全文获取类型
收费全文 | 55562篇 |
免费 | 14277篇 |
国内免费 | 922篇 |
专业分类
电工技术 | 1826篇 |
综合类 | 1309篇 |
化学工业 | 19683篇 |
金属工艺 | 1153篇 |
机械仪表 | 1676篇 |
建筑科学 | 2693篇 |
矿业工程 | 401篇 |
能源动力 | 1565篇 |
轻工业 | 8371篇 |
水利工程 | 627篇 |
石油天然气 | 541篇 |
武器工业 | 99篇 |
无线电 | 9051篇 |
一般工业技术 | 13223篇 |
冶金工业 | 1499篇 |
原子能技术 | 238篇 |
自动化技术 | 6806篇 |
出版年
2024年 | 47篇 |
2023年 | 189篇 |
2022年 | 434篇 |
2021年 | 756篇 |
2020年 | 1767篇 |
2019年 | 3479篇 |
2018年 | 3408篇 |
2017年 | 3786篇 |
2016年 | 4250篇 |
2015年 | 4470篇 |
2014年 | 4595篇 |
2013年 | 5934篇 |
2012年 | 3764篇 |
2011年 | 3468篇 |
2010年 | 3661篇 |
2009年 | 3500篇 |
2008年 | 3050篇 |
2007年 | 2868篇 |
2006年 | 2539篇 |
2005年 | 2107篇 |
2004年 | 2040篇 |
2003年 | 2096篇 |
2002年 | 2314篇 |
2001年 | 1980篇 |
2000年 | 1551篇 |
1999年 | 822篇 |
1998年 | 314篇 |
1997年 | 285篇 |
1996年 | 247篇 |
1995年 | 150篇 |
1994年 | 118篇 |
1993年 | 119篇 |
1992年 | 82篇 |
1991年 | 97篇 |
1990年 | 64篇 |
1989年 | 62篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 36篇 |
1984年 | 17篇 |
1983年 | 23篇 |
1982年 | 25篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 18篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
电子政务信息资源库建设研究 总被引:3,自引:2,他引:3
目前,电子政务系统几乎都是彼此隔离的信息系统,如何集成系统内各应用系统和数据资源,架构一个统一电子政务平台,实现资源共享,成为提高电子政务整体应用水平的关键.讨论了电子政务数据集成平台系统的设计和应用,系统基于Web Service体系结构,利用Oracle 10g强大的数据集成和管理能力,通过全面集成各种格式的数据和分散的业务系统,基于政务信息资源库,解决了政府部门之间信息系统难以一体化的问题. 相似文献
994.
Applying case-based reasoning for product configuration in mass customization environments 总被引:14,自引:0,他引:14
Product variation and customization is a trend in current market-oriented manufacturing environment. Companies produce products in order to satisfy customer's needs. In the customization environment, the R&D sector in an enterprise should be able to offer differentiation in product selection after they take the order. Such product differentiation should meet the requirement of cost and manufacturing procedure. In the light of this, how to generate an accurate bill of material (BOM) that meets the customer's needs and gets ready for the production is an important issue in the intensely competitive market.
The purpose of this study is to reduce effectively the time and cost of design under the premise to manufacture an accurate new product. In this study, the Case-Based Reasoning (CBR) algorithm was used to construct the new BOM. Retrieving previous cases that resemble the current problem can save a lot of time in figuring out the problem and offer a correct direction for designers. When solving a new problem, CBR technique can quickly help generate a right BOM that fits the present situation. 相似文献
995.
Sung Kim Bastani F.B. I-Ling Yen Chen I.-R. 《IEEE transactions on pattern analysis and machine intelligence》2004,30(4):218-230
Dramatic advances in computer and communication technologies have made it economically feasible to extend the use of embedded computer systems to more and more critical applications. At the same time, these embedded computer systems are becoming more complex and distributed. As the bulk of the complex application-specific logic of these systems is realized by software, the need for certifying software systems has grown substantially. While relatively mature techniques exist for certifying hardware systems, methods of rigorously certifying software systems are still being actively researched. Possible certification methods for embedded software systems range from formal verification to statistical testing. These methods have different strengths and weaknesses and can be used to complement each other. One potentially useful approach is to decompose the specification into distinct aspects that can be independently certified using the method that is most effective for it. Even though substantial-research has been carried out to reduce the complexity of the software system through decomposition, one major hurdle is the need to certify the overall system on the basis of the aspect properties. One way to address this issue is to focus on architectures in which the aspects are relatively independent of each other. However, complex embedded systems are typically comprised of multiple architectures. We present an alternative approach based on the use of application-oriented-frameworks for implementing embedded systems. We show that it is possible to design such frameworks for embedded applications and derive expressions for determining the system reliability from the reliabilities of the framework and the aspects. The method is illustrated using a distributed multimedia collaboration system. 相似文献
996.
Bas‐relief is designed to provide 3D perception for the viewers under illumination. For the problem of bas‐relief generation from 3D object, most existing methods ignore the influence of illumination on bas‐relief appearance. In this paper, we propose a novel method that adaptively generate bas‐reliefs with respect to illumination conditions. Given a 3D object and its target appearance, our method finds an adaptive surface that preserves the appearance of the input. We validate our approach through a variety of applications. Experimental results indicate that the proposed approach is effective in producing bas‐reliefs with desired appearance under illumination. 相似文献
997.
Traditional adaptive event‐triggered design methods compensated for the event‐triggered error are not direct, and the stability analysis of resulting close‐loop systems is rather complicated. To alleviate the above restrictions, we propose a direct and simple event‐triggered co‐design method to solve the tracking control problem for parameter strict‐feedback systems with actuator faults and uncertain disturbances. By introducing a compensating terms in a smooth function form of a conventional control law and certain positive integrable functions, the effects of actuator faults and event‐triggered error can be compensated completely. Such a direct design method has the following features: (i) a direct compensation of the event‐triggered error is achieved without introducing any extra design parameters; (ii) it is not necessary to know any bound information on the parameters of event‐triggered threshold, and global asymptotic tracking control of the overall closed‐loop system is achieved; and (iii) the resulting stability criteria of the proposed event‐triggered control design are much simpler and easier to fulfill by virtue of the introduced co‐design method. Simulations are then carried out to validate the proposed schemes. 相似文献
998.
A 3D‐printed cylindrical Luneburg lens antenna working at 26 GHz is proposed in this article. The antenna consists of a feeding waveguide, a 3D‐printed cylinder, and a pair of printed metal grids which are stuck on the side faces of the cylinder. 3D‐printed structure ensures the convenience for processing and structural integrity of the Luneburg lens. Hole drilling technology is utilized for the design of the cylindrical lens. In the E‐plane, conversion of spherical waves into planar waves is achieved based on the gradient refractive index which is realized by the gradient equivalent relative dielectric constant. The main part of the lens contains a hole drilling region to realize the desired equivalent permittivity from 1.23 to 2, while another gradual‐thickness region realize the permittivity ranges from 1.23 to 1. H‐probe method is utilized for the optimization of the gradual‐thickness region in this article. And for the H‐plane, with the grids, H‐field distribution is optimized compared with the Luneburg lens antenna without the loading grids. Thus, the side lobe level (SLL) in H‐plane could be reduced. Meanwhile, a narrower half power beamwidth (HPBW) in H‐plane will be obtained due to the metal grids. Experiment results illustrate the feasibility and validity of the proposed 3D‐printed cylindrical Luneburg lens antenna. 相似文献
999.
This paper presents a variational algorithm for feature‐preserved mesh denoising. At the heart of the algorithm is a novel variational model composed of three components: fidelity, regularization and fairness, which are specifically designed to have their intuitive roles. In particular, the fidelity is formulated as an L1 data term, which makes the regularization process be less dependent on the exact value of outliers and noise. The regularization is formulated as the total absolute edge‐lengthed supplementary angle of the dihedral angle, making the model capable of reconstructing meshes with sharp features. In addition, an augmented Lagrange method is provided to efficiently solve the proposed variational model. Compared to the prior art, the new algorithm has crucial advantages in handling large scale noise, noise along random directions, and different kinds of noise, including random impulsive noise, even in the presence of sharp features. Both visual and quantitative evaluation demonstrates the superiority of the new algorithm. 相似文献
1000.
认知决策引擎是认知无线电(Cognitive Radio,CR)的核心。为适应CR参数的自适应重配置,提出了一种改进的二进制人工蜂群(Binary Artificial Bee Colony algorithm,BABC)算法。该算法在基本BABC算法的基础上,加入了反向学习初始化机制、混合编码规则以及社会认知策略,保证了个体的多样性、提高了搜索速度。给出了该算法的基本步骤,并在多载波通信系统中对算法性能进行了仿真。仿真结果表明,基于该算法的CR认知决策引擎的收敛速度和精度均优于经典的遗传算法(Genetic Algorithm,GA)和BABC算法,优化得到的系统参数具有更好的性能。 相似文献