全文获取类型
收费全文 | 5875篇 |
免费 | 264篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 53篇 |
综合类 | 7篇 |
化学工业 | 1217篇 |
金属工艺 | 93篇 |
机械仪表 | 135篇 |
建筑科学 | 207篇 |
矿业工程 | 15篇 |
能源动力 | 89篇 |
轻工业 | 563篇 |
水利工程 | 39篇 |
石油天然气 | 5篇 |
无线电 | 410篇 |
一般工业技术 | 984篇 |
冶金工业 | 1530篇 |
原子能技术 | 22篇 |
自动化技术 | 780篇 |
出版年
2023年 | 47篇 |
2022年 | 101篇 |
2021年 | 151篇 |
2020年 | 106篇 |
2019年 | 76篇 |
2018年 | 197篇 |
2017年 | 181篇 |
2016年 | 182篇 |
2015年 | 150篇 |
2014年 | 169篇 |
2013年 | 401篇 |
2012年 | 344篇 |
2011年 | 331篇 |
2010年 | 236篇 |
2009年 | 186篇 |
2008年 | 267篇 |
2007年 | 215篇 |
2006年 | 194篇 |
2005年 | 156篇 |
2004年 | 119篇 |
2003年 | 112篇 |
2002年 | 97篇 |
2001年 | 80篇 |
2000年 | 90篇 |
1999年 | 94篇 |
1998年 | 501篇 |
1997年 | 285篇 |
1996年 | 192篇 |
1995年 | 107篇 |
1994年 | 95篇 |
1993年 | 105篇 |
1992年 | 24篇 |
1991年 | 40篇 |
1990年 | 22篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 18篇 |
1985年 | 34篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 30篇 |
1981年 | 35篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 49篇 |
1976年 | 42篇 |
1975年 | 18篇 |
1973年 | 12篇 |
排序方式: 共有6149条查询结果,搜索用时 15 毫秒
141.
Jonathan Weber Sébastien Lefèvre 《Journal of Visual Communication and Image Representation》2013,24(3):397-409
Quasi-flat zones are morphological operators which segment the image into homogeneous regions according to certain criteria. They are used as an image simplification tool or an image segmentation pre-processing, but they induced a very important oversegmentation. Several filtering methods have been proposed to deal with this issue but they suffer from different drawbacks, e.g., loss of quality or edge deformation. In this article, we propose a new method based on existing approaches which achieves better or similar results than existing approaches, does not suffer from their drawbacks and requires less computation time. It consists of two successive steps. First, small quasi-flat zones are removed according to a minimal area threshold. They are then filled through the growth of remaining zones. 相似文献
142.
Conjugated copolymers are important materials for organic light-emitting diodes. Here, an investigation of the photophysical and charge-transporting properties of the prototypical poly(p-phenylene vinylene) based copolymer SuperYellow (SY) is reported. The study also investigated the effect of processing conditions by comparing the properties of spin-coated and solution-cast films. For both types of films, the results of time-resolved fluorescence and photoluminescence quantum yield measurements are similar. The high photoluminescence quantum yield of 60% and its independence of processing conditions shows the effectiveness of the bulky side groups in preventing concentration quenching of fluorescence. Time of flight measurements of charge mobility in both spin-coated and solution-cast films also showed similar results, with mobilities in the range 10?6–10?7 cm2/V s for both films. These results provide important information about a widely used copolymer and show that a good polymer light-emitting diode material can have low mobility. 相似文献
143.
On‐Demand Wrinkling Patterns in Thin Metal Films Generated from Self‐Assembling Liquid Crystals 下载免费PDF全文
Laurens T. de Haan Philippe Leclère Pascal Damman Albertus P. H. J. Schenning Michael G. Debije 《Advanced functional materials》2015,25(9):1360-1365
In this work, a new, universal method is described that uses the photopatterning of liquid crystals, which is accurately translated into a controlled, intricately wrinkled metal surface. Remarkably, the patterns have an oscillation in amplitude of the wrinkles. This rapid method allows generation of intricate multidomain patterns and continuous circular structures, including azimuthal, radial, and even higher complexity arrangements as examples. These wrinkled gold surfaces are also strikingly visual, which is interesting for applications ranging from diffractive elements to fine jewelry. 相似文献
144.
Soham Saha Benjamin T. Diroll Joshua Shank Zhaxylyk Kudyshev Aveek Dutta Sarah Nahar Chowdhury Ting Shan Luk Salvatore Campione Richard D. Schaller Vladimir M. Shalaev Alexandra Boltasseva Michael G. Wood 《Advanced functional materials》2020,30(7)
Transparent conducting oxides, such as doped indium oxide, zinc oxide, and cadmium oxide (CdO), have recently attracted attention as tailorable materials for applications in nanophotonic and plasmonic devices such as low‐loss modulators and all‐optical switches due to their tunable optical properties, fast optical response, and low losses. In this work, optically induced extraordinarily large reflection changes (up to 135%) are demonstrated in bulk CdO films in the mid‐infrared wavelength range close to the epsilon near zero (ENZ) point. To develop a better understanding of how doping level affects the static and dynamic optical properties of CdO, the evolution of the optical properties with yttrium (Y) doping is investigated. An increase in the metallicity and a blueshift of the ENZ point with increasing Y‐concentrations is observed. Broadband all‐optical switching from near‐infrared to mid‐infrared wavelengths is demonstrated. The major photoexcited carrier relaxation mechanisms in CdO are identified and it is shown that the relaxation times can be significantly reduced by increasing the dopant concentration in the film. This work could pave the way to practical dynamic and passive optical and plasmonic devices with doped CdO spanning wavelengths from the ultraviolet to the mid‐infrared region. 相似文献
145.
This article introduces a high-level system using belief functions for exchanging and managing imperfect information about events on the road in vehicular ad hoc networks. The main purpose of this application is to provide the most reliable information for the driver from multiple messages received informing the driver about events on the roads. This system and some variants are tested using a MATLAB? simulator. An implementation with Android smartphones using a Bluetooth technology to exchange the messages is also introduced. 相似文献
146.
P. N. Brunkov A. R. Kovsh V. M. Ustinov Yu. G. Musikhin N. N. Ledentsov S. G. Konnikov A. Polimeni A. Patanè P. C. Main L. Eaves C. M. A. Kapteyn 《Journal of Electronic Materials》1999,28(5):486-490
Capacitance- and conductance-voltage studies have been carried out on Schottky barrier structures containing a sheet of self-organized
InAs quantum dots. The dots are formed in GaAs n-type matrices after the deposition of four monolayers of InAs. Quasi-static
analysis of capacitance-voltage measurements indicates that there are at least two filled electron levels in the quantum dots,
located 60 and 140 meV below the GaAs conduction band edge. The conductance of the structure depends on the balance between
measurement frequency and the thermionic emission rate of carriers from the quantum dots. An investigation of the temperature-dependent
conductance at different frequencies as a function of the reverse bias allows us to study separately the electron emission
rates from the ground and first excited levels in the quantum dots. We estimate that the electron escape times from both levels
of the quantum dots become comparable at room temperature and equal to about 100 ps. 相似文献
147.
Antonio Sánchez‐Díaz Marta Izquierdo Salvatore Filippone Nazario Martin Emilio Palomares 《Advanced functional materials》2010,20(16):2695-2700
Organic solar cells made using a blend of DPM12 and P3HT are studied. The results show that higher Voc can be obtained when using DPM12 in comparison to the usual mono‐substituted PCBM electron acceptor. Moreover, better device performances are also registered when the cells are irradiated with sun‐simulated light of 10–50 mW cm?2 intensity. Electrochemical and time‐resolved spectroscopic measurements are compared for both devices and a 100‐mV shift in the density of states (DOS) is observed for DPM12/P3HT devices with respect to PCBM/P3HT solar cells and slow polaron‐recombination dynamics are found for the DPM12/P3HT devices. These observations can be directly correlated with the observed increase in Voc, which is in contrast with previous results that correlated the higher Voc with different ideality factors obtained using dark‐diode measurements. The origin for the shift in the DOS can be correlated to the crystallinity of the blend that is influenced by the properties of the included fullerene. 相似文献
148.
The photolabile and phototoxic fluoroquinolone (FQ) antibacterial drugs norfloxacin and rufloxacin have been used as capping agents for 25 nm Ag nanoparticles, exploiting the noncovalent interaction between the cationic piperazinyl ring of both FQs and the negatively charged metal surface. The resulting FQ‐protected silver nanoclusters (Ag@FQs), ca. 80 nm in diameter, are dispersible in phosphate buffer at physiological pH and their response to light excitation has been studied by steady‐state and time‐resolved spectroscopic and photochemical techniques. The fluorescence emission of the FQs chromophores is not extensively quenched in the Ag@FQs. In contrast, both Ag@FQs exhibit a photochemical stability more than one order of magnitude larger than that of the free drugs. This is the result of significant and differentiated quenching effects by the Ag surface on the kinetic and population of the excited triplet states of FQs, which are the key intermediate in the drugs photodecomposition. In view of the well‐known antimicrobial properties of the Ag nanoparticles, the Ag@FQs could represent intriguing nanohybrids in the perspective multifunctional nanodrugs. 相似文献
149.
Ghiasi Gita Beaudry Catherine Larivière Vincent St-Pierre Carl Schiffauerova Andrea Harsh Matthew 《Scientometrics》2021,126(9):7937-7991
Scientometrics - Gender equality is one of the primary dimensions of responsible research and innovation. Based on bibliometric and survey data of nanotechnology researchers in Canada, this paper... 相似文献
150.
The electropolymerization of a flavin reductase-amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provides the efficient entrapment of the enzyme in a functionalized polypyrrole film. The enzyme film was characterized and applied to the detection of several flavins and pyridine nucleotides. The response of the bioelectrode was based on the amperometric oxidation, at -0.1 V vs SCE, of the enzymically generated dihydroflavins in the presence of reduced pyridine nucleotides. The highest sensitivities and detection limits were 668 mA M(-1) cm(-2) and 4 nM for riboflavin, 179 mA M(-1) cm(-2) and 20 nM for flavin mononucleotide, and 107 mA M(-1) cm(-2) and 40 nM for flavin adenine dinucleotide. Direct electrochemical measurements at -0.65 V and electroenzymatic measurements at -0.1 V of riboflavin, carried out with these bioelectrodes, show that an amplification phenomenon occurs, due to an electrochemical recycling reaction of enzyme substrate. A nonamplified response to reduced pyridine nucleotides was also obtained in the presence of 0.1 mM riboflavin. The sensitivity and detection limit of the bioelectrode are 19.6 mA M(-1) cm(-2) and 0.2 μM for NADH and 11.2 mA M(-1) cm(-2) and 0.5 μM for NADPH. 相似文献