全文获取类型
收费全文 | 26524篇 |
免费 | 2482篇 |
国内免费 | 1642篇 |
专业分类
化学 | 2852篇 |
晶体学 | 42篇 |
力学 | 2802篇 |
综合类 | 275篇 |
数学 | 19953篇 |
物理学 | 4724篇 |
出版年
2024年 | 38篇 |
2023年 | 261篇 |
2022年 | 235篇 |
2021年 | 420篇 |
2020年 | 690篇 |
2019年 | 728篇 |
2018年 | 710篇 |
2017年 | 749篇 |
2016年 | 760篇 |
2015年 | 659篇 |
2014年 | 1120篇 |
2013年 | 2640篇 |
2012年 | 1165篇 |
2011年 | 1452篇 |
2010年 | 1235篇 |
2009年 | 1675篇 |
2008年 | 1636篇 |
2007年 | 1679篇 |
2006年 | 1494篇 |
2005年 | 1258篇 |
2004年 | 1120篇 |
2003年 | 1105篇 |
2002年 | 1081篇 |
2001年 | 859篇 |
2000年 | 866篇 |
1999年 | 795篇 |
1998年 | 682篇 |
1997年 | 623篇 |
1996年 | 401篇 |
1995年 | 320篇 |
1994年 | 283篇 |
1993年 | 216篇 |
1992年 | 197篇 |
1991年 | 153篇 |
1990年 | 141篇 |
1989年 | 97篇 |
1988年 | 86篇 |
1987年 | 74篇 |
1986年 | 66篇 |
1985年 | 102篇 |
1984年 | 132篇 |
1983年 | 66篇 |
1982年 | 97篇 |
1981年 | 97篇 |
1980年 | 87篇 |
1979年 | 75篇 |
1978年 | 67篇 |
1977年 | 48篇 |
1976年 | 43篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated. 相似文献
12.
13.
14.
15.
João Marcos G. Barbosa Milenna K. Fernandes Rodrigues Lurian C. David Taynara C. e Silva Danielly A. Fortuna Lima Naiara Z. Pereira Emmanuel B. D'Alessandro Anselmo E. de Oliveira Paulo H. Jorge da Cunha Maria Clorinda S. Fioravanti Nelson R. Antoniosi Filho 《Biomedical chromatography : BMC》2020,34(11):e4935
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication. 相似文献
16.
AbstractRealistic stochastic modeling is increasingly requiring the use of bounded noises. In this work, properties and relationships of commonly employed bounded stochastic processes are investigated within a solid mathematical ground. Four families are object of investigation: the Sine-Wiener (SW), the Doering–Cai–Lin (DCL), the Tsallis–Stariolo–Borland (TSB), and the Kessler–Sørensen (KS) families. We address mathematical questions on existence and uniqueness of the processes defined through Stochastic Differential Equations, which often conceal non-obvious behavior, and we explore the behavior of the solutions near the boundaries of the state space. The expression of the time-dependent probability density of the Sine-Wiener noise is provided in closed form, and a close connection with the Doering–Cai–Lin noise is shown. Further relationships among the different families are explored, pathwise and in distribution. Finally, we illustrate an analogy between the Kessler–Sørensen family and Bessel processes, which allows to relate the respective local times at the boundaries. 相似文献
17.
18.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
19.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
20.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients 下载免费PDF全文
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献