全文获取类型
收费全文 | 360篇 |
免费 | 19篇 |
专业分类
化学 | 257篇 |
晶体学 | 2篇 |
力学 | 12篇 |
数学 | 31篇 |
物理学 | 77篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2019年 | 10篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 23篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 29篇 |
2007年 | 22篇 |
2006年 | 15篇 |
2005年 | 27篇 |
2004年 | 12篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1964年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有379条查询结果,搜索用时 15 毫秒
111.
Teshima K Kondo T Maeda C Oda T Hagimoto T Tsukuda R Yoshimura Y 《Journal of mass spectrometry : JMS》2002,37(6):631-638
We investigated the application of alkylamines, as additives to the mobile phase, to a quantification method for the metabolites, M-III and M-IV, of TAK-778, which is a new bone anabolic agent, in human serum using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Prior to setting up the analytical method, we found that 1-alkylamines co-existing with M-III and M-IV in the turbo ionsprayed solution formed 1-alkylammonium adduct molecules of these metabolites during the ionization process, and the abundance of the adduct ions was considerably higher than that of protonated molecules ([M + H](+)s) of these metabolites. Based on these findings, we investigated a variety of 1-alkylamines and their spiked concentrations in the mobile phase for LC/MS/MS analysis to obtain higher sensitivities for the quantification of these metabolites. After these examinations, we found that 1-hexylamine at a final concentration of 0.05 mmol l(-1) was the most suitable additive for the mobile phase, and set the selected reaction monitoring (SRM) ions for the 1-hexylammonium adduct molecule and [M + H](+), allowing about a fivefold gain in the SRM chromatographic peak compared with that without 1-hexylamine. The adduct ion was considered to be formed by interaction between the amino group of 1-hexylamine and the phosphoryl group of M-III and M-IV. The internal standard (I.S.) used was deuterated M-III for each metabolite. The analytes and I.S. were extracted with diethyl ether from serum samples at neutral pH and injected into the LC/MS/MS system with a turbo ionspray interface. The limit of quantification for both analytes was 0.5 ng ml(-1) when 0.1 ml of serum was used, and the calibration curves were linear in the range 0.5-100 ng ml(-1). The method was precise; the intra- and inter-day precisions of the method were not more than 5.6%. The accuracy of the method was good, with deviations between added and calculated concentrations of M-III and M-IV being typically within 16.6%. This method provided reliable pharmacokinetic data for M-III and M-IV after the intramuscular administration of TAK-778 sustained-release formulation in humans. 相似文献
112.
Kuniyasu Masataka Aoyagi Yusuke Unno Noriyuki Satake Shin-ichi Yuki Kazuhisa Seki Yohji 《Optical Review》2016,23(3):529-534
Optical Review - A basic heat transfer promoter such as packed beds of spheres is one of the technologies of the promotion of heat transfer using the turbulent mixture. We carried out 3-D... 相似文献
113.
Ryuhei Ikeda Prof. Ryoichi Kuwano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8610-8618
The iridium catalyst [IrCl(cod)]2–phosphine–I2 (cod=1,5‐cyclooctadiene) selectively reduced isoxazolium triflates to isoxazolines or isoxazolidines in the presence of H2. The iridium‐catalyzed hydrogenation proceeded in high‐to‐good enantioselectivity when an optically active phosphine–oxazoline ligand was used. The 3‐substituted 5‐arylisoxazolium salts were transformed into 4‐isoxazolines with up to 95:5 enantiomeric ratio (e.r.). Chiral cis‐isoxazolidines were obtained in up to 89:11 e.r., with no formation of their trans isomers, when the substrates had a primary alkyl substituent at the 5‐position. The mechanistic studies indicate that the hydridoiridium(III) species prefers to deliver its hydride to the C5 atom of the isoxazole ring. The hydride attack leads to the formation of the chiral isoxazolidine via a 3‐isoxazoline intermediate. Meanwhile, in the selective formation of 4‐isoxazolines, hydride attack at the C5 atom may be obstructed by steric hindrance from the 5‐aryl substituent. 相似文献
114.
Ryoichi Kishi Kazuaki Hiroki Taiki Tominaga Ken‐Ichi Sano Hidenori Okuzaki Jose G. Martinez Toribio F. Otero Yoshihito Osada 《Journal of Polymer Science.Polymer Physics》2012,50(11):790-796
Novel electro‐conductive and mechanically‐tough double network polymer hydrogels (E‐DN gels) were synthesized by polymerization of 3, 4‐ethylenedioxythiophene in the presence of a double network hydrogel (DN gel) matrix. The E‐DN gels showed not only excellent mechanical performance, having a fracture stress of 1.4–2.1 MPa, but also electrical conductivity as high as 10?3 S cm?1, both under dry and water‐swollen states. The fracture stress and fracture energy of the E‐DN gel was increased by 1.7 and 3.4 times, respectively, as compared with the DN gel. From scanning electron microscope and AFM observations, it was found that electro‐conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) was incorporated into DN gel matrix, apparently due to the formation of a poly‐ion complex with sulfonic acid group of the DN gel network. Thus, PEDOT incorporated into the DN gel matrix greatly improves not only electronic conductivity, but also mechanical properties, reinforcing the double network gel matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 相似文献
115.
116.
Ishimatsu R Izadyar A Kabagambe B Kim Y Kim J Amemiya S 《Journal of the American Chemical Society》2011,133(40):16300-16308
Here, we report on the first electrochemical study that reveals the kinetics and molecular level mechanism of heterogeneous ion-ionophore recognition at plasticized polymer membrane/water interfaces. The new kinetic data provide greater understanding of this important ion-transfer (IT) process, which determines various dynamic characteristics of the current technologies that enable highly selective ion sensing and separation. The theoretical assessment of the reliable voltammetric data confirms that the dynamics of the ionophore-facilitated IT follows the one-step electrochemical (E) mechanism controlled by ion-ionophore complexation at the very interface in contrast to the thermodynamically equivalent two-step electrochemical-chemical (EC) mechanism based on the simple transfer of an aqueous ion followed by its complexation in the bulk membrane. Specifically, cyclic voltammograms of Ag(+), K(+), Ca(2+), Ba(2+), and Pb(2+) transfers facilitated by highly selective ionophores are measured and analyzed numerically using the E mechanism to obtain standard IT rate constants in the range of 10(-2) to 10(-3) cm/s at both plasticized poly(vinyl chloride) membrane/water and 1,2-dichloroethane/water interfaces. We demonstrate that these strongly facilitated IT processes are too fast to be ascribed to the EC mechanism. Moreover, the little effect of the viscosity of nonaqueous media on the IT kinetics excludes the EC mechanism, where the kinetics of simple IT is viscosity-dependent. Finally, we employ molecular level models for the E mechanism to propose three-dimensional ion-ionophore complexation at the two-dimensional interface as the unique kinetic requirement for the thermodynamically facilitated IT. 相似文献
117.
Park Jae-Hyeok Hagio Takeshi Kamimoto Yuki Ichino Ryoichi 《Journal of Solid State Electrochemistry》2021,25(6):1901-1913
Journal of Solid State Electrochemistry - As a new trial to improve the corrosion resistance of the Fe-W alloy platings, Fe-W alloys incorporating a small amount of Zn, namely novel ternary Fe-W-Zn... 相似文献
118.
Hexasilsesquioxanes bearing bulky Tip (2,4,6-triisopropylphenyl) groups were synthesized and the structure was determined. The X-ray crystal analysis revealed that the enantiomer pair originating from the restricted rotation of the bulky Tip groups was included in the single lattice. In solution, evidence for the rapid interconversion of both enantiomers was encountered in 1H NMR. Thus, variable temperature NMR indicated peak broadeningupon warming the sample, with a coalescence temperature of 38 ° C. Kinetic parameters of the rotation were also calculated. 相似文献
119.
Hiroshi Hachisako Tetsuya Yamazaki Ryoichi Murakami Kimiho Yamada 《Liquid crystals》1993,15(5):723-727
Steric selectivity in terms of molecular planarity of cationic dyes was investigated using anionic bilayer aggregates. Planar cationic dye (para-type stilbazolium) could be incorporated into the hydrophobic region of anionic crystalline bilayer aggregates, whereas structurally related, less planar dyes (ortho-type stilbazolium) could not be incorporated in spite of somewhat higher hydrophobicity resulting from lengthening of the N-alkyl group. 相似文献
120.
We have developed a new method to fabricate periodic waveguide structures used for quasi-phase-matched second-harmonic generation, where nonlinear optical organic crystals and fluorinated copolyimides are alternately arranged. Quasi-phase-matched second-harmonic generation from an organic waveguide device has been demonstrated. 相似文献