全文获取类型
收费全文 | 18382篇 |
免费 | 3369篇 |
国内免费 | 4153篇 |
专业分类
化学 | 14028篇 |
晶体学 | 374篇 |
力学 | 1312篇 |
综合类 | 453篇 |
数学 | 2335篇 |
物理学 | 7402篇 |
出版年
2024年 | 46篇 |
2023年 | 305篇 |
2022年 | 624篇 |
2021年 | 667篇 |
2020年 | 758篇 |
2019年 | 706篇 |
2018年 | 666篇 |
2017年 | 702篇 |
2016年 | 818篇 |
2015年 | 901篇 |
2014年 | 1071篇 |
2013年 | 1417篇 |
2012年 | 1603篇 |
2011年 | 1692篇 |
2010年 | 1284篇 |
2009年 | 1333篇 |
2008年 | 1478篇 |
2007年 | 1245篇 |
2006年 | 1189篇 |
2005年 | 1088篇 |
2004年 | 886篇 |
2003年 | 643篇 |
2002年 | 672篇 |
2001年 | 665篇 |
2000年 | 643篇 |
1999年 | 450篇 |
1998年 | 341篇 |
1997年 | 260篇 |
1996年 | 273篇 |
1995年 | 240篇 |
1994年 | 237篇 |
1993年 | 180篇 |
1992年 | 139篇 |
1991年 | 123篇 |
1990年 | 93篇 |
1989年 | 87篇 |
1988年 | 76篇 |
1987年 | 61篇 |
1986年 | 53篇 |
1985年 | 44篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
微裂纹扩展中的分形现象及其计算机仿真 总被引:1,自引:0,他引:1
本文探讨了采用仿真技术研究微裂纹连接过程和生成分形断口表面的可行性,发展了用于仿真微裂纹随机生长行为的GO模型的基本构相,并进行了计算机仿真实验,由此得出了一此有的结论。 相似文献
92.
93.
The sherds of terra-cotta warriors and horses and Lishan clay were characterized by Mossbauer spectroscopy, XRD, XRF, NAA,
thermal and chemical analyses. Lishan clay was testified as the original material of terracotta warriors and horses, the kilning
of these warriors and horses was first carried out in an oxidizing atmosphere, and then changed to a predominantly reducing
atmosphere. With refiring experiments, the temperatures of Q3 and Q4 samples were determined to be 830±50 and 980±50°C respectively.
Transformations of Lishan clay were determined by firing in oxidizing and reducing atmospheres. The Mossbauer parameters of
Lishan clay, which was taken after 2–24h firing, were changing up to 12h. 相似文献
94.
巴旦杏中脂肪酸的测定 总被引:5,自引:1,他引:4
采用气相色谱仪进行定量分析,气-联质联用仪进行定性分析,巴旦杏中脂肪酸进行了测定,并探讨了样品处理方法和气-质联用仪的分析条件,得到了较为满意的分析结果。 相似文献
95.
96.
Stimulated Raman adiabatic passage (STIRAP) has been successfully extended to multilevel system. During the STIRAP process, the intermediate levels have notable population which is detrimental if these levels could decay to other levels through spontaneous emission. This paper proposes a novel method to reduce the intermediate level population during the STIRAP process. A complete population transfer can be achieved in this modified STIRAP even if the intermediate level decays to other levels. 相似文献
97.
Qin Jiang 《Journal of Mathematical Analysis and Applications》2007,328(1):380-389
Some solvability conditions of periodic and subharmonic solutions are obtained for a class of subquadratic nonautonomous second-order Hamiltonian systems by the minimax methods in critical point theory. 相似文献
98.
99.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
100.