全文获取类型
收费全文 | 283791篇 |
免费 | 5942篇 |
国内免费 | 1851篇 |
学科分类
工业技术 | 291584篇 |
出版年
2021年 | 2920篇 |
2020年 | 2056篇 |
2019年 | 2441篇 |
2018年 | 4124篇 |
2017年 | 4045篇 |
2016年 | 4456篇 |
2015年 | 3471篇 |
2014年 | 5347篇 |
2013年 | 12846篇 |
2012年 | 8818篇 |
2011年 | 11307篇 |
2010年 | 9082篇 |
2009年 | 9606篇 |
2008年 | 10509篇 |
2007年 | 10576篇 |
2006年 | 9107篇 |
2005年 | 7972篇 |
2004年 | 7089篇 |
2003年 | 6598篇 |
2002年 | 6570篇 |
2001年 | 6600篇 |
2000年 | 6177篇 |
1999年 | 6241篇 |
1998年 | 14805篇 |
1997年 | 10709篇 |
1996年 | 8081篇 |
1995年 | 6032篇 |
1994年 | 5475篇 |
1993年 | 5306篇 |
1992年 | 4085篇 |
1991年 | 3857篇 |
1990年 | 3919篇 |
1989年 | 3859篇 |
1988年 | 3610篇 |
1987年 | 3120篇 |
1986年 | 3131篇 |
1985年 | 3580篇 |
1984年 | 3458篇 |
1983年 | 3189篇 |
1982年 | 2785篇 |
1981年 | 3022篇 |
1980年 | 2775篇 |
1979年 | 2924篇 |
1978年 | 2816篇 |
1977年 | 3022篇 |
1976年 | 4103篇 |
1975年 | 2517篇 |
1974年 | 2351篇 |
1973年 | 2408篇 |
1972年 | 2008篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Gonzalez L. Julio C. Li Wei Gong Yu Jin XueJun 《Metallurgical and Materials Transactions B》2019,50(3):1417-1427
Metallurgical and Materials Transactions B - This paper reports a Galerkin finite-element analysis of carbon partitioning from martensite into austenite during the quenching and partitioning... 相似文献
82.
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
83.
84.
85.
86.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
87.
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
88.
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