiorder. We take a subclass of containing monounary algebras satisfying the property We characterize algebras in by the notions of a degree and properties of their -endomorphisms. We apply the results to finite monounary algebras. Supported by grant VEGA 1/0161/03  相似文献   
86.
Attempts to carry out the hydroformylation of allyldiethylamine homogeneously catalyzed by rhodium complexes led to unexpected formation of N,N,N,N-tetraethyl-1,4-diaminobutane and 4-(diethylamino)-1-butanole as final products. The role of the catalyst on the product formation and the reaction mechanism are briefly discussed.  相似文献   
87.
Contents By applying the quaternion variant of the Cauchy integral formula the general solution of the direct magnetic problem is derived. The applicability of the method presented here is shown by investigating and calculating the outer field of a analytically magnetized sphere.
Die Lösung der direkten Aufgabe der Magnetik mit Hilfe des Quaternionen Analogons des 3-D Cauchy-Riemann Systems
Übersicht Die allgemeine Lösung der direkten Aufgabe der Magnetik wird mit Hilfe der Quaternionenvariante des Cauchy-Integrals abgeleitet. Die Anwendbarkeit der vorgestellten, Methode wird am Beispiel des berechneten äußeren magnetischen Feldes einer analytisch magnetisierten Kugel untersucht.
  相似文献   
88.
High-purity, fine-grained oxide ceramic powders that are commonly used for ZnO-based varistors were synthesized by means of the reaction spray process. Processing steps included formation of the solutions of zinc nitrate and/or certain metal additives and spraying of the solution into a heated reaction column using a two-phase nozzle. After water evaporation from the droplets, the precursor salts were decomposed at elevated temperatures (up to 1473 K) in order to obtain homogeneous oxide powders with complex compositions corresponding to the final multicomponent varistor system. The decomposition behaviour of the precursors, as well as the characteristics of the resulting powders: crystallinity, phase composition, particle shape, morphology and particle-size distribution, were examined. It was shown that the characteristics of the reaction spray-derived powders can be controlled by adjusting the system and the solutions parameters.  相似文献   
89.
Using a new design of helium-methane gas-flow detector of conversion electrons for Mössbauer spectroscopy, non-uniform nucleation of the primary -Fe-Co phase on both contact and free surfaces of the Ar(+H2) annealed amorphous Fe75Co9B16 alloy was observed in its early crystallization stage. In this state the amount of crystalline phase on the contact ribbon side surpasses that on the free one by a factor of three, whereas no traces of volume crystallization were observed in the transmission spectra. By applying ion implantation to both ribbon surfaces, a slight reduction of the crystalline phase contribution was found. Magnetic domain structure observations were performed in order to evaluate the influence of surface crystallization on magnetic properties.  相似文献   
90.
 The paper contains a review of some results concerning probability theory on MV algebras (laws of large numbers, central limit theorem, martingale convergence theorem). Also some algebraic and methodical aspects are discussed.  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