全文获取类型
收费全文 | 409124篇 |
免费 | 3424篇 |
国内免费 | 954篇 |
专业分类
化学 | 206727篇 |
晶体学 | 6537篇 |
力学 | 19386篇 |
综合类 | 7篇 |
数学 | 54217篇 |
物理学 | 126628篇 |
出版年
2018年 | 11114篇 |
2017年 | 11921篇 |
2016年 | 8347篇 |
2015年 | 3841篇 |
2014年 | 4633篇 |
2013年 | 13202篇 |
2012年 | 13389篇 |
2011年 | 23251篇 |
2010年 | 14755篇 |
2009年 | 14720篇 |
2008年 | 20607篇 |
2007年 | 23831篇 |
2006年 | 10509篇 |
2005年 | 15965篇 |
2004年 | 11931篇 |
2003年 | 11001篇 |
2002年 | 8890篇 |
2001年 | 10188篇 |
2000年 | 7780篇 |
1999年 | 5918篇 |
1998年 | 4489篇 |
1997年 | 4587篇 |
1996年 | 4576篇 |
1995年 | 4179篇 |
1994年 | 4073篇 |
1993年 | 3784篇 |
1992年 | 4586篇 |
1991年 | 4579篇 |
1990年 | 4411篇 |
1989年 | 4395篇 |
1988年 | 4309篇 |
1987年 | 4323篇 |
1986年 | 4032篇 |
1985年 | 5269篇 |
1984年 | 5334篇 |
1983年 | 4404篇 |
1982年 | 4572篇 |
1981年 | 4398篇 |
1980年 | 4312篇 |
1979年 | 4670篇 |
1978年 | 5048篇 |
1977年 | 4726篇 |
1976年 | 4656篇 |
1975年 | 4418篇 |
1974年 | 4334篇 |
1973年 | 4421篇 |
1972年 | 2916篇 |
1968年 | 2804篇 |
1967年 | 2826篇 |
1966年 | 2505篇 |
排序方式: 共有10000条查询结果,搜索用时 241 毫秒
991.
The norm kernel of the A=12 system composed of two 6He clusters, and the L=0 basis functions (in the SU(3) and angular momentum-coupled schemes) are analytically obtained in the Fock-Bargmann space. The norm kernel has a diagonal form in the former basis, but the asymptotic conditions are naturally defined in the latter one. The system is a good illustration for the method of projection of the norm kernel to the basis functions in the presence of SU(3) degeneracy that was proposed by the authors. The coupled-channel problem is considered in the algebraic version of the resonating-group method, with the multiple decay thresholds being properly accounted for. The structure of the ground state of 12Be obtained in the approximation of zero-range nuclear force is compared with the shell-model predictions. In the continuum part of the spectrum, the S-matrix is constructed, the asymptotic normalization coefficients are deduced and their energy dependence is analyzed. 相似文献
992.
The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been
computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory
of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the
previous computed results [2]. Present results are compared with measured values [3] and with previous computation results
[2]. Some other theoretical computational results are also presented here for comparison.
相似文献
993.
T. Wagner J. Gutwirth P. Nemec M. Frumar T. Wagner M. Vlcek V. Perina A. Mackova V. Hnatovitz 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1561-1562
The pulsed laser deposition technique has been applied to prepare amorphous ternary AgSbS films. The films were prepared from AgSbS2 bulk glass using a KrF excimer laser. The composition of prepared films according to the results of the energy dispersive X-ray analysis and the Rutherford backscattering was close to bulk one. Optical transmission and spectral dependence of the refractive index proved the good optical quality of the films. The Ar+ ion laser dot exposures of the films show a potential applicability of the films as a new type of optical recording material. PACS 78.66.Jg; 81.15.Fg; 81.40.Wx 相似文献
994.
N. V. Vysotina N. N. Rozanov V. E. Semenov V. A. Smirnov S. V. Fedorov D. N. Christodoulides 《Optics and Spectroscopy》2005,98(6):895-903
The polarization structure of nonparaxial spatial solitons in a transparent medium with the electronic mechanism of Kerr nonlinearity is studied theoretically. It is demonstrated analytically in the weak nonparaxiality approximation that the regime of polarization locking, in which all the field components have the same propagation constant, is the only stable regime. Estimates of the rate of transition of the initial metastable regime of rotation of the polarization ellipse to the regime of polarization locking are presented. Based on a numerical solution of the nonlinear Maxwell equations, the presence of the nonparaxial regime of polarization locking is confirmed and the main characteristics of the corresponding spatial solitons are obtained. 相似文献
995.
V. I. Vershinin 《Journal of Analytical Chemistry》2005,60(9):880-891
Russian standards in training conventional graduates and bachelors are considered. These standards determine the status and volume of analytical chemistry courses at different higher educational institutions. An analysis of the educational standards, standard curricula, and the aims of teaching analytical chemistry suggests the advisability of changing the content of the course, particularly at industrial (branch) higher educational institutions. The provision of the analytical chemistry course with special literature (manuals, textbooks), equipment, and computer software is considered. 相似文献
996.
Q.-Y. Shao A.-D. Li J.-B. Cheng H.-Q. Ling D. Wu Z.-G. Liu N.-B. Ming C. Wang H.-W. Zhou B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2005,81(6):1181-1185
LaAlO3 (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO2 layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p 相似文献
997.
B. M. Azizur Rahman A. K. M. Saiful Kabir Muttukrishnan Rajarajan Kenneth T. V. Grattan 《Optical and Quantum Electronics》2005,37(1-3):171-183
Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations. 相似文献
998.
The results of the elemental analysis of blood serum are often used for the diagnosis of different diseases associated with derangements of mineral metabolism. In this work, we studied the main sources of a systematic error in the atomic-emission spectrometric (AES) analysis of blood serum and developed a procedure for the AES determination of Ca, Cu, Fe, Mg, P, and Zn in the human blood serum. The repeatability relative standard deviations of determinations varied from 10 to 24%. 相似文献
999.
Electron transport in a three-dimensional quantum wire is analyzed by taking into account electron scattering by a single point impurity. It is shown that the magnetoconductance plotted versus chemical potential μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively. The peaks lie near the conductance steps. The thermopower plotted versus μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively. 相似文献
1000.
The effect of hydrostatic pressure on the structure of a plastic columnar discotic triphenylene has been investigated. The goal was to determine whether pressure can be used to modify electronic properties via changes in structural properties of columnar discotics to any significant extent. The findings are that (i) the intra- and inter-columnar distances are reduced in a nearly isotropic fashion, (ii) that the crystal sizes are reduced and (iii) that a transition takes place from a more highly ordered plastic columnar to a less ordered hexagonal columnar state with increasing pressure. The induced decrease of the molecular distances, amounting to 6% for pressures up to 17 kbar, are clearly too small to induce an appreciable modification of the electronic structure and thus opto-electronic properties. 相似文献