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   952篇
  免费   76篇
  国内免费   66篇
化学   310篇
晶体学   3篇
力学   56篇
综合类   16篇
数学   557篇
物理学   152篇
  2024年   2篇
  2023年   16篇
  2022年   32篇
  2021年   27篇
  2020年   31篇
  2019年   18篇
  2018年   19篇
  2017年   36篇
  2016年   43篇
  2015年   24篇
  2014年   44篇
  2013年   70篇
  2012年   32篇
  2011年   50篇
  2010年   44篇
  2009年   46篇
  2008年   43篇
  2007年   57篇
  2006年   51篇
  2005年   44篇
  2004年   54篇
  2003年   43篇
  2002年   23篇
  2001年   29篇
  2000年   31篇
  1999年   23篇
  1998年   20篇
  1997年   24篇
  1996年   17篇
  1995年   12篇
  1994年   11篇
  1993年   7篇
  1992年   10篇
  1991年   8篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   2篇
  1984年   6篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   3篇
  1979年   4篇
  1978年   3篇
  1977年   4篇
  1971年   1篇
  1968年   1篇
排序方式: 共有1094条查询结果,搜索用时 15 毫秒
131.
The complete amino acid sequence of β-momorcharin, a ribosome-inactivating protein from the seeds of Momordica charantia Linn (Cucurbitaceae) has been determined. This has been done by the sequence analysis of peptides obtained by enzymatic digestion with trypsin, chymotrypsin and S. aureus V8 protease, as well as by chemical cleavage with BNPS-skatole. The protein consists of 249 amino acid residues containing one asparagine - linked sugar group attached to the site of Asn 5 1 and has a calculated relative molecular mass of 28,452 Da without addition of the carbohydrate. Comparison of this sequence with those of trichosanthin and other ribosome-inactivating proteins from different species of plants shows a significant homology with each other. Regarding the similarity of their biological properties, an active domain of these proteins has been predicted here.  相似文献   
132.
The novolac-based resins used as positive-tone photoresists are frequently etched in an oxygen plasma. It is desirable to have a predictive model of the photoresist etch rate but, for process improvement, control, and analysis, the development of a rigorous mechanistic model is impractical. Instead, a simplified mechanistic model is derived, here, according to the method proposed by Hougen and Watson for the study of fluid–solid interactions. This model derivation method is employed in order to arrive at a functional form that represents chemical etching of the resist by oxygen radicals, assisted by the plasma ion flux. Values for model parameters are determined from process data by nonlinear regression. The quality of the model fit to the data is tested statistically.  相似文献   
133.
In this paper, we establish some differential identities and obtain some Sturm comparison theorems for the second order nonlinear differential equation by using them.and generalize some classicial Sturm comparison theorems.  相似文献   
134.
In the present paper, the author shows that the predictor/multi‐corrector (PMC) time integration for the advection–diffusion equations induces numerical diffusivity acting only in the streamline direction, even though the equations are spatially discretized by the conventional Galerkin finite element method (GFEM). The transient 2‐D and 3‐D advection problems are solved with the PMC scheme using both the GFEM and the streamline upwind/Petrov Galerkin (SUPG) as the spatial discretization methods for comparison. The solutions of the SUPG‐PMC turned out to be overly diffusive due to the additional PMC streamline diffusion, while the solutions of the GFEM‐PMC were comparatively accurate without significant damping and phase error. A similar tendency was seen also in the quasi‐steady solutions to the incompressible viscous flow problems: 2‐D driven cavity flow and natural convection in a square cavity. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
135.
Exact L 2 Small Balls of Gaussian Processes   总被引:3,自引:3,他引:0  
We prove a comparison theorem extending Li(6) and develop a complex-analytic approach to treat L 2 small ball probabilities of Gaussian processes. We demonstrate the techniques for the m-times integrated Brownian motions and in examples where one can not apply Li comparison theorem.  相似文献   
136.
In this paper, we investigate the periodic boundary value problems for nonlinear first order functional differential equations. By establishing a new comparison result, criteria on the existence of maximal and minimal solutions are obtained.  相似文献   
137.
Cavitated bifurcation for composed compressible hyper-elastic materials   总被引:4,自引:0,他引:4  
The cavitated bifurcation problem in a solid sphere composed of two compressible hyper-elastic materials is examined. The bifurcation solution for the composed sphere under a uniform radial tensile boundary dead-load is obtained. The bifurcation curves and the stress contributions subsequent to the cavitation are given. The right and left bifurcation as well as the catastrophe and concentration of stresses are analyzed. The stability of solutions is discussed through an energy comparison. Project supported by the National Natural Science Foundation of China (No. 19802012).  相似文献   
138.
139.
This paper concerns the optimal stopping problem for discrete time multiparameter stochastic processes with the index set Nd. In the classical optimal stopping problems, the comparisons between the expected reward of a player with complete foresight and the expected reward of a player using nonanticipating stop rules, known as prophet inequalities, have been studied by many authors. Ratio comparisons between these values in the case of multiparameter optimal stopping problems are studied by Krengel and Sucheston (1981) [9] and Tanaka (2007, 2006) [14] and [15]. In this paper an additive comparison in the case of finite stage multiparameter optimal stopping problems is given.  相似文献   
140.
The application of Bayesian methods in cosmology and astrophysics has flourished over the past decade, spurred by data sets of increasing size and complexity. In many respects, Bayesian methods have proven to be vastly superior to more traditional statistical tools, offering the advantage of higher efficiency and of a consistent conceptual basis for dealing with the problem of induction in the presence of uncertainty. This trend is likely to continue in the future, when the way we collect, manipulate and analyse observations and compare them with theoretical models will assume an even more central role in cosmology.

This review is an introduction to Bayesian methods in cosmology and astrophysics and recent results in the field. I first present Bayesian probability theory and its conceptual underpinnings, Bayes' Theorem and the role of priors. I discuss the problem of parameter inference and its general solution, along with numerical techniques such as Monte Carlo Markov Chain methods. I then review the theory and application of Bayesian model comparison, discussing the notions of Bayesian evidence and effective model complexity, and how to compute and interpret those quantities. Recent developments in cosmological parameter extraction and Bayesian cosmological model building are summarised, highlighting the challenges that lie ahead.  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