全文获取类型
收费全文 | 29303篇 |
免费 | 15830篇 |
国内免费 | 19篇 |
出版年
2023年 | 23篇 |
2022年 | 119篇 |
2021年 | 468篇 |
2020年 | 2200篇 |
2019年 | 3740篇 |
2018年 | 3855篇 |
2017年 | 4112篇 |
2016年 | 4145篇 |
2015年 | 4179篇 |
2014年 | 3840篇 |
2013年 | 4272篇 |
2012年 | 2029篇 |
2011年 | 1752篇 |
2010年 | 3175篇 |
2009年 | 1887篇 |
2008年 | 844篇 |
2007年 | 427篇 |
2006年 | 433篇 |
2005年 | 452篇 |
2004年 | 429篇 |
2003年 | 370篇 |
2002年 | 348篇 |
2001年 | 373篇 |
2000年 | 281篇 |
1999年 | 183篇 |
1998年 | 49篇 |
1997年 | 40篇 |
1996年 | 46篇 |
1995年 | 31篇 |
1994年 | 46篇 |
1993年 | 35篇 |
1992年 | 73篇 |
1991年 | 53篇 |
1990年 | 57篇 |
1989年 | 64篇 |
1988年 | 39篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 45篇 |
1984年 | 38篇 |
1983年 | 33篇 |
1982年 | 49篇 |
1979年 | 42篇 |
1978年 | 25篇 |
1977年 | 33篇 |
1976年 | 33篇 |
1975年 | 40篇 |
1974年 | 36篇 |
1973年 | 40篇 |
1971年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 320 毫秒
981.
Pau Rodenas Taesup Song Pitchaimuthu Sudhagar Gabriela Marzari Hyungkyu Han Laura Badia‐Bou Sixto Gimenez Francisco Fabregat‐Santiago Ivan Mora‐Sero Juan Bisquert Ungyu Paik Yong Soo Kang 《Liver Transplantation》2013,3(2):176-182
TiO2 hollow nanowires (HNWs) and nanoparticles (NPs) constitute promising architectures for QDs sensitized photoanodes for H2 generation. We sensitize these structures with CdS/CdSe quantum dots by two different methods (chemical bath deposition, CBD and succesive ionic layer adsorption and reaction, SILAR) and evaluate the performance of these photoelectrodes. Remarkable photocurrents of 4 mA·cm and 8 mA·cm?2 and hydrogen generation rates of 40 ml·cm?2·day?1 and 80 ml·cm?2·day?1 have been obtained in a three electrode configuration with sacrificial hole scavengers (Na2S and Na2SO3), for HNWs and NPs respectively, which is confirmed through gas analysis. More importantly, autonomous generation of H2 (20 ml·cm?2·day?1 corresponding to 2 mA·cm?2 photocurrent) is obtained in a two electrode configuration at short circuit under 100 mW·cm?2 illumination, clearly showing that these photoanodes can produce hydrogen without the assistance of any external bias. To the best of the authors' knowledge, this is the highest unbiased solar H2 generation rate reported for these of QDs based heterostructures. Impedance spectroscopy measurements show similar electron density of trap states below the TiO2 conduction band while the recombination resistance was higher for HNWs, consistently with the much lower surface area compared to NPs. However, the conductivity of both structures is similar, in spite of the one dimensional character of HNWs, which leaves some room for improvement of these nanowired structures. The effect of the QDs deposition method is also evaluated. Both structures show remarkable stability without any appreciable photocurrent loss after 0.5 hour of operation. The findings of this study constitute a relevant step towards the feasibility of hydrogen generation with wide bandgap semiconductors/quantum dots based heterostructures. 相似文献
982.
983.
Cephas E. Small Sai‐Wing Tsang Song Chen Sujin Baek Chad M. Amb Jegadesan Subbiah John R. Reynolds Franky So 《Liver Transplantation》2013,3(7):909-916
Polymer bulk heterojunction solar cells based on low bandgap polymer:fullerene blends are promising for next generation low‐cost photovoltaics. While these solution‐processed solar cells are compatible with large‐scale roll‐to‐roll processing, active layers used for typical laboratory‐scale devices are too thin to ensure high manufacturing yields. Furthermore, due to the limited light absorption and optical interference within the thin active layer, the external quantum efficiencies (EQEs) of bulk heterojunction polymer solar cells are severely limited. In order to produce polymer solar cells with high yields, efficient solar cells with a thick active layer must be demonstrated. In this work, the performance of thick‐film solar cells employing the low‐bandgap polymer poly(dithienogermole‐thienopyrrolodione) (PDTG‐TPD) was demonstrated. Power conversion efficiencies over 8.0% were obtained for devices with an active layer thickness of 200 nm, illustrating the potential of this polymer for large‐scale manufacturing. Although an average EQE > 65% was obtained for devices with active layer thicknesses > 200 nm, the cell performance could not be maintained due to a reduction in fill factor. By comparing our results for PDTG‐TPD solar cells with similar P3HT‐based devices, we investigated the loss mechanisms associated with the limited device performance observed for thick‐film low‐bandgap polymer solar cells. 相似文献
984.
Valerio Zardetto Francesco Di Giacomo Diana Garcia‐Alonso Wytze Keuning Mariadriana Creatore Claudia Mazzuca Andrea Reale Aldo Di Carlo Thomas M. Brown 《Liver Transplantation》2013,3(10):1292-1298
The application of UV irradiation processes are successfully proposed for the first time in the fabrication of both of the two plastic electrodes in flexible dye solar cells (DSCs) and modules. For the realization of the photo‐electrode, a customized TiO2 paste formulation and UV processing method was developed which yields 134% (48%) performance enhancement with respect to the same (binder‐free) paste treated at 120 °C. UV treatment induces both complete removal of organic media and more efficient charge collection. Significantly, highly catalytic platinized flexible counter‐electrodes are also obtained via UV photo‐induced reduction of screen‐printed platinum precursor pastes based on hexachloroplatinic acid. Using both UV‐processed electrodes, a fully plastic DSC is fabricated with a conversion efficiency of 4.3% under 1 Sun (semitransparent) and 5.3% under 0.2 Sun (opaque). Performance is within 10% of the efficiency of a glass‐based DSC prepared with the same materials but with conventional high temperature processes. The material formulations and processes are simple, and easily up‐scaled over large areas, even directly and simultaneously applicable to the preparation of both the photo‐and counter‐electrode on the same substrate which enabled us to demonstrate the first module on plastic realized with a W series interconnection. 相似文献
985.
Huilin Pan Xia Lu Xiqian Yu Yong‐Sheng Hu Hong Li Xiao‐Qing Yang Liquan Chen 《Liver Transplantation》2013,3(9):1186-1194
Layered sodium titanium oxide, Na2Ti3O7, is synthesized by a solid‐state reaction method as a potential anode for sodium‐ion batteries. Through optimization of the electrolyte and binder, the microsized Na2Ti3O7 electrode delivers a reversible capacity of 188 mA h g?1 in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0–3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na+/Na, in good agreement with a first‐principles prediction of 0.35 V. The Na storage properties in Na2Ti3O7 are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na2Ti3O7 exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid‐state interphase layer on Na2Ti3O7 electrode is analyzed. A zero‐current overpotential related to thermodynamic factors is observed for both nano‐ and microsized Na2Ti3O7. The electronic structure, Na+ ion transport and conductivity are investigated by the combination of first‐principles calculation and electrochemical characterizations. On the basis of the vacancy‐hopping mechanism, a quasi‐3D energy favorable trajectory is proposed for Na2Ti3O7. The Na+ ions diffuse between the TiO6 octahedron layers with pretty low activation energy of 0.186 eV. 相似文献
986.
Yu-Hsiang Lee Yu-Ling Yeh Keng-Hsien Lin Yu-Chih Hsu 《Bioprocess and biosystems engineering》2013,36(8):1071-1078
The commercial value of marine Nannochloropsis oculata has been recognized due to its high content of eicosapentaenoic acid (>50 % w/w). To make it as a profitable bioresource, one of the most desirable goals is to develop a quality-controlled, cost-effective, and large-scale photobioreactor for N. oculata growth. Generally, closed culture system can offer many advantages over open system such as small space requirement, controllable process and low risk of contamination. However, oxygen accumulation is often a detrimental factor for enclosed microalgal culture that has seriously hampered the development of microalga-related industries. In this study, we proposed to use fluorochemical as oxygen carrier to overcome the challenge where four liquid fluorochemicals namely perfluorooctyl bromide, perfluorodecalin, methoxynonafluorobutane, and ethoxynonafluorobutane were investigated separately. Our results showed that the microalgal proliferation with different fluorinated liquids was similar and comparable to the culture without a fluorochemical. When cultured in the photobioreactor with 60 % oxygen atmosphere, the N. oculata can grow up in all the fluorochemical photobioreactors, but completely inhibited in the chamber without a fluorochemical. Moreover, the perfluorooctyl bromide system exhibited the most robust efficacy of oxygen removal in the culture media (perfluorooctyl bromide > perfluorodecalin > methoxynonafluorobutane > ethoxynonafluorobutane), and yielded a >3-fold increase of biomass production after 5 days. In summary, the developed fluorochemical photobioreactors offer a feasible means for N. oculata growth in closed and large-scale setting without effect of oxygen inhibition. 相似文献
987.
Guang‐Ping Hao An‐Hui Lu Wei Dong Zhen‐Yu Jin Xiang‐Qian Zhang Jin‐Tao Zhang Wen‐Cui Li 《Liver Transplantation》2013,3(11):1421-1427
Sandwich‐type microporous hybrid carbon nanosheets (MHCN) consisting of graphene and microporous carbon layers are fabricated using graphene oxides as shape‐directing agent and the in‐situ formed poly(benzoxazine‐co‐resol) as carbon precursor. The reaction and condensation can be readily completed within 45 min. The obtained MHCN has a high density of accessible micropores that reside in the porous carbon with controlled thickness (e.g., 17 nm), a high surface area of 1293 m2 g?1 and a narrow pore size distribution of ca. 0.8 nm. These features allow an easy access, a rapid diffusion and a high loading of charged ions, which outperform the diffusion rate in bulk carbon and are highly efficient for an increased double‐layer capacitance. Meanwhile, the uniform graphene percolating in the interconnected MHCN forms the bulk conductive networks and their electrical conductivity can be up to 120 S m?1 at the graphene percolation threshold of 2.0 wt.%. The best‐practice two‐electrode test demonstrates that the MHCN show a gravimetric capacitance of high up to 103 F g?1 and a good energy density of ca. 22.4 Wh kg?1 at a high current density of 5 A g?1. These advanced properties ensure the MHCN a great promise as an electrode material for supercapacitors. 相似文献
988.
Marcus Bär Joachim Klaer Lothar Weinhardt Regan G. Wilks Stefan Krause Monika Blum Wanli Yang Clemens Heske Hans‐Werner Schock 《Liver Transplantation》2013,3(6):777-781
The surface properties of CuInS2 (CIS) thin‐film solar cell absorbers are investigated by a combination of electron and soft X‐ray spectroscopies. Spatially separated regions of varying colors are observed and identified to be dominated by either CuS or Cu2S surface phases. After their removal by KCN etching, the samples cannot be distinguished by eye and the CIS surface is found to be Cu‐deficient in both regions. However, a significantly more pronounced off‐stoichiometry in the region initially covered by Cu2S can be identified. In this region, the resulting surface band gap is also significantly larger than the EgSurf of the initially CuS‐terminated region. Such variations may represent a hidden parameter which, if overlooked, induces irreproducibility and thus prevents systematic optimization efforts. 相似文献
989.
Chien‐Chen Lai Kai‐Zen Lu Man‐Tzu Chiu Tsung‐Han Hsieh Lei Wan Cheng‐Wen Lin 《Proteomics》2013,13(23-24):3442-3456
Japanese encephalitis virus (JEV) nonstructural protein 5 (NS5) exhibits a Type I interferon (IFN) antagonistic function. This study characterizes Type I IFN antagonism mechanism of NS5 protein, using proteomic approach. In human neuroblastoma cells, NS5 expression would suppress IFNβ‐induced responses, for example, expression of IFN‐stimulated genes PKR and OAS as well as STAT1 nuclear translocation and phosphorylation. Proteomic analysis showed JEV NS5 downregulating calreticulin, while upregulating cyclophilin A, HSP 60 and stress‐induced‐phosphoprotein 1. Gene silence of calreticulin raised intracellular Ca2+ levels while inhibiting nuclear translocalization of STAT1 and NFAT‐1 in response to IFNβ, thus, indicating calreticulin downregulation linked with Type I IFN antagonism of JEV NS5 via activation of Ca2+/calicineurin. Calcineurin inhibitor cyclosporin A attenuated NS5‐mediated inhibition of IFNβ‐induced responses, for example, IFN‐sensitive response element driven luciferase, STAT1‐dependent PKR mRNA expression, as well as phosphorylation and nuclear translocation of STAT1. Transfection with calcineurin (vs. control) siRNA enhanced nuclear translocalization of STAT1 and upregulated PKR expression in NS5‐expressing cells in response to IFNβ. Results prove Ca2+, calreticulin, and calcineurin involvement in STAT1‐mediated signaling as well as a key role of JEV NS5 in Type I IFN antagonism. This study offers insights into the molecular mechanism of Type I interferon antagonism by JEV NS5. 相似文献
990.
In the present work, we report a novel on‐target protein cleavage method. The method utilizes ultrasonic energy and allows up to 20 samples to be cleaved in 5 min for protein identification and one sample in 30 s for on‐tissue digestion. The standard proteins were spotted on a conductive glass slide in a volume of 0.5 μL followed by 5 min of ultrasonication after trypsin addition. Controls (5 min, 37°C no ultrasonication) were also assayed. After trypsin addition, digestion of the tissues was enhanced by 30 s of ultrasonication. The samples were analyzed and compared to those obtained by using conventional 3 h heating proteolysis. The low sample volume needed for the digestion and reduction in sample‐handling steps and time are the features that make this method appealing to the many laboratories working with high‐throughput sample treatment. 相似文献