全文获取类型
收费全文 | 7920篇 |
免费 | 220篇 |
国内免费 | 55篇 |
专业分类
化学 | 4754篇 |
晶体学 | 58篇 |
力学 | 171篇 |
数学 | 1419篇 |
物理学 | 1793篇 |
出版年
2023年 | 25篇 |
2022年 | 76篇 |
2021年 | 204篇 |
2020年 | 154篇 |
2019年 | 230篇 |
2018年 | 249篇 |
2017年 | 209篇 |
2016年 | 313篇 |
2015年 | 229篇 |
2014年 | 247篇 |
2013年 | 525篇 |
2012年 | 459篇 |
2011年 | 574篇 |
2010年 | 408篇 |
2009年 | 349篇 |
2008年 | 485篇 |
2007年 | 452篇 |
2006年 | 401篇 |
2005年 | 398篇 |
2004年 | 338篇 |
2003年 | 268篇 |
2002年 | 232篇 |
2001年 | 108篇 |
2000年 | 113篇 |
1999年 | 115篇 |
1998年 | 97篇 |
1997年 | 72篇 |
1996年 | 97篇 |
1995年 | 61篇 |
1994年 | 54篇 |
1993年 | 59篇 |
1992年 | 50篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 27篇 |
1982年 | 22篇 |
1981年 | 28篇 |
1979年 | 21篇 |
1978年 | 25篇 |
1976年 | 24篇 |
1975年 | 26篇 |
1974年 | 19篇 |
1973年 | 17篇 |
1972年 | 19篇 |
1971年 | 14篇 |
排序方式: 共有8195条查询结果,搜索用时 15 毫秒
21.
For any chain Γ the ring NT(Γ,K) of all finitary Γ-matrices ‖a ij ‖ i,jεΓ over an associative ring K with zeros on and above the main diagonal is locally nilpotent and hence radical. If R′=NT(Γ′,K′),R=NT(Γ,K) and either |Γ|<∞ or K is a ring with no zero-divisors, then isomorphisms between rings R and R′, their adjoint groups and associated Lie rings are described. 相似文献
22.
The large N phase transition point is investigated in the heat kernel on the U(N) group with respect to arbitrary boundary conditions. A simple functional relation is found relating the density of eigenvalues of the boundary field to the saddle point shape of the typical Young tableaux in the large N limit of the character expansion of the heat kernel. Both strong coupling and weak coupling phases are investigated for some particular cases of the boundary holonomy. 相似文献
23.
Velislava A Ignatova Sven Van Den Berghe Steven Van Dyck Vladimir N Popok 《Microscopy and microanalysis》2006,12(5):432-437
The oxide scales of AISI 304 formed in boric acid solutions at 300 degrees C and pH = 4.5 have been studied using X-ray photoelectron spectroscopy (XPS) depth profiling. The present focus is depth profile quantification both in depth and chemical composition on a molecular level. The roughness of the samples is studied by atomic force microscopy before and after sputtering, and the erosion rate is determined by measuring the crater depth with a surface profilometer and vertical scanning interferometry. The resulting roughness (20-30 nm), being an order of magnitude lower than the crater depth (0.2-0.5 microm), allows layer-by-layer profiling, although the ion-induced effects result in an uncertainty of the depth calibration of a factor of 2. The XPS spectrum deconvolution and data evaluation applying target factor analysis allows chemical speciation on a molecular level. The elemental distribution as a function of the sputtering time is obtained, and the formation of two layers is observed-one hydroxide (mainly iron-nickel based) on top and a second one deeper, mainly consisting of iron-chromium oxides. 相似文献
24.
The coherent inelastic processes of the type a → b, which may take place in the interaction of hadrons and γ quanta with nuclei at very high energies (the nucleus remains the same), are theoretically investigated. Analytical formulas for the effective cross-section σcoh(a→b) are obtained. 相似文献
25.
S. A. Egorov 《Technical Physics》2006,51(8):999-1003
Calorimetric studies of titanium nickelide show that thermally reversible prestraining does not affect the heat of the B2 → R and R → B2 martensitic transformations. At the same time, reactive stresses induced by straining under constrained conditions are found to decrease the heat of the B19′ → B2, R → B19′, B2 → R, and R → B2 transformations by a factor of 1.16–1.40. A formula describing this effect is proposed. 相似文献
26.
Vladimir Kozlov 《Journal of Functional Analysis》2004,217(2):448-488
We develop an asymptotic theory of nonlinear operator differential equations of an arbitrary order in Banach spaces. The nonlinear part of the equation is written in a divergent form. It is shown that the main term in an asymptotic representation of solutions at infinity satisfies a finite-dimensional dynamical system perturbed by a small nonlocal operator. 相似文献
27.
28.
29.
Tatiana B. Mikenas Vladimir A. Zakharov Lyudmila G. Echevskaya Mikhail A. Matsko 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5057-5066
The effects of polymerization temperature, polymerization time, ethylene and hydrogen concentration, and effect of comonomers (hexene‐1, propylene) on the activity of supported catalyst of composition LFeCl2/MgCl2‐Al(i‐Bu)3 (L = 2,6‐bis[1‐(2,6‐dimethylphenylimino)ethyl] pyridyl) and polymer characteristics (molecular weight (MW), molecular‐weight distribution (MWD), molecular structure) have been studied. Effective activation energy of ethylene polymerization over LFeCl2/MgCl2‐Al(i‐Bu)3 has a value typical of supported Ziegler–Natta catalysts (11.9 kcal/mol). The polymerization reaction is of the first order with respect to monomer at the ethylene concentration >0.2 mol/L. Addition of small amounts of hydrogen (9–17%) significantly increases the activity; however, further increase in hydrogen concentration decreases the activity. The IRS and DSC analysis of PE indicates that catalyst LFeCl2/MgCl2‐Al(i‐Bu)3 has a very low copolymerizing ability toward propylene and hexene‐1. MW and MWD of PE produced over these catalysts depend on the polymerization time, ethylene and hexene‐1 concentration. The activation effect of hydrogen and other kinetic features of ethylene polymerization over supported catalysts based on the Fe (II) complexes are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5057–5066, 2007 相似文献
30.
Victor V. Dodonov Margarita A. Man’ko Vladimir I. Man’ko Apostol Vourdas 《Journal of Russian Laser Research》2007,28(5):404-428
A brief review of the history of ten workshops/conferences on “Squeezed States and Uncertainty Relations” and main achievements
in the related fields of quantum physics for the period from 1991 to 2007 are presented. 相似文献