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   1544篇
  免费   156篇
  国内免费   101篇
化学   105篇
力学   173篇
综合类   44篇
数学   1272篇
物理学   207篇
  2023年   9篇
  2022年   19篇
  2021年   42篇
  2020年   36篇
  2019年   35篇
  2018年   30篇
  2017年   59篇
  2016年   72篇
  2015年   29篇
  2014年   91篇
  2013年   105篇
  2012年   88篇
  2011年   79篇
  2010年   95篇
  2009年   105篇
  2008年   88篇
  2007年   94篇
  2006年   107篇
  2005年   84篇
  2004年   54篇
  2003年   63篇
  2002年   57篇
  2001年   53篇
  2000年   35篇
  1999年   36篇
  1998年   35篇
  1997年   33篇
  1996年   24篇
  1995年   31篇
  1994年   17篇
  1993年   16篇
  1992年   5篇
  1991年   10篇
  1990年   12篇
  1989年   7篇
  1988年   10篇
  1987年   3篇
  1986年   3篇
  1985年   8篇
  1984年   3篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1959年   1篇
  1957年   1篇
排序方式: 共有1801条查询结果,搜索用时 31 毫秒
51.
High‐performance liquid chromatography coupled with photodiode array detection has been extensively applied in many fields and the peaks among the analyzed samples can be shifted due to the variations of instrumental and experimental conditions. In multivariate analysis, retention time alignment is an important pretreatment step. Hence, the shifted peaks in high‐performance liquid chromatography coupled with photodiode array detection three‐dimensional spectra should be aligned for further analysis. Being motivated by this purpose, the interval correlated shifting method combined with the proposed data arrangement methods are recommended and employed on high‐performance liquid chromatography coupled with photodiode array detection data as a demonstration. We validate the alignment performance of the proposed method through comparison the consistency of the retention time before and after alignment. The obtained results demonstrated that the proposed method is capable of successful aligning the employed data. Additionally, the interval correlated shifting method combined with the data arrangement modes is implemented in an easy‐to‐use graphical user interface environment and so can be operated easily by users not familiar with programming languages.  相似文献   
52.
In sensory psychophysics reaction time is a measure of the stochastic latency elapsed from stimulus presentation until a sensory response occurs as soon as possible. A random multiplicative model of reaction time variability is investigated for generating the reaction time probability density functions. The model describes a generic class of hyperbolic functions by Piéron?s law. The results demonstrate that reaction time distributions are the combination of log-normal with power law density functions. A transition from log-normal to power law behavior is found and depends on the transfer of information in neurons. The conditions to obtain Zipf?s law are analyzed.  相似文献   
53.
In this paper, we take the parabolic equation with periodic boundary conditions as a model to present a spectral method with the Fourier approximation in spatial and single/multi-interval Legendre Petrov–Galerkin method in time. For the single interval spectral method in time, we obtain the optimal error estimate in L 2-norm. For the multi-interval spectral method in time, the L 2-optimal error estimate is valid in spatial. Numerical results show the efficiency of the methods.  相似文献   
54.
本文我们讨论求凸连续函数的零点的区间割线法 ,所构造的方法简捷、实用 ,且具有较高的收敛效率 (三次函数计值 ,为三阶收敛 ).  相似文献   
55.
Safe bounds in linear and mixed-integer linear programming   总被引:1,自引:0,他引:1  
Current mixed-integer linear programming solvers are based on linear programming routines that use floating-point arithmetic. Occasionally, this leads to wrong solutions, even for problems where all coefficients and all solution components are small integers. An example is given where many state-of-the-art MILP solvers fail. It is then shown how, using directed rounding and interval arithmetic, cheap pre- and postprocessing of the linear programs arising in a branch-and-cut framework can guarantee that no solution is lost, at least for mixed-integer programs in which all variables can be bounded rigorously by bounds of reasonable size. Mathematics Subject Classification (2000):primary 90C11, secondary 65G20  相似文献   
56.
Continuity of Effect Algebra Operations in the Interval Topology   总被引:1,自引:0,他引:1  
We study the continuity of and of effect algebras in the interval topology, and present several examples of effect algebras with interesting properties.  相似文献   
57.
We consider smooth multimodal maps which have finitely many non-flat critical points. We prove the existence of real bounds. From this we obtain a new proof for the non-existence of wandering intervals, derive extremely useful improved Koebe principles, show that high iterates have `negative Schwarzian derivative' and give results on ergodic properties of the map. One of the main complications in the proofs is that we allow to have inflection points.

  相似文献   

58.
There are mainly two approaches to the multifractal analysis of measures. The first one, which is used in applications and in studying problems arising from dynamical systems, uses a hierarchy of boxes. The second one, which is more satisfactory from the viewpoint of geometric measure theory, uses more intrinsicconcepts. This article is an account of a work by J. Barral, F. Ben Nasr, and J. Peyriere [3] which pro-vides a bridge between these two theories.  相似文献   
59.
P. Kabaila 《Acta Appl Math》2003,78(1-3):185-192
We consider the problem of constructing a 1– upper confidence limit for the scalar parameter 0 in the presence of the nuisance parameter vector 0, when the data are discrete. The 'profile plug-in' upper confidence limit is introduced by Kabaila and Lloyd. This confidence limit is based on computing a P-value from an estimator of 0, replacing the nuisance parameter by the profile maximum likelihood estimate for known, and equating to . Theoretical and numerical evidence for the good coverage properties of this confidence limit is presented by Kabaila and Lloyd. An upper confidence limit should be assessed not only by its coverage properties but also by how large this confidence limit is. We measure how large the profile plug-in upper limit is by using a large sample approximation to it. This large sample approximation is used to delineate further the good properties of this confidence limit.  相似文献   
60.
区间数的排序方法研究   总被引:27,自引:1,他引:26  
指出献^[3-5]所定义的用于区间数排序的可能度存在的不足,分别给出了刻画区间数大小比较的相对优势度的定义和模糊互补矩阵排序的一种新方法。在此基础上,给出了区间数的一种排序方法。  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