全文获取类型
收费全文 | 225篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 148篇 |
晶体学 | 1篇 |
力学 | 15篇 |
数学 | 49篇 |
物理学 | 20篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 13篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有233条查询结果,搜索用时 15 毫秒
31.
A Sc complex of (4S,5S)-diphenyl PYBOX 1 was found to serve as a catalyst for the asymmetric conjugate addition reactions between various thiols and 3-crotonoyl-2-oxazolidinone, affording the corresponding adducts in good yields and high enantioselectivies (up to 92% ee). A new improved method for making (4S,5S)-diphenyl PYBOX is presented. 相似文献
32.
Chifei Wu Tada‐Aki Yamagishi Yoshiaki Nakamoto Shin‐Ichiro Ishida Saburo Kubota Koh‐Hei Nitta 《Journal of Polymer Science.Polymer Physics》2000,38(11):1496-1503
The viscoelastic properties and stabilities of those properties of organic hybrids consisting of chlorinated polyethylene (CPE) and tetrakis[methylene‐3‐(3‐5‐di‐tert‐butyl‐4‐hydroxy phenyl)propionyloxy]methane (AO‐60) and triethylene glycol bis[3‐(3‐tert‐butyl‐4‐hydroxy‐5‐methyl phenyl)propionyloxy] (AO‐70) were investigated. The CPE/AO‐70 hybrids show only one transition, whereas for the CPE/AO‐60 hybrids, one novel relaxation appears above the glass‐transition temperature of CPE. This relaxation on the higher temperature side in the mechanical spectrum for CPE/AO‐60 is associated with the appearance of the AO‐60‐rich phase. Furthermore, the stabilities of the viscoelastic properties and microstructures of the organic hybrids consisting of CPE and multifunctional hindered phenols are dominated by the strength of the intermolecular interaction between CPE and phenols and the conformations of the middle skeletal parts of hindered phenols. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1496–1503, 2000 相似文献
33.
34.
Aki H. Niiya T. Iwase Y. Goto M. Kimura T. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):423-435
The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated
by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of
AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution.
In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry:
the first-type had a high association constant K
1 of 4.0-8.0·103 M-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K
2 of 1.0·103 M-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in
a two-step reaction and was characterized by a smaller K
1:2of 4.0·102 M-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of
AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in
the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37°C. In weak acid and neutral
solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl
group was included (Mode II). AMPC was very stable in these solutions (t
1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed
AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC
in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
35.
Hajime Ohtani Aki Suzuki Shin Tsuge 《Journal of polymer science. Part A, Polymer chemistry》2000,38(10):1880-1888
The end groups of styrene–methyl methacrylate (St‐MMA) copolymers polymerized radically with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator, which are difficult to characterize even by NMR, were investigated by pyrolysis–gas chromatography. On the resulting pyrograms, characteristic products that formed from the end‐group moiety due to AIBN, such as 2‐cyanopropane, 2‐cyanopropen, and various compounds consisting of an isobutyronitrile group and a monomer unit, were observed together with those from the main chain, such as St and MMA monomers and various dimeric and trimeric products. The relative abundance between the recombination and disproportionation termination reactions in the copolymerization process was estimated from the relative intensities between the characteristic peaks of the end group and those of the main chain. Thus, the estimated abundance for the termination reactions suggested that the polymerization process for this particular copolymer system terminated preferentially by recombination rather than by disproportionation. Furthermore, the relative abundance between the monomer units adjacent to the chain‐end AIBN residues was estimated on the basis of the peak intensities of the products consisting of an isobutyronitrile group and either monomer unit, which reflected the penultimate neighboring structure of the end group in the polymer chain. Thus, the observed results suggested that the isobutyronitrile radical formed by the dissociation of AIBN in the initiation reaction was predominantly adjoined by St monomer rather than by MMA monomer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1880–1888, 2000 相似文献
36.
37.
38.
Henrik Ebel Marko K. Matikainen Vesa-Ville Hurskainen Aki Mikkola 《Nonlinear dynamics》2017,88(2):1075-1091
This study thoroughly examines various higher-order three and four-node beam elements for use in the absolute nodal coordinate formulation (ANCF). The paper carefully investigates which potential benefits and drawbacks the utilization of higher-order ANCF beam elements without in-slope vectors has in the case of the usage of full three-dimensional elasticity. When the elastic forces for shear-deformable ANCF beam elements are calculated using full three-dimensional elasticity—especially in the form of the St. Venant–Kirchhoff material law—Poisson locking severely deteriorates the accuracy of the numeric results. As shown in this paper, an existing approach to preventing this locking phenomenon for three-node beam elements can still produce unsatisfying results in load cases involving bidirectional bending. The results of this study show that enriching the polynomial basis used to approximate the beam kinematics provides a natural solution to this issue. As will be seen, these findings for three-node elements can also be extended to four-node elements. When using a sufficient approximation order in transverse directions, satisfying accuracy can be achieved both in conventional one-dimensional bending and in the above-mentioned bidirectional load case. 相似文献
39.
Yuki?KanazawaEmail authorView authors OrcID profile Tetsuya?Yamada Aki?Kido Koji?Fujimoto Kyoko?Takakura Hiroaki?Hayashi Yasutaka?Fushimi Satoshi?Kozawa Koji?Koizumi Makiko?Okuni Naomi?Ueda Kaori?Togashi 《Applied magnetic resonance》2017,48(2):125-134
To visualize the condition of impregnation of polyethylene glycol (PEG) in waterlogged wood, we demonstrated magnetic transfer (MT) magnetic resonance imaging (MRI) through a series of process of PEG impregnation. Three different samples were examined; reference wood, 10 cm cut wood, and 5 cm cut wood. During this study, the upper section sample was kept immersed in water, for the middle and lower sections the concentration of PEG solution was changed at 20 wt% intervals from 20 to 100 wt%. The impregnated periods of each PEG solution concentration were 14 days. Then, MR imaging were performed with/without MT pulse. The MTR value for both 10 cm- and 5 cm-samples were shown to decrease at 20 wt% PEG at peak concentration. When the sample volume was large, e.g., 10 cm-sample, the MTR value decreased to 100 wt% PEG concentration. In contrast, when a sample volume was small, e.g., 5 cm-sample, MTR value decreased to 60 wt% PEG concentration. In conclusion, MTR analysis makes it possible to nondestructively visualize and evaluate the inner condition concerning the PEG impregnation method for waterlogged wood. 相似文献
40.
Recently, the Voice Handicap Index (VHI), developed in the United States, has been highlighted as a means to assess a patient's perceptions of the severity of his or her voice disorder. The VHI is based on a self-administered questionnaire that quantifies the degree of a patient's disability related to his/her voice disorder. The questionnaire was translated into Japanese and applied to Japanese patients with various kinds of disordered voice or dysphonia. The results were analyzed and the usefulness discussed. In this study, 546 patients (281 males and 265 females) were included. Mean VHI scores were 36.2/120 in males and 44.1/120 in females. In the male patients, VHI scores were the highest among teens. However, VHI scores did not vary with age in the female patients. Patients with vocal fold paralysis, functional dysphonia, psychological dysphonia, and spasmodic dysphonia showed relatively high VHI scores, whereas those with laryngeal granuloma and laryngopharyngeal reflux disease showed low scores. In most diseases, functional and physiological scores were higher than emotional scores. In any treated patients, those with vocal nodule, vocal polyp, polypoid vocal fold, and recurrent laryngeal nerve paralysis, VHI scores decreased after therapeutic intervention. These findings suggest that the Japanese VHI is a useful tool for monitoring a patient's psychological status, choosing appropriate treatment, and assessing the therapeutic outcome. 相似文献