全文获取类型
收费全文 | 15231篇 |
免费 | 605篇 |
国内免费 | 139篇 |
专业分类
化学 | 8897篇 |
晶体学 | 333篇 |
力学 | 357篇 |
综合类 | 7篇 |
数学 | 2633篇 |
物理学 | 3748篇 |
出版年
2023年 | 85篇 |
2022年 | 146篇 |
2021年 | 221篇 |
2020年 | 226篇 |
2019年 | 329篇 |
2018年 | 341篇 |
2017年 | 347篇 |
2016年 | 610篇 |
2015年 | 491篇 |
2014年 | 603篇 |
2013年 | 1254篇 |
2012年 | 830篇 |
2011年 | 945篇 |
2010年 | 697篇 |
2009年 | 597篇 |
2008年 | 850篇 |
2007年 | 744篇 |
2006年 | 672篇 |
2005年 | 556篇 |
2004年 | 495篇 |
2003年 | 419篇 |
2002年 | 354篇 |
2001年 | 263篇 |
2000年 | 242篇 |
1999年 | 191篇 |
1998年 | 186篇 |
1997年 | 150篇 |
1996年 | 158篇 |
1995年 | 174篇 |
1994年 | 112篇 |
1993年 | 88篇 |
1992年 | 116篇 |
1991年 | 105篇 |
1990年 | 118篇 |
1989年 | 119篇 |
1988年 | 125篇 |
1987年 | 108篇 |
1986年 | 111篇 |
1985年 | 200篇 |
1984年 | 213篇 |
1983年 | 132篇 |
1982年 | 122篇 |
1981年 | 134篇 |
1980年 | 134篇 |
1979年 | 101篇 |
1978年 | 98篇 |
1977年 | 96篇 |
1976年 | 99篇 |
1975年 | 86篇 |
1974年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A. Odrzywołek 《The European Physical Journal C - Particles and Fields》2007,52(2):425-434
The spectrum of the neutrinos produced in the massive photon and longitudinal plasmon decay process has been computed with
four levels of approximation for the dispersion relations. Some analytical formulae in the limit cases are derived. Interesting
conclusions related to previous calculations of the energy loss in stars are presented. The high energy tail of the neutrino
spectrum is shown to be proportional to exp(-E/kT), where E is the neutrino energy and kT is the temperature of the plasma.
PACS 97.90.+j; 97.60.-s; 95.55.Vj; 52.27.Ep 相似文献
62.
We study the Friedmann-Robertson-Walker model with dynamical dark energy modelled in terms of the equation of state p
X
= w
X
(a(z)) ρ
X
in which the coefficient w
X
is parameterized by the scale factor a or redshift z. We use methods of qualitative analysis of differential equations to investigate the space of all admissible solutions for
all initial conditions on the two-dimensional phase plane. We show advantages of representing this dynamics as a motion of
a particle in the one-dimensional potential V(a). One of the features of this reduction is the possibility of investigating how typical big rip singularities are in the
future evolution of the model. The properties of potential function V can serve as a tool for qualitative classification of all evolution paths. Some important features like resolution of the
acceleration problem can be simply visualized as domains on the phase plane. Then one is able to see how large is the class
of solutions (labelled by the inset of the initial conditions) leading to the desired property. 相似文献
63.
V. V. Panić A. B. Dekanski S. K. Milonjić V. B. Mišković-Stanković B. Ž. Nikolić 《Russian Journal of Electrochemistry》2006,42(10):1055-1060
Electrocatalytic properties of RuO2/Ti anode with different coating masses, which are prepared by the alkoxide sol-gel procedure, are investigated in chlorine
and oxygen evolution reactions by polarization measurements and electrochemical impedance spectroscopy in H2SO4 and NaCl electrolytes. According to polarization measurements, the activity of anodes at overpotentials below 100 mV is independent
of coating mass. However, impedance measurements above 100 mV reveal changes in the activity of anodes in chlorine evolution
reaction for different coating masses. The diffusion limitations related to the evolved chlorine are registered in low-frequency
domain at 1.10 V (SCE), diminishing with the increase in potential to the 1.15 V (SCE). The observed impedance behavior is
discussed with respect to the activity model for activated titanium anodes in chlorine evolution reaction involving formation
of gas channels within porous coating structure. Gas channels enhance the mass transfer rate similarly to the forced convection,
which also increases the activity of anode. This is more pronounced for the anode of greater coating mass due to its more
compact surface structure. The more compact structure appears to be beneficial for gas channels formation.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1173–1179.
The text was submitted by the authors in English. 相似文献
64.
65.
66.
A mistake concerning the ultra LI-ideal of a lattice implication algebra is pointed out, and some new sufficient and necessary conditions for an LI-ideal to be an ultra LI-ideal are given. Moreover, the notion of an LI-ideal is extended to MTL-algebras, the notions of a (prime, ultra, obstinate, Boolean) LI-ideal and an ILI-ideal of an MTL-algebra are introduced, some important examples are given, and the following notions are proved to be equivalent in MTL-algebra: (1) prime proper LI-ideal and Boolean LI-ideal, (2) prime proper LI-ideal and ILI-ideal, (3) proper obstinate LI-ideal, (4) ultra LI-ideal.
This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y605389) and K. C. Wong
Magna Fund in Ningbo University. 相似文献
67.
Orotic acid (vitamin B13) is a key intermediate in biosynthesis of the pyrimidine nucleotides in living organisms, moreover, it may serve as the biological carrier for some metal ions. cis-Diammine(orotato)platinum(II), cis-[Pt(C5H2N2O4)(NH3)2] can be considered as a new potential cisplatin analogue. The FT-Raman and FT-IR spectra of the title complex are reported, for the first time. The molecular structure, vibrational frequencies, and the theoretical infrared and Raman intensities have been calculated by the density functional mPW1PW91 method. The detailed vibrational assignment has been made on the basis of the calculated potential energy distribution. The theoretically predicted IR and Raman spectra show very good agreement with experiment. Natural bond orbital (NBO) analyses were performed for cisplatin, carboplatin and the title complex. The results provided new data on the nature of platinum–ligand bonding in these compounds. Strong intramolecular hydrogen bond between the orotate ligand and the coordinated ammonia group stabilizes the structure of the platinum(II) complex. Thus, it is suggested that the orotate ligand in the title complex is more inert to the substitution reactions than the chloride ligands in cisplatin. 相似文献
68.
J. Sładkowski 《International Journal of Theoretical Physics》1991,30(4):517-520
A generalization of theG-theory defined by A. Heilet al. is presented. 相似文献
69.
J. Sładkowski 《International Journal of Theoretical Physics》1991,30(8):1075-1078
The possibility of inflation without any genuine scalar is discussed. It is suggested that drops of primordial plasma may drive inflation. The model, although naive, is consistent with observational data. 相似文献
70.
In this paper we discuss farthest-point problems in which a set or sequence S of n points in the plane is given in advance and can be preprocessed to answer various queries efficiently. First, we give a data structure that can be used to compute the point farthest from a query line segment in O(log2n) time. Our data structure needs O(nlogn) space and preprocessing time. To the best of our knowledge no solution to this problem has been suggested yet. Second, we show how to use this data structure to obtain an output-sensitive query-based algorithm for polygonal path simplification. Both results are based on a series of data structures for fundamental farthest-point queries that can be reduced to each other. 相似文献