全文获取类型
收费全文 | 1237篇 |
免费 | 51篇 |
国内免费 | 6篇 |
专业分类
化学 | 1027篇 |
晶体学 | 8篇 |
力学 | 20篇 |
数学 | 66篇 |
物理学 | 173篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 21篇 |
2019年 | 21篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 37篇 |
2015年 | 30篇 |
2014年 | 35篇 |
2013年 | 65篇 |
2012年 | 74篇 |
2011年 | 91篇 |
2010年 | 45篇 |
2009年 | 44篇 |
2008年 | 81篇 |
2007年 | 96篇 |
2006年 | 91篇 |
2005年 | 76篇 |
2004年 | 69篇 |
2003年 | 60篇 |
2002年 | 50篇 |
2001年 | 25篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 8篇 |
排序方式: 共有1294条查询结果,搜索用时 15 毫秒
61.
Ken-Ichi Kanno Yuichi Kobayashi Shin-Ichiro Nishimura Hiroyoshi Kuzuhara Kenichi Hatanaka 《Journal of carbohydrate chemistry》2013,32(4-5):481-490
Abstract 1,6-Anhydro-2-deoxy-3,4-di-O-benzyl-2-phthalimido-β-d- glucopyranose (5) was synthesized from 1,6-anhydro-β-d-mannopyranose (1) in five steps. Compound 5 was polymerized under cationic conditions and selectively yielded glucosamine oligomers (degree of polymerization 5-7). Copolymerization of 5 with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose indicated the low reactivity of 5 with the active cation derived from 5. Deprotection of 2-deoxy-3,4-di-O-benzyl-2-phthalimido-(1→6)-β-d-glucopyranan (7) and N-acetylation gave 2-acetamido-2-deoxy-(1→6)-β-d-glucopyranan (9). 相似文献
62.
Tetsuya Kajimoto Yuichi Ishioka Takahiro Katoh 《Journal of carbohydrate chemistry》2013,32(8-9):469-495
p‐Dodecylbenzenethiol (1) and p‐octyloxybenzenethiol (2) were synthesized as new odorless benzenethiols. Moreover, preparation of novel 1‐thioglycosides using 1 and 2 as well as their application for glycosylation reactions was performed. As a result, it was found that these 1‐thio‐glycosides were excellent glycosyl donors, and especially 2‐thio‐sialoside prepared from 1 and 2 afforded the best result to date in terms of α‐ and β‐selectivity in the sialylation where only the single C‐3 hydroxyl group of acceptor D‐galactopyranoside was free. All procedures from the preparation of thioglycosides to glycosylation reaction were attainable under completely odorless conditions. 相似文献
63.
Development of highly functional cesium selective adsorbents for the decontamination of high-activity-level water(HALW) from the Fukushima NPP-1 accident is very urgent. In order to selectively adsorb the radioactive cesium, three kinds of novel porous silica gels loaded with insoluble ferrocyanides(SLFC) were prepared using a successive impregnation/precipitation method. Based on the results of previous research, the SLFC composites have relatively large uptake ratio above 95%, distribution coefficients(Kd) above 103 cm3/g, and excellent adsorption kinetics even in seawater. The solidification results also indicate that zeolites have an excellent Cs immobilization characteristic, gas-trapping and self-sintering abilities, and low leachability. We chose three kinds of SLFC composites to achieve the optimization of solidification by mixing with nine kinds of additives at high temperatures(up to 1200 °C). The Cs contents in the three composites were estimated to be below 30% of the initial contents and decreased with the three stages at calcination temperatures ranging from 25 to 1200 °C. By contrast, the Cs immobilization ratio was markedly lowered by mixing with additives: of those, allophane had the best immobilization result. By increasing the additive ratio to 50 wt%, the Cs immobilization ratio became almost 100% and no volatilization of Cs was detected even after calcination at 1200 °C. This result indicates that calcination of the mixture of SLFC composites after adsorbing Cs+ ions and specific additives under appropriate ratio is effective for stable solidification. 相似文献
64.
Jinhua Hong Shunsuke Kobayashi Akihide Kuwabara Yumi H. Ikuhara Yasuyuki Fujiwara Yuichi Ikuhara 《Molecules (Basel, Switzerland)》2021,26(12)
Solid electrolytes, such as perovskite Li3xLa2/1−xTiO3, LixLa(1−x)/3NbO3 and garnet Li7La3Zr2O12 ceramic oxides, have attracted extensive attention in lithium-ion battery research due to their good chemical stability and the improvability of their ionic conductivity with great potential in solid electrolyte battery applications. These solid oxides eliminate safety issues and cycling instability, which are common challenges in the current commercial lithium-ion batteries based on organic liquid electrolytes. However, in practical applications, structural disorders such as point defects and grain boundaries play a dominating role in the ionic transport of these solid electrolytes, where defect engineering to tailor or improve the ionic conductive property is still seldom reported. Here, we demonstrate a defect engineering approach to alter the ionic conductive channels in LixLa(1−x)/3NbO3 (x = 0.1~0.13) electrolytes based on the rearrangements of La sites through a quenching process. The changes in the occupancy and interstitial defects of La ions lead to anisotropic modulation of ionic conductivity with the increase in quenching temperatures. Our trial in this work on the defect engineering of quenched electrolytes will offer opportunities to optimize ionic conductivity and benefit the solid electrolyte battery applications. 相似文献
65.
Spatiotemporal pattern formation in a product-activated enzymic reaction at high enzyme concentrations is investigated. Stochastic simulations show that catalytic turnover cycles of individual enzymes can become coherent and that complex wave patterns of molecular synchronization can develop. The analysis based on the mean-field approximation indicates that the observed patterns result from the presence of Hopf and wave bifurcations in the considered system. 相似文献
66.
Yang K Chen LP Cai YQ Hiraoka N Li S Zhao JF Shen DW Song HF Tian H Bai LH Chen ZH Shuai ZG Feng DL 《Physical review letters》2007,98(3):036404
Excitons in a complex organic molecular crystal were studied by inelastic x-ray scattering (IXS) for the first time. The dynamic dielectric response function is measured over a large momentum transfer region, from which an exciton dispersion of 130 meV is observed. Semiempirical quantum chemical calculations reproduce well the momentum dependence of the measured dynamic dielectric responses, and thus unambiguously indicate that the lowest Frenkel exciton is confined within a fraction of the complex molecule. Our results demonstrate that IXS is a powerful tool for studying excitons in complex organic molecular systems. Besides the energy position, the IXS spectra provide a stringent test on the validity of the theoretically calculated exciton wave functions. 相似文献
67.
Shimoda K Tobu Y Shimoikeda Y Nemoto T Saito K 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,186(1):156-159
We here show the (43)Ca 5QMAS NMR spectra at high field (16.4 T) and the first 7QMAS spectrum at ultra-high field (21.8 T) for geologically important Ca-containing glasses. The high-resolution MQMAS spectra present a clear evidence of multiple Ca sites in the amorphous structures that have never been identified by other analytical methods. The present study suggests that the Ca(2+) ions are mainly in 7- and 8-fold coordination sites. This will offer valuable insights for dynamic properties of magmatic liquids. The MQMAS NMR technique at high magnetic field is a unique tool to understand the detailed structural information on a specific element in solids including organic and inorganic compounds. 相似文献
68.
Lee Chuin Chen Md. Matiur Rahman Kenzo Hiraoka 《Journal of the American Society for Mass Spectrometry》2014,25(11):1862-1869
The heating of electrospray ion source under atmospheric pressure is limited to the normal boiling point of the solution. The boiling takes place when the vapor pressure of the liquid at a given temperature equals the ambient pressure. By using a high pressure ESI source, which has been developed previously in our laboratory, a stable electrospray ionization of super-heated aqueous solution is performed up to a solution temperature of 180°C. The ion source is pressurized with pure nitrogen to a maximum pressure of 11 atm, and it is coupled to a commercial mass spectrometer via a custom-made ion transport capillary. A booster pump with variable pumping speed is added to the pumping system to regulate the pressure in the first pumping stage at 1?~?1.3 Torr. High pressure mass spectrometry is performed on several peptides and proteins to demonstrate its application in the temperature-controlled thermally induced denaturation and dissociation. Graphical Abstract
? 相似文献
69.
Development of a New Benzylating Reagent Spontaneously Releasing Benzyl Cation Equivalents at Room Temperature
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Kohei Yamada Yuichi Tsukada Yukiko Karuo Dr. Masanori Kitamura Prof. Dr. Munetaka Kunishima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12274-12278
A new O‐benzylating reagent, that is, 4‐(4,6‐diphenoxy‐1,3,5‐triazin‐2‐yl)‐4‐benzylmorpholinium trifluoromethanesulfonate (DPT‐BM), has been developed. Benzyl cation equivalents are generated from DPT‐BM by dissolving the compound in a solvent at room temperature under non‐acidic conditions. The benzylation of various alcohols by using a combination of DPT‐BM and magnesium oxide provided the benzyl ethers in good yields. 相似文献
70.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献