全文获取类型
收费全文 | 246篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 144篇 |
力学 | 5篇 |
数学 | 50篇 |
物理学 | 53篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 13篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 19篇 |
2006年 | 12篇 |
2005年 | 19篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有252条查询结果,搜索用时 46 毫秒
21.
Iovka Dragieva Christina Deleva Mladen Mladenov Ivania Markova-Deneva 《Monatshefte für Chemie / Chemical Monthly》2002,82(1):807-814
Different structures of the interglobular space or voids between self-organized nanoparticles lead to differences in the measurable magnetic properties of single-domain particle chains of similar composition, grain size, and amorphous structure of the single globules. The volumes and radii of nanoparticles obtained by application of a magnetic field (3 to 15 nm) are larger than those determined without application of a magnetic field during the borohydride reduction process. Two types of hydrogen containing nanotubes with diameters of up to 2 (small-size containers) and 5 nm (large-size containers) are produced using as a driving force the domain wall formation energy between ferromagnetic nanoparticles with quantum size effected dimensions prepared by this reduction method at room temperature and ambient atmosphere. Nanoscale hydrogen containers can be used instead of MeH nanoparticle electrodes as perfect energy charge transfer media of high efficiency (close to 100%) using Li ion electrolytes. No influence on the electrode temperature and no participation of OH− and H2O in the main charge/discharge transfer reactions were observed. 相似文献
22.
This work presents a comparison of convective interaction media (CIM) and controlled pore glass (CPG) as solid supports for
immunoglobulin antibodies used in bioanalytical detection of allergens in foodstuffs. A flow-injection manifold with highly
sensitive thermal lens spectrometric detection was used for this purpose. Using beta-lactoglobulin, a milk allergen, as a
model analyte, CIM disc supports had a higher linear range (0.2–3.5 μg L−1), better reproducibility (intra-day RSD = 1%, inter-day RSD = 10%), lower consumption of reagents, and better immunocolumn
stability (1 month, over 240 injections of substrate), while providing comparable LODs (0.1 μg L−1). Application of CIM discs as solid supports in immunocolumns for allergen detection enables fast and sensitive screening
of allergens in foodstuffs with sample throughput of up to eight samples per hour. 相似文献
23.
24.
Mladen K. Chargin
Ingo Raasch
Rudolf BrunsDawson Deuermeyer
《Finite Elements in Analysis and Design》1991,7(4):343-354Structural optimization is almost as old as the finite element method (FEM). Whereas FEM found its way to real-life applications very quickly, structural optimization remained a topic of interest in the research community for many years. However, there have been a number of attemps recently to develop general purpose program systems for property optimization. For shape optimization, there is no general purpose code currently available that can solve realistic problems. This paper will describe a method of calculating shape sensitivities within
, in a simple manner, without resort to external programs. Once the shape sensitivities are obtained, the shape optimization process can proceed in a manner similar to property optimization. The key concept is the use of natural design variables to define the shape changes in a given structure. The design variables are the magnitudes of enforced displacements applied to the structure. The displacements produced by these variables are added to the initial shape to obtain a new shape. This approach can be computationally intensive and since one shape variable is dependent of another, multiple CPU's can be used to significantly reduce the solution time.
Two examples are solved to demonstrate the capability of these techniques. The first is a cantilever beam with holes loaded by a point load at the free end. The shape of the holes as well as the thickness of the beam are selected as the design variables. The second example is the shape optimization of a connecting rod subjected to several different loading and boundary conditions. 相似文献
25.
26.
In this work, the diffusion properties of single component n-heptane and toluene as well as their binary mixtures in two SBA-15
samples with different structural characteristics were studied by the standard Zero Length Column (ZLC) technique under three
different concentration levels. A theoretical ZLC desorption model considering the Generalized Maxwell-Stefan (GMS) formulation
was developed. Using the independently measured single component equilibrium and kinetic parameters, the model was able to
reasonably predict experimental binary ZLC desorption curve for countercurrent diffusion of toluene in the presence of n-heptane.
However, there was a significant deviation between model prediction results and experimental data for countercurrent desorption
of n-heptane in the presence of toluene. The diffusion of n-heptane is reduced by the presence of toluene, regardless of the
relative content of micropores in the intrawall pores, while that of toluene is virtually unaffected by the counter-diffusion
of n-heptane. The observed phenomena cannot be addressed by the simple model considering the cross term diffusion effect.
The structural property of material and the molecular characteristics of probe molecules were used to account for the difference
in the behavior between n-heptane and toluene. 相似文献
27.
Mladen Pavicic 《International Journal of Theoretical Physics》1998,37(8):2099-2103
It is shown that the identity rule — arule of inference which has the form of modus ponens butwith the operation of identity substituted for theoperation of implication — turns any ortholatticeinto either an orthomodular lattice (a model of a quantumtheory) or a distributive lattice (a model of aclassical theory). It is also shown that — asopposed to the implication algebras — one cannotconstruct an identity algebra although the identity rule contains theoperation of identity as the only operation. 相似文献
28.
L. Hand D. Petersen H. Scott K. Gottfried M. Atac A. L. Read L. Voyvodic W. Czyż B. Furmańska R. Holyński A. Jurak S. Krzywdzinski G. Nowak H. Wilczyński W. Wolter B. Wosiek R. Ball J. Kiley A. Kotlewski L. Litt J. Florian J. J. Lord R. J. Wilkes 《Zeitschrift fur Physik C Particles and Fields》1979,1(2):139-142
An experimental search is presented for the existence of intra-nuclear cascading which, for small values of the Bjorken scaling variable ω, is the only mechanism of particle multiplication in the target nucleus. Our data indicate that cascading does exist as one of the effective mechanisms of particle multiplication in μ-nucleus collisions. No significant variation of the observed multiplicity with ω is observed. 相似文献
29.
Structure and diffusion characterization of SBA-15 materials 总被引:4,自引:0,他引:4
Hoang VT Huang Q Eić M Do TO Kaliaguine S 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):2051-2057
In situ formation of the micro- and mesoporous structures of SBA-15 materials was investigated. It was found that the structure is significantly different from that for cylindrical or hexagonal pores, which suggests that the SBA-15 is more complex than an array of hexagonally ordered channels. Nitrogen adsorption isotherms at 77 K provided evidence that large (primary) mesopores are accompanied by a certain amount of significantly smaller pores with a broad distribution in the micropore/small-mesopore range within the mesoporous walls of main channels. It was found that the microporosity can be controlled by the time of heating as well as the synthesis temperature. The diffusion properties of n-heptane as a probe molecule in four selected SBA-15 samples with different micropore volumes were studied by the standard zero length column technique and related to their structural characteristics. The results have shown that the diffusion process involving n-heptane at a low concentration level takes place inside the walls of main mesoporous channels and depends on the relative content of micropores. In the samples that have a relatively high content of micropores, n-heptane diffusivities are relatively low, their activation energies are high, and the process is similar to diffusion in typical microporous adsorbents, like zeolites. As the micropore content is decreased, diffusion becomes more and more controlled by secondary mesopores of the intrawall pore structure, rendering diffusion faster and activation energies lower. 相似文献
30.
Starcević K Karminski-Zamola G Piantanida I Zinić M Suman L Kralj M 《Journal of the American Chemical Society》2005,127(4):1074-1075
Spectroscopic titrations and thermal denaturation experiments show that "acyclic" analogue 1 does not bind to ds-DNA, but under same conditions "cyclic" 2 strongly interacts with ds-DNA and ds-RNA by intercalation into the double helix. Besides, 2 is significantly more effective in inhibition of the tumor cell growth in vitro than 1. We have shown that it is possible to efficiently and irreversibly convert "DNA inactive" compound 1 into "DNA active" compound 2 by light irradiation of the aqueous solutions of the former. This strategy offers a new and attractive approach to photoinduced anticancer therapy. 相似文献