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   188篇
  免费   12篇
  国内免费   1篇
电工技术   1篇
化学工业   55篇
金属工艺   5篇
机械仪表   5篇
建筑科学   5篇
能源动力   4篇
轻工业   25篇
水利工程   1篇
石油天然气   1篇
无线电   9篇
一般工业技术   45篇
冶金工业   8篇
自动化技术   37篇
  2023年   2篇
  2022年   2篇
  2021年   1篇
  2020年   9篇
  2019年   3篇
  2018年   8篇
  2017年   5篇
  2016年   9篇
  2015年   8篇
  2014年   14篇
  2013年   24篇
  2012年   16篇
  2011年   12篇
  2010年   6篇
  2009年   13篇
  2008年   8篇
  2007年   8篇
  2006年   9篇
  2005年   3篇
  2004年   2篇
  2002年   2篇
  2000年   3篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1993年   1篇
  1992年   7篇
  1991年   1篇
  1988年   4篇
  1987年   1篇
  1986年   2篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1971年   1篇
排序方式: 共有201条查询结果,搜索用时 302 毫秒
111.
Grape juice quality can be substantially influenced by different processing methods and their parameters. This study deals with the influence of thermomaceration temperature and its holding time on important juice quality parameters such as the content of trans-resveratrol, trans-piceid, trans-ε-viniferin, and 2,4,6-trihydroxyphenantrene-2-O-glucoside. All the aforementioned compounds together with antioxidative capacity, total polyphenols, and antimutagenic activity were measured. This study used the following grapes: Blaufränkisch, Blaufränkisch bio, Saint Laurent, Grüner Veltliner, Grüner Veltliner bio, and Müller-Thurgau. For all tested grape varieties, the most important processing parameters were temperature and thermomaceration holding time. There were no significant differences in the content of the studied compounds. Three preservation technologies, freezing, bottle pasteurization, and high-pressure treatment, were also studied regarding the content of abovementioned biologically active compounds. Results of this study can be immediately applied to grape juice production.  相似文献   
112.
The lipid bilayer is a basic building block of biological membranes and can be pictured as a barrier separating two compartments filled with electrolyte solution. Artificial planar lipid bilayers are therefore commonly used as model systems to study the physical and electrical properties of the cell membranes in contact with electrolyte solution. Among them the glycerol-based polar phospholipids which have dipolar, but electrically neutral head groups, are most frequently used in formation of artificial lipid bilayers. In this work the electrical properties of the lipid layer composed of zwitterionic lipids with non-zero dipole moments are studied theoretically. In the model, the zwitterionic lipid bilayer is assumed to be in contact with aqueous solution of monovalent salt ions. The orientational ordering of water, resulting in spatial variation of permittivity, is explicitly taken into account. It is shown that due to saturation effect in orientational ordering of water dipoles the relative permittivity in the zwitterionic headgroup region is decreased, while the corresponding electric potential becomes strongly negative. Some of the predictions of the presented mean-field theoretical consideration are critically evaluated using the results of molecular dynamics (MD) simulation.  相似文献   
113.
Providing of children aged 3-5 years with vitamins C, B1, B2, B6 and PP was studied before and after intake (during 3 months) of multivitamin "Pikovit" (KRKA, Yugoslavia) by the excretion with urine of ascorbic acid, thiamine, riboflavin, 4-pyridoxic acid and N-methylnicotinamide. Before "Pikovit" intake the mean level of thiamine excretion was close to the lower border of the normal level, while ascorbic acid and N-methylnicotinamide levels were lower than the normal in 73 and 69% of the children studied, respectively. "Pikovit" induced an increase in the mean values of excretion of all vitamins studied except for ascorbic acid. The multivitamin prevented the impairment of children providing with vitamins C and B6, and improved their provision with vitamins B1, B2 and PP. However, the doses of vitamins used proved to be insufficient for complete normalization of the vitamin status in children, therefore it is necessary to use "Pikovit" in higher doses as it is recommended by the firm-manufacturer.  相似文献   
114.
Commercially delivered 2-chloro-5-methyl-1,4-phenylenediamine (1 metric ton) was not identical to the commonly used dye intermediate; it was found that the material was a pure but not yet described molecule. 1H, 13C NMR, MS, microanalysis and X-ray diffraction showed that the substance was in fact 5-amino-4-chloro-2,7-dimethyl-1H-benzimidazole. The manufacturer's mistake was explained by independent synthesis, which revealed that the key step was nitration of N-(5-chloro-2-methyl-4-nitrophenyl)acetamide giving N-(5-chloro-2-methyl-4,6-dinitrophenyl)acetamide, which requires Fe(III) catalysis. Subsequent reduction of N-(5-chloro-2-methyl-4,6-dinitrophenyl)acetamide with hydrogen and Pd/C catalyst exclusively gives N-(2,4-diamino-3-chloro-6-methylphenyl)acetamide. The ring closure reaction giving 5-amino-4-chloro-2,7-dimethyl-1H-benzimidazole takes place during the reduction with iron.  相似文献   
115.
The study was made of lisine- and arginine-rich histone fractions and DNA in lymphocytes of peripheral blood in patients with lupus erythematosus. The findings showed intranuclear changes of immunocompetent cells in various forms of the disease. The above parameters may be used in the diagnosis, evaluation of treatment efficacy, prognosis.  相似文献   
116.
117.
Schiphol, the main airport of the Netherlands, is growing rapidly. The aircraft movements, also growing in number, place a considerable environmental burden on the surrounding population, notably, noise and odour nuisance and risks. In the process of deciding on how to extend the capacity of the airport to accommodate the anticipated twofold growth in the number of movements with respect to 1990, environmental problems form a major concern. The concern about risks for the surrounding population was enhanced after the crash on 4 October 1992, in which a Boeing 747 cargo carrier bored into a block of flats in a suburb of Amsterdam near Schiphol. In this accident, the four crew members were killed, together with 39 inhabitants of the flats/apartment building. These risks were studied as part of the Environmental Impact Assessment (EIA). To make these studies useful for decision making necessitated a major improvement in the available techniques for risk quantification. The results of the quantitative analyses, using several different methods, have all indicated that the activities of Schiphol pose a considerable risk compared to other major industrial activities in the Netherlands. This paper describes the development of the methodology from 1990 in the light of the policy context in which it took place. Use of the methods in the decision-making process is illustrated by describing the current status of this process.  相似文献   
118.
Frontal gland contents of soldiers of three Prorhinotermes species, Prorhinotermes canalifrons, Prorhinotermes inopinatus, and Prorhinotermes simplex, consisted of two groups of compounds: nitroalkenes and sesquiterpene hydrocarbons. Analysis by gas chromatography-mass spectrometry revealed (E)-1-nitropentadec-1-ene as the major component of the glands with mean values of 152, 207, and 293 μg/individual for P. canalifrons, P. inopinatus, and P. simplex, respectively. Four other 1-nitroalkenes (C13, C14, C16, and C17), and two nitrodienes (C15 and C17) were also detected in the three species. The C17:1 nitroalkene was identified as (E)-1-nitroheptadec-1-ene. The sesquiterpene composition of the gland was species-specific: P. simplex contained (3Z,6E)-α-farnesene (mean of 39 μg/individual), while P. canalifrons and P. inopinatus contained the same compound (means of 0.5 and 1.5 μg/individual, respectively) as well as the (3E,6E) isomer (means of 1.8 and 0.7 μg/individual, respectively). Two other sesquiterpenes, trans-β-bergamotene and (Z)-γ-bisabolene, were also found in low quantities in the frontal gland of P. canalifrons.  相似文献   
119.
120.
Nepal is very rich in hydropower. Unfortunately, due to the mountainous topography it is difficult to build a comprehensive electrical grid. Only 30% of the population (primarily in urban areas) currently has access to electricity from the national grid and about 5% from non-grid (micro-hydropower and solar). In addition the power is seasonal, resulting in poor “load factor”. On a seasonal basis, the power generated by large hydropower stations during the summer surpasses the peak demand of the country. The peak load varies from 400 MW to 560 MW from 17:00 to 21:00 hours. The maximum demand recorded on December 8, 2004 was 557.53 MW at 18:16 hour. Thus, the widespread hydroelectric potential is not effectively utilized.  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