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   41538篇
  免费   2451篇
  国内免费   34篇
电工技术   290篇
综合类   34篇
化学工业   7506篇
金属工艺   773篇
机械仪表   795篇
建筑科学   1272篇
矿业工程   78篇
能源动力   802篇
轻工业   5453篇
水利工程   371篇
石油天然气   170篇
武器工业   4篇
无线电   2373篇
一般工业技术   7392篇
冶金工业   10882篇
原子能技术   198篇
自动化技术   5630篇
  2023年   370篇
  2022年   328篇
  2021年   877篇
  2020年   764篇
  2019年   693篇
  2018年   1540篇
  2017年   1531篇
  2016年   1592篇
  2015年   1126篇
  2014年   1434篇
  2013年   2780篇
  2012年   2421篇
  2011年   2251篇
  2010年   1763篇
  2009年   1580篇
  2008年   1833篇
  2007年   1613篇
  2006年   1195篇
  2005年   992篇
  2004年   939篇
  2003年   824篇
  2002年   728篇
  2001年   487篇
  2000年   470篇
  1999年   640篇
  1998年   3480篇
  1997年   2083篇
  1996年   1346篇
  1995年   788篇
  1994年   678篇
  1993年   663篇
  1992年   216篇
  1991年   241篇
  1990年   232篇
  1989年   230篇
  1988年   201篇
  1987年   180篇
  1986年   182篇
  1985年   229篇
  1984年   189篇
  1983年   138篇
  1982年   170篇
  1981年   181篇
  1980年   162篇
  1979年   131篇
  1978年   125篇
  1977年   207篇
  1976年   447篇
  1975年   89篇
  1973年   85篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
41.
Engineering with Computers - This work presents a new efficient array-based algorithm for adaptive mesh refinement capable of interactively generating millions of triangles. The new refinement...  相似文献   
42.
International Journal of Computer Vision - We identify two issues as key to developing effective face recognition systems: maximizing the appearance variations of training images and minimizing...  相似文献   
43.
Nonwoven geotextiles have been used as filters in geotechnical and geoenvironmental works for half a century. They are easy to install and can be specified to meet the requirements for proper filter performance. There are situations where a geotextile filter may be subjected to tensile loads, which may alter relevant filter properties, such as its filtration opening size. Examples of such situations are silty fence applications, geotextile separators, geotextile tubes and geotextiles under embankments on soft soils. This paper investigates the effects of tensile strains on geotextile pore dimensions. A special equipment and testing technique allowed tests to be carried out on geotextile specimens subjected to tension and confinement. The results obtained showed that the variation in filtration opening size depends on the type of strain state the geotextile is subjected, under which the geotextile pore diameter may remain rather constant or increase significantly. However, confinement reduces the geotextile filtration opening size independent on the strain mobilised. An upper bound for the filtration opening size of strained nonwoven geotextiles is introduced and was satisfactory for the geotextile products tested.  相似文献   
44.
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included.  相似文献   
45.
The Journal of Supercomputing - Modern GPUs can achieve high computing power at low cost, but still requires much time and effort. Tridiagonal system and scan solvers are one example of widely used...  相似文献   
46.
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could.  相似文献   
47.
Mine Water and the Environment - Water inflows through fracture networks are a major economic and safety issue in underground mines. Although pre-grouting of pilot holes during mine development...  相似文献   
48.
49.
Calcium (Ca) is a key micronutrient of high relevance for human nutrition that also influences the texture and taste of dairy products and their processability. In bovine milk, Ca is presented in several speciation forms, such as complexed with other milk components or free as ionic calcium while being distributed between colloidal and serum phases of milk. Partitioning of Ca between these phases is highly dynamic and influenced by factors, such as temperature, ionic strength, pH, and milk composition. Processing steps used during the manufacture of dairy products, such as preconditioning, concentration, acidification, salting, cooling, and heating, all contribute to modify Ca speciation and partition, thereby influencing product functionality, product yield, and fouling of equipment. This review aims to provide a comprehensive understanding of the influence of Ca partition on dairy products properties to support the development of kinetics models to reduce product losses and develop added-value products with improved functionality. To achieve this objective, approaches to separate milk phases, analytical approaches to determine Ca partition and speciation, the role of Ca on protein–protein interactions, and their influence on processing of dairy products are discussed.  相似文献   
50.
The rumen is a complex microbial system of substantial importance in terms of greenhouse gas emissions and feed efficiency. This study proposes combining metagenomic and host genomic data for selective breeding of the cow hologenome toward reduced methane emissions. We analyzed nanopore long reads from the rumen metagenome of 437 Holstein cows from 14 commercial herds in 4 northern regions in Spain. After filtering, data were treated as compositional. The large complexity of the rumen microbiota was aggregated, through principal component analysis (PCA), into few principal components (PC) that were used as proxies of the core metagenome. The PCA allowed us to condense the huge and fuzzy taxonomical and functional information from the metagenome into a few PC. Bivariate animal models were applied using these PC and methane production as phenotypes. The variability condensed in these PC is controlled by the cow genome, with heritability estimates for the first PC of ~0.30 at all taxonomic levels, with a large probability (>83%) of the posterior distribution being >0.20 and with the 95% highest posterior density interval (95%HPD) not containing zero. Most genetic correlation estimates between PC1 and methane were large (≥0.70), with most of the posterior distribution (>82%) being >0.50 and with its 95%HPD not containing zero. Enteric methane production was positively associated with relative abundance of eukaryotes (protozoa and fungi) through the first component of the PCA at phylum, class, order, family, and genus. Nanopore long reads allowed the characterization of the core rumen metagenome using whole-metagenome sequencing, and the purposed aggregated variables could be used in animal breeding programs to reduce methane emissions in future generations.  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