全文获取类型
收费全文 | 1392843篇 |
免费 | 25803篇 |
国内免费 | 7761篇 |
专业分类
化学 | 696206篇 |
晶体学 | 20904篇 |
力学 | 76151篇 |
综合类 | 113篇 |
数学 | 246125篇 |
物理学 | 386908篇 |
出版年
2021年 | 13546篇 |
2020年 | 15920篇 |
2019年 | 16034篇 |
2018年 | 15836篇 |
2017年 | 14489篇 |
2016年 | 29203篇 |
2015年 | 21039篇 |
2014年 | 30366篇 |
2013年 | 74218篇 |
2012年 | 40730篇 |
2011年 | 40745篇 |
2010年 | 39686篇 |
2009年 | 41671篇 |
2008年 | 39249篇 |
2007年 | 36017篇 |
2006年 | 38170篇 |
2005年 | 33170篇 |
2004年 | 32943篇 |
2003年 | 30388篇 |
2002年 | 30702篇 |
2001年 | 29704篇 |
2000年 | 25486篇 |
1999年 | 22868篇 |
1998年 | 21152篇 |
1997年 | 21069篇 |
1996年 | 21160篇 |
1995年 | 19175篇 |
1994年 | 18642篇 |
1993年 | 18188篇 |
1992年 | 18229篇 |
1991年 | 18495篇 |
1990年 | 17696篇 |
1989年 | 17770篇 |
1988年 | 17395篇 |
1987年 | 17303篇 |
1986年 | 16208篇 |
1985年 | 22614篇 |
1984年 | 23859篇 |
1983年 | 20054篇 |
1982年 | 21660篇 |
1981年 | 20895篇 |
1980年 | 20221篇 |
1979年 | 20467篇 |
1978年 | 21755篇 |
1977年 | 21363篇 |
1976年 | 21059篇 |
1975年 | 19771篇 |
1974年 | 19434篇 |
1973年 | 19905篇 |
1972年 | 14395篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
851.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献
852.
V. Ballarini G. Barucca E. Bennici C. F. Pirri C. Ricciardi E. Tresso F. Giorgis 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):591
All amorphous silicon-nitride planar optical microcavities operating in the visible range have been grown by plasma enhanced chemical vapor deposition. The luminescence intensity of the N-rich silicon-nitride layer from a microcavity with 6 period distributed Bragg reflectors (DBRs) is two order of magnitude higher than that of the luminescent layer without the cavity. Moreover, a strong directionality of the microcavities emission can be observed. Such results can be ascribed to the anisotropic optical density of states induced in the Fabry–Perot structure. The quality factors of the resonators are strictly correlated to the number of periods of the DBRs. 相似文献
853.
F. Grunewald B. Kunyavskii D. Nikolova E. Plotkin 《Journal of Mathematical Sciences》2003,116(1):2972-2981
We study two-variable Engel-like relations and identities characterizing finite-dimensional solvable Lie algebras and, conjecturally, finite solvable groups and introduce some invariants of finite groups associated with such relations. Bibliography: 29 titles. 相似文献
854.
The method of nonlinear moments, when used to solve the Boltzmann equation, necessitates the calculation of collision integral
matrix elements. The matrix elements are hard to calculate numerically, especially at large indices. The asymptotics of the
matrix elements are constructed. In terms of the model of pseudopower particle interaction, a formula free of summation is
derived. This makes it possible to find the asymptotic behavior of linear and nonlinear elements when two indices are large.
For an arbitrary interaction cross section, asymptotic expansions of linear and nonlinear matrix elements in one index are
obtained. For Maxwellian molecules, asymptotic formulas are derived for three large indices. 相似文献
855.
F. Trani G. Cantele D. Ninno G. Iadonisi 《Physica E: Low-dimensional Systems and Nanostructures》2004,22(4):808-814
In this paper we report on tight-binding calculations of lowest unoccupied molecular orbitals states for silicon ellipsoidal nanocrystals. The electronic structure has been calculated for different nanocrystal shapes either keeping constant or varying the number of silicon atoms. We have found that changing the ellipsoid aspect ratio a non-obvious energy level structure is obtained. The implications for the infrared optical transitions and their relationship with the polarization of the radiation involved are discussed. 相似文献
856.
Relationships between the electrodynamic (wave propagation constants) and quantum-mechanical parameters (probability of induced transitions) of interaction between energy quanta and particles of the medium are derived for dipole and paramagnetic interaction types. It is demonstrated that quantum-mechanical parameters are generally complex. 相似文献
857.
R. K. Bairamov 《Russian Journal of Applied Chemistry》2003,76(10):1699-1701
Influence exerted by additives introduced into the working solution, by iron or copper formedin electric-spark dispersion of these metals and zinc, on the quality of the products obtained in electric erosionwas studied. 相似文献
858.
We establish the existence of a weak solution to the Dirichlet problem belonging to a Sobolev space for nonlinear elliptic equations of second order with right-hand sides from a wide class of functions defined in terms of the logarithmic function. 相似文献
859.
Previous studies of the initial stage of oxidation on clean single crystal of Cu(1 0 0) have been extended to the case of the Cu(1 1 0) surface. The dynamic observation of the nucleation and growth of Cu oxide by means of in situ ultra high vacuum transmission electron microscopy (UHV-TEM) shows a highly enhanced oxidation rate on Cu(1 1 0) surface as compared to Cu(1 0 0). The kinetic data on the nucleation and growth of the three-dimensional oxide islands agree well with our heteroepitaxial model of surface diffusion of oxygen. 相似文献
860.
The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation. 相似文献