全文获取类型
收费全文 | 3155篇 |
免费 | 235篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 49篇 |
综合类 | 16篇 |
化学工业 | 691篇 |
金属工艺 | 111篇 |
机械仪表 | 74篇 |
建筑科学 | 284篇 |
矿业工程 | 25篇 |
能源动力 | 114篇 |
轻工业 | 163篇 |
水利工程 | 31篇 |
石油天然气 | 2篇 |
无线电 | 246篇 |
一般工业技术 | 698篇 |
冶金工业 | 165篇 |
原子能技术 | 11篇 |
自动化技术 | 717篇 |
出版年
2023年 | 64篇 |
2022年 | 65篇 |
2021年 | 118篇 |
2020年 | 108篇 |
2019年 | 102篇 |
2018年 | 123篇 |
2017年 | 98篇 |
2016年 | 152篇 |
2015年 | 137篇 |
2014年 | 158篇 |
2013年 | 230篇 |
2012年 | 239篇 |
2011年 | 274篇 |
2010年 | 186篇 |
2009年 | 178篇 |
2008年 | 175篇 |
2007年 | 168篇 |
2006年 | 106篇 |
2005年 | 92篇 |
2004年 | 87篇 |
2003年 | 55篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1972年 | 3篇 |
1967年 | 4篇 |
1961年 | 3篇 |
排序方式: 共有3397条查询结果,搜索用时 15 毫秒
991.
Jingjing Tian Qifan Xue Xiaofeng Tang Yuxuan Chen Ning Li Zhicheng Hu Tingting Shi Xin Wang Fei Huang Christoph J. Brabec Hin‐Lap Yip Yong Cao 《Advanced materials (Deerfield Beach, Fla.)》2019,31(23)
A synergic interface design is demonstrated for photostable inorganic mixed‐halide perovskite solar cells (PVSCs) by applying an amino‐functionalized polymer (PN4N) as cathode interlayer and a dopant‐free hole‐transporting polymer poly[5,5′‐bis(2‐butyloctyl)‐(2,2′‐bithiophene)‐4,4′‐dicarboxylate‐alt‐5,5′‐2,2′‐bithiophene] (PDCBT) as anode interlayer. First, the interfacial dipole formed at the cathode interface reduces the workfunction of SnO2, while PDCBT with deeper‐lying highest occupied molecular orbital (HOMO) level provides a better energy‐level matching at the anode, leading to a significant enhancement in open‐circuit voltage (Voc) of the PVSCs. Second, the PN4N layer can also tune the surface wetting property to promote the growth of high‐quality all‐inorganic perovskite films with larger grain size and higher crystallinity. Most importantly, both theoretical and experimental results reveal that PN4N and PDCBT can interact strongly with the perovskite crystal, which effectively passivates the electronic surface trap states and suppresses the photoinduced halide segregation of CsPbI2Br films. Therefore, the optimized CsPbI2Br PVSCs exhibit reduced interfacial recombination with efficiency over 16%, which is one of the highest efficiencies reported for all‐inorganic PVSCs. A high photostability with a less than 10% efficiency drop is demonstrated for the CsPbI2Br PVSCs with dual interfacial modifications under continuous 1 sun equivalent illumination for 400 h. 相似文献
992.
Venkata R. Nallagatla Thomas Heisig Christoph Baeumer Vitaliy Feyer Matteo Jugovac Giovanni Zamborlini Claus M. Schneider Rainer Waser Miyoung Kim Chang Uk Jung Regina Dittmann 《Advanced materials (Deerfield Beach, Fla.)》2019,31(40)
Redox‐based memristive devices are one of the most attractive candidates for future nonvolatile memory applications and neuromorphic circuits, and their performance is determined by redox processes and the corresponding oxygen‐ion dynamics. In this regard, brownmillerite SrFeO2.5 has been recently introduced as a novel material platform due to its exceptional oxygen‐ion transport properties for resistive‐switching memory devices. However, the underlying redox processes that give rise to resistive switching remain poorly understood. By using X‐ray absorption spectromicroscopy, it is demonstrated that the reversible redox‐based topotactic phase transition between the insulating brownmillerite phase, SrFeO2.5, and the conductive perovskite phase, SrFeO3, gives rise to the resistive‐switching properties of SrFeOx memristive devices. Furthermore, it is found that the electric‐field‐induced phase transition spreads over a large area in (001) oriented SrFeO2.5 devices, where oxygen vacancy channels are ordered along the in‐plane direction of the device. In contrast, (111)‐grown SrFeO2.5 devices with out‐of‐plane oriented oxygen vacancy channels, reaching from the bottom to the top electrode, show a localized phase transition. These findings provide detailed insight into the resistive‐switching mechanism in SrFeOx‐based memristive devices within the framework of metal–insulator topotactic phase transitions. 相似文献
993.
994.
Bjrn Kirchhoff Laura Braunwarth Christoph Jung Hannes Jnsson Donato Fantauzzi Timo Jacob 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(5)
Improved understanding of the fundamental processes leading to degradation of platinum nanoparticle electrocatalysts is essential to the continued advancement of their catalytic activity and stability. To this end, the oxidation of platinum nanoparticles is simulated using a ReaxFF reactive force field within a grand‐canonical Monte Carlo scheme. 2–4 nm cuboctahedral particles serve as model systems, for which electrochemical potential‐dependent phase diagrams are constructed from the thermodynamically most stable oxide structures, including solvation and thermochemical contributions. Calculations in this study suggest that surface oxide structures should become thermodynamically stable at voltages around 0.80–0.85 V versus standard hydrogen electrode, which corresponds to typical fuel cell operating conditions. The potential presence of a surface oxide during catalysis is usually not accounted for in theoretical studies of Pt electrocatalysts. Beyond 1.1 V, fragmentation of the catalyst particles into [Pt6O8]4? clusters is observed. Density functional theory calculations confirm that [Pt6O8]4? is indeed stable and hydrophilic. These results suggest that the formation of [Pt6O8]4? may play an important role in platinum catalyst degradation as well as the electromotoric transport of Pt2+/4+ ions in fuel cells. 相似文献
995.
996.
Marie‐Ingrid Richard Thomas W. Cornelius Florian Lauraux Jean‐Baptiste Molin Christoph Kirchlechner Steven J. Leake Jrme Carnis Tobias U. Schülli Ludovic Thilly Olivier Thomas 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(6)
Compression of micropillars is followed in situ by a quick nanofocused X‐ray scanning microscopy technique combined with 3D reciprocal space mapping. Compared to other attempts using X‐ray nanobeams, it avoids any motion or vibration that would lead to a destruction of the sample. The technique consists of scanning both the energy of the incident nanofocused X‐ray beam and the in‐plane translations of the focusing optics along the X‐ray beam. Here, the approach by imaging the strain and lattice orientation of Si micropillars and their pedestals during in situ compression is demonstrated. Varying the energy of the incident beam instead of rocking the sample and mapping the focusing optics instead of moving the sample supplies a vibration‐free measurement of the reciprocal space maps without removal of the mechanical load. The maps of strain and lattice orientation are in good agreement with the ones recorded by ordinary rocking‐curve scans. Variable‐wavelength quick scanning X‐ray microscopy opens the route for in situ strain and tilt mapping toward more diverse and complex materials environments, especially where sample manipulation is difficult. 相似文献
997.
Agnieszka Mech Wendel Wohlleben Antoine Ghanem Vasile‐Dan Hodoroaba Stefan Weigel Frank Babick Raphael Brüngel Christoph M. Friedrich Kirsten Rasmussen Hubert Rauscher 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(36)
Identifying nanomaterials (NMs) according to European Union legislation is challenging, as there is an enormous variety of materials, with different physico‐chemical properties. The NanoDefiner Framework and its Decision Support Flow Scheme (DSFS) allow choosing the optimal method to measure the particle size distribution by matching the material properties and the performance of the particular measurement techniques. The DSFS leads to a reliable and economic decision whether a material is an NM or not based on scientific criteria and respecting regulatory requirements. The DSFS starts beyond regulatory requirements by identifying non‐NMs by a proxy approach based on their volume‐specific surface area. In a second step, it identifies NMs. The DSFS is tested on real‐world materials and is implemented in an e‐tool. The DSFS is compared with a decision flowchart of the European Commission’s (EC) Joint Research Centre (JRC), which rigorously follows the explicit criteria of the EC NM definition with the focus on identifying NMs, and non‐NMs are identified by exclusion. The two approaches build on the same scientific basis and measurement methods, but start from opposite ends: the JRC Flowchart starts by identifying NMs, whereas the NanoDefiner Framework first identifies non‐NMs. 相似文献
998.
999.
When three-dimensional optical topometry of technical surfaces is performed, one major problem is that often the local reflectance of the object's surface varies within a wide range. This leads to overexposed and underexposed areas on the detector, where no measurements can be made. To overcome this problem, we have developed a method that extends the dynamic range of an imaging system. As an example we implemented this method to a measurement system that is based on fringe projection with a data projector and a color CCD camera. By projection of quasi-monochromatic fringes a different dynamic range in each of the three color channels of the camera is achieved. Hence the overall dynamic range of the system is increased by a factor larger than 5. 相似文献
1000.
Raska CS Parker CE Dominski Z Marzluff WF Glish GL Pope RM Borchers CH 《Analytical chemistry》2002,74(14):3429-3433
Immobilized metal ion affinity chromatography (IMAC) is a useful method to selectively isolate and enrich phosphopeptides from a peptide mixture. Mass spectrometry is a very suitable method for exact molecular weight determination of IMAC-isolated phosphopeptides, due to its inherent high sensitivity. Even exact molecular weight determination, however, is not sufficient for identification of the phosphorylation site if more than one potential phosphorylation site is present on a peptide. The previous method of choice for sequencing the affinity-bound peptides was electrospray tandem mass spectrometry (ESI-MS/MS). This method required elution and salt removal prior to MS analysis of the peptides, which can lead to sample loss. Using a matrix-assisted laser desorption/ionization (MALDI) source coupled to an orthogonal injection quadrupole time-of-flight (QqTOF) mass spectrometer with true MS/MS capabilities, direct sequencing of IMAC-enriched peptides has been performed on IMAC beads applied directly to the MALDI target. The utility of this new method has been demonstrated on a protein with unknown phosphorylation sites, where direct MALDI-MS/MS of the tryptic peptides bound to the IMAC beads resulted in the identification of two novel phosphopeptides. Using this technique, the phosphorylation site determination is unambiguous, even with a peptide containing four potentially phosphorylated residues. Direct analysis of phosphorylated peptides on IMAC beads does not adversely affect the high-mass accuracy of an orthogonal injection QqTOF mass spectrometer, making it a suitable technique for phosphoproteomics. 相似文献