全文获取类型
收费全文 | 346篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
化学 | 270篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 22篇 |
物理学 | 53篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 29篇 |
2012年 | 41篇 |
2011年 | 34篇 |
2010年 | 22篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有363条查询结果,搜索用时 15 毫秒
81.
82.
Zoghi Ali T. Shokouhi Mohammad Naderi Fahimeh Abbasghorbani Maryam Fatehi Azita Pouladi Babak Adhami Mohammad Amin 《Journal of solution chemistry》2022,51(1):84-96
Journal of Solution Chemistry - Hydrogen sulfide and carbonyl sulfide represent undesirable impurities in a variety of industrial gas streams such as natural gas, liquefied natural gas and... 相似文献
83.
Let G be a group. If every nontrivial subgroup of G has a proper supplement, then G is called an aS-group. We study some properties of aS-groups. For instance, it is shown that a nilpotent group G is an aS-group if and only if G is a subdirect product of cyclic groups of prime orders. We prove that if G is an aS-group which satisfies the descending chain condition on subgroups, then G is finite. Among other results, we characterize all abelian groups for which every nontrivial quotient group is an aS-group. Finally, it is shown that if G is an aS-group and |G| ≠ pq, p, where p and q are primes, then G has a triple factorization. 相似文献
84.
Yan J Garzan A Narayan RS Vasileiou C Borhan B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13749-13756
In an attempt to revise the structural assignment of mucoxin, and faced with 64 diastereomeric possibilities, we resorted to the synthesis of truncated structures that contained the core stereochemical sites. Twelve stereochemical analogues were synthesized, their (1)H and (13)C NMR spectra were analyzed and four recurring stereochemical trends were distilled from the data. Applying the observed trends to the diastereomeric population pared the possible choices for the correct structure of mucoxin from 64 to 4. Synthesis of these analogues led to the identification of the correct structure of mucoxin. 相似文献
85.
[reaction: see text] A new concept of simultaneous covalent anchoring of a N-heterocyclic carbene palladium/ionic liquid matrix on the silica surface and the application of the resulting catalyst in the Heck reaction of a variety of different haloarenes is described. The catalyst shows high thermal stability (up to 280 degrees C) and could be recovered and reused for four reaction cycles, giving a total TON congruent with 36 600. Furthermore, TEM coupled with EDX analysis indicate the formation of Pd nanoparticles within the immobilized IL layer. 相似文献
86.
Summary: In this work, a surface re-modified multi-walled carbon nanotube (MWNT) was prepared by the chemical attachment of oligomeric unsaturated polyester on the MWNT surface. The re-modified MWNT was incorporated in two concentrations of 0.35 and 0.70 Wt.% into epoxy resin in order to investigate its effect on morphology and mechanical behavior of the MWNT/epoxy nanocomposite. The transmission electron microscopy showed that the re-modification of MWNT surface improves its dispersion state in the epoxy matrix. The tensile measurements for the nanocomposite having different amounts of surface re-modified/not-modified MWNT showed that the fracture mechanism changed from brittle to tough beyond a certain amount of surface re-modified MWNT. The scanning electron microscopy findings on the fracture surface morphology of the resulted nanocomposite substantiated the observed phenomena. 相似文献
87.
The rate constant of alkaline fading of malachite green (MG+) was studied in alcohol–water binary mixtures. This reaction was studied under pseudo‐first‐order conditions at 283–303 K. It was observed that the reaction rate constants were increased in the presence of different weight percentages of methanol, ethanol, 1‐propanol, 2‐propanol, ethylene glycol, 1,2‐propanediol, and glycerol (up to 19.3%). In aqueous glycerol solutions higher than 19.3%, the rate constant of reaction slightly decreases, which is due to high viscosity values of solvent mixtures. The fundamental rate constants of MG+ fading in these solutions were obtained by using the SESMORTAC model. Owing to the charged character of activated complex, with an increase in the weight percentage of the used cosolvents or temperature, k2 values change according to the trend of hydroxide ion nucleophilic parameter values. Also, using MG+ solvatochromism, a simple test, called MAGUS, is introduced for measuring the glycerol concentration in its aqueous solutions. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 508–518, 2010 相似文献
88.
A simple, efficient, and general method has been developed for the one-pot synthesis of α-aminophosphonic esters in water using β-cyclodextrin as an efficient catalyst. α-Aminophosphonic esters were obtained in good yields (45-82%) and purity under mild conditions by the reaction of diethyl phosphite with a mixture of aldehyde and amine in water at reflux. 相似文献
89.
<正>An efficient and mild method for the direct conversion of alcohols into N-alkylphthalimides using 2,4,6-trichloro-1,3,5-triazine and dimethylformamide was described.The reaction was preceded via(alcoxymethylene) dimethylammonium chloride intermediate and produced corresponding N-alkylphthalimides in good-to-excellent yields. 相似文献
90.
A high speed, selective, and robust capillary electrophoresis (CE) method with high capacity was developed and validated for determination of assay of 1,4-dideoxy-1,4-imino-D-arabinitol in active pharmaceutical ingredients, solutions, and tablets during the development work at preclinical and Phase I and II clinical studies. 1,4-Dideoxy-1,4-imino-D-arabinitol, tartrate has (almost) no UV absorption. Therefore, the developed CE method for quantification was based on indirect UV detection. A cation CE principle was chosen using an electrolyte at pH 4.0 containing dimethyldiphenylphosphonium hydroxide, which has a strong UV absorbance. The quantification was performed using internal standard technique, by which piperidine was used as internal standard. The method was validated. The validation results showed that the CE method was suitable for the assay (and dissolution) analysis. 相似文献