首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   76篇
  免费   2篇
化学   65篇
数学   7篇
物理学   6篇
  2021年   4篇
  2020年   3篇
  2019年   2篇
  2018年   2篇
  2017年   3篇
  2016年   3篇
  2015年   3篇
  2014年   1篇
  2013年   5篇
  2012年   3篇
  2011年   3篇
  2010年   2篇
  2008年   2篇
  2007年   2篇
  2006年   3篇
  2005年   3篇
  2004年   5篇
  2003年   4篇
  2002年   5篇
  2001年   2篇
  1999年   1篇
  1998年   3篇
  1996年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1985年   3篇
  1982年   1篇
  1975年   1篇
排序方式: 共有78条查询结果,搜索用时 46 毫秒
11.
We construct biorthogonal bases of spaces of an n-separate multiresolution analysis and wavelets for n scaling functions. Fast algorithms are presented for finding the coefficients of expansions of functions in such bases.  相似文献   
12.
Solar radiations trigger the physiological alteration in skin which progress toward photoaging. Sunscreens are known to be effective against the photodamaging effects of sunlight. The purpose of this study was to evaluate the extent to which aging signs caused by real‐life sunlight exposure could be avoided by comparing various parameters between sun‐exposed and sun‐protected skin using noninvasive probes. Female volunteers (n = 11) after getting their consent were provided with marketed sunscreen product to apply onto their skin for 6 months. Measurements were scheduled every 15 days from the baseline reading for 6 months. Cutometer, Mexameter and Corneometer were used for evaluation of facial skin parameters. Clinical evaluations showed the effects of sunlight exposure on different skin parameters by comparing sun‐protected and unprotected skin, where Gross elasticity (R2), Net elasticity (R5), Viscoelasticity (R6) and Biological elasticity (R7) showed insignificant results, while Hydration, Melanin and Erythema showed significant results. Sun‐exposed skin presented 0.72%, 0.66%, 0.77%, 1.39%, 1.99%, 2.01% and 3.15% changes in R2, R5, R6 and R7, melanin, erythema and hydration, respectively, which were potentially prevented by sunscreen application. Premature aging is inhibited by following photoprotective regimen on routine basis, emphasizing the potential benefit of sunscreen against early aging signs.  相似文献   
13.
Synthetic polymers represent a modifiable class of materials that can serve as adjuvants to address challenges in numerous biomedical and medicinal chemistry applications including the delivery of siRNA. Polymer‐based therapeutics offer unique challenges in both synthesis and characterization as compared to small molecule therapeutics. The ability to control the structure of the polymer is critical in creating a therapeutic. Reported herein, are batch and flow polymerization processes to produce amphiphilic terpolymers through a Lewis acid BF3OEt2‐catalyzed polymerization. These processes focus on controlling reaction variables, which affect polymer structure in this rapid, exothermic, nonliving cationic polymerization. In addition to analytical characterization of the polymers, the in vivo activity of the polymer‐siRNA conjugates is also highlighted—demonstrating that the method of synthesis does affect the in vivo activity of the resulting polymer conjugate. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1119–1129  相似文献   
14.
Some exact solutions to a nonlinear heat equation are constructed. An initial-boundary value problem is examined for a nonlinear heat equation. To construct solutions, the problem for a partial differential equation of the second order is reduced to a similar problem for a first order partial differential equation.  相似文献   
15.
A computer analysis of the literature material clarified the types of activity most characteristic for pyridine derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 109–113, January, 1985.  相似文献   
16.
A study has been made of enantioselective hydrosilylation and reduction, by hydrogen transfer, of prochiral alkyl phenyl ketones or alkyl hetaryl ketones over various optically active catalysts. A total of 14 aromatic and heterocyclic carbinols were synthesized with preparative yields of 54–100%. The most effective catalytic systems were found to be complexes of RhCl3 and [Rh(cod)Cl]2 with the known optical inductor (S,S)-i-Pr-Pybox, with which we have obtained for the first time a series of heterocyclic secondary alcohols with an enantioselectivity of 20–63%.Latvian Institute of Organic Synthesis, Riga, LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 342–358, March, 1996. Original article submitted December 11, 1995.  相似文献   
17.
Alkyl(2-furyl), alkyl(2-thienyl), and methyl pyridyl ketones form stoichiometric inclusion complexes with -cyclodextrins. Reduction of these complexes in aqueous solution of Na2CO3 at room temperature yields the corresponding secondary alcohols with an optical yield which attains 27%.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1621–1627, December, 1993.  相似文献   
18.
Data on the production and the reactions of quinoline aldoximes and ketoximes and their derivatives are reviewed. The synthesis of new heterocycles based on quinoline oximes is examined separately. The main results from investigation of the biological activity of quinoline oximes are presented.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 163–190, February, 2005.  相似文献   
19.
When methylazines (2-, 3-, and 4-methylpyridines, methylpyrazine) are treated with N-chlorosuccinimide they undergo successive chlorination of the methyl group to give 2-chloromethylpyridine, 2-dichloromethylpyridine, and dichloromethylpyrazine in preparative yields. 3-Dichloromethylpyridine was synthesized from pyridine-3-aldehyde and PC15. The primary chlorination products of 4-methylthiazole are 4-methyl-5-chlorothiazole and 5-chloro-4-chloromethylthiazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 543–546, April, 1989.  相似文献   
20.
This paper surveys the state of the art for primary methods for the evaluation of electrolytic conductivity in aqueous solutions as they are currently carried out in several national metrological institutes (NMIs). The theoretical and practical basic knowledge of this measurement is described. Analysis of and comments on the different approaches are offered to give emphasis to technical difficulties and possible solutions. Further development is foreseeable, ensuring a common effort for the sharing of expertise that has been undertaken at the NMIs. In particular, improvements are expected towards traceable measurements of solutions with conductivity values lower than those actually standardized, down to the level of ultrapure water.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号