全文获取类型
收费全文 | 8179篇 |
免费 | 1375篇 |
国内免费 | 2813篇 |
专业分类
化学 | 6684篇 |
晶体学 | 192篇 |
力学 | 412篇 |
综合类 | 263篇 |
数学 | 1169篇 |
物理学 | 3647篇 |
出版年
2024年 | 14篇 |
2023年 | 40篇 |
2022年 | 202篇 |
2021年 | 233篇 |
2020年 | 224篇 |
2019年 | 194篇 |
2018年 | 218篇 |
2017年 | 273篇 |
2016年 | 231篇 |
2015年 | 319篇 |
2014年 | 354篇 |
2013年 | 563篇 |
2012年 | 542篇 |
2011年 | 596篇 |
2010年 | 564篇 |
2009年 | 638篇 |
2008年 | 754篇 |
2007年 | 661篇 |
2006年 | 647篇 |
2005年 | 638篇 |
2004年 | 507篇 |
2003年 | 427篇 |
2002年 | 432篇 |
2001年 | 471篇 |
2000年 | 555篇 |
1999年 | 287篇 |
1998年 | 177篇 |
1997年 | 155篇 |
1996年 | 118篇 |
1995年 | 129篇 |
1994年 | 117篇 |
1993年 | 120篇 |
1992年 | 109篇 |
1991年 | 76篇 |
1990年 | 84篇 |
1989年 | 73篇 |
1988年 | 71篇 |
1987年 | 72篇 |
1986年 | 54篇 |
1985年 | 34篇 |
1984年 | 45篇 |
1983年 | 39篇 |
1982年 | 46篇 |
1981年 | 35篇 |
1980年 | 29篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1976年 | 18篇 |
1974年 | 13篇 |
1965年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
We report on a new type of Fano effect, named as Andreev-Fano effect, in a hybrid normal-metal/supeeconductor (N/S) interferometer embedded with a quantum dot. Compared with the conventional Fano effect, AndreevFano effect has some new features related to the characteristics of Andreev reflection. In the Iinear response regime, the line shape is the square of the conventional Fano shape, while in the nonlinear transport, a sharp resonant structure is superposed on an expanded interference pattern, which is qualitatively different from the conventional Fano effect. The phase dependence of the hybrid N/S interferometer is also distinguished from those of all-N or all-S interferometers. 相似文献
22.
Poisson回归模型广泛应用于分析计数型数据 ,Dean&Lawless(1989)和Dean(1992 )讨论了非重复测量得到的计数型数据的偏大离差存在性的检验问题 .本文分别利用随机系数模型和对数非线性模型讨论了基于重复测量得到的计数型数据的偏大离差的检验问题 ,得到了检验的score统计量 . 相似文献
23.
Onofrio Mario Di Vincenzo Plamen Koshlukov Roberto La Scala 《Advances in Applied Mathematics》2006,37(4):541
In this paper we describe completely the involutions of the first kind of the algebra UTn(F) of n×n upper triangular matrices. Every such involution can be extended uniquely to an involution on the full matrix algebra. We describe the equivalence classes of involutions on the upper triangular matrices. There are two distinct classes for UTn(F) when n is even and a single class in the odd case.Furthermore we consider the algebra UT2(F) of the 2×2 upper triangular matrices over an infinite field F of characteristic different from 2. For every involution *, we describe the *-polynomial identities for this algebra. We exhibit bases of the corresponding ideals of identities with involution, and compute the Hilbert (or Poincaré) series and the codimension sequences of the respective relatively free algebras.Then we consider the *-polynomial identities for the algebra UT3(F) over a field of characteristic zero. We describe a finite generating set of the ideal of *-identities for this algebra. These generators are quite a few, and their degrees are relatively large. It seems to us that the problem of describing the *-identities for the algebra UTn(F) of the n×n upper triangular matrices may be much more complicated than in the case of ordinary polynomial identities. 相似文献
24.
25.
本文研究的问题是确定f(p,B)的值,也就是给定顶点数p和带宽B,求满足最大度不超过B的连通图的最小边数,本文给出了一些f(p,B)的值及相应极图。 相似文献
26.
27.
从江浙蝮蛇毒腺中抽提总RNA,RT-PCR进行体外扩增,获得江浙蝮蛇蛇毒蛋白C激活因子基因,克隆至pGEX-5X-3载体中,对3个重组克隆分别作DNA全序列分析,通过遗传密码推导出相应的氨基酸序列,与其它已知的丝氨酸复白酶蛇毒蛋白的氨基酸作比较,其中许多上氨基酸有很强的同源性,该基因的成功克隆,不仅推导出江浙蝮蛇蛇毒蛋白C激活因子的蛋白质序列,也为进一步开展江浙蝮蛇蛇毒蛋白C激活因子蛋白质工程的研究工作打下良好的基础。 相似文献
28.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
29.
30.
KunHuaLIN MaoPingSONG ChenXiaDU QiaoHongZHANG YangJieWU 《中国化学快报》2003,14(7):673-676
The cyclomercurated ferrocenylimines containing heterocyclic ring were prepared by the condensation of cyclomercuration of acylferrocene with the appropriate heterocyclic amine.This procedure provides an efficient method for the synthesis of cyclomerucurated ferrocenylimines containing heterocyclic ring which are difficultly synthesized by the conventional method.The reaction mechanism is proposed. 相似文献