全文获取类型
收费全文 | 7088篇 |
免费 | 1282篇 |
国内免费 | 499篇 |
专业分类
化学 | 2471篇 |
晶体学 | 87篇 |
力学 | 1608篇 |
综合类 | 62篇 |
数学 | 320篇 |
物理学 | 4321篇 |
出版年
2024年 | 6篇 |
2023年 | 48篇 |
2022年 | 127篇 |
2021年 | 162篇 |
2020年 | 181篇 |
2019年 | 180篇 |
2018年 | 151篇 |
2017年 | 221篇 |
2016年 | 274篇 |
2015年 | 323篇 |
2014年 | 331篇 |
2013年 | 1004篇 |
2012年 | 419篇 |
2011年 | 497篇 |
2010年 | 340篇 |
2009年 | 405篇 |
2008年 | 371篇 |
2007年 | 407篇 |
2006年 | 368篇 |
2005年 | 345篇 |
2004年 | 333篇 |
2003年 | 282篇 |
2002年 | 251篇 |
2001年 | 221篇 |
2000年 | 172篇 |
1999年 | 142篇 |
1998年 | 173篇 |
1997年 | 147篇 |
1996年 | 117篇 |
1995年 | 129篇 |
1994年 | 109篇 |
1993年 | 110篇 |
1992年 | 86篇 |
1991年 | 72篇 |
1990年 | 53篇 |
1989年 | 44篇 |
1988年 | 58篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 17篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 4篇 |
1972年 | 6篇 |
排序方式: 共有8869条查询结果,搜索用时 15 毫秒
21.
A. B. Mitkevich 《Mechanics of Composite Materials》2005,41(6):497-504
Errors in the programs of winding pressure vessels can lead to an asymmetric reinforcement structure, which affects the equilibrium
shape of their domes and the tension in the left and right families of filaments. In this paper, equations determining the
equilibrium shape of the domes, the tension in filaments, and the shear stresses between layers are obtained. Examples with
winding trajectories in the form of geodesics and constant-deviation lines are considered. It is found that, for pressure
vessels, in the absence of external torque, the tension levels in filaments of the left and right families differ considerably.
It is also revealed that, for actual friction coefficients in winding, the shear stresses taken up by the binder are insignificant.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 743–752, November–December, 2005. 相似文献
22.
23.
The problem of investigation of the amplitude and phase structure of a time-varying probing optical signal and the structure of time-varying inhomogeneities of a substance tested by this signal is considered. The analysis is concerned, in particular, with determination of the structure of signals and processes with resolution in the pico- and femtosecond range. The scheme used for the analysis is based on registration of four spatially separated spectra of the studied radiation. The spectra are formed in a four-channel scheme with a twin-wave Michelson interferometer and a spectral device. Modulators based on electrooptical crystals (perovskites) are placed in the channels. The sum spectra are formed: without modulators, with the effect of either of the modulators, and with both of them affecting the radiation. The effect of the studied substance implies either modulating the radiation (in this case it is described by multiplication) or redistributing the radiation (then it is described by convolution). 相似文献
24.
A solution to the phase problem in optics is considered within the context of the analysis of signals changing in time and of the effect of an object under investigation on the probing radiation. The solution is based on the use of a twin-wave interferometer with phase modulation in one of the channels and a spectrometer. The analysis is concerned, in particular, with signals and processes of ultrashort duration. To shift the frequency in the interferometer channel, an electrooptical crystal of ferroelectric perovskite is used as the modulator. Errors of amplitude and phase structures determined are analyzed. 相似文献
25.
V.B. Fainerman V.N. Kazakov S.V. Lylyk A.V. Makievski R. Miller 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):97-102
One of the essential differences in the design of bubble pressure tensiometers consists in the geometry of the measuring capillaries. To reach extremely short adsorption times of milliseconds and below, the so-called deadtime of the capillaries must be of the order of some 10 ms. In particular, for concentrated surfactant solutions, such as micellar solutions, short deadtimes are needed to minimize the initial surfactant load of the generated bubbles. A theoretical model is derived and confirmed by experiments performed for a wide range of experimental conditions, mainly in respect to variations in deadtime and bubble volume. 相似文献
26.
以金刚石压腔高压装置为工具,用Ⅱ型金刚石作压砧兼红外窗口,对本征态聚苯胺进行了高压(0~8.4 GPa)就位红外光谱测试。结果表明:在4.8~5.2 GPa压力区间,代表醌环振动的吸收峰相对代表苯环振动的吸收峰变小,表明聚苯胺在此压力区间结构上发生了显著变化,且这种变化是不可逆的。聚苯胺的高压(0~14.5 GPa)电阻测量结果表明:当压力小于7.5 GPa时,电阻随压力升高而显著降低,据此认为聚苯胺为电子性导电物质;在7.5 GPa处电阻出现极小值,然后又缓慢升高,至10 GPa后基本不变。推测聚苯胺电阻极小值是由结构变化引起的。至于红外光谱与电阻测量结果反映聚苯胺结构变化的压力值不一致,可能是由于测试条件不同所致。 相似文献
27.
28.
W. Kockelmann M. Hofmann O. Moze S.J. Kennedy K.H.J. Buschow 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):25-32
The element distributions and the magnetic ordering behaviour of compounds RNi10Si2 (R
=
Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize
in an ordered variant of the ThMn12 structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively,
corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn12 structure. TbNi10Si2 orders antiferromagnetically below T
N
= 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi10Si2 do not carry any ordered magnetic moments. The compounds with R
=
Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively.
Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002 相似文献
29.
30.
Y. Yavin 《Journal of Optimization Theory and Applications》1993,78(1):77-91
Stochastic optimal control techniques are applied to compare the performance of identical medium-range air-to-air missiles which have different thrust-mass profiles. The measure of the performance is the probability of reaching a lock-on-point with a favorable range of guidance and flight parameters, during a fixed time interval [0,t
f
], given that, during the flight, the trajectories of the missile are subjected to a variety of constraints including dynamic pressure constraints. 相似文献