全文获取类型
收费全文 | 65624篇 |
免费 | 15950篇 |
国内免费 | 85篇 |
专业分类
化学 | 67110篇 |
晶体学 | 383篇 |
力学 | 2523篇 |
综合类 | 1篇 |
数学 | 6022篇 |
物理学 | 5620篇 |
出版年
2024年 | 376篇 |
2023年 | 4164篇 |
2022年 | 1826篇 |
2021年 | 2913篇 |
2020年 | 4883篇 |
2019年 | 2652篇 |
2018年 | 2677篇 |
2017年 | 1023篇 |
2016年 | 6314篇 |
2015年 | 6073篇 |
2014年 | 5631篇 |
2013年 | 6640篇 |
2012年 | 4315篇 |
2011年 | 2294篇 |
2010年 | 4328篇 |
2009年 | 4191篇 |
2008年 | 2191篇 |
2007年 | 1810篇 |
2006年 | 995篇 |
2005年 | 839篇 |
2004年 | 724篇 |
2003年 | 640篇 |
2002年 | 497篇 |
2001年 | 401篇 |
2000年 | 345篇 |
1999年 | 253篇 |
1998年 | 257篇 |
1997年 | 253篇 |
1996年 | 273篇 |
1995年 | 342篇 |
1993年 | 327篇 |
1992年 | 251篇 |
1988年 | 260篇 |
1985年 | 323篇 |
1984年 | 319篇 |
1982年 | 264篇 |
1981年 | 294篇 |
1980年 | 349篇 |
1979年 | 298篇 |
1978年 | 303篇 |
1977年 | 402篇 |
1976年 | 474篇 |
1975年 | 545篇 |
1974年 | 550篇 |
1973年 | 357篇 |
1972年 | 407篇 |
1971年 | 377篇 |
1970年 | 557篇 |
1969年 | 427篇 |
1968年 | 470篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Dr.-Ing. M. Millies Dipl.-Ing. St. v. Bose Dipl.-Ing. A. Tokarz Univ.-Prof.Dr.-Ing. D. Mewes 《Heat and Mass Transfer》1994,30(1):17-25
The common methods for calculating the mass transfer across liquid-liquid interfaces in technical applications take into account the mass transfer resistances within the bulk phases. The transfer resistance of the interface and a possible coupling between the momentum and the mass transport is not taken into account. In the present paper a survey is given of theoretical approaches which can describe this coupling and the additional mass transfer resistance. A theory is proposed by Hampe which can be used to explain the coupling between momentum and mass transport employing thermodynamics of irreversible processes. On the basis of this work, the influence of the dilatation of a flat interface on the mass transfer is deduced. It is also concluded from this theory that the diffusion coefficients within the bulk phases are coupled near the thermodynamic equilibrium. 相似文献
52.
53.
The equilibrium statistical volume distribution in foams, which has been previously demonstrated to be the so-called log-normal, is accounted on probability grounds by a scaling law on the bubble's volume time-evolution. This law states that the conditional probability for a given bubble to have the volume v(t + Δt), he assumption that it was v(t), to depend solely on the relationship v(t + Δt)/v(t), and in particular, to be independent of the time t. The theoretical results, however, allow to go further. Indeed, since the time dependece of its parameters (expectation and variance) are given functions of time, only two parameters are necessary to describe completely the foam. 相似文献
54.
Prof. Dr. Leszek Stoch 《Journal of Thermal Analysis and Calorimetry》1992,38(9):1947-1948
55.
56.
57.
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
58.
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
59.
Suchada Suntornchashwej Dr. Khanit Suwanborirux Dr. Kazushi Koga Minoru Isobe Prof. Dr. 《化学:亚洲杂志》2007,2(1):114-122
Malyngamide X ( 1 ), the first (7R)‐lyngbic acid connected to a new tripeptide backbone, was isolated from the Thai sea hare Bursatella leachii. The gross structure of 1 was established on the basis of 1D and 2D NMR and mass spectroscopic data. Combination of the NMR spectroscopic experiments with α‐methoxy‐α‐(trifluoromethyl)phenylacetic acid esters, 2,2,2‐trifluoro‐1‐(9‐anthryl)ethanol chiral solvating agent, and molecular mechanics of 1 and the synthetic molecular fragments allowed us to determine the absolute stereochemistry of all six stereogenic centers without hydrolytic degradation of the compound. Compound 1 displayed moderate cytotoxic, antitubercular, and antimalarial properties. 相似文献
60.
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