全文获取类型
收费全文 | 534044篇 |
免费 | 6470篇 |
国内免费 | 1294篇 |
专业分类
电工技术 | 10262篇 |
综合类 | 767篇 |
化学工业 | 78282篇 |
金属工艺 | 22456篇 |
机械仪表 | 18627篇 |
建筑科学 | 13101篇 |
矿业工程 | 2714篇 |
能源动力 | 13101篇 |
轻工业 | 44848篇 |
水利工程 | 5423篇 |
石油天然气 | 8265篇 |
武器工业 | 15篇 |
无线电 | 63336篇 |
一般工业技术 | 106808篇 |
冶金工业 | 93036篇 |
原子能技术 | 10458篇 |
自动化技术 | 50309篇 |
出版年
2021年 | 3600篇 |
2019年 | 3419篇 |
2018年 | 12871篇 |
2017年 | 13273篇 |
2016年 | 9894篇 |
2015年 | 4521篇 |
2014年 | 7037篇 |
2013年 | 21623篇 |
2012年 | 13639篇 |
2011年 | 22925篇 |
2010年 | 19351篇 |
2009年 | 20192篇 |
2008年 | 20386篇 |
2007年 | 22132篇 |
2006年 | 13066篇 |
2005年 | 15184篇 |
2004年 | 13401篇 |
2003年 | 12789篇 |
2002年 | 11502篇 |
2001年 | 11283篇 |
2000年 | 10926篇 |
1999年 | 11334篇 |
1998年 | 26974篇 |
1997年 | 19442篇 |
1996年 | 15303篇 |
1995年 | 11628篇 |
1994年 | 10667篇 |
1993年 | 10266篇 |
1992年 | 7833篇 |
1991年 | 7495篇 |
1990年 | 7220篇 |
1989年 | 7154篇 |
1988年 | 6948篇 |
1987年 | 5851篇 |
1986年 | 5899篇 |
1985年 | 6930篇 |
1984年 | 6359篇 |
1983年 | 5963篇 |
1982年 | 5310篇 |
1981年 | 5567篇 |
1980年 | 5121篇 |
1979年 | 5127篇 |
1978年 | 4973篇 |
1977年 | 5816篇 |
1976年 | 7599篇 |
1975年 | 4291篇 |
1974年 | 4146篇 |
1973年 | 4172篇 |
1972年 | 3424篇 |
1971年 | 3087篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
92.
Jincy Joy Jessica Pereira Rachida Aid‐Launais Graciela Pavon‐Djavid Alok R Ray Didier Letourneur Anne Meddahi‐Pell Bhuvanesh Gupta 《Polymer International》2019,68(7):1367-1377
The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry 相似文献
93.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
94.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
95.
A conceptualization of intended learning outcomes supporting self‐regulated learners in indicating learning paths 下载免费PDF全文
P. Tangworakitthaworn L. Gilbert G.B. Wills 《Journal of Computer Assisted Learning》2015,31(5):393-404
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs. 相似文献
96.
97.
98.
99.
100.