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   1098篇
  免费   89篇
  国内免费   1篇
电工技术   7篇
化学工业   673篇
金属工艺   19篇
机械仪表   14篇
建筑科学   36篇
矿业工程   5篇
能源动力   19篇
轻工业   198篇
水利工程   4篇
无线电   21篇
一般工业技术   117篇
冶金工业   36篇
原子能技术   1篇
自动化技术   38篇
  2024年   2篇
  2023年   20篇
  2022年   153篇
  2021年   207篇
  2020年   48篇
  2019年   44篇
  2018年   41篇
  2017年   54篇
  2016年   46篇
  2015年   44篇
  2014年   56篇
  2013年   60篇
  2012年   60篇
  2011年   63篇
  2010年   52篇
  2009年   48篇
  2008年   33篇
  2007年   25篇
  2006年   23篇
  2005年   13篇
  2004年   17篇
  2003年   7篇
  2002年   14篇
  2001年   5篇
  2000年   5篇
  1999年   7篇
  1998年   8篇
  1997年   6篇
  1996年   5篇
  1995年   5篇
  1993年   5篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1977年   1篇
  1976年   5篇
  1974年   1篇
排序方式: 共有1188条查询结果,搜索用时 0 毫秒
51.
The aim of Collective Research Project QUALI-JUICE (COLL-CT-2005, Co Nr 012461) was to introduce the biosensors in control of microbiologically pure apple juice production. Three commercial lactate biosensors were used and compared with enzyme kits assays. Parallel the microbiological analysis of the production process at one juice producing enterprise was done. The results of lactic acid assay with biosensors were in good correlation with those obtained by enzyme kits. The main benefit of biosensor use was shortening of measurement time as compared with assay by enzyme kit and possibility to measure at line. The concentration of l-lactic acid in apple pulp could be correlated with the number of lactic acid bacteria. Pasteurization process was eliminating lactic acid bacteria and the concentration of lactic acid was at this stage not exceeding 0.1 g L−1. The final product (apple concentrate) contained in some cases very high amounts of lactic acid indicating secondary microbiological contamination after pasteurization step. Parallel microbiological analysis of production process and lactate assay indicated that the critical point during production was prolonged vacuum filtration after pasteurization.  相似文献   
52.
Grains of winter wheat (Korweta variety) were partially germinated in an abiotic stress condition (0–15 mM FeSO4 solutions) in order to accumulate iron by ferritin overexpression. The physical, chemical, biochemical properties and technological parameters of the obtained material as well as their resistance to an insect storage pest—granary weevil—were analyzed. Sprouted wheat grains with overexpression of ferritin contain 52 times more iron, more than 50 % in form of ferritin. The contents of reducing sugars, crude protein, fiber and ash as well as amylolytic activity increased significantly in sprouted wheat grain, while starch, fat, wet gluten, falling number and inhibition activity against granary weevil α-amylase decreased. Germinated wheat grain enriched with iron strongly affected granary weevil developmental parameters. Despite the fact that technological parameters of the product were deteriorated, it is worth to consider this material application as an iron supplement for cereal products, when the application of soybean is impossible.  相似文献   
53.
In this work the electrochemical characteristics of copper and steel in chromate, cyanide, and phosphate baths as well as in a commercial bath (ENSTRIP S-180), in the absence of chromium and cyanides were determined. Average rates of copper coatings stripping from steel in the above mentioned baths and the baths influence on the morphology of steel surfaces were described. It was found that the commercial bath ENSTRIP S-180 could be successfully used for stripping of copper coatings from steel elements.  相似文献   
54.
Age related macular degeneration of the eye is brought about by damage to the retinal pigment epithelium (RPE) and is a major cause of adult blindness. One potential treatment method is transplantation of RPE cells grown in vitro. Maintaining RPE cell viability and physiological function in vitro is a challenge, and this must also be achieved using materials that can be subsequently used to deliver an intact cell sheet into the eye. In this paper, plasma polymerisation has been used to develop a chemically modified surface for maintaining RPE cells in vitro. Multiwell plates modified with a plasma copolymer of allylamine and octadiene maintained RPE cell growth at a level similar to that of TCPS. However, the addition of bound glycosaminoglycans (GAGs) to the plasma polymerised surface significantly enhanced RPE proliferation. Simply adding GAG to the culture media had no positive effect. It is shown that a combination of plasma polymer and GAG is a promising method for developing suitable surfaces for cell growth and delivery, that can be applied to any substrate material.  相似文献   
55.
Silicon carbonitride (a-Si:N:C) films produced by remote plasma chemical vapor deposition (RP-CVD) were investigated. Tetramethyldisilazane as a single-source precursor and (H2+N2) upstream gas mixture for plasma generation were used. The influence of the upstream gas composition on the structure, density, mechanical and tribological properties of the films deposited on p-type Si (001) wafers (both heated—T s =300°C and unheated—T s =30°C) are reported. The H2 RP-CVD process was found to result in the formation of outstanding low friction (0.04) and high hardness (H=27-31 GPa) a-Si:N:C films exhibiting promisingly high H/E values.  相似文献   
56.
We have compared the results of estimations of the total number of protein-coding genes in the Saccharomyces cerevisiae genome, which have been obtained by many laboratories since the yeast genome sequence was published in 1996. We propose that there are 5300-5400 genes in the genome. This makes the first estimation of the number of intronless ORFs longer than 100 codons, based on the features of the set of genes with phenotypes known in 1997 to be correct. This estimation assumed that the set of the first 2300 genes with known phenotypes was representative for the whole set of protein-coding genes in the genome. The same method used in this paper for the approximation of the total number of protein-coding sequences among more than 40 000 ORFs longer than 20 codons gives a result that is only slightly higher. This suggests that there are still some non-coding ORFs in the databases and a few dozen small ORFs, not yet annotated, which probably code for proteins.  相似文献   
57.
Sometime Query Answering Systems (QAS) for a Distributed Autonomous Information System (DAIS) may fail by returning the empty set of objects as an answer for a query q. Systems in DAIS can be incomplete, have hierarchical attributes, and the semantics of attributes and their values may differ between sites. Also, if there are no objects in S matching q, the query may fail when submitted to S. Alternatively, QAS for S may try to relax the query q as it was proposed in T. Gaasterland (IEEE Expert, 12(5), 1997, 48–59), P. Godfrey (International Journal of Cooperative Information Systems, 6(2), 1997, 95–149) and W. Chu et al. (Journal of Intelligent Information Systems, 6(2/3), 1996, 223–259). It means that q can be replaced by a new more general query. Clearly, the goal is to find possibly the smallest generalization of q which will not fail in S. Smaller generalizations guarantee higher confidence in objects returned by QAS. Such QAS is called cooperative (only one site is involved). Queries may also fail in S when some of the attributes listed in q are outside the domain of S. To resolve this type of queries, assuming that S is a part of DAIS, we may extract definitions of such attributes from information systems residing at some of the remote sites for S and next use them to approximate q in S. In order to do that successfully, we assume that all involved systems have to agree on the ontology of some of their common attributes Z.W. Raś and A. Dardzińska (Information Systems International Journal, 29(1), 2004, 47–58; Proceedings of FQAS 2004 Conference, LNCS/LNAI No. 3055, 2004, pp. 125–136); Z.W. Raś and S. Joshi, Fundamenta Informaticae Journal, 30(3/4), 1997, 313–324. QAS based on the above strategy is called collaborative (minimum two sites are involved). Similarly, a query may fail in S when the granularity of an attribute used in q is finer than the granularity of the same attribute in S. This paper shows how to use collaboration and cooperation approach to solve failing queries in DAIS assuming that attributes are hierarchical. Some aspects of a collaboration strategy dealing with failing query problem for non-hierarchical attributes have been presented in Z.W. Raś and A. Dardzińska (Information Systems International Journal, 29(1), 2004, 47–58; Proceedings of FQAS 2004 Conference, LNCS/LNAI No. 3055, 2004, pp. 125–136).  相似文献   
58.
The method of dispersion analysis and experiments are used to establish the possibility of using coal concentration waste, which contains a clay component close to conventional clay raw materials and quartz, calcite and coal impurities. The results of an experimental study of the physicochemical properties of model mixtures are presented together with some practical recommendations.  相似文献   
59.
The effect of silicon ion implantation upon the corrosion resistance and structure of the surface layers formed during the implantation in the Ti6A14V titanium alloy was examined. The silicon doses were 0.5, 1.5, 3.0 and 4.5 × 1017Si+/cm2, and the ion beam energy was 100 keV. The corrosion resistance of the samples exposed to a 0.9% NaCl solution at a temperature of 37 °C was measured using electrochemical methods. The structure of the surface layers formed during the implantation was examined by a transmission electron microscope (TEM). The results of the corrosion resistance examinations have shown that the unimplanted and 0.5 × 1017Si+/cm2 implanted samples undergo uniform corrosion. At higher silicon doses, the samples show pitting corrosion. The highest corrosion resistance was shown by the alloy implanted with 0.5 × 1017Si+/cm2. It has been found that, after a long-term (1200 h) exposure to a 0.9% NaCl solution, the corrosion resistance of the samples is greater than that observed after a short-term exposure. TEM examinations have shown that, beginning from a dose of 1.5 × 1017Si+/cm2, the surface of the Ti6A14V alloy samples becomes amorphous. Heating of the 1.5 × 1017Si+/cm2 implanted samples at 200 and 500 °C does not change their structure, whereas after heating at 650 °C, the amorphous phase vanishes.  相似文献   
60.
Two methods of solving the inverse heat conduction problem with employment of the discrete Fournier transform are presented in this article. The first one operates similarly to the SVD algorithm and consists in reducing the number of components of the discrete Fournier transform which are taken into account to determine the solution to the inverse problem. The second method is related to the regularization of the solution to the inverse problem in the discrete Fournier transform domain. Those methods were illustrated by numerical examples. In the first example, an influence of the boundary conditions disturbance by a random error on the solution to the inverse problem (its stability) was examined. In the second example, the temperature distribution on the inner boundary of the multiply connected domain was determined. Results of calculations made in both ways brought very good outcomes and confirm the usefulness of applying the discrete Fournier transform to solving inverse problems.  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