全文获取类型
收费全文 | 72567篇 |
免费 | 23374篇 |
国内免费 | 17033篇 |
专业分类
化学 | 45332篇 |
晶体学 | 940篇 |
力学 | 4991篇 |
综合类 | 45篇 |
数学 | 9482篇 |
物理学 | 52184篇 |
出版年
2024年 | 433篇 |
2023年 | 658篇 |
2022年 | 639篇 |
2021年 | 535篇 |
2020年 | 782篇 |
2019年 | 1315篇 |
2018年 | 1306篇 |
2017年 | 1948篇 |
2016年 | 2042篇 |
2015年 | 2253篇 |
2014年 | 2073篇 |
2013年 | 3811篇 |
2012年 | 4086篇 |
2011年 | 5631篇 |
2010年 | 9084篇 |
2009年 | 9345篇 |
2008年 | 3142篇 |
2007年 | 2657篇 |
2006年 | 2350篇 |
2005年 | 2754篇 |
2004年 | 3678篇 |
2003年 | 3047篇 |
2002年 | 2836篇 |
2001年 | 3107篇 |
2000年 | 2302篇 |
1999年 | 2507篇 |
1998年 | 2107篇 |
1997年 | 1916篇 |
1996年 | 2242篇 |
1995年 | 2701篇 |
1994年 | 2770篇 |
1993年 | 2841篇 |
1992年 | 2417篇 |
1991年 | 2076篇 |
1990年 | 1737篇 |
1989年 | 1842篇 |
1988年 | 1829篇 |
1987年 | 1121篇 |
1986年 | 1176篇 |
1985年 | 840篇 |
1984年 | 963篇 |
1982年 | 886篇 |
1981年 | 729篇 |
1980年 | 768篇 |
1979年 | 525篇 |
1978年 | 530篇 |
1977年 | 633篇 |
1976年 | 1041篇 |
1973年 | 436篇 |
1972年 | 532篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
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
993.
In the present paper, we prove that the Bernstein-Kantorovič operators have the ability of preserving translation property
in both C and Lp norms.
Supported (in part) by the NSFC(10471130,10371024) of PRC and the Natural Science Foundation (Y604003) of Zhejiang Province. 相似文献
994.
H. Ohta M. Kimata K. Koyama Y. Oshima M. Motokawa H. Nishikawa K. Kikuchi I. Ikemoto 《International Journal of Infrared and Millimeter Waves》2005,26(11):1525-1530
We have developed a new magneto-optical measurement system using a rotational cavity system equipped with a millimeter vector
network analyzer and a 14 T solenoid type super conducting magnet. The measurement can be performed in the transmission configuration
down to 1.6 K. The results of the precise angular dependence measurement of quasi-one-dimensional organic conductor (DMET)2I3 using the new system are shown, and its Fermi surface will be discussed in connection with the previous reports. 相似文献
995.
We consider solutions bifurcating from a spatially
homogeneous equilibrium under the assumption that the associated
linearization possesses continuous spectrum up to the imaginary
axis, for all values of the bifurcation parameter, and that a real
eigenvalue crosses the imaginary axis. For a model we investigate
the nonlinear stability of the trivial solution with respect to
spatially localized perturbations, prove the occurrence of a
pitchfork bifurcation of equilibria and the nonlinear stability of
the bifurcating equilibria, again with respect to spatially
localized perturbations. 相似文献
996.
997.
Elastic electron scattering on the exotic light nucleus28S is investigated in the plane wave Born approximation. The variation of the squared form factors of28S with momentum transfer is compared with that of32S. It is found that the behavior of the form factors near the second minimum (with a moderate momentum transfer) is sensitive
to the alteration of the charge density distribution of halo protons in28S. This indicates that elastic electron scattering can be a good probe of the structure of proton-halo nuclei. 相似文献
998.
999.
1000.
Liquid-liquid extraction of zirconium(IV) was investigated from dilute hydrochloric acid medium by salicyaldoxime (HA) in dichloromethane. The metal was spiked with 95Zr and analyzed by its radioactivity. The effects of different donors, like trioctyl phosphine oxide (TOPO), triphenyl phosphine oxide (TPPO), tributyl phosphine oxide (TBPO), tributyl phosphate (TBP), trioctyl amine (TOA) and Amberlite LA-2 were studied. The adduct formation constants for both binary species (metal-ligand) and ternary species (metal-ligand-donor) were also calculated form the distribution data.One of the authors (S.B.) thanks The University of Burdwan for providing senior research fellowship to her. She also wishes to thank Dr. D. Mukherjee and Dr. S. Bhattacharya, B.U. for their valuable suggestions. 相似文献