全文获取类型
收费全文 | 518篇 |
免费 | 10篇 |
专业分类
化学 | 246篇 |
晶体学 | 4篇 |
力学 | 31篇 |
数学 | 40篇 |
物理学 | 207篇 |
出版年
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 13篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1972年 | 4篇 |
1971年 | 7篇 |
1970年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有528条查询结果,搜索用时 15 毫秒
131.
132.
133.
The reaction of hexachlorotropone with trimethylsilylethynyl-lithium leads to contraction of the seven-membered ring via a semibenzilic acid rearrangement to yield pentachlorophenyl trimethylsilylethynyl ketone, 4. Treatment of 4 with dicobalt octacarbonyl yields the corresponding alkyne-dicobalt hexacarbonyl, 6, which has been characterized by X-ray crystallography. 相似文献
134.
135.
136.
137.
Michelle A. Meierhoefer Matthew J. Walters S. Patrick Dunn Jarrett H. Vella Bonnie J. Grant Carolyn L. Sober Nidhi S. Patel Laela M. Hajiaghamohseni Sara B. Lioi Clyde R. Metz Charles F. Beam William T. Pennington Donald G. Vanderveer N. Dwight Camper 《Journal of heterocyclic chemistry》2006,43(2):307-313
138.
Corticotropin-releasing factor (CRF), CRF-related peptides and their receptors are present in the central nervous system and in peripheral tissues including the immune, reproductive and cardiovascular systems. CRF and urocortin (urocortin 1) bind to the CRF receptor type 1 (CRF(1) receptor) and the CRF receptor type 2 (CRF(2) receptor), whereas urocortin 2 (formerly known as stresscopin related peptide) and urocortin 3 (formerly known as stresscopin) bind with high affinity to the CRF(2) receptor. Recent studies show that urocortin 1, urocortin 2 and urocortin 3 are potent regulators of cardiovascular function. This review highlights the role of cardiovascular CRF and related peptides and its relevance in mediating the adaptive response of the cardiovascular system to stressful conditions. 相似文献
139.
We present a new instrument, based on a low-frame-rate (8 Hz) CCD camera used in a heterodyne optical-mixing configuration, that can create wide-field laser Doppler maps. As an illustration, we show results obtained in a mouse brain, in vivo, showing the Doppler signature of blood flow. The instrument is based on a frequency-shifting digital holography scheme. 相似文献
140.
Michelle Dunn Wendy Scott 《International Journal of Mathematical Education in Science & Technology》2018,49(1):31-45
First-year engineering students often struggle to see the relevance of theoretical mathematical concepts for their future studies and professional careers. This is an issue, as students who do not see relevance in fundamental parts of their studies may disengage from these parts and focus their efforts on other subjects they think will be more useful to them. In this study, we surveyed engineering students enrolled in a first-year mathematics subject on their perceptions of the relevance of the individual mathematical topics taught. Surveys were administered at the start of semester when some of these topics were unknown to them, and again at the end of semester when students had not only studied all these topics but also watched a set of animated videos. These videos had been produced by higher-year students to explain where they had seen applications of the mathematical concepts presented in the first year. We notice differences between the perceived relevance of topics for future study and for professional careers, with relevance to study rated higher than relevance to careers. We also find that the animations are seen as helpful in understanding the relevance of first-year mathematics. The majority of students indicated that lecturers with students as partners should work collaboratively to produce future videos. 相似文献