全文获取类型
收费全文 | 529513篇 |
免费 | 4791篇 |
国内免费 | 1297篇 |
专业分类
化学 | 269957篇 |
晶体学 | 7649篇 |
力学 | 26043篇 |
综合类 | 17篇 |
数学 | 68108篇 |
物理学 | 163827篇 |
出版年
2021年 | 5079篇 |
2020年 | 5504篇 |
2019年 | 6258篇 |
2018年 | 8439篇 |
2017年 | 8590篇 |
2016年 | 11669篇 |
2015年 | 6218篇 |
2014年 | 10497篇 |
2013年 | 23563篇 |
2012年 | 18466篇 |
2011年 | 21923篇 |
2010年 | 16508篇 |
2009年 | 16355篇 |
2008年 | 20752篇 |
2007年 | 20609篇 |
2006年 | 18689篇 |
2005年 | 16679篇 |
2004年 | 15532篇 |
2003年 | 14027篇 |
2002年 | 13907篇 |
2001年 | 14757篇 |
2000年 | 11353篇 |
1999年 | 8762篇 |
1998年 | 7614篇 |
1997年 | 7483篇 |
1996年 | 6933篇 |
1995年 | 6263篇 |
1994年 | 6271篇 |
1993年 | 6022篇 |
1992年 | 6379篇 |
1991年 | 6868篇 |
1990年 | 6580篇 |
1989年 | 6489篇 |
1988年 | 6324篇 |
1987年 | 6133篇 |
1986年 | 5873篇 |
1985年 | 7410篇 |
1984年 | 7770篇 |
1983年 | 6535篇 |
1982年 | 6819篇 |
1981年 | 6329篇 |
1980年 | 6004篇 |
1979年 | 6508篇 |
1978年 | 6743篇 |
1977年 | 6630篇 |
1976年 | 6587篇 |
1975年 | 6305篇 |
1974年 | 6129篇 |
1973年 | 6425篇 |
1972年 | 4707篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
A. P. Solov’ev M. I. Perchenko Yu. P. Sinichkin O. V. Zyuryukina 《Technical Physics》2002,47(8):996-1001
An expression for a signal at the ultrasonic frequency from a photodetector arising when diffraction waves at the cathode
mix is obtained for the case when the optical and acoustic beams are space-limited and Bragg angles are small. The alternating
current generated when the scattering medium is crossed by a focused 3-MHz ultrasonic beam and illuminated by a cw He-Ne laser
is measured. Satisfactory agreement between experimental results and those calculated from the formulas obtained indicates
that our model treating acoustooptical interaction in the medium in terms of Raman-Nath diffraction is valid. Conditions for
measuring the alternating current (which is a parameter of acoustooptical imaging) that are optimal from the viewpoint of
maximizing the signal and signal-to-noise ratio are predicted theoretically and corroborated experimentally. 相似文献
992.
R. A. Kotel’nikova G. N. Bogdanov G. V. Zotina V. S. Romanova Z. N. Parnes 《Physics of the Solid State》2002,44(3):576-577
Efficient quenching of eosin phosphorescence by amino-acid derivatives of fullerene (AADFs) such as C60-alanine and C60-glycine in aqueous solutions indicates the possibility of transferring electrons from eosin to fullerene upon collisions or in the exciplex state. To investigate electron transfer in the protein structure, we studied the process of incorporation of C60-alanine and C60-glycine into the heme pocket of myoglobin by controlling Förster quenching. The dissociation constant for the protein-AADF complex was estimated. 相似文献
993.
V. I. Strunin A. A. Lyakhov G. Zh. Khudaibergenov V. V. Shkurkin 《Technical Physics》2002,47(6):760-766
A model of silane decomposition in a radio-frequency argon plasma is constructed. The concentrations of SiH4 decomposition products, as well as products of synthesis (higher silanes), are calculated. The role of metastable argon atoms in the formation of SiH3 radicals and the higher silanes is analyzed. 相似文献
994.
A relaxation kinetic equation that describes the behavior of a Bose gas is derived. The Kramers half-space problem on isothermal slip is treated. An analytical solution and the number-of-particle distribution function for particles flying toward a wall, in explicit form, are obtained. The dependence of the slip velocity on the parameter that is the ratio of the chemical potential to the product of Boltzmann's constant by the absolute temperature is analyzed. The influence of the quantum effects on the isothermal slip coefficient is evaluated for He4. 相似文献
995.
996.
997.
998.
The long-range sound propagation from a deep ocean to a receiving system located on the shelf is modeled. The waveguide model is constructed on the basis of the data of an acoustic-oceanographic experiment carried out in the northwestern Pacific. The sensitivity and the frequency dependence of the difference in the sound field levels at the crossing of the frontal zone on the geoacoustic characteristics of the bottom of the shelf and the continental slope are investigated. It is shown that the level difference decreases by 8.2 dB as the velocity of longitudinal waves increases by 100 m/s in the range within 1490–1820 m/s. 相似文献
999.
Results of acoustic measurements in skeletal muscle are generalized. It is shown that assessment of the pathologies and functional condition of the muscular system is possible with the use of shear waves. The velocity of these waves in muscles is much smaller than the velocity of sound; therefore, a higher symmetry type is formed for them. In the presence of a preferential direction (along muscle fibers), it is characterized by only two rather than five (as in usual media with the same anisotropy) moduli of elasticity. A covariant form of the corresponding wave equation is presented. It is shown that dissipation properties of skeletal muscles can be controlled by contracting them isometrically. Pulsed loads (shocks) and vibrations are damped differently, depending on their frequency spectrum. Characteristic frequencies on the order of tens and hundreds of hertz are attenuated due to actin-myosin bridges association/dissociation dynamics in the contracted muscle. At higher (kilohertz) frequencies, when the muscle is tensed, viscosity of the tissue increases by a factor of several tens because of the increase in friction experienced by fibrillar structures as they move relative to the surrounding liquid; the tension of the fibers changes the hydrodynamic conditions of the flow around them. Finally, at higher frequencies, the attenuation is associated with the rheological properties of biological molecules, in particular, with their conformational dynamics in the wave field. Models that describe the controlled shock dissipation mechanisms are proposed. Corresponding solutions are found, including those that allow for nonlinear effects. 相似文献
1000.
Regina S. Burachik Rafail N. Gasimov Nergiz A. Ismayilova C. Yalçin. Kaya 《Journal of Global Optimization》2006,34(1):55-78
We study convergence properties of a modified subgradient algorithm, applied to the dual problem defined by the sharp augmented
Lagrangian. The primal problem we consider is nonconvex and nondifferentiable, with equality constraints. We obtain primal
and dual convergence results, as well as a condition for existence of a dual solution. Using a practical selection of the
step-size parameters, we demonstrate the algorithm and its advantages on test problems, including an integer programming and
an optimal control problem.
*Partially Supported by 2003 UniSA ITEE Small Research Grant Ero2.
Supported by CAPES, Brazil, Grant No. 0664-02/2, during her visit to the School of Mathematics and Statistics, UniSA. 相似文献