全文获取类型
收费全文 | 14045篇 |
免费 | 1308篇 |
国内免费 | 416篇 |
专业分类
化学 | 6579篇 |
晶体学 | 29篇 |
力学 | 1144篇 |
综合类 | 58篇 |
数学 | 5391篇 |
物理学 | 2568篇 |
出版年
2023年 | 188篇 |
2022年 | 323篇 |
2021年 | 405篇 |
2020年 | 658篇 |
2019年 | 484篇 |
2018年 | 435篇 |
2017年 | 396篇 |
2016年 | 657篇 |
2015年 | 613篇 |
2014年 | 712篇 |
2013年 | 1079篇 |
2012年 | 723篇 |
2011年 | 749篇 |
2010年 | 507篇 |
2009年 | 777篇 |
2008年 | 722篇 |
2007年 | 786篇 |
2006年 | 662篇 |
2005年 | 529篇 |
2004年 | 504篇 |
2003年 | 468篇 |
2002年 | 405篇 |
2001年 | 386篇 |
2000年 | 336篇 |
1999年 | 283篇 |
1998年 | 293篇 |
1997年 | 225篇 |
1996年 | 230篇 |
1995年 | 160篇 |
1994年 | 123篇 |
1993年 | 116篇 |
1992年 | 78篇 |
1991年 | 75篇 |
1990年 | 60篇 |
1989年 | 53篇 |
1988年 | 52篇 |
1987年 | 39篇 |
1986年 | 80篇 |
1985年 | 34篇 |
1984年 | 47篇 |
1983年 | 16篇 |
1982年 | 27篇 |
1981年 | 29篇 |
1980年 | 20篇 |
1979年 | 36篇 |
1978年 | 41篇 |
1977年 | 41篇 |
1976年 | 40篇 |
1975年 | 15篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 873 毫秒
151.
Robyn Pierce Kaye Stacey 《International Journal of Computers for Mathematical Learning》2004,9(1):59-93
This article suggests a framework to organise a cluster of variables that are associated with students' effective use of computer algebra systems (CAS) in mathematics learning. Based on a review of the literature and from the authors' own teaching experience, the framework identifies the main characteristics of students' interactions with CAS technology and how these may be used to monitor students' developing use of CAS; from this, the framework may be used to plan teaching in order to gain greater benefit from the availability of CAS. Four case studies describing students' development over a semester are reported. These demonstrate a variety of combinations of technical competencies and personal attributes. They indicate the importance of both the technical and personal aspects but suggest that negative attitudes rather than technical difficulties can limit the effective use of CAS. Finally practical suggestions are given for teaching strategies which may promote effective use of CAS.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献
152.
本文讨论延迟微分方程单支方法的非线性稳定性 .对于 Kα,β,γ类非线性延迟微分方程 ,我们证明带有线性插值的 G( c,p,q) -代数稳定的单支方法当 c≤ 1时是 GR( p/2 ,q/2 ) -稳定及弱 GAR( p/2 ,q/2 ) -稳定的 ,当 c<1时是 GAR( p/2 ,q/2 ) -稳定的 .最后的数值试验表明了上述结论的正确性 . 相似文献
153.
Periodica Mathematica Hungarica - 相似文献
154.
Joel Tellinghuisen 《Journal of Molecular Spectroscopy》2004,226(2):137-145
Heavily overlapped, or congested spectra often display much structure but few individual “lines.” Methods have been devised for analyzing such spectra through nonlinear least-squares fitting of the intensity as a function of wavelength or wavenumber. Such total spectrum fitting (TSF) methods are examined statistically for a simple diatomic model and compared with the standard “measure-assign-fit” (MAF) approach in use since the dawn of spectroscopy. Monte Carlo computations on typically 1000 synthetic spectra at a time verify that the predictions of the variance-covariance matrix are reliable under many circumstances. However in regions where the P and R branches double up, the predicted standard errors in the key spectroscopic constants rise sharply and greatly exceed estimates from the Monte Carlo ensemble statistics. In the same regions, the MAF method actually gives better precision. However, for imperfectly overlapped R and P branches, the MAF standard errors are typically three times larger than the TSF values; moreover, the MAF statistical errors are dwarfed by bias. The TSF approach, while clearly superior in these tests, has a practical drawback: it, too, can give significant bias if the spectra are analyzed with an incorrect model, as illustrated here through calculations employing the wrong function to describe the spectral lineshape. 相似文献
155.
N. A. Anikin A. S. Mendkovich M. B. Kuzminskiy A. M. Andreev 《Russian Chemical Bulletin》2008,57(2):428-430
A new fast computational method for mass calculations of docking complexes by the AM1/PM3 semiempirical methods is proposed.
The computation time is shortened by at least an order of magnitude compared to alternative schemes of quantum chemical calculations.
The root-mean-square deviation of the AM1 calculated energies of formation of complexes from the results obtained by conventional
diagonalization procedure is at most 0.4 kcal mol−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 418–420, February, 2008. 相似文献
156.
In this paper an automatic technique for handling discontinuous IVPs when they are solved by means of adaptive Runge–Kutta codes is proposed. This technique detects, accurately locates and passes the discontinuities in the solution of IVPs by using the information generated by the code along the numerical integration together with a continuous interpolant of the discrete solution. A remarkable feature is that it does not require additional information on the location of the discontinuities. Some numerical experiments are presented to illustrate the reliability and efficiency of the proposed algorithms. 相似文献
157.
158.
159.
大学物理实验的双任务教学方法初探 总被引:5,自引:1,他引:4
为搭建课程改革与学习效果之间的桥梁,在大学物理实验中引入了双任务教学方法.本文介绍了双任务教学法的概念、优点及具体实施方法. 相似文献
160.
M. A. Noor 《Journal of Optimization Theory and Applications》2004,121(2):385-395
In this paper, we suggest and analyze some iterative methods for solving nonconvex variational inequalities using the auxiliary principle technique, the convergence of which requires either only pseudomonotonicity or partially relaxed strong monotonicity. Our proofs of convergence are very simple. As special cases, we obtain earlier results for solving general variational inequalities involving convex sets. 相似文献