全文获取类型
收费全文 | 141篇 |
免费 | 5篇 |
专业分类
化学 | 95篇 |
力学 | 4篇 |
数学 | 4篇 |
物理学 | 26篇 |
无线电 | 17篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 10篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 14篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 9篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有146条查询结果,搜索用时 15 毫秒
111.
The microscopic driving mechanisms for the structural phase transition on W(001) and Mo(001) surfaces are discussed. It is argued that the coherence length is short for these systems and an effective lattice dynamic Hamiltonian is appropriate for the study of these transitions. The Migdal renormalization scheme is applied to a simple model Hamiltonian and the overall phase diagram in the temperature-anisotropy field plane is obtained. 相似文献
112.
113.
An accurate fT measurement technique is presented, enabling to derive, after correction for the diffusion capacitance, the emitter transition capacitance from fT(IC). Results are compared with the Poon-Gummel C-V expression, confirming experimentally a maximum of transition-layer capacitance at the “built-in” voltage V1. 相似文献
114.
The achievable throughput of a high-resolution electron-beam pattern generator in which a matrix of 1000 individually blankable 0.1-μm-sized pixels is scanned in a raster should be about 0.5 cm2/s. This is an order of magnitude greater than for the best existing shaped-beam vector-scan machine. The matrix could be formed by splitting a solid beam into beamlets which pass through an array of blankers. The beam splitter and array optics can be corrected for spherical aberration so that all the beamlets can be brought together at the entrance to the projection/deflection system. 相似文献
115.
Yamahata C Vandevyver C Lacharme F Izewska P Vogel H Freitag R Gijs MA 《Lab on a chip》2005,5(10):1083-1088
We discuss the successful transport of jurkat cells and 5D10 hybridoma cells using a reciprocating micropump with nozzle-diffuser elements. The effect of the pumping action on cell viability and proliferation, as well as on the damaging of cellular membranes is quantified using four types of well-established biological tests: a trypan blue solution, the tetrazolium salt WST-1 reagent, the LDH cytotoxicity assay and the calcium imaging ATP test. The high viability levels obtained after pumping, even for the most sensitive cells (5D10), indicate that a micropump with nozzle-diffuser elements can be very appropriate for handling living cells in cell-on-a-chip applications. 相似文献
116.
Novel approach for fritless capillary electrochromatography 总被引:1,自引:0,他引:1
At present, the main limitation for the further adoption of capillary electrochromatography (CEC) in the (routine) laboratory is caused by the lack of reproducible and stable columns. The main source of column instability is concentrated in the frits needed to retain the packed bed inside the CEC capillary. The sintering process used to prepare the frits can be rather problematic and irreproducible, particularly for small stationary phase particles and wide column diameters. Since the (surface) composition of the frits is different from the bulk stationary phase packing, different electroosmotic flow (EOF) velocities are generated. This effect is assumed to be primarily responsible for rapid column destruction. In this contribution, a novel approach for the preparation of fritless CEC capillaries is presented and evaluated. Using 5 microm Hypersil ODS particles, separation efficiencies in the range of 130,000-200,000 plates/m were obtained. In a 100 microm inner diameter packed column, electrical currents up to 50 microA could be tolerated without negative effects such as bubble formation. The prepared CEC columns were found to be stable and could easily be operated continuously for several days without column damage. An additional advantage of the proposed tapering approach is that application of pressure on the in- and outlet vial during separation was not required to prevent bubble formation. 相似文献
117.
van Zutphen S Robillard MS van der Marel GA Overkleeft HS den Dulk H Brouwer J Reedijk J 《Chemical communications (Cambridge, England)》2003,(5):634-635
A method for obtaining potentially anti-tumour active dinuclear platinum coordination compounds via solid-phase inorganic synthesis is described for the first time. 相似文献
118.
Internal modification of poly(dimethylsiloxane) microchannels with a borosilicate glass coating 总被引:2,自引:0,他引:2
Orhan JB Parashar VK Flueckiger J Gijs MA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):9154-9161
We report on an original technique for the in situ coating of poly(dimethylsiloxane) (PDMS) microchannels with borosilicate glass, starting from an active nonaqueous and alkali-free precursor solution. By chemical reaction of this active solution inside the microchannel and subsequent thermal annealing, a protective and chemically inert glass borosilicate coating is bonded to the PDMS. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and nuclear magnetic resonance spectroscopy of the active solution show that it is composed of a silicon oxide network with boron connectivity. Thermal gravimetric analysis demonstrates the absence of organic content when curing is done above 150 degrees C. The borosilicate nature of the glass coating covalently bonded to the PDMS is demonstrated using ATR-FTIR spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy and scanning electron microscopy show a smooth and crack-free coating. The latter is used as an efficient protective barrier against diffusion in PDMS of fluorescent rhodamine B dye that is dissolved either in water or in toluene. Moreover, the coating prevents swelling and consequent structural damage of the PDMS when the latter is exposed to harsh chemicals such as toluene. 相似文献
119.
The shear flow of two-dimensional foams is probed as a function of shear rate and disorder. Disordered, bidisperse foams exhibit strongly shear rate dependent velocity profiles. This behavior is captured quantitatively in a simple model based on the balance of the time-averaged drag forces in the system, which are found to exhibit power-law scaling with the foam velocity and strain rate. Disorder makes the scaling of the bulk drag forces different from that of the local interbubble drag forces, which we evidence by rheometrical measurements. In monodisperse, ordered foams, rate independent velocity profiles are found, which lends further credibility to this picture. 相似文献
120.