全文获取类型
收费全文 | 225391篇 |
免费 | 19913篇 |
国内免费 | 9948篇 |
专业分类
电工技术 | 14205篇 |
技术理论 | 30篇 |
综合类 | 22770篇 |
化学工业 | 27493篇 |
金属工艺 | 9548篇 |
机械仪表 | 11515篇 |
建筑科学 | 33414篇 |
矿业工程 | 14184篇 |
能源动力 | 8290篇 |
轻工业 | 16564篇 |
水利工程 | 11215篇 |
石油天然气 | 12192篇 |
武器工业 | 3211篇 |
无线电 | 14148篇 |
一般工业技术 | 16453篇 |
冶金工业 | 11624篇 |
原子能技术 | 1666篇 |
自动化技术 | 26730篇 |
出版年
2024年 | 1038篇 |
2023年 | 2990篇 |
2022年 | 5706篇 |
2021年 | 7505篇 |
2020年 | 7337篇 |
2019年 | 5503篇 |
2018年 | 5170篇 |
2017年 | 6512篇 |
2016年 | 7889篇 |
2015年 | 8514篇 |
2014年 | 15580篇 |
2013年 | 13612篇 |
2012年 | 16314篇 |
2011年 | 17953篇 |
2010年 | 13230篇 |
2009年 | 13413篇 |
2008年 | 12261篇 |
2007年 | 14862篇 |
2006年 | 13514篇 |
2005年 | 11786篇 |
2004年 | 9824篇 |
2003年 | 8559篇 |
2002年 | 6936篇 |
2001年 | 5725篇 |
2000年 | 4903篇 |
1999年 | 3822篇 |
1998年 | 2719篇 |
1997年 | 2395篇 |
1996年 | 1942篇 |
1995年 | 1622篇 |
1994年 | 1365篇 |
1993年 | 989篇 |
1992年 | 789篇 |
1991年 | 545篇 |
1990年 | 475篇 |
1989年 | 440篇 |
1988年 | 243篇 |
1987年 | 198篇 |
1986年 | 164篇 |
1985年 | 185篇 |
1984年 | 136篇 |
1983年 | 114篇 |
1982年 | 60篇 |
1981年 | 75篇 |
1980年 | 81篇 |
1979年 | 42篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1975年 | 16篇 |
1959年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Chunnuan Ji Rongjun Qu Cheng Bo Cao Huo Chen Qiang Xu Changmei Sun Chunhua Wang Huafang Yuan Jun Zhou 《应用聚合物科学杂志》2006,102(6):6054-6059
A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg2+, Ag+, Cu2+, Zn2+, and Pb2+ at various pH values were determined. The maximum adsorption capacities for Hg2+ and Ag+ were 1.56 and 0.75 mmol g?1 respectively. The resin had high selectivity for Hg2+ and Ag+ over the pH range 1.0–7.0. The adsorption capacities for Hg2+ and Ag+ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg2+ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006 相似文献
82.
The HUB-CI model is investigated in a telerobotic system in a client/server network to manage the lifecycle of engineering design and prototyping. The purpose of this platform is to support collaborative engineering design and proof of concept to enhance distributed team collaboration and resource utilization. The suggested platform is exemplified in two collaboration support tools and a physical prototyping platform. Structured Co-Insight Management is developed to support innovative idea exchanges and the consensus decision-making during the design process. Conflict/error detection management helps preventing conflicts and errors during the lifecycle of design and development. Physical collaboration over the network occurs when a team controls the telerobot operation during prototyping and testing in design cycles. A pilot system is implemented with a group project for the design of an electronic circuit (including both hardware and software designs). The functional assessment method is used to compare this platform to other collaborative design tools. The system presented offers unique qualitative advantages as an integrated collaboration support system. 相似文献
83.
Visualization of pathlines is common and highly relevant for the analysis of unsteady flow. However, pathlines can intersect, leading to visual clutter and perceptual issues. This makes it intrinsically difficult to provide expressive visualizations of the entire domain by an arrangement of multiple pathlines, in contrast to well‐established streamline placement techniques. We present an approach to reduce these problems. It is inspired by glyph‐based visualization and small multiples: we partition the domain into cells, each corresponding to a downscaled version of the entire domain. Inside these cells, a single downscaled pathline is drawn. On the overview scale, our pathline glyphs lead to emergent visual patterns that provide insight into time‐dependent flow behavior. Zooming‐in allows us to analyze individual pathlines in detail and compare neighboring lines. The overall approach is complemented with a context‐preserving zoom lens and interactive pathline‐based exploration. While we primarily target the visualization of 2D flow, we also address the extension to 3D. Our evaluation includes several examples, comparison to other flow visualization techniques, and a user study with domain experts. 相似文献
84.
介绍了氟化氢吸收原理、流程 ,国内外氟化氢吸收设备的选型 ,满足工艺要求的穿流栅板塔的设计计算及应用。 相似文献
85.
在现代社会中,平板电脑、智能手机在人们日常生活的方方面面发挥着巨大的作用。通过分析电子产品在儿童和青少年的视力、身体发育、社交能力和学习能力等方面的负面影响,提出了加强亲子陪伴、合理引导控制等应对措施。 相似文献
86.
循环结构是C语言程序设计中的重难点,其掌握情况对于后续章节的学习效果尤为关键。本文以什么是循环、何时需要使用循环以及如何使用循环三个问题为主线,通过精心选择的教学案例和灵活有效的教学方法来进行解答,以激发学生兴趣,培养编程思想。 相似文献
87.
吴建功 《电子制作.电脑维护与应用》2014,(18)
经过60年的发展,陕西煤炭技工院校形成了以服务煤业为特色的专业结构和办学模式,为祖国煤炭发展做出了不可替代的贡献。近年来,由于煤炭市场遇冷,行业技校吸引力持续减弱,如何走出困境,重铸辉煌,作者从整合职教资源,调整管理职能,转换办学模式的角度进行了分析思考,或许能给陕煤技校改革发展提供一些有益参考。 相似文献
88.
针对"网络信息安全"教材建设的现状进行分析,提出建设基于工作流导向的任务式实训模式教材的必要性,并从教材的指导思想、整体结构、内容结构及其特色等方面进行了阐述。实践证明,该新型教材的建设和使用能够激发学生学习网络安全知识的兴趣,提升动手能力,有效提高教学质量和效率。 相似文献
89.
田利明 《精细与专用化学品》2003,11(20):8-9
20 0 2年我国染料及有机颜料生产和进出口数量达到历史最好水平 ,2 0 0 3年上半年虽然经受了SARS的影响 ,但我国染料及有机颜料工业仍然取得了稳定增长的成绩。上半年染料产量总计 19 5 9万t,同比增长 2 4 7%;颜料产量为 4 30万t,同比增长 2 1 6 9%。上半年出口增长幅度减缓 ,染料出口总量为 9 92万t,同比增长 3 1%;有机颜料出口为 4 2万t,同比增长 3 1%。进口基本稳定 ,上半年染料进口量为 3 2 5万t,同比增长 9 1%;有机颜料进口为1 6 9万t,同比增长为 11 5 %。总之 ,上半年主要经济指标完成情况良好 ,进出口数量和经济效益继续保持稳定增长。但染料和纺织品的生产与出口都遇到一定的困难 ,纺织品出口又直接影响染料的内销市场 ,由于内外市场的变化 ,使染料生产和进出口的增长幅度减缓。 相似文献
90.
We report a novel method of polyimide (PI) synthesis from prepolymers based on dianhydrides and diacetyl derivatives of aromatic diamines that facilitate the preparation of a melt processable mixture at 300 ± 10°C of the prepolymer and magnetic Nd‐Fe‐B alloy to provide PI‐bonded magnets with enhanced properties. It is shown that chemical structure of the prepolymers strongly influences viscosity behavior via crystallization of the oligoimide in the melt, leading to formation of PI with rigid‐rod like structure. This structural ordering of the prepolymers based on diacetyl derivative of diamine used in this study, if not controlled, leads to exponential increase of melt viscosity with time, making it practically impossible to prepare melt processable mixture of the magnetic particles and the PI prepolymers at elevated temperatures. The results obtained demonstrate that appropriate dianhydrides and diacetyl derivatives of diamines that do not lead to crystallization of oligoimides in prepolymer mixture can be used under controlled processing conditions to prepare melt‐processable PI‐bonded magnets containing rigid‐rod like PI structure that significantly increases thermal stability of the magnets. The temperature dependencies of the magnetic properties of the PI‐bonded magnets under conditions that they are likely to encounter during their service life were found to be remarkably similar to that of commercial thermoplastic magnets such as injection‐molded nylon magnets. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 478–485, 2006 相似文献