全文获取类型
收费全文 | 39558篇 |
免费 | 1458篇 |
国内免费 | 44篇 |
专业分类
化学 | 26594篇 |
晶体学 | 364篇 |
力学 | 709篇 |
数学 | 5791篇 |
物理学 | 7602篇 |
出版年
2023年 | 314篇 |
2022年 | 323篇 |
2021年 | 533篇 |
2020年 | 660篇 |
2019年 | 673篇 |
2018年 | 886篇 |
2017年 | 803篇 |
2016年 | 1459篇 |
2015年 | 1211篇 |
2014年 | 1221篇 |
2013年 | 2545篇 |
2012年 | 2632篇 |
2011年 | 2883篇 |
2010年 | 1713篇 |
2009年 | 1443篇 |
2008年 | 2412篇 |
2007年 | 2302篇 |
2006年 | 2081篇 |
2005年 | 1875篇 |
2004年 | 1530篇 |
2003年 | 1176篇 |
2002年 | 1076篇 |
2001年 | 786篇 |
2000年 | 705篇 |
1999年 | 525篇 |
1998年 | 393篇 |
1997年 | 301篇 |
1996年 | 449篇 |
1995年 | 324篇 |
1994年 | 316篇 |
1993年 | 351篇 |
1992年 | 308篇 |
1991年 | 229篇 |
1990年 | 221篇 |
1989年 | 174篇 |
1988年 | 169篇 |
1987年 | 169篇 |
1986年 | 167篇 |
1985年 | 254篇 |
1984年 | 229篇 |
1983年 | 184篇 |
1982年 | 180篇 |
1981年 | 171篇 |
1980年 | 146篇 |
1979年 | 164篇 |
1978年 | 162篇 |
1977年 | 157篇 |
1976年 | 158篇 |
1975年 | 150篇 |
1973年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Ivan Kojadinovic 《4OR: A Quarterly Journal of Operations Research》2007,5(2):117-142
The application of multi-attribute utility theory based on the Choquet integral requires the prior identification of a capacity
if the utility scale is unipolar, or of a bi-capacity if the utility scale is bipolar. In order to implement a minimum distance
principle for capacity or bi-capacity approximation or identification, quadratic distances between capacities and bi-capacities
are studied. The proposed approach, consisting in solving a strictly convex quadratic program, has been implemented within
the GNU R kappalab package for capacity and nonadditive integral manipulation. Its application is illustrated on two examples.
相似文献
52.
J. J. EGOZCUE J. L. DIAZ-BARRERO V. PAWLOWSKY-GLAHN 《数学学报(英文版)》2006,22(4):1175-1182
The set of probability functions is a convex subset of L1 and it does not have a linear space structure when using ordinary sum and multiplication by real constants. Moreover, difficulties arise when dealing with distances between densities. The crucial point is that usual distances are not invariant under relevant transformations of densities. To overcome these limitations, Aitchison's ideas on compositional data analysis are used, generalizing perturbation and power transformation, as well as the Aitchison inner product, to operations on probability density functions with support on a finite interval. With these operations at hand, it is shown that the set of bounded probability density functions on finite intervals is a pre-Hilbert space. A Hilbert space of densities, whose logarithm is square-integrable, is obtained as the natural completion of the pre-Hilbert space. 相似文献
53.
Generally, in homotopy theory a cylinder object (or, its dual, a path object) is used to define homotopy between morphisms,
and a cone object is used to build exact sequences of homotopy groups. Here, an axiomatic theory based on a cone functor is
given. Suspension objects are associated to based objects and cofibrations, obtaining homotopy groups referred to an object
and relative to a cofibration, respectively. Exact sequences of these groups are built. Algebraic and particular examples
are given. We point out that the main results of this paper were already stated in [3], and the purpose of this article is
to give full details of the foregoing. 相似文献
54.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
55.
Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was
investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer
and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider
constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various
types of compounds is documented by various examples. 相似文献
56.
Anelia Achanova Ivan Zhelyazkov Tsvetelina Petrova 《Czechoslovak Journal of Physics》2004,54(2):211-223
Microwave discharges produced by travelling/standing electromagnetic waves have drawn considerable attention in recent years
due to their wide application in microelectronic industry. Here are presented the axial distributions of the electrons and
ions as well as those of excited atoms in an argon microwave discharge at a low gas pressure (400 mTorr) sustained by a 2.45
GHz travelling dipolar electromagnetic wave. The numerical calculations are based on a self-consistent kinetic-electrodynamic
model and the results obtained are in a good agreement with the experimental data. The model yields also the magnitude of
the wave power sustaining the discharge and the axial profiles of all electromagnetic-wave characteristics and the axial distribution
of the neutral gas temperature. 相似文献
57.
J. Mlynár J. Ongena The EFDA JET Contributions I. Duran M. Hron R. Pánek V. Petržílka F. Žáček 《Czechoslovak Journal of Physics》2004,54(3):C28
JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years. 相似文献
58.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels. 相似文献
59.
In the present paper, Daubechies' wavelets and the computation of their scaling coefficients are briefly reviewed. Then a new method of computation is proposed. This method is based on the work [7] concerning a new orthonormality condition and relations among scaling moments, respectively. For filter lengths up to 16, the arising system can be explicitly solved with algebraic methods like Gröbner bases. Its simple structure allows one to find quickly all possible solutions. 相似文献
60.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献