全文获取类型
收费全文 | 203881篇 |
免费 | 1962篇 |
国内免费 | 591篇 |
专业分类
化学 | 102317篇 |
晶体学 | 3340篇 |
力学 | 9287篇 |
综合类 | 5篇 |
数学 | 22480篇 |
物理学 | 69005篇 |
出版年
2021年 | 1657篇 |
2020年 | 1797篇 |
2019年 | 1998篇 |
2018年 | 2699篇 |
2017年 | 2601篇 |
2016年 | 3765篇 |
2015年 | 2305篇 |
2014年 | 3614篇 |
2013年 | 9087篇 |
2012年 | 7239篇 |
2011年 | 8733篇 |
2010年 | 6041篇 |
2009年 | 5909篇 |
2008年 | 7913篇 |
2007年 | 8079篇 |
2006年 | 7725篇 |
2005年 | 6891篇 |
2004年 | 6425篇 |
2003年 | 5650篇 |
2002年 | 5492篇 |
2001年 | 6424篇 |
2000年 | 4931篇 |
1999年 | 3794篇 |
1998年 | 3038篇 |
1997年 | 3046篇 |
1996年 | 2791篇 |
1995年 | 2614篇 |
1994年 | 2462篇 |
1993年 | 2338篇 |
1992年 | 2691篇 |
1991年 | 2671篇 |
1990年 | 2600篇 |
1989年 | 2396篇 |
1988年 | 2449篇 |
1987年 | 2448篇 |
1986年 | 2279篇 |
1985年 | 2960篇 |
1984年 | 3215篇 |
1983年 | 2631篇 |
1982年 | 2801篇 |
1981年 | 2772篇 |
1980年 | 2639篇 |
1979年 | 2729篇 |
1978年 | 2821篇 |
1977年 | 2819篇 |
1976年 | 2886篇 |
1975年 | 2671篇 |
1974年 | 2644篇 |
1973年 | 2776篇 |
1972年 | 1763篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
961.
B. Blank J. -J. Gaimard H. Geissel K. -H. Schmidt H. Stelzer K. Sümmerer D. Bazin R. Del Moral J. P. Dufour A. Fleury F. Hubert H. -G. Clerc M. Steiner 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):375-379
Total charge-changing cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets, as well as for11Li on C, Sn and Pb targets at about 80 MeV/nucleon. These data are compared to measured total reaction cross sections and Glauber-type calculations using Hartree-Fock density distributions. These comparisons allow to draw conclusions on the proton density distribution of the neutronrich lithium isotopes. The results show that even for the most exotic nucleus11Li the proton distribution is only very weakly influenced by the long tail in the neutron density distribution already established in several experiments. 相似文献
962.
With a suitable combination of ligand-stabilised nanoparticle suspension and ionic salt solutions, it is possible to produce microcrystals that are coated with nanoparticles. The self-assembly process of coating microcrystals by gold nanoparticles (NP) is mediated by the crystal lattice. This is the so-called CLAMS process - a generic process for self-organisation of nanoparticles on the surface of crystals [M. Murugeshan, D. Cunningham, J.-L. Martnez-Albertos, R. Vrcelj, B.D. Moore, Chem. Commun. (2005) 2677]. We are exploring here the structural properties of these self-assembled structures by using different imaging techniques. 相似文献
963.
M. J. Soupioni B. D. Symeopoulos H. V. Papaefthymiou 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(3):441-444
Summary Four different bottled water brands sold in Greece in the winter of 2001-2002 were analyzed for a wide range of chemical elements,
using neutron activation analysis (NAA). The elements Na and Br were determined instrumentally (INAA), whereas the other metals
and trace elements radiochemically (RNAA). The results indicated that the mean level of all the elements determined in the
samples were well within the European Union (EU) directive on drinking water and accomplish the drinking water standards of
the World Health Organisation (WHO) as well as of the Food and Drug Administration (FDA). 相似文献
964.
965.
966.
P. Macko D. Romanini O.V. Naumenko A. Jenouvrier A. Campargue 《Journal of Molecular Spectroscopy》2004,227(1):90-108
The absorption spectrum of natural water vapour around 1.5 μm has been recorded with a typical sensitivity of 5 × 10−10 cm−1 by using a CW-cavity ring down spectroscopy set up based on fibred DFB lasers. A series of 31 DFB lasers has allowed a full coverage of the 6130.8-6748.5 cm−1 (1.63-1.48 μm) region corresponding to the H transparency band of the atmosphere. The line parameters (wavenumber and intensity) of a total of 5190 lines, including 4247 lines of water vapor, were derived by a one by one fit of the lines to a Voigt profile. Different isotopologues of water (H216O, H218O, H217O, and HD16O) present in natural abundance in the sample contribute to the spectrum. For the main isotopologue, H216O, 2130 lines were measured with line intensities as weak as 10−29 cm/molecule while only 926 lines (including a proportion of 30% inaccurate calculated lines) with a minimum intensity of 3 × 10−27 cm/molecule are provided by the HITRAN and GEISA databases. Our comparison in the whole 5750-7965 cm−1 region, has also evidenced that an error in the process of conversion of the intensity units from cm−2/atm to cm−1/(molecule × cm−2) at 296 K, has led to H216O line intensities values listed in the HITRAN-2000 database, systematically 8 % below the original FTS values. The rovibrational assignment was performed on the basis of the ab initio calculations by Schwenke and Partridge with a subsequent refinement and validation using the Ritz combination principle together with all previously measured water transitions relevant to this study. This procedure allowed determining 172, 139, 71, and 115 new energy levels for the H216O, H218O, H217O, and HD16O isotopologues, respectively. The results are compared with the available databases and discussed in regard of previous investigations by Fourier transform spectroscopy. The spectrum analysis has showed that most of the transitions which cannot be assigned to water are very weak and are due to impurities such as carbon dioxide and ammonia, leaving only about 3% of the observed transitions unassigned. The interest of a detailed knowledge of water absorption for trace detectors developed in the 1.5 μm range is underlined: for instance HDO contributes significantly to the considered spectrum while no HDO line parameters are provided by the HITRAN database. 相似文献
967.
S. K. Gorbatsevich I. A. Kaputskaya S. A. Maskevich S. Yu. Mikhnevich N. D. Strekal’ 《Optics and Spectroscopy》2004,97(2):238-243
The fluorescence of solid solutions of CdSe/ZnS quantum dots and the organic dye DODCI is investigated. It is shown that nonradiative transfer of electronic excitation energy to dye molecules, which with some probability lose their acceptor properties as a result of photoisomerization or photodegradation, is responsible for a significant increase in the fluorescence intensity of a donor. The degree of polarization of the donor fluorescence attains values exceeding 0.5, which is due to the difference in the fluorescence quantum yields of donors with different orientations of the oscillator with respect to the electric vector of an excitation light wave. A numerical simulation of the experimentally observed dependences is performed. 相似文献
968.
969.
A. Tseronis D. Tsilimantos N. Uzunoglu 《International Journal of Infrared and Millimeter Waves》2005,26(2):279-295
Radiation phenomena observed in a wedge shape ended dielectric slab waveguide are analyzed using mode matching technique. The case of transverse electric polarization (TE) being parallel to dielectric slab waveguide is assumed. In order to describe the fields in the wedge region, a stack of dielectric plates is assumed and in each layer the fields are expanded in terms of the mixed spectrum of guided and radiated modes. A similar expansion is used in the constant thickness slab waveguide while in free space medium a continuous-radiation mode expansion is used. Then a mode matching approach is applied, incorporating the orthogonality properties of mixed spectrum modes, in order to compute the wave fields inside the dielectric slab waveguide and wedge medium. Mode matching is achieved by discretizing the continuous radiation mode spectrum leading into a numerically stable solution provided a sufficient large number of points are used to convert integrals into finite summations. Numerical computations are carried out for various wedge geometries and shapes including linear and exponential profiles. 相似文献
970.