全文获取类型
收费全文 | 6602篇 |
免费 | 852篇 |
国内免费 | 555篇 |
专业分类
电工技术 | 278篇 |
技术理论 | 1篇 |
综合类 | 490篇 |
化学工业 | 156篇 |
金属工艺 | 69篇 |
机械仪表 | 334篇 |
建筑科学 | 2219篇 |
矿业工程 | 103篇 |
能源动力 | 115篇 |
轻工业 | 179篇 |
水利工程 | 37篇 |
石油天然气 | 66篇 |
武器工业 | 139篇 |
无线电 | 1099篇 |
一般工业技术 | 467篇 |
冶金工业 | 229篇 |
原子能技术 | 160篇 |
自动化技术 | 1868篇 |
出版年
2024年 | 17篇 |
2023年 | 97篇 |
2022年 | 129篇 |
2021年 | 153篇 |
2020年 | 192篇 |
2019年 | 138篇 |
2018年 | 156篇 |
2017年 | 200篇 |
2016年 | 329篇 |
2015年 | 312篇 |
2014年 | 474篇 |
2013年 | 418篇 |
2012年 | 543篇 |
2011年 | 516篇 |
2010年 | 462篇 |
2009年 | 454篇 |
2008年 | 449篇 |
2007年 | 474篇 |
2006年 | 454篇 |
2005年 | 340篇 |
2004年 | 285篇 |
2003年 | 261篇 |
2002年 | 186篇 |
2001年 | 142篇 |
2000年 | 125篇 |
1999年 | 122篇 |
1998年 | 75篇 |
1997年 | 80篇 |
1996年 | 54篇 |
1995年 | 46篇 |
1994年 | 66篇 |
1993年 | 28篇 |
1992年 | 46篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1968年 | 3篇 |
1963年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有8009条查询结果,搜索用时 170 毫秒
1.
Ahlam Ammar Sharif 《建筑学研究前沿(英文版)》2020,9(4):837-857
Urban researchers have maintained a constant interest in the complexity and continuity of urban space usage. Some have applied actor–network theory (ANT) to investigate the heterogeneity of spaces and present them through the networks of their users’ activities. However, these accounts are predominantly limited in examining the extent to which these spaces may be heterogeneous when exploring such networks. This paper draws on recent ANT scholarship, which employs an ethnographic research conducted in a main park in a housing project at Dahiyat Al Hussein in Amman, Jordan. The findings describe the complex and unpredictable negotiations that occur within spaces by documenting the varieties and interrelations among user activity networks within this common and shared urban space. This research reveals the extent to which spaces, parks in this case, may be heterogeneous by unpacking their usage. The conclusions and insights assert the necessity of paying attention to design detail and creating designs that are responsive to evolving user activities. 相似文献
2.
目前,基于因素空间理论的背景基提取算法计算过程复杂,初始化必须依赖各因素极值,基点数量提取冗余等原因,未能在应用中取得很好效果。为此,结合内点判别法和知识可继承、可扩展的思想,提出一种计算简单、初始化独立、基点数量小的改进的背景基提取算法。然后,利用改进的背景基提取算法构造出一种全新的数据分类算法-基点分类算法,基点分类算法以提取每一类样本的背景基为预测模型,再通过新定义的λ-背景基,优化预测模型。数值实验表明:基点分类算法原理简单、构造难度小、分类模型泛化能力强,预测能力准确率高,同时严格的模型限定区域又能为识别新类别提供新方法。 相似文献
3.
Hannerz Harald; Albertsen Karen; Nielsen Martin Lindhardt; Tüchsen Finn; Burr Hermann 《Canadian Metallurgical Quarterly》2004,23(3):283
This study explored whether factors related to the work environment could predict changes in body mass index (BMI) and whether the effect of psychosocial factors was dependent on baseline BMI. The sample consisted of 1,980 male employees from the Danish National Work Environment Cohort Study. Changes in BMI between 1995 and 2000 were analyzed, by multiple regression, as a function of background variables and a series of occupational variables obtained in 1995. Age, baseline BMI, job insecurity, and psychological demands predicted changes in BMI. Job insecurity and high or low psychological demands increased the likelihood of weight gain among obese employees, whereas they increased the likelihood of weight loss among employees with a low BMI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
In this paper we suggest a new statistical method of correcting the results of hot-line experiments for the effects of background sources and we use the new method to reassess the adequacy of three probability distributions proposed in the literature for image spread from line sources. The data are from sources labelled with 125I in semi-thin resin sections 0·4-0·8 μm in thickness. The new method reveals that two of the models describe the empirical distributions more closely than earlier analysis had suggested, and it confirms an increasing relationship between half distance of image spread and the thickness of the source. However, it also confirms that considerable ‘inter hot-line’ experimental variation remains, even after background correction. This suggests that multiple experiments are needed to produce reliable estimates of half distance. 相似文献
5.
J.S. Sánchez 《Pattern recognition》2004,37(7):1561-1564
Instance-based learning methods like the nearest neighbour classifier generally suffer from the indiscriminate storage of all training instances, resulting in large memory requirements and slow execution speed. In this paper, new training set size reduction methods based on prototype generation and space partitioning are proposed. Experimental results show that the new algorithms achieve a very high reduction rate with still an important classification accuracy. 相似文献
6.
为了实现利用VisualBasic编程语言实现动画模拟的功能,文章以对运动目标跟踪的计算机模拟为例,提出和实现了用该语言实现动画的各种方法,介绍了每种方法的原理并通过程序示例证明其达到了相应的动画效果。 相似文献
7.
8.
9.
John P. Wikswo Jr. Nestor G. Sepulveda Yu Pei Ma W. Patrick Henry Daniel J. Staton Duane Crum 《Journal of Nondestructive Evaluation》1993,12(2):109-119
A SQUID magnetometer can be used to measure the magnetic field produced by flaws in a two-dimensional, conducting plate carrying a current. Identification of the flaw-induced magnetic field is difficult because of the large magnetic field associated with the edges of the plate and the current in the leads that connect the plate to the power supply. We have developed a technique by which the wire and edge fields can be cancelled prior to mapping the magnetic field. In this technique, a similar unflawed conducting sheet is placed adjacent to the flawed plate, with a connection between the sheet and the plate at one edge, and with the opposite edges of the sheet and of the plate connected to the two conductors of a coaxial cable. Thus, an applied current will flow along one conductor of the cable, across the cancelling sheet, cross into the flawed plate, return along the plate, and then return to the power supply along the other conductor of the coaxial cable. As a result of this geometry, there is no magnetic field from the lead-in wires because they are coaxial, and the magnetic field due to the edges of the plate is cancelled by the opposing magnetic field of the edges in the adjacent sheet. The extent of cancellation is determined primarily by the separation between the plate and the cancelling sheet, by the thickness of the plate, and by macroscopic inhomogeneities in their electrical conductivities. 相似文献
10.
Yong-Jik KimJames H. Anderson 《Information Processing Letters》2002,84(1):47-55
A simple code transformation is presented that reduces the space complexity of Yang and Anderson's local-spin mutual exclusion algorithm. In both the original and the transformed algorithm, only atomic read and write instructions are used; each process generates Θ(logN) remote memory references per lock request, where N is the number of processes. The transformed algorithm uses Θ(N) distinct variables, which is clearly optimal. 相似文献