全文获取类型
收费全文 | 14585篇 |
免费 | 1303篇 |
国内免费 | 1707篇 |
专业分类
化学 | 8439篇 |
晶体学 | 154篇 |
力学 | 1740篇 |
综合类 | 55篇 |
数学 | 811篇 |
物理学 | 6396篇 |
出版年
2024年 | 28篇 |
2023年 | 178篇 |
2022年 | 347篇 |
2021年 | 357篇 |
2020年 | 410篇 |
2019年 | 352篇 |
2018年 | 314篇 |
2017年 | 416篇 |
2016年 | 583篇 |
2015年 | 516篇 |
2014年 | 732篇 |
2013年 | 917篇 |
2012年 | 749篇 |
2011年 | 1114篇 |
2010年 | 903篇 |
2009年 | 1129篇 |
2008年 | 933篇 |
2007年 | 1192篇 |
2006年 | 1044篇 |
2005年 | 713篇 |
2004年 | 710篇 |
2003年 | 628篇 |
2002年 | 389篇 |
2001年 | 389篇 |
2000年 | 311篇 |
1999年 | 298篇 |
1998年 | 265篇 |
1997年 | 256篇 |
1996年 | 263篇 |
1995年 | 182篇 |
1994年 | 136篇 |
1993年 | 126篇 |
1992年 | 113篇 |
1991年 | 96篇 |
1990年 | 85篇 |
1989年 | 62篇 |
1988年 | 60篇 |
1987年 | 49篇 |
1986年 | 38篇 |
1985年 | 39篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1973年 | 9篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
消荧光现象是激光与物质表面非线性相互作用的结果,这是一种普遍现象。在表面谐波产生的研究中,它常常被忽略。大量研究表明:表面谐波产生与消荧光现象,有着密切的内在联系。本文以消荧光观点详细讨论了表面谐波产生的机制,提出了表面谐波产生的消荧光模型。新机制可归纳为:(a)多光子受激吸收产生消荧光光斑,(b)激光热效应等促进自发辐射转向准受激辐射,(c)伴随荧光消失,部分产生荧光的激光能量转换为产生表面谐波 相似文献
42.
首次用三道光纤探测器,伸入HL-1装置内真空室,采集活动石墨孔栏处等离子体光信号,用22m石英长光纤传输光信号至控制室进行观测。通过边界等离子体H_α和杂质辐射的时空分布,初步探讨了HL-1装置的脱离等离子体。 相似文献
43.
Analysis of the generation mechanism of the S-shaped J—V curves of MoS2/Si-based solar cells 下载免费PDF全文
Amorphous-microcrystalline MoS$_{2}$ thin films are fabricated using the sol-gel method to produce MoS$_{2}$/Si-based solar cells. The generation mechanisms of the S-shaped current density-voltage ($J$-$V$) curves of the solar cells are analyzed. To improve the performance of the solar cells and address the problem of the S-shaped $J$-$V$ curve, a MoS$_{2}$ film and a p$^+$ layer are introduced into the front and back interfaces of the solar cell, respectively, which leads to the formation of a p-n junction between the p-Si and the MoS$_{2}$ film as well as ohmic contacts between the MoS$_{2}$ film and the ITO, improving the S-shaped $J$-$V$ curve. As a result of the high doping characteristics and the high work function of the p$^+$ layer, a high-low junction is formed between the p$^+$ and p layers along with ohmic contacts between the p$^+$ layer and the Ag electrode. Consequently, the S-shaped $J$-$V$ curve is eliminated, and a significantly higher current density is achieved at a high voltage. The device exhibits ideal p-n junction rectification characteristics and achieves a high power-conversion efficiency (CE) of 7.55%. The findings of this study may improve the application of MoS$_{2}$ thin films in silicon-based solar cells, which are expected to be widely used in various silicon-based electronic and optical devices. 相似文献
44.
45.
46.
In studies of metabolism using serum albumin labelled with iodine (I131 and I125) the question of the biological equivalence of the labelled material is of decisive importance. Changes of the chemical and biological characteristic of various proteins after iodination have been found by a number of workers [1–4], especially with reference to chromatographic behaviour, rate of metabolism in the organism and content of thiol. Oxidation of sulphhydryl groups can lead to interchain disulphide bridge-linkage and the formation of molecule aggregates. 相似文献
47.
《Physics and Chemistry of Liquids》2012,50(5):579-584
Surface tension (γ) and viscosity (η) data of aqueous solutions of the deoxyadenosine (DOA) and the deoxyribose (DOR) sugars have been measured with the survismeter, a new instrument, along with tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile and dimethylsulphoxide (DMSO) solvents. The same properties have also been measured with a stalagmometer and a viscosimeter, respectively, which afford the same information, albeit at the expense of a larger amount of chemicals and solvents. We obtain comparatively better accuracy in both kinds of measurements than with conventional methods. Therefore, the survismeter lends itself as a simple and reliable instrument. 相似文献
48.
49.
50.
Swagata Chakraborty Susmitha A. L. Ramakrishna V. Hosur 《Magnetic resonance in chemistry : MRC》2012,50(9):587-591
Direct detection of 13C nucleus can be used as a valuable alternative where 1H detection poses a challenge due to relaxation effects, chemical exchange and poor chemical shift dispersion. In this context, we have designed a suite of 2D 13Cα‐detected hNCA experiments that provide sequential correlations of 13Cα with 15N on one hand and efficient spectroscopic labeling of certain groups of residues, namely, Gly, Ala, Ser and Thr, on the other. These residues act as checkpoints in the sequential walk, which in turn offer new possibilities of backbone assignment of small proteins from a set of 2D experiments, thereby providing great economy in terms of spectrometer time. The direct identification of peptide segments around Gly, Ala, Ser and Thr residues along a protein chain will be highly valuable for deriving important information on sites of ligand binding, phosphorylation, inhibitor/substrate binding, understanding protein folding pathways, comprehending local conformational dynamics etc. without having to obtain complete sequence‐specific assignments, which can be time consuming and at times formidable, especially in large proteins. We have illustratively demonstrated the multifaceted applications of these variants of 2D experiments on ubiquitin and M‐crystallin. We foresee that these 2D hNCA experiments will provide economic and efficient strategies for studying the structure and function of proteins. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献