全文获取类型
收费全文 | 142442篇 |
免费 | 12577篇 |
国内免费 | 7501篇 |
专业分类
电工技术 | 8471篇 |
技术理论 | 15篇 |
综合类 | 10890篇 |
化学工业 | 22914篇 |
金属工艺 | 7692篇 |
机械仪表 | 8625篇 |
建筑科学 | 11545篇 |
矿业工程 | 3985篇 |
能源动力 | 3891篇 |
轻工业 | 13159篇 |
水利工程 | 3085篇 |
石油天然气 | 7318篇 |
武器工业 | 1274篇 |
无线电 | 16378篇 |
一般工业技术 | 16021篇 |
冶金工业 | 6065篇 |
原子能技术 | 1627篇 |
自动化技术 | 19565篇 |
出版年
2024年 | 704篇 |
2023年 | 2434篇 |
2022年 | 4533篇 |
2021年 | 5967篇 |
2020年 | 4734篇 |
2019年 | 3748篇 |
2018年 | 4075篇 |
2017年 | 4752篇 |
2016年 | 4268篇 |
2015年 | 6049篇 |
2014年 | 7623篇 |
2013年 | 9001篇 |
2012年 | 10120篇 |
2011年 | 10809篇 |
2010年 | 9569篇 |
2009年 | 8864篇 |
2008年 | 8777篇 |
2007年 | 8343篇 |
2006年 | 8021篇 |
2005年 | 6598篇 |
2004年 | 4622篇 |
2003年 | 3912篇 |
2002年 | 3885篇 |
2001年 | 3408篇 |
2000年 | 2828篇 |
1999年 | 2876篇 |
1998年 | 2252篇 |
1997年 | 1850篇 |
1996年 | 1750篇 |
1995年 | 1298篇 |
1994年 | 1204篇 |
1993年 | 847篇 |
1992年 | 678篇 |
1991年 | 522篇 |
1990年 | 384篇 |
1989年 | 308篇 |
1988年 | 266篇 |
1987年 | 171篇 |
1986年 | 126篇 |
1985年 | 87篇 |
1984年 | 46篇 |
1983年 | 46篇 |
1982年 | 54篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 16篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1959年 | 9篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Yadong Li Jing Liu Chenlong Liu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(2):329-348
To detect communities in signed networks consisting of both positive and negative links, two new evolutionary algorithms (EAs) and two new memetic algorithms (MAs) are proposed and compared. Furthermore, two measures, namely the improved modularity Q and the improved modularity density D-value, are used as the objective functions. The improved measures not only preserve all properties of the original ones, but also have the ability of dealing with negative links. Moreover, D-value can also control the partition to different resolutions. To fully investigate the performance of these four algorithms and the two objective functions, benchmark social networks and various large-scale randomly generated signed networks are used in the experiments. The experimental results not only show the capability and high efficiency of the four algorithms in successfully detecting communities from signed networks, but also indicate that the two MAs outperform the two EAs in terms of the solution quality and the computational cost. Moreover, by tuning the parameter in D-value, the four algorithms have the multi-resolution ability. 相似文献
83.
Lijin Xie Junfeng Ma Jun Zhou Zhongqiang Zhao Hua Tian Yonggang Wang Jiantao Tao Xiaoyi Zhu 《Journal of the American Ceramic Society》2006,89(5):1717-1720
Well-crystallized bismuth tungstate (Bi2 WO6 ) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi2 WO6 powder mainly depends on the different reaction temperatures and the weight ratio of LiNO3 –NaNO3 salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region. 相似文献
84.
合成气中氨含量测定方法的改进 总被引:1,自引:0,他引:1
用快速测定仪测定气体中的氨含量,采气量为50ml,可准确测出高含量氨体积百分比含量为80%-100%和低含量氨体积百分比含量为1%-20%的样气,该仪器结构简单,易于制造,测定过程简单,结果准确,一目了然。 相似文献
85.
86.
朱云溪 《网络安全技术与应用》2014,(10):200-201
云计算是一种基于互联网的计算方式,通过这种方式,共享的软硬件资源和信息可以按需提供给计算机和其他设备,该技术是一种近些年来发展的新兴科技,同时在一定的程度之上遍布于软件企业的各个领域之中,引导着当前软件企业发展的方向.基于此,本文探讨了云计算背景之下软件企业创新的趋势. 相似文献
87.
Shape‐memory polyurethane/multiwalled carbon nanotube (SMP–MWNT) composites with various multiwalled carbon nanotube (MWNT) contents were synthesized, and the corresponding SMP–MWNT fibers were prepared by melt spinning. The influence of the MWNT content on the spinnability, fracture morphology, thermal and mechanical properties, and shape‐memory behavior of the shape‐memory polymer was studied. The spinning ability of SMP–MWNTs decreased significantly with increasing MWNT content. When the MWNT content reached 8.0 wt %, the fibers could not be produced because of the poor rheological properties of the composites. The melt‐blending, extrusion, and melt‐spinning processes for the shape‐memory fiber (SMF), particularly at low MWNT contents, caused the nanotubes to distribute homogeneously and preferentially align along the drawing direction of the SMF. The crystallization in the SMF was promoted at low MWNT contents because it acted as a nucleation agent. At high MWNT contents, however, the crystallization was hindered because the movement of the polyurethane chains was restricted. The homogeneously distributed and aligned MWNTs preserved the SMF with high tenacity and initial modulus. The recovery ratio and recovery force were also improved because the MWNTs helped to store the internal elastic energy during stretching and fixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
88.
89.
祝娟 《重庆科技学院学报(社会科学版)》2010,(9):38-40
对于科技发展带来的一些消极影响,有人认为伦理的干预是无济于事的,甚至最终会影响科技本身的发展。但是,现实中科技与社会发展之间的密切关系表明,对科技的发展给予伦理导向是社会发展的必然走向。把科学发展观作为科技发展的伦理向度,能够实现科技发展和社会进步两者的双赢。 相似文献
90.
朱志美 《重庆科技学院学报(社会科学版)》2010,(9):145-146,149
语境在语言理解中起着重要作用,是语言交际的基础。结合具体例子,分析了语境在语言理解中具有消除歧义、转变语义、补充语言省略意义、帮助理解言外之意的作用。指出只有正确地把握语境,才能深入理解语言的真正含义。 相似文献