全文获取类型
收费全文 | 180篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 111篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 35篇 |
物理学 | 37篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 17篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
181.
Multi-stage versions of Jacobi relaxation are studied for use in multigrid methods for steady Euler equations. It is shown that these multi-stage versions allow much more general and much more efficient multigrid methods than possible with classic relaxation methods. 相似文献
182.
O. V. Kris’ko V. M. Silonov T. V. Skorobogatova D. A. Kireev 《Moscow University Physics Bulletin》2007,62(4):240-243
An expression for the Fourier transform of the screening electron density of simple metals has been derived using smooth nonlocal model potentials of simple metals. The expression describes the contribution of conduction electrons to the atomic factors of X-ray scattering in simple metals. Aluminum was used as an example for numerical checking. Comparison with the results of similar calculations for the form factor of the Krasko-Gurskii model potential shows the importance of taking the nonlocality of the model potential into account. 相似文献
183.
We show that the electronic part of the linear magnetoelectric response, usually omitted in first-principles studies, can be comparable in magnitude to that mediated by polar lattice distortions, even in strong magnetoelectrics. Using a self-consistent response to a Zeeman field for noncollinear spins, we show how polarization emerges in magnetoelectrics through both electronic and lattice contributions--analogous to the high- and low-frequency responses of dielectrics. The approach we use is computationally simple, and can be used to study linear and nonlinear responses to magnetic fields. 相似文献
184.
Glass dispersed liquid crystal films doped with the tris(β-diketonato)europium(III) complex [Eu(dbm)3(gly)] (Hdbm=dibenzoylmethane, gly=1,2-dimethoxyethane) were prepared. The liquid crystal host was 4-pentyl-4′-cyanobiphenyl (5CB); a mixed silica–titania glass with a refractive index close to that of 5 CB was chosen as the glass matrix. The photoluminescence intensity was measured as a function of temperature. A strong intensity change was observed at the nematic-to-isotropic transition. 相似文献
185.
High polymers are used in medicine, surgery, or artificial organs in three ways: 1) to construct complete artificial replacements for human organs, 2) to repair, sustain, or augment function of normal organs, and 3) to provide a biochemical function. Artificial hearts, heart lung machines, and artificial kidneys are examples of artificial organs that man is designing and building to replace natural organs. Plastics are used widely in their construction. Plastics offer a variety of properties needed for these applications, including ease of fabrication, chemical inertness, and nontoxic properties, and a wide range of physical properties in hardness, flexibility, and permeability. Externally, as adjuncts or assists to natural organs, there are many applications of plastics in present use from clothing to glasses to dentures. Internally, the applications include vascular prostheses, check valve balls for heart valves, encapsulating resins for pacemakers, meshes and foams for reconstructive surgery, drainage tubes, and cannulae for hemodialysis. The plastics most widely used in surgical implants are polytetrafluoroethylene, polypropylene, saturated aromatic polyesters, and polysiloxanes. Growing use is being made of segmented polyurethanes, acrylics, and epoxy resins. Experimental work is under way on polyelectrolytes and various hydrogels based on polyhydroxyl compounds. The newest class of applications of high polymers is that wherein the polymer has a definite and specific chemical interaction with the biochemistry of the body, i.e., it plays a pharmaceutical role. Examples of this include: 1) synthetic ion exchange resins for absorbing metabolites from the blood; 2) synthetic polyelectrolytes capable of absorbing specific viruses; 3) synthetic polymers such as (a) polyinosinic-polycytidylic acid (a synthetic ribonucleic acid) or (b) a copolymer of vinyl pyran and an undisclosed comonomer which promotes the production of interferon, a chemical substance normally produced by cells as an antiviral agent; and 4) synthetic natural-like polypeptides, enzymes, and chemical modifications of these with enhanced biologic activity. The future of the use of high polymers in these applications appears to be in the earliest stages. Half a million Americans die each year of heart disease and 60,000 die of kidney disease, hence the potential for artificial versions of these organs is very large. The use of surgical devices is growing steadily. The use of polymers as drugs has not yet been tapped. In 50 years, biochemists will have a battery of synthetic polymer drugs which will cure many diseases, prevent cancer, speed wound healing, and eventually, it is hoped, provide a chemical regime for regeneration of lost limbs and organs. 相似文献
186.
Josefine Enman Kerstin Ramser Ulrika Rova Kris Arvid Berglund 《Journal of Raman spectroscopy : JRS》2008,39(10):1464-1468
Eritadenine, 2(R),3(R)‐dihydroxy‐4‐(9‐adenyl)‐butyric acid, is a cholesterol‐reducing compound naturally occurring in the shitake mushroom (Lentinus edodes). To identify the unknown Raman spectrum of this compound, pure synthetic eritadenine was examined and the vibrational modes were assigned by following the synthesis pathway. This was accomplished by comparing the known spectra of the starting compounds adenine and D ‐ribose with the spectra of a synthesis intermediate, methyl 5‐(6‐Aminopurin‐9H‐9‐yl)‐2,3‐O‐isopropylidene‐5‐deoxy‐β‐D ‐ribofuranoside (MAIR) and eritadenine. In the Raman spectrum of eritadenine, a distinctive vibrational mode at 773 cm−1 was detected and ascribed to vibrations in the carbon chain, ν(C C). A Raman line that arose at 1212 cm−1, both in the Raman spectrum of MAIR and eritadenine, was also assigned to ν(C C). Additional Raman lines detected at 1526 and at 1583 cm−1 in the Raman spectrum of MAIR and eritadenine were assigned to ν(N C) and a deformation of the purine ring structure. In these cases the vibrational modes are due to the linkage between adenine and the ribofuranoside moiety for MAIR, and between adenine and the carbon chain for eritadenine. This link is also the cause for the disappearance of adenine specific Raman lines in the spectrum of both MAIR and eritadenine. Several vibrations observed in the spectrum of D ‐ribose were not observed in the Raman spectrum of eritadenine due to the absence of the ribose ring structure. In the Raman spectrum of MAIR some of the D ‐ribose specific Raman lines disappeared due to the introduction of methyl and isopropylidene moieties to the ribose unit. With the approach presented in this study the so far unknown Raman spectrum of eritadenine could be successfully identified and is presented here for the first time. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
187.
Kevin W. Mattison Yingfan Wang Kris Grymonpr Paul L. Dubin 《Macromolecular Symposia》1999,140(1):53-76
Negatively charged polyelectrolytes such as carboxymethylcellulose, pectin, and alginate are commonly present in food products. These polyelectrolytes serve a variety of functions such as controlling viscosity and stabilizing emulsions. Proteins are also present in many food formulations. Because of their high charge density, polyelectrolytes can be expected to interact with these proteins. Hence, an understanding of the parameters controlling protein-polyelectrolyte interactions is useful. 相似文献