全文获取类型
收费全文 | 11346篇 |
免费 | 1196篇 |
国内免费 | 1447篇 |
专业分类
化学 | 7683篇 |
晶体学 | 214篇 |
力学 | 260篇 |
综合类 | 149篇 |
数学 | 2309篇 |
物理学 | 3374篇 |
出版年
2024年 | 27篇 |
2023年 | 126篇 |
2022年 | 271篇 |
2021年 | 346篇 |
2020年 | 371篇 |
2019年 | 376篇 |
2018年 | 345篇 |
2017年 | 384篇 |
2016年 | 430篇 |
2015年 | 391篇 |
2014年 | 629篇 |
2013年 | 918篇 |
2012年 | 661篇 |
2011年 | 690篇 |
2010年 | 539篇 |
2009年 | 681篇 |
2008年 | 788篇 |
2007年 | 752篇 |
2006年 | 653篇 |
2005年 | 556篇 |
2004年 | 544篇 |
2003年 | 482篇 |
2002年 | 672篇 |
2001年 | 327篇 |
2000年 | 301篇 |
1999年 | 253篇 |
1998年 | 233篇 |
1997年 | 205篇 |
1996年 | 200篇 |
1995年 | 156篇 |
1994年 | 125篇 |
1993年 | 94篇 |
1992年 | 85篇 |
1991年 | 69篇 |
1990年 | 50篇 |
1989年 | 29篇 |
1988年 | 32篇 |
1987年 | 25篇 |
1986年 | 34篇 |
1985年 | 28篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 25篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
51.
We demonstrate the potential of femtosecond two-color pulse interferometry for in vitro optical glucose monitoring, by dispersion of the group refractive index in a glucose solution sample with respect to a red-color
light and a blue-color light. By comparison with femtosecond one-color pulse interferometry, the basic performance of the
present system with regard to sensitivity, quantitativeness, and tolerance to surrounding disturbances, is evaluated. The
resulting accuracy and precision of glucose determination are 77 and 118mg/dl for 10-mm-sample-thickness, respectively. This
near-common-path configuration of the two-color pulse light provides good stability to fluctuations of sample temperature,
which is important in clinical applications. Considering the performance of femtosecond two-color pulse interferometry as
an optical glucose sensor, a suitable measurement site for in vivo optical glucose monitoring is discussed. 相似文献
52.
Eckhard Steffen 《Discrete Mathematics》2004,280(1-3):191-214
Cubic bridgeless graphs with chromatic index four are called uncolorable. We introduce parameters measuring the uncolorability of those graphs and relate them to each other. For k=2,3, let ck be the maximum size of a k-colorable subgraph of a cubic graph G=(V,E). We consider r3=|E|−c3 and
. We show that on one side r3 and r2 bound each other, but on the other side that the difference between them can be arbitrarily large. We also compare them to the oddness ω of G, the smallest possible number of odd circuits in a 2-factor of G. We construct cyclically 5-edge connected cubic graphs where r3 and ω are arbitrarily far apart, and show that for each 1c<2 there is a cubic graph such that ωcr3. For k=2,3, let ζk denote the largest fraction of edges that can be k-colored. We give best possible bounds for these parameters, and relate them to each other. 相似文献
53.
Pingan Zeng Jiaquan Liu Yuxia Guo 《Journal of Mathematical Analysis and Applications》2004,300(1):102-128
In this paper, by using the Morse index theory for strongly indefinite functionals developed in [Nonlinear Anal. TMA, in press], we compute precisely the critical groups at the origin and at infinity, respectively. The abstract theorems are used to study the existence (multiplicity) of nontrivial periodical solutions for asymptotically wave equation and beam equation with resonance both at infinity and at zero. 相似文献
54.
岳华 《数学的实践与认识》2003,33(6):96-104
本文证明了可分无穷维 Hilbert空间上每个有界线性算子均可写成两个强不可约算子之和 .这回答了文献 [9]中提出一个公开问题 相似文献
55.
In this paper, by the use of a fixed point theorem, many new necessary and sufficient conditions for the existence of positive solutions in C[0,1]∩C1[0,1]∩C2(0,1) or C[0,1]∩C2(0,1) are presented for singular superlinear and sublinear second-order boundary value problems. Singularities at t=0, t=1 will be discussed. 相似文献
56.
57.
58.
用迈克耳逊干涉仪测量气体折射率的误差的研究 总被引:1,自引:0,他引:1
研究在用迈克尔逊干涉仪测量气体折射率时存在的系统和方法误差,提出了误差修正方法。 相似文献
59.
Infrared and nuclear magnetic resonance (NMR) spectroscopies have been applied for quantitative comparison on unsaturated bonds in tetrafluoroethylene (TFE)-propylene (P)-vinylidene fluoride (VdF) terpolymers. These spectroscopies have led to consistent results while they are based on completely different principles. It is shown that the absolute concentration can be evaluated from NMR measurements. The behavior of unsaturation has been discussed in terms of after-treatment such as wet and dry treatments. The result obtained here can give the important information to improve the performance of fluoroelastomer based on TFE-P-VdF terpolymers. 相似文献
60.
D. Sasireka E. Palaniyandi K. Iyakutti 《International journal of quantum chemistry》2004,99(3):142-152
Local lattice relaxation of substitutional donors in silicon investigated using self‐consistent multiple scattering Xα (MSXα) method within the framework of the standard muffin‐tin potential approximation is extended to substitutional donors in germanium and substitutional acceptors in both silicon and germanium. Incorporating the effect of lattice relaxation surrounding the impurity makes the model suitable for both shallow and deep levels. Chemical trends of some aspects of impurity states, such as local lattice relaxation and charge transfer, of the impurities both in silicon and germanium are inferred. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献