全文获取类型
收费全文 | 80577篇 |
免费 | 437篇 |
国内免费 | 393篇 |
专业分类
化学 | 25920篇 |
晶体学 | 812篇 |
力学 | 6782篇 |
数学 | 32451篇 |
物理学 | 15442篇 |
出版年
2018年 | 10450篇 |
2017年 | 10270篇 |
2016年 | 6115篇 |
2015年 | 904篇 |
2014年 | 354篇 |
2013年 | 487篇 |
2012年 | 3902篇 |
2011年 | 10632篇 |
2010年 | 5720篇 |
2009年 | 6108篇 |
2008年 | 6729篇 |
2007年 | 8876篇 |
2006年 | 381篇 |
2005年 | 1438篇 |
2004年 | 1665篇 |
2003年 | 2080篇 |
2002年 | 1109篇 |
2001年 | 277篇 |
2000年 | 326篇 |
1999年 | 184篇 |
1998年 | 224篇 |
1997年 | 181篇 |
1996年 | 242篇 |
1995年 | 154篇 |
1994年 | 111篇 |
1993年 | 138篇 |
1992年 | 87篇 |
1991年 | 91篇 |
1990年 | 83篇 |
1989年 | 92篇 |
1988年 | 86篇 |
1987年 | 83篇 |
1986年 | 82篇 |
1985年 | 85篇 |
1984年 | 86篇 |
1983年 | 70篇 |
1982年 | 70篇 |
1981年 | 71篇 |
1980年 | 82篇 |
1979年 | 69篇 |
1978年 | 58篇 |
1977年 | 48篇 |
1976年 | 37篇 |
1975年 | 39篇 |
1973年 | 48篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
Gerhard Hasslinger Erik S. Rieger 《The Journal of the Operational Research Society》1996,47(5):640-653
This paper deals with approximate analysis methods for open queueing networks. External and internal flows from and to the nodes are characterized by renewal processes with discrete time distributions of their interarrival times. Stationary distributions of the waiting time, the queue size and the interdeparture times are obtained using efficient discrete time algorithms for single server (GI/G/1) and multi-server (GI/D/c) nodes with deterministic service. The network analysis is extended to semi-Markovian representations of each flow among the nodes, which include parameters of the autocorrelation function. 相似文献
913.
Steve PhillipsJr. 《The Journal of the Operational Research Society》1996,47(5):697-701
The paper presents an application oriented procedure for solving the project management duration/resource tradeoff problem. A procedure is presented for reducing a project from a normal to a crash duration state at a minimum amount of additional resource expenditure assuming a linear utilization functions. The procedure is network based using a graphical Cut Search Approach to locate the minimal resource level at each reduction in total project duration. Activity-on-arc networks and flow networks are utilized. The paper is presented for practical application and for conceptual development as compared to a theoretical treatment. 相似文献
914.
Krishna S Kumar 《Pramana》1993,41(1):45-53
We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z0 pole. From measurements of the τ polarization in e+ e?→τ + τ ?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg v e /g a e =0.066±0.015 andg V τ /g A τ =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG τ /G μ =0.996±0.008. 相似文献
915.
A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints. 相似文献
916.
A. E. Asratyan M. Aderholz V. V. Ammosov W. Burkot E. F. Clayton T. Coghen O. Erriquez G. S. Gapienko V. A. Gapienko J. Guy D. Hantke G. T. Jones V. S. Kaftanov U. F. Katz J. Kern V. A. Korotkov S. P. Krutchinin M. A. Kubantsev P. Marage D. B. Miller M. M. Mobayyen D. R. O. Morrison M. Neveu J. Sacton N. Schmitz K. Varvell W. Venus W. Wittek V. G. Zaetz 《Zeitschrift fur Physik C Particles and Fields》1993,58(1):55-60
The diffractive production of charmed strangeD s * and possiblyD s mesons by neutrinos and antineutrinos on nucleons in hydrogen, deuterium and neon targets is observed. The slope parameter of thet distribution is 3.3±0.8 (GeV)?2. The production rate per charged current neutrino interaction with an isoscalar target times the D s + →φτ+ branching fraction is (1.03±0.27)×10?4. 相似文献
917.
Guy Henniart 《Inventiones Mathematicae》1993,113(1):339-350
Résumé SoitF un corps local non archimédien à corps résiduel fini. La conjecture de Langlands locale (prouvée par Laumon, Rapoport et Stuhler quandF est de caractéristique non nulle) associe à une classe d'isomorphisme de représentations irréductibles du groupe de Weil deF une classe d'isomorphisme () de représentations admissibles irréductibles supercuspidales d'un groupe linéaire surF, le groupe GL
n
(F) si est de dimensionn. Nous prouvons dans cet appendice qu'il existe au plus une telle correspondance qui préserve les facteurs de paires et coïncide, en dimension 1, avec l'application donnée par la théorie du corps de classes.
Oblatum 10 XII 1991
Un complément à l'article -elliptic sheaves and the Langlands correspondence par G. Laumon, M. Rapoport et U. Stuhler. 相似文献
Summary LetF be a non-archimedean local field with finite residue field. The local Langlands conjecture (proved by Laumon, Rapoport and Stuhler when the characteristic ofF is positive) associates to an isomorphism class of irreducible representations of the Weil group ofF an isomorphism class () of admissible irreducible supercuspidal representations of some linear group overF, viz. GL n (F) if dim ()=n. In this appendix we prove that there is at most one such correspondence which extends local class field theory in dimension 1, and preserves -factors for pairs.
Oblatum 10 XII 1991
Un complément à l'article -elliptic sheaves and the Langlands correspondence par G. Laumon, M. Rapoport et U. Stuhler. 相似文献
918.
Ron S. Dickson Gary S. Evans Gary D. Fallon 《Journal of organometallic chemistry》1982,236(2):C49-C52
The complexes (η-C5Me5)2Rh2(μ-CO) {μ-η2,η2-C(O)CRCR} are obtained from reactions between (η-C5Me5)2Rh2(CO)2 and the alkynes RCCR (R CF3, CO2Me, or Ph) at 25°C. The molecular geometry of the complex with R CF3 has been established by X-ray diffraction; the bridging 'ene-one' unit adopts a μ-η2,η2 conformation. Other complexes isolated from these reactions include (η-C5Me5)Rh(C6R6) (R CF3, CO2Me), (η-C5Me)2Rh2(C4R4) (R CO2Me) and (η-C5Me5)2Rh2(CO2C2R2) (R Ph). The reaction between (η-C5Me5)2Rh2(CO)2 and C6F5CCC6F5 gives (η-C5Me5)2Rh2(CO)2(C6F5C2C6F5). Mononuclear complexes such as (η-C5Me5)Co(C4R4CO) are the major products isolated from reactions between (η-C5Me5)2CO2(CO)2 and alkynes at 25°C. 相似文献
919.
The extended Koopmans’ theorem is related to Fukui function, which measures the change in electron density that accompanies
electron attachment and removal. Two approaches are used, one based on the extended Koopmans’ theorem differential equation
and the other based directly on the expression of the ionized wave function from the extended Koopmans’ theorem. It is observed
that the Fukui function for electron removal can be modeled as the square of the first Dyson orbital, plus corrections. The
possibility of useful generalizations to the extended Koopmans’ theorem is considered; some of these extensions give approximations,
or even exact expressions, for the Fukui function for electron attachment. 相似文献
920.
Shigeru Arimoto 《Journal of mathematical chemistry》2007,41(3):231-269
The present article is the first part of a series devoted to extending the Repeat Space Theory (RST) to apply to carbon nanotubes
and related molecular networks. Four key problems are formulated whose affirmative solutions imply the formation of the initial
investigative bridge between the research field of nanotubes and that of the additivity and other network problems studied
and solved by using the RST. All of these four problems are solved affirmatively by using tools from the RST. The Piecewise
Monotone Lemmas (PMLs) are cornerstones of the proof of the Fukui conjecture concerning the additivity problems of hydrocarbons.
The solution of the fourth problem gives a generalized analytical formula of the pi-electron energy band curves of nanotube
(a, b), with two new complex parameters c and d. These two parameters bring forth a broad class of analytic curves to which the PMLs and associated theoretical devices apply.
Based on the above affirmative solutions of the problems, a central theorem in the RST, called the asymptotic linearity theorem
(ALT) has been applied to nanotubes and monocyclic polyenes. Analytical formulae derived in this application of the ALT illuminate
in a new global context (i) the conductivity of nanotubes and (ii) the aromaticity of monocyclic polyenes; moreover an analytical
formula obtained by using the ALT provides a fresh insight into Hückel’s (4n+2) rule. The present article forms a foundation of the forthcoming articles in this series.
The present series of articles is closely associated with the series of articles entitled ‘Proof of the Fukui conjecture via
resolution of singularities and related methods’ published in the JOMC. 相似文献