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   4881篇
  免费   321篇
  国内免费   13篇
电工技术   44篇
综合类   1篇
化学工业   948篇
金属工艺   104篇
机械仪表   119篇
建筑科学   88篇
矿业工程   7篇
能源动力   119篇
轻工业   868篇
水利工程   56篇
石油天然气   17篇
无线电   217篇
一般工业技术   651篇
冶金工业   1432篇
原子能技术   26篇
自动化技术   518篇
  2024年   18篇
  2023年   41篇
  2022年   63篇
  2021年   222篇
  2020年   146篇
  2019年   195篇
  2018年   198篇
  2017年   207篇
  2016年   175篇
  2015年   133篇
  2014年   173篇
  2013年   265篇
  2012年   262篇
  2011年   269篇
  2010年   184篇
  2009年   216篇
  2008年   173篇
  2007年   148篇
  2006年   119篇
  2005年   103篇
  2004年   71篇
  2003年   71篇
  2002年   56篇
  2001年   50篇
  2000年   43篇
  1999年   62篇
  1998年   436篇
  1997年   278篇
  1996年   181篇
  1995年   112篇
  1994年   102篇
  1993年   83篇
  1992年   29篇
  1991年   27篇
  1990年   17篇
  1989年   31篇
  1988年   29篇
  1987年   22篇
  1986年   21篇
  1985年   16篇
  1984年   10篇
  1983年   4篇
  1982年   8篇
  1981年   12篇
  1980年   11篇
  1978年   7篇
  1977年   32篇
  1976年   70篇
  1975年   3篇
  1974年   3篇
排序方式: 共有5215条查询结果,搜索用时 109 毫秒
101.
Network and service management has established itself as a research field in the general area of computer networks. However, up to now, no appropriate organization of the field has been carried out in terms of a comprehensive list of terms and topics. In this paper, we introduce a taxonomy for network and service management. With such a taxonomy, it is possible to better understand the landscape of research as well as to reason about possible future challenges and opportunities. As such, in addition to the taxonomy itself, we also present an initial analysis of the field’s past, present, and future, based on the records of papers submitted and accepted in major conferences in the area, as well as a site survey performed through a questionnaire answered by experts from both industry and academia.  相似文献   
102.
Hyperspectral images usually have large volumes of data comprising hundreds of spectral bands. Removal of redundant bands can both reduce computational time and improve classification performance. This work proposes and analyses a band-selection method based on the k-means clustering strategy combined with a classification approach using entropy filtering. Experimental results in different terrain images show that our method can significantly reduce the number of bands while maintaining an accurate classification.  相似文献   
103.
104.
This work focuses on the detailed study of the palladium(II) extraction reactions by N-methyl-N-phenyl-octanthioamide (MPHTA) and N-methyl-N-cyclohexyl-octanthioamide (MCHTA) in toluene, since their ability to efficiently and selectively recover Pd(II) from a wide range of HCl concentrations is already known. Equilibrium data are presented and discussed, and further complemented by information depicted from UV–visible and NMR spectra. The determined apparent molar volumes show that MPHTA is monomeric, and MCHTA exhibits a slight tendency to aggregate. The Pd(II) extraction reactions by MPHTA and MCHTA are equivalent until 4.5 M HCl, passing through the formation of inner-sphere complexes with the metal ion.  相似文献   
105.

Visually impaired individuals often rely on assistive technologies such as white canes for independent navigation. Many electronic enhancements to the traditional white cane have been proposed. However, only a few of these proof-of-concept technologies have been tested with authentic users, as most studies rely on blindfolded non-visually impaired participants or no testing with participants at all. Experiments involving blind users are usually not contrasted with the traditional white cane. This study set out to compare an ultrasound-based electronic cane with a traditional white cane. Moreover, we also compared the performance of a group of visually impaired participants (N = 10) with a group of blindfolded participants without visual impairments (N = 31). The results show that walking speed with the electronic cane is significantly slower compared to the traditional white cane. Moreover, the results show that the performance of the participants without visual impairments is significantly slower than for the visually impaired participants. No significant differences in obstacle detection rates were observed across participant groups and device types for obstacles on the ground, while 79% of the hanging obstacles were detected by the electronic cane. The results of this study thus suggest that electronic canes present only one advantage over the traditional cane, namely in its ability to detect hanging obstacles, at least without prolonged practice. Next, blindfolded participants are insufficient substitutes for blind participants who are expert cane users. The implication of this study is that research into digital white cane enhancements should include blind participants. These participants should be followed over time in longitudinal experiments to document if practice will lead to improvements that surpass the performance achieved with traditional canes.

  相似文献   
106.
Shrimp residues were dried (65 °C), grounded, and posteriorly used as an ingredient to the production of ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’. Both products were packed in modified atmosphere (100% N2) and stored for 180 days (25 °C) for shelf life evaluation. The centesimal composition, physicochemical, microbiological and sensory analyses were carried out in triplicate. The microbiological analysis (residue and shrimp flour) was within the limits of the legislation, confirming the hygienic–sanitary care during processing. The protein content was the most outstanding (40.13% for the spiced shrimp flour and 20.52% for the shrimp flavoured biscuits). The microbiological evaluation for the ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’ was below the legal limit, and both products were accepted by sensory analysis. The shelf life evaluation demonstrated stability for 6 months. Thus, we concluded that the Litopenaeus vannamei shrimp residue is a promising ingredient in the food industry.  相似文献   
107.
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   
108.
109.
110.
Silicon - Corn plants are highly demanding of nitrogen and the application of silicon has been studied because it minimizes stress from different natures, and for the better utilization of some...  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