全文获取类型
收费全文 | 471篇 |
免费 | 48篇 |
国内免费 | 34篇 |
专业分类
化学 | 475篇 |
晶体学 | 2篇 |
力学 | 1篇 |
物理学 | 75篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 49篇 |
2012年 | 20篇 |
2011年 | 19篇 |
2010年 | 34篇 |
2009年 | 29篇 |
2008年 | 26篇 |
2007年 | 29篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 4篇 |
排序方式: 共有553条查询结果,搜索用时 31 毫秒
151.
J. E. Daniels D. Pontoni Rui Ping Hoo V. Honkim?ki 《Journal of synchrotron radiation》2010,17(4):473-478
Combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) is a powerful technique for the study of materials at length scales ranging from atomic/molecular sizes (a few angstroms) to the mesoscopic regime (~1 nm to ~1 µm). A set‐up to apply this technique at high X‐ray energies (E > 50 keV) has been developed. Hard X‐rays permit the execution of at least three classes of investigations that are significantly more difficult to perform at standard X‐ray energies (8–20 keV): (i) in situ strain analysis revealing anisotropic strain behaviour both at the atomic (WAXS) as well as at the mesoscopic (SAXS) length scales, (ii) acquisition of WAXS patterns to very large q (>20 Å?1) thus allowing atomic pair distribution function analysis (SAXS/PDF) of micro‐ and nano‐structured materials, and (iii) utilization of complex sample environments involving thick X‐ray windows and/or samples that can be penetrated only by high‐energy X‐rays. Using the reported set‐up a time resolution of approximately two seconds was demonstrated. It is planned to further improve this time resolution in the near future. 相似文献
152.
P. Kraft O. Bunk F. A. Reifler R. Hufenus M. Heuberger F. Pfeiffer 《Journal of synchrotron radiation》2010,17(2):257-262
A synchrotron study is presented in which the concept of one‐dimensional tomographic reconstruction of small‐angle X‐ray scattering patterns is applied to investigate polyamide 6 monofilaments, dip‐coated with alumina particles. The filaments are scanned with a focused synchrotron beam and the resulting scattering patterns are recorded with a PILATUS 2M detector. The reconstructed sequence of SAXS images reflects the local nanostructure variation along the filament radius. In particular, the influence of coating process parameters on the polyamide 6 is investigated. 相似文献
153.
Ordered mesoporous silicas (OMSs) such as SBA-15 (p6mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 °C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and nitrogen adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 °C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 °C, respectively. 相似文献
154.
Zhiyong Jiang Jens Rieger Dieter Lilge Rainer Gehrke Zhihong Li Yongfeng Men 《European Polymer Journal》2010,46(9):1866-13808
The morphological development of melt-drawn transparent high-density polyethylene during heating was investigated employing in-situ synchrotron small-angle X-ray scattering (SAXS) technique. The results confirm that at lower temperatures only meridional scattering peaks aligned perpendicular to the extensional flow direction can be observed, indicating a highly oriented lamellar crystallite structure; whereas at higher temperatures an equatorial streak additional to the layer-like meridional scattering pattern develops, reflecting the presence of shish-kebab-like objects in the specimen under investigation. Upon heating, the average thickness of the kebab crystals remains essentially unaffected below 110 °C, and subsequently the selective melting of the less stable kebabs proceeds yielding thicker layered lamellar crystals. When the temperature is raised to 131 °C, the shish-like formation and the thermally stable kebab crystals melt simultaneously. In addition, the microstructure of the melt-drawn specimen subjected to annealing at elevated temperatures was probed at room temperature. As opposed to the SAXS patterns registered at high temperatures, the SAXS diagram measured after annealing shows no equatorial streak, suggesting that the cylindrical structures could be re-formed. This observation can be explained by assuming that the plate-like kebab crystals with their normal parallel to the stretching direction grow and impinge during cooling to room temperature due to secondary crystallization, which can be verified by in-situ SAXS experiments during annealing and subsequent cooling. 相似文献
155.
D. Hlavat Z. Hork F. Lednický J. Hromdkov A. Pleska Yu. V. Zanevskii 《Journal of Polymer Science.Polymer Physics》2001,39(9):931-942
The compatibilizing effect of di‐, tri‐, penta‐, and heptablock (two types) copolymers with styrene and butadiene blocks was studied in polystyrene/polypropylene (PS/PP) 4/1 blends. The structure of PS/PP blends with the addition of 5 or 10 wt % of a block copolymer (BC) was determined on several scale levels by means of transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS). The results of the structure analysis were correlated with measured stress‐transfer properties: elongation at break, impact, and tensile strength. Despite the fact that the molar mass of the PS blocks in all the BCs used was about 10,000, that is, below the critical value M* (~18,000) necessary for the formation of entanglements of PS chains, all the BCs used were found to be good compatibilizers. According to TEM, a certain amount of a BC is localized at the interface in all the analyzed samples, and this results in a finer dispersion of the PP particles in the PS matrix, the effect being more pronounced with S‐B‐S triblock and S‐B‐S‐B‐S pentablock copolymers. The addition of these two BCs to the PS/PP blend also has the most pronounced effect on the improvement of mechanical properties of these blends. Hence, these two BCs can be assumed to be better compatibilizers for the PS/PP (4/1) blend than the S‐B diblock as well as both S‐B‐S‐B‐S‐B‐S and B‐S‐B‐S‐B‐S‐B heptablock copolymers. In both types of PS/PP/BC blends (5 or 10 wt % BC), the BC added was distributed between both the PS/PP interface and the PS phase, and, according to SAXS, it maintained a more or less ordered supermolecular structure of neat BCs. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 931–942, 2001 相似文献
156.
M. Sánchez‐Chaves M. Fernández‐García M. L. Cerrada 《Journal of Polymer Science.Polymer Physics》2007,45(9):1026-1036
The crystalline structure exhibited by terpolymers obtained through chemical modification with benzoyl chloride from an ethylene‐vinyl alcohol copolymer with a molar fraction in vinyl alcohol of 68%, EVOH68, has been studied by either wide angle X‐ray diffraction or small angle X ray scattering experiments and differential scanning calorimetry. The type of crystal lattice developed has been found to be strongly dependent on modification degree and thermal history. A highly‐disordered crystalline lattice with very small crystallites has been found for the quenched specimen with the highest benzoate content while the rest of fast cooled samples crystallized into an orthorhombic lattice. On the other hand, a monoclinic crystal cell has been observed in the slowly cooled specimens with low benzoate incorporation. At the last given thermal treatment, this monoclinic lattice evolves and seems to be transformed into an orthorhombic‐like crystal for the terpolymer with the highest modification ratio. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1026–1036, 2007 相似文献
157.
E. Nedkov 《European Polymer Journal》2004,40(11):2573-2582
Gamma irradiated isotactic polypropylene (IPP) has been studied by means of wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The skin layer has been investigated by WAXS reflection mode while the core layer underwent WAXS studies by transmission mode. β-IPP has been found solely in the skin layer. An increase in the β-phase has been observed as result of the irradiation. A phase transitions and decrease of crystallite sizes have been also observed. All of the parameters show a sharp change at a critical dose of 100 kGy. At this point the system parameters reverse. Radiation processes proceeding up to 100 kGy called radiation annealing are related to the improved crystallite perfection and thus emphasize the phase boundary. The processes provoke at higher radiation doses, up to 2000 kGy, damage in both crystal and amorphous lamellar parts. The values of the crystal and amorphous densities get closer and the process is similar to the partial radiation melting. 相似文献
158.
聚合物对硫化铅钠米微粒的稳定作用 总被引:6,自引:1,他引:6
以含铅聚合物微凝胶与H2S气体反应制得PbS纳米微粒/聚合物复合体系,利用小角X光散射方法对复合在聚合物中的PbS纳米微粒的粒度及分布进行了表征,研究了不同反应条件对其粒度及复合体系稳定性的影响。 相似文献
159.
C. A. Kawaguti S. H. Pulcinelli C. V. Santilli A. F. Craievich 《Journal of Sol-Gel Science and Technology》2006,37(3):213-217
The surface properties of SnO2 nanoparticles were modified by grafting ionic (Tiron®, (OH)2C6H2(SO3Na)2·H2O) or non-ionic (Catechol®, C6H4-1,2-(OH)2) capping molecules during aqueous sol-gel processing to improve the redispersibility of powdered xerogel. The effect of the amount of grafted organic molecules on the redispersibility of powders in aqueous solution at several basic pH values was studied. The nanostructural features of the colloidal suspensions were analyzed by small angle X-ray scattering (SAXS) measurements. Irrespective of the nature and amount of grafted molecules, complete redispersion was obtained in aqueous solution at pH = 13. The redispersion at pH = 11 results in a mixture of dispersed primary particles and aggregates. The proportion of well dispersed nanoparticles and aggregates (and their average size) can be tuned by the quantity of grafted ionic molecules. 相似文献
160.