全文获取类型
收费全文 | 9908篇 |
免费 | 836篇 |
国内免费 | 376篇 |
专业分类
电工技术 | 509篇 |
综合类 | 420篇 |
化学工业 | 1738篇 |
金属工艺 | 571篇 |
机械仪表 | 670篇 |
建筑科学 | 839篇 |
矿业工程 | 264篇 |
能源动力 | 262篇 |
轻工业 | 749篇 |
水利工程 | 137篇 |
石油天然气 | 597篇 |
武器工业 | 71篇 |
无线电 | 1129篇 |
一般工业技术 | 1422篇 |
冶金工业 | 501篇 |
原子能技术 | 123篇 |
自动化技术 | 1118篇 |
出版年
2024年 | 25篇 |
2023年 | 176篇 |
2022年 | 276篇 |
2021年 | 393篇 |
2020年 | 306篇 |
2019年 | 279篇 |
2018年 | 290篇 |
2017年 | 365篇 |
2016年 | 334篇 |
2015年 | 379篇 |
2014年 | 545篇 |
2013年 | 606篇 |
2012年 | 646篇 |
2011年 | 780篇 |
2010年 | 610篇 |
2009年 | 568篇 |
2008年 | 572篇 |
2007年 | 477篇 |
2006年 | 487篇 |
2005年 | 420篇 |
2004年 | 308篇 |
2003年 | 267篇 |
2002年 | 229篇 |
2001年 | 203篇 |
2000年 | 189篇 |
1999年 | 283篇 |
1998年 | 209篇 |
1997年 | 201篇 |
1996年 | 152篇 |
1995年 | 123篇 |
1994年 | 99篇 |
1993年 | 64篇 |
1992年 | 48篇 |
1991年 | 49篇 |
1990年 | 29篇 |
1989年 | 25篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
91.
92.
Fresh leaves and volatile oil of the important weed Ageratum conyzoides in south China were highly inhibitory to seedling growth of various cultivated crops, especially in an adverse habitat. The constituents of the volatile oil were analyzed by GC-MS. Eleven components were identified and six main components, precocene I, precocene II, 3,3-dimethyl-5-tert-butylindone, -caryophyllene, -bisabolene, and fenchyl acetate, were isolated by means of column chromatography. Precocene I, precocene II, -caryophyllene, and 3,3-dimethyl-5-tert-butylindone inhibited seedling growth of acceptor plants. Inhibitory activity of the volatile oil was more intense than that of the pure components. Fenchyl acetate and -bisabolene have no inhibitory activity, but when mixed with precocene II, they increased the inhibitory activity to growth of acceptor seedling plants. Experiments show that allelopathic synergism exists among allelochemicals of Ageratum conyzoides. 相似文献
93.
随着我国经济的增长,越来越多的高速公路相继建成通车。特别是一些山区高速公路,由于受到地势条件的限制,多呈纵坡大、展线复杂、区域小气候影响大。近年来,我国山区高速公路互通桥梁相继出现梁体滑移导致伸缩缝挤死,造成桥面出现隆起现象,严重影响行车安全。通过对某高速公路某座互通主线桥伸缩缝挤死导致桥面隆起的现象进行了深入调查,结合施工质量、设计理念对病害产生的原因进行了分析研究,并对病害提出了针对性的维修处治建议。为山区高速公路互通立交桥梁的设计、施工、养护工作有一定的指导意义。 相似文献
94.
基于现阶段条件下的混凝土热力学参数及温控措施,考虑气温、混凝土性能随龄期的变化及MgO的膨胀性等因素,采用三维有限元法对鱼粮水库拱坝的温度场进行仿真计算分析,计算结果表明,坝体混凝土在自然入仓、冬季保温的情况下,无需采取其它温控措施,通过对比不分缝方案及分缝方案,说明设置诱导缝可改善坝体应力分布情况。通过改变缝的位置更加有利于释放大坝温度应力,且各部位应力均能满足规范要求。 相似文献
95.
介绍了企业在面临国际陶瓷市场竞争激烈的形势下,努力转变发展思路,拓宽市场,强化质量意识。根据市场变化,生产适销对路搞档优质陶瓷产品,增强产品的市场能力,提高了企业的经济效益。 相似文献
96.
Cluster ensemble approaches make use of a set of clustering solutions which are derived from different data sources to gain a more comprehensive and significant clustering result over conventional single clustering approaches. Unfortunately, not all the clustering solutions in the ensemble contribute to the final result. In this paper, we focus on the clustering solution selection strategy in the cluster ensemble, and propose to view clustering solutions as features such that suitable feature selection techniques can be used to perform clustering solution selection. Furthermore, a hybrid clustering solution selection strategy (HCSS) is designed based on a proposed weighting function, which combines several feature selection techniques for the refinement of clustering solutions in the ensemble. Finally, a new measure is designed to evaluate the effectiveness of clustering solution selection strategies. The experimental results on both UCI machine learning datasets and cancer gene expression profiles demonstrate that HCSS works well on most of the datasets, obtains more desirable final results, and outperforms most of the state-of-the-art clustering solution selection strategies. 相似文献
97.
This paper presents a segment-based probabilistic approach to robustly recognize continuous sign language sentences. The recognition strategy is based on a two-layer conditional random field (CRF) model, where the lower layer processes the component channels and provides outputs to the upper layer for sign recognition. The continuously signed sentences are first segmented, and the sub-segments are labeled SIGN or ME (movement epenthesis) by a Bayesian network (BN) which fuses the outputs of independent CRF and support vector machine (SVM) classifiers. The sub-segments labeled as ME are discarded and the remaining SIGN sub-segments are merged and recognized by the two-layer CRF classifier; for this we have proposed a new algorithm based on the semi-Markov CRF decoding scheme. With eight signers, we obtained a recall rate of 95.7% and a precision of 96.6% for unseen samples from seen signers, and a recall rate of 86.6% and a precision of 89.9% for unseen signers. 相似文献
98.
99.
100.
Guodong Jing Yunhui Shi Dehui Kong Wenpeng Ding Baocai Yin 《Multimedia Tools and Applications》2014,70(2):741-755
Sparse representation provides a new method of generating a super-resolution image from a single low resolution input image. An over-complete base for sparse representation is an essential part of such methods. However, discovering the over-complete base with efficient representation from a large amount of image patches is a difficult problem. In this paper, we propose a super-resolution construction based on multi-space sparse representation to efficiently solve the problem. In the representation, image patches are decomposed into a structure component and a texture component represented by the over-complete bases of their own spaces so that their high-level features can be captured by the bases. In the implementation, a prior knowledge about low resolution images generation is combined to the typical base construction for high construction quality. Experiment results demonstrate that the proposed method significantly improves the PSNR, SSIM and visual quality of reconstructed high-resolution image. 相似文献