全文获取类型
收费全文 | 27046篇 |
免费 | 582篇 |
国内免费 | 104篇 |
专业分类
化学 | 15335篇 |
晶体学 | 166篇 |
力学 | 840篇 |
综合类 | 9篇 |
数学 | 3728篇 |
物理学 | 7654篇 |
出版年
2023年 | 118篇 |
2022年 | 360篇 |
2021年 | 447篇 |
2020年 | 408篇 |
2019年 | 375篇 |
2018年 | 441篇 |
2017年 | 410篇 |
2016年 | 696篇 |
2015年 | 564篇 |
2014年 | 674篇 |
2013年 | 1099篇 |
2012年 | 1389篇 |
2011年 | 1596篇 |
2010年 | 895篇 |
2009年 | 866篇 |
2008年 | 1347篇 |
2007年 | 1300篇 |
2006年 | 1205篇 |
2005年 | 1611篇 |
2004年 | 1598篇 |
2003年 | 1138篇 |
2002年 | 786篇 |
2001年 | 627篇 |
2000年 | 572篇 |
1999年 | 375篇 |
1998年 | 316篇 |
1997年 | 304篇 |
1996年 | 382篇 |
1995年 | 328篇 |
1994年 | 330篇 |
1993年 | 343篇 |
1992年 | 332篇 |
1991年 | 274篇 |
1990年 | 223篇 |
1989年 | 216篇 |
1988年 | 191篇 |
1987年 | 182篇 |
1986年 | 176篇 |
1985年 | 235篇 |
1984年 | 219篇 |
1983年 | 187篇 |
1982年 | 195篇 |
1981年 | 191篇 |
1980年 | 178篇 |
1979年 | 158篇 |
1978年 | 177篇 |
1977年 | 147篇 |
1976年 | 141篇 |
1974年 | 134篇 |
1973年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough. 相似文献
152.
C. Torres O. Alejos C. de Francisco J.M. Muñoz P. Hernández-Gómez 《Applied Physics A: Materials Science & Processing》2003,77(3-4):543-547
This paper describes a robust and fast fitting procedure applicable for relaxing processes that cannot be understood as a discrete sum of single processes but require an activation energy distribution. The method is based on a set of closed-form expressions that allow the computation of the relaxation parameters directly from the isochronal curves obtained experimentally. The usefulness of this method is checked by analyzing the isochronal curves given by a theoretical energy distribution and the magnetic disaccommodation spectra observed in yttrium iron garnet (YIG) samples. PACS 02.60.Ed; 75.60.Lr; 75.50.Gg 相似文献
153.
Grundel D. A. Oliveira C. A. S. Pardalos P. M. 《Journal of Optimization Theory and Applications》2004,122(3):487-500
The multidimensional assignment problem (MAP) is a NP-hard combinatorial optimization problem, occurring in many applications, such as data association. In this paper, we prove two conjectures made in Ref. 1 and based on data from computational experiments on MAPs. We show that the mean optimal objective function cost of random instances of the MAP goes to zero as the problem size increases, when assignment costs are independent exponentially or uniformly distributed random variables. We prove also that the mean optimal solution goes to negative infinity when assignment costs are independent normally distributed random variables. 相似文献
154.
H. J. Munkholm obtained a generalization for topological manifolds of the famous Borsuk–Ulam type theorem proved by Conner and Floyd. The purpose of this paper is to prove a version of Conner and Floyd's theorem for generalized manifolds. 相似文献
155.
In many Italian archaeological sites dated between the sixth and third centuries BC, unworked lumps of Cu-based materials are sometimes found, the so called Aes Rude, which according to archaeological considerations were appreciated as currency, as a medium of exchange and as a form of saving. The microchemical investigation of these ancient artefacts discloses their nature as apparently not usable for any functional applications or possible use. Indeed, Aes Rude resemble ordinary copper material, but microchemical results indicate that they are constituted by highly ferruginous leaded copper, making them useless for producing other metal objects by means of casting or hot and cold working. Notwithstanding this intrinsic negative feature, the production of these intractable Cu-based alloys was deliberately carried out to maximise the process yield in terms of produced metal from an impure and unselected metal ore by tailoring the smelting process parameters. With these considerations in mind, the microchemical investigation of these ancient iron–copper alloys gives evidence of the passage from the acceptance of an artefact value based on its true nature or potential use to the acceptance of the value based only on its appearance or form irrespective of its present or future use. This information could contribute to a better understanding of the evolution of human thought and economic and social interactions. 相似文献
156.
Javier Fernández de Bobadilla 《Topology》2004,43(4):925-982
In this paper we develop a Morsification Theory for holomorphic functions defining a singularity of finite codimension with respect to an ideal, which recovers most previously known morsification results for non-isolated singularities and generalise them to a much wider context. We also show that deforming functions of finite codimension with respect to an ideal within the same ideal respects the Milnor fibration. Furthermore we present some applications of the theory: we introduce new numerical invariants for non-isolated singularities, which explain various aspects of the deformation of functions within an ideal; we define generalisations of the bifurcation variety in the versal unfolding of isolated singularities; applications of the theory to the topological study of the Milnor fibration of non-isolated singularities are presented. Using intersection theory in a generalised jet-space we show how to interpret the newly defined invariants as certain intersection multiplicities; finally, we characterise which invariants can be interpreted as intersection multiplicities in the above mentioned generalised jet space. 相似文献
157.
F. Tercero J. A. López Fernández E. García L. de Haro M. C. Carter A. Barcia B. Galocha J. L. Besada 《International Journal of Infrared and Millimeter Waves》2003,24(5):669-681
The Beam Mode Expansion (BME) approach for corrugated conical feed horn plus meniscus lens is presented. This approach is useful for providing the radiation pattern as it propagates through an optical system. A developed theoretical model has been verified measuring near and far field of a built horn and lens. These results have been used for designing the optical system of a Cassegrain antenna at 100GHz using the fundamental Gaussian beam mode (GBM) of the new approach. Multimode analysis has been performed with the pre-designed system in order to test the fundamental GBM results. 相似文献
158.
Jan de Vries 《Monatshefte für Mathematik》1901,12(1):45-48
Ohne Zusammenfassung 相似文献
159.
A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively. 相似文献
160.