全文获取类型
收费全文 | 233551篇 |
免费 | 2012篇 |
国内免费 | 801篇 |
专业分类
化学 | 117270篇 |
晶体学 | 4000篇 |
力学 | 10771篇 |
综合类 | 1篇 |
数学 | 25537篇 |
物理学 | 78785篇 |
出版年
2020年 | 1789篇 |
2019年 | 2044篇 |
2018年 | 2724篇 |
2017年 | 2652篇 |
2016年 | 3921篇 |
2015年 | 2400篇 |
2014年 | 3976篇 |
2013年 | 10084篇 |
2012年 | 7548篇 |
2011年 | 9437篇 |
2010年 | 6708篇 |
2009年 | 6641篇 |
2008年 | 8736篇 |
2007年 | 8764篇 |
2006年 | 8305篇 |
2005年 | 7542篇 |
2004年 | 6945篇 |
2003年 | 6124篇 |
2002年 | 6073篇 |
2001年 | 7097篇 |
2000年 | 5383篇 |
1999年 | 4239篇 |
1998年 | 3572篇 |
1997年 | 3483篇 |
1996年 | 3305篇 |
1995年 | 3013篇 |
1994年 | 2956篇 |
1993年 | 3050篇 |
1992年 | 3157篇 |
1991年 | 3337篇 |
1990年 | 3088篇 |
1989年 | 3028篇 |
1988年 | 3068篇 |
1987年 | 2958篇 |
1986年 | 2805篇 |
1985年 | 3816篇 |
1984年 | 4008篇 |
1983年 | 3203篇 |
1982年 | 3412篇 |
1981年 | 3346篇 |
1980年 | 3235篇 |
1979年 | 3344篇 |
1978年 | 3437篇 |
1977年 | 3362篇 |
1976年 | 3457篇 |
1975年 | 3147篇 |
1974年 | 3157篇 |
1973年 | 3196篇 |
1972年 | 2238篇 |
1971年 | 1851篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
821.
We calculate the temperature-dependent energy gap in the magnetic excitations spectrum of the two-dimensional antiferromagnet in the presence of a staggered magnetic field, using the nonlinear sigma model. 相似文献
822.
The permittivity and loss of poly(methyl methacrylate) (PMMA) network crosslinked with trimethylol-1,1,1 propane and its interpenetrating network polymers with 10, 34, and 50% (by weight) poly(urethane) have been measured from 100 to 400 K over a frequency range of 12 to 1 × 105 Hz. Two relaxation processes, γ and β, are observed in the PMMA network, and a third process, αpu, in the 10% poly(urethane) IPN. At higher concentrations of poly(urethane), the γ process is removed from the temperature-frequency range of our study. Crosslinking in pure PMMA slows the segmental motions involved in the β process and raises its activation energy. Physical aging of the 10 wt% poly(urethane)-PMMA causes its γ process to become indiscernible and the αpu process to become better resolved. A discussion of these results in terms of local regions of segmental motion is provided. 相似文献
823.
F. Jancik B. Seifert C. K. Laird W. Czysz J. S. Dunnett W. Schmidt und P. Bachhausen 《Fresenius' Journal of Analytical Chemistry》1987,327(7):747-755
Ohne Zusammenfassung 相似文献
824.
C. Scheidenberger K. Beckert P. Beller F. Bosch C. Brandau D. Boutin L. Chen B. Franzke H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov Yu. A. Litvinov M. Mazzocco G. Münzenberg F. Nolden W. R. Plaß M. Steck B. Sun H. Weick M. Winkler 《Hyperfine Interactions》2006,173(1-3):61-66
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams
stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for
high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.
P. Beller, deceased. 相似文献
825.
Mechanisms for the formation of toxisterol A are suggested. The connection between the conformation of the initial previtamin and the stereochemistry of the reaction products is discussed.Lensoviet Leningrad Technological Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 225–229, March–April, 1989. 相似文献
826.
A new and accurate relationship for the shear modulus in the fiber direction of unidirectional fiber composites is derived, based on the Kerner model concepts but not using its approximate relationships. Furthermore, this model is extended by taking into account the mesophase between the fiber and the matrix accomodating smoothly the mechanical properties between neighbouring phases. The introduction of the mesophase results in an improvement of the theoretical predictions, which now approach close to experimental values for the moduli of different fibrous composites. 相似文献
827.
P. Lichard 《Zeitschrift fur Physik C Particles and Fields》1987,37(1):125-137
We propose a method of evaluating the soft dilepton production rate in hadron-nucleus and nucleus-nucleus collisions at high energies based on summing the contributions from quark-antiquark systems (chains) created in individual hadron-nucleon interactions. The individual contributions are determined by using the square dependence of the soft dilepton production rate on hadron multiplicity predicted for hadron-hadron collisions by the soft-quarkannihilation model and observed recently inpp collisions at the CERN ISR. The possibility of additional contributions originating from the annihilation of quarks and antiquarks that belong to different chains is taken into account in a phenomenological way, which nevertheless enables to correlate different phenomena in soft dilepton production. More detailed predictions are given for proton-nucleus collisions at 200 GeV/c. 相似文献
828.
Marek Pękała Jan Mucha Benedicte Vertruyen Rudi Cloots Marcel Ausloos 《Journal of magnetism and magnetic materials》2006
Samples of La0.7Ca0.3Mn1−xGaxO3 with x=0, 0.025, 0.05 and 0.10 were prepared by standard solid-state reaction. They were first characterized chemically, including the microstructure. The magnetic properties and various transport properties, i.e. the electrical resistivity, magnetoresistivity (for a field below 8 T), thermoelectric power and thermal conductivity measured each time on the same sample, are reported. The markedly different behaviour of the x=0.1 sample from those with a smaller Ga content, is discussed. The dilution of the Mn3+/Mn4+ interactions with Ga doping considerably reduces the ferromagnetic double exchange interaction within the manganese lattice leading to a decrease of the Curie temperature. The polaron binding energy varies from 224 to 243 meV with increased Ga doping. 相似文献
829.
We prove that a finite unary algebra with at least two operation symbols is a homomorphic image of a (finite) subdirectly
irreducible algebra if and only if the intersection of all its subalgebras which have at least two elements is nonempty.
While working on this paper the first and the third authors were partially supported by the Grant Agency of the Czech Republic,
grant #201/02/0594, and by the institutional grant MSM0021620839; the second author was supported by the Ministry of Science,
Technologies and Development of Republic of Serbia, grant no. 1227. 相似文献
830.
Summary Certain characteristics of a two-fiber sensor device, of the type proposed by Papaet al. for sea water turbidity monitorship, are examined. The extension of medium from which most of the received backscattered
power originates is investigated, together with possible effects of multiple scattering on the received power. Laboratory
measurements testing the results of the analysis are reported.
Riassunto Sono esaminate alcune caratteristiche di un sensore a due fibre, del tipo di quello proposto da Papaet al. per il monitoraggio della torbidità dell'acqua di mare. è stata studiata l'estensione della zona del mezzo da cui proviene la maggior parte della radiazione retrodiffusa ricevuta. Sono stati considerati effetti di diffusione multipla. I risultati dell'analisi sono stati controllati con misure in laboratorio.
Резюме Исследуются некоторые характеристики дву-qh-нитевого датчика, предложенного Папа и др. для мониторирования мутности морской воды. Исследуется расширение зоны в среде, из которой формируется основная часть рассеянного назад излучения. Также рассматриваются эффекты многократного рассеяния. На основе лабораторных измерений проводится проверка результатов анализа.相似文献