全文获取类型
收费全文 | 2688篇 |
免费 | 426篇 |
国内免费 | 197篇 |
专业分类
化学 | 958篇 |
晶体学 | 13篇 |
力学 | 346篇 |
综合类 | 44篇 |
数学 | 450篇 |
物理学 | 1500篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 84篇 |
2021年 | 65篇 |
2020年 | 87篇 |
2019年 | 67篇 |
2018年 | 63篇 |
2017年 | 95篇 |
2016年 | 114篇 |
2015年 | 85篇 |
2014年 | 96篇 |
2013年 | 217篇 |
2012年 | 131篇 |
2011年 | 148篇 |
2010年 | 126篇 |
2009年 | 172篇 |
2008年 | 168篇 |
2007年 | 179篇 |
2006年 | 127篇 |
2005年 | 134篇 |
2004年 | 163篇 |
2003年 | 145篇 |
2002年 | 106篇 |
2001年 | 94篇 |
2000年 | 77篇 |
1999年 | 69篇 |
1998年 | 85篇 |
1997年 | 65篇 |
1996年 | 45篇 |
1995年 | 40篇 |
1994年 | 45篇 |
1993年 | 29篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有3311条查询结果,搜索用时 203 毫秒
991.
Using the Nevanlinna value distribution theory of meromorphic function,we investigate the existence problem of admissible solutions of higher-order algebraic differential equations systems,and obtain a result concerning admissible components of solution. 相似文献
992.
993.
Bei Zhang Mo Ying Li Xu Ming Luo Xiong Biao Wang Tong Wu 《Journal of mass spectrometry : JMS》2020,55(1)
Qixianqingming granules (QXQM) comprise a traditional Chinese medicine (TCM) formula that was developed based on the combination of TCM theory and clinical practice. This formula has been proven to effectively treat asthma. In this study, an analytical procedure using ultraperformance liquid chromatography, coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry, was established for the rapid separation and sensitive identification of the chemical components in QXQM and its metabolites in serum of rats. Seventy‐two compounds were systematically identified in QXQM, including flavonoids, terpenoids, anthraquinones, phenylethanoid glycosides, stilbenes, alkaloids, and organic acids. Thirteen prototype compounds and 29 metabolites were detected in the serum of rats. The results provided fundamental information for further studying the mechanisms and clinical application of QXQM. 相似文献
994.
995.
Nikolai S. Mosyagin Aleksander N. Petrov Anatoly V. Titov Andrei V. Zaitsevskii 《International journal of quantum chemistry》2013,113(20):2277-2281
The potential curve, dissociation energy, equilibrium internuclear distance, and spectroscopic constants for the ground state of the Ca2 molecule are calculated with the help of the generalized relativistic effective core potential method, which allows one to exclude the inner core electrons from the calculations and to take the relativistic effects into account effectively. Extensive generalized correlation basis sets were constructed and used. The scalar relativistic coupled cluster method with corrections for high‐order cluster amplitudes is used for the correlation treatment. The results are analyzed and compared with the experimental data and corresponding all‐electron results. © 2013 Wiley Periodicals, Inc. 相似文献
996.
Guillermo Ramírez Rafael López Ignacio Ema Jaime Fernández Rico 《International journal of quantum chemistry》2013,113(1):52-55
In atomic systems, electron density has a simple finite expansion in spherical harmonics times radial factors. The difficulties in the calculation of some radial factors are illustrated in the low‐lying states of the carbon atom. Single‐particle methods such as Hartree–Fock and approximate density functional theory cannot ensure the correct expansion of the density in spherical harmonics. Wave‐function methods are appropriate but, as some expansion terms are entirely due to correlation, these methods only will give correct results for high‐quality variational functions. Using full‐configuration integration (CI), all the terms predicted by the theory appear and are not negligible but the convergence of the term due to correlation toward its correct value is uncertain even for very large CI spaces. © 2012 Wiley Periodicals, Inc. 相似文献
997.
Resilience of systems to failures during functioning is of great practical importance. One of the strategies that might be considered to enhance reliability and resilience of a system is swapping components when a component fails, thus replacing it by another component from the system that is still functioning. This paper studies this scenario, particularly with the use of the survival signature to quantify system reliability, where it is assumed that such a swap of components requires these components to be of the same type. We examine the effect of swapping components on a reliability importance measure for the specific components, and we also consider the joint reliability importance of two components. Such swapping of components may be an attractive means toward more resilient systems and could be an alternative to adding more components to achieve redundancy of repair and replacement activities. 相似文献
998.
We studied some topological properties of the space of bounded Volterra-type integral operators on generalized Fock spaces with weight function growing faster than the classical Gaussian function. In particular, the connected and path-connected components, isolated and essentially isolated points of the space are described. The result shows that while the space contains all the non-compact operators as its isolated points, it fails to admit essentially isolated points. 相似文献
999.
Exploring micropolar effects in thin film lubrication 总被引:1,自引:0,他引:1
The micropolar theory for fluids is adopted to probe the effect of the microstructure and microrotation on lubrication features in thin film lubrication. Micropolarity will give rise to an increase in the equivalent viscosity that subsequently leads to a better lubrication. The effective viscosity grown with micro polarity is very close to that of experiment in a preceding work. 相似文献
1000.
以Nd2Fe14B/αFe为例,采用立方体晶粒结构模型,研究了纳米复合永磁材料中不同磁性晶粒间的交换耦合相互作用和有效各向异性.纳米复合永磁材料的有效各向异性Keff等于软、硬磁性相各向异性的统计平均值,每个晶粒的各向异性由晶粒表面交换耦合部分和晶粒内部未交换耦合部分的各向异性共同确定.计算结果表明,软、硬磁性相晶粒尺寸分布显著地影响有效各向异性Keff的值.当软、硬磁性晶粒尺寸D相同时,Keff随晶粒尺寸和硬磁性相体积分数的降低而减小, 当D<20nm 时,K
关键词:
纳米复合永磁材料
交换耦合相互作用
有效各向异性
晶粒尺寸 相似文献