全文获取类型
收费全文 | 863篇 |
免费 | 19篇 |
国内免费 | 6篇 |
专业分类
化学 | 418篇 |
晶体学 | 1篇 |
力学 | 37篇 |
数学 | 183篇 |
物理学 | 249篇 |
出版年
2022年 | 6篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 35篇 |
2012年 | 42篇 |
2011年 | 46篇 |
2010年 | 26篇 |
2009年 | 18篇 |
2008年 | 44篇 |
2007年 | 31篇 |
2006年 | 49篇 |
2005年 | 40篇 |
2004年 | 26篇 |
2003年 | 30篇 |
2002年 | 28篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 21篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1965年 | 4篇 |
1890年 | 3篇 |
排序方式: 共有888条查询结果,搜索用时 31 毫秒
1.
2.
3.
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
4.
Matthias Heuchel Martin Bhning Ole Hlck Martin R. Siegert Dieter Hofmann 《Journal of Polymer Science.Polymer Physics》2006,44(13):1874-1897
Atomistic packing models have been created, which help to better understand the experimentally observed swelling behavior of glassy polysulfone and poly (ether sulfone), under CO2 gas pressures up to 50 bar at 308 K. The experimental characterization includes the measurement of the time‐dependent volume dilation of the polymer samples after a pressure step and the determination of the corresponding gas concentrations by gravimetric gas‐sorption measurements. The models obtained by force‐field‐based molecular mechanics and molecular dynamics methods allow a detailed atomistic analysis of representative swelling states of polymer/gas systems, with respect to the dilation of the matrix. Also, changes of free volume distribution and backbone mobility are accessible. The behavior of gas molecules in unswollen and swollen polymer matrices is characterized in terms of sorption, diffusion, and plasticization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1874–1897, 2006 相似文献
5.
Frank Abild-Pedersen Ole Lytken Jakob Engbk Gunver Nielsen Ib Chorkendorff Jens K. Nrskov 《Surface science》2005,590(2-3):127-137
We have, theoretically and experimentally, investigated the dissociation of methane on the terraces and steps of a Ni(1 1 1) surface. Using Density Functional Theory (DFT) total energy calculations combined with Ultra High Vacuum (UHV) experiments, we find that the steps exhibit a higher activity than the terraces. We have, furthermore, investigated how carbon and sulfur present on the surface will deactivate the steps, leaving only the terraces active. We find the intrinsic sticking probabilities of methane on the steps and terraces at 500 K to be 2.8 × 10−7 for the steps and 2.1 × 10−9 for the terraces, in complete agreement with our calculated difference in activation energy of 17 kJ/mol. 相似文献
6.
7.
Peter G. Casazza Ole Christensen Alexander M. Lindner Roman Vershynin 《Proceedings of the American Mathematical Society》2005,133(4):1025-1033
We show that the conjectured generalization of the Bourgain-Tzafriri restricted-invertibility theorem is equivalent to the conjecture of Feichtinger, stating that every bounded frame can be written as a finite union of Riesz basic sequences. We prove that any bounded frame can at least be written as a finite union of linearly independent sequences. We further show that the two conjectures are implied by the paving conjecture. Finally, we show that Weyl-Heisenberg frames over rational lattices are finite unions of Riesz basic sequences.
8.
9.
10.
Dr. Sigmund Lustgarten 《Monatshefte für Chemie / Chemical Monthly》1882,3(1):715-722
Ohne ZusammenfassungDiese Abhandlung ist schon im Maihefte der Sitzungsberichte erschienen, war auch für das entsprechende fünfte Heft der Monatshefte bestimmt, ist aber durch ein Versehen aus demselben weggeblieben. 相似文献