首页 | 官方网站   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   523888篇
  免费   8242篇
  国内免费   1501篇
工业技术   533631篇
  2021年   4957篇
  2020年   3547篇
  2019年   4610篇
  2018年   7887篇
  2017年   7693篇
  2016年   8020篇
  2015年   5667篇
  2014年   9413篇
  2013年   24375篇
  2012年   14867篇
  2011年   20395篇
  2010年   15999篇
  2009年   17884篇
  2008年   18279篇
  2007年   17953篇
  2006年   15670篇
  2005年   14306篇
  2004年   13697篇
  2003年   13485篇
  2002年   12707篇
  2001年   12884篇
  2000年   11920篇
  1999年   12646篇
  1998年   32941篇
  1997年   22889篇
  1996年   16872篇
  1995年   12967篇
  1994年   11218篇
  1993年   10929篇
  1992年   7842篇
  1991年   7335篇
  1990年   7221篇
  1989年   6909篇
  1988年   6387篇
  1987年   5679篇
  1986年   5587篇
  1985年   6200篇
  1984年   5843篇
  1983年   5102篇
  1982年   4826篇
  1981年   4913篇
  1980年   4658篇
  1979年   4559篇
  1978年   4364篇
  1977年   5287篇
  1976年   6920篇
  1975年   3753篇
  1974年   3506篇
  1973年   3634篇
  1972年   2958篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
71.
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...  相似文献   
72.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
73.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models.  相似文献   
74.
75.
76.
Programming and Computer Software - Image segmentation using a hierarchical sequence of piecewise constant approximations that minimally differ from the original image in terms of the total squared...  相似文献   
77.
78.
79.
80.
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies.  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-23

京公网安备 11010802026262号