全文获取类型
收费全文 | 1925篇 |
免费 | 81篇 |
国内免费 | 16篇 |
专业分类
化学 | 1360篇 |
晶体学 | 16篇 |
力学 | 42篇 |
数学 | 344篇 |
物理学 | 260篇 |
出版年
2023年 | 17篇 |
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 33篇 |
2019年 | 32篇 |
2018年 | 31篇 |
2017年 | 30篇 |
2016年 | 61篇 |
2015年 | 56篇 |
2014年 | 52篇 |
2013年 | 117篇 |
2012年 | 130篇 |
2011年 | 125篇 |
2010年 | 66篇 |
2009年 | 76篇 |
2008年 | 127篇 |
2007年 | 146篇 |
2006年 | 141篇 |
2005年 | 102篇 |
2004年 | 94篇 |
2003年 | 67篇 |
2002年 | 80篇 |
2001年 | 45篇 |
2000年 | 48篇 |
1999年 | 27篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 32篇 |
1995年 | 20篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 5篇 |
1962年 | 3篇 |
排序方式: 共有2022条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
J. L. Jiménez Pérez E. Rangel Vargas R. Gutiérrez Fuentes A. Cruz-Orea H. Bautista de León 《The European physical journal. Special topics》2008,153(1):511-513
In this paper we used thermal lens spectrometry to
determine the thermal diffusivity of cheese fats. We have used equal
concentrations of cheese fats from oaxaca, chihuahua, gouda, manchego and
mozzarella cheeses at 42°C temperature. The two lasers
mismatched mode experimental configuration was used with a He-Ne laser, as a
probe beam and an Ar+ laser as the excitation one. The characteristic
time constant of the transient thermal lens was obtained by fitting the
theoretical expression to the experimental data in order to obtain the
thermal diffusivity of the cheese fat samples. This measured thermal
property may contribute to a better understanding of the cheese fats
quality, which is very important in food industry. 相似文献
95.
96.
Reyes-Chilpa R Jiménez-Estrada M Godínez MV Hernández-Ortega S Campos M Béjar E 《Natural product letters》2002,16(4):239-242
A new cacalolide sesquiterpenoid, named as Romo-A, was isolated from the roots of Psacalium decompositum, Asteraceae, a Mexican medicinal shrub with antidiabetic properties. Its structure was elucidated by NMR, MS, IR, UV, and confirmed by X-ray diffraction studies. 相似文献
97.
Avalos M Babiano R Cintas P Clemente FR Gordillo R Hursthouse MB Jiménez JL Light ME Palacios JC 《The Journal of organic chemistry》2002,67(7):2378-2381
The present contribution discloses a simple and unexpected acid-catalyzed cleavage of tetrahydrotetrazines leading to 1,2-bis(hydrazones). Incorporation of a chiral fragment derived from carbohydrates enables the rapid preparation of glycosazones, a family of compounds employed by Emil Fischer to elucidate the configuration of sugars. In addition, a mechanistic proposal accounts for experimental observations. 相似文献
98.
Delgado J Espinós A Jiménez MC Miranda MA 《Chemical communications (Cambridge, England)》2002,(22):2636-2637
Formation of an o-quinone methide via C-C fragmentation of a zwitterion formed by intramolecular excited state proton transfer from an o-allylphenol derivative is reported for the first time. 相似文献
99.
García-Herrero A Montero E Muñoz JL Espinosa JF Vián A García JL Asensio JL Cañada FJ Jiménez-Barbero J 《Journal of the American Chemical Society》2002,124(17):4804-4810
We show that the conformational features of the molecular complexes of E. coli beta-galactosidase and O-glycosides may differ from those formed with closely related compounds in their chemical nature, such as C- and S-glycosyl analogues. In the particular case presented here, NMR and ab initio quantum mechanical results show that the 3D-shapes of the ligand/inhibitor within the enzyme binding site depend on the chemical nature of the compounds. In fact, they depend on the relative size of the stereoelectronic barriers for chair deformation or for rotation around Phi glycosidic linkage. 相似文献
100.
Asensio JL Cañada FJ Cheng X Khan N Mootoo DR Jiménez-Barbero J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(6):1035-1041
The conformational behavior of alpha-O-Man-(1-->1)-beta-Gal (1) and its C-analogue (2) has been studied using J/NOE NMR data, molecular mechanics, molecular dynamics, and ab initio calculations. The population distribution around the glycosidic linkages of 1 and 2 is rather different, especially for the alpha-Man linkage. A lower limit for the exo-anomeric effect in water has been experimentally determined. 相似文献