全文获取类型
收费全文 | 1406685篇 |
免费 | 24845篇 |
国内免费 | 6878篇 |
专业分类
电工技术 | 33801篇 |
综合类 | 6326篇 |
化学工业 | 266105篇 |
金属工艺 | 62663篇 |
机械仪表 | 38932篇 |
建筑科学 | 43899篇 |
矿业工程 | 11215篇 |
能源动力 | 50038篇 |
轻工业 | 99492篇 |
水利工程 | 13928篇 |
石油天然气 | 37229篇 |
武器工业 | 128篇 |
无线电 | 193130篇 |
一般工业技术 | 266639篇 |
冶金工业 | 116806篇 |
原子能技术 | 33637篇 |
自动化技术 | 164440篇 |
出版年
2021年 | 15404篇 |
2020年 | 11685篇 |
2019年 | 14449篇 |
2018年 | 13686篇 |
2017年 | 12848篇 |
2016年 | 20145篇 |
2015年 | 17059篇 |
2014年 | 28430篇 |
2013年 | 87333篇 |
2012年 | 32449篇 |
2011年 | 43070篇 |
2010年 | 40100篇 |
2009年 | 49150篇 |
2008年 | 40905篇 |
2007年 | 37536篇 |
2006年 | 42283篇 |
2005年 | 36496篇 |
2004年 | 39206篇 |
2003年 | 39311篇 |
2002年 | 38766篇 |
2001年 | 34970篇 |
2000年 | 33860篇 |
1999年 | 32123篇 |
1998年 | 29953篇 |
1997年 | 30218篇 |
1996年 | 29484篇 |
1995年 | 27269篇 |
1994年 | 26066篇 |
1993年 | 25970篇 |
1992年 | 25293篇 |
1991年 | 22187篇 |
1990年 | 22641篇 |
1989年 | 21722篇 |
1988年 | 20162篇 |
1987年 | 18576篇 |
1986年 | 17872篇 |
1985年 | 21236篇 |
1984年 | 21843篇 |
1983年 | 19822篇 |
1982年 | 18953篇 |
1981年 | 19008篇 |
1980年 | 17570篇 |
1979年 | 18196篇 |
1978年 | 17444篇 |
1977年 | 16546篇 |
1976年 | 16411篇 |
1975年 | 15784篇 |
1974年 | 15319篇 |
1973年 | 15380篇 |
1972年 | 12856篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Test Case Generation as an AI Planning Problem 总被引:6,自引:0,他引:6
Adele E. Howe Anneliese von Mayrhauser Richard T. Mraz 《Automated Software Engineering》1997,4(1):77-106
While Artificial Intelligence techniques have been applied to a variety of software engineering applications, the area of automated software testing remains largely unexplored. Yet, test cases for certain types of systems (e.g., those with command language interfaces and transaction based systems) are similar to plans. We have exploited this similarity by constructing an automated test case generator with an AI planning system at its core. We compared the functionality and output of two systems, one based on Software Engineering techniques and the other on planning, for a real application: the StorageTek robot tape library command language. From this, we showed that AI planning is a viable technique for test case generation and that the two approaches are complementary in their capabilities. 相似文献
902.
C. Ebert presents his views on the state of software engineering as a field, its roots and inherent conflicts, its relationship to other engineering disciplines, where it is headed, and what we can do to influence that direction. T. Matsubara, T. Webb, M. Pezze, and O.W. Bertelsen offer a spectrum of further insights 相似文献
903.
Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong 总被引:1,自引:1,他引:0
At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead. 相似文献
904.
Results are reported of a detailed optical and electron metallographic study of the effects of variations in quenching rate from the β-phase and aging temperature in the + ZrCr2 phase region, on the recrystallization and grain growth characteristics of Zr-1.14 wt% Cr-0.08 wt% Fe alloy used for nuclear fuel sheathing. It is shown that certain quenching rates, which produce a mixed martensitic-Widmanstätten structure, should be avoided during the fabrication of fuel sheathing, since recrystallization and grain growth occurs at a much lower temperature than a material quenched at such a rate that the structure is wholly Widmanstätten or wholly martensitic. Preaging at 350 or 450°C prior to the high-temperature (700–750°C) aging reduces the incidence of recrystallization and grain growth. 相似文献
905.
Noel E. Sharkey 《Robotics and Autonomous Systems》1997,22(3-4):345-359
It is time to locate connectionist representation theory in the new wave of robotics research. The utility of representations developed in artificial neural networks (ANNs) during learning has been demonstrated in cognitive science research since the 1980s. The research reported here puts learned representations to work in a decentered control task, the disembodied arm problem, in which a mobile robot operates an arm fixed to a table to pick up objects. There is no physical linkage between the arm and the robot and so the robot's point of view must be decentered. This is done by developing a modular Artificial Neural Net system in three stages: (i) a classifier net is trained with laser scan data to output transformationally invariant position classes; (ii) an arm net is trained for picking up objects; (iii) an inter net is trained to communicate and coordinate the sensing and acting. The completed system is shown to create new nonsymbolic transformationally invariant representations in order to perform the effective generalization of decentered viewpoints. 相似文献
906.
This paper is concerned with partially observed stochastic optimal control problems when nonlinearities enter the dynamics of the unobservable state and the observations as gradients of potential functions. Explicit representations for the information state are derived in terms of a finite number of sufficient statistics. Consequently, the partially observed problem is recast as one of complete information with a new state generated by a modified version of the Kalman filter. When the terminal cost is quadratic in the unobservable state and includes the integral of the nonlinearities, the optimal control laws are explicitly computed, similar to linear-exponential-quadratic-Gaussian (LEQG) and linear-quadratic-Gaussian (LQG) tracking problems. The results are applicable to filtering and control of Hamiltonian systems 相似文献
907.
Lauren P.D. Nandhakumar N. 《IEEE transactions on pattern analysis and machine intelligence》1997,19(5):417-430
The ability to determine the viewing parameters of objects from their projections has enabled well established tomographic techniques to be employed in the 3D reconstruction of objects from images obtained via modalities where the orientation of the objects cannot be controlled. A method is described for the determination of the viewing parameters of randomly acquired projections of asymmetric objects. It extends upon the common lines algorithm by determining the relative orientation of projections from the location of lines of intersection among the Fourier transforms of the projections in 3D Fourier space. A new technique for finding the lines of intersection in the presence of translational displacement, and for subsequently finding the translational displacement, is presented. The complete algorithm is described and its efficacy is demonstrated using real data. A new technique for dealing with noise is also discussed 相似文献
908.
The aim of this paper is to give a general quantitative requirement which the loop gain must satisfy in order to stabilize a given unstable (possibly nonlinear and time-varying) plant, namely that the gain must exceed one. 相似文献
909.
910.