全文获取类型
收费全文 | 1767篇 |
免费 | 95篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 505篇 |
金属工艺 | 45篇 |
机械仪表 | 23篇 |
建筑科学 | 50篇 |
矿业工程 | 2篇 |
能源动力 | 50篇 |
轻工业 | 292篇 |
水利工程 | 8篇 |
石油天然气 | 7篇 |
无线电 | 129篇 |
一般工业技术 | 331篇 |
冶金工业 | 138篇 |
原子能技术 | 4篇 |
自动化技术 | 264篇 |
出版年
2023年 | 13篇 |
2022年 | 40篇 |
2021年 | 58篇 |
2020年 | 43篇 |
2019年 | 55篇 |
2018年 | 41篇 |
2017年 | 46篇 |
2016年 | 41篇 |
2015年 | 52篇 |
2014年 | 60篇 |
2013年 | 130篇 |
2012年 | 123篇 |
2011年 | 142篇 |
2010年 | 77篇 |
2009年 | 94篇 |
2008年 | 78篇 |
2007年 | 95篇 |
2006年 | 75篇 |
2005年 | 56篇 |
2004年 | 59篇 |
2003年 | 51篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 30篇 |
1999年 | 32篇 |
1998年 | 53篇 |
1997年 | 42篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 2篇 |
排序方式: 共有1865条查询结果,搜索用时 31 毫秒
1.
Alberto Ballesteros Ester Laguna-Gutierrez Paula Cimavilla-Roman Maria Luisa Puertas Antonio Esteban-Cubillo Julio Santaren Miguel Angel Rodriguez-Perez 《应用聚合物科学杂志》2021,138(46):51373
In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear rheology and X-ray micro-computed tomography. Sepiolites treated with quaternary ammonium salts (O-QASEP) are better dispersed in the PS matrix than natural sepiolites (N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A percolated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEP and 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O-QASEP present the lowest cell size and the most homogeneous cellular structures. 相似文献
2.
This paper presents a brief overview of recent approaches to two problems in music information retrieval: query by example and automated source separation. It describes the challenges inherent in musical query by example and the systems that take very different approaches to the problem. The paper also explores approaches to source separation in a musical context, focusing on systems that take distinct approaches to the problem. Finally, it comments about the future directions for digital signal processing (DSP) research in the context of music information retrieval. 相似文献
3.
Varani L. Reggiani L. Kuhn T. Gonzalez T. Pardo D. 《Electron Devices, IEEE Transactions on》1994,41(11):1916-1925
We present a microscopic interpretation of electronic noise in semiconductor materials and two-terminal devices. The theory is based on Monte Carlo simulations of the carrier motion self-consistently coupled with a Poisson solver. Current and voltage noise operations are applied and their respective representations discussed. As application we consider the cases of homogeneous materials, resistors, n+nn + structures, and Schottky-barrier diodes. Phenomena associated with coupling between fluctuations in carrier velocity and self-consistent electric field are quantitatively investigated for the first time. At increasing applied fields hot-carrier effects are found to be of relevant importance in all the cases considered here. As a general result, noise spectroscopy is found to be a source of valuable information to investigate and characterize transport properties of semiconductor materials and devices 相似文献
4.
5.
A theoretical approach for the interpretation of the kinetics of simultaneous stable and metastable phase precipitation in
a binary system is proposed. The model, based on the nucleation and growth theory, defines a critical size different for each
phase. The size of the clusters evolves by adding or substracting a single atom one at a time. A set of coupled differential
equations is obtained for the chemical rate whose solution reproduces the kinetics of thermoelectric power measurements in
the Fe-C multiphase system. Suppositions about the growing and dissolution rate constants reduce the size of the equation
system with a gain in computation time. 相似文献
6.
Nguyen-Huy Dung Pardo Marie-Paule Dogguy.Smiri Leïla 《Materials Research Bulletin》1982,17(3):293-300
The Mn0.23Ga1.85S3 phase belongs to the solid solution , stable at low temperature in the Ga2S3MnS system. It is hexagonal superstructure of the wurtzite, with the Ga2S3α′ type (; Z = 6; space groupe P61 or P65). Its crystal structure has been refined by the least squares method to a final R = 0.06 with 323 independant reflections. This structure is closely related to Ga2S3 α described by Hahn and Frank, and differs only by the partial occupation of the vacant metal site of Ga2S3 by Mn atoms in statistical disorder. 相似文献
7.
8.
A CMOS log-polar image sensor has been designed and fabricated. As a result, a systematic approach has been proposed to design space-variant sensors and layouts. The pixels in this sensor are distributed in a polar fashion; the image plane consists of concentric rings containing the elementary sensing cells. Such a structure, where polygons use any space orientation, does not match very well with current design tools and CMOS fabrication processes. An approach to design nonorthogonal repetitive structures using standard fabrication processes and computer-aided design (CAD) tools is presented. The result of this work is an image sensor, with log-polar structure, suitable for image processing since the log-polar mapping has interesting mathematical and image data reduction properties 相似文献
9.
In this work we present a snake based approach for the segmentation of images of computerized tomography (CT) scans. We introduce a new term for the internal energy and another one for external energy which solve common problems associated with classical snakes in this type of images. A simplified minimizing method is also presented. 相似文献
10.
Antonio J. Pérez-López José Manuel López-Nicolás Angel A. Carbonell-Barrachina 《European Food Research and Technology》2007,225(2):255-260
Consumers demand organic products because they believe that the organic products are more flavorful and respectful to the
environment and human health. The effects of organic farming on the minerals contents and aroma composition of Clemenules
mandarin juices were studied. Minerals (Fe, Cu, Mn, Zn, Ca, Mg, K, and Na) were quantified using atomic absorption-emission
spectroscopy, while volatile compounds were extracted using the dynamic headspace technique and were identified and quantified
by GC–MS. In general, organic farming produced a mandarin juice with a higher quality than that produced by conventional agricultural
practices. Higher concentrations of both minerals and positive volatile compounds were found in the organic juice, while the
formation of off-flavors was higher in the conventional juice, although threshold values were not reached. 相似文献