全文获取类型
收费全文 | 2511篇 |
免费 | 238篇 |
国内免费 | 271篇 |
专业分类
化学 | 450篇 |
晶体学 | 3篇 |
力学 | 123篇 |
综合类 | 65篇 |
数学 | 1744篇 |
物理学 | 635篇 |
出版年
2023年 | 23篇 |
2022年 | 51篇 |
2021年 | 59篇 |
2020年 | 80篇 |
2019年 | 66篇 |
2018年 | 66篇 |
2017年 | 61篇 |
2016年 | 89篇 |
2015年 | 70篇 |
2014年 | 119篇 |
2013年 | 168篇 |
2012年 | 116篇 |
2011年 | 153篇 |
2010年 | 113篇 |
2009年 | 166篇 |
2008年 | 161篇 |
2007年 | 175篇 |
2006年 | 153篇 |
2005年 | 140篇 |
2004年 | 103篇 |
2003年 | 103篇 |
2002年 | 100篇 |
2001年 | 73篇 |
2000年 | 84篇 |
1999年 | 77篇 |
1998年 | 61篇 |
1997年 | 48篇 |
1996年 | 50篇 |
1995年 | 30篇 |
1994年 | 32篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有3020条查询结果,搜索用时 31 毫秒
11.
Nobuhiro Honda 《Mathematische Nachrichten》2003,256(1):48-57
In a previous paper of the same title the author gave a generalization of the constrution of Donaldson–Friedman, to prove the existence of twistor spaces of n CP 2 with a special kind of divisors. In the present paper, we consider its equivariant version. When n = 3, this gives another proof of the existence of degenerate double solid with C *–action, and we show that the branch quartic surface is birational to an elliptic ruled surface. In case n ≥ 4, this yields new Moishezon twistor spaces with C *–action, which is shown to be the most degenerate ones among twistor spaces studied by Campana and Kreußler. 相似文献
12.
13.
14.
The crystallization of poly(ethylene terephthalate) under uniaxial tensile strain at different extension rates was investigated with optical polarimetry in a temperature range between the glass-transition temperature and the quiescent crystallization temperature. The evolution of the optical properties of the polymer, including the turbidity, birefringence, and dichroism, were monitored simultaneously with the mechanical parameters. To complete the semicrystalline microstructure characterization of the polymer under strain, an online wide-angle X-ray diffraction (WAXD) technique was used in separate experiments, which were performed under the same thermomechanical conditions. For real-time measurements, a high-energy synchrotron radiation source was used. The optical properties provided information about both the crystalline and amorphous phases, whereas the WAXD patterns essentially gave information about the crystalline phase. The two experimental techniques were then used in a complementary way to characterize the semicrystalline microstructure. Significant deviations from the stress-optical rule were found. This was attributed to both transient effects and the appearance of crystallites, which consisted of highly oriented molecular segments that could contribute to the optical anisotropy but not necessarily to the stress. The behavior of the optical dichroism was found to be qualitatively different from that of the birefringence. The latter monotonically increased with the strain, whereas the former first increased with the strain, passed through a maximum, and then decreased to a steady-state value. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1915–1927, 2004 相似文献
15.
The main purpose of this paper is to use a mean value theorem of Dirichlet L-functions to study the asymptotic property of a hybrid mean value of a generalized Cochrane sum, and give an interesting mean value formula.2000 Mathematics Subject Classification: Primary—11F20; Secondary—11F99 相似文献
16.
E. D. Nursultanov 《Mathematical Notes》1998,63(2):205-214
In this paper we prove theorems on multiplicators of Fourier series inL
p, where the conditions depend on a parameterp. An example illustrating the importance of these conditions is constructed.
Translated fromMatematicheskie Zametki, Vol. 63, No. 2, pp. 235–247, February, 1998. 相似文献
17.
For approximate wave functions, we prove the theorem that there is a one‐to‐one correspondence between the constraints of normalization and of the Fermi–Coulomb and Coulomb hole charge sum rules at each electron position. This correspondence is surprising in light of the fact that normalization depends on the probability of finding an electron at some position. In contrast, the Fermi–Coulomb hole sum rule depends on the probability of two electrons staying apart because of correlations due to the Pauli exclusion principle and Coulomb repulsion, while the Coulomb hole sum rule depends on Coulomb repulsion. We demonstrate the theorem for the ground state of the He atom by the use of two different approximate wave functions that are functionals rather than functions. The first of these wave function functionals is constructed to satisfy the constraint of normalization, and the second that of the Coulomb hole sum rule for each electron position. Each is then shown to satisfy the other corresponding sum rule. The significance of the theorem for the construction of approximate “exchange‐correlation” and “correlation” energy functionals of density functional theory is also discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
18.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献
19.
利用普通幂级数发生函数方法,通过对发生函数进行xD算子,得到和式∑k=0^nμ^kf(k)的计算公式,并计算该类和式+ 相似文献
20.
用三个关系式与Mathematica软件求第二类自然数幂和公式 总被引:1,自引:1,他引:0
首先介绍三个第二类自然数幂和关系式并对其中的两式给出证明,接着利用这些关系式与数学软件M athem atica4.0,给出求解第二类自然数幂和公式的若干机械计算方法. 相似文献