全文获取类型
收费全文 | 8846篇 |
免费 | 1535篇 |
国内免费 | 845篇 |
专业分类
化学 | 6283篇 |
晶体学 | 115篇 |
力学 | 490篇 |
综合类 | 63篇 |
数学 | 1057篇 |
物理学 | 3218篇 |
出版年
2024年 | 12篇 |
2023年 | 152篇 |
2022年 | 188篇 |
2021年 | 254篇 |
2020年 | 333篇 |
2019年 | 321篇 |
2018年 | 286篇 |
2017年 | 269篇 |
2016年 | 380篇 |
2015年 | 414篇 |
2014年 | 485篇 |
2013年 | 695篇 |
2012年 | 809篇 |
2011年 | 796篇 |
2010年 | 574篇 |
2009年 | 533篇 |
2008年 | 602篇 |
2007年 | 502篇 |
2006年 | 516篇 |
2005年 | 417篇 |
2004年 | 372篇 |
2003年 | 275篇 |
2002年 | 262篇 |
2001年 | 201篇 |
2000年 | 139篇 |
1999年 | 149篇 |
1998年 | 143篇 |
1997年 | 154篇 |
1996年 | 149篇 |
1995年 | 111篇 |
1994年 | 113篇 |
1993年 | 86篇 |
1992年 | 55篇 |
1991年 | 54篇 |
1990年 | 59篇 |
1989年 | 40篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 33篇 |
1985年 | 29篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
31.
Inside Back Cover: Deciphering a Nanocarbon‐Based Artificial Peroxidase: Chemical Identification of the Catalytically Active and Substrate‐Binding Sites on Graphene Quantum Dots (Angew. Chem. Int. Ed. 24/2015) 下载免费PDF全文
32.
33.
Dr. Christianus M. A. Leenders Gijs Jansen Martijn M. M. Frissen René P. M. Lafleur Dr. Ilja K. Voets Dr. Anja R. A. Palmans Prof. Dr. E. W. Meijer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4608-4615
We introduce monosaccharides as versatile water‐soluble units to compatibilise supramolecular polymers based on the benzene‐1,3,5‐tricarboxamide (BTA) moiety with water. A library of monosaccharide‐based BTAs is evaluated, varying the length of the alkyl chain (hexyl, octyl, decyl and dodecyl) separating the BTA and saccharide units, as well as the saccharide units (α‐glucose, β‐glucose, α‐mannose and α‐galactose). In all cases, the monosaccharides impart excellent water compatibility. The length of the alkyl chain is the determining factor to obtain either long, one‐dimensional supramolecular polymers (dodecyl spacer), small aggregates (decyl spacer) or molecularly dissolved (octyl and hexyl) BTAs in water. For the BTAs comprising a dodecyl spacer, our results suggest that a cooperative self‐assembly process is operative and that the introduction of different monosaccharides does not significantly change the self‐ assembly behaviour. Finally, we investigate the potential of post‐assembly functionalisation of the formed supramolecular polymers by taking advantage of dynamic covalent bond formation between the monosaccharides and benzoxaboroles. We observe that the supramolecular polymers readily react with a fluorescent benzoxaborole derivative permitting imaging of these dynamic complexes by confocal fluorescence microscopy. 相似文献
34.
Self‐Assembly and Compartmentalization of Nanozymes in Mesoporous Silica‐Based Nanoreactors 下载免费PDF全文
Yanyan Huang Dr. Youhui Lin Xiang Ran Prof. Dr. Jinsong Ren Prof. Dr. Xiaogang Qu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5705-5711
Herein, to mimic complex natural system, polyelectrolyte multilayer (PEM)‐coated mesoporous silica nanoreactors were used to compartmentalize two different artificial enzymes. PEMs coated on the surface of mesoporous silica could serve as a permeable membrane to control the flow of molecules. When assembling hemin on the surface of mesoporous silica, the hemin‐based mesoporous silica system possessed remarkable peroxidase‐like activity, especially at physiological pH, and could be recycled more easily than traditional graphene–hemin nanocompounds. The hope is that these new findings may pave the way for exploring novel nanoreactors to achieve compartmentalization of nanozymes and applying artificial cascade catalytic systems to mimic cell organelles or important biochemical transformations 相似文献
35.
The complex-scaled Green's function(CGF)method is employed to explore the single-proton resonance in 15F.Special attention is paid to the first excited resonant state 5/2+,which has been widely studied in both theory and experiments.However,past studies generally overestimated the width of the 5/2+state.The predicted energy and width of the first excited resonant state 5/2+by the CGF method are both in good agreement with the experimental value and close to Fortune's new estimation.Furthermore,the influence of the potential parameters and quadruple deformation effects on the resonant states are investigated in detail,which is helpful to the study of the shell structure evolution. 相似文献
36.
Meccanica - In this work, we have developed a systematic computational methodology to directly simulate the ductile fracture of ship hull structure during ship stranding based on the meshfree... 相似文献
37.
Cheng Ren Guanghao Ji Xiankai Li Prof. Jing Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(53):e202201442
The direct hydrodimerization of acrylates and acrylonitrile offers a general streamlined access to industrially important intermediates to nylon 6,6. However, a practical catalytic method for this process has thus far underdeveloped owing to the challenges in regioselectivity and environmental compatibility of applied reagents. Here, we report a cobalt-catalyzed tail-to-tail hydrodimerization of activated alkenes driven by a visible-light photoredox catalysis at ambient temperature, which is applicable to both adipates and adiponitrile synthesis from potentially renewable feedstocks. This protocol utilizes half equivalent of hantzsch ester as a recyclable two-electron and two-proton donor with the assistance of catalytic amount of base as a proton shuttle, and has been shown to be highly regioselective and efficient for hydrodimerizing various activated alkenes to 1,4-difunctionalized butane derivatives. 相似文献
38.
Dr. Qiuhua Liu Wanjie Ren Siwei Zhang Dr. Yang Huang Dilong Chen Dr. Wennan Zeng Prof. Dr. Zaichun Zhou Prof. Dr. Lin He Prof. Dr. Wenping Guo Prof. Dr. Jianfeng Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202103892
Both geometric architecture and electronic configurations of heme proteins contribute to its activity. In this work we designed and synthesized a series of four copper(II) porphyrin complexes ( 4 -, 3 -, 2 - and 1 -Cu) where the molecular conformations are modulated by a pair of stepwise shortened straps on the same porphyrin side (cis-ortho) to give double bow-shaped skeletons. Single crystal structures demonstrate that the straps gradually increase the saddle deformation and the deviation of the metal centers, which is in accordance with two, unusual d-orbital reconstructions of two different ground states, as revealed by 4 K EPR and DFT calculations. In the study of the electrocatalytic hydrogen evolution reaction (HER), 1 -Cu, with the shortest straps, showed the most apparent improvement of activity. Second coordination sphere (SCS) effects created by the double bow-shaped architecture and the strong saddle porphyrin core in 1 -Cu are found to play key roles in proton trapping during the catalytic process. The work contributes a novel strategy to improve the catalytic performance of heme analogs through ligand geometric modulation. 相似文献
39.
Sicheng Yang Dr. Jiaoyu Ren Prof. Hong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103867
The drug delivery system based on nano/micromotors has become a research hot spot in recent years. However, naked micromotors may be ruptured or passivated under the complex biological environment, which will result in the leakage of drugs in advance or limited self-propulsion performance. Herein, an injectable micromotor@hydrogel drug delivery system to protect micromotors from the external environment is proposed. The micromotors were prepared through layer-by-layer assembly technology. The asymmetric decomposition of hydrogen peroxide catalyzed by the locally distributed platinum nanoparticles enabled efficient propulsion of the micromotors in low concentration of hydrogen peroxide. In order to protect micromotors, they were loaded into the Schiff base hydrogel. The micromotor@hydrogel system can be injected directly into the lesion to release micromotors in response to the environment, reducing external influence on micromotors and improving the sustained-release effect. Erythromycin (Ery) loaded into the micromotors and the micromotor@hydrogel system demonstrated excellent antibacterial effect. Micromotors released from the hydrogel underwent enhanced diffusion in the surroundings of bacteria without addition of exogenous hydrogen peroxide, which was manifested by their appearance in edge of the inhibition zone. The proposed micromotor@hydrogel drug delivery system offers a new strategy for the treatment of bacterial infections. 相似文献
40.
Yao Wen Chen Yangfan Li Jiangling Yang Jian Ren Shan Liu Weizao Liu Qingcai 《Research on Chemical Intermediates》2022,48(5):1813-1829
Research on Chemical Intermediates - Industrial wastewater is becoming a universal environmental problem, wherein toxic organic compounds are important sources of pollution. For the degradation... 相似文献