全文获取类型
收费全文 | 435503篇 |
免费 | 8266篇 |
国内免费 | 1404篇 |
专业分类
电工技术 | 7888篇 |
综合类 | 361篇 |
化学工业 | 67116篇 |
金属工艺 | 14637篇 |
机械仪表 | 12361篇 |
建筑科学 | 12311篇 |
矿业工程 | 927篇 |
能源动力 | 11544篇 |
轻工业 | 48084篇 |
水利工程 | 3526篇 |
石油天然气 | 1923篇 |
武器工业 | 18篇 |
无线电 | 56305篇 |
一般工业技术 | 80344篇 |
冶金工业 | 79884篇 |
原子能技术 | 5650篇 |
自动化技术 | 42294篇 |
出版年
2021年 | 3316篇 |
2020年 | 2398篇 |
2019年 | 3086篇 |
2018年 | 4921篇 |
2017年 | 4901篇 |
2016年 | 5247篇 |
2015年 | 4294篇 |
2014年 | 6670篇 |
2013年 | 21198篇 |
2012年 | 11668篇 |
2011年 | 15973篇 |
2010年 | 12376篇 |
2009年 | 13835篇 |
2008年 | 14829篇 |
2007年 | 15151篇 |
2006年 | 13360篇 |
2005年 | 12453篇 |
2004年 | 12026篇 |
2003年 | 11693篇 |
2002年 | 11307篇 |
2001年 | 11387篇 |
2000年 | 10525篇 |
1999年 | 11038篇 |
1998年 | 25429篇 |
1997年 | 18542篇 |
1996年 | 14509篇 |
1995年 | 11359篇 |
1994年 | 10046篇 |
1993年 | 9697篇 |
1992年 | 7242篇 |
1991年 | 6919篇 |
1990年 | 6496篇 |
1989年 | 6218篇 |
1988年 | 5966篇 |
1987年 | 4982篇 |
1986年 | 4917篇 |
1985年 | 6074篇 |
1984年 | 5678篇 |
1983年 | 4894篇 |
1982年 | 4575篇 |
1981年 | 4536篇 |
1980年 | 4293篇 |
1979年 | 4124篇 |
1978年 | 3814篇 |
1977年 | 4710篇 |
1976年 | 6459篇 |
1975年 | 3147篇 |
1974年 | 3047篇 |
1973年 | 2932篇 |
1972年 | 2335篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Gerd J. Hahn 《国际生产研究杂志》2020,58(5):1425-1441
The Fourth Industrial Revolution – also known as Industry 4.0 (i4.0) – comprises the digitalisation of the industrial sector. This paper uses the theoretical lens of supply chain innovation (SCI) to investigate the implications of i4.0 on supply chain management. For these purposes, the method of structured content analysis is applied to more than 200 use cases of i4.0-enabled SCI introduced by both established and startup companies. i4.0-enabled SCI manifests along three dimensions: process, technology, and business architecture. The key findings of this study can be summarised as follows: first, i4.0-enabled SCI extends the initial focus on productivity improvements in SC processes towards scalability and flexibility. Second, extant i4.0 solutions rely mostly on analytics and smart things while omitting smart people technology and the human-centric approach associated with the i4.0 paradigm. Third, established companies adopt i4.0 merely to sustain their existing business architectures while startup companies radically change their operating models, relying heavily on data analytics and the platform economy. Consequently, established companies pursue a problem-driven, engineering-based approach to SCI while startup companies follow an ‘asset-light’, business-driven approach. Lastly, there are two distinct approaches to digitalising operational SC processes: platform-based crowdsourcing of standard processes and on-demand provision of customised services. 相似文献
42.
43.
44.
45.
Wojciech Jó?wicki Anna A. Bro?yna Jerzy Siekiera Andrzej T. Slominski 《International journal of molecular sciences》2015,16(2):3783-3803
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape. 相似文献
46.
47.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage 下载免费PDF全文
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
48.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
49.
Kevin J. Hanley 《International journal for numerical methods in engineering》2020,121(21):4865-4877
An algorithm is presented for discrete element method simulations of energy-conserving systems of frictionless, spherical particles in a reversed-time frame. This algorithm is verified, within the limits of round-off error, through implementation in the LAMMPS code. Mechanisms for energy dissipation such as interparticle friction, damping, rotational resistance, particle crushing, or bond breakage cannot be incorporated into this algorithm without causing time irreversibility. This theoretical development is applied to critical-state soil mechanics as an exemplar. It is shown that the convergence of soil samples, which differ only in terms of their initial void ratio, to the same critical state requires the presence of shear forces and frictional dissipation within the soil system. 相似文献