全文获取类型
收费全文 | 4461篇 |
免费 | 736篇 |
国内免费 | 417篇 |
专业分类
化学 | 2933篇 |
晶体学 | 57篇 |
力学 | 378篇 |
综合类 | 30篇 |
数学 | 532篇 |
物理学 | 1684篇 |
出版年
2024年 | 5篇 |
2023年 | 125篇 |
2022年 | 100篇 |
2021年 | 184篇 |
2020年 | 194篇 |
2019年 | 194篇 |
2018年 | 173篇 |
2017年 | 131篇 |
2016年 | 227篇 |
2015年 | 215篇 |
2014年 | 247篇 |
2013年 | 319篇 |
2012年 | 411篇 |
2011年 | 410篇 |
2010年 | 286篇 |
2009年 | 252篇 |
2008年 | 271篇 |
2007年 | 250篇 |
2006年 | 249篇 |
2005年 | 205篇 |
2004年 | 152篇 |
2003年 | 121篇 |
2002年 | 93篇 |
2001年 | 77篇 |
2000年 | 98篇 |
1999年 | 85篇 |
1998年 | 74篇 |
1997年 | 70篇 |
1996年 | 69篇 |
1995年 | 65篇 |
1994年 | 33篇 |
1993年 | 44篇 |
1992年 | 44篇 |
1991年 | 30篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有5614条查询结果,搜索用时 140 毫秒
31.
32.
33.
Huo-yuan Duan Qun Lin 《计算数学(英文版)》2006,24(2):157-168
This paper provides a proof for the uniform convergence rate (independently of the number of mesh levels) for the nonnested V-cycle multigrid method for nonsymmetric and indefinite second-order elliptic problems. 相似文献
34.
35.
36.
毛细管电色谱研究进展 总被引:7,自引:2,他引:7
毛细管电色谱是一种新兴的具有高效,高选择性的微分离技术。本文评述了毛细管电色说的发展状况和相关的技术,并对其发展前景进行了展望,引用文献24篇 。 相似文献
37.
Iron speciation related to color of Jurassic sedimentary rocks in Turpan Basin, northwest China 总被引:1,自引:0,他引:1
Guodong Zheng Bihong Fu Yi Duan Qi Wang M. Matsuo B. Takano 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):421-427
Mesozoic-Cenozoic reddish and green beds are widely distributed in northwest China. Mössbauer spectroscopy revealed that the composition of iron species varies with color in the middle-upper Jurassic sedimentary rocks from the Turpan Basin. Three main kinds of iron species were identified: (1) ferric iron of hematite (hem-Fe3+), (2) paramagnetic ferric iron (para-Fe3+), and (3) paramagnetic ferrous iron (para-Fe2+). Pyrite iron (pyr-Fe2+) was revealed only in a few samples. In general, there is a direct correlation between rock color, iron species and total iron content, however, in detail, this relationship is more complicated. The reddish rocks contain higher contents of total iron and hem-Fe3+, whereas the gray rocks contain much more para-Fe2+. However, relatively low hematite content cannot give red color to rocks, probably due to suppression by other pigments such as organic matter in black or chlorite in green. The dark or green rocks normally contain either only paramagnetic Fe2+ and paramagnetic Fe3+ species or these two species associated with hematite Fe3+, but the relative content of hematite species is lower. The variations of different iron species control lithological properties such as color and also may reflect the sedimentary conditions. Moreover, iron speciation in these rocks is one of the main factors, which result the color features of rocks in remote sensing imagery.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
38.
Zhu Hai-Liang Huang Pei Duan Chun-Ying Zheng Li-Min Liu Yong-Jiang Wu Mei-Fang Tang Wen-Xia 《Transition Metal Chemistry》1999,24(4):380-383
An azide-bridged polymeric cationic chain complex, [LCu2(N3)2]n(ClO4)2n
·n(H2O)**, where L=the dinucleating macrocyclic ligand bis-p-xylylBISDIEN, has been prepared and characterized by x-ray crystallography, u.v.-vis and i.r. spectra, and by magnetic measurements. The structure consists of cationic azide-bridged [LCu2(N3)2]2+ (unit) chains, non-coordinated perchlorate anions and crystallized water molecules. The azide anion is bound to two copper atoms in neighboring units with an end-to-end bridging mode. In each unit, the copper atoms have a different coordination geometry; Cu(1) is a four-coordinated, distorted square-planar geometry, whereas Cu(2) is a five-coordinated, distorted square-pyramid. The electronic spectra of the title complex differ in anhydrous and in aqueous MeCN solutions, indicating that dissociation and solvation occur in aqueous solutions. The characteristic i.r. absorptions of azides and perchlorates are described. Magnetic moments vary from 2.05 (B.M.) at 300K to2.01 (B.M.) at 80K, which suggests that very weak interactions exist between the metals. 相似文献
39.
40.
微波场中甲烷部分氧化制合成气 Ⅱ.Co/ZrO_2催化剂在微波场中的升温行为及催化活性 总被引:4,自引:0,他引:4
近年来,甲烷部分氧化制合成气(POM)的研究一直十分活跃[1,2].前文报道了用于甲烷部分氧化制合成气的镍基催化剂(Ni/La2O3)在微波场中的升温行为和催化活性[3],发现在达到相同的CH4转化率时,微波活化方式下的催化剂床层温度比常规加热低得多... 相似文献