全文获取类型
收费全文 | 529031篇 |
免费 | 4171篇 |
国内免费 | 1284篇 |
专业分类
化学 | 269308篇 |
晶体学 | 7646篇 |
力学 | 26013篇 |
综合类 | 17篇 |
数学 | 67860篇 |
物理学 | 163642篇 |
出版年
2021年 | 5052篇 |
2020年 | 5495篇 |
2019年 | 6234篇 |
2018年 | 8431篇 |
2017年 | 8565篇 |
2016年 | 11645篇 |
2015年 | 6185篇 |
2014年 | 10460篇 |
2013年 | 23524篇 |
2012年 | 18355篇 |
2011年 | 21813篇 |
2010年 | 16433篇 |
2009年 | 16293篇 |
2008年 | 20673篇 |
2007年 | 20530篇 |
2006年 | 18629篇 |
2005年 | 16628篇 |
2004年 | 15472篇 |
2003年 | 13965篇 |
2002年 | 13859篇 |
2001年 | 14731篇 |
2000年 | 11346篇 |
1999年 | 8753篇 |
1998年 | 7607篇 |
1997年 | 7472篇 |
1996年 | 6931篇 |
1995年 | 6262篇 |
1994年 | 6267篇 |
1993年 | 6019篇 |
1992年 | 6380篇 |
1991年 | 6874篇 |
1990年 | 6581篇 |
1989年 | 6489篇 |
1988年 | 6323篇 |
1987年 | 6139篇 |
1986年 | 5876篇 |
1985年 | 7409篇 |
1984年 | 7770篇 |
1983年 | 6535篇 |
1982年 | 6820篇 |
1981年 | 6331篇 |
1980年 | 6005篇 |
1979年 | 6505篇 |
1978年 | 6741篇 |
1977年 | 6629篇 |
1976年 | 6588篇 |
1975年 | 6302篇 |
1974年 | 6129篇 |
1973年 | 6424篇 |
1972年 | 4706篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
991.
992.
M A Aguilar-Mendez E San Martin-Martinez J E Morales A Cruz-Orea M R Jaime-Fonseca 《Analytical sciences》2007,23(4):457-461
Water vapor diffusion coefficient (WVDC) and thermal diffusivity (alpha) were determined in gelatin-starch films through photothermal techniques. The effect of different variables in the elaboration of these films, such as starch and glycerol concentrations and pH, were evaluated through the response surface methodology. The results indicated that an increase in the glycerol concentration and pH favored the WVDC of the films. On the other hand, alpha was influenced principally by the starch content and pH of the film-forming solution. The minimum alpha value was 4.5 x 10(-4) cm2/s, which is compared with alpha values reported for commercial synthetic polymers. 相似文献
993.
E. D. Aluker A. G. Krechetov A. Yu. Mitrofanov A. S. Pashpekin 《Russian Journal of Physical Chemistry B, Focus on Physics》2007,1(6):570-572
A new method for studying the kinetics of the expansion of explosion products based on measuring the time elapsed from explosion initiation to the short-circuiting of the discharge gap by the products was proposed. It was revealed that, at the initial stage of expansion of the silver azide explosion products, they move with uniform acceleration, a behavior suggestive that, during this period, the exothermic reaction 2N3 → 3N2 occurs. 相似文献
994.
Ben Craps Matthias R. Gaberdiel Jeffrey A. Harvey 《Communications in Mathematical Physics》2003,234(2):229-251
We study D-branes in the bosonic closed string theory whose automorphism group is the Bimonster group (the wreath product
of the Monster simple group with ℤ2). We give a complete classification of D-branes preserving the chiral subalgebra of Monster invariants and show that they
transform in a representation of the Bimonster. Our results apply more generally to self-dual conformal field theories which
admit the action of a compact Lie group on both the left- and right-moving sectors.
Received: 20 February 2002 / Accepted: 17 August 2002 Published online: 19 December 2002
Communicated by R.H. Dijkgraaf 相似文献
995.
A ring R has right SIP (SSP) if the intersection (sum) of two direct summands of R is also a direct summand. We show that the right SIP (SSP) is the Morita invariant property. We also prove that the trivial extension of R by M has SIP if and only if R has SIP and (1 – e)Me = 0 for every idempotent e in R. Moreover, we give necessary and sufficient conditions for the generalized upper triangular matrix rings to have SIP. 相似文献
996.
Translated from Matematicheskie Zametki, Vol. 50, No. 6, pp. 31–42, December, 1991. 相似文献
997.
For two types of qutrits specified by the dynamical symmetry SU(3) and SU(2), we consider the difference in entanglement caused by the lack of quantum observables in the latter case. In particular, we show that the SU(2) qutrits can have specific separable entanglement caused by quantum correlations of intrinsic degrees of freedom in a single party without interparty correlations. 相似文献
998.
D. A. Davydov S. Z. Nazarova A. A. Valeeva A. A. Rempel 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):677-680
The order-disorder phase transition in vanadium monoxide of substoichiometric compositions VOy has been studied for the first time in situ by the Faraday method with a pendulum magnetic balance of the Domenically type. A minimum is found on the temperature dependence of the magnetic susceptibility of vanadium monoxide of different compositions at a temperature of about 700 K. X-ray diffraction analysis performed before and after measuring the magnetic susceptibility confirmed the change in the structure of vanadium monoxide and the possibility of atom-vacancy processes upon cooling and heating of the samples. 相似文献
999.
M. A. Sakhbetdinov P. F. Kartsev 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1115-1117
Schemes and calculated characteristics of effective logic elements with two inputs for classical ground-state computations are reported. These elements have a high threshold (0.48) and perform a desired logical operation in a wide range of input signals. 相似文献
1000.
The following areal objects are considered: an ether thread contracting two material points and a multidimensional ether fibre in the pseudo-Euclidean world of events. An ether space-time model with an arbitrarily determined Riemannian metric is constructed and the problem of the λ term in Einstein equations is discussed in this regard. 相似文献