全文获取类型
收费全文 | 13785篇 |
免费 | 1006篇 |
国内免费 | 488篇 |
专业分类
电工技术 | 667篇 |
综合类 | 681篇 |
化学工业 | 2255篇 |
金属工艺 | 682篇 |
机械仪表 | 816篇 |
建筑科学 | 884篇 |
矿业工程 | 332篇 |
能源动力 | 411篇 |
轻工业 | 744篇 |
水利工程 | 176篇 |
石油天然气 | 851篇 |
武器工业 | 72篇 |
无线电 | 1816篇 |
一般工业技术 | 1687篇 |
冶金工业 | 1402篇 |
原子能技术 | 89篇 |
自动化技术 | 1714篇 |
出版年
2024年 | 33篇 |
2023年 | 211篇 |
2022年 | 318篇 |
2021年 | 507篇 |
2020年 | 327篇 |
2019年 | 296篇 |
2018年 | 336篇 |
2017年 | 376篇 |
2016年 | 351篇 |
2015年 | 486篇 |
2014年 | 660篇 |
2013年 | 800篇 |
2012年 | 771篇 |
2011年 | 926篇 |
2010年 | 777篇 |
2009年 | 715篇 |
2008年 | 759篇 |
2007年 | 689篇 |
2006年 | 747篇 |
2005年 | 665篇 |
2004年 | 424篇 |
2003年 | 365篇 |
2002年 | 296篇 |
2001年 | 276篇 |
2000年 | 275篇 |
1999年 | 415篇 |
1998年 | 558篇 |
1997年 | 374篇 |
1996年 | 345篇 |
1995年 | 238篇 |
1994年 | 201篇 |
1993年 | 151篇 |
1992年 | 106篇 |
1991年 | 77篇 |
1990年 | 67篇 |
1989年 | 51篇 |
1988年 | 44篇 |
1987年 | 21篇 |
1986年 | 40篇 |
1985年 | 18篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 24篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1977年 | 34篇 |
1976年 | 54篇 |
1975年 | 6篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Hongen Liao Hata N. Nakajima S. Iwahara M. Sakuma I. Dohi T. 《IEEE transactions on information technology in biomedicine》2004,8(2):114-121
This paper describes an autostereoscopic image overlay technique that is integrated into a surgical navigation system to superimpose a real three-dimensional (3-D) image onto the patient via a half-silvered mirror. The images are created by employing a modified version of integral videography (IV), which is an animated extension of integral photography. IV records and reproduces 3-D images using a microconvex lens array and flat display; it can display geometrically accurate 3-D autostereoscopic images and reproduce motion parallax without the need for special devices. The use of semitransparent display devices makes it appear that the 3-D image is inside the patient's body. This is the first report of applying an autostereoscopic display with an image overlay system in surgical navigation. Experiments demonstrated that the fast IV rendering technique and patient-image registration method produce an average registration accuracy of 1.13 mm. Experiments using a target in phantom agar showed that the system can guide a needle toward a target with an average error of 2.6 mm. Improvement in the quality of the IV display will make this system practical and its use will increase surgical accuracy and reduce invasiveness. 相似文献
92.
Zheng Liu Mingqin Xuan Zhaohui Zhao Yufeng Cong Kejian Liao 《Petroleum Science and Technology》2003,21(7):1317-1325
In this article, the compatibilities between different components of a base asphalt and styrene butadiene styrene (SBS) have been analyzed from microscopic structures. Specifically, the asphalt was separated into three components: saturates, aromatics, and resins, by Solvent Recycled Absorption Chromatography Separation Technology (SRACST). The compatibilities between these different components and the polymer were compared with the help of Fluorescence Microscope (FM) with which the existing state of the polymer SBS in these different components could be examined obviously. The modified effects indicated that aromatics could cause SBS swollen and, resins dissolved SBS better than saturates, though both the two components could partially dissolve SBS and the two mixtures presented two immiscible phase systems. In order to further investigate the compatibility between aromatics and SBS, from macroscopic properties, an additive rich in aromatics was added to the SBS/asphalt mixture, and the result was satisfactory. 相似文献
93.
Yong Chen Xiaofeng Liao Kwok-Wo Wong 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(7):527-529
An encryption system with discretized skew tent map has been proposed recently by N. Masuda . However, there is a fundamental weakness with this chaotic cryptographic scheme. In this paper, a chosen plaintext attack requiring only two plaintexts is proposed. An improved version of this attack that narrows the key space need to be searched is also suggested. The test results demonstrate that this encryption cryptosystem is easily broken under the proposed chosen plaintext attack. 相似文献
94.
95.
Problems that arise from health-care management, rather than from a disease process, are now recognized as making a substantial contribution to patient morbidity and mortality and to the cost of health care. However, most classifications of these problems do not provide sufficient detail to allow comparisons or to develop better strategies for the prevention, detection and management of these problems. A 'Generic Occurrence Classification' was developed to record their salient features, place them in context and elicit any system or human error-based contributing factors. This was done by an iterative process in which 'natural categories', identified from over 2000 incidents and 800 adverse events, were placed in a hierarchical structure created using software written in Microsoft Visual Basic; data were stored in a Microsoft Access database. This was shown to be a valid and reliable way to compare incidents and accidents from different sources and to allow sufficient detail to be retrieved to develop preventive strategies. 相似文献
96.
四坐标数控加工原理及算法研究 总被引:2,自引:0,他引:2
本文对四坐标数控加工原理和算法作了详细介绍,尤其对四坐标加工的刀轴矢量算法进行了研究,提出了用垂直于回转轴的平面与刀具运动方向和前导角形成的圆锥面求交,生成刀轴矢量的方法,该方法具有立意新颖、思路清晰,性能可靠,易于在微机上实现等特点,对复杂曲面零件的加工编程,具有重要的实用价值。 相似文献
97.
98.
99.
M Terpstra WB High Y Luo RA de Graaf H Merkle M Garwood 《Canadian Metallurgical Quarterly》1996,9(5):185-194
Increased capacity for glycolytic metabolism is a well-known characteristic of neoplastic cells. Because lactic acid is the end product of glycolysis, in vivo MRS measurements of tumor lactate concentration ([lac]t) may provide valuable information about tumor metabolism, which will aid the development of therapies and the clinical diagnosis and treatment of tumors. In the present study, several hemodynamic and histologic parameters were evaluated with respect to their influence on [lac]t. Pronounced differences in [lac]t in two distinct populations of tumors suggested a putative perfusion threshold. Above this threshold, [lac]t was independent of hemodynamic and histologic factors including tumor blood flow (measured using MRS and the method of D2O washout), extent of necrosis and inflammatory cell infiltrate. Thus, for most tumors, [lac]t was not determined by any one single factor such as hypoxia, venous clearance, glucose supply, extent of necrosis or degree of inflammatory cell infiltrate. Rather, [lac]t may be equilibrated, at least in part, by an interplay of forces involving hemodynamics and substrate supply. In general, the data are consistent with the hypothesis that elevated lactate in most tumors is related to the high glycolytic activity of adequately perfused, viable neoplastic cells. 相似文献
100.