全文获取类型
收费全文 | 4082篇 |
免费 | 234篇 |
国内免费 | 16篇 |
专业分类
化学 | 3368篇 |
晶体学 | 16篇 |
力学 | 67篇 |
数学 | 425篇 |
物理学 | 456篇 |
出版年
2023年 | 42篇 |
2022年 | 52篇 |
2021年 | 176篇 |
2020年 | 141篇 |
2019年 | 120篇 |
2018年 | 59篇 |
2017年 | 56篇 |
2016年 | 175篇 |
2015年 | 179篇 |
2014年 | 163篇 |
2013年 | 236篇 |
2012年 | 337篇 |
2011年 | 371篇 |
2010年 | 210篇 |
2009年 | 172篇 |
2008年 | 291篇 |
2007年 | 257篇 |
2006年 | 254篇 |
2005年 | 181篇 |
2004年 | 189篇 |
2003年 | 148篇 |
2002年 | 125篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有4332条查询结果,搜索用时 406 毫秒
161.
Roberto Andreani Gabriel Haeser María Laura Schuverdt Paulo J. S. Silva 《Mathematical Programming》2012,135(1-2):255-273
In this work we introduce a relaxed version of the constant positive linear dependence constraint qualification (CPLD) that we call RCPLD. This development is inspired by a recent generalization of the constant rank constraint qualification by Minchenko and Stakhovski that was called RCRCQ. We show that RCPLD is enough to ensure the convergence of an augmented Lagrangian algorithm and that it asserts the validity of an error bound. We also provide proofs and counter-examples that show the relations of RCRCQ and RCPLD with other known constraint qualifications. In particular, RCPLD is strictly weaker than CPLD and RCRCQ, while still stronger than Abadie’s constraint qualification. We also verify that the second order necessary optimality condition holds under RCRCQ. 相似文献
162.
This paper proposes to obtain homogeneous and stable blends of oligo(9,9-dioctylfluorene)-co-phenylene (OF), a conjugated oligomer with strong tendency of formation of excimers in the solid state, and nitrile rubber (NBR). This rubber protection reduces the formation of polymer excimers in the films. The fluorene oligomer was synthesized via Suzuki reaction and incorporated in the nitrile rubber. The films were formed by spin coating and casting techniques on the proportions of 1, 5, 10, 20 and 50 % (w/w) of OF in the nitrile rubber (NBR). The structural, optical and thermal properties of the films were evaluated with infrared, UV–Vis, fluorescence and thermogravimetry, respectively. The nitrile rubber proved to be essential for the preparation of homogeneous and stable films, since it was not possible to obtain films with only fluorene using the above-mentioned techniques. Furthermore, luminescent properties of OF are unchanged and the excimers formation in the solid state decrease suggesting the efficiency of nitrile rubber as the matrix for making films. 相似文献
163.
An efficient numerical procedure for solving linear second order Volterra integro-differential equations is presented herein.
The scheme is based on B-spline collocation and cubature formulas. Analysis is accompanied by numerical examples. Results
confirm reliability and efficiency of the proposed algorithm. 相似文献
164.
Laura C. Oliveira Cibele B. Zamboni Edson A. Pessoa Fernanda T. Borges 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):395-398
In this investigation ions in serum, urine and kidney of Wistar rats (control group) and Wistar with Acute Renal Insufficiency
(ARI) were quantified using instrumental neutron activation analysis. The measurements in serum and urine were performed before,
during and after ischemia-induced ARI. The measurements in kidney were performed for the control and ARI groups. Also, a comparative
analysis between the concentration ratios before, during and after ARI was performed in urine and serum samples for both groups.
The variations results for Cu in serum and I in urine, before and after ischemia-induced ARI, suggest that these elements
must be also investigated in renal dysfunction. 相似文献
165.
166.
167.
168.
Cibele B. Zamboni Laura C. Oliveira Luciana Kovacs Sabrina Metairon 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):389-393
In this study the neutron activation analysis (NAA) technique was applied to determine Ca and Mg in whole blood from inhabitants
of Brazil for the purpose of establishing concentration ranges indicative of sex and age. The initiative to perform these
measurements is related to the increase in heart disease. According to recent statistics from WHO, the average is one death
due to heart attack in Brazil, every five minutes. The measures were performed considering lifestyle factors (non-smokers,
non-drinkers and no history of toxicological exposure) of Brazilian inhabitants. A healthy group constituted of male (n = 94) and female (n = 84) blood donors, ages between 18 and 70 years and above 50 kg, was selected from the blood banks and hematological laboratories
of Brazil. The influence of sex was also investigated considering several age ranges (18–29, 30–40, 41–50, >50 years). The
results show significant differences when a comparison is made by sex and age and may be useful to identify or prevent clinical
diseases. These results emphasize the need to perform periodic evaluation of Ca and Mg in blood. 相似文献
169.
170.
Rachel A. Hegemann Laura M. Smith Alethea B.T. Barbaro Andrea L. Bertozzi Shannon E. Reid George E. Tita 《Physica A》2011,390(21-22):3894-3914
We propose an agent-based model to simulate the creation of street gang rivalries. The movement dynamics of agents are coupled to an evolving network of gang rivalries, which is determined by previous interactions among agents in the system. Basic gang data, geographic information, and behavioral dynamics suggested by the criminology literature are integrated into the model. The major highways, rivers, and the locations of gangs’ centers of activity influence the agents’ motion. We use a policing division of the Los Angeles Police Department as a case study to test our model. We apply common metrics from graph theory to analyze our model, comparing networks produced by our simulations and an instance of a Geographical Threshold Graph to the existing network from the criminology literature. 相似文献