全文获取类型
收费全文 | 139894篇 |
免费 | 8835篇 |
国内免费 | 4308篇 |
专业分类
电工技术 | 6684篇 |
技术理论 | 7篇 |
综合类 | 12105篇 |
化学工业 | 9356篇 |
金属工艺 | 5384篇 |
机械仪表 | 14615篇 |
建筑科学 | 34967篇 |
矿业工程 | 3989篇 |
能源动力 | 3038篇 |
轻工业 | 5032篇 |
水利工程 | 3678篇 |
石油天然气 | 4266篇 |
武器工业 | 1567篇 |
无线电 | 9534篇 |
一般工业技术 | 13322篇 |
冶金工业 | 2952篇 |
原子能技术 | 684篇 |
自动化技术 | 21857篇 |
出版年
2024年 | 479篇 |
2023年 | 1546篇 |
2022年 | 2468篇 |
2021年 | 3188篇 |
2020年 | 3458篇 |
2019年 | 2630篇 |
2018年 | 2415篇 |
2017年 | 2967篇 |
2016年 | 3405篇 |
2015年 | 3805篇 |
2014年 | 9917篇 |
2013年 | 7776篇 |
2012年 | 9864篇 |
2011年 | 10621篇 |
2010年 | 8979篇 |
2009年 | 9379篇 |
2008年 | 8601篇 |
2007年 | 10150篇 |
2006年 | 8521篇 |
2005年 | 7514篇 |
2004年 | 6095篇 |
2003年 | 5663篇 |
2002年 | 4451篇 |
2001年 | 3729篇 |
2000年 | 3092篇 |
1999年 | 2402篇 |
1998年 | 1916篇 |
1997年 | 1599篇 |
1996年 | 1331篇 |
1995年 | 1072篇 |
1994年 | 857篇 |
1993年 | 603篇 |
1992年 | 494篇 |
1991年 | 415篇 |
1990年 | 263篇 |
1989年 | 264篇 |
1988年 | 219篇 |
1987年 | 153篇 |
1986年 | 91篇 |
1985年 | 119篇 |
1984年 | 143篇 |
1983年 | 90篇 |
1982年 | 95篇 |
1981年 | 32篇 |
1980年 | 37篇 |
1979年 | 31篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The multihop optical network is the most appropriate solution to satisfy the increasing applications of Internet services. This paper extends the regular Kautz graph to one with multiple layers in order to produce more architectural variations. The connectivity between adjacent layers utilizes the systematic connection patterns of a regular Kautz graph. A routing algorithm based on its property is presented. Optical passive star (OPS) couplers are adopted to implement our new topologies. Three scheduling criteria that can solve the contention problem in the intermediate nodes are evaluated and compared in terms of their capability to improve the accessibility. 相似文献
102.
介绍了柳钢新建120万t/a链篦机-回转窑氧化球团工程的主要设计特点。该工程是我国第一条自行设计、设备国产化和采用清洁气体能源的链篦机-回转窑生产线。它的顺利投产,标志着我国炼铁炉料生产技术有了一个新的进步。 相似文献
103.
104.
R. Maciel Filho C. B. Batistella P. Sbaite A. Winter C. J. G. Vasconcelos M. R. Wolf Maciel A. Gomes L. Medina R. Kunert 《Petroleum Science and Technology》2006,24(3):275-283
The term atmospheric residue describes the material at the bottom of the atmospheric distillation tower having a lower boiling point limit of about 340°C; the term vacuum residue (heavy petroleum fractions) refers to the bottom of the vacuum distillation, which has an atmospheric equivalent boiling point (AEBP) above 540°C. In this work, the objective is to evaluate the behavior of different kinds of Brazilian atmospheric and vacuum residues using molecular distillation. The Falling Film Molecular Distillator was used. For the results obtained through this process, a significant range of temperature can be explored avoiding the thermal decomposition of the material. So these results are very important to the refinery decisions and improvements. The Experimental Factorial Design results showed that the temperature has more influence on the process than the feed flow rate, when a higher percentage of distillate is required. 相似文献
105.
106.
大型往复式压缩机功率大、占地面积大,管道振动问题也更为突出。笔者结合实践经验,对大型往复式压缩机的配管设计进行探讨,说明了平面布置与管道防振设计的密切关系,并介绍了管道防振设计的方法和步骤,以及相对简单的复杂管系气柱固有频率的转移矩阵计算方法。 相似文献
107.
基于联系国内外智能交通系统研究的具体实际,提出了建立城市智能交通实验研究中心的设想,并结合一个集成了视频和线圈信息采集方式的实验研究中心简单设计方案,对其所具有的基本功能作了初步研究和探讨。该系统兼具促进交流和有关培训等社会职能,可以作为国家智能交通事业发展过程中一种特殊的示范工程。 相似文献
108.
一种基于PWM的电压输出DAC电路设计 总被引:16,自引:1,他引:15
对实际应用中的脉宽调制(PWM)波形的频谱进行了理论分析.指出通过一个低通滤波器可以把PWM调制的数模转换信号解调出来.实现从PWM到DAC的转换。论文还对转换误差产生的因素进行了分析,指出了减少误差的方法,论文给出了两种从PWM到0~5V电压输出的电路实现方法,第2种电路具有很高的转换精度。 相似文献
109.
In this article, a subtractive clustering-based fuzzy identification method and a Sugeno-type fuzzy inference system are used for modeling in metal cutting. This approach is considered with its application on the experimental study of Boring and Trepanning Association (BTA) deep-hole drilling. The model for the surface roughness is identified by using the cutting speed and feed as input data and roughness as the output data. Using subtractive clustering in both input and output spaces performs the model-building process. Minimum error model is obtained through enumerative search of clustering parameters. The fuzzy model obtained is capable of predicting the surface roughness for a given set of inputs (speed and feed). Therefore, the operator can predict the quality of the surface for a given set of working parameters and will then be able to set the machining parameters to achieve a certain surface quality. The fuzzy model is verified experimentally by further experimentation using different sets of inputs. The tool life is also investigated using the same approach. The fuzzy inference system obtained is capable of predicting the tool life for a given set of cutting parameters. Therefore, the operator will be able to predict how many minutes the cutting tool is going to last and will set the time for the next tool change. 相似文献
110.
Due to the demand for real time wavelet processors in applications such as video compression [1], Internet communications compression [2], object recognition [3], and numerical analysis, many architectures for the Discrete Wavelet Transform (DWT) systems have been proposed. This paper surveys the different approaches to designing DWT architectures. The types of architectures depend on whether the application is 1-D, 2-D, or 3-D, as well as the style of architecture: systolic, semi-systolic, folded, digit-serial, etc. This paper presents an overview and evaluation of the architectures based on the criteria of latency, control, area, memory, and number of multipliers and adders. This paper will give the reader an indication of the advantages and disadvantages of each design. 相似文献