全文获取类型
收费全文 | 360318篇 |
免费 | 6752篇 |
国内免费 | 2354篇 |
专业分类
电工技术 | 6470篇 |
技术理论 | 5篇 |
综合类 | 3488篇 |
化学工业 | 57308篇 |
金属工艺 | 16179篇 |
机械仪表 | 11331篇 |
建筑科学 | 9086篇 |
矿业工程 | 2245篇 |
能源动力 | 8141篇 |
轻工业 | 30621篇 |
水利工程 | 4260篇 |
石油天然气 | 6415篇 |
武器工业 | 244篇 |
无线电 | 39038篇 |
一般工业技术 | 68927篇 |
冶金工业 | 51242篇 |
原子能技术 | 6020篇 |
自动化技术 | 48404篇 |
出版年
2022年 | 2492篇 |
2021年 | 3701篇 |
2020年 | 2617篇 |
2019年 | 3111篇 |
2018年 | 18412篇 |
2017年 | 17122篇 |
2016年 | 14239篇 |
2015年 | 4019篇 |
2014年 | 5692篇 |
2013年 | 13164篇 |
2012年 | 11671篇 |
2011年 | 20312篇 |
2010年 | 16936篇 |
2009年 | 14828篇 |
2008年 | 16692篇 |
2007年 | 17603篇 |
2006年 | 9045篇 |
2005年 | 8884篇 |
2004年 | 8019篇 |
2003年 | 7577篇 |
2002年 | 6919篇 |
2001年 | 6598篇 |
2000年 | 6260篇 |
1999年 | 6122篇 |
1998年 | 13240篇 |
1997年 | 9833篇 |
1996年 | 7551篇 |
1995年 | 5723篇 |
1994年 | 5268篇 |
1993年 | 5120篇 |
1992年 | 4073篇 |
1991年 | 3915篇 |
1990年 | 3941篇 |
1989年 | 3867篇 |
1988年 | 3625篇 |
1987年 | 3124篇 |
1986年 | 3129篇 |
1985年 | 3506篇 |
1984年 | 3396篇 |
1983年 | 3157篇 |
1982年 | 2764篇 |
1981年 | 2982篇 |
1980年 | 2700篇 |
1979年 | 2870篇 |
1978年 | 2772篇 |
1977年 | 2877篇 |
1976年 | 3737篇 |
1975年 | 2472篇 |
1974年 | 2302篇 |
1973年 | 2337篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
103.
104.
105.
106.
107.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
108.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献
109.
Catalysis Letters - In this work we studied the reactivity of the Trifluoroacetic acid hydroxylamine system in the one step salt free synthesis of amides from ketones. A particular regards was paid... 相似文献
110.
Kumari Asha Neeraj Kumar Biswas Sakshi Saxena Vibha Rani Satsangi Rohit Shrivastav Rama Kant Sahab Dass 《International Journal of Hydrogen Energy》2021,46(40):20858-20870
The present study attempts quantitative determination of changes in the morphological surface features viz. fractal dimension, lower and upper cut off length scale through Power Spectral Density analysis prior to and after irradiation of 100 KeV Ar+ ion beam at incidence angles of 0°, 40° and 60° on ZnO thin films. All the unirradiated and irradiated samples are subjected to photoelectrochemical characterization and a correlation between photoelectrochemical performance and morphological parameters is established. Sample irradiated at 40° angle at the fluence of 5 × 1016 ions/cm2 is found to possess maximum fractal dimension of 2.72, lower and upper cut off length scale of 3.16 nm and 63.00 nm respectively. This sample exhibits maximum photocurrent density of 3.19 mA/cm2 and applied bias photon-to-current efficiency of 1.12% at 1.23 V/RHE. Hydrogen gas collected for duration of 1 h for the same sample was ~4.83 mLcm?2. 相似文献