全文获取类型
收费全文 | 12107篇 |
免费 | 571篇 |
国内免费 | 259篇 |
专业分类
电工技术 | 264篇 |
综合类 | 430篇 |
化学工业 | 2025篇 |
金属工艺 | 453篇 |
机械仪表 | 512篇 |
建筑科学 | 1227篇 |
矿业工程 | 186篇 |
能源动力 | 745篇 |
轻工业 | 696篇 |
水利工程 | 299篇 |
石油天然气 | 318篇 |
武器工业 | 33篇 |
无线电 | 549篇 |
一般工业技术 | 2092篇 |
冶金工业 | 250篇 |
原子能技术 | 84篇 |
自动化技术 | 2774篇 |
出版年
2024年 | 19篇 |
2023年 | 175篇 |
2022年 | 192篇 |
2021年 | 278篇 |
2020年 | 315篇 |
2019年 | 352篇 |
2018年 | 361篇 |
2017年 | 437篇 |
2016年 | 488篇 |
2015年 | 496篇 |
2014年 | 601篇 |
2013年 | 1176篇 |
2012年 | 530篇 |
2011年 | 674篇 |
2010年 | 481篇 |
2009年 | 613篇 |
2008年 | 554篇 |
2007年 | 535篇 |
2006年 | 504篇 |
2005年 | 450篇 |
2004年 | 396篇 |
2003年 | 384篇 |
2002年 | 332篇 |
2001年 | 239篇 |
2000年 | 265篇 |
1999年 | 253篇 |
1998年 | 274篇 |
1997年 | 210篇 |
1996年 | 260篇 |
1995年 | 181篇 |
1994年 | 164篇 |
1993年 | 117篇 |
1992年 | 115篇 |
1991年 | 94篇 |
1990年 | 51篇 |
1989年 | 52篇 |
1988年 | 46篇 |
1987年 | 42篇 |
1986年 | 25篇 |
1985年 | 41篇 |
1984年 | 38篇 |
1983年 | 43篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1975年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
31.
32.
The efficient, economical and often elegant transformation from a design schema to an embodied design solution containing real components is essential for the commercial success of a product. More often the ability of the designer to explore an optimum solution is severely frustrated by the analytically intensive and time-consuming aspects of embodying a concept. This paper presents a computer based system-modelling tool that is to be used by designers during the transformation of a concept to an embodied solution particularly to deal with standard components. This environment provides for the representation of conceptual schemas and subsequent embodiment from computer based component selection modules. These selection modules encompass the full range of electronic representations for standard mechanical components. The strategy for representing a mechanical system, its included components and their associated representations is discussed. The process of constructing a system model, specifying the desired performance characteristics and system resolution are also described. 相似文献
33.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献
34.
一种用于卫星电视接收的FZP天线 总被引:1,自引:1,他引:0
本文用物理光学法对FZP反射器的聚焦场、聚焦效率及偏轴扫描特性等进行初步分析,并由此提出一种使用FZP天线实现多颗卫星信号同时接收的技术方案。原理性样机实际接收结果证实了其可行性 相似文献
35.
针对现有移动机器人路径规划中各种环境建模方法存在使用范围有限、复杂问题处理能力不足和运行效率低、缺乏灵活性等问题,结合二维半描述和知识利用原理,提出了一种可以比较圆满地解决诸如建筑物内不同楼层连接、室内室外环境交替出现等实用结构性空间问题的基于区域分割的多级环境建模方法。 相似文献
36.
代数应力模式的分析解及其在充分发展旋转管流中的应用 总被引:1,自引:0,他引:1
符松 《水动力学研究与进展(A辑)》1994,(6):689-693
本文通过求解雷诺应力在代数应力模式中与平均速度梯度之间的分析关系,研究了代数应力模式在涡旋流动特别是在充分发展旋转管流中存在的内在缺陷,这些缺陷的主要表现为:(1)在不考虑固壁对湍流影响的代数应力模式中,分析解给出W∝r和vw=0的错误结论;(2)若在代数应力模式中考虑固壁对湍流影响,在对称轴上会有v^2不等于w^2的非物理解。与诺应力输运模式相比,代数应力模式的缺陷归限结底在于该模式的基本假设不 相似文献
37.
Drying of textile bobbins was carried out on two kinds of laboratory-scale dryers: in a cross circulation drying rig, atmospheric pressure heating air is used, while in the through circulation drying apparatus, the heating air is pressurized before the drying process takes place. In both cases, a bobbin was fitted with seven thermocouples, placed in a plane normal to the bobbin axis but at different radial distances, in order to provide temperature data during the drying process. In cross circulation drying, plots of temperature against time indicated the presence of two moving fronts, one starting from inside the bobbin, another from the outside, while in through circulation drying, similar plots showed the presence of an evaporation front, moving from inside the bobbin to the outside. In both canes, numerical models were developed to simulate the drying processes. 相似文献
38.
Ben J. A. Kr se Kai M. Compagner Franciscus C. A. Groen 《Robotics and Autonomous Systems》1993,11(3-4):221-230
This paper describes a robust and accurate ultrasonic sensing system for a mobile robot. The system continuously updates a local map of the environment in which obstacles are represented by straight lines or points in a robot centered coordinate frame. The presented algorithms use a Kalman filter for the reduction of the noise in the ultrasonic data and use a systematical error correction (‘bundle correction’) to reduce the uncertainty in obstacle direction. Experiments are carried out in simulation and with a real mobile robot system. Results show that the accuracy with which line parameters can be estimated is in the order of 1 degree for the orientation and about 2 cm for the position. The effect of the bundle correction is significant and maximal when the robot approaches walls under a small angle. 相似文献
39.
In this paper, a unified method is presented: (i) to model delaminated stiffened laminated composite shells; (ii) for synthesising
accurate multiple post-buckling solution paths under compressive loading; and (iii) for predicting delamination growth. A
multi-domain modelling technique is used for modelling the delaminated stiffened shell structures. Error-free geometrically
nonlinear element formulations — a 2-noded curved stiffener element (BEAM2) and a 3-noded shell element (SHELL3) — are used
for the finite element analysis. An accurate and simple automated solution strategy based on Newton type iterations is used
for predicting the general geometrically nonlinear and postbuckling behaviour of structures. A simple method derived from
the 3-dimensionalJ-integral is used for computing the pointwise energy release rate at the delamination front in the plate/shell models. Finally,
the influence of post-buckling structural behaviour and the delamination growth on each other has been demonstrated. 相似文献
40.
The GILDES computer model, incorporating Stumm's concept of proton- and ligand-promoted dissolution, has been used to simulate the exposure of copper at room temperature to 210 ppb sulfur dioxide and 80% relative humidity. The agreement is good between the calculations and laboratory exposures performed under these exposure conditions. Surface reactions are relatively more important at lower relative humidities and the dominant corrosion products formed are solid state Cu2SO3, CuSO3 and Cu2U. Free-radical redox processes are important participants and control the relative distribution of Cu(I)- and Cu(H)-containing corrosion products. 相似文献