全文获取类型
收费全文 | 22080篇 |
免费 | 3757篇 |
国内免费 | 3137篇 |
专业分类
化学 | 16877篇 |
晶体学 | 259篇 |
力学 | 1304篇 |
综合类 | 198篇 |
数学 | 2793篇 |
物理学 | 7543篇 |
出版年
2024年 | 26篇 |
2023年 | 344篇 |
2022年 | 560篇 |
2021年 | 672篇 |
2020年 | 770篇 |
2019年 | 823篇 |
2018年 | 716篇 |
2017年 | 691篇 |
2016年 | 963篇 |
2015年 | 1096篇 |
2014年 | 1275篇 |
2013年 | 1676篇 |
2012年 | 1957篇 |
2011年 | 2010篇 |
2010年 | 1446篇 |
2009年 | 1415篇 |
2008年 | 1586篇 |
2007年 | 1428篇 |
2006年 | 1275篇 |
2005年 | 1141篇 |
2004年 | 935篇 |
2003年 | 726篇 |
2002年 | 751篇 |
2001年 | 637篇 |
2000年 | 503篇 |
1999年 | 458篇 |
1998年 | 419篇 |
1997年 | 317篇 |
1996年 | 311篇 |
1995年 | 286篇 |
1994年 | 260篇 |
1993年 | 214篇 |
1992年 | 178篇 |
1991年 | 188篇 |
1990年 | 188篇 |
1989年 | 134篇 |
1988年 | 125篇 |
1987年 | 94篇 |
1986年 | 77篇 |
1985年 | 76篇 |
1984年 | 34篇 |
1983年 | 39篇 |
1982年 | 29篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1973年 | 9篇 |
1936年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Xi Nian FANG Jian Hua WANG 《数学学报(英文版)》2006,22(6):1819-1824
In this paper, we study the extension of isometries between the unit spheres of normed space E and C(Ω). We obtain that any surjective isometry between the unit spheres of normed space E and C(Ω) can be extended to be a linear isometry on the whole space E and give an affirmative answer to the corresponding Tingley's problem (where Ω be a compact metric space). 相似文献
112.
In this paper, we study a micro‐macro model for polymeric fluid. The system involves coupling between the macroscopic momentum equation and a microscopic evolution equation describing the combined effects of the microscopic potential and thermofluctuation. We employ an energetic variation procedure to explore the relation between the macroscopic transport of the particles and the induced elastic stress due to the microscopic structure. For the initial data not far from the equilibrium, we prove the global existence and uniqueness of classical solutions to the system. © 2006 Wiley Periodicals, Inc. 相似文献
113.
A Novel Analytical Approach for Multi-Layer Diaphragm-Based Optical Microelectromechanical-System Pressure Sensors
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An optical microelectromechanical-system (MEMS) pressure sensor based on multi-layer circular diaphragm is described and analysed by using the proposed novel analytical approach and the traditional transfer matrix method. The analytical expressions of the deflection of multi-layer diaphragm and absolute optical reflectance are derived respectively. The influence of residual stress on the deflection of diaphragm is also analysed. Simulation results given by the finite element method are consistent with the ones which are analysed by using the analytical approach. The analytical approach will be helpful to design and fabricate the optical MEMS pressure sensors with multi-layer diaphragm based on Fabry-Perot interferometry. 相似文献
114.
Kristian Smistrup Peter T. Tang Ole Hansen Mikkel F. Hansen 《Journal of magnetism and magnetic materials》2006,300(2):418-426
We demonstrate a simple scheme for fabrication of microelectromagnets consisting of planar spiral coils semi-encapsulated in soft magnetic yokes using conventional microfabrication techniques. The microelectromagnets are suitable for applications operating at frequencies below 250 kHz. Conventional fabrication schemes for planar microelectromagnets typically rely on five mask steps. We allow the current to flow in the soft magnetic yoke and thereby two mask steps are eliminated. We have characterized the electromagnets electrically, the results agree well with theory, and the implications arising from current flowing in the magnetic yoke are discussed. We have integrated the microelectromagnets with microfluidic channels, and demonstrated separation of commercially available magnetic beads from a fluid in a microfluidic system, i.e. a lab-on-a-chip system. 相似文献
115.
Hua Zhang Nabil A. Amro Robert Elghanian Joseph Fragala 《Applied Surface Science》2006,253(4):1960-1963
A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications. 相似文献
116.
The hydrothermal synthesis and magnetic entropy change for the perovskite manganite La0.5Ca0.3Sr0.2MnO3 have been studied. The La0.5Ca0.3Sr0.2MnO3 can be produced as phase-pure, crystalline powders in one step from solutions of metal salts in aqueous potassium hydroxide solution at a temperature of 513 K in 72 h. Scanning electron microscopy shows that the materials are made up of cuboid-shaped particles in typical dimension of 4.0×2.5×1.6 μm. Heat treatment can improve the magnetocaloric effect for the hydrothermal sample. The maximum magnetic entropy change ΔSM for the as-prepared sample is 0.88 J kg−1 K−1 at 315 K for a magnetic field change of 2.0 T. It increases to 1.52 J kg−1 K−1, near its Curie temperature (317 K) by annealing the sample at 1473 K for 6 h. The hydrothermal synthesis method is a feasible route to prepare high-quality perovskite material for magnetic refrigeration application. 相似文献
117.
118.
采用真空熔融缓冷方法制备了单相β-Zn4Sb3以及含有过量Zn的β-Zn4Sb3块体热电材料.在300—700K的温度范围内测试了材料的电导率、Seebeck系数和热导率,研究了β-Zn4Sb3化合物中过量Zn的分布状态及其对材料热电性能的影响规律.结果表明:过量的Zn作为第二相较均匀的分布在β-Zn4Sb3的晶界上,随着Zn含量增加,材料电导率和热导率上升,Seebeck系数下降,Zn第二相的引入能有效提高材料的功率因子,Zn过量2at%的材料在700K时其ZT值达到1.10. 相似文献
119.
120.