全文获取类型
收费全文 | 1369860篇 |
免费 | 26494篇 |
国内免费 | 8512篇 |
专业分类
化学 | 689744篇 |
晶体学 | 20336篇 |
力学 | 75122篇 |
综合类 | 163篇 |
数学 | 242682篇 |
物理学 | 376819篇 |
出版年
2021年 | 13616篇 |
2020年 | 16033篇 |
2019年 | 16144篇 |
2018年 | 12554篇 |
2016年 | 28026篇 |
2015年 | 20928篇 |
2014年 | 30648篇 |
2013年 | 74728篇 |
2012年 | 39950篇 |
2011年 | 37600篇 |
2010年 | 37841篇 |
2009年 | 40013篇 |
2008年 | 36634篇 |
2007年 | 32444篇 |
2006年 | 38525篇 |
2005年 | 30965篇 |
2004年 | 31731篇 |
2003年 | 29590篇 |
2002年 | 30569篇 |
2001年 | 30120篇 |
2000年 | 25932篇 |
1999年 | 23021篇 |
1998年 | 21227篇 |
1997年 | 21177篇 |
1996年 | 21218篇 |
1995年 | 19261篇 |
1994年 | 18704篇 |
1993年 | 18272篇 |
1992年 | 18342篇 |
1991年 | 18584篇 |
1990年 | 17745篇 |
1989年 | 17807篇 |
1988年 | 17328篇 |
1987年 | 17291篇 |
1986年 | 16310篇 |
1985年 | 22684篇 |
1984年 | 23886篇 |
1983年 | 20038篇 |
1982年 | 21709篇 |
1981年 | 20912篇 |
1980年 | 20273篇 |
1979年 | 20453篇 |
1978年 | 21786篇 |
1977年 | 21383篇 |
1976年 | 21144篇 |
1975年 | 19821篇 |
1974年 | 19489篇 |
1973年 | 19995篇 |
1972年 | 14496篇 |
1967年 | 12643篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
172.
173.
174.
175.
Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. 相似文献
176.
177.
178.
Dr. Wan‐Ling Liu Ni‐Shin Yang Ya‐Ting Chen Stephen Lirio Cheng‐You Wu Prof. Chia‐Her Lin Prof. Hsi‐Ya Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):115-119
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors. 相似文献
179.
Lithium Insertion Mechanism in Iron-Based Oxyfluorides with Anionic Vacancies Probed by PDF Analysis
Dr. Damien Dambournet Dr. Karena W Chapman Dr. Mathieu Duttine Dr. Olaf Borkiewicz Dr. Peter J Chupas Dr. Henri Groult 《ChemistryOpen》2015,4(4):443-447
The mechanism of lithium insertion that occurs in an iron oxyfluoride sample with a hexagonal–tungsten–bronze (HTB)-type structure was investigated by the pair distribution function. This study reveals that upon lithiation, the HTB framework collapses to yield disordered rutile and rock salt phases followed by a conversion reaction of the fluoride phase toward lithium fluoride and nanometer-sized metallic iron. The occurrence of anionic vacancies in the pristine framework was shown to strongly impact the electrochemical activity, that is, the reversible capacity scales with the content of anionic vacancies. Similar to FeOF-type electrodes, upon de-lithiation, a disordered rutile phase forms, showing that the anionic chemistry dictates the atomic arrangement of the re-oxidized phase. Finally, it was shown that the nanoscaling and structural rearrangement induced by the conversion reaction allow the in situ formation of new electrode materials with enhanced electrochemical properties. 相似文献
180.
Gustavo A.Carri 《高分子科学》2015,33(4):523-539
We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental T g’s for cis poly(1,4-butadiene) and found an excellent quantitative agreement. 相似文献