全文获取类型
收费全文 | 2041篇 |
免费 | 54篇 |
国内免费 | 15篇 |
专业分类
化学 | 1342篇 |
晶体学 | 8篇 |
力学 | 13篇 |
数学 | 387篇 |
物理学 | 360篇 |
出版年
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 29篇 |
2020年 | 26篇 |
2019年 | 19篇 |
2018年 | 29篇 |
2017年 | 26篇 |
2016年 | 53篇 |
2015年 | 40篇 |
2014年 | 61篇 |
2013年 | 113篇 |
2012年 | 99篇 |
2011年 | 104篇 |
2010年 | 79篇 |
2009年 | 65篇 |
2008年 | 119篇 |
2007年 | 86篇 |
2006年 | 118篇 |
2005年 | 99篇 |
2004年 | 79篇 |
2003年 | 67篇 |
2002年 | 69篇 |
2001年 | 38篇 |
2000年 | 44篇 |
1999年 | 24篇 |
1998年 | 36篇 |
1997年 | 12篇 |
1996年 | 24篇 |
1995年 | 17篇 |
1994年 | 31篇 |
1993年 | 16篇 |
1992年 | 27篇 |
1991年 | 26篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 25篇 |
1986年 | 10篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有2110条查询结果,搜索用时 10 毫秒
261.
262.
By a result of A.V. Arhangel'skiǐ and E.G. Pytkeiev, the space C(X) of the continuous real functions on X with the topology of pointwise convergence has tightness ω iff Xn is Lindelöf for every n ∈ ω. In this paper we describe other convergence properties of C(X) (e.g. the Fréchet-Urysohn properly) in terms of covering properties of X.In some cases the equivalence between these properties turn out to be dependent on the set theory we choose. Some open problems are also stated. 相似文献
263.
Ferenc Szidarovszky Lucien Duckstein Istvan Bogardi 《European Journal of Operational Research》1984,15(2):251-258
The management of an aquifer is studied under the assumption that the solution of the multiobjective programming model describing the management problem should satisfy a certain set of axioms. It is shown that a certain class of multiobjective problems may be solved by a game-theoretical concept leading to a single objective quasiconvex programming problem. The method is generalization of Nash's cooperative game theoretical model, and may lean on Zeuther's bargaining process. The methodology is applied to the Transdanubian Karstic region in Hungary where three objectives are present: mining costs, water supply and environmental protection. Results are compared with the solution previously obtained by compromise programming with an l1-norm. It is found that results obtained by the two methods are comparable. 相似文献
264.
Nu Xu I. G. Bearden H. Bøggild J. Boissevain J. Dodd B. Erazmus S. Esumi C. W. Fabjan D. Ferenc D. E. Fields A. Franz J. Gaardhøje O. Hansen D. Hardtke H. van Hecke E. B. Holzer T. Humanic P. Hummel B. V. Jacak R. Jayanti M. Kaneta M. Kopytine M. Leltchouk T. Ljubicic B. Lörstad N. Maeda A. Medvedev M. Murray S. Nishimura H. Ohnishi G. Paic S. U. Pandey F. Piuz J. Pluta V. Polychronakos M. Potekhin G. Poulard A. Sakaguchi J. Simon-Gillo J. Schmidt-Sørensen W. Sondheim M. Spegel T. Sugitate J. P. Sullivan Y. Sumi W. J. Willis K. Wolf N. Xu D. S. Zachary 《Acta Physica Hungarica A》1996,4(1-4):263-270
We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT fo and the chemical potentials (μ q ,μ s ) are extracted and discussed. 相似文献
265.
Ferenc Weisz 《Analysis Mathematica》1996,22(1):65-79
ВВОДьтсь ДВА НОВых кл АссА пРОстРАНстВBMO, ИМ ЕУЩИх БОльшОЕ жНАЧЕНИЕ В тЕОРИИ ИНтЕРпОлИРО ВАНИь, И ДОкАжыВАУтсь НЕкОтОРыЕ сООтНОшЕНИь ЁкВИВАл ЕНтНОстИ Их И ОБыЧНых пРОстРАН стВBMO. ИжУЧАУтсь сООтВЕтстВУУЩИЕ “sharp”Ф УНкцИИ И ОБОБЩАУтсь НЕкОтОР ыЕ тЕОРЕМы гАРсИИ, И ФЕ ФФЕРМАНА И стЕИНА. 相似文献
266.
A. Fonseca K. Hernadi P. Piedigrosso J.-F. Colomer K. Mukhopadhyay R. Doome S. Lazarescu L.P. Biro P. Lambin P.A. Thiry D. Bernaerts J.B. Nagy 《Applied Physics A: Materials Science & Processing》1998,67(1):11-22
The quantities of deposited carbon were measured and the quality of the nanotubes was characterized by means of transmission
electron microscopy and scanning tunneling microscopy. The inner and outer diameters of the nanotubes were also measured and
the diameter distribution histograms were established. The multi-wall straight and coiled nanotubes were found to be quite
regular with an average inner (outer) diameter of 4–7 nm (15–25 nm) and with lengths up to 50 μm. The walls contain concentric
cylindrical graphene sheets separated by the graphitic interlayer distance. The single-wall nanotubes were found as bundles
of hundreds of aligned straight 1-nm-diameter nanotubes with lengths up to 1-μm.
The influence of various parameters such as the method of catalyst preparation, the nature and the pore size of the support,
the nature of the metal, the quantity of catalyst active particles, and the reaction conditions on the nanotubes formation
were studied. The numbers and dimensions of the catalyst active particles dispersed on the support were found to be of importance
in regulating the shape of the produced nanotubes. Following these results, a model of growth mechanism was suggested for
the nanotubes obtained by this method.
Received: 5 January 1998 相似文献
267.
Etsuko Fujita Barry Gordon Manny Hillman Agnes G. Nagy 《Journal of organometallic chemistry》1981,218(1):105-114
The redox potentials for oxidation of ferrocenes with hydrocarbon bridges and of corresponding ketoferrocenes were measured. For the reduced compound correlations were observed between the potentials and the iron to ring distances. For the ketoferrocenes, the importance of proper alignment of the carbonyl with the cyclopentadienyl rings is noted. Other possible relationships are discussed. 相似文献
268.
Ohne Zusammenfassung 相似文献
269.
W. Ochs V. Davidson A. Dzierba A. Firestone W. Ford R. Gomez F. Nagy C. Peck C. Rosenfeld J. Ballam J. Carroll G. Chadwick D. Linglin K. Moffeit R. Ely D. Grether P. Oddone 《Nuclear Physics B》1976,102(3):405-428
We present data on momentum correlations both in and out of the production plane for the reactions π+p→πf+(π+n) and π?p→πf?(π?Δ++). The dissociation products show strikingly similar transverse momentum distributions which in terms of exchange models suggest an equal amount of pion and baryon exchange. For both reactions, we find an approximate factorization in the projectile frame between the transverse momentum of πf and the longitudinal momenta of the dissociation products. Exchange models predict this result equally in both reactions, but it appears much more clearly in the Δ reaction. Finally, we relate the observed longitudinal and transverse momentum distributions in a way suggested by an isotropic decay model. 相似文献
270.
H. De Kerret E. Nagy M. Regler W. Schmidt-Parzefall K.R. Schubert K. Winter A. Brandt H. Dibon G. Flügge F. Niebergall P.E. Schumacher J.J. Aubert C. Broll G. Coignet J. Favier L. Massonnet M. Vivargent W. Bartl G. Neuhofer 《Physics letters. [Part B]》1976,63(4):477-482
New experimental results are reported on diffractive dissociation of protons into (nπ+) in proton-proton collisions at a centre-of-mass energy of . The data were obtained using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. We have searched for resonance contributions and found peaks at mass values of 1.5 GeV, 1.65 GeV, and 2.1 GeV. A dip in is observed at low t and low mass; it is most pronounced for events with neutrons emitted at 90° in the Gottfried-Jackson frame. The correlation between mass and slope depends strongly on θJ. The cross section of the channel pp → pnπ+ is 400 ± 110 μb at , giving an energy dependence of s?0.30±0.07 for isospin exchange zero in this channel. 相似文献