全文获取类型
收费全文 | 1379950篇 |
免费 | 29671篇 |
国内免费 | 7801篇 |
专业分类
化学 | 696140篇 |
晶体学 | 20476篇 |
力学 | 75671篇 |
综合类 | 106篇 |
数学 | 244327篇 |
物理学 | 380702篇 |
出版年
2021年 | 13561篇 |
2020年 | 15964篇 |
2019年 | 16099篇 |
2018年 | 14024篇 |
2016年 | 28550篇 |
2015年 | 20936篇 |
2014年 | 30521篇 |
2013年 | 74471篇 |
2012年 | 40228篇 |
2011年 | 39161篇 |
2010年 | 38528篇 |
2009年 | 40502篇 |
2008年 | 37695篇 |
2007年 | 33828篇 |
2006年 | 38422篇 |
2005年 | 31484篇 |
2004年 | 32136篇 |
2003年 | 29887篇 |
2002年 | 30657篇 |
2001年 | 30774篇 |
2000年 | 26144篇 |
1999年 | 23148篇 |
1998年 | 21259篇 |
1997年 | 21149篇 |
1996年 | 21215篇 |
1995年 | 19270篇 |
1994年 | 18717篇 |
1993年 | 18302篇 |
1992年 | 18573篇 |
1991年 | 18786篇 |
1990年 | 18004篇 |
1989年 | 18034篇 |
1988年 | 17638篇 |
1987年 | 17568篇 |
1986年 | 16515篇 |
1985年 | 22871篇 |
1984年 | 23982篇 |
1983年 | 20098篇 |
1982年 | 21722篇 |
1981年 | 20959篇 |
1980年 | 20286篇 |
1979年 | 20601篇 |
1978年 | 21802篇 |
1977年 | 21422篇 |
1976年 | 21135篇 |
1975年 | 19841篇 |
1974年 | 19494篇 |
1973年 | 19907篇 |
1972年 | 14426篇 |
1967年 | 12654篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Leila Torkian Mostafa M. Amini Tayebeh Gorji Omid Sadeghi 《Arabian Journal of Chemistry》2019,12(7):1315-1321
In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples. 相似文献
192.
Adly M. E. Gedawy E. M. El-Malah A. A. El-Telbany F. A. 《Russian Journal of Organic Chemistry》2019,55(8):1189-1196
Russian Journal of Organic Chemistry - Selenopheno[2,3-d]pyrimidine- and selenopheno[2,3-d][1,2,3]triazine-containing compounds were synthesized starting from... 相似文献
193.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor. 相似文献
194.
Manjumol K. A. Jayasankar M. Vidya K. Mohamed A. Peer Nair Balagopal N. Warrier K. G. K. 《Journal of Sol-Gel Science and Technology》2015,74(1):161-167
Journal of Sol-Gel Science and Technology - High temperature stable brookite rich titanium dioxide of average crystallite size 20&;nbsp;nm has been prepared by a novel aqueous sol–gel... 相似文献
195.
Saleh Z. M. Nasser H. Özkol E. Günöven M. Abak K. Canli S. Bek A. Turan R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting... 相似文献
196.
197.
Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015) 下载免费PDF全文
198.
199.
200.
A protocol to correct for intra‐ and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line 下载免费PDF全文