全文获取类型
收费全文 | 322267篇 |
免费 | 4553篇 |
国内免费 | 1084篇 |
专业分类
化学 | 174931篇 |
晶体学 | 4553篇 |
力学 | 13213篇 |
综合类 | 7篇 |
数学 | 38311篇 |
物理学 | 96889篇 |
出版年
2020年 | 2109篇 |
2019年 | 2083篇 |
2018年 | 2139篇 |
2017年 | 2049篇 |
2016年 | 4192篇 |
2015年 | 3543篇 |
2014年 | 4750篇 |
2013年 | 14588篇 |
2012年 | 11179篇 |
2011年 | 13880篇 |
2010年 | 8629篇 |
2009年 | 8562篇 |
2008年 | 12622篇 |
2007年 | 12830篇 |
2006年 | 12395篇 |
2005年 | 11273篇 |
2004年 | 10176篇 |
2003年 | 8996篇 |
2002年 | 8832篇 |
2001年 | 10223篇 |
2000年 | 7841篇 |
1999年 | 6244篇 |
1998年 | 4997篇 |
1997年 | 4833篇 |
1996年 | 4879篇 |
1995年 | 4445篇 |
1994年 | 4200篇 |
1993年 | 4027篇 |
1992年 | 4520篇 |
1991年 | 4364篇 |
1990年 | 4090篇 |
1989年 | 3900篇 |
1988年 | 4184篇 |
1987年 | 3861篇 |
1986年 | 3746篇 |
1985年 | 5413篇 |
1984年 | 5495篇 |
1983年 | 4445篇 |
1982年 | 4840篇 |
1981年 | 4871篇 |
1980年 | 4623篇 |
1979年 | 4745篇 |
1978年 | 4736篇 |
1977年 | 4704篇 |
1976年 | 4670篇 |
1975年 | 4592篇 |
1974年 | 4425篇 |
1973年 | 4577篇 |
1972年 | 2622篇 |
1971年 | 1906篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
54.
55.
P. W. J. Glover 《Transport in Porous Media》2018,124(1):31-56
In this paper, we have significantly modified an existing model for calculating the zeta potential and streaming potential coefficient of porous media and tested it with a large, recently published, high-quality experimental dataset. The newly modified model does not require the imposition of a zeta potential offset but derives its high salinity zeta potential behaviour from Stern plane saturation considerations. The newly modified model has been implemented as a function of temperature, salinity, pH, and rock microstructure both for facies-specific aggregations of the new data and for individual samples. Since the experimental data include measurements on samples of both detrital and authigenic overgrowth sandstones, it was possible to model and test the effect of widely varying microstructural properties while keeping lithology constant. The results show that the theoretical model represents the experimental data very well when applied to model data for a particular lithofacies over the whole salinity, from 10?5 to 6.3 mol/dm3, and extremely well when modelling individual samples and taking individual sample microstructure into account. The new model reproduces and explains the extreme sensitivity of zeta and streaming potential coefficient to pore fluid pH. The low salinity control of streaming potential coefficient by rock microstructure is described well by the modified model. The model also behaves at high salinities, showing that the constant zeta potential observed at high salinities arises from the development of a maximum charge density in the diffuse layer as it is compressed to the thickness of one hydrated metal ion. 相似文献
56.
57.
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
58.
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
59.
60.