全文获取类型
收费全文 | 254330篇 |
免费 | 1993篇 |
国内免费 | 711篇 |
专业分类
化学 | 128844篇 |
晶体学 | 4251篇 |
力学 | 13232篇 |
综合类 | 18篇 |
数学 | 26245篇 |
物理学 | 84444篇 |
出版年
2021年 | 2387篇 |
2020年 | 2401篇 |
2019年 | 2923篇 |
2018年 | 4131篇 |
2017年 | 4086篇 |
2016年 | 5564篇 |
2015年 | 2889篇 |
2014年 | 5160篇 |
2013年 | 10781篇 |
2012年 | 8882篇 |
2011年 | 10679篇 |
2010年 | 8327篇 |
2009年 | 8582篇 |
2008年 | 10018篇 |
2007年 | 9813篇 |
2006年 | 8803篇 |
2005年 | 7737篇 |
2004年 | 7303篇 |
2003年 | 6680篇 |
2002年 | 6577篇 |
2001年 | 8194篇 |
2000年 | 6023篇 |
1999年 | 4496篇 |
1998年 | 3635篇 |
1997年 | 3699篇 |
1996年 | 3304篇 |
1995年 | 2894篇 |
1994年 | 2955篇 |
1993年 | 2787篇 |
1992年 | 3351篇 |
1991年 | 3468篇 |
1990年 | 3283篇 |
1989年 | 3284篇 |
1988年 | 3174篇 |
1987年 | 3235篇 |
1986年 | 2972篇 |
1985年 | 3793篇 |
1984年 | 3818篇 |
1983年 | 3091篇 |
1982年 | 3053篇 |
1981年 | 3009篇 |
1980年 | 2780篇 |
1979年 | 3256篇 |
1978年 | 3259篇 |
1977年 | 3464篇 |
1976年 | 3392篇 |
1975年 | 3093篇 |
1974年 | 3063篇 |
1973年 | 3124篇 |
1972年 | 2303篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
N. B. Voznesensky E. V. Gavrilov A. P. Zhevlakov V. K. Kirillovskiĭ P. V. Orlov 《Technical Physics》2007,52(2):271-275
Methods and schemes to inspect the EUV mirror shape are developed on the basis of a point diffraction interferometer with computer processing of interferograms. A measurement accuracy to within 0.001 of a wavelength in the visual range is achieved. 相似文献
92.
V. V. AntiĆ M. P. AntiĆ M. N. Govedarica P. R. DvorniĆ 《Journal of polymer science. Part A, Polymer chemistry》2007,45(11):2246-2258
The kinetics of the formation of poly(carbosiloxane), as well as of alkyl-substituted poly(siloxane), by Karstedt's catalyst catalyzed hydrosilylation were investigated. Linear poly(carbosiloxane), poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene], (PTMDSE), was obtained by hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS) and 1,1,3,3-tetramethyldisiloxane (TMDS), while alkyl-substituted poly(siloxane), poly(methyldecylsiloxane), (PMDS), was synthesized by hydrosilylation of poly(methylhydrosiloxane) (PMHS) and 1-decene. To investigate the kinetics of PTMDSE formation, two series of experiments were performed at reaction temperatures ranging from 25 to 56 °C and with catalyst concentrations ranging from 7.0 × 10−6 to 3.1 × 10−5 mol Pt/mol CHCH2. A series of experiments was performed at reaction temperatures ranging from 28 to 48 °C, with catalyst concentrations of 7.0 ×10−6 mol of Pt per mol of CHCH2, when kinetics of PMDS formation was investigated. All reactions were carried out in bulk, with equimolar amounts of the reacting Si H and CHCH2 groups. The course of the reactions was monitored by following the disappearance of the Si H bands using quantitative infrared spectroscopy. The results obtained showed typical first order kinetics for the PTMDSE formation, consistent with the proposed reaction mechanism. In the case of PMDS an induction period occurred at lower reaction temperatures, but disappeared at 44 °C and the rate of Si H conversion also started to follow the first-order kinetics. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2246–2258, 2007 相似文献
93.
N. M. Bogoliubov 《Journal of Mathematical Sciences》2007,143(1):2729-2737
We consider random walks of two essentially different classes of random walkers, namely, of vicious and friendly ones, on
one-dimensional lattices with periodic boundary conditions. The walkers are called vicious since, arriving at a lattice site,
they annihilate not only one another but all the remaining walkers as well. On the contrary, an arbitrary number of friendly
walkers can share the same lattice sites. It is shown that a natural model describing the behavior of friendly walkers is
an integrable model of the boson type. A representation of the generating function for the number of the lattice paths performed
by a fixed number of friendly walkers for a certain number of steps is obtained. Bibliography: 22 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 335, 2006, pp. 59–74. 相似文献
94.
95.
Raman scattering in glasses is investigated theoretically. The experimental Raman spectra of glasses exhibit a low-frequency peak (at ~10 cm?1) that, as a rule, is attributed to vibrational modes of nanometer-sized structural units (nanocrystallites). It is established that the elastic moduli of nanocrystallites must necessarily be dependent on their sizes due to the Laplace pressure effect. A theory of the low-frequency peak is constructed using a realistic size distribution function of nanocrystallites with allowance made for the Laplace pressure effect and the dissipation of vibrational energy. Within this theory, the shape of the low-frequency peak and its evolution with temperature can be analyzed quantitatively. The proposed approach offers a physical interpretation of the experimental data and provides insight into the relation of the characteristic nanocrystallite sizes to the elastic moduli and surface tension coefficients of materials. 相似文献
96.
97.
An experimental apparatus and related procedures for the determination of the effective thermal conductivity of sintered powder-metal
plates saturated with distilled water at temperatures in the range 20–150°C are discussed. The apparatus and procedures are
applied to two samples of sintered powder-metal plates, one made of nickel 200 and the other of stainless steel 316, with
porosities of 28.10 and 46.45%, respectively, and each of nominal dimensions 127 mm × 127 mm × 6.35 mm. The experimental
results are compared with corresponding predictions yielded by several correlations available in the literature. The correlations
based on experimental data for packed beds of spherical particles and also porous plates made of cold-pressed (but not sintered)
particles of angular shapes do not apply well to sintered powder-metal plates. A new correlation, which is based on extensions
of ideas contained in earlier works and provides improved predictions, is proposed. 相似文献
98.
A fast electrooptic modulation in a polymer waveguide using a ferroelectric liquid crystal has been proposed. In this device, the surface stabilized ferroelectric liquid crystal and the soft mode ferroelectric liquid crystal are used as an active material on the passive polymer waveguide, and electrooptic switching is realized by controlling the total reflection at the polymer waveguide-liquid crystal interface. The response time is of the order of several microseconds. The analogue electrooptic modulation in the waveguide is realized using the field induced linear molecular tilt of the electroclinic effect in the soft mode ferroelectric liquid crystal. 相似文献
99.
100.