全文获取类型
收费全文 | 1835篇 |
免费 | 66篇 |
国内免费 | 11篇 |
专业分类
化学 | 1433篇 |
晶体学 | 26篇 |
力学 | 61篇 |
数学 | 114篇 |
物理学 | 278篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 34篇 |
2021年 | 51篇 |
2020年 | 39篇 |
2019年 | 47篇 |
2018年 | 45篇 |
2017年 | 44篇 |
2016年 | 83篇 |
2015年 | 65篇 |
2014年 | 112篇 |
2013年 | 159篇 |
2012年 | 139篇 |
2011年 | 158篇 |
2010年 | 86篇 |
2009年 | 62篇 |
2008年 | 109篇 |
2007年 | 114篇 |
2006年 | 92篇 |
2005年 | 91篇 |
2004年 | 53篇 |
2003年 | 48篇 |
2002年 | 45篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1969年 | 2篇 |
1964年 | 5篇 |
排序方式: 共有1912条查询结果,搜索用时 15 毫秒
1.
Structural Chemistry - The hydrogen bond interactions between methyl-imidazolium cation (MIM+) and fatty acid anions (CmHnCOO–, where m?=?1–6; n-3–13) of ionic liquids... 相似文献
2.
S. Venkatesan S. Suresh P. Ramu M. Kandasamy J. Arumugam S. Thambidurai K.M. Prabu N. Pugazhenthiran 《印度化学会志》2022,99(5):100436
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications. 相似文献
3.
4.
Nano palladium supported on high‐surface‐area metal–organic framework MIL‐101: an efficient catalyst for Sonogashira coupling of aryl and heteroaryl bromides with alkynes
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Manne Annapurna T. Parsharamulu P. Vishnuvardhan Reddy M. Suresh Pravin R. Likhar Mannepalli Lakshmi Kantam 《应用有机金属化学》2015,29(4):234-239
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
The stereoselective intramolecular cyclizations of bis(cinnamyl)tosylamides and dimethyl bis(cinnamyl)malonates mediated by cerium(IV) ammonium nitrate leading to the synthesis of 3,4-trans-disubstituted pyrrolidines and cyclopentanes are described. 相似文献
6.
M. Suresh Babu 《Tetrahedron letters》2004,45(42):7969-7970
Reduction of 2-aryl-oxazolines with NiCl2/NaBH4 followed by hydrolysis gives the corresponding aldehydes in good yields. 相似文献
7.
Numerical simulation aspects, related to low Reynolds number free boundary viscous flows at micro and mesolevel during the resin impregnation stage of the liquid composite moulding process (LCM), are presented in this article. A free boundary program (FBP), developed by the authors, is used to track the movement of the resin front accurately by accounting for the surface tension effects at the boundary. Issues related to the global and local mass conservation (GMC and LMC) are identified and discussed. Unsuitable conditions for LMC and consequently GMC are uncovered at low capillary numbers, and hence a strategy for the numerical simulation of such flows is suggested. FBP encompasses a set of subroutines that are linked to modules in ANSYS. FBP can capture the void formation dynamics based on the analysis developed. We present resin impregnation dynamics in two dimensions. Extension to three dimensions is a subject for further research. Several examples are shown and efficiency of different stabilization techniques are compared. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
8.
Suresh K Kumar Prabhakara S Rao L Krishnaiah B Jayaraj P Chiranjeevi 《Analytical sciences》2004,20(6):951-953
A simple and highly sensitive reagent of salicylaldehyde 3-oxobutanoylhydrazone (salicylaldehyde acetoacetic acid hydrazone, SAAH) was synthesized and studied for the spectrophotometric determination of nickel in detail. In the pH range 6, which greatly increased the selectivity, nickel reacted with SAAH to form a 1:1 yellow complex, having a sensitive absorption peak at 405 nm. Under the optimal conditions, Beer's law was obeyed over the range from 0.0117 to 0.1174 microg cm(-3). The apparent molar absorptivity was 3.025 x 10(5) dm3 mol(-1) cm(-1). The detection limit and the variation coefficient were found to be 1.752 ng cm(-3) and 1.0%, respectively. The method has been applied to the quantitative determination of nickel in different alloys and leaves. 相似文献
9.
10.
A 6.71 kW power tiller was evaluated for draft and drawbar power on tar roads. The effect of mounting 40 kg of wheel ballast was also studied. Polynomial regression analysis was used to establish the relationship between draft and wheel slip, drawbar power and wheel slip, drawbar power and fuel consumption, and drawbar power and specific fuel consumption. The results of the study showed draft values of 2107, 2110 and 2110 N in second low, third low and first high gears at an engine speed of 150o rpm with a 15% wheel slip. The respective draft values at engine speed of 2000 rpm with a 15% wheel slip were 2172, 2189 and 2212 N. With the mounting of 40kg wheel ballast there was an increase in draft of 217, 207 and 291 N at 1500 rpm, and 328, 306 and 344 N at 2000 rpm of the engine with a 15% wheel slip in second low, third low and first high gears, respectively. The increase in drawbar power with 40 kg ballast was 10.88%, 7.83% and 20.13% at 1500 rpm and 18.89%, 16.56% and 14.88% at 2000 rpm of engine over the drawbar power available with zero ballast. The fuel consumption with the use of wheel ballast was slightly more than the fuel consumption without any ballast. 相似文献