全文获取类型
收费全文 | 75175篇 |
免费 | 6843篇 |
国内免费 | 3528篇 |
专业分类
电工技术 | 4671篇 |
技术理论 | 10篇 |
综合类 | 4827篇 |
化学工业 | 12636篇 |
金属工艺 | 3971篇 |
机械仪表 | 4355篇 |
建筑科学 | 5402篇 |
矿业工程 | 1993篇 |
能源动力 | 2439篇 |
轻工业 | 4963篇 |
水利工程 | 1444篇 |
石油天然气 | 3581篇 |
武器工业 | 804篇 |
无线电 | 9660篇 |
一般工业技术 | 9281篇 |
冶金工业 | 4175篇 |
原子能技术 | 853篇 |
自动化技术 | 10481篇 |
出版年
2024年 | 335篇 |
2023年 | 1195篇 |
2022年 | 2423篇 |
2021年 | 3259篇 |
2020年 | 2391篇 |
2019年 | 2000篇 |
2018年 | 2276篇 |
2017年 | 2457篇 |
2016年 | 2260篇 |
2015年 | 2999篇 |
2014年 | 3664篇 |
2013年 | 4609篇 |
2012年 | 4831篇 |
2011年 | 5123篇 |
2010年 | 4567篇 |
2009年 | 4439篇 |
2008年 | 4292篇 |
2007年 | 4003篇 |
2006年 | 3942篇 |
2005年 | 3234篇 |
2004年 | 2530篇 |
2003年 | 2265篇 |
2002年 | 2378篇 |
2001年 | 2134篇 |
2000年 | 1776篇 |
1999年 | 1757篇 |
1998年 | 1570篇 |
1997年 | 1294篇 |
1996年 | 1115篇 |
1995年 | 912篇 |
1994年 | 711篇 |
1993年 | 568篇 |
1992年 | 416篇 |
1991年 | 343篇 |
1990年 | 246篇 |
1989年 | 238篇 |
1988年 | 188篇 |
1987年 | 124篇 |
1986年 | 122篇 |
1985年 | 97篇 |
1984年 | 45篇 |
1983年 | 35篇 |
1982年 | 48篇 |
1981年 | 45篇 |
1980年 | 42篇 |
1979年 | 35篇 |
1977年 | 24篇 |
1976年 | 33篇 |
1975年 | 27篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
15.
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。 相似文献
16.
Haibo Zhang Guohua Geng Kang Li Cheng Liu Yuqing Hou 《Journal of Modern Optics》2018,65(20):2278-2289
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?1) regularization was utilized for the efficient reconstruction for early detection of small tumour in CB-XLCT imaging. Specifically, we transformed the non-convex optimization problem into an iteratively reweighted scheme based on the L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?1) model. We studied eight different non-convex p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?1/2) methods give the best performance. 相似文献
17.
18.
Y S Cao C M Ang K S Raajeevan A K Kiran K C Lai S W Ng I Zulkifli Y L Wah 《Water science and technology》2006,54(8):237-246
This paper analyses the performance of the anaerobic selector (A/O process) in a full-scale activated sludge process receiving mostly industrial sewage discharge (> 60%) in Singapore. In addition to the sludge settleability, enhanced biological phosphorus removal (EBPR) was studied. The sludge volume index (SVI) reduced from 200 to 80 ml g(-1) and foaming was suppressed significantly, indicating the effectiveness of the anaerobic selector in improving sludge settleability. The phosphorus removal efficiency was 66%, and 7.5 mg HAc-COD was consumed per mg PO4(3-) -P removed. In the anaerobic compartment, 31% of the SCOD and 73% of the acetic acid in the settled sewage were removed with PO4(3-) -P release of 14.1 mg PO4(3-)-P l(-1). The linear correlation between PO4(3-) -P release in the anaerobic compartment and PO4(3-) -P uptake in the aerobic compartment indicates that there is about 0.8 mg PO4(3-) -P release in the anaerobic compartment per mg PO34(3-) -P uptake in the aerobic compartment. The fates of volatile fatty acids (VFAs) and its short chain acids (SCAs) in the process were studied and discussed. 相似文献
19.
Popular biorthogonal wavelet filters via a lifting scheme and its application in image compression 总被引:2,自引:0,他引:2
Cheng L. Liang D.L. Zhang Z.H. 《Vision, Image and Signal Processing, IEE Proceedings -》2003,150(4):227-232
A technique using a lifting scheme is presented for constructing compactly supported wavelets whose coefficients are composed of free variables locating in an interval. An efficient approach-based wavelet for image compression is developed by selecting the coefficients of the 9-7 wavelet filter and associated lifting scheme. Furthermore, the rationalised coefficients wavelet filter that can be implemented with simple integer arithmetic is achieved and its characteristic is close to the well known original irrational coefficients 9-7 wavelet filters developed by A. Cohen et al. (Commun. Pure Appl. Maths., vol.45, no.1, p.485-560, 1992). To reduce the computational cost of image coding applications further, an acceleration technique is proposed for the lifting steps. Software and hardware simulations show that the new method has very low complexity, and simultaneously preserves the high quality of the compressed image. 相似文献
20.
湘中海相浅层湘冷1井酸压工艺研究及应用 总被引:2,自引:0,他引:2
湘冷1井具有气层埋藏浅(400m-500m)、纵向上裂隙发育的特点,属低孔、低渗的含泥质灰岩致密储层。大量室内实验和研究采用“前置液酸压+闭合酸化”工艺技术,并优选了相应降阻酸和闭合酸配方。通过酸压实现了该井工业油气流的突破,取得了明显的增产效果,为新区海相浅层气的开发探索出了一套成熟的改造增产措施。 相似文献