全文获取类型
收费全文 | 3453篇 |
免费 | 39篇 |
国内免费 | 5篇 |
专业分类
化学 | 1227篇 |
晶体学 | 58篇 |
力学 | 183篇 |
数学 | 547篇 |
物理学 | 1482篇 |
出版年
2022年 | 28篇 |
2021年 | 52篇 |
2020年 | 67篇 |
2019年 | 68篇 |
2018年 | 95篇 |
2017年 | 105篇 |
2016年 | 140篇 |
2015年 | 53篇 |
2014年 | 92篇 |
2013年 | 159篇 |
2012年 | 137篇 |
2011年 | 127篇 |
2010年 | 124篇 |
2009年 | 132篇 |
2008年 | 135篇 |
2007年 | 127篇 |
2006年 | 124篇 |
2005年 | 88篇 |
2004年 | 77篇 |
2003年 | 76篇 |
2002年 | 93篇 |
2001年 | 85篇 |
2000年 | 57篇 |
1999年 | 61篇 |
1998年 | 54篇 |
1997年 | 51篇 |
1996年 | 46篇 |
1995年 | 32篇 |
1993年 | 30篇 |
1992年 | 26篇 |
1991年 | 41篇 |
1990年 | 35篇 |
1989年 | 38篇 |
1987年 | 37篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 35篇 |
1982年 | 41篇 |
1980年 | 38篇 |
1979年 | 36篇 |
1978年 | 37篇 |
1977年 | 48篇 |
1976年 | 50篇 |
1975年 | 45篇 |
1973年 | 46篇 |
1972年 | 31篇 |
1971年 | 35篇 |
1970年 | 31篇 |
1967年 | 28篇 |
排序方式: 共有3497条查询结果,搜索用时 0 毫秒
991.
Vladimir P. Kirin Vladimir A. Maksakov Sergey A. Popov 《Journal of organometallic chemistry》2004,689(15):2535-2542
The reaction of acetone-4-(2-methoxy-phenyl)thiosemicarbazone with triosmium cluster Os3(CO)11(NCMe) results in the formation of the cluster with the μ2 chelate-bridging ligand coordinated by S and N1 atoms, which was studied by X-ray diffraction analysis. Reaction of (3aR, 3bR, 4aR, 5aS)-5a-hydroxy-3,4,4-trimethyl-3a,3b,4,4a,5,5a-hexahydrocyclopropa[3, 4]cyclopenta[1,2-c]pyrazole-1-carbothioic acid amide with Os3(CO)11(NCMe) gives rise to the complex with the bridging ligand coordinated by sulphur atom. Further transformation of the complex in hot benzene results in tautomeric rearrangement of the organic ligand and the cleavage of the pyrazolinol cycle to form an open chain tautomer. Unusual silica gel induced oxidative cleavage of the cyclopropane ring in the open chain derivative and epoxidation of cycloalcane C-C bond are observed on the air. 相似文献
992.
O.V. Shcheritsa O.S. Mazhorova I.A. Denisov Yu.P. Popov A.V. Elyutin 《Journal of Crystal Growth》2006,290(2):350-356
The paper deals with computer simulation for growth and dissolution of ternary CdHgTe compounds in liquid-phase epitaxy (LPE) systems. The mathematical model accounts for the matter transport in both solid and liquid phases and the equilibrium phase diagram. The study displays the effect of solid-state diffusion on compositional grading at the substrate-layer boundary, on the formation of concentration distribution in both phases and on interface motion. The simulation has been done for isothermal conditions. 相似文献
993.
M. I. Fedorov V. V. Popov I. S. Eremin V. K. Zaitsev 《Physics of the Solid State》2000,42(7):1236-1239
The results of studying the kinetic coefficients of β-FeSi2 in the temperature range 4.2–300 K are considered. The resistivity decreases upon heating in the entire temperature range under investigation. The temperature dependences of the resistivity and thermal conductivity exhibit a break at ~20 K. In the range of 4.2–20 K, the resistivity is a linear function of temperature. The thermo-emf increases rapidly upon cooling and attains values exceeding 15 mV/K. The temperature dependence of the thermo-emf exhibits a break at ~40 K. The observed set of temperature dependences of the kinetic coefficients apparently cannot be explained by a superposition of the known effects only. A new effect probably exists that is associated with a strong electron-phonon interaction in FeSi2 and which requires a further investigation. 相似文献
994.
A. V. Andreev V. E. Asadchikov I. A. Artyukov A. V. Vinogradov V. N. Zruev Yu. S. Kas’yanov V. V. Kondratenko V. E. Levashov B. V. Mchedlishvili Yu. V. Ponomarev A. V. Popov A. A. Postnov S. V. Savel’ev R. A. Senin I. I. Struk 《Crystallography Reports》2001,46(4):596-600
The methods used to obtain X-ray images of track membranes and various biological objects in the soft (20 nm) and hard (0.2–0.02 nm) wavelength ranges have been considered. In the range of soft X-rays, the images were obtained in a Schwarzshild microscope. In the spectral range of hard X-ray radiation, various methods were used including the use of Fresnel zone plates, asymmetric reflecting crystals, X-ray microradiography and microtomography. 相似文献
995.
V. Yu. Popov 《Mathematical Notes》1999,65(2):188-201
The existence of a finitely based variety of anticommutative rings (in the sense of the identityx
2=0) with unsolvable equational theory is proved.
Translated fromMatematicheskie Zametki, Vol. 65, No. 2, pp. 230–245, February, 1999. 相似文献
996.
Synthesis of carbon nitride films by low-power inductively coupled plasma-activated transport reactions from a solid carbon source 总被引:1,自引:0,他引:1
C. Popov M.F. Plass A. Bergmaier W. Kulisch 《Applied Physics A: Materials Science & Processing》1999,69(2):241-244
Thin films of carbon nitride were prepared by low-power inductively coupled plasma chemical vapor deposition from a solid
carbon source by utilizing transport reactions. The maximum deposition rate achieved was 10 nm/min and depended mainly on
the substrate position in the reactor. The nitrogen fraction in the films was not so sensitive to the process parameters and
was at about 0.5 for all experiments as measured by Auger electron spectroscopy (AES) and elastic recoil detection (ERD) analysis.
The chemical bonding structure studied by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy
(XPS) showed the presence of triple, double and single bonds between carbon and nitrogen atoms.
Received: 12 May 1999 / Accepted: 12 May 1999 / Published online: 24 June 1999 相似文献
997.
An algorithm is proposed to construct a sequence of evolutionary adaptive grids, each consisting of segments of uniform grids
compatible with the Richardson extrapolation procedure. The necessary numerical accuracy is achieved by using Richardson's
extrapolation method to increase the accuracy of the difference solution and by controlling the nonhomogeneity parameter on
passing from one segment to the next. The numerical model used in the article is the diffusion-convection equation, whose
solution contains large gradients. Numerical calculations show that the algorithm attains the prespecified accuracy on a nonuniform
difference grid. Numerical examples support the universality of the proposed algorithm. High accuracy results can be obtained
without changing the structure of the difference schemes approximating the original problem; only the grid spacing has to
be changed.
Translated from Chislennye Metody v Matematicheskoi Fizike, Moscow State University, pp. 22–36, 1998. 相似文献
998.
A new method is proposed for setting a lower or upper limit a α
n
* on the neutron electric polarizability α
an
. It is based on the fact that the real part of the s-wave scattering amplitude changes sign near the s-wave neutron resonance at E=E*. The methods consist of the observation of the energy behavior of the forward-backward scattering asymmetry ω
1 which experiences a jump at E=E*. If the jump is such that dω
1/dE>0, then α
n
>α
n
*, while if dω
1/dE<0, then α
n
<α
n
*, and if dω
1/dE∼0, then α
n
∼α
n
*. Seven even-even nuclei are found with α
n
* from 0.5 to 3.1 in 10−3 fm3. Some details of a possible experiment with 182W are described.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 3, 171–174 (10 August 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
999.
E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1999,89(6):1045-1050
A solution of the three-dimensional time-dependent Schrödinger equation, describing the ionization dynamics of the hydrogen atom in a circular state in an electromagnetic field, is obtained by direct numerical integration. It is shown that the observed stabilization effect can be interpreted on the basis of the Kramers-Henneberger approach. A simple analytical model is proposed, which qualitatively describes the basic laws of the ionization process under the conditions of the reported calculations and laboratory experiments on ionization of the circular hydrogenlike 5g, m=4 state of the Ne atom. 相似文献
1000.
Physics of Atomic Nuclei - Recent results of the studies of exotic multiquark hadrons in the Fermilab D0 experiment are reported. These refer to the search and investigation of the... 相似文献