全文获取类型
收费全文 | 20137篇 |
免费 | 543篇 |
国内免费 | 118篇 |
专业分类
化学 | 14387篇 |
晶体学 | 190篇 |
力学 | 389篇 |
综合类 | 1篇 |
数学 | 2993篇 |
物理学 | 2838篇 |
出版年
2022年 | 165篇 |
2021年 | 205篇 |
2020年 | 301篇 |
2019年 | 295篇 |
2018年 | 188篇 |
2017年 | 181篇 |
2016年 | 410篇 |
2015年 | 361篇 |
2014年 | 455篇 |
2013年 | 941篇 |
2012年 | 995篇 |
2011年 | 1290篇 |
2010年 | 636篇 |
2009年 | 534篇 |
2008年 | 1028篇 |
2007年 | 1103篇 |
2006年 | 1087篇 |
2005年 | 1052篇 |
2004年 | 896篇 |
2003年 | 754篇 |
2002年 | 743篇 |
2001年 | 260篇 |
2000年 | 261篇 |
1999年 | 235篇 |
1998年 | 227篇 |
1997年 | 261篇 |
1996年 | 287篇 |
1995年 | 229篇 |
1994年 | 218篇 |
1993年 | 249篇 |
1992年 | 210篇 |
1991年 | 190篇 |
1990年 | 168篇 |
1989年 | 146篇 |
1988年 | 145篇 |
1987年 | 158篇 |
1986年 | 136篇 |
1985年 | 207篇 |
1984年 | 253篇 |
1983年 | 179篇 |
1982年 | 223篇 |
1981年 | 243篇 |
1980年 | 187篇 |
1979年 | 186篇 |
1978年 | 216篇 |
1977年 | 162篇 |
1976年 | 168篇 |
1975年 | 153篇 |
1974年 | 167篇 |
1973年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Matthew M. Malwitz Paul D. Butler Lionel Porcar Drew P. Angelette Gudrun Schmidt 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):3102-3112
The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO–CNA networklike solutions were compared with previously reported PEO–LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer–clay interactions, were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3102–3112, 2004 相似文献
52.
Doubly tunable sum frequency generation (SFG) spectra demonstrate that the water molecules at gold/electrolyte interface change their orientation with applied potential. At negative potentials, water molecules in the double layer align with their oxygen atom pointing to the solution. As potential became positive to be close to the potential of zero charge (PZC), the SFG signal decreased, suggesting the OH groups of the water molecule are either in random orientation or parallel to the electrode. As potential became more positive than the PZC, the SFG signal increased again with the oxygen-up orientation as same as in the negative potential region, indicating that water molecules interact with the adsorbed sulfate anions. The peak position of the SFG spectra indicates a relatively disordered state of water molecules at the gold electrode surface, in contrast to the previously observed ice-like structure of water at electrolyte/oxide interfaces. 相似文献
53.
54.
Transverse flow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow
and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge
volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant.
The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity.
This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modifications
in the scaling laws are presented. 相似文献
55.
56.
F. Rampf K. Binder W. Paul 《Journal of polymer science. Part A, Polymer chemistry》2006,44(18):2542-2555
We present simulation results for the phase behavior of a single chain for a flexible lattice polymer model using the Wang-Landau sampling idea. Applying this new algorithm to the problem of the homopolymer collapse allows us to investigate not only the high temperature coil–globule transition but also an ensuing crystallization at lower temperature. Performing a finite size scaling analysis on the two transitions, we show that they coincide for our model in the thermodynamic limit corresponding to a direct collapse of the random coil into the crystal without intermediate coil–globule transition. As a consequence, also the many chain phase diagram of this model can be predicted to consist only of gas and crystal phase in the limit of infinite chain length. This behavior is in agreement with findings on the phase behavior of hard-sphere systems with a relatively short-ranged attractive square well. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2542–2555, 2006 相似文献
57.
Suzanne J. Dilly Steven J. Carlisle Andrew J. Clark Andrew R. Shepherd Stephen C. Smith Paul C. Taylor Andrew Marsh 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2248-2259
A practical and divergent synthesis of supported [1,3,5]‐triazine dendritic molecules on Wang resin, PEGA resin, SynPhase? Lanterns, and silica gel is described. The alkylamine linkers used allow derivatization with functionality for both synthetic (e.g., supported reagent and scavenger activity) and chemical biology applications. The use of supported intermediates allows differentiation of symmetric linkers without the need for protecting group chemistry. The synthetic route uses inexpensive, readily available starting materials in a straightforward and scaleable strategy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2248–2259, 2006 相似文献
58.
59.
Two problems in projectiles are discussed which generate interestingloci. 相似文献
60.
Francisco-Javier Muñoz-Delgado Victoriano Ramirez-González Paul Sablonnière 《分析论及其应用》1995,11(1):62-71
In this work we study linear polynomial operators preserving some consecutive i-convexities and leaving invariant the polynomials
up to a certain degree. First, we study the existence of an incom patibility between the conservation of certain i-convexities
and the invariance of a space of polynomials. Interpolation properties are obtained and a theorem by Berens and DeVore about
the Bernstein's operator is extended. Finally, from these results a generalized Bernstein's operator is obtained.
This work was supported by Junta de Andalucia. Grupo de investigación: Matemática Aplicada. Código: 1107 相似文献