全文获取类型
收费全文 | 4236篇 |
免费 | 165篇 |
国内免费 | 37篇 |
专业分类
化学 | 2715篇 |
晶体学 | 9篇 |
力学 | 170篇 |
数学 | 928篇 |
物理学 | 616篇 |
出版年
2023年 | 22篇 |
2022年 | 70篇 |
2021年 | 94篇 |
2020年 | 102篇 |
2019年 | 90篇 |
2018年 | 89篇 |
2017年 | 66篇 |
2016年 | 179篇 |
2015年 | 148篇 |
2014年 | 180篇 |
2013年 | 275篇 |
2012年 | 314篇 |
2011年 | 323篇 |
2010年 | 157篇 |
2009年 | 198篇 |
2008年 | 270篇 |
2007年 | 259篇 |
2006年 | 219篇 |
2005年 | 202篇 |
2004年 | 205篇 |
2003年 | 144篇 |
2002年 | 102篇 |
2001年 | 47篇 |
2000年 | 38篇 |
1999年 | 35篇 |
1998年 | 39篇 |
1997年 | 37篇 |
1996年 | 49篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 16篇 |
1992年 | 31篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1974年 | 11篇 |
1967年 | 4篇 |
排序方式: 共有4438条查询结果,搜索用时 15 毫秒
181.
182.
Alberto García‐Peñas José M. Gómez‐Elvira Ernesto Pérez María L. Cerrada 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3251-3259
Terpolymers based on propylene with 1‐pentene and 1‐hexene as comonomeric units are satisfactorily synthesized using a metallocene catalyst. Thus, several terpolymers are prepared with distinct overall compositions in comonomers as well as three different 1‐pentene/1‐hexene ratios at a given composition to evaluate the influence on polymerization activity, intrinsic viscosity, and microstructural details. The new trigonal δ polymorph is observed in those quenched terpolymers with a global content in comonomers of about 14 mol %, independently of the ratio between both comonomers. However, preliminary results indicate a profound influence of that ratio on the crystallization rate. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3251–3259 相似文献
183.
Francesco Gasparrini Francesco Maggio Claudio Villani Alberto Brandi Stefano Cicchi K Michał Pietrusiewicz 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract High-performance liquid chromatography utilizing chiral stationary phases (CSPs) is well established as a very simple and efficient method for obtaining discrete amounts of optically active compounds with high e.e., as well as for determining their enantiomeric composition We wish to demonstrate in the present work that a totally synthetic brush-type π-acidic CSP based on a bis(N,N′-3,5-dinitrobenzoyl) derivative of (R,R)- or (S,S)-trans-1,2-diaminocyclohexane as selector can be used successfully to resolve variety of chiral organophosphorus compounds containing stereogenic centers at phosphorus 相似文献
184.
185.
Dr. Mohammed Tariq Dr. Daniel Salavera Prof. Alberto Coronas Prof. Luis P. N. Rebelo Prof. Jose N. Canongia Lopes 《Chemphyschem》2013,14(9):1956-1968
In this work the applicability of four of the most commonly used viscosity mixing rules to [ionic liquid (IL)+molecular solvent (MS)] systems is assessed. More than one hundred (IL+MS) binary mixtures were selected from the literature to test the viscosity mixing rules proposed by 1) Hind (Hi), 2) Grunberg and Nissan (G–N), 3) Herric (He) and 4) Katti and Chaudhri (K–C). The analyses were performed by estimating the average (absolute or relative) deviations, AADs and ARDs, between the available experimental data and the predicted ideal mixture viscosity values obtained by means of each rule. The interaction terms corresponding to the adjustable parameters inherent to each rule were also calculated and their trends discussed. 相似文献
186.
A mass‐conservative staggered immersed boundary model for solving the shallow water equations on complex geometries 下载免费PDF全文
Alberto Canestrelli Aukje Spruyt Bert Jagers Rudy Slingerland Mart Borsboom 《国际流体数值方法杂志》2016,81(3):151-177
In this work, an approach is proposed for solving the 3D shallow water equations with embedded boundaries that are not aligned with the underlying horizontal Cartesian grid. A hybrid cut‐cell/ghost‐cell method is used together with a direction‐splitting implicit solver: Ghost cells are used for the momentum equations in order to prescribe the correct boundary condition at the immersed boundary, while cut cells are used in the continuity equation in order to conserve mass. The resulting scheme is robust, does not suffer any time step limitation for small cut cells, and conserves fluid mass up to machine precision. Moreover, the solver displays a second‐order spatial accuracy, both globally and locally. Comparisons with analytical solutions and reference numerical solutions on curvilinear grids confirm the quality of the method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
187.
Arnald Grabulosa Alberto Mannu Antonio Mezzetti Guillermo Muller 《Journal of organometallic chemistry》2012,696(26):4221-4228
A family of eight neutral, pseudotetrahedral piano-stool ruthenium complexes C, of the type [RuCl2(p-cymene)(PArPhR)] (Ar = 1-naphthyl, 9-phenanthryl and 2-biphenylyl; R = Me, i-Pr, OMe, –CH2SiMe3 and –CH2SiPh3) have been prepared and characterised, including the X-ray crystal structure for C6 (Ar = 2-biphenylyl; R = i-Pr). These complexes catalyse the asymmetric hydrogen transfer reaction of acetophenone in refluxing 2-propanol in the presence of potassium tert-butoxyde, reaching full conversions and up to 45% ee after 24 h towards the S enantiomer of 1-phenylethanol. Cationic complexes formed upon treatment of C with one equivalent of AgSbF6 or (Et3O)PF6 are active in the cyclopropanation reaction of styrene and α-methylstyrene by ethyl diazoacetate. Low to moderate conversions (up to 58%), diastereoselectivities (up to 40% de), and moderate enantioselectivities (up to 69% ee) have been found. For both reactions, bulky complexes and C6 in particular lead to the best results. 相似文献
188.
Alberto S. Cattaneo Pavel Mnev Nicolai Reshetikhin 《Communications in Mathematical Physics》2014,332(2):535-603
In this paper we extend the classical BV framework to gauge theories on spacetime manifolds with boundary. In particular, we connect the BV construction in the bulk with the BFV construction on the boundary and we develop its extension to strata of higher codimension in the case of manifolds with corners. We present several examples including electrodynamics, Yang-Mills theory and topological field theories coming from the AKSZ construction, in particular, the Chern-Simons theory, the BF theory, and the Poisson sigma model. This paper is the first step towards developing the perturbative quantization of such theories on manifolds with boundary in a way consistent with gluing. 相似文献
189.
Inside Cover: Stereoselective Synthesis of 1,3‐Diaminotruxillic Acid Derivatives: An Advantageous Combination of CH‐ortho‐Palladation and On‐Flow [2+2]‐Photocycloaddition in Microreactors (Chem. Eur. J. 1/2016) 下载免费PDF全文
190.