全文获取类型
收费全文 | 641235篇 |
免费 | 6085篇 |
国内免费 | 1704篇 |
专业分类
化学 | 324983篇 |
晶体学 | 9564篇 |
力学 | 31659篇 |
综合类 | 19篇 |
数学 | 84856篇 |
物理学 | 197943篇 |
出版年
2021年 | 5694篇 |
2020年 | 6229篇 |
2019年 | 7057篇 |
2018年 | 9850篇 |
2017年 | 10079篇 |
2016年 | 13622篇 |
2015年 | 7516篇 |
2014年 | 12384篇 |
2013年 | 28660篇 |
2012年 | 22352篇 |
2011年 | 26320篇 |
2010年 | 19517篇 |
2009年 | 19465篇 |
2008年 | 24596篇 |
2007年 | 24373篇 |
2006年 | 22364篇 |
2005年 | 21853篇 |
2004年 | 20504篇 |
2003年 | 17770篇 |
2002年 | 16560篇 |
2001年 | 17750篇 |
2000年 | 13722篇 |
1999年 | 10613篇 |
1998年 | 9136篇 |
1997年 | 8968篇 |
1996年 | 8403篇 |
1995年 | 7611篇 |
1994年 | 7574篇 |
1993年 | 7289篇 |
1992年 | 7858篇 |
1991年 | 8235篇 |
1990年 | 7884篇 |
1989年 | 7790篇 |
1988年 | 7584篇 |
1987年 | 7423篇 |
1986年 | 7088篇 |
1985年 | 9103篇 |
1984年 | 9485篇 |
1983年 | 8068篇 |
1982年 | 8455篇 |
1981年 | 7841篇 |
1980年 | 7490篇 |
1979年 | 8089篇 |
1978年 | 8354篇 |
1977年 | 8200篇 |
1976年 | 8144篇 |
1975年 | 7833篇 |
1974年 | 7677篇 |
1973年 | 8082篇 |
1972年 | 5756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Modification of Paving Asphalts with Sulfur 总被引:2,自引:0,他引:2
Syroezhko A. M. Begak O. Yu. Fedorov V. V. Gusarova E. N. 《Russian Journal of Applied Chemistry》2003,76(3):491-496
Sulfur dissolved in oil components of asphalt is a binder, filler, and chemical co-reagent at once. The structure of sulfur-extended asphalt depends on its formula and heating temperature. Road pavement based on sulfur-extended asphalt demonstrates higher durability as compared to that with the conventional binders. 相似文献
992.
Operators on manifolds with corners that have base configurations with geometric singularities can be analysed in the frame of a conormal symbolic structure which is in spirit similar to the one for conical singularities of Kondrat'ev's work. Solvability of elliptic equations and asymptotics of solutions are determined by meromorphic conormal symbols. We study the case when the base has edge singularities which is a natural assumption in a number of applications. There are new phenomena, caused by a specific kind of higher degeneracy of the underlying symbols. We introduce an algebra of meromorphic edge operators that depend on complex parameters and investigate meromorphic inverses in the parameter-dependent elliptic case. Among the examples are resolvents of elliptic differential operators on manifolds with edges. 相似文献
993.
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
994.
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
995.
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
996.
O. V. Sizova E. P. Sokolova V. I. Baranovskii D. A. Rozmanov O. A. Tomashenko 《Journal of Structural Chemistry》2004,45(5):762-770
Ab initio MP2 calculations with several basis sets proved the existence of a stable benzonitrile dimer with a planar structure and a short contact between the H atom of one molecule and the N atom of another. The structure is greatly stabilized by attraction between the neighboring oppositely directed dipoles and donor-acceptor interaction between the orbital of the lone electron pair of the N′ atom and the vacant antibonding orbital localized on the C-H bond.Original Russian Text Copyright © 2004 by O. V. Sizova, E. P. Sokolova, V. I. Baranovskii, D. A. Rozmanov, and O. A. Tomashenko__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 807–815, September–October, 2004. 相似文献
997.
The effect of bacterial and fungal activities on organic matter degradation in Brazilian soils was studied by a microcalorimetric method. Bacteria and fungi isolated from tropical soils and added to: Rhodic eutrudox (R), Typic eutrudox (V) and Quartzipsamment (Q) soils amended separately with moisture (control) (A) and 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 23 μg of trifluralin (T) were investigated. The number of colony forming units in soil suspension was quantified by microscopy and inoculated in respective soil. All processes were measured at intervals of 7 days over a period of 35 days. The exothermic thermal effect (μJ) per cm3 of bacteria or fungi per gram of dry soil, respectively, for each substrate was: [(9±1), (4±1)] RA; [(478±24), (105±5)] RE; [(121±6), (71±4)] RL; [(121±6), (71±4)] RH; [(8±1); (3±1)] RT; [(10±1), (9±1] VA; [(347±17), (261±13)] VE; [(71±4), (28±1)] VL; [(22±1), (33±2)] VH; [(7±1), (10±1)] VT; [(19±1), (12±1)] QA; [(1301±65), (46±2)] QE; [(89±4), (9±1)] QL; [(130±7), (11±1)] QH; [(32±2), (8±1)] QT. The calorimetric values are higher for bacteria than for fungi. In general, the results showed higher activities in the soil amended with cattle manure than with other additives. 相似文献
998.
H. H. Salah M. Darwish A.-S. F. Obada 《International Journal of Theoretical Physics》2003,42(3):549-567
The odd excited negative binomial states are introduced using the photon creation operator by repeated application on negative binomialstates. These states interpolate between the odd displaced Fock states and the odd excited pure thermal states. In this paper both squeezing phenomena (normal squeezing and amplitude squared squeezing) are discussed. Besides discussion of the Glauber second-order correlation function, investigations are carried out for the quasi-probability distribution functions (Wigner function and Q-function). Finally the Pegg-Barnett phase probability distribution is computed for these states. 相似文献
999.
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
1000.
We prove that any irreducible faithful representation of an almost torsion-free Abelian group G of finite rank over a finitely generated field of characteristic zero is induced from an irreducible representation of a finitely generated subgroup of the group G. 相似文献