全文获取类型
收费全文 | 415篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
化学 | 268篇 |
晶体学 | 1篇 |
力学 | 11篇 |
数学 | 62篇 |
物理学 | 83篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 26篇 |
2010年 | 24篇 |
2009年 | 16篇 |
2008年 | 20篇 |
2007年 | 25篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1970年 | 2篇 |
1966年 | 2篇 |
1957年 | 23篇 |
1956年 | 4篇 |
1888年 | 2篇 |
1885年 | 1篇 |
1884年 | 1篇 |
1880年 | 1篇 |
1879年 | 1篇 |
排序方式: 共有425条查询结果,搜索用时 15 毫秒
191.
Ohne Zusammenfassung 相似文献
192.
193.
194.
F. De Corte A. Simonits F. Bellemans M. C. Freitas S. Jovanović B. Smodiš G. Erdtmann H. Petri A. De Wispelaere 《Journal of Radioanalytical and Nuclear Chemistry》1993,169(1):125-158
This paper reports on the contribution made by some cooperating laboratories to the further development of the k0-method. As to the extensions and improvements, emphasis is put on the availability of an Al–0.1% Au reference material for the k0-standardization of NAA, on the counting of large-diameter samples, on the use of a low-energy photon detector, and on the introduction of the Westcott formalism for the handling of non-1/v (n, ) reactions. A survey is given of a large variety of scientific and industrial applications, including the analysis of biological, geological and geochronological samples, various kinds of reference materials, high-purity products and ceramics, and a number of environmental pollution indicators. As shown, the advantage of the k0-standardization will be fully exploited with an increasing level of automation in NAA laboratories. Eventually, new measurements and evaluations of k0-factors and related nuclear data are given in an Appendix.On leave from: Central Research Institute for Physics (KFKI), H-1525 Budapest 114, POB 49, Hungary. 相似文献
195.
R. Brüggemann M. Petri H. Fischer D. Mauer D. Reinert W. Urban 《Applied physics. B, Lasers and optics》1989,48(2):105-110
A computer-controlled diode laser spectrometer for the 1200 to 2500 cm–1 spectral region is described. The spectrometer has been applied to high resolution spectroscopy of the NCO radical at 5.2 m. The lead-salt diode lasers are cooled to their operating temperature with a temperature adjustable helium evaporation cryostat. Computer-controlled tuning procedures for the frequency tuning of the diode lasers have been developed; they are independent of tables describing the tuning characteristics of the diode lasers. 41 lines of the antisymmetric stretching-vibrationv
3 of the linear NCO radical have been observed. We were able to detect vibration-rotation transitions in both2
1/2 and2
3/2 fine structure sublevels. These measurements led to the precise determination of additional molecular constants. 相似文献
196.
197.
198.
P. E. R. Durigon D. F. S. Petri H. Drings Th. Schimmel M. Bruns 《Colloid and polymer science》2001,279(10):1013-1019
Films of immiscible blends of (PS) and poly(methyl methacrylate) (PMMA) were characterized by contact-angle measurements
with sessile drop and atomic force microscopy (AFM). These blends showed a linear dependence of the contact angles on the
composition, as predicted by Cassie's equation for ideal surfaces. The surface structure investigated by AFM showed low roughness
and phase-separation features. The ratio between the drop radius and the roughness amounted to the order of 104–105. This magnitude seemed to be sufficient to put the PS/PMMA films close to ideality. Upon sulfonation, the wettability and
the microscopic surface roughness of the PS/PMMA blends increased. The treatment with sulfuric acid yielded sulfonated PS
domains on the surface, causing an increase in the surface wettability. The SO3
− groups were evidenced by X-ray photoelectron spectroscopy. The sulfonation of the PS/PMMA blends enables the formation of
multiphase surfaces with hydrophobic, charged and polar domains.
Received: 11 December 2000 Accepted: 6 April 2001 相似文献
199.
Antti Pohjakallio Prof. Petri M. Pihko Ulla M. Laitinen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(37):11325-11339
The formation of 3‐unsubstituted 2‐isoxazolines by means of condensation reactions between α,β‐unsaturated aldehydes and oximes proceeds readily in the presence of catalytic amounts of anilinium salts. Mechanistically, the process involves a fast conjugate addition of the oxime and a slower intramolecular oxime‐transfer reaction. The rate of oxime transfer was found to correlate with the acidity of the catalyst. This finding enabled us to discover an enantioselective process in which the fragile conjugate‐addition product generated in the first stage is rapidly cyclized into the stable isoxazoline under acidic conditions, with conservation of enantiomeric excess. In summary, herein we describe synthetically useful protocols for accessing 3‐unsubstituted 2‐isoxazolines in both the enantioselective and racemic manner. The mechanism of the condensation reaction catalyzed by the anilinium salt was also investigated by NMR spectroscopy experiments in which the effect of differently substituted aldehydes and oximes as well as water on the reaction rate was studied. The results point to the rate‐limiting elimination of water from the 3‐hydroxy‐2‐isoxazolidine intermediate. 相似文献
200.
This paper is about equality of proofs in which a binary predicate formalizing properties of equality occurs, besides conjunction
and the constant true proposition. The properties of equality in question are those of a preordering relation, those of an
equivalence relation, and other properties appropriate for an equality relation in linear logic. The guiding idea is that
equality of proofs is induced by coherence, understood as the existence of a faithful functor from a syntactical category
into a category whose arrows correspond to diagrams. Edges in these diagrams join occurrences of variables that must remain
the same in every generalization of the proof. It is found that assumptions about equality of proofs for equality are parallel
to standard assumptions about equality of arrows in categories. They reproduce standard categorial assumptions on a different
level. It is also found that assumptions for a preordering relation involve an adjoint situation.
相似文献