全文获取类型
收费全文 | 108528篇 |
免费 | 5903篇 |
国内免费 | 6514篇 |
专业分类
化学 | 61633篇 |
晶体学 | 1353篇 |
力学 | 6195篇 |
综合类 | 392篇 |
数学 | 13398篇 |
物理学 | 37974篇 |
出版年
2023年 | 782篇 |
2022年 | 1765篇 |
2021年 | 2176篇 |
2020年 | 2368篇 |
2019年 | 2542篇 |
2018年 | 2943篇 |
2017年 | 2870篇 |
2016年 | 3582篇 |
2015年 | 2514篇 |
2014年 | 3575篇 |
2013年 | 5097篇 |
2012年 | 5261篇 |
2011年 | 6757篇 |
2010年 | 5002篇 |
2009年 | 4965篇 |
2008年 | 4646篇 |
2007年 | 4359篇 |
2006年 | 4065篇 |
2005年 | 3840篇 |
2004年 | 4325篇 |
2003年 | 3533篇 |
2002年 | 3490篇 |
2001年 | 3081篇 |
2000年 | 2213篇 |
1999年 | 1862篇 |
1998年 | 1818篇 |
1997年 | 1539篇 |
1996年 | 1442篇 |
1995年 | 1228篇 |
1994年 | 1275篇 |
1993年 | 1522篇 |
1992年 | 1532篇 |
1991年 | 1407篇 |
1990年 | 1415篇 |
1989年 | 1330篇 |
1988年 | 995篇 |
1987年 | 941篇 |
1986年 | 923篇 |
1985年 | 947篇 |
1984年 | 938篇 |
1983年 | 839篇 |
1982年 | 822篇 |
1979年 | 803篇 |
1978年 | 817篇 |
1977年 | 815篇 |
1976年 | 924篇 |
1975年 | 817篇 |
1974年 | 848篇 |
1973年 | 850篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×1010 cm?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures. 相似文献
82.
T. Yu. Gumerov A. F. Dobrynina R. A. Yusupov V. P. Barabanov 《Russian Journal of Applied Chemistry》2006,79(12):1935-1939
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants. 相似文献
83.
The electrodynamic properties of coaxial two-dimensional Bragg resonators with two-dimensional distributed feedback are analyzed. These resonators are made of coaxial waveguide sections with doubly periodic corrugation, which provides coupling and mutual scattering of four partial waves. Two of them propagate along the waveguide, while the other two propagate in the transverse (azimuthal) direction. It is shown that the high azimuthal index selectivity of two-dimensional Bragg resonators may be related to a qualitative difference in topology of the dispersion characteristics of azimuth-symmetric and asymmetric normal waves propagating in infinite waveguides of such a geometry. For the finite-length systems used as two-dimensional Bragg resonators, the eigenmode spectrum is found for two types of boundary conditions that correspond to the limiting cases of perfectly matched (open) systems and, conversely, of systems closed for the extraction of transverse electromagnetic fluxes. Perimeter-to-length ratios of the resonator at which the Q factor of the fundamental azimuth-symmetric mode is greater than those of the other modes are determined. The applicability domain of the geometrical approach, which was earlier applied to two-dimensional Bragg resonators, is discussed. 相似文献
84.
Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed. 相似文献
85.
Zhong‐Zhen Yu Mingshu Yang Qingxin Zhang Chungui Zhao Yiu‐Wing Mai 《Journal of Polymer Science.Polymer Physics》2003,41(11):1234-1243
Nylon‐66 nanocomposites were prepared by melt‐compounding nylon‐66 with an alkyl ammonium surfactant pretreated montmorillonite (MMT). The thermal stability of the organic MMT powders was measured by thermogravimetric analysis. The decomposition of the surfactant on the MMT occurred from 200 to 500 °C. The low onset decomposition temperature of the organic MMT is one shortcoming when it is used to prepare polymer nanocomposites at high melt‐compounding temperatures. To provide greater property enhancement and better thermal stability of the polymer/MMT nanocomposites, it is necessary to develop MMT modified with more thermally stable surfactants. The dispersion and spatial distribution of the organic MMT layers in the nylon‐66 matrix were characterized by X‐ray diffraction. The organic MMT layers were exfoliated but not randomly dispersed in the nylon‐66 matrix. A model was proposed to describe the spatial distribution of the organic MMT layers in an injection‐molded rectangular bar of nylon‐66/organic MMT nanocomposites. Most organic MMT layers were oriented in the injection‐molding direction. Layers near the four surfaces of the bar were parallel to their corresponding surfaces; whereas those in the bulk differed from the near‐surface layers and rotated themselves about the injection‐molding direction. The influence of the spatial distribution of the organic MMT on crystallization of nylon‐66 was also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1234–1243, 2003 相似文献
86.
Yu. V. Sanochkin 《Technical Physics》2003,48(5):546-551
It is shown that, along with gravity waves, surface and internal waves caused by van der Waals forces may exist in a liquid
with a horizontal free surface. A dispersion relation is found by using the stepwise approximation for the coefficients of
a wave equation derived for these waves. The surface waves are similar to surface gravity waves in dispersion and amplitude
distribution but differ in frequency by several orders of magnitude. Another sequence of roots in the spectrum corresponds
to internal van der Waals waves that have an upper frequency bound and the dispersion law typical of a multimode waveguide. 相似文献
87.
S. S. Andreev A. D. Akhsakhalyan M. A. Bibishkin N. I. Chkhalo S. V. Gaponov S. A. Gusev E. B. Kluenkov K. A. Prokhorov N. N. Salashchenko F. Schafers S. Yu. Zuev 《Central European Journal of Physics》2003,1(1):191-209
We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed
at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss
normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing
of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements
for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography
(ψ-13nm) and short period multilayer optics. 相似文献
88.
S. B. Bushuk Yu. A. Kal'vinkovskaya A. N. Rubinov 《Journal of Applied Spectroscopy》2004,71(2):291-294
Capture of an ensemble of polymeric microspheres in a water suspension under the action of optical gradient forces in the field of interfering laser beams has been investigated for the case of two-, three-, and four-beam interference. The self-diffraction and diffraction of radiation on induced ordered spatial distribution of particles have been obtained. 相似文献
89.
Piryatinskiĭ Yu. P. Yaroshchuk O. V. Dolgov L. A. Bidna T. V. Enke D. 《Optics and Spectroscopy》2004,97(4):537-542
Optics and Spectroscopy - The fluorescence of the nematic liquid crystal n-butyl-n′-methoxyazoxybenzene (BMAOB) in the form of a layer and in porous glasses with pores of different diameter... 相似文献
90.