全文获取类型
收费全文 | 453433篇 |
免费 | 2046篇 |
国内免费 | 621篇 |
专业分类
化学 | 200436篇 |
晶体学 | 6506篇 |
力学 | 27745篇 |
综合类 | 20篇 |
数学 | 75236篇 |
物理学 | 146157篇 |
出版年
2020年 | 4274篇 |
2019年 | 5169篇 |
2018年 | 12480篇 |
2017年 | 12895篇 |
2016年 | 12283篇 |
2015年 | 5023篇 |
2014年 | 8793篇 |
2013年 | 16366篇 |
2012年 | 15915篇 |
2011年 | 22920篇 |
2010年 | 16958篇 |
2009年 | 17359篇 |
2008年 | 21249篇 |
2007年 | 23248篇 |
2006年 | 13319篇 |
2005年 | 14374篇 |
2004年 | 12468篇 |
2003年 | 12172篇 |
2002年 | 11362篇 |
2001年 | 10629篇 |
2000年 | 8527篇 |
1999年 | 6306篇 |
1998年 | 5825篇 |
1997年 | 5598篇 |
1996年 | 5212篇 |
1995年 | 4589篇 |
1994年 | 4615篇 |
1993年 | 4589篇 |
1992年 | 4665篇 |
1991年 | 5160篇 |
1990年 | 5079篇 |
1989年 | 5138篇 |
1988年 | 4796篇 |
1987年 | 4869篇 |
1986年 | 4546篇 |
1985年 | 5447篇 |
1984年 | 5664篇 |
1983年 | 4828篇 |
1982年 | 5067篇 |
1981年 | 4730篇 |
1980年 | 4380篇 |
1979年 | 5034篇 |
1978年 | 5223篇 |
1977年 | 5331篇 |
1976年 | 5521篇 |
1975年 | 5110篇 |
1974年 | 4940篇 |
1973年 | 5220篇 |
1972年 | 4343篇 |
1971年 | 3974篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Faitel'son E. A. Korkhov V. P. Aniskevich A. N. Starkova O. A. 《Mechanics of Composite Materials》2004,40(1):57-66
The results of a complex study of structural changes in a cured Norpol 440 polyester resin under the action of damp environment and mechanical loading are presented. A considerable effect of absorbed moisture on the structure and some characteristics of the material is revealed by using thermophysical methods and X-ray diffractometry. The joint effect of moisture and mechanical stress is estimated by investigating the creep in stationary and nonstationary moisture conditions. The anisotropy of the material structure formed during creep is evaluated from the results of dilatometric measurements. It is found that the degree of anisotropy of the material after creep accompanied by moisture sorption is higher than that after creep in the conditions of moisture equilibrium with atmosphere. It is established that the aftercure and relaxation of the residual creep deformation come to an end at heating to 80-85°C. At a further rise in temperature and repeated heating, changes in the material structure are not observed. 相似文献
992.
We propose iteration methods for solving the Dirichlet problem in domains with involved geometry. Such problems arise in relation to the problem of optimizing quantum dot and antidot infrared detectors. We estimate the deviation of an approximate solution from the exact solution. 相似文献
993.
We again consider the problem of the light-cone expansion for products of currents and explain the motivations making a rethinking of old results relevant today. 相似文献
994.
995.
Leonard M Khalilov Ludmila V Parfenova Askhat G Ibragimov Usein M Dzhemilev 《Journal of organometallic chemistry》2004,689(2):444-453
This paper is dedicated to a study of properties of the following novel optically active organoaluminium compounds (OACs): (1S,2S)-l,7,7-trimethyl-2-[(dialkylalumina)oxy]-bicyclo[2.2.1]heptanes and (1S)-N-(dialkylalumina)-6,7-dimethoxy-1-methyl-1,2,3,4- tetrahydroisoquinolines. The synthesis of the chiral OACs was carried out in the reaction of either natural camphor or salsolidine with both AlEt3 and i-Bu2AlH. The main goal of the research was to investigate the stereodifferentiating activity of the chiral OACs in the olefin carbo- and cycloalumination reactions, catalyzed by Cp2ZrCl2. 相似文献
996.
I. Antoniou M. Gadella J. Mateo G.P. Pronko 《International Journal of Theoretical Physics》2003,42(10):2389-2402
Through two examples: the Friedrichs model and a particular case of central potential scattering, we illustrate the way of constructing Gamow vectors. 相似文献
997.
Yu. V. Sanochkin 《Technical Physics》2003,48(5):546-551
It is shown that, along with gravity waves, surface and internal waves caused by van der Waals forces may exist in a liquid
with a horizontal free surface. A dispersion relation is found by using the stepwise approximation for the coefficients of
a wave equation derived for these waves. The surface waves are similar to surface gravity waves in dispersion and amplitude
distribution but differ in frequency by several orders of magnitude. Another sequence of roots in the spectrum corresponds
to internal van der Waals waves that have an upper frequency bound and the dispersion law typical of a multimode waveguide. 相似文献
998.
Salimgareeva V. N. Polevoi R. M. Kolesov S. V. Ostakhov S. S. Ponomareva V. A. Leplyanin G. V. 《Russian Journal of Applied Chemistry》2003,76(5):804-808
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied. 相似文献
999.
The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes. 相似文献
1000.
S. S. Andreev A. D. Akhsakhalyan M. A. Bibishkin N. I. Chkhalo S. V. Gaponov S. A. Gusev E. B. Kluenkov K. A. Prokhorov N. N. Salashchenko F. Schafers S. Yu. Zuev 《Central European Journal of Physics》2003,1(1):191-209
We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed
at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss
normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing
of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements
for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography
(ψ-13nm) and short period multilayer optics. 相似文献