全文获取类型
收费全文 | 557978篇 |
免费 | 7906篇 |
国内免费 | 1810篇 |
专业分类
电工技术 | 10096篇 |
综合类 | 2670篇 |
化学工业 | 81276篇 |
金属工艺 | 23536篇 |
机械仪表 | 20464篇 |
建筑科学 | 15474篇 |
矿业工程 | 2203篇 |
能源动力 | 13107篇 |
轻工业 | 48379篇 |
水利工程 | 5316篇 |
石油天然气 | 3849篇 |
武器工业 | 14篇 |
无线电 | 69779篇 |
一般工业技术 | 108349篇 |
冶金工业 | 85138篇 |
原子能技术 | 6958篇 |
自动化技术 | 71086篇 |
出版年
2021年 | 2833篇 |
2019年 | 2621篇 |
2018年 | 23581篇 |
2017年 | 23350篇 |
2016年 | 16651篇 |
2015年 | 4584篇 |
2014年 | 6276篇 |
2013年 | 20397篇 |
2012年 | 15399篇 |
2011年 | 30250篇 |
2010年 | 25369篇 |
2009年 | 24072篇 |
2008年 | 25635篇 |
2007年 | 28426篇 |
2006年 | 13483篇 |
2005年 | 16859篇 |
2004年 | 14518篇 |
2003年 | 13955篇 |
2002年 | 12234篇 |
2001年 | 11518篇 |
2000年 | 10746篇 |
1999年 | 11071篇 |
1998年 | 24307篇 |
1997年 | 17848篇 |
1996年 | 14196篇 |
1995年 | 11252篇 |
1994年 | 10006篇 |
1993年 | 9631篇 |
1992年 | 7355篇 |
1991年 | 6961篇 |
1990年 | 6584篇 |
1989年 | 6335篇 |
1988年 | 6023篇 |
1987年 | 5054篇 |
1986年 | 5003篇 |
1985年 | 6187篇 |
1984年 | 5811篇 |
1983年 | 5011篇 |
1982年 | 4670篇 |
1981年 | 4613篇 |
1980年 | 4353篇 |
1979年 | 4232篇 |
1978年 | 3909篇 |
1977年 | 4699篇 |
1976年 | 6206篇 |
1975年 | 3257篇 |
1974年 | 3148篇 |
1973年 | 2998篇 |
1972年 | 2414篇 |
1971年 | 2057篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
84.
V. A. Eremenko V. N. Karpov V. V. Timonin N. G. Barnov I. O. Shakhtorin 《Journal of Mining Science》2015,51(6):1113-1125
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed. 相似文献
85.
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,... 相似文献
86.
Evangelopoulos Xenophon Brockmeier Austin J. Mu Tingting Goulermas John Y. 《Machine Learning》2019,108(4):595-626
Machine Learning - We propose a set of highly scalable algorithms for the combinatorial data analysis problem of seriating similarity matrices. Seriation consists of finding a permutation of data... 相似文献
87.
88.
Few jurisdictions have translated internationally agreed social impact assessment (SIA) principles into statutory provisions. Governments and regulatory bodies tend to provide developers with high-level frameworks, or require that social impacts be ‘considered’, without specifying how this is to be done. In Australia, this lack of clarity leaves all parties uncertain about requirements for SIA. The New South Wales (NSW) Government’s 2017 release of the SIA guideline for State-significant mining, petroleum and extractive industry development represents an attempt to clarify requirements and provide guidance. In this paper, we describe the process of bringing this guideline to fruition from the perspective of being directly involved in its development, and highlight the challenges involved in integrating leading-practice principles into the state’s pre-existing policy framework. While the guideline represents a significant advance in policy-based SIA guidance, some aspects leave room for improvement. The real test of the guideline’s impact will lie in its influence on SIA practice in NSW, and ultimately in social outcomes for communities affected by resources projects. 相似文献
89.
J. Thomas BRENNA 《粮油食品科技》2022,30(3):7-15
人体大脑和身体的发育,需要从食物中摄取均衡的营养物质。人类大脑是区分人类和其他动物的特征。食物中的必需脂肪酸是机体组织结构和功能的必要组成部分。Omega-6(O6)亚油酸(LA6)是皮肤组织的组成成分,且是炎症、血栓形成、免疫和其他信号分子的前体;Omega-3(O3)α-亚麻酸(ALA3),特别是其长链代谢产物——二十二碳六烯酸(DHA3),是大脑、视网膜和部分神经组织中的关键组分。从富含LA6脂肪酸(缺乏O3脂肪酸)的植物籽中提取出的廉价而优质油脂,是20世纪的西方国家食品工业生产的主要脂肪来源。在代谢通路中,高浓度的LA6脂肪酸可拮抗O3脂肪酸代谢,造成O3脂肪酸不足,因此,在给怀孕动物的饲料中,只提供富含LA6但缺乏O3脂肪酸的油脂作为唯一的脂肪来源,会导致幼崽大脑发育不良。过去20~30年的研究表明,低含量LA6且含DHA3的油脂可改善大脑的功能。近年来的研究较多集中在营养因素对大脑发育的影响,最新研究数据表明,脂肪酸平衡对营养不良儿童的大脑发育尤为重要。世界卫生组织(WHO)越来越重视大脑的营养健康,通过其下属的食品法典委员会,建议用于治疗严重急性营养不良儿童的即食治疗食品中,使用含有均衡脂肪酸组成/构成的脂肪。同样,脂肪酸均衡对老年人可能也很重要。目前,业界已经有了调整油脂成分的方法,以确保脂肪酸均衡,从而维持人体整个生命周期的大脑健康。 相似文献
90.
P. Carrasqueira H. Rocha J. M. Dias T. Ventura B. C. Ferreira M. C. Lopes 《International Transactions in Operational Research》2023,30(1):206-223
Radiation therapy is a technology-driven cancer treatment modality that has experienced significant advances over the last decades, due to multidisciplinary contributions that include engineering and computing. Recent technological developments allow the use of noncoplanar volumetric modulated arc therapy (VMAT), one of the most recent photon treatment techniques, in clinical practice. In this work, an automated noncoplanar arc trajectory optimization framework designed in two modular phases is presented. First, a noncoplanar beam angle optimization algorithm is used to obtain a set of noncoplanar irradiation directions. Then, anchored in these directions, an optimization strategy is proposed to compute an optimal arc trajectory. The computational experiments considered a pool of twelve difficult head-and-neck tumor cases. It was possible to observe that, for some of these cases, the optimized noncoplanar arc trajectories led to significant treatment planning quality improvements, when compared with coplanar VMAT treatment plans. Although these experiments were done in a research environment treatment planning software (matRad), the conclusions can be of interest for a clinical setting: automated procedures can simplify the current treatment workflow, produce high-quality treatment plans, making better use of human resources and allowing for unbiased comparisons between different treatment techniques. 相似文献