全文获取类型
收费全文 | 83篇 |
免费 | 4篇 |
国内免费 | 5篇 |
专业分类
化学 | 46篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 22篇 |
物理学 | 21篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1944年 | 1篇 |
1941年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有92条查询结果,搜索用时 15 毫秒
31.
The thallium-indium alloys were dissolved in sulphuric acid (1 + 1). In this medium thallium remained in the univalent state and could be determined directly, without a separation, by an oxidation-reduction titration with potassium bromate. The indium was determined directly with an EDTA titration. Ascorbic acid was added to maintain the thallium in the univalent state, which did not interfere. Ascorbic acid also masked any interfering tervalent thallium by effectively reducing it to the univalent state. Sharp end-points were obtained for both titrations, which were carried out in the temperature range of 50-95 degrees . The method offers excellent precision and accuracy. 相似文献
32.
Low-voltage polymer-based scanning cantilever for in vivo optical coherence tomography 总被引:2,自引:0,他引:2
Novel hand-held optical coherence tomography (OCT) probes with polymer cantilevers have been developed for clinical oral and skin imaging. An electroactive ionic polymer-metal composite cantilever was used to generate 3-mm transverse scanning movement of an optical fiber with applied 2-V linear alternating voltage at 1 Hz. Low driving voltage ensures safety. Two different optical designs achieve both forward and sidewise scanning and make it possible to image everywhere within the human oral cavity. In vivo OCT imaging of the human tongue is demonstrated. 相似文献
33.
34.
35.
We revise the Atkins model of ion structure in fluids to improve self-consistency. Also, the effects of a small perturbing potential are calculated, and agreement is found with data on impurity ion mobility in liquid helium. 相似文献
36.
37.
E. E. Sigmund V. F. Mitrovi E. S. Calder G. W. Thomas H. N. Bachman W. P. Halperin P. L. Kuhns A. P. Reyes 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,159(2)
We report on a solution to the problem of phase noise in nuclear magnetic resonance (NMR) experiments. Phase noise refers to the variation in the phases of NMR signals from successive acquisitions due to an unstable applied field. Such a situation exists in high-field resistive Bitter magnets and, for sufficiently long timescales, can cause serious signal degradation upon signal averaging. An inductive shield, formed by a highly conducting metal tube placed around the sample and along the applied field, provides screening of the AC components of the applied field and thereby retains phase coherence over long periods. Although simple in principle there are technical difficulties for practical implementation of this method. We present demonstrations of the utility of this approach. In particular, we show a significant extension of the effective transverse coherence time of the 13C resonance in doubly 13C-labeled glycerol in a resistive Bitter magnet. This was accomplished through the use of a highly conducting aluminum shield, cooled to 4 K with liquid helium. 相似文献
38.
Fuzzy and possibilistic optimization methods are demonstrated to be effective tools in solving large-scale problems. In particular,
an optimization problem in radiation therapy with various orders of complexity from 1000 to 62,250 constraints for fuzzy and
possibilistic linear and nonlinear programming implementations possessing (1) fuzzy or soft inequalities, (2) fuzzy right-hand
side values, and (3) possibilistic right-hand side is used to demonstrate that fuzzy and possibilistic optimization methods
are tractable and useful. We focus on the uncertainty in the right side of constraints which arises, in the context of the
radiation therapy problem, from the fact that minimal and maximal radiation tolerances are ranges of values, with preferences
within the range whose values are based on research results, empirical findings, and expert knowledge, rather than fixed real
numbers. The results indicate that fuzzy/possibilistic optimization is a natural and effective way to model various types
of optimization under uncertainty problems and that large fuzzy and possibilistic optimization problems can be solved efficiently. 相似文献
39.
Four-component reactions between amino alcohols, aldehydes, isocyanides and thiols proceed rapidly under microwave or conventional heating at 60 °C in methanol. The reaction is successful with a wide range of components and gives access to potentially drug-like products containing amine, amide and thioether functionality in moderate to excellent yield. The reaction conditions are also applicable to the synthesis of a range of 8-10 membered medium ring lactones via three-component reactions of amino alcohols, isocyanides and acid-aldehydes. Incorporation of L-prolinol as the amino alcohol component in each case gives access to multicomponent products with moderate to high diastereoselectivity. 相似文献
40.
David Bachman 《Mathematische Annalen》2013,355(2):697-728
Let M 1 and M 2 be compact, orientable 3-manifolds with incompressible boundary, and M the manifold obtained by gluing with a homeomorphism ${\phi : {\partial}M_1 \to {\partial}M_2}$ . We analyze the relationship between the sets of low genus Heegaard splittings of M 1, M 2, and M, assuming the map ${\phi}$ is “sufficiently complicated”. This analysis yields counter-examples to the Stabilization Conjecture, a resolution of the higher genus analogue of a conjecture of Gordon, and a result about the uniqueness of expressions of Heegaard splittings as amalgamations. 相似文献