首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8832篇
  免费   1928篇
  国内免费   958篇
化学   7068篇
晶体学   35篇
力学   842篇
综合类   49篇
数学   336篇
物理学   3388篇
  2024年   9篇
  2023年   99篇
  2022年   184篇
  2021年   223篇
  2020年   326篇
  2019年   345篇
  2018年   380篇
  2017年   331篇
  2016年   386篇
  2015年   486篇
  2014年   671篇
  2013年   837篇
  2012年   656篇
  2011年   712篇
  2010年   563篇
  2009年   646篇
  2008年   615篇
  2007年   550篇
  2006年   539篇
  2005年   489篇
  2004年   450篇
  2003年   420篇
  2002年   266篇
  2001年   192篇
  2000年   193篇
  1999年   155篇
  1998年   146篇
  1997年   136篇
  1996年   101篇
  1995年   123篇
  1994年   87篇
  1993年   71篇
  1992年   56篇
  1991年   18篇
  1990年   43篇
  1989年   28篇
  1988年   23篇
  1987年   27篇
  1986年   17篇
  1985年   15篇
  1984年   21篇
  1983年   5篇
  1982年   15篇
  1981年   8篇
  1980年   6篇
  1979年   12篇
  1977年   7篇
  1976年   5篇
  1971年   4篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
963.
We investigate whether, and to what extent, the physical phenomenon of long-lifetime resonant electromagnetic states with localized slowly-evanescent field patterns can be used to transfer energy efficiently over non-negligible distances, even in the presence of extraneous environmental objects. Via detailed theoretical and numerical analyses of typical real-world model-situations and realistic material parameters, we establish that such a non-radiative scheme can lead to “strong coupling” between two medium-range distant such states and thus could indeed be practical for efficient medium-range wireless energy transfer.  相似文献   
964.
A series of soluble conjugated ligands TT , FT , PT , and NT that contained terpyridyl terminal units were synthesized by Heck coupling. These ligands absorbed at 341–434 nm and emitted blue–green light, with maximum at 440–522 nm and photoluminescence quantum yields of 0.15–0.71 in solution. The double‐layer electroluminescent devices with the configuration of ITO/PEDOT/ligand FT , PT , or NT /Ca/Al exhibited a brightness of 43–63 cd/m2. These ligands were further reacted with zinc(II) and ruthenium(II) ions and subsequent anion exchange to afford linear and supramolecular complexes. The photophysics of these complexes were investigated. A significant redshift of the emission maximum of the Zn complexes relative to the corresponding ligands was observed. The Ru complexes were used to fabricate photovoltaic devices with the structure ITO/PEDOT/Ru complex/P3HT:PCBM (1:1 wt/wt)/Ca/Al. The power conversion efficiency of these polymer–fullerene bulk heterojunction photovoltaic devices was up to 0.71%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7702–7712, 2008  相似文献   
965.
Vorobjev  Yu. M. 《Mathematical Notes》2001,70(3-4):486-493
It is shown that, up to a diffeomorphism, the linearized Poisson structure does not depend on the choice of the transversal near the zero section.  相似文献   
966.
Numerical simulation results derived from a Schrödinger–Poisson tool applied to scaled double-gate (DG) MOSFETs, supplemented by analytical characterizations of the pertinent physics, are presented to give insight concerning the near-ideal features of DG devices and to explain how the low-voltage drive current of the asymmetrical DG MOSFET, having only one predominant channel, can be comparable to, and even higher than, that of the symmetrical-gate counterpart designed to have the same off-state current.  相似文献   
967.
Efficient B3LYP and BHandH density functionals were used to estimate methanol's nuclear magnetic isotropic shieldings and spin–spin coupling constants in the basis set limit. Polarization‐consistent pcS‐n and pcJ‐n (n = 0, 1, 2, 3 and 4), and segmented contracted XZP, where X = D, T, Q and 5, basis sets were used and the results fitted with simple mathematical formulas. The performance of the methods was assessed from comparison with experiment and higher level calculations. 1J(CH) and 3J(HH) values were determined from very diluted solutions in deuterochloroform and compared with theoretical predictions. The agreement between complete basis set (CBS) density functional theory (DFT) predicted isotropic shieldings and spin–spin values and experiment was good. The BHandH/pcS‐n methanol shieldings obtained using structures optimized at the same level of theory are approaching the accuracy of the advanced coupled‐cluster‐singles‐doubles‐approximate triples (CCSD(T)) calculations. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
968.
Non-minimal interactions in the pp-wave Einstein–Yang–Mills–Higgs (EYMH) model are shown to give rise to color cross-effects analogous to the magneto-electricity in the Maxwell theory. In order to illustrate the significance of these color cross-effects, we reconstruct the effective (associated, color, and color-acoustic) metrics for the pp-wave non-minimal seven-parameter EYMH model with parallel gauge and scalar background fields. Then these metrics are used as hints for obtaining explicit exact solutions of the non-minimally extended Yang–Mills and Higgs equations for the test fields propagating in the vacuum interacting with curvature. The influence of the non-minimal coupling on the test particle motion is interpreted in terms of the so-called trapped surfaces, introduced in the Analog Gravity theory.  相似文献   
969.
970.
王效敬 《光学学报》1990,10(9):19-825
用光线矩阵方法推导了光纤-自聚焦棒-反射器在共轴耦合情况下的后向耦合系数;分析了它与耦合系统结构参数之间的关系.用计算机模拟画出了反射器为平面镜的系统的后向耦合系数和后向耦合损耗的曲线分布,计算曲线与实验结果大致符合.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号