全文获取类型
收费全文 | 35364篇 |
免费 | 3541篇 |
国内免费 | 4716篇 |
专业分类
化学 | 28658篇 |
晶体学 | 514篇 |
力学 | 2882篇 |
综合类 | 263篇 |
数学 | 3708篇 |
物理学 | 7596篇 |
出版年
2024年 | 55篇 |
2023年 | 393篇 |
2022年 | 1087篇 |
2021年 | 1016篇 |
2020年 | 1262篇 |
2019年 | 1176篇 |
2018年 | 1038篇 |
2017年 | 1342篇 |
2016年 | 1448篇 |
2015年 | 1269篇 |
2014年 | 1632篇 |
2013年 | 2564篇 |
2012年 | 1925篇 |
2011年 | 2242篇 |
2010年 | 1821篇 |
2009年 | 2252篇 |
2008年 | 2103篇 |
2007年 | 2147篇 |
2006年 | 1964篇 |
2005年 | 1831篇 |
2004年 | 1806篇 |
2003年 | 1416篇 |
2002年 | 1671篇 |
2001年 | 1074篇 |
2000年 | 880篇 |
1999年 | 720篇 |
1998年 | 623篇 |
1997年 | 561篇 |
1996年 | 588篇 |
1995年 | 540篇 |
1994年 | 519篇 |
1993年 | 362篇 |
1992年 | 354篇 |
1991年 | 223篇 |
1990年 | 173篇 |
1989年 | 162篇 |
1988年 | 173篇 |
1987年 | 139篇 |
1986年 | 104篇 |
1985年 | 85篇 |
1984年 | 88篇 |
1983年 | 31篇 |
1982年 | 79篇 |
1981年 | 104篇 |
1980年 | 114篇 |
1979年 | 123篇 |
1978年 | 95篇 |
1977年 | 72篇 |
1976年 | 64篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Based on the discrete-structural theory of thin plates and shells, a calculation model for thin-walled elements consisting
of a number of rigid anisotropic layers is put forward. It is assumed that the transverse shear and compression stresses are
equal on the interfaces. Elastic slippage is allowed over the interfaces between adjacent layers. The solution to the problem
is obtained in a geometrically nonlinear statement with account of the influence of transverse shear and compression strains.
The stress-strain state of circular two-layer transversely isotropic plates, both without defects and with a local area of
adhesion failure at their center, is investigated numerically and experimentally. It is found that the kinematic and static
contact conditions on the interfaces of layered thin-walled structural members greatly affect the magnitude of stresses and
strains. With the use of three variants of calculation models, in the cases of perfect and weakened contact conditions between
layers, the calculation results for circular plates are compared. It is revealed that the variant suggested in this paper
adequately reflects the behavior of layered thin-walled structural elements under large deformations.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 761–772, November–December, 2005. 相似文献
92.
Two groups of 10 speech-language pathology graduate students were each given 7 weeks of singing lessons to determine whether voice lessons could have an effect on their clinical and perceptual skills. Pre-, mid-, and posttests to measure various skills were designed and implemented. With use of paired sample statistical testing, statistically significant results were obtained. In addition, the subjective responses of the students show that the lessons were effective in improving pitch perception, breath control, and legato production or easy onset. This study supports efforts to integrate curricula in vocal performance and speech-language pathology. 相似文献
93.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献
94.
95.
96.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
97.
98.
Fusion-evaporation cross-sections for the α-induced reactions upon197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted
in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems
have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel
calculations that include the β2 and ν4 slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the
code CCDEF. 相似文献
99.
Ricardo García-Pelayo Iván Salazar William C. Schieve 《Journal of statistical physics》1993,72(1-2):167-187
An analytically solvable model for sand avalanches of noninteracting grains of sand, based on the Chapman-Kolmogorov equations, is presented. For a single avalanche, distributions of lifetimes, sizes of overflows and avalanches, and correlation functions are calculated. Some of these are exponentials, some are power laws. Spatially homogeneous distributions of avalanches are also studied. Computer simulations of avalanches of interacting grains of sand are compared to the solutions to the Chapman-Kolmogorov equations. We find that within the range of parameters explored in the simulation, the approximation of noninteracting grains of sand is a good one. 相似文献
100.
采用固源Si分子束外延,在较高的生长温度于Si(100)衬底上制备出Si1-xGex/Si量子阱发光材料。发光样品的质量和特性通过卢瑟福背散射、X射线双晶衍射及光致发光评估。背散射实验中观察到应变超晶格的反常沟道效应;X射线分析表明材料的生长是共度的、无应力释放的,结晶完整性好。低温光致发光主要是外延合金量子阱中带边激子的无声发射和横光学声子参与的激子复合。并讨论了生长温度对量于阱发光的影响。 相似文献