全文获取类型
收费全文 | 5068篇 |
免费 | 722篇 |
国内免费 | 711篇 |
专业分类
化学 | 3897篇 |
晶体学 | 56篇 |
力学 | 268篇 |
综合类 | 67篇 |
数学 | 720篇 |
物理学 | 1493篇 |
出版年
2024年 | 11篇 |
2023年 | 88篇 |
2022年 | 146篇 |
2021年 | 172篇 |
2020年 | 200篇 |
2019年 | 209篇 |
2018年 | 202篇 |
2017年 | 160篇 |
2016年 | 220篇 |
2015年 | 234篇 |
2014年 | 263篇 |
2013年 | 348篇 |
2012年 | 416篇 |
2011年 | 460篇 |
2010年 | 304篇 |
2009年 | 291篇 |
2008年 | 355篇 |
2007年 | 250篇 |
2006年 | 253篇 |
2005年 | 232篇 |
2004年 | 192篇 |
2003年 | 187篇 |
2002年 | 205篇 |
2001年 | 170篇 |
2000年 | 134篇 |
1999年 | 110篇 |
1998年 | 104篇 |
1997年 | 69篇 |
1996年 | 111篇 |
1995年 | 81篇 |
1994年 | 60篇 |
1993年 | 40篇 |
1992年 | 37篇 |
1991年 | 34篇 |
1990年 | 38篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有6501条查询结果,搜索用时 171 毫秒
21.
In this paper classical approaches are used to study the detailed processes of photoion-ization in an intense laser field. The analytic expression of the ionization rate is derived. Finally, the results obtained are compared with existing theories such as Landau's tunnel theory and Keldysh-Faisal-Reiss theory. 相似文献
22.
为了探索低温可调控ZnO薄膜沉积技术,提出了一种新的ZnO薄膜制备方法,即离化团簇束(ICB)法,并自行设计研制了应用该方法制备ZnO薄膜的专门装置.采用超音速喷嘴获得高速锌原子团簇束,用Hall等离子体源产生氧离子束离化锌原子团簇,获得了较高的离化率.在沉积过程中,可以通过调节衬底偏压、氩氧比、衬底加热温度等参数,来控制成膜的质量;应用这个装置成功地在硅衬底上制备的ZnO薄膜,经XRD和EDS检测,薄膜的c轴取向一致,Zn、O原子百分比接近于1:1,成膜质量好. 相似文献
23.
In this paper we investigate the acute triangulations of flat Mobius strips. We find out that we can always triangulate a
flat Mobius strip with at most nine acute triangles, and sometimes (but not always) that many triangles are really needed. 相似文献
24.
25.
The feature selection consists of obtaining a subset of these features to optimally realize the task without the irrelevant
ones. Since it can provide faster and cost-effective learning machines and also improve the prediction performance of the
predictors, it is a crucial step in machine learning. The feature selection methods using support machines have obtained satisfactory
results, but the noises and outliers often reduce the performance. In this paper, we propose a feature selection approach
using fuzzy support vector machines and compare it with the previous work, the results of experiments on the UCI data sets
show that feature selection using fuzzy SVM obtains better results than using SVM. 相似文献
26.
Tian Le LIN Bao Zhen YAN Gao Fei HU Mei WANG 《中国化学快报》2006,17(7):937-940
Complex formation between aluminium and quercetin(Q) in methanol was investigated by means of 27^Al solid-state, 13^C and 1^H NMR and MS(ESI), UV and IR spectra. Formation of the 1:2 complex was favored in methanol relative to all other solvent and the predominant species observed of Al(Ⅲ) has a 1:2 stoichiometry. The fine structure of 1:2 aluminum complex of quercetin was that the aluminum central atom chelated with two quereetin molecules and two methoxyl groups between two five membered rings, its coordination is six, the chelated site was 3-hydroxy-4-carbonyl. 相似文献
27.
Jun Hua YU Xue Song WANG Bao Wen ZHANG* Yi CAO Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(10)
Porphyrin derivatives attract much more interest in photodynamic therapy (PDT). Their importance as therapeutic drugs and targeting agents has been widely recognized1, and many of the efforts have been put towards crafting new porphyrin-based molecular entities to achieve enhanced tumor localization, better tissue penetration and increased singlet oxygen quantum yield2. The states of porphyrins in tissue models such as micelles, lipid bilayers are extensively investigated focusing more or l… 相似文献
28.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
29.
30.
TheImprovementofFischer'sInequalityandHadamard'sInequalityHuangLiping(黄礼平)(DepartmentofBasicSciences,XiangtanMiningInstitute,... 相似文献