全文获取类型
收费全文 | 27217篇 |
免费 | 5343篇 |
国内免费 | 3288篇 |
专业分类
化学 | 8930篇 |
晶体学 | 164篇 |
力学 | 612篇 |
综合类 | 189篇 |
数学 | 1951篇 |
物理学 | 16084篇 |
综合类 | 7918篇 |
出版年
2024年 | 77篇 |
2023年 | 318篇 |
2022年 | 721篇 |
2021年 | 835篇 |
2020年 | 848篇 |
2019年 | 691篇 |
2018年 | 674篇 |
2017年 | 752篇 |
2016年 | 952篇 |
2015年 | 1010篇 |
2014年 | 1426篇 |
2013年 | 1847篇 |
2012年 | 1619篇 |
2011年 | 1864篇 |
2010年 | 1505篇 |
2009年 | 1650篇 |
2008年 | 1902篇 |
2007年 | 2056篇 |
2006年 | 1878篇 |
2005年 | 1738篇 |
2004年 | 1385篇 |
2003年 | 1337篇 |
2002年 | 1332篇 |
2001年 | 1035篇 |
2000年 | 1047篇 |
1999年 | 862篇 |
1998年 | 723篇 |
1997年 | 613篇 |
1996年 | 503篇 |
1995年 | 418篇 |
1994年 | 374篇 |
1993年 | 324篇 |
1992年 | 279篇 |
1991年 | 227篇 |
1990年 | 204篇 |
1989年 | 206篇 |
1988年 | 147篇 |
1987年 | 103篇 |
1986年 | 61篇 |
1985年 | 70篇 |
1984年 | 44篇 |
1983年 | 22篇 |
1982年 | 38篇 |
1981年 | 23篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
We analyze the emission spectrum of a single organic quantum dot coupled to a microcavity in the strong coupling regime. We take into account non-linearities arising from both exciton–exciton interactions and the Pauli exclusion principle. We apply the recently developed Pade approximation for regular truncation of Green functions to calculate the emission spectrum. We show that as the number of excitations in the quantum dot increases the Rabi doublet evolves into a more complicated triplet structure. 相似文献
992.
《Journal of computational chemistry》2017,38(29):2538-2552
Chemical research is assisted by the creation of visual representations that map concepts (such as atoms and bonds) to 3D objects. These concepts are rooted in chemical theory that predates routine solution of the Schrödinger equation for systems of interesting size. The method of Quantum Chemical Topology (QCT) provides an alternative, parameter‐free means to understand chemical phenomena directly from quantum mechanical principles. Representation of the topological elements of QCT has lagged behind the best tools available. Here, we describe a general abstraction (and corresponding file format) that permits the definition of mappings between topological objects and their 3D representations. Possible mappings are discussed and a canonical example is suggested, which has been implemented as a Python “Add‐On” named Rhorix for the state‐of‐the‐art 3D modeling program Blender. This allows chemists to use modern drawing tools and artists to access QCT data in a familiar context. A number of examples are discussed. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. 相似文献
993.
This paper presents the performance analysis of a two-way relay system with nodes-mobility (NM) and channel estimation errors (CEE) under time-varying Rayleigh fading. Herein, analog network coding protocol is employed at the relay node. All the participating nodes are half-duplex and equipped with single-antenna devices. Specifically, we utilize first-order Markovian model to characterize the impact of NM in the channel. Along with the NM, we also consider that the CEE may exist in practical scenarios, where nodes require to estimate the channel state information. By incorporating these factors, we first derive the instantaneous end-to-end (e2e) signal-to-noise ratios (SNRs) at two source nodes. Then, we obtain the exact closed-form expressions for distribution and density functions of the two e2e SNRs. After that, we derive the accurate expressions of various performance metrics, viz., sum-bit error rate, overall outage probability, and ergodic sum-rate. Further, to attain more insights into the considered system, we deduce the asymptotic behavior of these performance metrics. Finally, numerical and Monte-Carlo simulation results are provided to validate our theoretical analysis and to illustrate the impact of NM and CEE on the performance measures of the considered system. 相似文献
994.
Ulf-G.Meiner 《中国物理C(英文版)》2010,34(9)
Isospin violation is driven through the light quark mass difference and electromagnetic effects. I review recent progress in extracting the light quark mass difference and tests of the chiral dynamics of Quantum Chromodynamics in various reactions involving light as well as heavy quarks. 相似文献
995.
996.
997.
I. Babushkin 《Physics letters. A》2010,374(6):896-900
We study deviation from the Poissonian statistics of the frequency spacing distribution, appearing due to coupling of polarizational and transverse degrees of freedom in a perfectly square vertical cavity surface emitting laser. The deviation can be controlled by strength of the intracavity anisotropy and its alignment to the device boundaries. 相似文献
998.
《化学:亚洲杂志》2017,12(5):486-496
Aqueous dye‐sensitized solar cells (DSSCs) are attractive due to their sustainability, the use of water as a safe solvent for the redox mediators, and their possible applications in photoelectrochemical water splitting. However, the higher tendency of dye leaching by water and the lower wettability of dye molecules are two major obstacles that need to be tackled for future applications of aqueous DSSCs. Sensitizers designed for aqueous DSSCs are discussed based on their functions, such as modification of the molecular skeleton and the anchoring group for better stability against dye leaching by water, and the incorporation of hydrophilic entities into the dye molecule or the addition of a surfactant to the system to increase the wettability of the dye for more facile dye regeneration. Surface treatment of the photoanode to deter dye leaching or improve the wettability of the dye molecule is also discussed. Redox mediators designed for aqueous DSSCs are also discussed. The review also includes quantum‐dot‐sensitized solar cells, with a focus on improvements in QD loading and suppression of interfacial charge recombination at the photoanode. 相似文献
999.
我国国有商业银行表外业务存在问题及解决对策 总被引:1,自引:0,他引:1
该文通过阐述我国国有商业银行表外业务发展中的情况和特点,根据其出现的品种单一、业务量少、区域发展不均衡和管理不规范等问题,相应地提出了加快金融创新、提高对其业务重要性的认识和业务营销水平、加强银行间区域合作和完善相关规章制度建设等合理的对策,以期能对我国金融业的发展提供些许有益的参考。 相似文献
1000.
使用SAC/SAC-CI方法,利用D95++**、6-311++g**以及cc-PVTZ等基组,对HD分子的基态(X1Σ+g)、第二激发态(B1Σ+u)和第三激发态(C1Πu)的平衡结构和谐振频率进行了优化计算.通过对3个基组的计算结果的比较,得出了cc-PVTZ基组为三个基组中的最优基组的结论;使用cc-PVTZ基组,利用SAC的GSUM(Group Sum of Operators)方法对基态(X1Σ+g)、SAC-CI的GSUM方法对激发态(B1Σ+u)和(C1Πu)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的完整势能函数;从得到的势能函数计算了与基态(X1Σ+g)、第二激发态(B1Σ+u)和第三激发态(C1Πu)相对应的光谱常数(Be, αe, ωe 和ωeχe),结果与实验数据基本吻合. 相似文献