全文获取类型
收费全文 | 32217篇 |
免费 | 3099篇 |
国内免费 | 1500篇 |
专业分类
电工技术 | 2280篇 |
技术理论 | 1篇 |
综合类 | 2017篇 |
化学工业 | 5470篇 |
金属工艺 | 1794篇 |
机械仪表 | 2029篇 |
建筑科学 | 2552篇 |
矿业工程 | 987篇 |
能源动力 | 880篇 |
轻工业 | 2441篇 |
水利工程 | 585篇 |
石油天然气 | 1675篇 |
武器工业 | 271篇 |
无线电 | 3959篇 |
一般工业技术 | 4095篇 |
冶金工业 | 1358篇 |
原子能技术 | 416篇 |
自动化技术 | 4006篇 |
出版年
2024年 | 184篇 |
2023年 | 659篇 |
2022年 | 1296篇 |
2021年 | 1540篇 |
2020年 | 1199篇 |
2019年 | 979篇 |
2018年 | 1090篇 |
2017年 | 1214篇 |
2016年 | 990篇 |
2015年 | 1383篇 |
2014年 | 1732篇 |
2013年 | 1904篇 |
2012年 | 2067篇 |
2011年 | 2141篇 |
2010年 | 1818篇 |
2009年 | 1827篇 |
2008年 | 1786篇 |
2007年 | 1570篇 |
2006年 | 1639篇 |
2005年 | 1335篇 |
2004年 | 874篇 |
2003年 | 885篇 |
2002年 | 830篇 |
2001年 | 735篇 |
2000年 | 742篇 |
1999年 | 792篇 |
1998年 | 640篇 |
1997年 | 551篇 |
1996年 | 476篇 |
1995年 | 432篇 |
1994年 | 322篇 |
1993年 | 248篇 |
1992年 | 227篇 |
1991年 | 145篇 |
1990年 | 127篇 |
1989年 | 117篇 |
1988年 | 85篇 |
1987年 | 52篇 |
1986年 | 31篇 |
1985年 | 35篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This paper formulates and studies a model of complex dynamical networks with switching topology and coupling delays. Based on the hybrid control and Lyapunov function, the stability and robust H∞ control of such networks with impulsive and switching effects, which have not been studied before, are addressed with some criteria derived. Examples are given to illustrate the effectiveness of the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
52.
Yao Huang Kao Jeun Chyuan Huang Yih Shun Gou 《Journal of Low Temperature Physics》1986,63(3-4):287-305
An analog circuit is used to investigate the behavior of the transition to chaos in the rf-driven Josephson junction under the variation of excitation amplitude and frequency with McCumber parameter >1. A series of transitions is observed, including a hysteretic jump, symmetry breaking, period doubling, and intermittency prior to chaos, and the transition boundaries are given in a state diagram in the vs. parameter space. Thus, the sequence of transitions to chaos can be inferred from this diagram. Based on these results, the harmonic balance method and Floquet theory are applied to study the instability of the transition series. It is suggested that all these transitions to chaos can be explained as parametric excitations. In addition, the transition boundaries in the state diagram can be satisfactorily computed from the conditions with a Floquet multiplier =±1. 相似文献
53.
54.
LD7铝合金时效工艺的研究 总被引:5,自引:3,他引:5
通过试验系统地研究了LD7铝合金的单级和两级时效工艺。结果表明,与传统的单级时效相比,两级时效在不降低室温强度,硬度的前提下,可显著提高合金的电导率及高温性能。 相似文献
55.
A second generation proton beam writing (PBW) system has been built at the Centre for Ion Beam Applications at the National University of Singapore for fabrication of high aspect ratio 3D nano lithographic structures. System improvements and a few lithographic structures obtained with this facility are presented in this paper. Through accurate alignment of the magnetic quadrupole lenses and the electrostatic scanning system, orthogonal beam scanning has been achieved. The earlier constrain of limited beam scan area has been overcome by adopting a combination of beam and stage scanning as well as stitching. With these improvements smallest ever Ni structure of 65 nm in width has been fabricated using nickel electroplating on a proton beam written PMMA sample in the second generation PBW facility. Using this improved PBW facility, we have also demonstrated the fabrication of fine lithographic patterns with 19 nm line width and 60 nm spacing in 100 nm thick negative high resolution hydrogen silsesquioxane resist. Future possible system improvements leading to finer resolution will be discussed briefly. 相似文献
56.
One of the fundamental tasks of targeted marketing is to elicit associations between customers and products. Based on the results from information retrieval and utility theory, this article proposes a unified framework of targeted marketing. The customer judgments of products are formally described by preference relations and the connections of customers and products are quantitatively measured by market value functions. Two marketing strategies, known as the customer‐oriented and product‐oriented marketing strategies, are investigated. Four marketing models are introduced and examined. They represent, respectively, the relationships between a group of customers and a group of products, between a group of customers and a single product, between a single customer and a group of products, and between a single customer and a single product. Linear and bilinear market value functions are suggested and studied. The required parameters of a market value function can be estimated by exploring three types of information, namely, customer profiles, product profiles, and transaction data. Experiments on a real‐world data set are performed to demonstrate the effectiveness of the proposed framework. 相似文献
57.
Chengjun Yao Yixun Liu Jianhua Yao Dongxiao Zhuang Jinsong Wu Zhiyong Qin Ying Mao Liangfu Zhou 《Computer methods and programs in biomedicine》2014
Background
Preoperatively acquired diffusion tensor image (DTI) and blood oxygen level dependent (BOLD) have been proved to be effective in providing more anatomical and functional information; however, the brain deformation induced by brain shift and tumor resection severely impairs the correspondence between the image space and the patient space in image-guided neurosurgery.Method
To address the brain deformation, we developed a hybrid non-rigid registration method to register high-field preoperative MRI with low-field intra-operative MRI in order to recover the deformation induced by brain shift and tumor resection. The registered DTI and BOLD are fused with low-field intra-operative MRI for image-guided neurosurgery.Results
The proposed hybrid registration method was evaluated by comparing the landmarks predicted by the hybrid registration method with the landmarks identified in the low-field intra-operative MRI for 10 patients. The prediction error of the hybrid method is 1.92 ± 0.54 mm, and the compensation accuracy is 74.3 ± 5.0%. Compared to the landmarks far from the resection region, those near the resection region demonstrated a higher compensation accuracy (P-value = .003) although these landmarks had larger initial displacements.Conclusions
The proposed hybrid registration method is able to bring preoperatively acquired BOLD and DTI into the operating room and compensate for the deformation to augment low-field intra-operative MRI with rich anatomical and functional information. 相似文献58.
59.
石灰石在煤气化过程中的催化和固硫作用 总被引:1,自引:1,他引:1
基于CaO在煤气化中的催化和固硫作用,以及石灰石加热分解的性质,石灰石有可能作为煤气化过程中的催化剂和固硫剂。本文根据国内外对石灰石在煤燃烧和煤气化中作用的研究,从石灰石结构、Ca/C,Ca/S,可能的反应机理等几个方面进行了介绍和分析,并指出需进一步研究的内容。 相似文献
60.
Zhichao Huang Junfeng Yao Zichun Zhong Yang Liu Xiaohu Guo 《Computer Graphics Forum》2014,33(7):239-248
Sparse localized decomposition is a useful technique to extract meaningful deformation components out of a training set of mesh data. However, existing methods cannot capture large rotational motion in the given mesh dataset. In this paper we present a new decomposition technique based on deformation gradients. Given a mesh dataset, the deformation gradient field is extracted, and decomposed into two groups: rotation field and stretching field, through polar decomposition. These two groups of deformation information are further processed through the sparse localized decomposition into the desired components. These sparse localized components can be linearly combined to form a meaningful deformation gradient field, and can be used to reconstruct the mesh through a least squares optimization step. Our experiments show that the proposed method addresses the rotation problem associated with traditional deformation decomposition techniques, making it suitable to handle not only stretched deformations, but also articulated motions that involve large rotations. 相似文献