全文获取类型
收费全文 | 47511篇 |
免费 | 4137篇 |
国内免费 | 5191篇 |
专业分类
化学 | 30926篇 |
晶体学 | 330篇 |
力学 | 1335篇 |
综合类 | 728篇 |
数学 | 7724篇 |
物理学 | 15796篇 |
出版年
2023年 | 642篇 |
2022年 | 768篇 |
2021年 | 1629篇 |
2020年 | 1242篇 |
2019年 | 1373篇 |
2018年 | 1005篇 |
2017年 | 1096篇 |
2016年 | 1397篇 |
2015年 | 1444篇 |
2014年 | 1781篇 |
2013年 | 3326篇 |
2012年 | 2323篇 |
2011年 | 2557篇 |
2010年 | 2279篇 |
2009年 | 3023篇 |
2008年 | 3176篇 |
2007年 | 3347篇 |
2006年 | 2811篇 |
2005年 | 1999篇 |
2004年 | 1895篇 |
2003年 | 1797篇 |
2002年 | 1574篇 |
2001年 | 1421篇 |
2000年 | 1183篇 |
1999年 | 950篇 |
1998年 | 922篇 |
1997年 | 716篇 |
1996年 | 729篇 |
1995年 | 640篇 |
1994年 | 621篇 |
1993年 | 628篇 |
1992年 | 621篇 |
1991年 | 439篇 |
1990年 | 359篇 |
1989年 | 290篇 |
1988年 | 320篇 |
1987年 | 268篇 |
1986年 | 254篇 |
1985年 | 377篇 |
1984年 | 260篇 |
1983年 | 161篇 |
1982年 | 338篇 |
1981年 | 504篇 |
1980年 | 453篇 |
1979年 | 496篇 |
1978年 | 390篇 |
1977年 | 292篇 |
1976年 | 250篇 |
1974年 | 85篇 |
1973年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
51.
《Physics letters. A》2020,384(7):126152
Derived from quantum waves immersed in an Abelian gauge potential, the quasiperiodic Aubry-André-Harper (AAH) model is a simple yet powerful Hamiltonian to study the Anderson localization of ultracold atoms. Here, we investigate the localization properties of ultracold atoms in quasiperiodic optical lattices subject to a non-Abelian gauge potential, which are depicted by non-Abelian AAH models. We identify that the non-Abelian AAH models can bear the self-duality. We analyze the localization of such non-Abelian self-dual optical lattices, revealing a rich phase diagram driven by the non-Abelian gauge potential involved: a transition from a pure delocalization phase, then to coexistence phases, and finally to a pure localization phase. This is in stark contrast to the Abelian counterpart that does not support the coexistence phases. Our results establish the connection between localization and gauge symmetry, and thus comprise a new insight on the fundamental aspects of localization in quasiperiodic systems, from the perspective of non-Abelian gauge potential. 相似文献
52.
《Physics letters. A》2020,384(27):126674
A nonlinear molecular structural mechanics (MSM) model is proposed in this paper for studying the tensile properties of microtubules (MTs). In the nonlinear MSM models, the interactions between tubulin monomers in MTs are treated as nonlinear axial and torsional springs, whose stiffness coefficients are extracted from all-atom molecular dynamics simulations. The Young's modulus and fracture properties of MTs under tension extracted from the present nonlinear MSM models are found to agree well with the existing simulation and experiment results, which shows the efficiency and accuracy of the proposed nonlinear MSM models. In addition, the nonlinear MSM models are also extended to investigate the tensile properties including Young's modulus and fracture strain of MTs possessing lattice defects. The results obtained from nonlinear MSM models are utilized to develop a predictive equation for quickly predicting the tensile properties of MTs with different lattice defect levels. 相似文献
53.
单摆教学的过程中引入MATLAB数值计算的教学新模式,可以有效地改善大学物理教学的枯燥方式,有助于提高学生对大学物理课中抽象的、复杂的物理现象和规律的理解,也有助于促进对所学数学知识的实际应用.这种新教学模式是深化高等工程教育改革、加快新工科建设、促进创新型工科人才培养的有效手段. 相似文献
54.
基于密度泛函的第一原理赝势平面波方法,计算晶体结构、电子结构和光学性质,研究硫钒铜矿化合物Cu3VS4、Cu3NbS4和Cu3TaS4的电子输运及电致变色特性,探讨作为透明半导体材料应用于太阳能电池和电致变色器件的可能性.电子结构的计算表明这类化合物是间接带隙半导体,其电子能带的导带底和价带顶分别位于布里渊区的X点和R点.价带顶的电子本征态主要来自于Cu原子的d电子轨道,而导带底电子态主要来源于VB族元素原子的d电子轨道.能带结构、电荷布居分析、电子局域化函数和光吸收及反射谱的计算表明这些硫钒铜矿化合物属于极性共价半导体,具有较高的电荷迁移率和优良的电致变色特性,可应用于高效电致变色器件. 相似文献
55.
本文利用红外光解离光谱研究了第三族金属氧化物离子对二氧化碳分子的转化机制. 研究表明,对于[ScO(CO2)n]+体系,在n≤4时,形成了溶剂化结构;在n=5时,形成了碳酸盐结构,实现了二氧化碳的转化. 对于[YO(CO2)n]+体系,需要4个二氧化碳分子就可以实现二氧化碳的转化. 而在[YO(CO2)n]+体系中,只发现了溶剂化结构,没有观察到碳酸盐结构. 理论计算表明,[YO(CO2)n]+体系拥有最小的溶剂化结构向碳酸盐结构转化能垒,[LaO(CO2)n]+体系拥有最大的溶剂化结构向碳酸盐结构转化能垒. 本文从分子水平揭示了不同金属氧化物离子对二氧化碳分子转化的影响规律. 相似文献
56.
Pingyu Zhu Qilin Zheng Shichuan Xue Chao Wu Xinyao Yu Yang Wang Yingwen Liu Xiaogang Qiang Junjie Wu Ping Xu 《Frontiers of Physics》2020,15(6):61501
One of the most important multipartite entangled states, Greenberger–Horne–Zeilinger state (GHZ), serves as a fundamental resource for quantum foundation test, quantum communication and quantum computation. To increase the number of entangled particles, significant experimental efforts should been invested due to the complexity of optical setup and the difficulty in maintaining the coherence condition for high-fidelity GHZ state. Here, we propose an ultra-integrated scalable on-chip GHZ state generation scheme based on frequency combs. By designing several microrings pumped by different lasers, multiple partially overlapped quantum frequency combs are generated to supply as the basis for on-chip polarization-encoded GHZ state with each qubit occupying a certain spectral mode. Both even and odd numbers of GHZ states can be engineered with constant small number of integrated components and easily scaled up on the same chip by only adjusting one of the pump wavelengths. In addition, we give the on-chip design of projection measurement for characterizing GHZ states and show the reconfigurability of the state. Our proposal is rather simple and feasible within the existing fabrication technologies and we believe it will boost the development of multiphoton technologies. 相似文献
57.
58.
《Comptes Rendus Chimie》2015,18(6):599-606
Pentose-derived surfactants were easily synthesized and fully characterized through classical analytical methods. The interfacial behaviors revealed the importance of both the length of the hydrophobic chain and the nature of the anomeric form. Finally, the spatial conformation of four xylosides was obtained by molecular modeling with software Hyperchem® 4 using the semi-empirical method PM3, which demonstrated the role of hydrophobic interactions in the stability of the compounds. 相似文献
59.
Experimental Evidence of Chemical Components in the Bonding of Helium and Neon with Neutral Molecules 下载免费PDF全文
60.
The bond ionicity in seventy two ANB8−N compounds is investigated according to the recently introduced first-principles ionicity scale, based on the centers of the maximally localized Wannier functions, which has several interesting features. The obtained bond ionicities (qi) are found to exhibit the expected trends, according to electronegativity arguments. In particular, the bond ionicity in the alkaline-earth oxides increases by going from MgO to BaO. A strong crystal structure dependence of qi is observed. A critical value of qi (of 0.91) that separates between the tetrahedrally and octahedrally coordinated systems is inferred directly from the calculated values of qi. The volume dependence of qi is investigated for all the considered compounds and found to reduce by volume decrease for most of the studied systems. The adopted ionicity scale is established as a very strong competitor to the most widely accepted Phillips and Pauling ionicity measures. 相似文献