全文获取类型
收费全文 | 3614篇 |
免费 | 396篇 |
国内免费 | 132篇 |
专业分类
电工技术 | 242篇 |
综合类 | 190篇 |
化学工业 | 762篇 |
金属工艺 | 132篇 |
机械仪表 | 185篇 |
建筑科学 | 173篇 |
矿业工程 | 131篇 |
能源动力 | 117篇 |
轻工业 | 186篇 |
水利工程 | 55篇 |
石油天然气 | 118篇 |
武器工业 | 15篇 |
无线电 | 509篇 |
一般工业技术 | 551篇 |
冶金工业 | 254篇 |
原子能技术 | 38篇 |
自动化技术 | 484篇 |
出版年
2024年 | 13篇 |
2023年 | 53篇 |
2022年 | 112篇 |
2021年 | 151篇 |
2020年 | 103篇 |
2019年 | 66篇 |
2018年 | 94篇 |
2017年 | 100篇 |
2016年 | 128篇 |
2015年 | 161篇 |
2014年 | 204篇 |
2013年 | 251篇 |
2012年 | 224篇 |
2011年 | 234篇 |
2010年 | 223篇 |
2009年 | 179篇 |
2008年 | 229篇 |
2007年 | 163篇 |
2006年 | 192篇 |
2005年 | 131篇 |
2004年 | 104篇 |
2003年 | 116篇 |
2002年 | 137篇 |
2001年 | 110篇 |
2000年 | 78篇 |
1999年 | 79篇 |
1998年 | 71篇 |
1997年 | 69篇 |
1996年 | 51篇 |
1995年 | 47篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 35篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1970年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有4142条查询结果,搜索用时 31 毫秒
31.
Integrated Microfluidic CustomArray Device for Bacterial Genotyping and Identification 总被引:2,自引:0,他引:2
32.
33.
特征选择是文本分类的关键步骤之一,所选特征子集的优劣直接影响文本分类的结果。论文首先定义了两种特征分类能力:一种是特征对类间文档的分散程度,该分散度越大越好;另一种是特征对类内文档的聚集程度,该集中度越大越好。然后把这两种特征影响度有机地结合起来设计了一个新的特征选择方法,该方法能够对所选特征进行综合考虑,从而使获得的特征集具有较好的代表性。仿真实验表明所提特征选择方法在一定程度上能够提高文本分类性能。 相似文献
34.
介绍一种以ARM为核心的嵌入式服务机器人体感遥控器的设计。硬件上,本遥控器采用具有ARM Cortex—M3内核的STM32F103C8T6作为核心处理器,选用ST公司的iNEMO惯性导航模块进行手部姿态的识别,同时还具有LCD显示模块、无线收发模块和电源模块;软件上,采用嵌入式操作系统μC/OS—Ⅱ实现多任务的调度和外围设备的管理。经实验验证,本遥控器具有高稳定性、高实时性、高可靠性、低误码率等优点。 相似文献
35.
Self-Organizing Map (SOM) possesses effective capability for visualizing high-dimensional data. Therefore, SOM has numerous applications in visualized clustering. Many growing SOMs have been proposed to overcome the constraint of having a fixed map size in conventional SOMs. However, most growing SOMs lack a robust solution to process mixed-type data which may include numeric, ordinal and categorical values in a dataset. Moreover, the growing scheme has an impact on the quality of resultant maps. In this paper, we propose a Growing Mixed-type SOM (GMixSOM), combining a value representation mechanism distance hierarchy with a novel growing scheme to tackle the problem of analyzing mixed-type data and to improve the quality of the projection map. Experimental results on synthetic and real-world datasets demonstrate that the proposed mechanism is feasible and the growing scheme yields better projection maps than the existing method. 相似文献
36.
37.
Nguyen Khanh Toan Nguyen Chi Tai Soo-A Kim Sang-Gun Ahn 《International journal of molecular sciences》2021,22(1)
Salivary gland dysfunction induces salivary flow reduction and a dry mouth, and commonly involves oral dysfunction, tooth structure deterioration, and infection through reduced salivation. This study aimed to investigate the impact of aging on the salivary gland by a metabolomics approach in an extensive aging mouse model, SAMP1/Klotho -/- mice. We found that the salivary secretion of SAMP1/Klotho -/- mice was dramatically decreased compared with that of SAMP1/Klotho WT (+/+) mice. Metabolomics profiling analysis showed that the level of acetylcholine was significantly decreased in SAMP1/Klotho -/- mice, although the corresponding levels of acetylcholine precursors, acetyl-CoA and choline, increased. Interestingly, the mRNA and protein expression of choline acetyltransferase (ChAT), which is responsible for catalyzing acetylcholine synthesis, was significantly decreased in SAMP1/Klotho -/- mice. The overexpression of ChAT induced the expression of salivary gland functional markers (α–amylase, ZO-1, and Aqua5) in primary cultured salivary gland cells from SAMP1/Klotho +/+ and -/- mice. In an in vivo study, adeno-associated virus (AAV)-ChAT transduction significantly increased saliva secretion compared with the control in SAMP1/Klotho -/- mice. These results suggest that the dysfunction in acetylcholine biosynthesis induced by ChAT reduction may cause impaired salivary gland function 相似文献
38.
The design and application of bioderived flame retardants have been widely conducted to meet the concept of green and sustainable development. Here, self-assembly technique is used to prepare core–shell bioderived additives by using β-FeOOH as the core and polydopamine (PDA)/tannic acid (TA) bilayer as the shell, following adsorption of nickel ions to enhance the thermal stability, flame retardancy, and mechanical properties of epoxy resin (EP). The molecular structure of biobased resources is rich in hydroxyl groups and carbon content, which can be dehydrated and carbonized during combustion and promote the formation of robust protective char layer. With the addition of 5 wt% β-FeOOH@PTNi, the EP composites can pass V-0 rating in the UL-94 test. The peak heat release rate and total heat release decrease by 28.4% and 17.4% compared with pure EP. The bioderived nanorods can capture the oxygen free radicals, contributing to flame retarding in gaseous phase. Thus, the release of high-toxic CO and flammable gaseous is significantly suppressed. Besides, the storage modulus of EP composites increases by 16.0% with the addition of 5% β-FeOOH@PTNi compared with pure EP. This work provides a sustainable methodology for the design of bioderived flame retardants for EP. 相似文献
39.
功能陶瓷现状与发展动向 总被引:15,自引:0,他引:15
本文重点论述了功能陶瓷材料,原料粉体、工艺与装备、元器件市场的现状及其发展趋势。指出了功能陶瓷在现代科技领域中具有重要意义及广阔的应用前景。 相似文献
40.
The thermal degradation of poly(vinyl butyral) (PVB)/glass ceramic, PVB/Ag, and PVB/glass ceramic/Ag composites was investigated with thermogravimetric analysis in nitrogen and air. Thermogravimetric data revealed that the compositions of both inorganic materials in air could greatly influence the thermal degradation of PVB. The degradation reactions of PVB/ceramic and PVB/Ag composites began earlier and accelerated rapidly at lower temperatures. The overall degradation period was obviously shortened for the thermal degradation of PVB/Ag in air, whereas a longer time was required for the PVB/ceramic composite than for PVB. Moreover, dual effects of ceramic and Ag on the thermal degradation of PVB were observed for PVB/ceramic/Ag composites. In addition, the catalytic effects of ceramic and Ag on the degradation reaction of PVB in air were verified with a kinetic analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2142–2149, 2004 相似文献