全文获取类型
收费全文 | 20067篇 |
免费 | 2147篇 |
国内免费 | 1180篇 |
专业分类
电工技术 | 1509篇 |
综合类 | 2992篇 |
化学工业 | 1823篇 |
金属工艺 | 483篇 |
机械仪表 | 1110篇 |
建筑科学 | 1957篇 |
矿业工程 | 627篇 |
能源动力 | 518篇 |
轻工业 | 833篇 |
水利工程 | 549篇 |
石油天然气 | 477篇 |
武器工业 | 168篇 |
无线电 | 2236篇 |
一般工业技术 | 2765篇 |
冶金工业 | 537篇 |
原子能技术 | 240篇 |
自动化技术 | 4570篇 |
出版年
2024年 | 66篇 |
2023年 | 212篇 |
2022年 | 407篇 |
2021年 | 478篇 |
2020年 | 564篇 |
2019年 | 501篇 |
2018年 | 515篇 |
2017年 | 635篇 |
2016年 | 723篇 |
2015年 | 733篇 |
2014年 | 1028篇 |
2013年 | 1288篇 |
2012年 | 1304篇 |
2011年 | 1476篇 |
2010年 | 1045篇 |
2009年 | 1323篇 |
2008年 | 1209篇 |
2007年 | 1445篇 |
2006年 | 1131篇 |
2005年 | 1015篇 |
2004年 | 898篇 |
2003年 | 890篇 |
2002年 | 697篇 |
2001年 | 615篇 |
2000年 | 535篇 |
1999年 | 432篇 |
1998年 | 322篇 |
1997年 | 343篇 |
1996年 | 239篇 |
1995年 | 209篇 |
1994年 | 196篇 |
1993年 | 154篇 |
1992年 | 151篇 |
1991年 | 119篇 |
1990年 | 85篇 |
1989年 | 89篇 |
1988年 | 58篇 |
1987年 | 46篇 |
1986年 | 35篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1966年 | 5篇 |
1964年 | 14篇 |
1963年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
颜呐 《广东工业大学高等工程教育研究》2007,7(2):78-80
白先勇以弱势的男性和强势的女性作为建构其小说世界的基点。男女角色易位颠覆了男强女弱的传统人物塑造方式,揭示出单个人边缘化生存所不为人知的痛苦。父辈影响、生活经历及其性取向是产生这一特色的根本原因。 相似文献
42.
Delevoye-Turrell Yvonne; Giersch Anne; Wing Alan M.; Danion Jean-Marie 《Canadian Metallurgical Quarterly》2007,116(1):56
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
44.
In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional “chain-like objects” (CLO's) that are 1–2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm−1 whose width is 35–40 cm−1, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm−1 scattering) concentrations. The 490 and 35 cm−1 values are consistent with bond angle deviations approaching 0°, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH4), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H2 levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon. 相似文献
45.
46.
47.
快速二阶BP网络及其在城市用水量预测中的应用 总被引:4,自引:0,他引:4
针对BP网络收敛速度慢,易导致局部极小值的缺点,提出一种快速二阶BP网络,并以城市年用水量预测为例,与BP网络对比,结果表明,该方法加快了收敛速度,提出了结果的准确度。 相似文献
48.
研究 m,m′-二氨基二苯酮 (m,m′- DABP)与均苯四酸二酐 (PMDA)的缩聚及亚酰化 ,并运用微波辐射和常规加热两种方式对反应进行了比较。考察了微波辐射时间 (功率 )、单体浓度、单体配比和温度等因素对缩聚物的特性粘数、转化率的影响。用红外光谱对亚酰化度进行了表征 ,并用简并四波混频技术首次测量了该缩聚物的三阶光学非线性极化率系数及其响应时间。实验结果表明 ,微波辐射对提高聚合物的特性粘数和转化率都有显著作用 ;合成的缩聚物具有较大的三阶光学非线性极化率系数 (聚酰亚胺的 χ(3) =1.642× 10 -13 esu)和较快的时间响应 (19ps 相似文献
49.
50.
In this paper,a new method is presented for 3D motion estimation by image region correspondences using stereo cameras.Under the weak perspectivity assumption.we first employ the moment tensor theory (Cyganski and Orr^[11]) to compute the monocular affine transformations relating images taken by the same camera at different time instants and the binocular affine transformations relating images taken by different cameras at the same time instant.We then show that 3D motion can be recovered from these 2D transformations.A space-time fusion strategy is proposed to aim at robust results.No knowledge of point correspondences if requred in the above processes and the computations involved are linear.To find corresponding image regions,new affine invariants,which show stronger invariance,are derived in term of tensor contraction theory.Experiments on real motion images are conducted to verify the proposed method. 相似文献