全文获取类型
收费全文 | 341篇 |
免费 | 6篇 |
专业分类
化学 | 218篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 7篇 |
物理学 | 109篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 11篇 |
2013年 | 52篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 12篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1958年 | 3篇 |
1931年 | 2篇 |
排序方式: 共有347条查询结果,搜索用时 15 毫秒
81.
82.
Many problems based on unstructured grids provide a natural multigrid framework due to using an adaptive gridding procedure.
When the grids are saved, even starting from just a fine grid problem poses no serious theoretical difficulties in applying
multigrid. A more difficult case occurs when a highly unstructured grid problem is to be solved with no hints how the grid
was produced. Here, there may be no natural multigrid structure and applying such a solver may be quite difficult to do.
Since unstructured grids play a vital role in scientific computing, many modifications have been proposed in order to apply
a fast, robust multigrid solver. One suggested solution is to map the unstructured grid onto a structured grid and then apply
multigrid to a sequence of structured grids as a preconditioner.
In this paper, we derive both general upper and lower bounds on the condition number of this procedure in terms of computable
grid parameters. We provide examples to illuminate when this preconditioner is a useful (e. g.,p orh-p formulated finite element problems on semi-structured grids) or should be avoided (e.g., typical computational fluid dynamics
(CFD) or boundary layer problems). We show that unless great care is taken, this mapping can lead to a system with a high
condition number which eliminates the advantage of the multigrid method.
This work was partially supported by ONR Grant # N0014-91-J-1576. 相似文献
83.
84.
85.
J. Leonard S. L. Malhotra 《Journal of polymer science. Part A, Polymer chemistry》1974,12(10):2391-2401
220 MHz NMR spectra of sample of poly-p-isopropyl-α-methylstyrene prepared through anionic (A) and cationic (B) polymerizations are studied. Peaks at τ values of 9.07, 9.41, and 9.71 are assigned to isotactic (i), heterotactic (h), and syndiotactic (s) α-methyl triads, respectively. From the α-methyl triads and the β-proton tetrads it is found that polymer A deviates little from Bernoullian statistics and that first-order Markov configurational statistics applies to polymer B. Isopropyl methine and methyl proton resonances are also analyzed in terms of the configurational statistics of the polymer. Resonances of the phenyl protons are assigned with increasing field to s, h, i meta and ortho protons. 相似文献
86.
Kumaran Ramanathan M.N. Kamalasanan B.D. Malhotra D.R. Pradhan S. Chandra 《Journal of Sol-Gel Science and Technology》1997,10(3):309-316
Physical adsorption and physical entrapment techniques have been utilized for the immobilization of lactate dehydrogenase (LDH) on tetraethylorthosilicate (TEOS) derived sol-gel films. The enzyme (LDH) activity has been assayed as a function of time, temperature, pH and pyruvate concentration. The results of photometric measurements used for monitoring the reaction yield a response time of about 1 min, linearity over a concentration range of 0–1.5 × 10-3 M and detection limit of 5 × 10-5 M. The TEOS sol-gel films containing LDH have been found to be stable for about 30 days at temperatures 4 to 10°C. 相似文献
87.
88.
89.
A d.c. arc emission spectrographic method has been developed for the determination of nine trace impurities in boron nitride. The charge for exciting the sample contains equal quantities of boron nitride and graphite (containing 2% NaF as carrier and 1% La(2)O(3) as an internal standard). The method is useful in the determination of impurities in the range 2-1000 ppm, with a mean relative standard deviation of 13%. 相似文献
90.
Allan J. Easteal Rakesh Malhotra William E. Price Lawrence A. Woolf 《Journal of solution chemistry》1991,20(3):319-334
Intradiffusion of species in acidified (using eithe hydrochloric or perchloric acid) iron(III) chloride solutions has been
studied using labeled iron(III), chloride and water. Comparison with data for iron(III) perchlorate has enabled the influence
of complexed species upon the diffusion to be ascertained. The chloro-iron species formed have larger diffusion coefficients
than the free iron(III) ion as would be expected from their lower net charge. Simple diffusion models have been employed to
enable estimates of the diffusion of the complexed species and of the free chloride diffusion coefficients to be obtained.
These are discussed in relation to literature data for similar systems. In addition esitmates of the effective hydration of
the iron(III) species in solutions have been obtained from the diffusion data. These are discussed in relation to two other
trivalent metal salt systems, chromium chloride and lanthanum chloride; the overall hydration of the three cations is virtually
identical. 相似文献