全文获取类型
收费全文 | 17746篇 |
免费 | 771篇 |
国内免费 | 158篇 |
专业分类
化学 | 11807篇 |
晶体学 | 109篇 |
力学 | 467篇 |
数学 | 3067篇 |
物理学 | 3225篇 |
出版年
2023年 | 141篇 |
2022年 | 115篇 |
2021年 | 342篇 |
2020年 | 418篇 |
2019年 | 405篇 |
2018年 | 263篇 |
2017年 | 231篇 |
2016年 | 633篇 |
2015年 | 493篇 |
2014年 | 585篇 |
2013年 | 912篇 |
2012年 | 1191篇 |
2011年 | 1378篇 |
2010年 | 714篇 |
2009年 | 611篇 |
2008年 | 1046篇 |
2007年 | 997篇 |
2006年 | 991篇 |
2005年 | 894篇 |
2004年 | 780篇 |
2003年 | 548篇 |
2002年 | 566篇 |
2001年 | 226篇 |
2000年 | 192篇 |
1999年 | 180篇 |
1998年 | 139篇 |
1997年 | 157篇 |
1996年 | 204篇 |
1995年 | 133篇 |
1994年 | 148篇 |
1993年 | 160篇 |
1992年 | 129篇 |
1991年 | 130篇 |
1990年 | 111篇 |
1989年 | 113篇 |
1988年 | 119篇 |
1987年 | 97篇 |
1986年 | 108篇 |
1985年 | 141篇 |
1984年 | 139篇 |
1982年 | 148篇 |
1981年 | 152篇 |
1980年 | 125篇 |
1979年 | 118篇 |
1978年 | 149篇 |
1977年 | 131篇 |
1976年 | 103篇 |
1975年 | 101篇 |
1974年 | 100篇 |
1973年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
991.
Dr. Raphaël Lamare Dr. Romain Ruppert Prof. Corinne Boudon Prof. Laurent Ruhlmann Dr. Jean Weiss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16071-16081
Polyoxometalates (POMs) can act as unique reservoirs for multiple electron transfers. As POMs display only weak absorption in the visible spectrum, they can be associated with chromophores such as porphyrins and porphyrin antennae. In this Minireview, the research dedicated to the combination of porphyrins and polyoxometalates is put in context and the state of the art identifying the challenges addressed in the optimization of hybrid materials for applications is detailed. 相似文献
992.
Vickie Tsui Daniel F. Ortwine Jeffrey M. Blaney 《Journal of computer-aided molecular design》2017,31(3):287-291
Computational chemistry/informatics scientists and software engineers in Genentech Small Molecule Drug Discovery collaborate with experimental scientists in a therapeutic project-centric environment. Our mission is to enable and improve pre-clinical drug discovery design and decisions. Our goal is to deliver timely data, analysis, and modeling to our therapeutic project teams using best-in-class software tools. We describe our strategy, the organization of our group, and our approaches to reach this goal. We conclude with a summary of the interdisciplinary skills required for computational scientists and recommendations for their training. 相似文献
993.
In the spirit of the Hamiltonian QR algorithm and other bidirectional chasing algorithms, a structure-preserving variant of
the implicit QR algorithm for palindromic eigenvalue problems is proposed. This new palindromic QR algorithm is strongly backward
stable and requires less operations than the standard QZ algorithm, but is restricted to matrix classes where a preliminary
reduction to structured Hessenberg form can be performed. By an extension of the implicit Q theorem, the palindromic QR algorithm
is shown to be equivalent to a previously developed explicit version. Also, the classical convergence theory for the QR algorithm
can be extended to prove local quadratic convergence. We briefly demonstrate how even eigenvalue problems can be addressed
by similar techniques.
D. S. Watkins partly supported by Deutsche Forschungsgemeinschaft through Matheon, the DFG Research Center Mathematics for key technologies in Berlin. 相似文献
994.
Structural rearrangement and stiffening of hydrophobically modified supramolecular hydrogels during thermal annealing 下载免费PDF全文
Chao Wang Clinton G. Wiener Yiming Yang R. A. Weiss Bryan D. Vogt 《Journal of Polymer Science.Polymer Physics》2017,55(13):1036-1044
Dynamic crosslinks formed by thermoreversible associations provide an energy dissipation mechanism to toughen hydrogels. However, the details of the organization of these crosslinks impact the hydrogel properties through constraints on the network chain conformation. The physical crosslinks generated by hydrophobic association of the 2‐(N‐ethylperfluorooctane‐sulfonamido)ethyl methacrylate (FOSM) groups in a random copolymer of N,N‐dimethylacrylamide (DMA) and FOSM provide a simple system to investigate how the hydrogel structure (as determined from small angle neutron scattering impacts the mechanical properties of the hydrogel. The initial hydration of the copolymer at 25 °C leads to a kinetically trapped structure with large‐scale heterogeneities. Heating the hydrogel at 60 °C, which is above the glass transition temperature for the FOSM domains, allows the hydrogel structure to rearrange to reduce the density of network defects and the structural heterogeneities. That effectively increases the crosslink density of the network, which stiffens the hydrogel and decreases the swelling at equilibrium at 25 °C. The processing history determines how the hydrophobes aggregate to form the physically crosslinked network, whose structure defines the mechanical properties of these hydrogels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1036–1044 相似文献
995.
Bin Du Adam Langlois Daniel Fortin Christine Stern Pierre D. Harvey 《Journal of Cluster Science》2012,23(3):737-751
The title cluster is luminescent at 77?K and exhibits an unsaturated site for binding anions when the counter ion is PF6 ?. A series of five non-luminescent metalloporphyrins exhibiting carboxylate anchoring groups were synthesized and characterized. These are the sodium salts of the 5-carboxyphenyl-tri-10,15,20-tolyl-, trans-di-5,10-carboxyphenyl-di-15,20-tolyl-, and tetra-5,10,15,20-carboxyphenyl(metallo)porphyrin (metallo?=?chloroiron(III), nickel(II)) anions. Evidence for supramolecular assemblies between the carboxylates and the cluster is provided by 31P NMR and UV?Cvis spectroscopy. The binding constant, K1n, extracted from the UV?Cvis data via Benesi-Hildebrand, Scott and Scatchard plots are approximately 21,000?±?5,000?M?1 for the nickel(II) species, in agreement with the previously reported zinc(II) ones (K11?=?20,000?±?2,000?M?1), but those for the chloroiron(III) are measured to be lower (12,500?±?3,500?M?1). This association is accompanied by a complete quenching of the luminescence of the cluster which can only be due to an efficient energy transfer to the d?Cd states of the chloroiron(III) and nickel(II) species but an electron transfer from the nickel(II)-containing chromophore to the cluster is also possible. This work demonstrates the profound effect that supramolecular interactions may have on the photophysical properties despite the long donor?Cacceptor separation. 相似文献
996.
997.
998.
Nikolay Djourelov Corine Bas Daniel Sillou Rosario Benavente Ernesto Pérez María L. Cerrada 《Journal of Polymer Science.Polymer Physics》2010,48(18):1994-2002
Copolymers of propylene and 1‐octadecene synthesized by a metallocene catalyst were characterized by PALS, WAXD, DSC, and density measurements. The change in the sizes and the number density of free‐volume holes as a function of the 1‐octadecene content were compared to the master laws published for copolymers of propylene with α‐olefins of shorter lengths. It was found that the samples were separated into two groups. The first set of samples obeyed the master laws while the second group deviated. This behavior was explained by the difference in the copolymer structure. The WAXD analysis confirmed the separation as well. The deviation was explained as due to the mesomorphic crystalline structure of the second group of samples, in contrast to the monoclinic one for the first group, which was a result of the relatively fast cooling from the molten state and from the high comonomer molar content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1994–2002, 2010 相似文献
999.
1000.
Corrigendum: Effect of hexyl substituent groups on photophysical and electrochemical properties of the poly[(9,9‐dioctyfluorene)‐2,7‐Diyl‐alt‐(4,7‐bis (3‐hexylthien‐5‐Yl)‐2,1,3‐benzothiadiazole)‐2′,2″‐diyl] 下载免费PDF全文