全文获取类型
收费全文 | 1071篇 |
免费 | 203篇 |
国内免费 | 322篇 |
专业分类
化学 | 1448篇 |
晶体学 | 24篇 |
力学 | 20篇 |
综合类 | 8篇 |
物理学 | 96篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 58篇 |
2019年 | 49篇 |
2018年 | 37篇 |
2017年 | 31篇 |
2016年 | 70篇 |
2015年 | 65篇 |
2014年 | 48篇 |
2013年 | 97篇 |
2012年 | 71篇 |
2011年 | 51篇 |
2010年 | 42篇 |
2009年 | 53篇 |
2008年 | 55篇 |
2007年 | 63篇 |
2006年 | 58篇 |
2005年 | 81篇 |
2004年 | 76篇 |
2003年 | 76篇 |
2002年 | 68篇 |
2001年 | 36篇 |
2000年 | 45篇 |
1999年 | 36篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 36篇 |
1995年 | 38篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 28篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1596条查询结果,搜索用时 281 毫秒
151.
In-situ TEM observation of the evolution of helium bubbles in Mo during He+ irradiation and post-irradiation annealing
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yi-Peng Li 《中国物理 B》2021,30(8):86109-086109
The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy (TEM) during 30 keV He+ irradiation (at 673 K and 1173 K) and post-irradiation annealing (after 30 keV He+ irradiation with the fluence of 5.74×1016 He+/cm2 at 673 K). Both He+ irradiation and subsequently annealing induced the initiation, aggregation, and growth of helium bubbles. Temperature had a significant effect on the initiation and evolution of helium bubbles. The higher the irradiation temperature was, the larger the bubble size at the same irradiation fluence would be. At 1173 K irradiation, helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size, which would induce the formation of microcracks. At the same time, the geometry of helium bubbles changed from sphericity to polyhedron. The polyhedral bubbles preferred to grow in the shape bounded by {100} planes. After statistical analysis of the characteristic parameters of helium bubbles, the functions between the average size, number density of helium bubbles, swelling rate and irradiation damage were obtained. Meanwhile, an empirical formula for calculating the size of helium bubbles during the annealing was also provided. 相似文献
152.
Single crystals of the title compound are obtained from a melt of U3O8, MoO3, and excess Cs2CO3 (Pt crucible, 950 °C, 12 h, cooling rate 5 °C/h). 相似文献
153.
XPS study of potassium-promoted molybdenum carbides for mixed alcohols synthesis via CO hydrogenation
下载免费PDF全文
![点击此处可从《天然气化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both β-Mo_2C and α-MoC_(1-x) pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied. XPS results revealed that the content of surface Mo and its valence distribution between β-Mo_2C and α-MoC_(1-x) were quite different. Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over β-Mo_2C. Potassium had strong electronic effect on β-Mo_2C, which led to a higher Mo~(4+) content. On the contrary, potassium had little electronic effect on α-MoC_(1-x), and K-Mo interaction was weak. Therefore, Mo~0 and Mo~(2+) became the dominant species on the catalyst surface, and the Mo~(4+) content showed almost no increase as the pretreatment temperature enhanced. In terms of catalytic performance of molybdenum carbides, the increase in Mo~0 most likely explained the increase in hydrocarbon selectivity, yet Mo~(4+) might be responsible for the alcohols synthesis. 相似文献
154.
155.
介孔碳担载的 Co-Mo 和 Ni-Mo 加氢脱硫催化剂 总被引:4,自引:0,他引:4
自制介孔碳 (CMC) 具有比传统活性碳 (AC) 更大的比表面积、孔径和孔体积, 以其为载体, 在浸渍液中加入螯合剂, 采用等量浸渍法制备了 Co-Mo/CMC 和 Ni-Mo/CMC 催化剂, 分别用于模型汽油和柴油加氢脱硫反应. 结果表明, Co-Mo/CMC 和 Ni-Mo/CMC 催化剂具有比 Co-Mo/AC 催化剂更好的织构性质和加氢脱硫活性. 在模型汽油的加氢脱硫反应中, Co-Mo/CMC 催化剂活性比工业催化剂 Co-Mo/Al2O3 高得多; 而在模型柴油的加氢脱硫反应中, Ni-Mo/CMC 催化剂活性也比工业催化剂 FH-98 高得多. 相似文献
156.
以间苯二酚和甲醛为炭源, F127 (EO106PO70EO106) 为结构导向剂, 在酸性水/乙醇溶液中引入 (NH4)6Mo7O24•4H2O 或 (NH4)2WO4 溶液, 经静置自组装形成凝胶, 再于 N2 中焙烧即合成出金属碳化物修饰的有序介孔炭材料. 结果表明, 金属离子的种类和用量对碳化物的分散度和介孔炭的有序度影响很大. 通过控制金属离子的用量可制备出粒径为 3~5 nm 且高度分散在介孔炭骨架中的碳化物粒子. 与分步浸渍法相比, 一步法制备的碳化物具有更高的分散度和催化肼分解活性. 相似文献
157.
Yatsimirsky V. K. Boldyreva N. A. Lisnyak V. V. Slobodyanik N. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(2):551-554
The thermal stability of sample Mo(PO3)3 that is the initial material for novel catalysts for carbonmonoxide oxidation has been studied. It has been concluded that
molybdenum(III) methaphosphate is stable up to 435°C. Processes of partial oxidation and layering of specimens are determined.
Novel material based on partial oxidized Mo(PO3)3 gives significant rise of the carbon oxidation rate. The molybdenum(III) metaphosphate is of a definite interest in view
of its application in practice as initial material for new catalysts row formation with different content of Mo(PO3)3 and MoOPO4 layers.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
158.
159.
ZHANG Feng zhang ** XU Liang shu HUANG He qing LONG Min nan QIU Xue hui CHEN Zhong 《高等学校化学研究》1999,(3)
IntroductionNitrogenasefromavarietyofN2-fixingorganismsiscomposedoftwo-componentprotein,MoFe-proteinandFe-protein.Fe-proteincontainsasingleFe4S4-cluster,whichhasthefunctionoftransferingelectronsfromdonortoMoFe-protein.MoFe-proteincontainsP-clusterpai… 相似文献
160.