全文获取类型
收费全文 | 156801篇 |
免费 | 1772篇 |
国内免费 | 396篇 |
专业分类
化学 | 85394篇 |
晶体学 | 2513篇 |
力学 | 6242篇 |
综合类 | 3篇 |
数学 | 15604篇 |
物理学 | 49213篇 |
出版年
2021年 | 1171篇 |
2020年 | 1319篇 |
2019年 | 1375篇 |
2018年 | 1832篇 |
2017年 | 1896篇 |
2016年 | 2990篇 |
2015年 | 1864篇 |
2014年 | 2689篇 |
2013年 | 6799篇 |
2012年 | 5303篇 |
2011年 | 6522篇 |
2010年 | 4562篇 |
2009年 | 4537篇 |
2008年 | 6031篇 |
2007年 | 5768篇 |
2006年 | 5566篇 |
2005年 | 5090篇 |
2004年 | 4595篇 |
2003年 | 4265篇 |
2002年 | 4167篇 |
2001年 | 5671篇 |
2000年 | 4092篇 |
1999年 | 3200篇 |
1998年 | 2232篇 |
1997年 | 2328篇 |
1996年 | 2194篇 |
1995年 | 2031篇 |
1994年 | 2018篇 |
1993年 | 1843篇 |
1992年 | 2322篇 |
1991年 | 2395篇 |
1990年 | 2232篇 |
1989年 | 2195篇 |
1988年 | 2168篇 |
1987年 | 2197篇 |
1986年 | 1993篇 |
1985年 | 2491篇 |
1984年 | 2510篇 |
1983年 | 2025篇 |
1982年 | 2029篇 |
1981年 | 1859篇 |
1980年 | 1850篇 |
1979年 | 2143篇 |
1978年 | 2214篇 |
1977年 | 2153篇 |
1976年 | 2083篇 |
1975年 | 1952篇 |
1974年 | 1942篇 |
1973年 | 1973篇 |
1972年 | 1298篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
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
33.
34.
35.
Inside Cover: Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies (Chem. Eur. J. 14/2015) 下载免费PDF全文
36.
Lubomír Havlk Jan Fbry Margarida Henriques Michal Duek 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):623-630
The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α‐NaFeO2 structure type in agreement with the ratio of the ionic radii r3+/r+. KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S—S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S2−) and the bond‐valence sums. 相似文献
37.
38.
39.
Kleandrova Valeria V. Rojas-Vargas Julio A. Scotti Marcus T. Speck-Planche Alejandro 《Molecular diversity》2022,26(5):2523-2534
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with... 相似文献
40.
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr... 相似文献