全文获取类型
收费全文 | 7755篇 |
免费 | 214篇 |
国内免费 | 52篇 |
专业分类
化学 | 4849篇 |
晶体学 | 23篇 |
力学 | 363篇 |
数学 | 1659篇 |
物理学 | 1127篇 |
出版年
2023年 | 44篇 |
2022年 | 145篇 |
2021年 | 188篇 |
2020年 | 175篇 |
2019年 | 141篇 |
2018年 | 154篇 |
2017年 | 123篇 |
2016年 | 286篇 |
2015年 | 250篇 |
2014年 | 257篇 |
2013年 | 459篇 |
2012年 | 514篇 |
2011年 | 559篇 |
2010年 | 297篇 |
2009年 | 310篇 |
2008年 | 456篇 |
2007年 | 467篇 |
2006年 | 375篇 |
2005年 | 352篇 |
2004年 | 341篇 |
2003年 | 263篇 |
2002年 | 201篇 |
2001年 | 92篇 |
2000年 | 64篇 |
1999年 | 72篇 |
1998年 | 74篇 |
1997年 | 71篇 |
1996年 | 86篇 |
1995年 | 48篇 |
1994年 | 58篇 |
1993年 | 64篇 |
1992年 | 51篇 |
1991年 | 48篇 |
1990年 | 51篇 |
1989年 | 37篇 |
1988年 | 48篇 |
1987年 | 39篇 |
1986年 | 39篇 |
1985年 | 77篇 |
1984年 | 70篇 |
1983年 | 48篇 |
1982年 | 57篇 |
1981年 | 44篇 |
1980年 | 46篇 |
1979年 | 34篇 |
1978年 | 45篇 |
1977年 | 36篇 |
1976年 | 36篇 |
1975年 | 15篇 |
1974年 | 32篇 |
排序方式: 共有8021条查询结果,搜索用时 15 毫秒
21.
Alberto S. Cattaneo 《Communications in Mathematical Physics》1997,189(3):795-828
In the context of the Batalin–Vilkovisky formalism, a new observable for the Abelian BF theory is proposed whose vacuum expectation value is related to the Alexander–Conway polynomial. The three-dimensional case
is analyzed explicitly, and it is proved to be anomaly free. Moreover, at the second order in perturbation theory, a new formula
for the second coefficient of the Alexander–Conway polynomial is obtained. An account on the higher-dimensional generalizations
is also given.
Received: 2 October 1996 / Accepted: 21 March 1997 相似文献
22.
We consider a class of non-linear mixed integer programs with n integer variables and k continuous variables. Solving instances from this class to optimality is an NP-hard problem. We show that for the cases with
k=1 and k=2, every optimal solution is integral. In contrast to this, for every k≥3 there exist instances where every optimal solution takes non-integral values.
Received: August 2001 / Accepted: January 2002?Published online March 27, 2002 相似文献
23.
24.
25.
Pablo Alberca Bjerregaard Alberto Elduque Cndido Martín Gonzlez Francisco Jos Navarro Mrquez 《Journal of Algebra》2002,250(2):397
The well-known Cartan–Jacobson theorem claims that the Lie algebra of derivations of a Cayley algebra is central simple if the characteristic is not 2 or 3. In this paper we have studied these two cases, with the following results: if the characteristic is 2, the theorem is also true, but, if the characteristic is 3, the derivation algebra is not simple. We have also proved that in this last case, there is a unique nonzero proper seven-dimensional ideal, which is a central simple Lie algebra of type A2, and the quotient of the derivation algebra modulo this ideal turns out to be isomorphic, as a Lie algebra, to the ideal itself. The original motivation of this work was a series of computer-aided calculations which proved the simplicity of derivation algebras of Cayley algebras in the case of characteristic not 3. These computations also proved the existence of a unique nonzero proper ideal (which turns out to be seven-dimensional) in the algebra of derivations of split Cayley algebras in characteristic 3. 相似文献
26.
Francesco de Giovanni 《Milan Journal of Mathematics》1991,61(1):257-265
27.
Giovanni Bruno Maria M. Giangregorio April S. Brown Soojeong Choi 《Applied Surface Science》2006,253(1):219-223
GaN is grown on Si-face 4H-SiC(0 0 0 1) substrates using remote plasma-assisted methods including metalorganic chemical vapour deposition (RP-MOCVD) and molecular beam epitaxy (MBE). Real time spectroscopic ellipsometry is used for monitoring all the steps of substrate pre-treatments and the heteroepitaxial growth of GaN on SiC. Our characterization emphasis is on understanding the nucleation mechanism and the GaN growth mode, which depend on the SiC surface preparation. 相似文献
28.
Alberto Giaconia Giuseppe Filardo Onofrio Scialdone Alessandro Galia 《Journal of polymer science. Part A, Polymer chemistry》2006,44(13):4122-4135
A laboratory‐scale continuous reaction system using a stirred tank reactor was assembled in our laboratory to study the dispersion polymerization of vinyl monomers in supercritical carbon dioxide (scCO2). The apparatus was equipped with a suitable downstream separation section to collect solid particles entrained in the effluent stream from the reactor, whose monomer concentration could be measured online with a gas chromatograph. The dispersion polymerization of methyl methacrylate in scCO2 was selected as a model process to be investigated in the apparatus. The experiments were performed at 65 °C and 25 MPa with 2,2′‐azobisisobutyronitrile as the initiator and a reactive polysiloxane macromonomer as a surfactant to investigate the effect of the mean residence time of the reaction mixture on the monomer conversion, polymerization rate, polymer molecular weight, and particle size distribution. The results were compared with those obtained in batch polymerizations carried out under similar operative conditions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4122–4135, 2006 相似文献
29.
Precisely two of the homogeneous spaces that appear as coadjoint orbits of the group of string reparametrizations,
, carry in a natural way the structure of infinite dimensional, holomorphically homogeneous complex analytic Kähler manifolds. These areN=Diff(S
1)/Rot(S
1) andM=Diff(S
1)/Möb(S
1). Note thatN is a holomorphic disc fiber space overM. Now,M can be naturally considered as embedded in the classical universal Teichmüller spaceT(1), simply by noting that a diffeomorphism ofS
1 is a quasisymmetric homeomorphism.T(1) is itself a homomorphically homogeneous complex Banach manifold. We prove in the first part of the paper that the inclusion ofM inT(1) iscomplex analytic.In the latter portion of this paper it is shown that theunique homogeneous Kähler metric carried byM = Diff (S
1/SL(2, ) induces preciselythe Weil-Petersson metric on the Teichmüller space. This is via our identification ofM as a holomorphic submanifold of universal Teichmüller space. Now recall that every Teichmüller spaceT(G) of finite or infinite dimension is contained canonically and holomorphically withinT(1). Our computations allow us also to prove that everyT(G), G any infinite Fuchsian group, projects out ofM transversely. This last assertion is related to the fractal nature ofG-invariant quasicircles, and to Mostow rigidity on the line.Our results thus connect the loop space approach to bosonic string theory with the sum-over-moduli (Polyakov path integral) approach. 相似文献
30.
Alberto Facchini 《Annali di Matematica Pura ed Applicata》1989,155(1):389-399
Sunto Se A è un modulo divisibile su un dominio d'integrità R e Q è il campo delle frazioni di R, sia RA Q il massimo sopraanello di R tale che A possa essere dotato della struttura di RA-modulo. La struttura di RA riflette quella di A. Se A è un modulo divisibile semplice di torsione, cioè è divisibile di torsione e non ha sottomoduli divisibili propri non nulli, RA è analiticamente irriducibile. Se C e D sono due moduli divisibili semplici, diciamo C equivalente a D se RC=RD. Se d-Space (R) è un insieme di rappresentanti delle classi di equivalenza degli R-moduli divisibili semplici, d-Space (R) puó essere dotato di una struttura di spazio di Hausdorff zero-dimensionale; lo spazio topologico d-Space (R) (da noi chiamato lo spazio di divisibilità di R) contiene un sottospazio chiuso omeomorfo alla superficie di Riemann astratta di R dotata della patch topology.
Lavoro eseguito con il contribute del Ministero délia Pubblica Istruzione 相似文献
Lavoro eseguito con il contribute del Ministero délia Pubblica Istruzione 相似文献