全文获取类型
收费全文 | 20736篇 |
免费 | 3952篇 |
国内免费 | 3384篇 |
专业分类
化学 | 15696篇 |
晶体学 | 365篇 |
力学 | 1329篇 |
综合类 | 241篇 |
数学 | 2388篇 |
物理学 | 8053篇 |
出版年
2024年 | 49篇 |
2023年 | 353篇 |
2022年 | 680篇 |
2021年 | 752篇 |
2020年 | 812篇 |
2019年 | 848篇 |
2018年 | 752篇 |
2017年 | 732篇 |
2016年 | 1073篇 |
2015年 | 1172篇 |
2014年 | 1312篇 |
2013年 | 1648篇 |
2012年 | 1965篇 |
2011年 | 2023篇 |
2010年 | 1514篇 |
2009年 | 1488篇 |
2008年 | 1516篇 |
2007年 | 1304篇 |
2006年 | 1230篇 |
2005年 | 1085篇 |
2004年 | 871篇 |
2003年 | 696篇 |
2002年 | 820篇 |
2001年 | 690篇 |
2000年 | 481篇 |
1999年 | 401篇 |
1998年 | 345篇 |
1997年 | 251篇 |
1996年 | 204篇 |
1995年 | 186篇 |
1994年 | 149篇 |
1993年 | 126篇 |
1992年 | 112篇 |
1991年 | 107篇 |
1990年 | 69篇 |
1989年 | 43篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 8篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Bamboo-shaped Ag-doped TiO2 nanowires with heterojunctions were synthesized by a simple solvothermal method. The diameter of the nanowires was about 50-100 nm, and they had a length of up to a few millimeters. The detailed structure of the heterojunction in the nanowire was also characterized. 相似文献
92.
Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O(2). The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (approximately 700 degrees C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (approximately 800 degrees C). Both nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies. 相似文献
93.
综述了1β-Methyl Carbapenem中间体的合成方法,重点强调了如何构筑1位β构型的甲基。参考文献37篇。 相似文献
94.
95.
96.
ResearchonCrystalStructureoftheComplexof10-Hydroxy-10-(3-indolyl)-9-phenanthrenonewithTetrahydrofuranMengJi-Ben;WenZhong;Wang... 相似文献
97.
研究了导电聚合物聚(3-丁基噻吩)(PBT)在大气环境下的导电热稳定性。在室温至220℃范围内,测试电导率随时间及温度的变化。TGA分析以及化学分析的结果表明:掺杂态的PBT大约在140℃附近有一转化温度,低于或高于这一转化温度,电导率下降的决定因素各不相同。高于转化温度时,电导率下降的主要原因是反离子和高分子主链的解离,进而发生化学反应,影响了高分子主链的结构。XPS测试结果表明:经热处理后的P 相似文献
98.
Youyi Sun Hongfang Jiu Douguo Zhang Jiangang Gao Bin Guo Qijin Zhang 《Chemical physics letters》2005,410(4-6):204-208
Ag colloidal nanoparticles coated with Eu(TTA)3 · 2H2O complexes were prepared, and it was found that Eu(TTA)3 · 2H2O complexes J-aggregate was formed on the surface of Ag nanoparticles according to a red shift (18.2 nm) in UV–Vis spectra. However, there had similar excitation wavelength, which was attributed to existence of Ag nanoparticles. Highly luminescent properties of Ag colloidal nanoparticles were observed, and it was believed to result from low energy transfer between Eu(III) complexes and Ag and the large electromagnetic field arising from the excitation of surface plasmon polariton of Ag nanoparticles. 相似文献
99.
Yuanyuan Han Qinghai Cai Bin Lu Xue Xiao Shuhan Cui 《Reaction Kinetics and Catalysis Letters》2007,91(1):29-35
A novel solid acid prepared from concentrated sulfuric, boric and phosphoric acid is a highly selective catalyst for the dimerization
of α-methylstyrene at room temperature to generate 4-methyl-2,4-diphenyl-1-pentene. 相似文献
100.
WenXiangHU XueJunHOU QingTaoPENG 《中国化学快报》2002,13(12):1199-1202
In this paper,a new HPLC method was established to determine the earbonyl compounds in air.As the absorbent,2,4-dinitrophenylhydrazint(2,4-DNPH)reaeted with earbonyls specifieally,which form the corresponding 2,4-dinitrophenylhydrazones,then analyzed by HPLC.The chromatographic conditions,the recovery rate,stability of samples,reagent blank,sampling efficiency were all studied systematically.The results showed that this established method had high sensitivity and good selectivity compared with other analytical methods,and it can detemine ten earbonyl compounds in air in 26 min simultancously. 相似文献