全文获取类型
收费全文 | 308037篇 |
免费 | 1818篇 |
国内免费 | 662篇 |
专业分类
化学 | 147690篇 |
晶体学 | 4506篇 |
力学 | 15295篇 |
综合类 | 6篇 |
数学 | 47042篇 |
物理学 | 95978篇 |
出版年
2020年 | 2026篇 |
2019年 | 2338篇 |
2018年 | 10992篇 |
2017年 | 11699篇 |
2016年 | 8088篇 |
2015年 | 3146篇 |
2014年 | 4007篇 |
2013年 | 9546篇 |
2012年 | 10984篇 |
2011年 | 19960篇 |
2010年 | 12611篇 |
2009年 | 12658篇 |
2008年 | 17932篇 |
2007年 | 21274篇 |
2006年 | 7967篇 |
2005年 | 13047篇 |
2004年 | 9345篇 |
2003年 | 8960篇 |
2002年 | 6953篇 |
2001年 | 6205篇 |
2000年 | 5090篇 |
1999年 | 3568篇 |
1998年 | 3129篇 |
1997年 | 3100篇 |
1996年 | 3048篇 |
1995年 | 2468篇 |
1994年 | 2548篇 |
1993年 | 2571篇 |
1992年 | 2713篇 |
1991年 | 2763篇 |
1990年 | 2690篇 |
1989年 | 2655篇 |
1988年 | 2590篇 |
1987年 | 2575篇 |
1986年 | 2475篇 |
1985年 | 3160篇 |
1984年 | 3348篇 |
1983年 | 2693篇 |
1982年 | 2965篇 |
1981年 | 2828篇 |
1980年 | 2636篇 |
1979年 | 2858篇 |
1978年 | 2996篇 |
1977年 | 2934篇 |
1976年 | 2936篇 |
1975年 | 2778篇 |
1974年 | 2759篇 |
1973年 | 2954篇 |
1972年 | 1948篇 |
1967年 | 1884篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Galia Pozina Elizaveta I. Girshova Konstantin M. Morozov Konstantin A. Ivanov Anton Yu. Egorov Mikhail A. Kaliteevski 《Annalen der Physik》2019,531(6)
Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures. 相似文献
122.
Differential inequalities for polynomials generalizing the well-known Smirnov, Rahman, Schmeisser, and Bernstein inequalities are obtained.
相似文献123.
Tereshchenko E. D. Cherniakov S. M. Yurik R. Yu. Rietveld M. T. Häggström I. 《Radiophysics and Quantum Electronics》2020,62(10):667-676
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar... 相似文献
124.
Journal of Structural Chemistry - An analysis is presented for the results obtained in the studies initiated by A. E. Shvelashivili, Corresponding Member, Academy of Sciences of Georgia, and... 相似文献
125.
126.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
127.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
128.
N. I. Golovina G. N. Nechiporenko G. G. Nemtsev G. P. Dolganova V. P. Roshchupkin D. B. Lempert G. B. Manelis 《Russian Journal of Applied Chemistry》2007,80(1):24-30
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined. 相似文献
129.
Yu. V. Pokonova 《Russian Journal of Applied Chemistry》2007,80(12):2163-2164
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic. 相似文献
130.
Using the simplest (sinusoidal) corrugation profile in the approximation of absence of losses in the material as an example, we study the regimes of complete transformation of an incident wave to the diffraction lobe by a corrugated metal surface or a corrugated interface of two dielectric media. A numerical-intuitive pattern of appearance and evolution of such regimes with increasing corrugation amplitude is revealed. It is shown that the regimes of complete transformation of an incident wave to the diffraction lobe are possible in both the case of autocollimation and the case of a considerable deviation from it. The examination is based on a numerical method of solving the integral equation by means of a specially created interactive processing system in Visual Fortran. 相似文献