全文获取类型
收费全文 | 2440篇 |
免费 | 316篇 |
国内免费 | 342篇 |
专业分类
化学 | 1927篇 |
晶体学 | 40篇 |
力学 | 121篇 |
综合类 | 26篇 |
数学 | 342篇 |
物理学 | 642篇 |
出版年
2024年 | 8篇 |
2023年 | 41篇 |
2022年 | 96篇 |
2021年 | 70篇 |
2020年 | 100篇 |
2019年 | 107篇 |
2018年 | 98篇 |
2017年 | 81篇 |
2016年 | 103篇 |
2015年 | 133篇 |
2014年 | 129篇 |
2013年 | 185篇 |
2012年 | 210篇 |
2011年 | 214篇 |
2010年 | 148篇 |
2009年 | 129篇 |
2008年 | 157篇 |
2007年 | 131篇 |
2006年 | 131篇 |
2005年 | 114篇 |
2004年 | 107篇 |
2003年 | 78篇 |
2002年 | 96篇 |
2001年 | 70篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 40篇 |
1997年 | 26篇 |
1996年 | 33篇 |
1995年 | 19篇 |
1994年 | 27篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有3098条查询结果,搜索用时 15 毫秒
61.
Photo-Induced Ultrafast Electron Dynamics in Anatase and Rutile TiO2: Effects of Electron-Phonon Interaction 下载免费PDF全文
The photo-induced ultrafast electron dynamics in both anatase and rutile TiO\begin{document}$_{2}$\end{document} are investigated by using the Boltzmann transport equation with the explicit incorporation of electron-phonon scattering rates. All structural parameters required for dynamic simulations are obtained from ab initio calculations. The results show that although the longitudinal optical modes significantly affect the electron energy relaxation dynamics in both phases due to strong Fr?hlich-type couplings, the detailed relaxation mechanisms have obvious differences. In the case of a single band, the energy relaxation time in anatase is 24.0 fs, twice longer than 11.8 fs in rutile. This discrepancy is explained by the different diffusion distributions over the electronic Bloch states and different scattering contributions from acoustic modes in the two phases. As for the multiple-band situation involving the lowest six conduction bands, the predicted overall relaxation times are about 47 fs and 57 fs in anatase and rutile, respectively, very different from the case of the single band. The slower relaxation in rutile is attributed to the existence of multiple rate-controlled steps during the dynamic process. The present findings may be helpful to control the electron dynamics for designing efficient TiO\begin{document}$_{2}$\end{document} -based devices. 相似文献
62.
WeiPing Liu ZhiHong Li JiangJun He XiaoDong Tang Gang Lian Zhu An JianJun Chang Han Chen QingHao Chen XiongJun Chen ZhiJun Chen BaoQun Cui XianChao Du ChangBo Fu Lin Gan Bing Guo GuoZhu He Alexander Heger SuQing Hou HanXiong Huang Ning Huang BaoLu Jia LiYang Jiang Shigeru Kubono JianMin Li KuoAng Li Tao Li YunJu Li Maria Lugaro XiaoBing Luo HongYi Ma ShaoBo Ma DongMing Mei YongZhong Qian JiuChang Qin Jie Ren YangPing Shen Jun Su LiangTing Sun WanPeng Tan Isao Tanihata Shuo Wang Peng Wang YouBao Wang Qi Wu ShiWei Xu ShengQuan Yan LiTao Yang Yao Yang XiangQing Yu Qian Yue Sheng Zeng HuanYu Zhang Hui Zhang LiYong Zhang NingTao Zhang QiWei Zhang Tao Zhang XiaoPeng Zhang XueZhen Zhang ZiMing Zhang Wei Zhao Zuo Zhao Chao Zhou JUNA Collaboration 《中国科学:物理学 力学 天文学(英文版)》2016,59(4):642001
Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given. 相似文献
63.
JianJun He ShiWei Xu ShaoBo Ma Jun Hu LiYong Zhang ChangBo Fu NingTao Zhang Gang Lian Jun Su YunJu Li ShengQuan Yan YangPing Shen SuQing Hou BaoLu Jia Tao Zhang XiaoPeng Zhang Bing Guo Shigeru Kubono WeiPing Liu 《中国科学:物理学 力学 天文学(英文版)》2016,59(5):652001
In 2014, the National Natural Science Foundation of China(NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory(JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch(AGB) stars, measuring the key ~(19)F( p,α)~(16)O reaction at effective burning energies(i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions. 相似文献
64.
Chromatographia - The application of temperature gradient interaction chromatography (TGIC) as an advanced technique for the characterisation of polymers is discussed, in comparison to other liquid... 相似文献
65.
Noah Schwarz Xiaofei Sun Dr. Ravi Yadav Dr. Ralf Köppe Dr. Thomas Simler Prof. Dr. Peter W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(50):12857-12865
Divalent lanthanide and alkaline-earth complexes supported by N-heterocyclic carbene (NHC) ligands have been accessed by redox-transmetalation between air-stable NHC-AgI complexes and the corresponding metals. By using the small ligand 1,3-dimethylimidazol-2-ylidene (IMe), two series of isostructural complexes were obtained: the tetra-NHC complexes [LnI2(IMe)4] (Ln=Eu and Sm) and the bis-NHC complexes [MI2(IMe)2(THF)2] (M=Yb, Ca and Sr). In the former, distortions in the NHC coordination were found to originate from intermolecular repulsions in the solid state. Application of the redox-transmetalation strategy with the bulkier 1,3-dimesitylimidazol-2-ylidene (IMes) ligand yielded [SrI2(IMes)(THF)3], while using a similar procedure with Ca metal led to [CaI2(THF)4] and uncoordinated IMes. DFT calculations were performed to rationalise the selective formation of the bis-NHC adduct in [SrI2(IMe)2(THF)2] and the tetra-NHC adduct in [SmI2(IMe)4]. Since the results in the gas phase point towards preferential formation of the tetra-NHC complexes for both metal centres, the differences between both arrangements are a result of solid-state effects such as slightly different packing forces. 相似文献
66.
Chun Lian Zhang Xi Fu Jiang Li Yang Shu Hua Zhang Shao Ming Shi 《Journal of Cluster Science》2014,25(2):459-466
A rare heterometallic cluster-based polymer [Cu4(Hbhea)4(μ 2-OCH3) K(CH3OH))] n ·(H2O) n (1) (H3bhea = 2-[bis-(2-hydroxy-ethyl)-amino]-ethanesulfonic acid), has been synthesized and structurally determined by single crystal X-ray diffraction, elemental analysis. Crystallographic unit of 1 consists of four Cu(II), four Hbhea ligands, one methanol molecule, one methanol anion, one K ion and one crystal lattice water and formed anion cluster [Cu4(Hbhea)4(CH3O)]? which further constructed a 3-D polymer by linking the six-coordination K ions. 相似文献
67.
Chunxia Jia Qing Wang Jianxin Ge Xiaofei Xu 《Journal of Thermal Analysis and Calorimetry》2014,116(2):1073-1081
Thermogravimetric (TG) data of oil sand obtained at Engineering Research Center of Oil Shale Comprehensive Utilization were studied to evaluate the kinetic parameters for Indonesian oil sand samples. Experiments were carried out at heating rates of 5, 15, and 25 °C min?1 in nitrogen, 10, 20, and 50 °C min?1 in oxygen atmosphere, respectively. The extent of char combustion was found out by relating TG data for pyrolysis and combustion with the ultimate analysis. Due to distinct behavior of oil shale during pyrolysis, TG curves were divided into three separate events: moisture release, devolatilization, and evolution of fixed carbon/char, where for each event, kinetic parameters, based on Arrhenius theory, were calculated. Coats–Redfern method, Flynn–Wall–Ozawa method, and distributed activation energy model method have been used to determine the activation energies of degradation. The methods are compared with regard to their characteristics and the ease of interpretation of the thermal kinetics. Activation energies of the samples were determined by three different methods and the results are discussed. 相似文献
68.
Chemically synthesized single‐crystalline gold microplates have been attracting increasing interest because of their potential as high‐quality gold films for nanotechnology. We present the growth of tens of nanometers thick and tens of micrometers large single‐crystalline gold plates directly on solid substrates by solution‐phase synthesis. Compared to microplates deposited on substrates from dispersion phase, substrate‐grown plates exhibit significantly higher quality by avoiding severe small‐particle contamination and aggregation. Substrate‐grown gold plates also open new perspectives to study the growth mechanism via step‐growth and observation cycles of a large number of individual plates. Growth models are proposed to interpret the evolution of thickness, area and shape of the plates. It is found that the plate surface remains smooth after regrowth, implying the applicability of regrowth for producing giant plates as well as unique single‐crystalline nano‐structures. 相似文献
69.
Xiaotian Tian Sai Lian Limin Zhao Xiaomei Chen Zhiyong Huang Xi Chen 《Journal of Solid State Electrochemistry》2014,18(9):2375-2382
A novel electrochemiluminescence (ECL) biosensor based on platinum nanoflowers (PtNFs)/graphene oxide (GO)/glucose oxidase (GODx) was discovered for glucose detection. PtNFs/GO was synthesized using a nontoxic, rapid, one-pot and template-free method and characterized by transmission electron microscopy (TEM) and high-resolution TEM techniques. The as-prepared PtNFs/GO with clean surface and multiporous structure was used to assemble GODx to form a glucose biosensor. Based on ECL results, the PtNFs/GO/GODx film-modified electrode displayed a high electrocatalytic activity towards the oxidation of glucose, which generated hydrogen peroxide (H2O2) to react with the luminol radicals thus enhanced the luminol ECL. Under the optimized conditions, two linear regions of ECL intensity to glucose concentration were valid in the range from 5 to 80 μmol/L (r?=?0.9957) and 80 to 1,000 μmol/L (r?=?0.9909) with a detection limit (S/N?=?3) of 2.8 μmol/L. In order to verify the reliability, the thus-fabricated biosensor was applied to determine the glucose concentration in glucose injection, glucose functional drink, and blood serum. The results indicated that the proposed biosensor presented good characteristics in terms of high sensitivity and good reproducibility for glucose determination, promising the applicability of this sensor in practical analysis. 相似文献
70.
An oligosaccharide donor, acetylated sept-o-glucopyranose tetradecyl carbamate, was designed and synthesized. This compound could be easily linked to hydroxyl-containing compounds through an Oglycosidic bond. Characterization of all the oligosaccharide intermediates and the final product was thoroughly discussed. 相似文献