全文获取类型
收费全文 | 6007篇 |
免费 | 229篇 |
国内免费 | 20篇 |
专业分类
化学 | 4276篇 |
晶体学 | 66篇 |
力学 | 95篇 |
数学 | 626篇 |
物理学 | 1193篇 |
出版年
2023年 | 54篇 |
2022年 | 157篇 |
2021年 | 164篇 |
2020年 | 146篇 |
2019年 | 165篇 |
2018年 | 121篇 |
2017年 | 124篇 |
2016年 | 230篇 |
2015年 | 177篇 |
2014年 | 180篇 |
2013年 | 332篇 |
2012年 | 412篇 |
2011年 | 510篇 |
2010年 | 282篇 |
2009年 | 260篇 |
2008年 | 436篇 |
2007年 | 397篇 |
2006年 | 354篇 |
2005年 | 294篇 |
2004年 | 271篇 |
2003年 | 199篇 |
2002年 | 179篇 |
2001年 | 86篇 |
2000年 | 88篇 |
1999年 | 53篇 |
1998年 | 38篇 |
1997年 | 41篇 |
1996年 | 45篇 |
1995年 | 45篇 |
1994年 | 36篇 |
1993年 | 41篇 |
1992年 | 41篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1974年 | 11篇 |
1972年 | 10篇 |
1969年 | 6篇 |
排序方式: 共有6256条查询结果,搜索用时 15 毫秒
21.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough. 相似文献
22.
SbPO4, a phosphate with a layered structure, was tested as an electrode material for lithium cells spanning the 3.0-0.0 V range. Two main electrochemical processes were detected as extensive plateaus at ca. 1.6 and 0.7 V in galvanostatic measurements. The first process was found to be irreversible, thus excluding a potential intercalation-like mechanism for the reaction and being better interpreted as a decomposition reaction leading to the formation of elemental Sb. This precludes the use of this compound as a cathodic material for lithium cells. By contrast, the process at 0.7 V is reversible and can be ascribed to the formation of lithium-antimony alloys. The best electrochemical response was obtained by cycling the cell at a C/20 discharge rate over the voltage range 1.25-0.25 V. Under these conditions, the cell delivers an average capacity of 165 Ah/kg—a value greater than those reported for other phosphates—upon successive cycling. 相似文献
23.
L.A. Carvalho dos Santos J. Hounie 《Journal of Mathematical Analysis and Applications》2004,299(2):465-493
We study Hardy spaces on the boundary of a smooth open subset or Rn and prove that they can be defined either through the intrinsic maximal function or through Poisson integrals, yielding identical spaces. This extends to any smooth open subset of Rn results already known for the unit ball. As an application, a characterization of the weak boundary values of functions that belong to holomorphic Hardy spaces is given, which implies an F. and M. Riesz type theorem. 相似文献
24.
H. J. Munkholm obtained a generalization for topological manifolds of the famous Borsuk–Ulam type theorem proved by Conner and Floyd. The purpose of this paper is to prove a version of Conner and Floyd's theorem for generalized manifolds. 相似文献
25.
In the present paper we determine the oscillator strength of two-dimensional (2D) D− ions under the influence of a static magnetic field. The results are important for the analysis of the optical transitions observed in semiconductor quantum wells. We have applied the ab initio procedure Hyperspherical Adiabatic Approach, based on the use of hyperspherical coordinates. This approach uses an adiabatic separation of the total wave function that allows accurate energies determination from molecular-like potential curves. The convergence is obtained in a systematic way by the inclusion of non-adiabatic couplings without the need of adjustable parameters. 相似文献
26.
Elizabeth A. Lewis 《Tetrahedron letters》2004,45(15):3059-3062
An efficient synthesis of C-functionalised cyclam macrocycles that employs bisaminal intermediates and allows N-substitution to be controlled is reported. 相似文献
27.
Experts were interviewed to identify criteria for evaluation of vocal performance. A scale was then constructed and inter- and intrajudge reliability assessed. Experts listened to 19 different performances, plus 6 presented a second time. Interjudge reliability for one judge was modest, but increased dramatically as the size of the judge panel increased. The most reliable items were overall score and intonation accuracy. Diction was less reliable than other items. Intrajudge reliability was higher for overall score than for any other item. A factor analysis on the test items yielded factors labelled intrinsic quality, execution, and diction. Another factor analysis, using the experts as variables, revealed two underlying evaluative dimensions. It was found that 13 experts were primarily influenced by execution, and that 8 were mainly affected by intrinsic quality. Interjudge and intrajudge reliabilities of these two groups differed. 相似文献
28.
Gisha Elizabeth Luckachan C. K. S. Pillai 《Journal of polymer science. Part A, Polymer chemistry》2006,44(10):3250-3260
Novel multiblock poly(ester amide)s containing poly(L ‐lactide) and cycloaliphatic amide segments were synthesized from telechelic oligomer of α,ω‐hydroxyl terminated poly(L ‐lactide), 1,3‐cyclohexylbis(methylamine), and sebacoylchloride by the “two‐step” interfacial polycondensation method. The blocky nature of PEAs was established by FTIR and 1H NMR spectroscopies. The effect of relative content of ester and amide segments on the crystallization nature of PEAs was investigated by WAXD and DSC analyses. PEAs having lower content of PLLA, PEA 1 and PEA 2, showed a crystallization pattern analogous to polyamides, whereas PEA 3, having higher content of PLLA, showed two crystalline phases characterized by polyester and polyamide segments. Random nature of PEAs was observed from single Tg values. Biodegradation studies using the enzyme lipase from Candida Cylindracea showed higher degradation rate for PEA 3 than that for PEA 1 and PEA 2. FTIR, 1H NMR, and DSC analyses of the degraded products indicated the involvement of ester linkages in the degradation process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3250–3260, 2006 相似文献
29.
Julio Penin Santos Fernando J.G. Landgraf Geraldo Caixeta Guimarães 《Journal of magnetism and magnetic materials》2006
The paper describes effect of texture on the anisotropy of magnetic properties and shows that an Epstein strip arrangement including strips cut in a direction 45° to the rolling direction gives property values that are closer to the average values than the traditional RD+TD arrangement. 相似文献
30.
Two problems in projectiles are discussed which generate interestingloci. 相似文献