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排序方式: 共有303条查询结果,搜索用时 15 毫秒
131.
Isao Ishigaki Akihiko Ito Tadashi Iwai Koichiro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(9):2511-2521
In order to investigate the effects of oxygen on the radiation-induced postpolymerization of trioxane in the solid state, a kinetic study has been made. Trioxane was purified by sublimation through Ag2O and Na-K alloy in vacuo and was irradiated and polymerized in the presence of rigorously dry oxygen. It was found that the initial rate of polymerization and the polymer yields are larger than those obtained in vacuo. By using the kinetic scheme proposed previously the results were analyzed kinetically. It was found that the influence of oxygen on the postpolymerization of trioxane is mainly attributable to the increase in the concentration of active species. The results obtained in dry air have been discussed in comparison with those in vacuo reported previously. 相似文献
132.
Takamasa Ishigaki Shigeru Yamauchi Junichiro Mizusaki Kazuo Fueki Hifumi Tamura 《Journal of solid state chemistry》1984,54(1):100-107
The tracer diffusion coefficient, , of oxide ions in LaCoO3 single crystal was determined over the temperature range of 700–1000°C by a gas-solid isotopic exchange technique using 18O tracer. For the determination, two methods, the gas phase analysis and the depth profile measurement, were employed. Under an oxygen pressure of 34 Torr, the temperature dependence of in LaCoO3 was expressed by at 950°C was found to be proportional to P?0.35O2. The diffusion of oxide ions occurs through a vacancy mechanism. The activation energy for the migration of oxide ion vacancies was estimated as 18 kcal · mole?1. 相似文献
133.
M. Takehisa H. Shintani M. Sekiguchi T. Koshikawa T. Oonishi M. Tsuge K. Sou Y. Yamase S. Kinoshita H. Tsukamoto T. Endo K. Yashima M. Nagai K. Ishigaki Y. Sato J. L. Whitby 《Radiation Physics and Chemistry》1998,52(1-6):21-27
An extensive study of the radiation resistance of microbial species constituting the bioburden of a number of different medical devices obtained from Japanese medical device manufacturers has been carried out. A standard protocol for determining radiation resistance was used and validated at the fourteen centres involved in the study. Individual microbial isolates from the bioburden obtained from seven different devices manufactured in these centres were studied. A total of 3742 unselected isolates were obtained, of which 197 failed to survive long enough for subsequent radiation resistance studies. The remainder were subjected to an initial screen test to identify those organisms that were sensitive to the lethal effects of radiation with a D10 of < 1.5kGy. The 465 isolates that survived the screen doses were then tested for survival in an incremental series of radiation doses using methods similar to those of Whitby (1979) and Yan and Tallentire(1995). The isolates from “dry” devices were more resistant than those obtained from the one water filled (“wet”) device studied. The overall distribution of radiation resistance among the isolates was considered to be similar to that forming the “Standard Distribution of Resistance” (SDR) included in the ISO International Standard 11137 “Sterilization of Health Care Products — Requirements for validation and routine control — Radiation sterilization”. 相似文献
134.
Tokio Hagiwara Takamasa Shimizu Tomonori Uda Hiroshi Hamana Tadashi Narita 《Journal of polymer science. Part A, Polymer chemistry》1990,28(1):185-192
The kinetic feature of the anionic polymerization of N-PMI was investigated in THF. The polymerization system initiated with lithium tert-butoxide was revealed to be so-called “slow-initiation” system. The rate constant of the initiation reaction, ki, was obtained to be 4.2 × 10?3 (L mol?1 s?1) at ?72°C. The apparent rate constants of the propagation reaction, k, at ?72°C were individually obtained from each slope of the first-order plots in the later stages of the polymerizations for four different initiator concentrations. Each k is fairly close to that of initiation rate around 10?3. The propagation reaction was concluded to be dominated by ion-pair mechanism from the analysis of the kinetic data and the results of the addition effects of crown ether and common salt. 相似文献
135.
Dr. Hiroyuki Kamata Dr. Keiichiro Kushiro Prof. Madoka Takai Prof. Ung‐il Chung Prof. Takamasa Sakai 《Angewandte Chemie (International ed. in English)》2016,55(32):9282-9286
Hydrogels are promising materials for biomedical applications, where timely degradation is often preferred. In the conventional design, however, the cleavage of polymer networks essentially causes considerable morphological changes (i.e., degradation‐induced swelling), triggering various medical complications. Herein, we report a rational strategy to suppress the degradation‐induced swelling based on the synthetic control of the polymer–solvent interaction parameter (χ) of constituent polymer networks. The resultant hydrogels with an optimal χ parameter (χ37 °C≈0.53; non‐osmostic hydrogels) displayed the capability to retain their original shape and degrade without generating significant swelling pressure under physiological conditions (Π37 °C<1 kPa). This concept of the safely degradable non‐osmotic hydrogel is theoretically universal, and can be exploited for other types of synthetic hydrogels in various settings. 相似文献
136.
Heteroleptic [Bis(oxazoline)](dipyrrinato)zinc(II) Complexes: Bright and Circularly Polarized Luminescence from an Originally Achiral Dipyrrinato Ligand
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Dr. Julius F. Kögel Dr. Shinpei Kusaka Dr. Ryota Sakamoto Toshiki Iwashima Mizuho Tsuchiya Ryojun Toyoda Ryota Matsuoka Dr. Takamasa Tsukamoto Dr. Junpei Yuasa Prof. Dr. Yasutaka Kitagawa Prof. Dr. Tsuyoshi Kawai Prof. Dr. Hiroshi Nishihara 《Angewandte Chemie (International ed. in English)》2016,55(4):1377-1381
Heteroleptic zinc(II) complexes synthesized using achiral dipyrrinato and chiral bis(oxazoline) ligands show bright fluorescence with quantum efficiencies of up to 0.70. The fluorescence originates from the 1π–π* photoexcited state localized exclusively on the dipyrrinato ligand. Furthermore, the luminescence is circularly polarized despite the achirality of the dipyrrinato ligand. Single‐crystal X‐ray structure analysis discloses that the chiral bis(oxazoline) ligand undergoes intramolecular π–π stacking with the dipyrrinato ligand, inducing axial chirality in the dipyrrinato moiety. 相似文献
137.
138.
139.
Hara Y Sakai T Maeda S Hashimoto S Yoshida R 《The journal of physical chemistry. B》2005,109(49):23316-23319
A new type of self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky reaction. In this study, capture sites with a positive charge for an oxidizing agent as a counterion were incorporated into the copolymer of N-isopropylacrylamide and the ruthenium complex as a catalyst. Soluble-insoluble self-oscillation of the polymer was first achieved without adding an oxidizing agent. The effect of temperature on the self-oscillating behavior was investigated. It was clarified that the polymer had two advantageous characteristics because of the higher LCST; one is to enable self-oscillation around body temperature, and the other is to cause the oscillation for a longer time without intermolecular aggregation among the polymer chains in the reduced state. This achievement of self-oscillation of polymer chains including an oxidizing agent may lead to their practical use under oxidant-free conditions. 相似文献
140.
Hashimoto N Ninomiya K Endo T Sisido M 《Chemical communications (Cambridge, England)》2005,(34):4321-4323
A simple and quick method for direct aminoacylation of a tRNA with a non-natural amino acid was developed by using an N-protected amino acid cyanomethyl ester as a substrate solubilized in CTACl micelle under ultrasonic agitation. 相似文献