全文获取类型
收费全文 | 105168篇 |
免费 | 1013篇 |
国内免费 | 604篇 |
专业分类
化学 | 42890篇 |
晶体学 | 908篇 |
力学 | 7284篇 |
综合类 | 1篇 |
数学 | 36968篇 |
物理学 | 18734篇 |
出版年
2022年 | 183篇 |
2021年 | 276篇 |
2020年 | 347篇 |
2019年 | 314篇 |
2018年 | 10617篇 |
2017年 | 10458篇 |
2016年 | 6602篇 |
2015年 | 1440篇 |
2014年 | 936篇 |
2013年 | 1698篇 |
2012年 | 5125篇 |
2011年 | 12061篇 |
2010年 | 6514篇 |
2009年 | 6772篇 |
2008年 | 7930篇 |
2007年 | 10072篇 |
2006年 | 1749篇 |
2005年 | 2667篇 |
2004年 | 2819篇 |
2003年 | 3026篇 |
2002年 | 2028篇 |
2001年 | 691篇 |
2000年 | 688篇 |
1999年 | 544篇 |
1998年 | 572篇 |
1997年 | 574篇 |
1996年 | 589篇 |
1995年 | 472篇 |
1994年 | 462篇 |
1993年 | 435篇 |
1992年 | 369篇 |
1991年 | 382篇 |
1990年 | 323篇 |
1989年 | 337篇 |
1988年 | 317篇 |
1987年 | 274篇 |
1986年 | 300篇 |
1985年 | 404篇 |
1984年 | 410篇 |
1983年 | 346篇 |
1982年 | 383篇 |
1981年 | 349篇 |
1980年 | 383篇 |
1979年 | 313篇 |
1978年 | 332篇 |
1977年 | 297篇 |
1976年 | 239篇 |
1975年 | 205篇 |
1974年 | 205篇 |
1973年 | 188篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In two papers Franz et al. proved bounds for the free energy of diluted random constraints satisfaction problems, for a Poisson degree distribution (Franz and Leone in J Stat Phys 111(3–4):535–564, 2003) and a general distribution (Franz et al. in J Phys A 36(43), 10967, 2003). Panchenko and Talagrand (Probab Theo Relat Fields 130(3):319–336, 2004) simplified the proof and generalized the result of Franz and Leone (J Stat Phys 111(3–4):535–564, 2003) for the Poisson case. We provide a new proof for the general degree distribution case and as a corollary, we obtain new bounds for the size of the largest independent set (also known as hard core model) in a large random regular graph. Our proof uses a combinatorial interpolation based on biased random walks (Salez in Combin Probab Comput 25(03):436–447, 2016) and allows to bypass the arguments in Franz et al. (J Phys A 36(43):10967, 2003) based on the study of the Sherrington–Kirkpatrick (SK) model. 相似文献
992.
Philippe Laurençot 《Journal of statistical physics》2018,171(3):484-492
Uniqueness of mass-conserving self-similar solutions to Smoluchowski’s coagulation equation is shown when the coagulation kernel K is given by \(K(x,x_*)=2(x x_*)^{-\alpha }\), \((x,x_*)\in (0,\infty )^2\), for some \(\alpha >0\). 相似文献
993.
Anton Alekseev Florian Naef Xiaomeng Xu Chenchang Zhu 《Letters in Mathematical Physics》2018,108(3):757-778
Descent equations play an important role in the theory of characteristic classes and find applications in theoretical physics, e.g., in the Chern–Simons field theory and in the theory of anomalies. The second Chern class (the first Pontrjagin class) is defined as \(p= \langle F, F\rangle \) where F is the curvature 2-form and \(\langle \cdot , \cdot \rangle \) is an invariant scalar product on the corresponding Lie algebra \(\mathfrak g\). The descent for p gives rise to an element \(\omega =\omega _3+\omega _2+\omega _1+\omega _0\) of mixed degree. The 3-form part \(\omega _3\) is the Chern–Simons form. The 2-form part \(\omega _2\) is known as the Wess–Zumino action in physics. The 1-form component \(\omega _1\) is related to the canonical central extension of the loop group LG. In this paper, we give a new interpretation of the low degree components \(\omega _1\) and \(\omega _0\). Our main tool is the universal differential calculus on free Lie algebras due to Kontsevich. We establish a correspondence between solutions of the first Kashiwara–Vergne equation in Lie theory and universal solutions of the descent equation for the second Chern class p. In more detail, we define a 1-cocycle C which maps automorphisms of the free Lie algebra to one forms. A solution of the Kashiwara–Vergne equation F is mapped to \(\omega _1=C(F)\). Furthermore, the component \(\omega _0\) is related to the associator \(\Phi \) corresponding to F. It is surprising that while F and \(\Phi \) satisfy the highly nonlinear twist and pentagon equations, the elements \(\omega _1\) and \(\omega _0\) solve the linear descent equation. 相似文献
994.
We classify and explicitly describe homomorphisms of Verma modules for conformal Galilei algebras \({\mathfrak {cga}}_\ell (d,\mathbb {C})\) with \(d=1\) for any integer value \(\ell \in {\mathbb {N}}\). The homomorphisms are uniquely determined by singular vectors as solutions of certain differential operators of flag type and identified with specific polynomials arising as coefficients in the expansion of a parametric family of symmetric polynomials into power sum symmetric polynomials. 相似文献
995.
The parafermionic cosets \(\mathsf {C}_{k} = {\text {Com}} ( \mathsf {H} , \mathsf {L}_{k}(\mathfrak {sl}_{2}) )\) are studied for negative admissible levels k, as are certain infinite-order simple current extensions \(\mathsf {B}_{k}\) of \(\mathsf {C}_{k}\). Under the assumption that the tensor theory considerations of Huang, Lepowsky and Zhang apply to \(\mathsf {C}_{k}\), irreducible \(\mathsf {C}_{k}\)- and \(\mathsf {B}_{k}\)-modules are obtained from those of \(\mathsf {L}_{k}(\mathfrak {sl}_{2})\). Assuming the validity of a certain Verlinde-type formula likewise gives the Grothendieck fusion rules of these irreducible modules. Notably, there are only finitely many irreducible \(\mathsf {B}_{k}\)-modules. The irreducible \(\mathsf {C}_{k}\)- and \(\mathsf {B}_{k}\)-characters are computed and the latter are shown, when supplemented by pseudotraces, to carry a finite-dimensional representation of the modular group. The natural conjecture then is that the \(\mathsf {B}_{k}\) are \(C_2\)-cofinite vertex operator algebras. 相似文献
996.
Ali Asghar Mohammadi Salman Taheri Arman Amini Reza Ahdenov 《Molecular diversity》2018,22(4):999-1006
Triamide derivatives have been synthesized in good yields in a novel, one-pot, five-component, and efficient process by the reaction of Z-oxazolone, water, primary amines, aldehydes, isocyanides, in the presence of catalytic amount of KAl(SO4)2·12H2O (alum) as a non-toxic, reusable, inexpensive, and easily available reagent via Ugi reaction in aqueous solution. 相似文献
997.
Gal Ehrlich Moshe Zohar Mark Auslender Roy Avrahamy Shlomo Hava 《Optical and Quantum Electronics》2018,50(1):48
We study a triangular arrangement of two flat mirrors and a grating mirror for coupling a \(-1{\mathrm{st}}\) diffracted order light beam into a traveling-wave intra-cavity light recirculation and out-of-cavity output, combining the \(0\,{\mathrm{th}}\) and the repeatedly diffracted secondary \(+1{\mathrm{st}}\) order beams. The thus designed and then optimized grating Fabry-Perot ring cavity demonstrates high output contrast and detection resolution for wavelength, cavity length and incidence angle. 相似文献
998.
In this paper, an asymmetric cryptosystem has been proposed to enhance the security of DRPE. The traditional DRPE scheme is thus tweaked by using fractional Fourier transform (FrFT), a class of structured phase masks called as deterministic phase masks (DMKs) and deploying singular value decomposition (SVD). In specific, we propose to organise the encryption procedure by using two DMKs and FrFT, additionally deploying SVD. On the decryption front, the input image is recovered by utilising the inverse singular value decomposition (ISVD) and an angular portion of the deterministic phase masks. The use of FrFT for encryption and decryption would enhance the robustness of DRPE scheme. Deployment of SVD on our asymmetric cryptosystem provides three components for cipher image is yet another added feature that hardens the security of DRPE scheme. DMKs are formed by the deviation from conventional rectangular function and limited range values which delivers key components with reduced size, better performance and lower complexity. The capability study of defined method, includes analysis on SVD, histogram and correlation coefficient. Our system is subject to an occlusion attack and noise attack to evaluate its performance and reliability. Computational analysis outputs and security investigation are offered in aspect to determine the security potential of proposed system. Comparative results are shown for values of mean-square-error and peak-signal-to-noise ratio of DRPE schemes. 相似文献
999.
Fernando Pigeard de Almeida Prado Gunter M. Schütz 《Journal of statistical physics》2011,142(5):984-999
We consider a kinetic Ising model which represents a generic agent-based model for various types of socio-economic systems.
We study the case of a finite (and not necessarily large) number of agents N as well as the asymptotic case when the number of agents tends to infinity. The main ingredient are individual decision thresholds
which are either fixed over time (corresponding to quenched disorder in the Ising model, leading to nonlinear deterministic
dynamics which are generically non-ergodic) or which may change randomly over time (corresponding to annealed disorder, leading
to ergodic dynamics). We address the question how increasing the strength of annealed disorder relative to quenched disorder
drives the system from non-ergodic behavior to ergodicity. Mathematically rigorous analysis provides an explicit and detailed
picture for arbitrary realizations of the quenched initial thresholds, revealing an intriguing “jumpy” transition from non-ergodicity
with many absorbing sets to ergodicity. For large N we find a critical strength of annealed randomness, above which the system becomes asymptotically ergodic. Our theoretical
results suggests how to drive a system from an undesired socio-economic equilibrium (e.g. high level of corruption) to a desirable
one (low level of corruption). 相似文献
1000.
Bipin Singh Koranga Rajesh Pandey 《International Journal of Theoretical Physics》2011,50(5):1468-1473
Neutrino mixing lead to a non zero contribution to the dark energy of the universe. We assume that the neutrino masses and
mixing arise through physics at a scale intermediate between Planck Scale and the electroweak scale. The mechanism of neutrino
mixing is a possible candidate to contribute the cosmological dark energy. Quantum gravitational (Planck scale) effects lead
to an effective SU(2)
L
×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields, which gives rise to additional terms in neutrino
mass matrix. There additional term can be considered to be perturbation of the GUT scale bi-maximal neutrino mass matrix.
We assume that the gravitational interaction is flavor. In this paper, we discuss the three flavor neutrino mixing and cosmological
dark energy contributes due to Planck scale effects. 相似文献