全文获取类型
收费全文 | 4583篇 |
免费 | 258篇 |
国内免费 | 17篇 |
专业分类
化学 | 3353篇 |
晶体学 | 12篇 |
力学 | 105篇 |
数学 | 697篇 |
物理学 | 691篇 |
出版年
2023年 | 92篇 |
2022年 | 65篇 |
2021年 | 128篇 |
2020年 | 214篇 |
2019年 | 174篇 |
2018年 | 87篇 |
2017年 | 90篇 |
2016年 | 194篇 |
2015年 | 147篇 |
2014年 | 158篇 |
2013年 | 210篇 |
2012年 | 336篇 |
2011年 | 418篇 |
2010年 | 172篇 |
2009年 | 135篇 |
2008年 | 275篇 |
2007年 | 233篇 |
2006年 | 242篇 |
2005年 | 170篇 |
2004年 | 150篇 |
2003年 | 125篇 |
2002年 | 106篇 |
2001年 | 36篇 |
2000年 | 43篇 |
1999年 | 21篇 |
1998年 | 33篇 |
1997年 | 16篇 |
1996年 | 28篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 29篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1968年 | 15篇 |
1967年 | 13篇 |
排序方式: 共有4858条查询结果,搜索用时 31 毫秒
1.
2.
Danilov Felix I. Bogdanov Dmytro A. Smyrnova Olena V. Korniy Sergiy A. Protsenko Vyacheslav S. 《Journal of Solid State Electrochemistry》2022,26(4):939-957
Journal of Solid State Electrochemistry - The electrochemical deposition of a nickel–iron alloy from a plating solution based on a deep eutectic solvent (a eutectic mixture of ethylene glycol... 相似文献
3.
Herein, we report an addition to the toolbox for the monitoring and quantification of the hydrolytic decay of pentose-1-phosphates, which are known to be elusive and difficult to quantify. This communication describes how apparent equilibrium shifts of a nucleoside phosphorolysis reaction can be employed to calculate hydrolytic loss of pentose-1-phosphates based on the measurement of post-hydrolysis equilibrium concentrations of a nucleoside and a nucleobase. To demonstrate this approach, we assessed the stability of the relatively stable ribose-1-phosphate at 98 °C and found half-lives of 1.8–11.7 h depending on the medium pH. This approach can be extended to other sugar phosphates and related reaction systems to quantify the stability of UV-inactive and hard-to-detect reaction products and intermediates. 相似文献
4.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
5.
6.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
7.
For a ? R\alpha \in \mathbf{R}, the class of a-\alpha -order spherical harmonic functions in an open set W í\Omega \subseteq Sn-1\mathbf{S}^{n-1}, Ha(W)H^{\alpha }(\Omega ) is defined as the C2-C^{2}-solutions of Dau=0\Delta _{\alpha }u=0; where Da=Ds+a(n+a-2)\Delta _{\alpha }=\Delta _{s}+\alpha (n+\alpha -2) is the spherical Laplace--Beltrami operator of order a\alpha and Ds\Delta _{s} is the radially independent part of the Laplace operator. We obtain a Green's integral formula for the functions in Ha(W)H^{\alpha }(\Omega ) with kernel expressed as a Gegenbauer function. As generalizations, higher order spherical iterated Dirac operators are defined in a polynomial form. Integral representations of the null solutions to these operators and an intertwining formula relating these operators on the sphere and their analogues in Euclidean space are presented. 相似文献
8.
Felix Klein 《Mathematische Annalen》1870,2(2):198-226
Ohne Zusammenfassung 相似文献
9.
10.
Mary E. Neubert DAVID G. ABDALLAH Jr Sandra S. Keast Julie M. Kim Soonnam Lee Ryan M. Stayshich Margaret E. Walsh Rolfe G. Petschek Shin-Tson Wu 《Liquid crystals》2003,30(6):711-731
New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1-4; and X = C n H 2n + 1 , F, CF 3 or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF 3 when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices.
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献