全文获取类型
收费全文 | 154篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 93篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 6篇 |
物理学 | 48篇 |
出版年
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有156条查询结果,搜索用时 15 毫秒
11.
The reaction of enol acetates with alcohols in the presence of a catalytic amount of a rhenium complex, such as ReBr(CO)5, produced the corresponding ketones and aldehydes in moderate to good yields. It was suggested that the preparation of an ether, an intermolecular dehydrated product, was the first step of the reaction. 相似文献
12.
13.
M. Kambara K. Miyake K. Murata T. Izumi Y. Shiohara T. Umeda 《Physica C: Superconductivity and its Applications》2000,330(3-4):191-202
Crystal growth of the melt-textured bulk Nd1+xBa2−xCu3O6+d (Nd123) superconducting oxides was investigated by employing isothermal undercooling solidification with hot-seeding in air. From the relationship between growth length and holding time, the Nd123 crystal was found to have almost stopped growing after a certain growth period, while the growth length increased proportionally to the holding time at an early stage of the crystal growth. As a result of quantitative analysis for the Nd123 crystal of which solidification was terminated, the distribution of the Nd/Ba substitution was observed to decrease in the Nd123 single crystal matrix from the seed crystal to the edge of the Nd123 crystals. Also, the substitution content at the edge of the Nd123 crystal, which corresponds to that at the final stage of the crystal growth, was found to be in good agreement with the minimum substitution of the Nd123 solid solution phase in the equilibrium phase diagram at this process temperature. These compositional changes could be explained using the equilibrium phase diagram as associated with the solid solution formation, which is responsible for the non-steady state solidification of the Nd123 crystals even for the isothermal undercooling processing. 相似文献
14.
Inhibition of the mevalonate pathway by an HMG-CoA reductase inhibitor, mevalotin, in Streptomyces prunicolor possessing both mevalonate and MEP pathways resulted in the production of a new metabolite mevashuntin that consisted of conjugated thiazolone and pyranonaphthoquinone moieties. 相似文献
15.
Optically driven actuators have a feature of a non-contact method supplied by light energy. A new method is proposed with
three poly(vinylidene difluoride) (PVDF) cantilevers as the legs and a polymer film as the body. The PVDF cantilevers are
coated with silver on one surface. When one side of the cantilever is irradiated by a laser beam, an electric field is produced
along a cross-section of the cantilever by the pyroelectric effect and a mechanical displacement occurs by the piezoelectric
effect. Its response time and its generated force are measured experimentally. Two types of optically driven actuators using
PVDF film are proposed to move using different characteristics. 相似文献
16.
17.
Minoru Umeda Hiroyuki Ojima Mohamed Mohamedi Isamu Uchida 《Journal of Polymer Science.Polymer Physics》2002,40(11):1103-1109
Methanol vapor‐induced membranous changes in a cast‐coated Nafion thin film were studied through current–voltage (I–V) characteristics with an interdigitated microarray (IDA) electrode and atomic force microscopy (AFM). The obtained I–V curves showed that the as‐prepared Nafion film was stable under humidified nitrogen gas; however, the I–V profile dramatically changed with exposure to methanol vapor. Next, the morphology of the film was compared before and after methanol exposure with AFM images. On the basis of our observations, we found that the as‐prepared film had an irregularly complicated microstructure, whereas the structure became homogeneous in appearance after 30 min of exposure to methanol gas. The alternating‐current conductivity data, showing almost the same magnitude before and after exposure, strongly suggested that the I–V profile shift was based on a change in an electrode reaction mechanism induced by a change in the junction at the Nafion/IDA electrode interface. Furthermore, the methanol vapor‐pre‐exposed Nafion was stable for further exposure to methanol vapor, water vapor, or both. With the stabilized film used in combination with the IDA electrode, a reversible change in the magnitude of the current was observed when the methanol/water vapor ratio was varied. This indicated that the electrode reaction had good reproducibility after the treatment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1103–1109, 2002 相似文献
18.
Mechanical Characterization Measurement of Polymer Material under Stress by Birefringence Microscope
Some polymer materials under tensile stress provide us interesting information. Internal structure changes of polymer materials
must be observed by external stress. Birefringence shows the orientation characteristic in molecular orientation. A microscopic
measurement system for birefringence distribution is proposed to analyze the relation between applied stress and birefringence
distribution of an internal structure. Birefringence distributions of gelatin such as phase difference and azimuthal angle
are shown in cases of loading and unloading stress as a demonstration. The phase difference increased nonlinearly with each
process, and change of birefringence in the elastic domain was different from that in the plastic domain. 相似文献
19.
Koji Umeda Takahiro Hanamuro Kunimi Yamada Yoshimitsu Negishi Hideki Iwano Tohru Danhara 《Radiation measurements》2007,42(10):1647-1654
20.
Interaction of von Karman vortices and intersecting main streams in staggered tube bundles 总被引:2,自引:0,他引:2
Flow visualization, heat transfer and pressure drop characteristics in flow through staggered tube bundles have been regarded
as classical, with results well-documented. However, the mechanism of producing such results has been left untouched. Applications
of staggered tube bundles are abundant in industry, for example as heat exchange devices like the shell-and-tube type and
fuel bundles in nuclear reactor cores. An experimental study is recorded in the present paper which investigates the interaction
of von Karman vortices and intersecting main streams in staggered tube bundles. Flow visualization by means of the particle
tracing method, laser Doppler velocimetry (LDV) and pressure drop measurements using a piezometer are conducted. A modified Reynolds number appropriate to flow through
a staggered tube arrangement is defined together with a pressure drop coefficient. Auto-correlation and power spectrum analyses
of signals obtained from LDV measurements yield an optimum spectrum frequency which is correlated against the Reynolds number. It is concluded that flow
characteristics in staggered tube bundles are determined by the interaction between the von Karman vortex street and X-shaped
interacting main streams.
Received: 4 August 1997 / Accepted: 3 October 1998 相似文献