全文获取类型
收费全文 | 73492篇 |
免费 | 5400篇 |
国内免费 | 2782篇 |
专业分类
电工技术 | 3880篇 |
技术理论 | 6篇 |
综合类 | 4427篇 |
化学工业 | 12692篇 |
金属工艺 | 3951篇 |
机械仪表 | 4804篇 |
建筑科学 | 5190篇 |
矿业工程 | 2405篇 |
能源动力 | 2231篇 |
轻工业 | 4776篇 |
水利工程 | 1000篇 |
石油天然气 | 5279篇 |
武器工业 | 460篇 |
无线电 | 7654篇 |
一般工业技术 | 9434篇 |
冶金工业 | 3932篇 |
原子能技术 | 750篇 |
自动化技术 | 8803篇 |
出版年
2024年 | 301篇 |
2023年 | 1263篇 |
2022年 | 2106篇 |
2021年 | 2905篇 |
2020年 | 2201篇 |
2019年 | 1963篇 |
2018年 | 2304篇 |
2017年 | 2506篇 |
2016年 | 2077篇 |
2015年 | 2698篇 |
2014年 | 3438篇 |
2013年 | 4217篇 |
2012年 | 4348篇 |
2011年 | 4856篇 |
2010年 | 4171篇 |
2009年 | 3950篇 |
2008年 | 3850篇 |
2007年 | 3710篇 |
2006年 | 3793篇 |
2005年 | 3430篇 |
2004年 | 2283篇 |
2003年 | 2083篇 |
2002年 | 1869篇 |
2001年 | 1636篇 |
2000年 | 1799篇 |
1999年 | 2048篇 |
1998年 | 1767篇 |
1997年 | 1425篇 |
1996年 | 1406篇 |
1995年 | 1186篇 |
1994年 | 958篇 |
1993年 | 717篇 |
1992年 | 546篇 |
1991年 | 428篇 |
1990年 | 327篇 |
1989年 | 254篇 |
1988年 | 226篇 |
1987年 | 142篇 |
1986年 | 120篇 |
1985年 | 96篇 |
1984年 | 66篇 |
1983年 | 40篇 |
1982年 | 42篇 |
1981年 | 30篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1945年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
FacetAtlas: multifaceted visualization for rich text corpora 总被引:1,自引:0,他引:1
Cao N Sun J Lin YR Gotz D Liu S Qu H 《IEEE transactions on visualization and computer graphics》2010,16(6):1172-1181
Documents in rich text corpora usually contain multiple facets of information. For example, an article about a specific disease often consists of different facets such as symptom, treatment, cause, diagnosis, prognosis, and prevention. Thus, documents may have different relations based on different facets. Powerful search tools have been developed to help users locate lists of individual documents that are most related to specific keywords. However, there is a lack of effective analysis tools that reveal the multifaceted relations of documents within or cross the document clusters. In this paper, we present FacetAtlas, a multifaceted visualization technique for visually analyzing rich text corpora. FacetAtlas combines search technology with advanced visual analytical tools to convey both global and local patterns simultaneously. We describe several unique aspects of FacetAtlas, including (1) node cliques and multifaceted edges, (2) an optimized density map, and (3) automated opacity pattern enhancement for highlighting visual patterns, (4) interactive context switch between facets. In addition, we demonstrate the power of FacetAtlas through a case study that targets patient education in the health care domain. Our evaluation shows the benefits of this work, especially in support of complex multifaceted data analysis. 相似文献
992.
Sun Wen Lu Yan Wu Feng Li Shipeng Tardif John 《IEEE transactions on visualization and computer graphics》2010,16(1):57-69
In this paper, we propose a novel approach for high-dynamic-range (HDR) texture compression (TC) suitable for rendering systems of different capacities. Based on the previously proposed DHTC scheme, we first work out an improved joint-channel compression framework, which is robust and flexible enough to provide compressed HDR textures at different bit rates. Then, two compressed HDR texture formats based on the proposed framework are developed. The 8 bpp format is of near lossless visual quality, improving upon known state-of-the-art algorithms. And, to our knowledge, the 4 bpp format is the first workable 4 bpp solution with good quality. We also show that HDR textures in the proposed 4 bpp and 8 bpp formats can compose a layered architecture in the texture consumption pipeline, to significantly save the memory bandwidth and storage in real-time rendering. In addition, the 8 bpp format can also be used to handle traditional low dynamic range (LDR) RGBA textures. Our scheme exhibits a practical solution for compressing HDR textures at different rates and LDR textures with alpha maps. 相似文献
993.
The knowledge economy offers opportunity to a broad and diverse community of information systems users to efficiently gain
information and know-how for improving qualifications and enhancing productivity in the work place. Such demand will continue
and users will frequently require optimised and personalised information content. The advancement of information technology
and the wide dissemination of information endorse individual users when constructing new knowledge from their experience in
the real-world context. However, a design of personalised information provision is challenging because users’ requirements
and information provision specifications are complex in their representation. The existing methods are not able to effectively
support this analysis process. This paper presents a mechanism which can holistically facilitate customisation of information
provision based on individual users’ goals, level of knowledge and cognitive styles preferences. An ontology model with embedded
norms represents the domain knowledge of information provision in a specific context where users’ needs can be articulated
and represented in a user profile. These formal requirements can then be transformed onto information provision specifications
which are used to discover suitable information content from repositories and pedagogically organise the selected content
to meet the users’ needs. The method is provided with adaptability which enables an appropriate response to changes in users’
requirements during the process of acquiring knowledge and skills. 相似文献
994.
Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study
Roland Kröbel Qinping Sun Joachim Ingwersen Xinping Chen Fusuo Zhang Torsten Müller Volker Römheld 《Environmental Modelling & Software》2010,25(4):583-601
The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richard's equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes. 相似文献
995.
996.
Ruijuan Zheng Mingchuan Zhang Qingtao Wu Shibao Sun Jiexin Pu 《International Journal of Information Security》2010,9(1):1-17
With the rapid development of network technologies and deteriorating of network environment, traditional single-net security
system cannot satisfy the security requirement. The excellent security performance of biological systems impels the bio-inspired
network security theory to be a hot research area currently. Based on Bio-inspired Multidimensional Network Security Model
we have put forward, we have advanced Bio-inspired Multi-Net Security system by implementing the functional distribution of
different subnets of different transient states in Multi-Net Paralleling structure. Firstly, parameter estimation and modified
algorithms of Hidden Markov Model are introduced to construct the mathematical mode of B-MNS; secondly, the integrated performance
of our modified B-MNS has been tested and its simulation has been carried out. So the feasibility, validity and high efficiency
of our model have been demonstrated theoretically, and practically. 相似文献
997.
针对船舶数字化和指针式复示器直观的特点,设计了不含大变比机械齿轮和不需人工基准位置调节的具有IEC61162标准数字信号输入的航向和舵角一体化指针式复示器;分析复示器的信号流后指出,其本质是由航向外表盘、航向内表盘和舵角指针组成的三个位置随动控制系统;设计了以步进电机为执行器和以步进脉冲计数进行位置估计和在基准位置点通过霍尔元件和永久磁铁进行精确位置测量相结合的控制方案;复示器采用了C8051F023单片机,通过其片上模拟差分输入和线性霍尔元件实现了刻度盘基准位置的精确测量;通过其片上PCA和中断程序实现了电子齿轮;试验表明,该复示器设计稳定可靠,具有较高的性价比。 相似文献
998.
北斗2代卫星导航电文纠错校验设计与仿真 总被引:1,自引:1,他引:0
提出了一种制表映射的BCH纠错解码和校验方法,通过对RNSS-ICD文档北斗导航电文BCH编码的深入理解,设计出了一种占用CPU资源少、实现简单方便的制表映射的编码和纠错解码算法,减小了算法在实现时对CPU和内存资源的占用;给出了一种再编码校验的校验方法仿真验证了该算法的准确性和可靠性,保证导航电文的可靠性;对提高接收机的性能具有很强的工程适用价值. 相似文献
999.
孙宁 《计算机与数字工程》2010,38(1):52-57
提出了基于GA的多路径测试数据生成的概念和实现方法。讨论了为了实现多路径测试数据生成,设计有效的和高效的适配函数应考虑的因素,用实际案例针对提出的适配函数进行了功能性能验证。结果表明了适配函数设计的有效性。 相似文献
1000.
Matlab在防护工程伪装效果评价中的应用 总被引:1,自引:0,他引:1
针对防护工程伪装效果优劣问题,给出了一种利用matlab来评价防护工程伪装效果的方法。通过分析防护工程伪装效果评价的总体架构,分别利用matlab的图像处理工具箱、统计学工具箱以及矩阵运算功能建立相关模块。实现了遥感数字图像处理、层次聚类构建指标体系、AHP确定指标权重和灰色聚类评价功能。最后通过一个实例证实运用该方法能较好满足防护工程口部伪装效果评价的需求。 相似文献