全文获取类型
收费全文 | 174006篇 |
免费 | 2409篇 |
国内免费 | 729篇 |
专业分类
化学 | 93929篇 |
晶体学 | 2516篇 |
力学 | 7699篇 |
综合类 | 7篇 |
数学 | 18111篇 |
物理学 | 54882篇 |
出版年
2021年 | 1049篇 |
2020年 | 1172篇 |
2019年 | 1203篇 |
2018年 | 1238篇 |
2017年 | 1251篇 |
2016年 | 2455篇 |
2015年 | 1999篇 |
2014年 | 2657篇 |
2013年 | 7955篇 |
2012年 | 6476篇 |
2011年 | 8187篇 |
2010年 | 5044篇 |
2009年 | 5153篇 |
2008年 | 7487篇 |
2007年 | 7446篇 |
2006年 | 7132篇 |
2005年 | 6659篇 |
2004年 | 5936篇 |
2003年 | 5121篇 |
2002年 | 5026篇 |
2001年 | 6055篇 |
2000年 | 4593篇 |
1999年 | 3500篇 |
1998年 | 2655篇 |
1997年 | 2642篇 |
1996年 | 2598篇 |
1995年 | 2304篇 |
1994年 | 2187篇 |
1993年 | 2060篇 |
1992年 | 2375篇 |
1991年 | 2323篇 |
1990年 | 2041篇 |
1989年 | 2030篇 |
1988年 | 2055篇 |
1987年 | 1983篇 |
1986年 | 1888篇 |
1985年 | 2803篇 |
1984年 | 2778篇 |
1983年 | 2222篇 |
1982年 | 2413篇 |
1981年 | 2308篇 |
1980年 | 2263篇 |
1979年 | 2199篇 |
1978年 | 2279篇 |
1977年 | 2236篇 |
1976年 | 2149篇 |
1975年 | 2140篇 |
1974年 | 2039篇 |
1973年 | 2129篇 |
1972年 | 1213篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
11.
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
12.
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
13.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing 下载免费PDF全文
14.
15.
16.
The European Physical Journal Special Topics - The removal of suspended particles from the interior of a thermocapillary liquid bridge via a finite-particle-size effect restricting the particle... 相似文献
17.
18.
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
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
19.
20.
An approach of dynamic mesh adaptation for simulating 3‐dimensional unsteady moving‐immersed‐boundary flows 下载免费PDF全文
In this paper, we present an approach of dynamic mesh adaptation for simulating complex 3‐dimensional incompressible moving‐boundary flows by immersed boundary methods. Tetrahedral meshes are adapted by a hierarchical refining/coarsening algorithm. Regular refinement is accomplished by dividing 1 tetrahedron into 8 subcells, and irregular refinement is only for eliminating the hanging points. Merging the 8 subcells obtained by regular refinement, the mesh is coarsened. With hierarchical refining/coarsening, mesh adaptivity can be achieved by adjusting the mesh only 1 time for each adaptation period. The level difference between 2 neighboring cells never exceeds 1, and the geometrical quality of mesh does not degrade as the level of adaptive mesh increases. A predictor‐corrector scheme is introduced to eliminate the phase lag between adapted mesh and unsteady solution. The error caused by each solution transferring from the old mesh to the new adapted one is small because most of the nodes on the 2 meshes are coincident. An immersed boundary method named local domain‐free discretization is employed to solve the flow equations. Several numerical experiments have been conducted for 3‐dimensional incompressible moving‐boundary flows. By using the present approach, the number of mesh nodes is reduced greatly while the accuracy of solution can be preserved. 相似文献