全文获取类型
收费全文 | 35047篇 |
免费 | 714篇 |
国内免费 | 140篇 |
专业分类
化学 | 19695篇 |
晶体学 | 237篇 |
力学 | 1179篇 |
综合类 | 9篇 |
数学 | 5175篇 |
物理学 | 9606篇 |
出版年
2022年 | 407篇 |
2021年 | 522篇 |
2020年 | 491篇 |
2019年 | 441篇 |
2018年 | 539篇 |
2017年 | 480篇 |
2016年 | 832篇 |
2015年 | 687篇 |
2014年 | 774篇 |
2013年 | 1564篇 |
2012年 | 1602篇 |
2011年 | 1866篇 |
2010年 | 1110篇 |
2009年 | 1030篇 |
2008年 | 1596篇 |
2007年 | 1537篇 |
2006年 | 1427篇 |
2005年 | 1809篇 |
2004年 | 1863篇 |
2003年 | 1329篇 |
2002年 | 978篇 |
2001年 | 782篇 |
2000年 | 735篇 |
1999年 | 492篇 |
1998年 | 400篇 |
1997年 | 417篇 |
1996年 | 517篇 |
1995年 | 434篇 |
1994年 | 426篇 |
1993年 | 480篇 |
1992年 | 468篇 |
1991年 | 416篇 |
1990年 | 325篇 |
1989年 | 313篇 |
1988年 | 312篇 |
1987年 | 353篇 |
1986年 | 324篇 |
1985年 | 418篇 |
1984年 | 395篇 |
1983年 | 326篇 |
1982年 | 352篇 |
1981年 | 356篇 |
1980年 | 335篇 |
1979年 | 318篇 |
1978年 | 328篇 |
1977年 | 291篇 |
1976年 | 267篇 |
1975年 | 267篇 |
1974年 | 257篇 |
1973年 | 249篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
Affine Arithmetic: Concepts and Applications 总被引:2,自引:0,他引:2
Affine arithmetic is a model for self-validated numerical computation that keeps track of first-order correlations between computed and input quantities. We explain the main concepts in affine arithmetic and how it handles the dependency problem in standard interval arithmetic. We also describe some of its applications. 相似文献
62.
63.
E. A. Van der Burg 《Fresenius' Journal of Analytical Chemistry》1870,9(1):179-203
Ohne Zusammenfassung 相似文献
64.
65.
66.
W M Niessen M A de Kraa E R Verheij P J Bergers G F La Vos U R Tjaden J van der Greef 《Rapid communications in mass spectrometry : RCM》1989,3(1):1-4
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL. 相似文献
67.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations. 相似文献
68.
M. A. Bertolim M. P. Mello K. A. de Rezende 《Transactions of the American Mathematical Society》2005,357(10):4091-4129
In this article the main theorem establishes the necessity and sufficiency of the Poincaré-Hopf inequalities in order for the Morse inequalities to hold. The convex hull of the collection of all Betti number vectors which satisfy the Morse inequalities for a pre-assigned index data determines a Morse polytope defined on the nonnegative orthant. Using results from network flow theory, a scheme is provided for constructing all possible Betti number vectors which satisfy the Morse inequalities for a pre-assigned index data. Geometrical properties of this polytope are described.
69.
Ping Li Fei Rong Yibing Xie Van Hu Chunwei Yuan 《Journal of Analytical Chemistry》2004,59(10):939-944
S-naproxen imprinted polymer was prepared with acrylamide as a functional monomer, 1,4-butanediyl diacrylate as a new kind of crossliner, and 2,4,6-trimethylbenzoylphenyl-phosphinic acid ethyl ester as photoinitiator. Their UV and IR spectra were applied to study the interactions between the template and the monomer. Binding experiments showed that the S-naproxen imprinted polymer had better recognition capability for the template than that of a blank polymer. The adsorption distribution coefficient KD of S-naproxen on molecularly-imprinted polymer was 153.2 g/mL, and the separation factor was 1.95 when the initial concentration of substrate was 2.0 mmol/L. Scatchard curves suggested that there were two classes of binding sites in the imprinted polymer and only one class in the blank polymer. Computer simulation using Hyperchem showed the existence of the interactions between the template and the functional monomer as well as the models of the complexes formed by the template and the monomer. 相似文献
70.
Alberto Mariani Simone Bidali Stefano Fiori Marco Sangermano Giulio Malucelli Roberta Bongiovanni Aldo Priola 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2066-2072
By combining frontal polymerization and radical‐induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2066–2072, 2004 相似文献