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   183篇
  免费   3篇
化学工业   78篇
金属工艺   3篇
机械仪表   4篇
建筑科学   4篇
矿业工程   1篇
能源动力   3篇
轻工业   33篇
水利工程   2篇
无线电   6篇
一般工业技术   23篇
冶金工业   18篇
原子能技术   2篇
自动化技术   9篇
  2023年   4篇
  2022年   7篇
  2021年   13篇
  2020年   3篇
  2019年   3篇
  2018年   6篇
  2017年   4篇
  2016年   4篇
  2015年   4篇
  2014年   4篇
  2013年   11篇
  2012年   5篇
  2011年   4篇
  2010年   7篇
  2009年   5篇
  2008年   12篇
  2007年   3篇
  2006年   7篇
  2005年   5篇
  2004年   6篇
  2003年   5篇
  2002年   6篇
  2001年   3篇
  2000年   1篇
  1999年   2篇
  1998年   3篇
  1997年   7篇
  1996年   9篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   4篇
  1986年   2篇
  1985年   1篇
  1984年   5篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   3篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
  1971年   1篇
排序方式: 共有186条查询结果,搜索用时 24 毫秒
91.
A novel multitriphenylamine substituted derivatives, possessing the respective photochromic groups were synthesized by Stille cross-coupling methodology. The hyperbranched structures have been characterized by 1H NMR, 13C NMR. Obtained structures show good stability in common organic solvents such as CHCl3, toluene and CH2Cl2 and exhibit excellent thermal stability. Electrochemical results and theoretical calculation suggest that oxidation and reduction start from the side of amine and branching five member heterocycle ring moieties, respectively.  相似文献   
92.
The ability of 4 squirrel monkeys to distinguish between members of 3 homologous series of substances (aliphatic alcohols, aldehydes, and ketones) was investigated, and their performance was compared with that of a group of 10 human participants. With all 3 substance classes, and in both species, a significant negative correlation was found between discrimination performance and structural similarity of odorants in terms of differences in carbon chain length. These findings suggest carbon chain length of aliphatic odorants to be one of presumably several determinants of the interaction between stimulus molecule and olfactory receptor and support the assumption that human and nonhuman primates may share common mechanisms of odor quality perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
93.
It was established that the synthesis of hybrid molecules containing a thiazolidinone and a (2Z)-2-chloro-3-(4-nitrophenyl)prop-2-ene structural fragments is an effective approach for the design of potential anticancer agents. Given the results of the previous SAR-analysis, the aim of the study was to synthesize a novel 4-thiazolidinone derivative Les-3331 and investigate its molecular mechanism of action in MCF-7 and MDA-MB-231 breast cancer cells. The cytotoxic properties and antiproliferative potential of Les-3331 were determined. The effect of the tested compound on apoptosis induction and mitochondrial membrane potential was checked by flow cytometry. ELISA was used to determine caspase-8 and caspase-9, LC3A, LC3B, Beclin-1, and topoisomerase II concentration. Additionally, PAMPA, in silico or in vitro prediction of metabolism, CYP3A4/2D6 inhibition, and an Ames test were performed. Les-3331 possesses high cytotoxic and antiproliferative activity in MCF-7 and MDA-MB-231 breast cancer cells. Its molecular mechanism of action is associated with apoptosis induction, decreased mitochondrial membrane potential, and increased caspase-9 and caspase-8 concentrations. Les-3331 decreased LC3A, LC3B, and Beclin-1 concentration in tested cell lines. Topoisomerase II concentration was also lowered. The most probable metabolic pathways and no DDIs risk of Les-3331 were confirmed in in vitro assays. Our studies confirmed that a novel 4-thiazolidinone derivative represents promising anti-breast cancer activity.  相似文献   
94.
Bisphenol A (BPA), with its wide array of products and applications, is currently one of the most commonly produced chemicals in the world. A narrow pool of data on BPA–microorganism–plant interaction mechanisms has stimulated the following research, the aim of which has been to determine the response of the soil microbiome and crop plants, as well as the activity of soil enzymes exposed to BPA pressure. A range of disturbances was assessed, based on the activity of seven soil enzymes, an abundance of five groups of microorganisms, and the structural diversity of the soil microbiome. The condition of the soil was verified by determining the values of the indices: colony development (CD), ecophysiological diversity (EP), the Shannon–Weaver index, and the Simpson index, tolerance of soil enzymes, microorganisms and plants (TIBPA), biochemical soil fertility (BA21), the ratio of the mass of aerial parts to the mass of plant roots (PR), and the leaf greenness index: Soil and Plant Analysis Development (SPAD). The data brought into sharp focus the adverse effects of BPA on the abundance and ecophysiological diversity of fungi. A change in the structural composition of bacteria was noted. Bisphenol A had a more beneficial effect on the Proteobacteria than on bacteria from the phyla Actinobacteria or Bacteroidetes. The microbiome of the soil exposed to BPA was numerously represented by bacteria from the genus Sphingomonas. In this object pool, the highest fungal OTU richness was achieved by the genus Penicillium, a representative of the phylum Ascomycota. A dose of 1000 mg BPA kg−1 d.m. of soil depressed the activity of dehydrogenases, urease, acid phosphatase and β-glucosidase, while increasing that of alkaline phosphatase and arylsulfatase. Spring oilseed rape and maize responded significantly negatively to the soil contamination with BPA.  相似文献   
95.
An effective two-stage method for obtaining polyacrylonitrile fibers with antibacterial properties has been developed. The method consists of the incorporation of carboxylic groups into fibers by PAA grafting polymerization followed by fiber impregnation with gentamycin, neomycin, or penicillin solutions. The modified fibers show effective biocide liberation into water and antibacterial activity towards Gram-positive and Gram-negative microorganisms (Staphylococuus aureus, Escherichia coli, and Pseudomonas aeruginosa). The presence of antibiotics combined with the modified fibers though chemical bonds has been proved by IR and 1H-NMR investigations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1955–1966, 1997  相似文献   
96.
The authors tested the ability of 60 free-flying honeybees (Apis mellifera carnica) to discriminate a conditioning odor from an array of 26 simultaneously presented substances. The stimuli included 10 pairs of enantiomers and 6 essential oils. The bees (a) significantly distinguished between 98% of the 540 odor pairs tested, thus showing an excellent overall discrimination performance, and (b) were able to discriminate between the optical isomers of limonene, α-pinene, β-citronellol, menthol, and carvone but failed to distinguish between the (+)- and (–)- forms of α-terpineol, camphor, rose oxide, fenchone, and 2-butanol. The findings support the assumptions that enantioselective molecular odor receptors may exist only for some volatile enantiomers and that insects and mammals may share common principles of odor quality perception, irrespective of their completely differing repertoires of olfactory receptors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
97.
Detailed analysis of nanopores (IUPAC micropores at pore half-width x < 1 nm) of carbonised porous phenolformaldehyde resin microbeads used as a precursor of activated carbon (AC) and CO2 activated carbon (at 50% burn-off) has been performed on the basis of high-resolution transmission electron microscopy (HRTEM) image analysis and nitrogen adsorption data analysed using several density functional theory (DFT) methods. The results of quenched solid DFT (QSDFT) and nonlocal (NLDFT) are in agreement with the pore size distributions of nanopores based on the HRTEM image analysis. Development of porosity with progressive activation degree in a series of ACs leads to enhancement of the deviation of the pore shape from the used pore models. The TG/DTA data and Raman spectra show nonlinear but weak changes in the AC characteristics with increasing burn-off degree.  相似文献   
98.
99.
100.
Using a conditioning paradigm, the olfactory sensitivity of five spider monkeys, three squirrel monkeys, and three pigtail macaques for six acyclic monoterpene alcohols that differ markedly in their frequency of occurrence in plant odors was assessed. The results showed that: (1) all three primate species have a well-developed olfactory sensitivity for acyclic monoterpene alcohols; (2) squirrel monkeys are significantly more sensitive for members of this class of odorants than the other two species and are able to detect all six odorants at concentrations below 0.1 ppm; and (3) there is a lack of positive correlations between olfactory sensitivity and the abundance of the acyclic monoterpene alcohols in flower odors and etheric oils. The results lend support to the growing body of evidence that suggests between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance. The findings do not support the hypothesis that olfactory sensitivity for members of a chemical class may be related to the frequency of occurrence of such odorants in a species' chemical environment.  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