全文获取类型
收费全文 | 2892篇 |
免费 | 79篇 |
国内免费 | 6篇 |
专业分类
化学 | 1601篇 |
晶体学 | 58篇 |
力学 | 142篇 |
数学 | 596篇 |
物理学 | 580篇 |
出版年
2023年 | 24篇 |
2022年 | 44篇 |
2021年 | 48篇 |
2020年 | 73篇 |
2019年 | 75篇 |
2018年 | 90篇 |
2017年 | 80篇 |
2016年 | 136篇 |
2015年 | 100篇 |
2014年 | 129篇 |
2013年 | 364篇 |
2012年 | 151篇 |
2011年 | 119篇 |
2010年 | 116篇 |
2009年 | 119篇 |
2008年 | 111篇 |
2007年 | 95篇 |
2006年 | 105篇 |
2005年 | 70篇 |
2004年 | 76篇 |
2003年 | 48篇 |
2002年 | 45篇 |
2001年 | 55篇 |
2000年 | 37篇 |
1999年 | 44篇 |
1998年 | 36篇 |
1997年 | 33篇 |
1996年 | 38篇 |
1995年 | 30篇 |
1994年 | 38篇 |
1993年 | 25篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 27篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1975年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有2977条查询结果,搜索用时 15 毫秒
1.
2.
We present some classical solutions to a gauge theory based on quadratically nonlinear Lie algebras without a central term. We observe that instanton-like and meron-like solutions force the internal fields to behave like solitons. 相似文献
3.
Mustafa Çelebier Ertan Şahin Nilgün Ancın Nurşen Altuntaş Öztaş Selma Gül Öztaş 《应用有机金属化学》2007,21(10):viii-viii
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Bahattin Gümgüm Nermin Biricik Feyyaz Durap Ismail Özdemir Nevin Gürbüz Wee Han Ang Paul J. Dyson 《应用有机金属化学》2007,21(8):711-715
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
5.
E. I. Ölmez D. Kut A. N. Bilge I. Ölmez 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):227-231
In ambient air, arsenic to selenium ratio (As/Se) is generally found to be less than 1, except in areas influenced by specific
point sources, such as Cu smelters. However, the annual average of this ratio is found to be much higher than unity in Turkey.
This finding is rather unique and may provide a marker for air masses influenced by the coal-related emissions in Turkey.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献
7.
Montgomery and Vaughan improved a theorem of Erd?s and Fuchs for an arbitrary sequence. Sárközy extended this theorem of Erd?s and Fuchs for two arbitrary sequences which are "near" in a certain sense. Using the idea of Jurkat (differentiation of the generating function), we will extend similarly the result of Montgomery and Vaughan for "sufficiently near" sequences. 相似文献
8.
We consider a multiperiod mean-variance model where the model parameters change according to a stochastic market. The mean
vector and covariance matrix of the random returns of risky assets all depend on the state of the market during any period
where the market process is assumed to follow a Markov chain. Dynamic programming is used to solve an auxiliary problem which,
in turn, gives the efficient frontier of the mean-variance formulation. An explicit expression is obtained for the efficient
frontier and an illustrative example is given to demonstrate the application of the procedure. 相似文献
9.
Simple and convenient methods for determining surface chemical composition of lignocellulosic materials are described. The
methods are based on vapor phase fluorine surface derivatization with either trifluoro acetic anhydride (TFAA), tri-fluoro
ethanol (TFE) or pentafluorophenyl hydrazine (PFPH) and subsequent Electron Spectroscopy for Chemical Analysis (ESCA). Model
cellulosic surfaces with well defined functionalities were used to optimize the derivatization reaction conditions. Detection
and accessibility of surface hydroxyl functional groups were investigated in cotton and regenerated cellulose as models. Carboxymethyl
cellulose (CMC) was used as a model surface for detection and quantification of carboxylic acid groups. Theoretical conversion
curves for derivatization reactions were calculated and used to evaluate the extent of the reactions on the model surfaces.
It was found that the conversion was higher for the regenerated cellulose and CMC than for cotton. The protocols developed
using the model surfaces were applied to a case study on wood fibers with different degrees of complexity, namely dissolving
and chemithermomechanical (CTMP) pulp. Untreated and oxygen-plasma modified pulps were compared with respect to the surface
composition of functional groups. According to the derivatization reactions, functionalities containing oxygen were significantly
increased on the plasma-treated samples. The effect of the treatment was found to be dependent on the type of pulp. Fluorine
derivatization is shown to be an unambiguous method for clear assessment of the chemical functionalities of cellulosic surfaces. 相似文献
10.
Manfred F. Gz 《Mathematical Methods in the Applied Sciences》1994,17(10):787-805
Wave-hierarchy problems appear in a variety of applications such as traffic flows, roll waves down an open inclined channel and multiphase flows. Usually, these are described by the compressible Navier-Stokes equations with specific non-linearities; in a fluidized bed model they contain an additional pressure gradient term and are supplemented by an elliptic equation for this unknown pressure. These equations admit solutions periodic in space as well as in time, i.e. periodic travelling waves. Therefore, the corresponding initial value problem with periodic boundary conditions is solved locally in time in appropriate Sobolev spaces. Some remarks are made concerning global solutions, the occurrence of clusters or voids and the bifurcation of time periodic solutions, respectively. 相似文献