全文获取类型
收费全文 | 410篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 215篇 |
力学 | 28篇 |
数学 | 47篇 |
物理学 | 126篇 |
出版年
2021年 | 3篇 |
2019年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 22篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 23篇 |
2007年 | 17篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1942年 | 1篇 |
1930年 | 4篇 |
1918年 | 1篇 |
1881年 | 2篇 |
排序方式: 共有416条查询结果,搜索用时 15 毫秒
51.
52.
53.
Isobaric variations of the characteristic temperatures Tg and Tmax, obtained on uniform cooling and heating of glasses, are investigated in terms of their dependence on the relevant experimental variables, using a single retardation time model. The corresponding partial derivatives of Tg and Tmax are derived as functions of the partition parameter x (ranging between zero and unity), which determines the relative contributions of temperature and structure to the retardation time. It is shown that the variation of Tg with the cooling rate is independent of x. In contrast, Tmax critically depends on x, and its value as well as those of its three partial derivatives are linear functions of x?1. The variations of Tmax are analyzed in terms of a set of reduced variables, leading to simple reduction rules between any two of the experimental variables when the third is kept invariant. The reduction rules are further substantiated by investigating the behavior of glasses in two-step thermal cycles, which result in a unique set of inter-relationships between any pair of the partial derivatives of Tmax, whatever the value of x. The results are discussed in terms of their relevance to the behavior of real glasses. 相似文献
54.
Self-assembled shells composed of colloidal particles: fabrication and characterization 总被引:1,自引:0,他引:1
Hsu MF Nikolaides MG Dinsmore AD Bausch AR Gordon VD Chen X Hutchinson JW Weitz DA Marquez M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2963-2970
We construct shells with tunable morphology and mechanical response with colloidal particles that self-assemble at the interface of emulsion droplets. Particles self-assemble to minimize the total interfacial energy, spontaneously forming a particle layer that encapsulates the droplets. We stabilize these layers to form solid shells at the droplet interface by aggregating the particles, connecting the particles with adsorbed polymer, or fusing the particles. These techniques reproducibly yield shells with controllable properties such as elastic moduli and breaking forces. To enable diffusive exchange through the particle shells, we transfer them into solvents that are miscible with the encapsulant. We characterize the mechanical properties of the shells by measuring the response to deformation by calibrated microcantilevers. 相似文献
55.
56.
George Hutchinson 《Journal of Pure and Applied Algebra》1977,10(2):115-119
Let R be a ring with 1, Rop the opposite ring, and R-Mod the category of left unitary R-modules and R-linear maps. A characterization of well-powered abelian categories such that there exists an exact embedding functor →R-Mod is given. Using this characterization and abelian category duality, the following duality principles can be established.Theorem. There exists an exact embedding functor →R-Mod if and only if there exists an exact embedding functor op→Rop-Mod.Corollary. If R-Mod has a specified diagram-chasing property, then Rop-Mod has the dual property.A lattice L is representable by R-modules if it is embeddable in the lattice of submodules of some unitary left R-module; (R) denotes the quasivariety of all lattices representable by R-modules.Theorem. A lattice L is representable by R-modules if and only if its order dual L1 is representable by Rop-modules. That is, .If is a commutative ring with 1 and a specified diagram-chasing result is satisfied in R-Mod, then the dual result is also satisfied in R-Mod. Furthermore, is self-dual: 相似文献
57.
Dunbar AD Richardson TH McNaughton AJ Hutchinson J Hunter CA 《The journal of physical chemistry. B》2006,110(33):16646-16651
The visible absorption spectra of various substituted porphyrin compounds both in chloroform solution and as Langmuir-Blodgett (LB) solid-state films have been investigated. The porphyrin compounds examined were the Zn, Sn, Mg, and free base derivatives of 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO). Changes in the absorption spectra of these materials induced by their exposure to various organic compounds are reported with a view toward determining whether this is a useful approach toward an optical gas sensor. 相似文献
58.
Bence Paul Kai Kysenius James B. Hilton Michael W. M. Jones Robert W. Hutchinson Daniel D. Buchanan Christophe Rosty Fred Fryer Ashley I. Bush Janet M. Hergt Jon D. Woodhead David P. Bishop Philip A. Doble Michelle M. Hill Peter J. Crouch Dominic J. Hare 《Chemical science》2021,12(30):10321
Tumours are abnormal growths of cells that reproduce by redirecting essential nutrients and resources from surrounding tissue. Changes to cell metabolism that trigger the growth of tumours are reflected in subtle differences between the chemical composition of healthy and malignant cells. We used LA-ICP-MS imaging to investigate whether these chemical differences can be used to spatially identify tumours and support detection of primary colorectal tumours in anatomical pathology. First, we generated quantitative LA-ICP-MS images of three colorectal surgical resections with case-matched normal intestinal wall tissue and used this data in a Monte Carlo optimisation experiment to develop an algorithm that can classify pixels as tumour positive or negative. Blinded testing and interrogation of LA-ICP-MS images with micrographs of haematoxylin and eosin stained and Ki67 immunolabelled sections revealed Monte Carlo optimisation accurately identified primary tumour cells, as well as returning false positive pixels in areas of high cell proliferation. We analysed an additional 11 surgical resections of primary colorectal tumours and re-developed our image processing method to include a random forest regression machine learning model to correctly identify heterogenous tumours and exclude false positive pixels in images of non-malignant tissue. Our final model used over 1.6 billion calculations to correctly discern healthy cells from various types and stages of invasive colorectal tumours. The imaging mass spectrometry and data analysis methods described, developed in partnership with clinical cancer researchers, have the potential to further support cancer detection as part of a comprehensive digital pathology approach to cancer care through validation of a new chemical biomarker of tumour cells.Digital pathology and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging reveals a unique elemental signature of colorectal cancer. 相似文献
59.
Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems. 相似文献
60.
Tunable ultraviolet laser source based on solid-state dye laser technology and CsLiB(6)O(10) harmonic generation 总被引:1,自引:0,他引:1
Tunable UV radiation centered at 289nm was obtained from a 532-nm Nd:YAG pumped high-brightness solid-state dye laser, frequency doubled in CsLiB(6)O(10). Frequency doubling to 284-294 nm was demonstrated from a singly doped, rotating pyrromethene dye plastic disk with damage threshold >3 J/cm(2) . UV energies up to 44 mJ at 10 Hz were obtained with a 15% absolute conversion efficiency from 532 nm. 相似文献