全文获取类型
收费全文 | 6397篇 |
免费 | 256篇 |
国内免费 | 56篇 |
专业分类
化学 | 3769篇 |
晶体学 | 63篇 |
力学 | 251篇 |
综合类 | 2篇 |
数学 | 1454篇 |
物理学 | 1170篇 |
出版年
2023年 | 54篇 |
2022年 | 161篇 |
2021年 | 170篇 |
2020年 | 173篇 |
2019年 | 201篇 |
2018年 | 186篇 |
2017年 | 173篇 |
2016年 | 274篇 |
2015年 | 204篇 |
2014年 | 282篇 |
2013年 | 449篇 |
2012年 | 435篇 |
2011年 | 475篇 |
2010年 | 256篇 |
2009年 | 291篇 |
2008年 | 341篇 |
2007年 | 287篇 |
2006年 | 219篇 |
2005年 | 207篇 |
2004年 | 204篇 |
2003年 | 167篇 |
2002年 | 153篇 |
2001年 | 96篇 |
2000年 | 93篇 |
1999年 | 53篇 |
1998年 | 41篇 |
1997年 | 56篇 |
1996年 | 72篇 |
1995年 | 62篇 |
1994年 | 49篇 |
1993年 | 53篇 |
1992年 | 45篇 |
1991年 | 46篇 |
1990年 | 44篇 |
1989年 | 28篇 |
1988年 | 38篇 |
1987年 | 45篇 |
1986年 | 44篇 |
1985年 | 39篇 |
1984年 | 49篇 |
1983年 | 29篇 |
1982年 | 44篇 |
1981年 | 37篇 |
1980年 | 32篇 |
1979年 | 40篇 |
1978年 | 36篇 |
1977年 | 33篇 |
1976年 | 35篇 |
1975年 | 24篇 |
1974年 | 26篇 |
排序方式: 共有6709条查询结果,搜索用时 15 毫秒
991.
Quan M. Nguyen 《Optics Communications》2010,283(18):3500-3511
We study the deterministic effects of inter-pulse Raman-induced crosstalk in amplified wavelength division multiplexing (WDM) optical fiber transmission lines. We show that the dynamics of pulse amplitudes in an N-channel transmission system is described by an N-dimensional predator-prey model. We find the equilibrium states with non-zero amplitudes and prove their stability by obtaining the Lyapunov function. The stability is independent of the exact details of the approximation for the Raman gain curve. Furthermore, we investigate the impact of cross phase modulation and Raman self and cross frequency shifts on the dynamics and establish the stability of the equilibrium state with respect to these perturbations. Our results provide a quantitative explanation for the robustness of differential-phase-shift-keyed WDM transmission against Raman crosstalk effects. 相似文献
992.
Aguilar-Arevalo AA Anderson CE Brice SJ Brown BC Bugel L Conrad JM Dharmapalan R Djurcic Z Fleming BT Ford R Garcia FG Garvey GT Mirabal J Grange J Green JA Imlay R Johnson RA Karagiorgi G Katori T Kobilarcik T Linden SK Louis WC Mahn KB Marsh W Mauger C Metcalf W Mills GB Moore CD Mousseau J Nelson RH Nguyen V Nienaber P Nowak JA Osmanov B Pavlovic Z Perevalov D Polly CC Ray H Roe BP Russell AD Schirato R Shaevitz MH Sorel M Spitz J Stancu I Stefanski RJ Tayloe R Tzanov M Van de Water RG 《Physical review letters》2010,105(18):181801
The MiniBooNE experiment at Fermilab reports results from a search for ˉν_{μ}→ˉν_{e} oscillations, using a data sample corresponding to 5.66×102? protons on target. An excess of 20.9±14.0 events is observed in the energy range 475相似文献
993.
The nonlinear evolution of resonantly driven systems, such as suprathermal particle driven modes in magnetically confined plasmas, is shown to strongly depend on the existence and nature of an underlying damping mechanism. When background resonant damping is present, subcritical states can take place. In particular, purely nonlinear steady-state regimes are found, whose destabilization threshold and saturation levels are calculated and validated using numerical simulations. This nonlinear behavior can be of relevance for acoustic modes in magnetically confined plasmas. 相似文献
994.
Nguyen TH Mahieu G Berthe M Grandidier B Delerue C Stiévenard D Ebert P 《Physical review letters》2010,105(22):226404
Determination of the Coulomb energy of single point defects is essential because changing their charge state critically affects the properties of materials. Based on a novel approach that allows us to simultaneously identify a point defect and to monitor the occupation probability of its electronic state, we unambiguously measure the charging energy of a single Si dangling bond with tunneling spectroscopy. Comparing the experimental result with tight-binding calculations highlights the importance of the particular surrounding of the localized state on the effective charging energy. 相似文献
995.
996.
Samir Adly Abderrahim Hantoute Bao Tran Nguyen 《Journal of Mathematical Analysis and Applications》2018,457(2):1017-1037
We give different conditions for the invariance of closed sets with respect to differential inclusions governed by a maximal monotone operator defined on Hilbert spaces, which is subject to a Lipschitz continuous perturbation depending on the state. These sets are not necessarily weakly closed as in [3], [4], while the invariance criteria are still written by using only the data of the system. So, no need to the explicit knowledge of neither the solution of this differential inclusion, nor the semi-group generated by the maximal monotone operator. These invariant/viability results are next applied to derive explicit criteria for a-Lyapunov pairs of lower semi-continuous (not necessarily weakly-lsc) functions associated to these differential inclusions. The lack of differentiability of the candidate Lyapunov functions and the consideration of general invariant sets (possibly not convex or smooth) are carried out by using techniques from nonsmooth analysis. 相似文献
997.
Hop D. Nguyen 《Journal of Pure and Applied Algebra》2018,222(8):2342-2358
Absolutely Koszul algebras are a class of rings over which any finite graded module has a rational Poincaré series. We provide a criterion to detect non-absolutely Koszul rings. Combining the criterion with Macaulay2 computations, we identify large families of Veronese subrings and Segre products of polynomial rings which are not absolutely Koszul. In particular, we classify completely the absolutely Koszul algebras among Segre products of polynomial rings, when the base field has characteristic 0. 相似文献
998.
Pham Hung Quy 《Journal of Pure and Applied Algebra》2018,222(5):1126-1138
Let be an equidimensional excellent local ring of characteristic . The aim of this paper is to show that does not depend on the choice of parameter ideal provided R is an F-injective local ring that is F-rational on the punctured spectrum. 相似文献
999.
It is proved that a semiperfect module is lifting if and only if it has a projective cover preserving direct summands. Three corollaries are obtained: (1) every cyclic module over a ring R is lifting if and only if every cyclic R-module has a projective cover preserving direct summands; (2) a ring R is artinian serial with Jacobson radical square-zero if and only if every (2-generated) R-module has a projective cover preserving direct summands; (3) a ring R is a right (semi-)perfect ring if and only if (cyclic) lifting R-module has a projective cover preserving direct summands, if and only if every (cyclic) R-module having a projective cover preserving direct summands is lifting. It is also proved that every cyclic module over a ring R is ⊕-supplemented if and only if every cyclic R-module is a direct sum of local modules. Consequently, a ring R is artinian serial if and only if every left and right R-module is a direct sum of local modules. 相似文献
1000.
Numerical Algorithms - In this paper, we introduce a new algorithm which combines the inertial projection and contraction method and the viscosity method for solving monotone variational inequality... 相似文献