全文获取类型
收费全文 | 4330篇 |
免费 | 487篇 |
国内免费 | 584篇 |
专业分类
化学 | 3567篇 |
晶体学 | 40篇 |
力学 | 20篇 |
综合类 | 7篇 |
数学 | 44篇 |
物理学 | 1723篇 |
出版年
2024年 | 7篇 |
2023年 | 60篇 |
2022年 | 73篇 |
2021年 | 85篇 |
2020年 | 161篇 |
2019年 | 139篇 |
2018年 | 96篇 |
2017年 | 128篇 |
2016年 | 165篇 |
2015年 | 158篇 |
2014年 | 196篇 |
2013年 | 277篇 |
2012年 | 288篇 |
2011年 | 299篇 |
2010年 | 234篇 |
2009年 | 317篇 |
2008年 | 287篇 |
2007年 | 378篇 |
2006年 | 269篇 |
2005年 | 177篇 |
2004年 | 176篇 |
2003年 | 233篇 |
2002年 | 147篇 |
2001年 | 193篇 |
2000年 | 129篇 |
1999年 | 96篇 |
1998年 | 96篇 |
1997年 | 96篇 |
1996年 | 75篇 |
1995年 | 76篇 |
1994年 | 62篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 32篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有5401条查询结果,搜索用时 515 毫秒
1.
Pavitra Laohapaisan Kanyapat Lumyong Jumreang Tummatorn Charnsak Thongsornkleeb Jaruwan Chatwichien Nantamon Supantanapong Somsak Ruchirawat 《化学:亚洲杂志》2022,17(1):e202101212
ortho-Alkynylarylketone derivatives were employed as key precursors for a one-pot synthesis of arylnaphthalenelactone and furanonaphthol libraries. In this work, we discovered a cost-effective protocol to prepare arylnaphthalenelactones in one-pot using inexpensive starting material, malonate ester, which was conveniently functionalized leading to a variety of structures. Moreover, we also found an unexpected oxy-dearylation reaction which could be used to synthesize furanonaphthol analogs. These novel methods could be applied to a broad range of substrates to give the corresponding products in up to 83% yield. Notably, these classes of compounds exhibited more significant inhibition against protein-tyrosine phosphatase 1B (PTP1B) enzyme than a standard compound, ursolic acid. 相似文献
2.
3.
Today the synthesis of silver nanoparticles is very common due to their numerous applications in various fields. Silver nanoparticles have unique properties such as: optical and catalytic properties, which, depend on the size and shape of the produced nanoparticles. So, today the production of silver nanoparticles with different shapes which have various uses in different fields such as medicine, are noted by many researchers. This article, is an attempt to present an overview of the shape-controlled synthesis of silver nanoparticles using various methods. 相似文献
4.
Suman Gomosta Rongala Ramalakshmi Chinnappa Arivazhagan Anagha Haridas Beesam Raghavendra Kuppaiyandi Maheswari Thierry Roisnel Sundargopal Ghosh 《无机化学与普通化学杂志》2019,645(6-7):588-594
The complexes [Ag{κ3‐S,S′,H‐H2B(mbz)2}(PR3)]x, ( 1 : x = 2, R = Ph; 2 : x = 1, R = Cy) (mbz = 2‐mercaptobenzothiazolyl) and amidine based dihydro(2‐mercaptobenzo‐thiazolyl) borates, [HN=C(Ph)–NH(R)–H2B(mbz)] ( 3 : R = 2,6‐diisopropylphenyl and 4 : R = Ph) were synthesized and characterized by various spectroscopic methods and single‐crystal X‐ray crystallography. Complex [Ag{κ3‐S,S′,H‐H2B(mbz)2}(PPh3)]2 ( 1 ) has a dimeric structure in its crystalline state, in which central silver(I) atoms adopt a distorted trigonal bipyramid arrangement. In contrast, complex [Ag{κ3‐S,S′,H‐H2B(mbz)2}(PCy3)] ( 2 ) has a monomeric structure in its crystalline state, in which the central silver(I) atoms adopt a distorted trigonal planar arrangement. Infrared spectroscopy was utilized as a tool for investigating the presence of M ··· H–B interactions. In addition, density functional theory (DFT) calculations were used to analyse the B–H ··· [M] bonding interaction in the metal borate complexes. 相似文献
5.
Using 1,1,2‐triphenylethane‐1,2‐diol, AgSbF6, and NOSbF6, two different carbonyl products of rearrangement were synthesized: neutral ketone compound 1,2,2‐triphenylethanone ( 1 ) from NOSbF6 and coordination complex of Ag ion and aldehyde product ([Ag ·2 2]+SbF6–) from AgSbF6. Single crystal X‐ray analyses reveal the different structure generated by different salt. UV/Vis absorption spectra and calculation demonstrate the formation of both compounds. It provides an example of chemoselectivity of Wagner–Meerwein 1,2‐shifts in pinacol rearrangement that depends upon different oxidant. 相似文献
6.
7.
以脂质体作为模板, 通过化学还原法制备了脂质体@Ag/Au 中空纳米材料, 并研究了其与过氧化氢(H2O2)的作用. 利用透射电子显微镜(TEM)、 紫外-可见(UV-Vis)吸收光谱和表面增强拉曼光谱(SERS)对纳米材料进行了表征. 在过氧化氢和纳米材料存在的情况下, 加入3,3 ',5,5'-四甲基联苯胺(TMB)作为显色液, 无色的TMB被氧化成蓝色的氧化TMB(oxTMB), 可以检测到反应后oxTMB在652 nm处的特征吸收强度及其拉曼光谱的变化. 实验结果表明, 当过氧化氢浓度在15100 μmol/L 范围内, oxTMB的特征吸收强度与其浓度呈线性关系, 可实现对过氧化氢的微量检测, 检测限为0.5 μmol/L. 相似文献
8.
Li Li Liu Shi Xiaohu Yu Shaojun Qing Zhixian Gao Qiquan Luo Gang Feng Rongbin Zhang 《中国化学快报》2019,30(6):1147-1152
The adsorption energies for single Ni atom on CuAl2O4(100) and (110) surfaces are 5.30 and 4.08 eV, respectively. The growth and aggregation of Ni can be effectively inhibited on the perfect CuAl2O4(100) surface. The adsorption of Ni on the spinel surface is accompanied by charge transfer. The interaction of Ni with CuAl2O4 surface is stronger than with the γ-Al2O3(110) surface. 相似文献
9.
G. L. Gutsev K. V. Bozhenko L. G. Gutsev A. N. Utenyshev S. M. Aldoshin 《Journal of computational chemistry》2019,40(3):562-571
The geometrical structures and properties of the M8O12, M8O12H8, and M8O12H12 clusters are explored using density functional theory with the generalized gradient approximation for all 3d-metals M from Sc to Zn. It is found that the geometries and total spin magnetic moments of the clusters depended strongly on the 3d-atom type and the hydrogenation extent. More than the half of all of the 30 clusters had singlet lowest total energy states, which could be described as either nonmagnetic or antiferromagnetic. Hydrogenation increases the total spin magnetic moments of the M8O12H12 clusters when MMn Ni, which become larger by four Bohr magneton than those of the corresponding unary clusters M8. Hydrogenation substantially affects such properties as polarizability, forbidden band gaps, and dipole moments. Collective superexchange where the local total spin magnetic moments of two atom squads are coupled antiparallel was observed in antiferromagnetic singlet states of Fe8O12H8 and Co8O12H8, whereas the lowest total energy states of their neighbors Mn8O12H8 and Ni8O12H8 are ferrimagnetic and ferromagnetic, respectively. Hydrogenation leads to a decrease in the average binding energy per atom when moving across the 3d-metal atom series. © 2018 Wiley Periodicals, Inc. 相似文献
10.
《Arabian Journal of Chemistry》2019,12(4):476-488
The synthesis of compounds with an excellent adsorption capability plays an essential role to remove contaminants such as phthalic acid esters (PAEs) with potential carcinogenic characteristics from different food products. In this context, for the first time, a novel adsorbent (MWCNT-Fe3O4/Ag) was synthesized by using iron (magnetic agent), and silver (catalytic and surface enhancer agent) to further approach in a magnetic SPE-GC/MS method for determining of PAEs in carbonated soft drink samples. The limit of detection (LOD) and limit of quantification (LOQ) values of MSPE-GC/MS were determined in six PAEs as a range of 10.8–22.5 and 36–75 ng/L, respectively. Also, the calibration curves of PAEs were linear (R2 = 0.9981–0.9995) over the concentration level of 10.000 ng/L and the recoveries of the six PAEs were ranging from 96.60% to 109.22% with the RSDs less than 8%. Moreover, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and transmission electron microscopy analyses (TEM) were utilized to characterize the produced MWCNT-Fe3O4/Ag. Based on the findings, the surface of MWCNT is relatively uniform, which became coarser after loading with Fe3O4/Ag particles. Also, EDX spectrum showed the carbon (C), iron (Fe), oxygen (O), Ag and copper (Cu) are the main components of synthesized MWCNTs-Fe3O4/Ag. The successful adhesion of Fe3O4/Ag on the texture of MWCNTs using a co-precipitation method was confirmed by XRD and FT-IR assays. Additionally, excellent crystallinity and clear lattice nanocrystals fringes of prepared MWCNT-Fe3O4/Ag was demonstrated by TEM analysis. Based on the obtained VSM images, the prepared sorbent (MWCNT-Fe3O4/Ag) has the good magnetic performance for magnetic separation and extraction processes. It was concluded that the synthesized MWCNT-Fe3O4/Ag could be used as an efficient adsorbent for determining contaminants such as PAEs in different beverage samples. 相似文献