全文获取类型
收费全文 | 15539篇 |
免费 | 489篇 |
国内免费 | 12篇 |
专业分类
化学 | 7594篇 |
晶体学 | 132篇 |
力学 | 338篇 |
综合类 | 1篇 |
数学 | 3602篇 |
物理学 | 4373篇 |
出版年
2021年 | 160篇 |
2020年 | 220篇 |
2019年 | 203篇 |
2018年 | 322篇 |
2017年 | 331篇 |
2016年 | 640篇 |
2015年 | 507篇 |
2014年 | 581篇 |
2013年 | 1211篇 |
2012年 | 772篇 |
2011年 | 921篇 |
2010年 | 579篇 |
2009年 | 515篇 |
2008年 | 523篇 |
2007年 | 444篇 |
2006年 | 308篇 |
2005年 | 184篇 |
2004年 | 237篇 |
2003年 | 250篇 |
2002年 | 263篇 |
2001年 | 224篇 |
2000年 | 227篇 |
1999年 | 209篇 |
1998年 | 193篇 |
1997年 | 190篇 |
1996年 | 179篇 |
1995年 | 165篇 |
1994年 | 160篇 |
1993年 | 154篇 |
1992年 | 169篇 |
1991年 | 140篇 |
1990年 | 153篇 |
1989年 | 146篇 |
1988年 | 147篇 |
1987年 | 135篇 |
1986年 | 136篇 |
1985年 | 181篇 |
1984年 | 193篇 |
1983年 | 148篇 |
1982年 | 165篇 |
1981年 | 164篇 |
1980年 | 166篇 |
1979年 | 173篇 |
1978年 | 167篇 |
1977年 | 166篇 |
1976年 | 164篇 |
1975年 | 142篇 |
1974年 | 160篇 |
1973年 | 146篇 |
1965年 | 128篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
141.
Mladen Pavičić 《Foundations of Physics》1989,19(8):999-1016
Unified quantum logic based on unified operations of implication is formulated as an axiomatic calculus. Soundness and completeness are demonstrated using standard algebraic techniques. An embedding of quantum logic into a new modal system is carried out and discussed.On leave of absence from Department of Mathematics, University of Zagreb, Pot. Pret. 165, YU-41001 Zagreb, Yugoslavia. 相似文献
142.
We discuss productions of scalar gluonium candidates in the radiativeJ/ decays. The branching ratios of such productions are estimated on the basis of the Euler-Heisenberg effective Lagrangian for gluon-photon couplings. We mention that these estimates cannot be expected to be accurate to better than within a factor 2. We show that the radiativeJ/ decays probably invalidate gluoniumgg interpretation of the GAMS meson F0(1590) and a narrow 0++ stateS lying below 1 GeV. However, a possible wide scalar effective gluonium candidate(920) is shown not to be excluded by the data on the decayJ/. We also find that the experimental data about radiativeJ/ decays presumably agree with a recently suggested interpretation of F0(1590) as being approximately a half-and-half mixture of pure 0++ gluoniumgg andSU(3)f singlet quarkoniumq¯q states. 相似文献
143.
The tensor product of two supersingleton representations
n of the Lie superalgebraosp (1, 2n) is studied forn2. The main results are as follows: (a) anticommutators and commutators of the odd generators in
n
n form a skew-symmetric representation of the Lie algebrau(n, n); (b) simple explicit form of all irreducible components of
n
n, which are labelled by a single parameterJ=0, 1, ..., has been found. Each of them is a*-representation ofosp (1, 2n) for which assertion (a) is valid. The dimension of its vacuum subspace equals
, i.e., the nondegenerate vacuum occurs for J=0 only. Basic property of this family of irreducible*-representations of osp(1, 2n) are analogous to those of massless representations of osp(1, 4).Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
144.
A kinematically correct treatment of the full transition amplitude for many-body hypernuclear production is presented. By an example of (+, K+) reaction, effects of the spin-flip amplitude and its interference with the spin-non-flip amplitude are demonstrated and specified for
12
C.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.The discussions with many colleagues are appreciated, in particular those with R. Mach, L. Majling and T. Motoba were of much use. 相似文献
145.
The characteristic length scales for the transport in disordered metals are discussed. Based on a phenomenological model of phase randomising scattering processes, the influence of the phase coherence length on the conductance of ballistic systems is studied. It is argued that the frequency dependence of the conductance of quasi-one dimensional systems can be used in order to determine not only the statistical average but the whole distribution function of the phase coherence length. Various cases of distributions, the -function, the exponential, and the Gamma distribution, are discussed. It is shown that due to quantum coherence effects deviations from the classical (Drude) behavior of the conductance exist. For independent scattering processes the probability distribution function is given by the Poisson distribution function. In this case an expression for the conductance can be derived which contains the ballistic transport, and the result for the exponential distribution. 相似文献
146.
J. Požela A. Namajūnas A. Tamaševičius J. Ulbikas 《Applied Physics A: Materials Science & Processing》1989,48(2):181-188
A method for quantitative characterization of chaotic dynamical systems is discussed. An electronic instrument for determining the number of independent variablesk
*, involved in the motion, is described. It allows one to obtain these in real time from a single observable. The suggested technique has been applied to quantification of strange attractors underlying chaotic instabilities in semi-insulating GaAsCr, and n-Ge, irradiated with high energy electrons. In n-Ge, for instance, the measured numbersk
* range from 2 to 4 depending on control parameters. These measurements reveal the highly deterministic nature of the observed chaotic oscillations. The physical mechanisms responsible for the current instabilities and chaotic behaviour are discussed. 相似文献
147.
Carbon Nanotubes in Analytical Sciences 总被引:1,自引:0,他引:1
Arben Merkoçi 《Mikrochimica acta》2006,152(3-4):157-174
148.
A new algorithm/program has been elaborated for simultaneous processing of different sets of vapour–liquid equilibrium data. The program was tested with six binary hexane + isomeric pentanol systems, each of them measured at three different isobaric conditions and one isothermal system of tert-butyl-methyl-ether + 2-methyl-2-propanol measured at three different temperatures. The correlation uses the maximum likelihood method, taking into account real behaviour of vapour phase. The parameters obtained are valid within the whole temperature range of the data, and are consistent in comparison with those obtained from individual correlations of isobars or isotherms. Results are presented for the Wilson and NRTL equations. 相似文献
149.
Vukadin M. Leovac Goran A. Bogdanović Valerija I. Češljević Ljiljana S. Jovanović Sladjana B. Novaković Ljiljana S. Vojinović-Ješić 《Structural chemistry》2007,18(1):113-119
The ligand, salicylaldehyde Girard-T hydrazonium chloride, [H2SalGT]Cl (1), and two complexes [Cu(HSalGT)X2]·H2O (X = Br(2); Cl(3)) were synthesized and their crystal structures were determined by single-crystal X-ray analysis. In the two isostructural
complexes, the Cu(II) is located in a square-pyramidal environment, with the chelating ligand and one halogen atom in the
basal plane and the second halogen in the apical position. The most apparent structural difference between the 1 and its complexes 2 and 3 is the orientation of the N(CH3)3 group: in 1, it is practically coplanar to the rest of the molecule, while in 2 and 3 it is oriented to the side of the axially bonded halogen, which can be explained by the C–H…X intramolecular interactions.
The compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and electronic absorption
spectra. 相似文献
150.
The redox properties of the system Fe(tmphen)3(II/III) (tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline) have been studied in the solvents nitromethane, acetonitrile, propanediol-1,2-carbonate, dimethylformamide, dimethylacetamide, dimethylsulfoxide and of the systems Fe(phen)3(II/III) (phen=1,10-phenanthroline) and Fe(niphen)3(II/III) (niphen=5-nitro-1,10-phenanthroline) in the solvents nitromethane, acetonitrile, propanediol-1,2-carbonate and acetone. The redox potentials of Fe(tmphen)3(II/III) are nearly independent of the solvent suggesting that the system might be used as a reference redox couple similar to the systems ferrocene/ferricinium or bisbiphenylchromium(0/I). In contrast the redox potentials of Fe(niphen)3(II/III) show a significant decrease with increasing donor number of the solvent which can be explained by nucleophilic attack of solvent molecules at the iron. It is shown that such a mechanism is consistent with the known solvent and salt effects on the kinetics of dissociation of ferroin and ferriin type complexes. 相似文献