全文获取类型
收费全文 | 1928篇 |
免费 | 57篇 |
国内免费 | 6篇 |
专业分类
化学 | 1278篇 |
晶体学 | 10篇 |
力学 | 99篇 |
数学 | 175篇 |
物理学 | 429篇 |
出版年
2022年 | 12篇 |
2021年 | 21篇 |
2020年 | 34篇 |
2019年 | 26篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 42篇 |
2015年 | 33篇 |
2014年 | 32篇 |
2013年 | 80篇 |
2012年 | 100篇 |
2011年 | 139篇 |
2010年 | 64篇 |
2009年 | 75篇 |
2008年 | 116篇 |
2007年 | 105篇 |
2006年 | 93篇 |
2005年 | 73篇 |
2004年 | 72篇 |
2003年 | 56篇 |
2002年 | 51篇 |
2001年 | 36篇 |
2000年 | 33篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 42篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 31篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 29篇 |
1977年 | 14篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1972年 | 8篇 |
1968年 | 11篇 |
排序方式: 共有1991条查询结果,搜索用时 31 毫秒
121.
L. Funke F. Dnau J. Dring P. Kemnitz E. Will G. Winter 《Physics letters. [Part B]》1983,120(4-6):301-304
A shape transition from a probably asymmetric shape at low excitation to a more axial-symmetric shape above 21/2+ has been found in 81Kr. This shape change and the drastic increase of the M1 transition probabilities above spin 21/2 are attributed to the alignment of two g9/2 protons. 相似文献
122.
The magnetization reversal of ultrathin Co films on Cu(001) has been investigated by grazing ion scattering and magneto-optical Kerr effect. Differences in the behavior of surface and bulk magnetization are found and attributed to the reduced coordination and site symmetry at the surface. The reversal behavior of the surface magnetization depends on the chemical surface composition. For pure Co films, the reversal of the bulk magnetization is preceded by a complete reversal of the surface magnetization. A particular magnetic state of the surface is suggested as a precursor for magnetization reversal. 相似文献
123.
The structure and magnetism of ultrathin Fe films epitaxially grown on a Cu(001) surface are investigated by grazing scattering of fast H and He atoms or ions. By making use of a new variant of ion beam triangulation based on the detection of the number of emitted electrons, we obtain direct information on the structure of the film surface. We observe for room temperature growth a dominant and defined fcc-like structure. Complex surface reconstructions as reported in recent STM and LEED studies are observed only for cooling and H2 dosing. 相似文献
124.
Schreiner E Nicolini C Ludolph B Ravindra R Otte N Kohlmeyer A Rousseau R Winter R Marx D 《Physical review letters》2004,92(14):148101
The temperature-dependent behavior of a solvated oligopeptide, GVG(VPGVG), is investigated. Spectroscopic measurements, thermodynamic measurements, and molecular dynamics simulations find that this elastinlike octapeptide behaves as a two-state system that undergoes an "inverse temperature" folding transition and reentrant unfolding close to the boiling point of water. A molecular picture of these processes is presented, emphasizing changes in the dynamics of hydrogen bonding at the protein/water interface and peptide backbone librational entropy. 相似文献
125.
A. Khoukaz I. Geck C. Quentmeier H.-H. Adam A. Budzanowski R. Czyżykiewicz D. Grzonka L. Jarczyk K. Kilian P. Kowina N. Lang T. Lister P. Moskal W. Oelert C. Piskor-Ignatowicz T. Rożek R. Santo G. Schepers T. Sefzick S. Sewerin M. Siemaszko J. Smyrski A. Strzałkowski A. Täschner P. Winter M. Wolke P. Wüstner W. Zipper 《The European Physical Journal A - Hadrons and Nuclei》2004,20(2):345-350
The
-meson production in the reaction
has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross-sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near-threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final-state interaction and Coulomb effects. The obtained angular distribution of the
-mesons is also consistent with pure s-wave production.Received: 11 August 2003, Revised: 14 November 2003, Published online: 6 April 2004PACS:
13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy
GeV) - 13.85.Lg Total cross-sections - 25.40.-h Nucleon-induced reactions 相似文献
126.
Kemmitt T Al-Salim NI Gainsford GJ Bubendorfer A Waterland M 《Inorganic chemistry》2004,43(20):6300-6306
Aqueous titanium citrate solutions were prepared from the reaction of citric acid with titanium 2-propoxide in a range of molar ratios. Solutions containing two or fewer citrates per titanium resulted in the slow crystallization of an insoluble titanium oxo-citrate complex. Single-crystal X-ray analysis identified the species as Ti(8)O(10)(citrate)(4)(H(2)O)(12).14H(2)O.3HOPr(i)(), crystallized in the tetragonal space group I4(1)/a, with a = 30.775(7) A, c = 14.528(7) A, V = 13 759(8) A(3), and Z = 8. The trianionic citrate ligands supply both carboxylate and alkoxide coordination and stabilize the structure using simultaneous chelating and bridging modes of attachment. The compound is a neutral species, exhibiting titanium in three contrasting environments. Laser Raman microscopy and (13)C CPMAS solid-state NMR data were consistent with those of the X-ray crystal structure. When exposed to air, the crystals rapidly lost water and became a powder. The dehydrated powder was noncrystalline to X-rays and insoluble, but (13)C NMR results demonstrated retention of the carboxylate linkages. 相似文献
127.
Heinrich Winter 《Mathematische Semesterberichte》2004,50(2):191-235
Dieser Beitrag hat seinen Ursprung in Veranstaltungen zur Heuristik im Rahmen meiner Tätigkeit in der fachdidaktischen Ausbildung von Gymnasiallehrern an der hiesigen RWTH. Mehr und mehr habe ich dabei die Überzeugung gewonnen, dass es notwendig ist, Lehramtskandidaten historische, heuristische und pädagogische Aspekte wichtiger mathematischer Inhalte erfahren zu lassen, die innerhalb der fachlichen Ausbildung nicht oder nicht genügend Berücksichtigung finden können und die aber im Hinblick auf den späteren Beruf wesentlich sind. Es wird hiermit weniger für eine Behandlung des Zwei-Quadrate-Satzes in der Schule - wenngleich sehr erwünscht - plädiert, wohl aber könnte dieses Thema Bestandteil eines fachdidaktischen Seminars oder Proseminars sein. Die Einschränkung im obigen Zitat von Hardy war natürlich eine zusätzliche didaktische Herausforderung. Den Gutachtern danke ich für ihre Ermutigung sowie für zahlreiche Verbesserungsvorschläge und Hinweise auf Unklarheiten und Fehler. Ebenso danke ich Herrn Artmann sehr, der eine frühere Fassung gelesen und konstruktiv kritisiert hat.Einige Grafiken wurden mit der dynamischen Mathematiksoftware GEONExT erzeugt. GEONExT ist unter der Adresse http: //geonext.de frei erhältlich. 相似文献
128.
We analyze the decomposition rank (a notion of covering dimensionfor nuclear C*-algebras introduced by E. Kirchberg and the author)of subhomogeneous C*-algebras. In particular, we show that asubhomogeneous C*-algebra has decomposition rank n if and onlyif it is recursive subhomogeneous of topological dimension n,and that n is determined by the primitive ideal space. As an application, we use recent results of Q. Lin and N. C.Phillips to show the following. Let A be the crossed productC*-algebra coming from a compact smooth manifold and a minimaldiffeomorphism. Then the decomposition rank of A is dominatedby the covering dimension of the underlying manifold. 2000 MathematicsSubject Classification 46L85, 46L35. 相似文献
129.
Juncheng?WeiEmail author Matthias?Winter 《Calculus of Variations and Partial Differential Equations》2004,20(4):403-430
We consider the following singularly perturbed semilinear elliptic problem:
where
is a bounded domain in R
N
with smooth boundary
,
is a small constant and f is some superlinear but subcritical nonlinearity. Associated with (I) is the energy functional
defined by
where
. Ni and Takagi ([29, 30]) proved that for a single boundary spike solution
, the following asymptotic expansion holds:
where c
1 > 0 is a generic constant,
is the unique local maximum point of
and
is the boundary mean curvature function at
. In this paper, we obtain a higher-order expansion of
where c
2, c
3 are generic constants and
is the scalar curvature at
. In particular c
3 > 0. Some applications of this expansion are given.Received: 14 January 2003, Accepted: 28 July 2003, Published online: 15 October 2003Mathematics Subject Classification (2000):
Primary 35B40, 35B45; Secondary 35J25 相似文献
130.
Phenanthrenequinone undergoes highly efficient proton transfer processes in the presence of a thiourea-functionalised polystyrene copolymer whereas interactions with a similar benzyl-thiourea monomer show strong redox modulation of the quinone without proton transfer. 相似文献