全文获取类型
收费全文 | 102816篇 |
免费 | 1172篇 |
国内免费 | 518篇 |
专业分类
化学 | 42286篇 |
晶体学 | 988篇 |
力学 | 7156篇 |
数学 | 34936篇 |
物理学 | 19140篇 |
出版年
2023年 | 182篇 |
2022年 | 266篇 |
2021年 | 363篇 |
2020年 | 485篇 |
2019年 | 471篇 |
2018年 | 10649篇 |
2017年 | 10433篇 |
2016年 | 6743篇 |
2015年 | 1445篇 |
2014年 | 1022篇 |
2013年 | 1517篇 |
2012年 | 5331篇 |
2011年 | 12133篇 |
2010年 | 6587篇 |
2009年 | 6830篇 |
2008年 | 7983篇 |
2007年 | 10037篇 |
2006年 | 1587篇 |
2005年 | 2565篇 |
2004年 | 2627篇 |
2003年 | 2792篇 |
2002年 | 1886篇 |
2001年 | 669篇 |
2000年 | 650篇 |
1999年 | 516篇 |
1998年 | 549篇 |
1997年 | 479篇 |
1996年 | 542篇 |
1995年 | 405篇 |
1994年 | 392篇 |
1993年 | 390篇 |
1992年 | 314篇 |
1991年 | 254篇 |
1990年 | 267篇 |
1989年 | 243篇 |
1988年 | 253篇 |
1987年 | 229篇 |
1986年 | 217篇 |
1985年 | 318篇 |
1984年 | 299篇 |
1983年 | 219篇 |
1982年 | 242篇 |
1981年 | 223篇 |
1980年 | 228篇 |
1979年 | 208篇 |
1978年 | 228篇 |
1977年 | 198篇 |
1976年 | 153篇 |
1974年 | 168篇 |
1973年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Those who have worked in the Royal Institution of Great Britain have, since its foundation in 1799, made significant contributions
to scientific knowledge, to its practical application, and to its communication to a wide variety of audiences. Such work
cannot be carried out in an architectural vacuum, and in this paper we examine how the buildings of the Royal Institution,
20 and 21 Albemarle Street in central London, have shaped the work undertaken within its walls and how, on a number of occasions,
the buildings have been reconfigured to take account of the evolving needs of scientific research and communication.
This paper is based on the Conservation Plan of the Royal Institution that we wrote during 2003. The Conservation Plan did
not examine the land owned by the Royal Institution to the north (i.e., 22 and 23 Albemarle Street; for this area see Richard Garnier, “Grafton Street, Mayfair,” Georgian Group Journal 13 (2003), 210–272), but it did discuss 18 and 19 Albemarle Street. In this paper we concentrate on the core Royal Institution
buildings at 20 and 21 Albemarle Street. Other studies of the relationship of architecture,space, and science include Crosbie
Smith and Jon Agar, ed., Making Space for Science: Territorial Themes in the Shaping of Knowledge (Basingstoke: Macmillan, 1997); Peter Galison and Emily Thompson, ed., The Architecture of Science (Cambridge, Mass.: MIT Press, 1999); and Sophie Forgan,“The architecture of science and the idea of a university,” Studies in History and Philosophy of Science 20 (1989), 405–434.
Frank A.J.L. James is Professor of the History of Science at the Royal Institution; he has written widely on the history of
nineteenth-century science in its social and cultural contexts and is editor of the Correspondence of Michael Faraday. He is President of the British Society for the History of Science. Anthony Peers is an Associate of Rodney Melville and
Partners where he works in the field of building conservation as an architectural historian. He is a Council member of the
Ancient Monument Society. 相似文献
112.
Zhang Tao 《中国科学G辑(英文版)》2007,50(5):591-600
The roles of the magnetic field and electric field of the light are investigated when the light is refracted in the medium.
The model of the electron cloud conductor is presented. Electron cloud in a molecule is treated as a conductor and the Faraday’s
Law is applied to this conductor that is in the alternating magnetic field of the light. dB
M/dt of the light gives rise to an alternating induced current on the electron cloud conductor, and the light exchanges energy,
i.e. the refractive energy, with the electron cloud conductor. Formulas of refractive index, which is the ratio of light speed
in vacuum to that in the medium, are derived with this model. These formulas are tested with several mediums and Langevin’s
diamagnetic susceptibility of helium gas, and the results are in good agreement with the measured data. The anisotropy and
the nonlinearity of the refractive index are explained with the theory described in this work.
Supported by Beijing Science and Technology New Star Program (Grant No. 952870400), the Beijing Municipal Commission of Education
and the Excellent Young Teachers Program of Ministry of Education of China 相似文献
113.
114.
Thomas McCauley 《Pramana》2006,67(4):681-689
I briefly review the present and future status of the burgeoning field of neutrino astronomy. I outline the astrophysics and
particle physics goals, design, and performance of the various current and proposed neutrino telescopes. Also described are
present results and future expectations. 相似文献
115.
This paper is concerned with the d-dimensional cyclic polytope with n vertices, C(n,d), and the set of its triangulations, S(n,d). We show that there is a bijection between S(n,d) and certain partitions of the set of increasing d-tuples on the integers 1 to n–1. We give a combinatorial characterization of the second higher Stasheff–Tamari poset, which is a partial ordering of S(n,d), and we determine its 2-dimension. There is a well-known representation of triangulations of an n-gon by right bracket vectors. We generalize this to cyclic polytopes of higher dimensions. 相似文献
116.
Thomas Marlow 《International Journal of Theoretical Physics》2006,45(7):1247-1257
We attempt a justification of a generalisation of the consistent histories programme using a notion of probability that is valid for all complete sets of history propositions. This consists of introducing Cox's axioms of probability theory and showing that our candidate notion of probability obeys them. We also give a generalisation of Bayes' theorem and comment upon how Bayesianism should be useful for the quantum gravity/cosmology programmes.
PACS: 02.50.Cw;03.65.Ta;04.60.-m. 相似文献
117.
Thomas Andreae 《Journal of Graph Theory》2002,39(4):222-229
For a graph A and a positive integer n, let nA denote the union of n disjoint copies of A; similarly, the union of ?0 disjoint copies of A is referred to as ?0A. It is shown that there exist (connected) graphs A and G such that nA is a minor of G for all n??, but ?0A is not a minor of G. This supplements previous examples showing that analogous statements are true if, instead of minors, isomorphic embeddings or topological minors are considered. The construction of A and G is based on the fact that there exist (infinite) graphs G1, G2,… such that Gi is not a minor of Gj for all i ≠ j. In contrast to previous examples concerning isomorphic embeddings and topological minors, the graphs A and G presented here are not locally finite. The following conjecture is suggested: for each locally finite connected graph A and each graph G, if nA is a minor of G for all n ? ?, then ?0A is a minor of G, too. If true, this would be a far‐reaching generalization of a classical result of R. Halin on families of disjoint one‐way infinite paths in graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 39: 222–229, 2002; DOI 10.1002/jgt.10016 相似文献
118.
Cornelis Van de Panne 《The Journal of the Operational Research Society》1992,43(12):1159-1171
The paper deals with the appropriate form of interaction between two refineries with different demand patterns. This problem can be formulated as finding a decentralized solution of linear programming problems linked by buying and selling activities. The complete problem is first solved for central values of product demands and costs and revenues. The structure of the basis then determines the organization of the interaction in terms of which unit sets quantities and which prices, or whether centralized decisions should be made. If, for expected values of product demand and costs, the structure of the basis is the same then the related organization of trading can be used for day-to-day transactions. For a well-known oil refinery model it is found that, for fairly large demand variations, decentralized interaction is effective, but that the structure of the basis changes easily with crude price variations, and that simulations did not converge for these variations. 相似文献
119.
Transition temperatures (TN1) from the nematic lyotropic liquid-crystalline phase to the isotropic phase were measured for the system cetyltrimethylammonium bromide (CTAB) water in the presence of small amounts of 3-stilbene carboxylic acid (3SC), 4-stilbene carboxylic acid (4SC) and Δ2/2'-bi-(2H-l,4-benzothiazine) (BT). TNI, increases as a function of trans-3SC or trans-4SC concentration, ranging from 01 to 08 wt %, by up to 12°C. A further increase in TNI between 2 and 5°C can be achieved by photochemically converting the solubilized trans stilbene derivatives to the cis isomers. Irradiation of a trans-3SC containing sample at a temperature just above TNl leads to a light-induced phase transition to the lyotropic liquid-crystalline phase. Solubilization of trans-BT causes a slight decrease of TNI while photoisomerization to cis-BT increases TNI by 1°C. 相似文献
120.
Vineet Kumar Rai 《Applied physics. B, Lasers and optics》2007,88(2):297-303
The dependence of temperature on the fluorescence lifetime and fluorescence intensity ratio using Stark sublevels and thermally
coupled (close lying) levels in triply ionized rare earth ions, doped into a variety of glasses and fibers, have been reviewed.
Also, it is claimed that not only for the two closely lying levels of triply ionized rare earth ion of the same kind, but
also for two different triply ionized rare earth ions, having their excited levels very close to each other, may be used to
monitor the temperature.
PACS 42.70.Ce 相似文献