全文获取类型
收费全文 | 39896篇 |
免费 | 4195篇 |
国内免费 | 2814篇 |
专业分类
电工技术 | 2841篇 |
技术理论 | 8篇 |
综合类 | 6007篇 |
化学工业 | 3042篇 |
金属工艺 | 1012篇 |
机械仪表 | 2745篇 |
建筑科学 | 4302篇 |
矿业工程 | 1397篇 |
能源动力 | 1338篇 |
轻工业 | 552篇 |
水利工程 | 1125篇 |
石油天然气 | 977篇 |
武器工业 | 706篇 |
无线电 | 3710篇 |
一般工业技术 | 4693篇 |
冶金工业 | 2295篇 |
原子能技术 | 356篇 |
自动化技术 | 9799篇 |
出版年
2024年 | 154篇 |
2023年 | 622篇 |
2022年 | 811篇 |
2021年 | 1039篇 |
2020年 | 1204篇 |
2019年 | 1118篇 |
2018年 | 1170篇 |
2017年 | 1331篇 |
2016年 | 1441篇 |
2015年 | 1478篇 |
2014年 | 2267篇 |
2013年 | 2757篇 |
2012年 | 2560篇 |
2011年 | 2916篇 |
2010年 | 2287篇 |
2009年 | 2420篇 |
2008年 | 2478篇 |
2007年 | 2659篇 |
2006年 | 2465篇 |
2005年 | 2165篇 |
2004年 | 1741篇 |
2003年 | 1445篇 |
2002年 | 1250篇 |
2001年 | 1009篇 |
2000年 | 884篇 |
1999年 | 760篇 |
1998年 | 610篇 |
1997年 | 545篇 |
1996年 | 451篇 |
1995年 | 427篇 |
1994年 | 355篇 |
1993年 | 300篇 |
1992年 | 280篇 |
1991年 | 206篇 |
1990年 | 165篇 |
1989年 | 180篇 |
1988年 | 142篇 |
1987年 | 74篇 |
1986年 | 97篇 |
1985年 | 69篇 |
1984年 | 68篇 |
1983年 | 51篇 |
1982年 | 53篇 |
1981年 | 42篇 |
1980年 | 31篇 |
1979年 | 32篇 |
1978年 | 29篇 |
1977年 | 26篇 |
1964年 | 26篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system. 相似文献
62.
C. S. Kubrusly 《Systems & Control Letters》1992,19(3)
A discrete system is uniformly mean-square stable if uniform convergence is preserved between input and state correlation sequences, and if nuclearity is preserved between the input and state correlation limits. This paper supplies a contraction-free condition ensuring mean-square stability for infinite-dimensional bilinear systems evolving in a separable Hilbert space. 相似文献
63.
This paper deals with the issues of development and implementation of a real-time NURBS interpolator for a six-axis robot. Using an open-architecture controller system as a testbed, a real-time NURBS curve interpolator was developed, implemented and tested. Sample runs were conducted with the resulting trajectories measured in real-time during robot motion. The resulting trajectories are analyzed, discussed and compared with those from a commonly used point-to-point approximation technique. The real-time NURBS curve interpolator's feasibility, advantages and related issues are also discussed. 相似文献
64.
We consider an integer-subset representation problem motivated by a medical application in radiation therapy. We prove NP-completeness, derive nontrivial bounds, and report on the performance of a greedy heuristic. 相似文献
65.
Robert Jenssen Author Vitae Deniz Erdogmus Author Vitae Author Vitae Jose C. Principe Author Vitae Author Vitae 《Pattern recognition》2007,40(3):796-806
We introduce a new graph cut for clustering which we call the Information Cut. It is derived using Parzen windowing to estimate an information theoretic distance measure between probability density functions. We propose to optimize the Information Cut using a gradient descent-based approach. Our algorithm has several advantages compared to many other graph-based methods in terms of determining an appropriate affinity measure, computational complexity, memory requirements and coping with different data scales. We show that our method may produce clustering and image segmentation results comparable or better than the state-of-the art graph-based methods. 相似文献
66.
67.
The infrastructure renewal program at MIT consists of a large number of projects with an estimated budget that could approach $1 billion. Infrastructure renewal at the Massachusetts Institute of Technology (MIT) is the process of evaluating and investing in the maintenance of facility systems and basic structure to preserve existing campus buildings. The selection and prioritization of projects must be addressed with a systematic method for the optimal allocation of funds and other resources. This paper presents a case study of a prioritization method utilizing multi-attribute utility theory. This method was developed at MIT's Department of Nuclear Engineering and was deployed by the Department of Facilities after appropriate modifications were implemented to address the idiosyncrasies of infrastructure renewal projects and the competing criteria and constraints that influence the judgment of the decision-makers. Such criteria include minimization of risk, optimization of economic impact, and coordination with academic policies, programs, and operations of the Institute. A brief overview of the method is presented, as well as the results of its application to the prioritization of infrastructure renewal projects. Results of workshops held at MIT with the participation of stakeholders demonstrate the feasibility of the prioritization method and the usefulness of this approach. 相似文献
68.
Vibrational mode in a two-dimensional dust monolayer is investigated by considering the finite size of dust grains. Each dust grain is assumed to be a negative point charge and a dipole moment due to the inhomogeneous charge distribution on its surface. The dispersion relation of the vibrational mode is derived. Both the self-excited and externally excited cases are discussed. It is shown that the mode is sensitive to the direction of the dipole moment. 相似文献
69.
根据啮合型同向旋转双螺杆挤出非充满熔融的理论模型,对描述非充满熔融过程的主要物理量:固相高度变化函数、熔融速率及熔融区总长等进行了计算分析,并对有关影响因素进行了讨论。 相似文献
70.
Li Yu-cheng Teng Bin 《水动力学研究与进展(B辑)》1993,(2)
By using Cokelet's wave theory,the limiting wave height and the relative waveangular frequency in wave-current field were calculated in this paper.It is indicated by numeri-cal calculation that if the water depth is not too small,the result given by authors'calculationare very close to the results of limiting wave height by Dalrymple(1975)and to the data of rel-ative wave angular frequency by linear wave theory;but if water depth is rather small,thereare some discrepancy, 相似文献