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   1544篇
  免费   15篇
电工技术   10篇
化学工业   68篇
金属工艺   6篇
机械仪表   17篇
建筑科学   11篇
能源动力   16篇
轻工业   68篇
水利工程   3篇
无线电   43篇
一般工业技术   53篇
冶金工业   1223篇
原子能技术   1篇
自动化技术   40篇
  2023年   3篇
  2022年   7篇
  2021年   13篇
  2020年   5篇
  2019年   4篇
  2018年   9篇
  2017年   10篇
  2016年   6篇
  2015年   3篇
  2014年   13篇
  2013年   37篇
  2012年   17篇
  2011年   33篇
  2010年   14篇
  2009年   14篇
  2008年   20篇
  2007年   14篇
  2006年   8篇
  2005年   9篇
  2004年   13篇
  2003年   8篇
  2002年   7篇
  2001年   10篇
  2000年   2篇
  1999年   32篇
  1998年   397篇
  1997年   183篇
  1996年   147篇
  1995年   77篇
  1994年   53篇
  1993年   77篇
  1992年   9篇
  1991年   18篇
  1990年   13篇
  1989年   10篇
  1988年   14篇
  1987年   11篇
  1986年   13篇
  1985年   17篇
  1984年   3篇
  1983年   5篇
  1982年   7篇
  1981年   7篇
  1980年   13篇
  1979年   3篇
  1978年   9篇
  1977年   51篇
  1976年   104篇
  1975年   3篇
  1965年   3篇
排序方式: 共有1559条查询结果,搜索用时 15 毫秒
51.
52.
Genomic selection has been widely implemented in many livestock breeding programs, but it remains incipient in buffalo. Therefore, this study aimed to (1) estimate variance components incorporating genomic information in Murrah buffalo; (2) evaluate the performance of genomic prediction for milk-related traits using single- and multitrait random regression models (RRM) and the single-step genomic best linear unbiased prediction approach; and (3) estimate longitudinal SNP effects and candidate genes potentially associated with time-dependent variation in milk, fat, and protein yields, as well as somatic cell score (SCS) in multiple parities. The data used to estimate the genetic parameters consisted of a total of 323,140 test-day records. The average daily heritability estimates were moderate (0.35 ± 0.02 for milk yield, 0.22 ± 0.03 for fat yield, 0.42 ± 0.03 for protein yield, and 0.16 ± 0.03 for SCS). The highest heritability estimates, considering all traits studied, were observed between 20 and 280 d in milk (DIM). The genetic correlation estimates at different DIM among the evaluated traits ranged from ?0.10 (156 to 185 DIM for SCS) to 0.61 (36 to 65 DIM for fat yield). In general, direct selection for any of the traits evaluated is expected to result in indirect genetic gains for milk yield, fat yield, and protein yield but also increase SCS at certain lactation stages, which is undesirable. The predicted RRM coefficients were used to derive the genomic estimated breeding values (GEBV) for each time point (from 5 to 305 DIM). In general, the tuning parameters evaluated when constructing the hybrid genomic relationship matrices had a small effect on the GEBV accuracy and a greater effect on the bias estimates. The SNP solutions were back-solved from the GEBV predicted from the Legendre random regression coefficients, which were then used to estimate the longitudinal SNP effects (from 5 to 305 DIM). The daily SNP effect for 3 different lactation stages were performed considering 3 different lactation stages for each trait and parity: from 5 to 70, from 71 to 150, and from 151 to 305 DIM. Important genomic regions related to the analyzed traits and parities that explain more than 0.50% of the total additive genetic variance were selected for further analyses of candidate genes. In general, similar potential candidate genes were found between traits, but our results suggest evidence of differential sets of candidate genes underlying the phenotypic expression of the traits across parities. These results contribute to a better understanding of the genetic architecture of milk production traits in dairy buffalo and reinforce the relevance of incorporating genomic information to genetically evaluate longitudinal traits in dairy buffalo. Furthermore, the candidate genes identified can be used as target genes in future functional genomics studies.  相似文献   
53.
Luenberger observer theory is extended to distributed parameter systems. This extension is based on the consideration of sensors. For systems with infinite dimensional state spaces, it is possible to construct the state vector asymptotically (or a part of the state vector) by a ‘good’ choice of sensors. We show that the link between detectability and sensor structure may be of some interest in the construction of observers.  相似文献   
54.
Fungal strains were screened for lipase producing activities and 10 strains were classified as good producers. Aspergillus sp., Fusarium sp., and Penicillium sp. exhibited the highest activities when fermented in wheat bran (WB) and soybean bran (SB). No fungal growth was observed using sugarcane bagasse (CB). An experimental design was applied to incorporate CB into the fermentation process for lipase production by Aspergillus sp. and Penicillium sp., and to evaluate the best moisture content for the substrate. Strains studied achieved maximum lipase activities with 25% CB combined with 75% WB or SB at 40% moisture content. The highest lipase activities were observed for WB and SB, and for SB combined with CB using Aspergillus sp. Fermentation of 96 h was the optimum period for enzyme production.  相似文献   
55.
Laurus nobilis is one of the most broadly used spices in Moroccan gastronomy. Its antimicrobial activity against both gram-positive and gram-negative bacterial species was demonstrated. Likewise, its toxicity was investigated on Swiss albinos' mice . Daily, mice were treated orally with 0.003 and 0.3 mg during 7 days. Plasmatic markers and enzymatic systems were assessed and histological alterations were evaluated. A significant increase in creatine phosphokinase level was observed. The microscopic evaluation showed that L. nobilis induces morphological perturbation in mice's liver. The results also showed an inhibitory effect of glyceraldehydes 3-phosphate dehydrogenase and an important increase in the level of thiobarbituric acid reactive substances and succinate dehydrogenase and no change in catalase activities. The results showed that L. nobilis induces toxicity at 0.3 mg/g mouse and affects energy metabolism and oxidative stress.

PRACTICAL APPLICATIONS


The aim of the present study is to determine the antimicrobial effect of Laurus nobilis on pathogens for potential application as herbal medicine in infusion or oral preparation. The effect of the spice extract was investigated on the metabolic markers, stress biomarkers and clinical parameters. This study was completed with histological coupes. To our knowledge, this is the first report to demonstrate the laurel effect on energy metabolism and oxidative stress.  相似文献   
56.
57.
An iterative algorithm, developed by the authors to compute the finite zeros of a linear multivariable system (Sebakhy et al. 1983), is extended to compute the infinite zeros of the system as well. The method is simple, efficient and suitable for programming on a digital computer  相似文献   
58.
This paper deals with sufficient conditions of asymptotic stability and stabilization for nonlinear discrete‐time systems represented by a Takagi–Sugeno‐type fuzzy model whose state variables take only nonnegative values at all times t for any nonnegative initial state. This class of systems is called positive systems. The conditions of stabilizability are obtained with state feedback control. This work is based on multiple Lyapunov functions. The results are presented in linear matrix inequalities form. A real plant is studied to illustrate this technique. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
59.
Increased use of diesel engine in on‐road vehicles presents a serious health concern, particularly in traffic‐congested urban areas. Diesel exhaust contains various gaseous and particulate pollutants, which, at high concentrations, pose adverse health effects. In this respect, various policy measures are being adopted worldwide to curtail emissions from diesel engines. This paper presents an assessment of diesel engine policy banning in the Greater Beirut Area. For this purpose, particulate matter levels in the air were measured after the ban and compared with concentrations reported prior to the ban. Health‐based socio‐economic benefits associated with improvement in air quality were then estimated using the long‐term decrease of particulate matter as an indicator.  相似文献   
60.
IT outsourcing is not a new concept. Originating from the early 60’s in the form of time sharing, IT outsourcing has evolved to the application service provision (ASP) model, in the late 90’s to pure services in the beginning of the century. Services, and their major representative web services, are actually the next phase of the movement toward Internet-based componentized software, known in the not so distant past as ASP. As the continuous expansion of the Internet and its relating technologies creates new marketing opportunities, traditional monolithic architectures are giving way to service-oriented computing (SOC), the architecture that enables service provision. SOC permits the utilization of large systems which are comprised of self-containing building blocks: services. Services may be made public, searched, reused and combined to form complex business processes while in the same time retaining a significant level of flexibility. Services and SOC have emerged as a response to a fundamental shift in enterprise business culture that started at the late 90’s. Although they are promising as an IT outsourcing enabler, many issues need to be dealt with before they can be considered suitable for wide adoption. These issues are of technological, business, economic and cultural nature and they were also faced by ASPs in the past. It is worth revisiting the successes and failures of the ASP model in order to get a better understanding of the evolving IT outsourcing industry. In this work, we describe the evolution of service provision from its initial form as software application, through the application service provision era and towards the new trend of web services.  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