全文获取类型
收费全文 | 23026篇 |
免费 | 2543篇 |
国内免费 | 2211篇 |
专业分类
化学 | 2389篇 |
晶体学 | 37篇 |
力学 | 1965篇 |
综合类 | 549篇 |
数学 | 15694篇 |
物理学 | 7146篇 |
出版年
2024年 | 29篇 |
2023年 | 191篇 |
2022年 | 388篇 |
2021年 | 406篇 |
2020年 | 466篇 |
2019年 | 475篇 |
2018年 | 503篇 |
2017年 | 670篇 |
2016年 | 752篇 |
2015年 | 563篇 |
2014年 | 1165篇 |
2013年 | 1493篇 |
2012年 | 1158篇 |
2011年 | 1452篇 |
2010年 | 1305篇 |
2009年 | 1547篇 |
2008年 | 1544篇 |
2007年 | 1666篇 |
2006年 | 1481篇 |
2005年 | 1367篇 |
2004年 | 1169篇 |
2003年 | 1073篇 |
2002年 | 878篇 |
2001年 | 795篇 |
2000年 | 739篇 |
1999年 | 650篇 |
1998年 | 573篇 |
1997年 | 546篇 |
1996年 | 389篇 |
1995年 | 337篇 |
1994年 | 272篇 |
1993年 | 207篇 |
1992年 | 180篇 |
1991年 | 156篇 |
1990年 | 153篇 |
1989年 | 110篇 |
1988年 | 107篇 |
1987年 | 93篇 |
1986年 | 76篇 |
1985年 | 100篇 |
1984年 | 78篇 |
1983年 | 54篇 |
1982年 | 70篇 |
1981年 | 69篇 |
1980年 | 44篇 |
1979年 | 42篇 |
1978年 | 36篇 |
1977年 | 32篇 |
1976年 | 35篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
3.
《Wave Motion》2018
Large cable net structures have been widely applied in aerospace engineering due to the feature of light-weight, high packaging efficiency, and high thermal stability. Structural vibrations induced by a variety of disturbances are inevitable in the space environment, resulting in the requirement of effective vibration control strategies for large cable net structures. Since the large cable net structures have many closely spaced vibrational modes in the range of low frequencies, traditional modal based control may cause modal truncation and spillover problems. In this paper, a wave-based boundary control strategy is adopted and its effectiveness to control the vibration of cable net structures is investigated, by transfer function analysis and numerical methods. It is found that the structural vibration can be absolutely resisted by applying the wave-based boundary controllers onto all the exterior nodes, when disturbances come from the external boundaries of the cable net. Our results in this paper can provide a theoretical basis for the vibration control of large cable net structures. 相似文献
4.
5.
Lithium Insertion Mechanism in Iron-Based Oxyfluorides with Anionic Vacancies Probed by PDF Analysis
Dr. Damien Dambournet Dr. Karena W Chapman Dr. Mathieu Duttine Dr. Olaf Borkiewicz Dr. Peter J Chupas Dr. Henri Groult 《ChemistryOpen》2015,4(4):443-447
The mechanism of lithium insertion that occurs in an iron oxyfluoride sample with a hexagonal–tungsten–bronze (HTB)-type structure was investigated by the pair distribution function. This study reveals that upon lithiation, the HTB framework collapses to yield disordered rutile and rock salt phases followed by a conversion reaction of the fluoride phase toward lithium fluoride and nanometer-sized metallic iron. The occurrence of anionic vacancies in the pristine framework was shown to strongly impact the electrochemical activity, that is, the reversible capacity scales with the content of anionic vacancies. Similar to FeOF-type electrodes, upon de-lithiation, a disordered rutile phase forms, showing that the anionic chemistry dictates the atomic arrangement of the re-oxidized phase. Finally, it was shown that the nanoscaling and structural rearrangement induced by the conversion reaction allow the in situ formation of new electrode materials with enhanced electrochemical properties. 相似文献
6.
7.
本文利用统计计量学方法对山西省农民家庭消费水平和消费结构的变化及原因进行了实证分析。建立了山西省农民人均消费的消费函数和山西省农民总消费支出与食品、衣着、住房、日用品、燃料及文化生活服务支出的关系模型,并通过模型分析解释了农民的消费结构,也为决策者提供一些有效的参考资料。 相似文献
8.
采用密度泛函方法(B3P86)对 Fe_2分子结构进行了优化.计算结果中未观察到自旋污染,基态波函数与高态波函数并未混杂,结果表明,Fe_2中有8个未配对电子,这些电子空间分布不同和自旋平行产生的自旋极化效应,使 Fe_2能量最低.计算结果表明,Fe_2分子的基态是~9∑_g~ ,并非~7Δ_u,进而表明 Fe_2的自旋平行效应比电子自旋配对效应要强.计算得到该分子基态的二阶、三阶和四阶力常数分别为1.4115×10~(-2)aJ/nm~2、-37.1751×10~3aJ/nm~3和 98.7596×10~4aJ/nm~4;光谱数据ω_eχ_e、B_e、α_e分别为0.3522、0.0345、 0.4963×10~(-4)cm~(-1);离解能为3.5522eV,平衡键长为0.2137nm,振动频率为292.914cm~(-1);并得到了 Murrel-Sorbie 函数. 相似文献
9.
A.-S. F. Obada M. Darwish H. H. Salah 《International Journal of Theoretical Physics》2002,41(9):1755-1768
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined. 相似文献
10.
Heinrich Saller 《International Journal of Theoretical Physics》2002,41(8):1491-1509
Unstable particles, together with their stable decay products, constitute probability collectives that are defined as Hilbert spaces with dimension higher than one, nondecomposable in a particle basis. Their structure is considered in the framework of Birkhoff-von Neumann's Hilbert subspace lattices. Bases with particle states are related to bases with a diagonal scalar product by a Hilbert-bein involving the characteristic decay parameters (in some analogy to the n-bein structures of metrical manifolds). Probability predictions as expectation values, involving unstable particles, have to take into account all members of the higher dimensional collective. For example, the unitarity structure of the S-matrix for an unstable particle collective can be established by a transformation with its Hilbert-bein. 相似文献