全文获取类型
收费全文 | 82篇 |
免费 | 0篇 |
专业分类
化学 | 68篇 |
力学 | 1篇 |
数学 | 6篇 |
物理学 | 7篇 |
出版年
2021年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1960年 | 1篇 |
1934年 | 2篇 |
排序方式: 共有82条查询结果,搜索用时 17 毫秒
21.
Rubber-modification of polyamide is a widely-applied method of improving material resistance under high strain rate loading. The processing conditions used for preparing such two-phase blends strongly influence their structure and thus their subsequent impact properties. In the present work the relationships between production parameters, phase structure and impact resistance have been studied, and the rǒle of the rubber phase in promoting energy absorption investigated. It has been found that improved impact resistance, defined as a combination of high resistance to crack initiation and to crack propagation, is achieved by decreasing the polyamide phase viscosity while increasing the extrusion and injection temperatures, the mixing shear rate and the rubber phase volume fraction; an EPR modifier offers superior performance to a polybutadiene modifier; the dominant mechanisms of energy-absorption are shearing and void formation, there being no clear evidence of crazing; the J-integral technique of plastic fracture mechanics can be applied to Charpy impact testing; TEM allied with image analysis techniques provides quantitative morphological information on polymer blends. 相似文献
22.
Christopher J. G. Plummer Rudolf Gensler Hans-Henning Kausch 《Colloid and polymer science》1997,275(11):1068-1077
Melt crystallized isotactic polypropylene thin films of thickness between 30 and 100 nm have been investigated by high-resolution
transmission electron microscopy at room temperature. The c-axis projection of the 2*31 helices and their packing in the lattice were clearly visible in flat-on lamellae of the α-phase following reconstruction
from the components of the image Fourier transform corresponding to the (1 1 0) and (0 4 0) lattice planes, and the image
power spectra also indicated contributions from (1 3 0) and (0 6 0) relfections, corresponding to a line resolution of about
0.35 nm. These results are discussed in terms of Bloch wave calculations based on the generally accepted structure for the
α-phase. Attempts to obtain lattice images of the β-phase in isotactic polypropylene and melt crystallized syndiotactic polypropylene
under similar operating conditions are also briefly discussed, although these provided relatively little structural information.
Received: 27 June 1997 Accepted: 15 August 1997 相似文献
23.
Summary Depolarized light scattering of amorphous polycarbonate (PC) is angular independent. The amount of scattering did not give any evidence for the existence of a liquid crystal type of phase, consisting of regions with a strong orientation correlation between chain segments. Annealing of PC belowT
g
does not affect its scattering behaviour. Therefore, observed changes in physical properties such as the mechanical behaviour cannot be interpreted by an appreciable increase of intermolecular orientation correlation. If PC is heated at 190 °C for several days, an angular dependent scattering component appears. This component arises from the formation of spherulites with a sheaf-like structure.With 4 figures and 1 table 相似文献
24.
The 13C NMR spectra of [1.2]-spirenes 2 and spiro[2.4]hepta-(4.6)-dienes 5 are described and the effects of substituents are discussed. A bonding model of the [1.2]-spirenes 2 is derived on the basis of C-H coupling constants and calculated charge densities. The 13C NMR shifts of 1-aryl-spiro[2.4]hepta-(4.6)-dienes 6 show a good correlation with the Hammett σp constants of the substituents in p-position of the phenyl ring. Conclusions on spiroconjugation in [1.2]-spirenes 2 are drawn from comparing the 13C shifts of similar substituted [1.2]-spirenes and spiro[2.4]hepta-(4.6)-dienes. The spiroconjugation in [1.2]-, [2.2]- and [2.3]-spirenes 2, 3 and 4 is discussed comparing the calculated charge densities with the δ (13C) values, as well as the UV and p.e. spectra. 相似文献
25.
Routine MW analysis of polymers is generally performed in solution by Gel Permeation Chromatography. The technique, however, presents increasing difficulties in the ultra-high and ultra-low MW range. Moreover, GPC is not applicable to most fluorinated and»high performance«thermoplastics which require dissolution temperatures close to the polymer melting point. In response to these challenges, polymer scientists have developed new methods of MWD determination. Although these methods have not yet reached the versatility of GPC, they present potential for further development and are interesting as complementary techniques to GPC. For sparingly soluble polymers, melt viscoelastic properties have been used to obtain information on polymer MWD. Flow birefringence, based on the orientation and extension of long flexible molecular chains in a shear field, has been applied to the characterization of ultra-high MW polymers. For low MW polymers and oligomers, the MALDI mass spectrometry technique, with its unique capabilities to resolve individual oligomers within a MWD, proves to be an interesting alternative to conventional GPC characterization. 相似文献
26.
27.
28.
Dr. Florian Puls Felix Seewald Dr. Vadim Grinenko Prof. Dr. Hans-Henning Klauß Prof. Dr. Hans-Joachim Knölker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(67):16776-16787
The hexadecafluorophthalocyanine–iron complex FePcF16 was recently shown to convert olefins into ketones in the presence of stoichiometric amounts of triethylsilane in ethanol at room temperature under an oxygen atmosphere. Herein, we describe an extensive mechanistic investigation for the conversion of 2-vinylnaphthalene into 2-acetylnaphthalene as model reaction. A variety of studies including deuterium- and 18O2-labeling experiments, ESI-MS, and 57Fe Mössbauer spectroscopy were performed to identify the intermediates involved in the catalytic cycle of the oxidation process. Finally, a detailed and well-supported reaction mechanism for the FePcF16-catalyzed Wacker-type oxidation is proposed. 相似文献
29.
Hans-Henning Kausch-Blecken von Schmeling 《Colloid and polymer science》2011,289(13):1407-1427
A definition of macromolecular science (as opposed to polymer science and engineering) is given, from which the year 1930 is derived as the year of its birth. The scope of treatment of this paper will be limited
to solid technical polymers. Some important discoveries of polymer technology in the nineteenth century are reviewed together with the reason why the concept of macromolecules and the theory of rubber
elasticity did not emerge earlier. The role of chain backbones in structure formation and mechanical loading of technical
polymers has been heavily discussed ever since and has attracted this author for most of his scientific work. He offers a
personal perspective of the most important achievements in three domains of macromolecular science: the synthesis of well-designed
chain molecules, structural characterization and the understanding of the micro-mechanics of (nano-structured) polymer materials.
Progress is generally documented by citing individual references from the discussed periods—well knowing that the development
of science is due to the contributions of many more people. In conclusion, a critical outlook will be attempted on future
trends in the design and application of well-adapted—and frequently complex—polymer systems towards growing human needs. 相似文献
30.
H.-H. Kausch R. Gensler Ch. Grein C. J. G. Plummer P. Scaramuzzino 《Journal of Macromolecular Science: Physics》2013,52(5-6):803-815
The deformation processes in crystalline polymers have been studie ever since the discovery of chain folding in 1957. Since then, scientists have been intrigued by the different steps of the transformation of the folded-chain lamellar structure of single crystals or of macroscopically isotropic, often spherulitic, polymers into fibrous morphologies (see Refs. 1 and 2 for early reviews). The importance of molecular tilt, of inter- and intralamellar slip, and of micronecking were rapidly recognized [1–4]. In this paper, we discuss the analogies and differences with respect to crazing of glassy amorphous polymers. Obviously, there is an extensive body of literature on the micromechanics of crazing (see the reviews in Refs. 5–9). On the basis of these studies, it has been established that crazes in amorphous polymers are well-defined regions with approximately planar boundaries that extend perpendicular to the direction of maximum principal tensile stress and that contain highly stretched and voided material [7]. However, crazelike features have also been observed in many semicrystalline polymers (polyethylene [PE], isotactic polypropylene [IPP], isotatic polystyrene [IPS], polyoxymethylene [POM], polyamide 6 and 66 [PA6 and PA66], polycarbonate [PC], polyethylene terephthalate [PET], polybutylene terephthalate [PBT], polyvinylidene fluoride [PVDF], and polyether ether ketone [PEEK]). They are designated in the literature [3–10] as micronecks, true crazes, fibrillar deformation zones (DZs), or simply as crazes since they correspond well to the above definition. 相似文献