全文获取类型
收费全文 | 171389篇 |
免费 | 1801篇 |
国内免费 | 507篇 |
专业分类
化学 | 88477篇 |
晶体学 | 3044篇 |
力学 | 7157篇 |
综合类 | 3篇 |
数学 | 19538篇 |
物理学 | 55478篇 |
出版年
2020年 | 1403篇 |
2019年 | 1563篇 |
2018年 | 1981篇 |
2017年 | 2067篇 |
2016年 | 3190篇 |
2015年 | 1896篇 |
2014年 | 3119篇 |
2013年 | 7673篇 |
2012年 | 5763篇 |
2011年 | 6895篇 |
2010年 | 5030篇 |
2009年 | 5014篇 |
2008年 | 6544篇 |
2007年 | 6442篇 |
2006年 | 6089篇 |
2005年 | 5514篇 |
2004年 | 5102篇 |
2003年 | 4605篇 |
2002年 | 4465篇 |
2001年 | 5225篇 |
2000年 | 3869篇 |
1999年 | 2974篇 |
1998年 | 2488篇 |
1997年 | 2396篇 |
1996年 | 2244篇 |
1995年 | 2123篇 |
1994年 | 2092篇 |
1993年 | 2003篇 |
1992年 | 2305篇 |
1991年 | 2247篇 |
1990年 | 2198篇 |
1989年 | 2125篇 |
1988年 | 2121篇 |
1987年 | 2124篇 |
1986年 | 2021篇 |
1985年 | 2629篇 |
1984年 | 2684篇 |
1983年 | 2382篇 |
1982年 | 2494篇 |
1981年 | 2310篇 |
1980年 | 2291篇 |
1979年 | 2430篇 |
1978年 | 2464篇 |
1977年 | 2392篇 |
1976年 | 2439篇 |
1975年 | 2365篇 |
1974年 | 2328篇 |
1973年 | 2509篇 |
1972年 | 1623篇 |
1971年 | 1338篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
N. L. Dmitruk O. Yu. Borkovskaya R. V. Konakova I. B. Mamontova S. V. Mamykin D. I. Voitsikhovskiy 《Technical Physics》2002,47(6):698-702
The effect of 60Co gamma irradiation at doses of 103-2×105 Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied
to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating)
obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer
higher efficiency and radiation resistance. 相似文献
92.
Electrical resistivity of U3Tein4, U2Te3 (cubic) and UTe3 has been measured over temperature range 4.2–300 K. The two former compounds appear to be semimetallic conductors while the last one has semiconducting character. The results are discussed in the terms of available magnetic data. 相似文献
93.
94.
Philip B. Lukins 《Chemical physics letters》1991,180(6):551-555
Measurements of the magneto-optical Cotton—Mouton effect at 632.8 nm of O2(3Σ) over a range of temperature (≈299–464 K) and pressure (up to 613 kPa) are reported and analysed. The study enables a useful comparison to be made of data obtained under different conditions by the two groups that have undertaken systematic measurements of this effect. Agreement between the experimental results and also the derived molecular properties is found to be satisfactory. 相似文献
95.
96.
Possibilities for the control of the parameters of free-polarization decay (FPD), optical nutation, and photon echo (PE) using the dressing field are studied. Coherent transients are generated with the Stark switching technique and are detected in the radiation of the probe field polarized orthogonally to the dressing field. The evolution-operator technique is employed in the calculations. The experiments are performed at the R(4, 3) transition of the 0 ? 1 v3 13CH3F vibrational band with the radiation of a cw CO2 laser. It is theoretically and experimentally demonstrated that FPD and PE are suppressed upon an increase in the intensity of the dressing field. The observed shapes of the transient FPD and PE signals and their variations with the dressing field intensity are in qualitative agreement with the results of the calculations. 相似文献
97.
S. Meenakshi B.K. Godwal I. Orgzall S. Tkachev 《Journal of Physics and Chemistry of Solids》2006,67(8):1660-1667
We report the results of an X-ray diffraction study of CdAl2Se4 and of Raman studies of HgAl2Se4 and ZnAl2Se4 at room temperature, and of CdAl2S4 and CdAl2Se4 at 80 K at high pressure. The ambient pressure phase of CdAl2Se4 is stable up to a pressure of 9.1 GPa above which a phase transition to a disordered rock salt phase is observed. A fit of the volume pressure data to a Birch-Murnaghan type equation of state yields a bulk modulus of 52.1 GPa. The relative volume change at the phase transition at ∼9 GPa is about 10%. The analysis of the Raman data of HgAl2Se4 and ZnAl2Se4 reveals a general trend observed for different defect chalcopyrite materials. The line widths of the Raman peaks change at intermediate pressures between 4 and 6 GPa as an indication of the pressure induced two stage order-disorder transition observed in these materials. In addition, we include results of a low temperature Raman study of CdAl2S4 and CdAl2Se4, which shows a very weak temperature dependence of the Raman-active phonon modes. 相似文献
98.
V. Edon M.C. Hugon B. Agius L. Miotti C. Radtke F. Tatsch J.J. Ganem I. Trimaille I.J.R. Baumvol 《Applied Physics A: Materials Science & Processing》2006,83(2):289-293
The influence of processing parameters on the electrical characteristics of RuO2/LaAlO3/Si metal-oxide-semiconductor structures was investigated. In particular, the sputtering regime during deposition of LaAlO3 on Si and the atmosphere used in the post-deposition annealing step were addressed by determining capacitance-voltage and
gate current-voltage characteristics. These results were correlated with compositional information obtained by Rutherford
backscattering spectrometry and nuclear reaction analysis. A post-deposition annealing step in oxygen at 600 °C resulted in
better electrical characteristics of the final structure as compared to the same treatment performed in nitrogen. This result
is explained by oxygen ability to heal oxygen vacancies in the LaAlO3 film, especially at the dielectric/semiconductor interface region. A thermalized sputtering regime during deposition of LaAlO3 on Si leads to capacitors with electrical characteristics superior to those deposited in ballistic regime.
PACS 77.84.Dy; 81.15.Cd; 81.40.Gh; 73.40.Qv; 82.80.Yc 相似文献
99.
We have employed a full-relativistic version of an all-electron full-potential linearized-augmented plane-wave method in the local density approximation to investigate the electronic structure of nanolaminate Zr2AlX (X=C and N). The Zr 4d electrons are treated as valence electrons. We have investigated the lattice parameters, bulk moduli, band structures, total and partial densities of states and charge densities. It is demonstrated that the strength and electrical transport properties in these materials are principally governed by the metallic planes. 相似文献
100.
A Dirac picture perturbation theory is developed for the time evolution operator in classical dynamics in the spirit of the Schwinger–Feynman–Dyson perturbation expansion and detailed rules are derived for computations. Complexification formalisms are given for the time evolution operator suitable for phase space analyses, and then extended to a two-dimensional setting for a study of the geometrical Berry phase as an example. Finally a direct integration of Hamilton's equations is shown to lead naturally to a path integral expression, as a resolution of the identity, as applied to arbitrary functions of generalized coordinates and momenta. 相似文献