全文获取类型
收费全文 | 18128篇 |
免费 | 2609篇 |
国内免费 | 1730篇 |
专业分类
电工技术 | 2244篇 |
综合类 | 2249篇 |
化学工业 | 778篇 |
金属工艺 | 405篇 |
机械仪表 | 1488篇 |
建筑科学 | 2638篇 |
矿业工程 | 472篇 |
能源动力 | 247篇 |
轻工业 | 336篇 |
水利工程 | 381篇 |
石油天然气 | 651篇 |
武器工业 | 206篇 |
无线电 | 1774篇 |
一般工业技术 | 1086篇 |
冶金工业 | 682篇 |
原子能技术 | 84篇 |
自动化技术 | 6746篇 |
出版年
2024年 | 106篇 |
2023年 | 316篇 |
2022年 | 588篇 |
2021年 | 595篇 |
2020年 | 548篇 |
2019年 | 457篇 |
2018年 | 388篇 |
2017年 | 587篇 |
2016年 | 602篇 |
2015年 | 685篇 |
2014年 | 1090篇 |
2013年 | 953篇 |
2012年 | 1315篇 |
2011年 | 1473篇 |
2010年 | 1158篇 |
2009年 | 1171篇 |
2008年 | 1161篇 |
2007年 | 1393篇 |
2006年 | 1258篇 |
2005年 | 1016篇 |
2004年 | 938篇 |
2003年 | 850篇 |
2002年 | 757篇 |
2001年 | 645篇 |
2000年 | 573篇 |
1999年 | 428篇 |
1998年 | 304篇 |
1997年 | 260篇 |
1996年 | 183篇 |
1995年 | 140篇 |
1994年 | 133篇 |
1993年 | 90篇 |
1992年 | 61篇 |
1991年 | 50篇 |
1990年 | 43篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 7篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1957年 | 2篇 |
1956年 | 3篇 |
1955年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
The embedding of a small but expressive language of multidimensional functional programming in a well known and widely used language of object‐oriented programming leads to the combination of two radically different programming models. In this paper, we formally define the syntax and semantics of GLU?, which can be thought of as the multidimensional core of Lucid and GLU, and we describe its implementation as a language embedded in C++. With the aid of a few examples, we argue that the marriage of the two programming models is not only compatible and natural, but also that it produces a new and interesting hybrid language. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
42.
These experiments explored the role of prior experience in 12- to 18-month-old infants' tool-directed actions. In Experiment 1, infants' use of a familiar tool (spoon) to accomplish a novel task (turning on lights inside a box) was examined. Infants tended to grasp the spoon by its handle even when doing so made solving the task impossible (the bowl did not fit through the hole in the box, but the handle did) and even though the experimenter demonstrated a bowl-grasp. In contrast, infants used a novel tool flexibly and grasped both sides equally often. In Experiment 2, infants received training using the novel tool for a particular function; 3 groups of infants were trained to use the tool differently. Later, infants' performance was facilitated on tasks that required infants to grasp the part of the tool they were trained to grasp. The results suggest that (a) infants' prior experiences with tools are important to understanding subsequent tool use, and (b) rather than learning about tool function (e.g., hammering), infants learn about which part of the tool is meant to be held, at least early in their exposure to a novel tool. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Qing Li 《Computer Standards & Interfaces》1991,13(1-3):99-103
The term ‘object-oriented database’ has been used to refer to different characteristics and mechanisms supported by semantic databases and (behaviorally) object-oriented ones. While this indicates the current confusion due to the lack of a common model, it also suggests the potential desirability of combining these two kinds of modeling facilities into the same nutshell. This paper summarizes from these two paradigms the features common to both, the features influenced/adopted by each other, and the features which are presented in one paradigm but missing from the other. After a brief analysis and discussion of these features, we conclude this paper by proposing our major theme: a complete object data model should take the union of the facilities offered by these two kinds of models. 相似文献
44.
Huai Wen-xin Wuhan University of Hydraulic & Electric Engineering Wuhan Hubei P.R.China Prof.Li Wei 《水动力学研究与进展(B辑)》1993,(3)
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion. 相似文献
45.
46.
47.
本文基于静态相关性分析和动态调整相结合的方法,提出了一种逻辑程序的执行模型,它不仅开发了“与“并行,同进也开发了一定的“或“并行,从而有效地加速了逻辑程序的执行。 相似文献
48.
哈尔滨炼油厂MTBE装置试生产 总被引:4,自引:0,他引:4
介绍了哈尔滨炼油厂MTBE装置的工艺路线、新技术的应用及特点;催化剂的装填及应用情况;总结了生产过程中遇到的一系列问题及解决办法;探索了平稳生产的新徐径,以保证装置安全、平稳、长周期运行;同时对反应器操作温度、催化蒸馏塔操作压力、原料中醇烯比等因素对异丁烯转化率及MTBE产品的影响做了简单的总结。 相似文献
49.
工程应用中软件工具的多样性和设计活动的分散性形成了大量异构数据。本文分析了传统的异构数据管理方法的不足,提出使用数据库系统的文件系统结合的管理方法。针对此方法下所形成的异构数据源问题,给出了基于J2EE规范的数据访问对象抽象工厂解决方案。 相似文献
50.
Displacement Discontinuity Method for Fracture Mechanics Analysis of Reissner Plates: Static and Dynamic 总被引:1,自引:0,他引:1
This paper is concerned with the displacement discontinuity method applied to the shear deformable plates (Reissner’s and
Mindlin’s theories) with cracks subjected to static and dynamic loads. Fundamental solutions of dislocation are derived using
the Fourier transform method and the Laplace transformation technique. Boundary integral equations are presented in terms
of rotations/displacement on the crack surfaces. The Chebyshev polynomials of the second kind are used to evaluate the integral
equations with hypersingular kernels on the crack boundaries and determine the stress intensity factors at the crack tips.
Comparisons are made with other numerical solutions to demonstrate the proposed method is accurate both for static and dynamic
problems. 相似文献