全文获取类型
收费全文 | 27197篇 |
免费 | 192篇 |
国内免费 | 9篇 |
专业分类
教育 | 20127篇 |
科学研究 | 2537篇 |
各国文化 | 114篇 |
体育 | 1634篇 |
综合类 | 9篇 |
文化理论 | 487篇 |
信息传播 | 2490篇 |
出版年
2021年 | 127篇 |
2020年 | 196篇 |
2019年 | 334篇 |
2018年 | 2592篇 |
2017年 | 2546篇 |
2016年 | 1987篇 |
2015年 | 384篇 |
2014年 | 459篇 |
2013年 | 3008篇 |
2012年 | 577篇 |
2011年 | 1157篇 |
2010年 | 1134篇 |
2009年 | 688篇 |
2008年 | 1018篇 |
2007年 | 1452篇 |
2006年 | 403篇 |
2005年 | 611篇 |
2004年 | 679篇 |
2003年 | 557篇 |
2002年 | 373篇 |
2001年 | 336篇 |
2000年 | 321篇 |
1999年 | 272篇 |
1998年 | 139篇 |
1997年 | 189篇 |
1996年 | 181篇 |
1995年 | 189篇 |
1994年 | 147篇 |
1993年 | 165篇 |
1992年 | 251篇 |
1991年 | 224篇 |
1990年 | 215篇 |
1989年 | 246篇 |
1988年 | 252篇 |
1987年 | 212篇 |
1986年 | 208篇 |
1985年 | 223篇 |
1984年 | 202篇 |
1983年 | 237篇 |
1982年 | 177篇 |
1981年 | 161篇 |
1980年 | 163篇 |
1979年 | 232篇 |
1978年 | 186篇 |
1977年 | 165篇 |
1976年 | 151篇 |
1975年 | 128篇 |
1974年 | 119篇 |
1973年 | 125篇 |
1971年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
1 Introduction Duringthe past several decades ,considerable atten-tion has been given to devising methods for solvingconstrained opti mization problemsviaunconstrainedmini mization techniques and a number of researchwork in the area of nonlinear programmi… 相似文献
172.
173.
174.
Christopher P. Dwyer 《Irish Educational Studies》2019,38(2):213-217
This review examines Psychology and the Study of Education: Critical Perspectives on Developing Theories, a collection of academic articles edited by Cathal Ó Siochrú. The collection comprehensively considers wide-ranging topics pertinent to the psychology of education, with a target audience of educators and students wishing to learn more about psychology. The review evaluates the collection as an integrated work of entries and analyses each component chapter; recognising the success of the collection with respect to its aim of challenging readers to critically reflect upon and consider the value of psychology in both understanding and influencing education. The book transcends the common formula of academic article collections in this area by being presented in a somewhat conversational manner, making it both interesting and accessible. The book is recommended for anyone interested in the psychology of education and for anyone who values the advancement of learning and teaching. 相似文献
175.
176.
177.
The paper describes the design and use of a studio system which arose out of the need to give demonstrations of experimental procedures to practical classes of up to 150 students. Since the requirements could be specified in some detail it was possible to use novel methods of working which turned out to be very efficient and economical. 相似文献
178.
Willi Dörfler 《Educational Studies in Mathematics》2003,54(2-3):147-170
A broad view of mathematics education takes it as the study of how people learn and do mathematics. Starting with this view, the actual and potential relationships of mathematics education as are search discipline to mathematics as a field of knowledge and activity and to the mathematicians carrying out that activity are analyzed. This leads to the picture of a gulf between the two scientific communities which are based in different cultures of thinking and research. A (meta-)study of mathematics and all its facets termed here mathematicology is proposed. It could serve as common ground for cooperative studies by mathematicians and mathematics educators. Thereby the gulf will not necessarily become narrower but abridge over the differences and mutual misunderstandings could be built. 相似文献
179.
180.
Takashi Sagawa 《浙江大学学报(A卷英文版)》2018,19(1):80-85
Composite materials of Fe/Al2O3, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al2O3 is one of the promising candidates for re-transformation of exhausted CO2 into fuels such as alcohols and hydrocarbons. The development of a CO2 reforming system using the composite materials of Fe/Al2O3 through CO2 reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO2 produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H2 from CO2 and water were obtained. However, this CO2 reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO2 reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH4, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO2 was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO2 conversion reduced half of the Fe, the selectivity of CO from CO2 increased to 95% in the case of Cu. 相似文献