全文获取类型
收费全文 | 4200篇 |
免费 | 176篇 |
国内免费 | 228篇 |
专业分类
化学 | 1125篇 |
晶体学 | 9篇 |
力学 | 49篇 |
综合类 | 21篇 |
数学 | 2038篇 |
物理学 | 1362篇 |
出版年
2023年 | 22篇 |
2022年 | 90篇 |
2021年 | 94篇 |
2020年 | 64篇 |
2019年 | 55篇 |
2018年 | 72篇 |
2017年 | 72篇 |
2016年 | 59篇 |
2015年 | 51篇 |
2014年 | 77篇 |
2013年 | 263篇 |
2012年 | 150篇 |
2011年 | 336篇 |
2010年 | 243篇 |
2009年 | 468篇 |
2008年 | 439篇 |
2007年 | 361篇 |
2006年 | 377篇 |
2005年 | 231篇 |
2004年 | 116篇 |
2003年 | 81篇 |
2002年 | 190篇 |
2001年 | 142篇 |
2000年 | 118篇 |
1999年 | 71篇 |
1998年 | 76篇 |
1997年 | 40篇 |
1996年 | 63篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1959年 | 2篇 |
排序方式: 共有4604条查询结果,搜索用时 15 毫秒
101.
杨乐不等式的推广及加强 总被引:1,自引:0,他引:1
赵长健 《数学的实践与认识》2000,30(4)
本文首先利用凸函数基本不等式和平均值不等式推广并加强了杨乐不等式 ,然后利用 Jensen不等式给出了两个更为广泛的结果 . 相似文献
102.
Zusammenfassung. Der lokale–Polynom–Sch?tzer besteht darin, an eine Sequenz von aufeinanderfolgenden Datenpunkten lokal ein Polynom anzupassen
und damit zuf?llige Schwankungen in den Daten wegzugl?tten. Dieser Ansatz gewinnt in der nichtparametrischen Kurvensch?tzung
st?ndig an Bedeutung. Es wird gezeigt, wie die Herleitung einiger elementarer Eigenschaften dieses Handwerkszeuges des Datenanalytikers
einen Streifzug durch die lineare Algebra erforderlich macht.
Eingegangen am 27.03.1998 / Angenommen am 15.06.1998 相似文献
103.
The influence of a wall porosity on the pressure distribution in a curvilinear squeeze film bearing lubricated by a lubricant being a viscoplastic fluid of a Vo?adlo type is considered. 相似文献
104.
Daniel Macias Castillo 《Journal of Number Theory》2013,133(9):3007-3032
We discuss an explicit refinement of Rubin?s integral version of Stark?s conjecture. We prove that this refinement is a consequence of the relevant case of the Equivariant Tamagawa Number Conjecture of Burns and Flach, hence obtaining a full proof in several important cases. We also derive several explicit consequences of this refinement concerning the annihilation as Galois modules of ideal class groups by explicit elements constructed from the values of higher order derivatives of Dirichlet L-functions. We finally describe the relation between our approach and those found in recent work of Emmons and Popescu and of Buckingham. 相似文献
105.
In this paper, we prove a Hadamard property and Liouville type theorems for viscosity solutions of fully nonlinear elliptic partial differential equations with a gradient term, both in the whole space and in an exterior domain. 相似文献
106.
István Juhász 《Topology and its Applications》2011,158(18):2460-2462
In this short note I attempt to describe some of the most important contributions of Ken Kunen to set-theoretic topology together with some of the highlights of our personal relationship. 相似文献
107.
Sándor Zsuppán 《Journal of Mathematical Analysis and Applications》2011,382(2):856-863
In this paper we investigate the domain dependence of the inf-sup stability constant in the family of two-dimensional simply connected domains using its connection to the optimal constant figuring in Friedrichs? inequality for conjugate harmonic functions and the conformal mapping of the domain. A lower estimation of the inf-sup constant is also given in terms of the conformal mapping provided the boundary of the domain is smooth enough. We illustrate the results with several examples. 相似文献
108.
C. Mœglin 《Advances in Mathematics》2011,228(2):1068
This paper is about the pole of some Eisenstein series for classical groups over a number field. In a previous paper, we have shown how to normalize intertwining operators in such a way that they are holomorphic for positive parameters. Here we show that the image of such operators is (in the interesting cases) either 0 or an irreducible representation. This enables us to compute explicitly the residue of the Eisenstein series obtained from square integrable cohomological representations. At the end of the paper we give necessary and sufficient conditions in terms of Arthur?s data in order that a square integrable cohomological representation is cuspidal; the conditions are not totally satisfactory and we explain what we expect when Arthur?s results will be fully available. 相似文献
109.
Zhiting Jiang Qionglin Liang Yong Wang Xiaoying Zheng Lijun Pei Ting Zhang Yiming Wang Guoan Luo 《Biomedical chromatography : BMC》2011,25(7):767-774
Nutritional intervention is effective in reducing the risk of neural tube defects (NTDs). To determine the effects of nutritional supplementation on human metabolism, a metabonomic study was carried out on 96 women of reproductive age. Subjects with nutritional intervention were given fortified wheat flour (containing folic acid, vitamin B1, vitamin B2, ferric sodium edetate and zinc oxide) for 8 months. Serum metabolic fingerprinting was detected via ultraperformance liquid chromatography in tandem with time‐of‐flight mass spectrometry (UPLC‐TOF MS), and data acquired was processed by multivariate statistical analysis. The result revealed a significant difference between the control and intervention group. Twenty potential biomarkers, including fructose 6‐phosphate, sphingosine 1‐phosphate, docosahexaenoic acid and hexadecanoic acid, were located and identified by the accurate mass measurement of TOF MS. These compounds are believed to be functionally related to anti‐oxidative competence in vivo. In conclusion, metabonomics study is a valuable approach in exploring the effect mechanism of nutritional intervention on NTD prevention. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
110.
《Journal of Coordination Chemistry》2012,65(11):2021-2027
Results of quantum-chemical calculations of MCl4–C6H5COCl (M=Si, Ge, Sn) systems of 1?:?1 composition using RHF/3-21?G* and MP2/3-21?G* levels as well as those of 1?:?2 composition using the RHF/3-21?G* level have been represented. MCl4?←?C6H5COCl complexes of 1?:?1 composition are energetically more advantageous. They are formed in solid state provided that the M···O distance in individual systems is considerably less than the sum of van der Waals radii of M and O and their total energies are appreciably less than the sum of total energies of components. These conditions are realized only for M=Sn. In systems of 1?:?2 compositions, calculated M···O distances are practically equal to the sum of covalent radii of M and O. Nonetheless, complexes with such composition are not formed in solid state. Total energy of the system which is lower than the sum of its components’ energies is not an indispensable condition for complex formation. The 35Cl nuclear quadrupole resonance (NQR) frequencies and asymmetry parameters of the electric field gradient at the 35Cl nuclei have been evaluated using the results of ab initio calculations. 相似文献