全文获取类型
收费全文 | 45795篇 |
免费 | 4805篇 |
国内免费 | 2712篇 |
专业分类
电工技术 | 1525篇 |
技术理论 | 2篇 |
综合类 | 4063篇 |
化学工业 | 4091篇 |
金属工艺 | 2577篇 |
机械仪表 | 3353篇 |
建筑科学 | 893篇 |
矿业工程 | 1472篇 |
能源动力 | 448篇 |
轻工业 | 5413篇 |
水利工程 | 358篇 |
石油天然气 | 1432篇 |
武器工业 | 881篇 |
无线电 | 8008篇 |
一般工业技术 | 3612篇 |
冶金工业 | 2131篇 |
原子能技术 | 361篇 |
自动化技术 | 12692篇 |
出版年
2024年 | 122篇 |
2023年 | 630篇 |
2022年 | 973篇 |
2021年 | 1319篇 |
2020年 | 1257篇 |
2019年 | 986篇 |
2018年 | 918篇 |
2017年 | 1245篇 |
2016年 | 1364篇 |
2015年 | 1690篇 |
2014年 | 2429篇 |
2013年 | 2436篇 |
2012年 | 3086篇 |
2011年 | 3479篇 |
2010年 | 2552篇 |
2009年 | 2621篇 |
2008年 | 2685篇 |
2007年 | 3246篇 |
2006年 | 2887篇 |
2005年 | 2589篇 |
2004年 | 2189篇 |
2003年 | 1994篇 |
2002年 | 1650篇 |
2001年 | 1328篇 |
2000年 | 1238篇 |
1999年 | 932篇 |
1998年 | 830篇 |
1997年 | 763篇 |
1996年 | 648篇 |
1995年 | 512篇 |
1994年 | 493篇 |
1993年 | 413篇 |
1992年 | 317篇 |
1991年 | 253篇 |
1990年 | 237篇 |
1989年 | 202篇 |
1988年 | 139篇 |
1987年 | 80篇 |
1986年 | 71篇 |
1985年 | 86篇 |
1984年 | 68篇 |
1983年 | 81篇 |
1982年 | 61篇 |
1981年 | 43篇 |
1980年 | 31篇 |
1979年 | 29篇 |
1978年 | 19篇 |
1977年 | 25篇 |
1976年 | 12篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 247 毫秒
101.
文章主要讨论了LonWorks现场总线技术在城市污水处理厂和气象指数预报中的应用。采用IPC和PLC控制结构对现场的各种设备实现控制和数据的采集,通过现场总线网络传输数据到中心控制室或远程终端,实现污水处理的自动控制和气象信息的实时采集和处理。 相似文献
102.
103.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at 相似文献
104.
105.
对瑞利和非瑞利杂波中的单、双参数杂波图的控制虚警性能和检测性能进行了比较分析,并得到了双参数杂波图门限调整值的取值范围,得出了几点有益的结论。 相似文献
106.
Quality of Crude Fish Oil Extracted from Herring Byproducts of Varying States of Freshness 总被引:1,自引:0,他引:1
ABSTRACT: Herring byproducts were stored at 2 and 15 °C for up to 72 h. Over time, significant increases of total volatile bases (TVB), histamine, putrescine, cadaverine, and tyramine were detected. However, only tyramine and TVB levels were temperature-dependent. The level of total polyunsaturated fatty acids (PUFAs) was constant. Longer byproducts storage gave rise to an oil with higher levels of free fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total PUFAs, while fluorescent compounds were lower. A higher storage temperature led to oil higher in α-tocopherol and EPA levels and lower in anisidine value. Surprisingly, the oil with the highest content of PUFAs was not produced from the freshest byproducts, and oil with low oxidation products can be extracted from stored byproducts. 相似文献
107.
Reports an error in "Interactive use of lexical information in speech perception" by Cynthia M. Connine and Charles Clifton (Journal of Experimental Psychology: Human Perception and Performance, 1987[May], Vol 13[2], 291-299). In the aforementioned article, Figures 1 and 2 were inadvertently transposed. The figure on p. 294 is actually Figure 2, and the figure on p. 296 is actually Figure 1. The captions are correct as they stand. (The following abstract of the original article appeared in record 1987-23984-001.) Two experiments are reported that demonstrate contextual effects on identification of speech voicing continua. Experiment 1 demonstrated the infuence of lexical knowledge on identification of ambiguous tokens from word–nonword and nonword–word continua. Reaction times for word and nonword responses showed a word advantage only for ambiguous stimulus tokens (at the category boundary); no word advantage was found for clear stimuli (at the continua endpoints). Experiment 2 demonstrated an effect of a postperceptual variable, monetary payoff, on nonword–nonword continua. Identification responses were influenced by monetary payoff, but reaction times for bias-consistent and bias-inconsistent responses did not differ at the category boundary. An advantage for bias-consistent responses was evident at the continua endpoints. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
阐述了仿真环境中的网络攻击模型的设计,建立了一个网络攻击仿真模型,用以产生网络攻击,以达到摧毁网络的机密性、完整性和可用性的目的;采用知识表达的方法来建立模型,该模型包含具有知识库和推理机的专家系统,通过随时间而变化的量,使模型具有基于仿真时钟的推理能力;在攻击模型的设计中,定义了它的基本状态和状态跃迁函数,说明了模型的行为,以及攻击策略的制定,最佳策略的选择,攻击选择原则等问题。 相似文献
109.
Airframe riveting is a critical process that requires high levels of process monitoring and quality assurance due to the very
high risk associated with the failure of such joints. This paper describes the development of the enabling technology developed
for a machine vision-based process monitoring system. One of the key factors affecting the performance of a machine vision
system is the quality of the lighting. In the application described in this paper the available lighting was severely limited
by the confined space in which the system had to operate. The problem was also compounded by the reflective nature of the
objects to be examined. The initial images obtained were not suitable for further processing due to the presence of significant
shadows and specular reflections. A novel solution to this problem based on multiple wavelength illumination and signal processing
is presented along with results from experimental trials of the approach. 相似文献
110.
CaCu3Ti4O12 electroceramic was prepared by a microwave assisted solid-state reaction technique from CaCO3, CuO and TiO2 powders. Processing involved the preparation of raw material, mixing and milling, calcination, pellet forming and sintering processes. Conventional furnace and microwave assisted sintering processes were employed in order to improve phase structures, morphology and dielectric properties of CaCu3Ti4O12 ceramics. Surface and fracture FESEM analysis showed that the microwave assisted sintered CaCu3Ti4O12 produced better densification and more uniform grain size compared to the conventional sintered sample. 相似文献