全文获取类型
收费全文 | 9988篇 |
免费 | 1441篇 |
国内免费 | 680篇 |
专业分类
化学 | 6906篇 |
晶体学 | 95篇 |
力学 | 526篇 |
综合类 | 36篇 |
数学 | 1295篇 |
物理学 | 3251篇 |
出版年
2023年 | 176篇 |
2022年 | 200篇 |
2021年 | 287篇 |
2020年 | 406篇 |
2019年 | 348篇 |
2018年 | 304篇 |
2017年 | 298篇 |
2016年 | 495篇 |
2015年 | 476篇 |
2014年 | 532篇 |
2013年 | 698篇 |
2012年 | 902篇 |
2011年 | 909篇 |
2010年 | 626篇 |
2009年 | 569篇 |
2008年 | 669篇 |
2007年 | 525篇 |
2006年 | 560篇 |
2005年 | 412篇 |
2004年 | 338篇 |
2003年 | 266篇 |
2002年 | 218篇 |
2001年 | 158篇 |
2000年 | 161篇 |
1999年 | 196篇 |
1998年 | 164篇 |
1997年 | 136篇 |
1996年 | 149篇 |
1995年 | 114篇 |
1994年 | 100篇 |
1993年 | 90篇 |
1992年 | 86篇 |
1991年 | 81篇 |
1990年 | 51篇 |
1989年 | 43篇 |
1988年 | 42篇 |
1987年 | 42篇 |
1986年 | 32篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 28篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1970年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
31.
用XRD、IR和TPR等技术研究了钙钛矿型复合氧化物的晶体结构及其反应性能.整个组成范围内,LaNi_(i-x)Mn_xO_3(0.0≤x≤1.0)体系都生成单一钙钛矿相;x=0.0,0.6≤X≤1.0时为菱形晶系,0.2≤x≤0.5为立方晶系.IR和TPR研究表明,晶体结构对B—O键合作用存在较大影响.CO微反考察表明,本体系的催化活性与晶系存在密切关系,晶体对称性越高,反应活性越低.说明钙钛矿型复合氧化物的催化活性与体系活性中心的B—O键合作用能力有关. 相似文献
32.
33.
34.
Wang Dunhui Huang Songling Han Zhida Su Zhenghua Wang Yi Du Youwei 《Solid State Communications》2004,131(2):97-99
A series of Gd(1−x)Bx alloys have been prepared by arc melting method. After introducing small quantity of B atom in Gd, the Curie temperature of these alloys increase while the magnetic entropy changes are almost same as that of Gd. The refrigerant capacities of these alloys are also greater than that of Gd. These results suggest that Gd(1−x)Bx alloys may be utilized as refrigerant in household magnetic refrigeration. 相似文献
35.
Dextran-modified iron oxide nanoparticles 总被引:1,自引:0,他引:1
Dextran-modified iron oxide nanoparticles were prepared by precipitation of Fe(Ⅱ) and Fe(Ⅲ) salts with ammonium hydroxide by two methods. Iron oxide was precipitated either in the presence of dextran solution, or the dextran solution was added after precipitation. In the second method, the iron oxide particle size and size distribution could be controlled depending on the concentration of dextran in the solution. The nanoparticles were characterized by size-exclusion chromatography, transmission electron microscopy and dynamic light scattering. Optimal conditions for preparation of stable iron oxide colloid particles were determined, The dextran/iron oxide ratio 0-0,16 used in precipitation of iron salts can be recommended for synthesis of nanoparticles suitable for biomedical applications, as the colloid does not contain excess dextran and does not coagulate. 相似文献
36.
37.
Dingzhu Du 《应用数学学报(英文版)》1989,5(4):355-360
Lower bounds for Byzantine agreement obtained by Dolev and Strong are shown, by a simpler method, also to be true for weak Byzantine agreement.This work was done while the author was studying at University of California, Santa Barbara, in 1984. 相似文献
38.
Improving Construction for Connected Dominating Set with Steiner Tree in Wireless Sensor Networks 总被引:2,自引:0,他引:2
Manki Min Hongwei Du Xiaohua Jia Christina Xiao Huang Scott C.-H. Huang Weili Wu 《Journal of Global Optimization》2006,35(1):111-119
The connected dominating set plays an important role in ad hoc wireless networking. Many constructions for approximating the minimum connected dominating set have been proposed in the
literature. In this paper, we propose a new one with Steiner tree, which produces approximation solution within a factor of
6.8 from optimal. This approximation algorithm can also be implemented distributedly. 相似文献
39.
40.
Precise measurement of magnetic moment of short-lived β-emitting nuclei12B ( I π=1+, T 1/2=20.18 ms)
Zhou Dongmei Zheng Yongnan Du Enpeng Xu Yongjun Zhu Jiazheng Yuan Daqing Wang Zhiqiang Luo Hailong Zuo Yi Ma Ruigang Duan Xiao M. Mihara M. Fukuda K. Matsuta T. Minamisono Zhu Shengyun 《中国科学G辑(英文版)》2004,47(5):531-539
The spin polarized β-emitting nuclei12B (I
π=1+,T
1/2=20.18 ms) were produced by the nuclear reaction11B(d, p)12B and by the selection technique of the incident deuteron energy and the12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment
of12B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift. 相似文献