全文获取类型
收费全文 | 2145篇 |
免费 | 42篇 |
国内免费 | 9篇 |
专业分类
化学 | 1395篇 |
晶体学 | 7篇 |
力学 | 26篇 |
数学 | 356篇 |
物理学 | 412篇 |
出版年
2021年 | 16篇 |
2020年 | 22篇 |
2019年 | 17篇 |
2017年 | 14篇 |
2016年 | 28篇 |
2015年 | 38篇 |
2014年 | 38篇 |
2013年 | 78篇 |
2012年 | 56篇 |
2011年 | 70篇 |
2010年 | 65篇 |
2009年 | 49篇 |
2008年 | 112篇 |
2007年 | 84篇 |
2006年 | 106篇 |
2005年 | 81篇 |
2004年 | 72篇 |
2003年 | 75篇 |
2002年 | 68篇 |
2001年 | 57篇 |
2000年 | 51篇 |
1999年 | 38篇 |
1998年 | 37篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 37篇 |
1994年 | 50篇 |
1993年 | 55篇 |
1992年 | 60篇 |
1991年 | 35篇 |
1990年 | 25篇 |
1989年 | 30篇 |
1988年 | 30篇 |
1987年 | 36篇 |
1986年 | 28篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 31篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1978年 | 36篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 21篇 |
1974年 | 29篇 |
1973年 | 24篇 |
1972年 | 16篇 |
1971年 | 24篇 |
排序方式: 共有2196条查询结果,搜索用时 31 毫秒
1.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
2.
We prove that to most of the known hypercyclic operators A on separable Banach spaces there exist compact (compact convex, compact connected) subsets K of E such that each compact (compact convex, compact connected) subset of E can be approximated with respect to Hausdorff's distance by for suitable .
Received July 8, 1997, in final form October 17, 1997 相似文献
3.
H.L. Xu A. Persson S. Svanberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):233-236
New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity
levels belonging to the 4f5d26p and 4f
25d
2 configurations of Ce I and 6 even-parity levels belonging to the 5d26s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II
levels range in energy from 26 545 to 29 102 cm-1, and 42 573 to 48 152 cm-1, respectively.
Received 25 September 2002 Published online 4 March 2003 相似文献
4.
5.
Gerd Herzog Christoph Schmoeger 《Proceedings of the American Mathematical Society》2003,131(11):3507-3509
We prove the converse of Raubenheimer and Rode's Banach algebra version of the Perron-Frobenius Theorem.
6.
Stephan Dahlke Gabriele Steidl Gerd Teschke 《Journal of Fourier Analysis and Applications》2004,10(5):507-539
This article is concerned with frame constructions on domains and manifolds. The
starting point is a unitary group representation which is square integrable modulo a suitable
subgroup and therefore gives rise to a generalized continuous wavelet transform. Then generalized
coorbit spaces can be defined by collecting all functions for which this wavelet transform
is contained in a weighted Lp-space. Moreover, we show that a judicious discretization of the
representation leads to an atomic decomposition and to Banach frames for these coorbit spaces. 相似文献
7.
Ingrid Persson Folke Tjerneld Bärbel Hähn-Hagerdal 《Applied biochemistry and biotechnology》1991,27(1):9-25
Cellulolytic enzyme production in aqueous two-phase systems withTrichoderma reesei Rutgers C30 has been investigated. The influ ence of different phase systems, as well as addition of media compo nents and substrate on enzyme production have been studied. Extractive enzyme production in fed-batch cultivations was per formed in a phase system composed of PEG 8000 5%-Dextran T500 7% with 1% Solka-Floc BW 200 as substrate. The cellulolytic enzyme system was intermittently withdrawn with the top phase. Addition of media components every 24 h and cellulose every 72 h gave an aver age enzyme activity in the withdrawn top phase of 2.2 FPU/mL dur ing 170 h cultivation. The corresponding productivity was 18 FPU/lh. The productivity was increased to 24 FPU/l.h when media compo nents and cellulose were added every 72 h. The average enzyme con centration was then 1.6 FPU/mL. The results are discussed in relation to methods for cellulolytic enzyme production involving immobiliza tion and cell recycling. 相似文献
8.
Georg Süss-Fink Ulf Bodensieck Lisa Hoferkamp Gerd Rheinwald Helen Stoeckli-Evans 《Journal of Cluster Science》1992,3(4):469-478
The reaction of trirutheniumdodecacarbonyl with various thioureas was found to give, depending upon the substituents and the reaction conditions, a large variety of tri-, tetra-, penta-, and hexanuclear ruthenium clusters. The ligand systems observed in the products are derived from the thioureas employed; the fragmentation of the thiourea molecules involve N-H, C-S, C-H, and C-N activation processes. 相似文献
9.
10.