全文获取类型
收费全文 | 3758篇 |
免费 | 567篇 |
国内免费 | 616篇 |
专业分类
化学 | 3126篇 |
晶体学 | 46篇 |
力学 | 155篇 |
综合类 | 77篇 |
数学 | 384篇 |
物理学 | 1153篇 |
出版年
2024年 | 10篇 |
2023年 | 68篇 |
2022年 | 158篇 |
2021年 | 134篇 |
2020年 | 162篇 |
2019年 | 192篇 |
2018年 | 141篇 |
2017年 | 151篇 |
2016年 | 200篇 |
2015年 | 178篇 |
2014年 | 228篇 |
2013年 | 240篇 |
2012年 | 323篇 |
2011年 | 345篇 |
2010年 | 247篇 |
2009年 | 232篇 |
2008年 | 265篇 |
2007年 | 244篇 |
2006年 | 198篇 |
2005年 | 186篇 |
2004年 | 166篇 |
2003年 | 115篇 |
2002年 | 141篇 |
2001年 | 120篇 |
2000年 | 85篇 |
1999年 | 70篇 |
1998年 | 43篇 |
1997年 | 33篇 |
1996年 | 42篇 |
1995年 | 43篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 25篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1961年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4941条查询结果,搜索用时 15 毫秒
121.
122.
Shan Jiang Yong-peng Zhao Yao Xie Miao Xu Huai-yu Cui Han Wu Yang Liu Qiang Xu Qi Wang 《Applied physics. B, Lasers and optics》2012,109(1):1-7
We demonstrated the lasing of Ne-like Ar 46.9?nm pumped by capillary discharge with the delay time between pre-pulse and main-pulse ranging from 2 to 130???s. Results show that the laser output reduced significantly when the delay time is much longer than 12???s. The temporal evolution of spontaneous radiation emitted from pre-ionized plasma implies that the observed reduction of the laser output is caused by the axial non-uniformity of pre-ionized plasma density and the decrease of pre-ionized plasma density. 相似文献
123.
Wei Zhao Yi Zhang Xiao Wang Xiaowen Hu Feng Liu Thomas P. Russell Guofu Zhou 《Journal of polymer science. Part A, Polymer chemistry》2018,56(20):1369-1375
Block copolymer (BCP) films with long-range lateral ordering and orientation are crucial for many applications. Here, we report a simple, versatile strategy based on a solution casting procedure, to produce millimeter thick film of BCPs with highly oriented nanostructures. Transmission electron microscope (TEM), small angle X-ray scattering (SAXS), and Hansen solubility parameters were used to study the morphology and interactions of the system. A variety of BCP-solvent pairs were investigated. Factors including set-up geometry, BCP characteristics, solvent evaporation, surface tension, and interactions, such as solvent-BCP, solvent-substrate, and BCP-substrate were examined. A mechanism is proposed to describe the observed long-range lateral ordering and orientation in films up to 1 mm in thickness. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1369–1375 相似文献
124.
125.
Abstract . The solvothermal reaction between cuprous iodide and the rigid triangular imidazole ligand in mixed N,N′‐dimethylacetamide (DMA)‐acetonitrile solvent leads to the isolation of the 3D metal‐organic framework [(Cu4I4)3(TIPA)4] · 7DMA ( 1 ) [TIPA = tri(4‐imidazolylphenyl) amine], which was characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Topologically, the structure of 1 is an unprecedented 3,3,4,4‐connected net with a point symbol of {4.8.10}2{4.82}2{42.82.102}2{84.122}. Compound 1 exhibits orange‐red photoluminescence with an emission maximum at 622 nm at room temperature. 相似文献
126.
Preparation of BiVO4/MIL‐125(Ti) composite with enhanced visible‐light photocatalytic activity for dye degradation 下载免费PDF全文
Zhiquan Yang Jie Ding Jinna Feng Chong He Ying Li Xiaowen Tong Xiaojun Niu Hongguo Zhang 《应用有机金属化学》2018,32(4)
Because of their desired features, including very specific surface areas and designable framework architecture together with their possibility to be functionalized, Metal Framework (MOF) is a promising platform for supporting varied materials in respect of catalytic applications in water treatment. In this work, a novel visible‐light‐responsive photocatalyst that comprised BiVO4 together with MIL‐125(Ti), was synthesized by a two‐step hydrothermal approach. The characterization of as‐obtained samples as performed by X‐ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscope, X‐ray photoelectron spectroscopy and ultraviolet‐visible diffuse reflection spectra. Rhodamine B was selected being a target for the evaluation of the photocatalytic function of as‐developed photocatalyst. The photocatalytic reaction parameters, for example, the content of BiVO4 as well as initial concentration of Rhodamine B was researched. The composite photocatalyst possessing Bi:Ti molar ratio of 3:2 brought to light the fact that the greatest photocatalytic activity had the ability to degrade 92% of Rhodamine B in 180 min. In addition to that, the BiVO4/MIL‐125(Ti) composite could keep its photocatalytic activity during the recycling test. The phenomenon of disintegration of the photo‐generated charges in the BiVO4/MIL‐125(Ti) composite was brought to discussion as well. 相似文献
127.
Recent advances in photocatalysis focus on the development of materials with hierarchical structure and on the surface plasmon resonance (SPR) phenomenon exhibited by metal nanoparticles (NPs). In this work, both are combined in a material where size‐controllable Ag‐NPs are uniformly loaded onto the hierarchical microporous and mesoporous and nanocolumnar structures of ZnO, resulting in Ag‐NP/ZnO nanocomposites. The embedded Ag‐NPs slightly decrease the hydrophobicity of fibrous ZnO, improve its wettability, and increase the absorption of formaldehyde (H2CO) onto the photocatalyst, all of this resulting in excellent photodegradation of formaldehyde in aqueous solution. Besides, we found that Ag‐NPs with optimal size not only accelerate the charge transfer to the surface of ZnO, but also strengthen the SPR effect in the intercolumnar channels of fibrous ZnO particles combining with high concentration of photo‐generated radical species. The micro‐to‐mesoporous ZnO is like a nanoarray packed Ag‐NPs. With Ag‐NPs of diameter 2.5 < ? < 6.5 nm, ZnO exhibits the most superior photodegradation rate constant value of 0.0239 min?1 with total formaldehyde removal of 97%. This work presents a new feasible approach involving highly sophisticated Ag‐NP/ZnO architecture combining the SPR effect and hierarchically ordered structures, which results in high photocatalytic activity for formaldehyde photodegradation. 相似文献
128.
Julia Ertl Dr. Maria Elena Ortiz-Soto Thien Anh Le Julian Bechold Junwen Shan Dr. Jörg Teßmar Prof. Bernd Engels Prof. Jürgen Seibel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6533-6541
Selective chemical modification of proteins plays a pivotal role for the rational design of enzymes with novel and specific functionalities. In this study, a strategic combination of genetic and chemical engineering paves the way for systematic construction of biocatalysts by tuning the product spectrum of a levansucrase from Bacillus megaterium (Bm-LS), which typically produces small levan-like oligosaccharides. The implementation of site-directed mutagenesis followed by a tyrosine-specific modification enabled control of the product synthesis: depending on the position, the modification provoked either enrichment of short oligosaccharides (up to 800 % in some cases) or triggered the formation of high molecular weight polymer. The chemical modification can recover polymerization ability in variants with defective oligosaccharide binding motifs. Molecular dynamic (MD) simulations provided insights into the effect of modifying non-native tyrosine residues on product specificity. 相似文献
129.
130.
Jiarui Yu Nan Gao Xiaowen Xie Xing Xin Zhanqi Li Shuai Chen Jingkun Xu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(5):794-802
Thermally healing capability of cracks and defects is important and urgent for the safe operation and life extending of electric materials and devices. Here, by the combination of thermally driven reversible Diels–Alder (DA) interaction and in-situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT), a series of intrinsically conductive poly(3,4-ethylenedioxythiophene) (PEDOT)/DA composites possess intrinsically self-healing property under low-temperature (reverse DA reaction at 100°C; DA crosslinking at 60°C) stimulus were achieved. The crosslinking DA bonding reactions are multiple from the co-existence of pre-synthesized macromolecular polyurethane attached DA units (PU-DA) and 2,4-hexadiyne-1,6-diol (DADOL) in the films. PU-DA involved in the polymerization process of EDOT to endow PEDOT with outstanding solution-processability, uniform film making, and structural self-healing capability, while DADOL was added to enhance the cross bonding between polymer chains. This work will accelerate the research and application development of intrinsically self-healing conducting polymers for commercial capacitors, antistatic coatings, implantable, printable electronics, and so on. 相似文献