全文获取类型
收费全文 | 2756篇 |
免费 | 167篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 32篇 |
综合类 | 5篇 |
化学工业 | 781篇 |
金属工艺 | 38篇 |
机械仪表 | 49篇 |
建筑科学 | 115篇 |
矿业工程 | 10篇 |
能源动力 | 105篇 |
轻工业 | 200篇 |
水利工程 | 29篇 |
石油天然气 | 5篇 |
无线电 | 244篇 |
一般工业技术 | 497篇 |
冶金工业 | 194篇 |
原子能技术 | 9篇 |
自动化技术 | 613篇 |
出版年
2024年 | 4篇 |
2023年 | 43篇 |
2022年 | 141篇 |
2021年 | 136篇 |
2020年 | 81篇 |
2019年 | 83篇 |
2018年 | 102篇 |
2017年 | 84篇 |
2016年 | 105篇 |
2015年 | 89篇 |
2014年 | 118篇 |
2013年 | 195篇 |
2012年 | 146篇 |
2011年 | 228篇 |
2010年 | 144篇 |
2009年 | 143篇 |
2008年 | 175篇 |
2007年 | 125篇 |
2006年 | 111篇 |
2005年 | 75篇 |
2004年 | 56篇 |
2003年 | 62篇 |
2002年 | 43篇 |
2001年 | 31篇 |
2000年 | 35篇 |
1999年 | 30篇 |
1998年 | 55篇 |
1997年 | 56篇 |
1996年 | 38篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有2926条查询结果,搜索用时 15 毫秒
991.
We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong transverse electric field in the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed. 相似文献
992.
993.
Vincenzo Amendola Stefano Scaramuzza Lucio Litti Moreno Meneghetti Gaia Zuccolotto Antonio Rosato Elena Nicolato Pasquina Marzola Giulio Fracasso Cristina Anselmi Marcella Pinto Marco Colombatti 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(12):2476-2486
Diagnostic approaches based on multimodal imaging are needed for accurate selection of the therapeutic regimens in several diseases, although the dose of administered contrast drugs must be reduced to minimize side effects. Therefore, large efforts are deployed in the development of multimodal contrast agents (MCAs) that permit the complementary visualization of the same diseased area with different sensitivity and different spatial resolution by applying multiple diagnostic techniques. Ideally, MCAs should also allow imaging of diseased tissues with high spatial resolution during surgical interventions. Here a new system based on multifunctional Au‐Fe alloy nanoparticles designed to satisfy the main requirements of an ideal MCA is reported and their biocompatibility and imaging capability are described. The MCAs show easy and versatile surface conjugation with thiolated molecules, magnetic resonance imaging (MRI) and computed X‐ray tomography (CT) signals for anatomical and physiological information (i.e., diagnostic and prognostic imaging), large Raman signals amplified by surface enhanced Raman scattering (SERS) for high sensitivity and high resolution intrasurgical imaging, biocompatibility, exploitability for in vivo use and capability of selective accumulation in tumors by enhanced permeability and retention effect. Taken together, these results show that Au‐Fe nanoalloys are excellent candidates as multimodal MRI‐CT‐SERS imaging agents. 相似文献
994.
Simona D’Oca Valentina Fabi Stefano P. Corgnati Rune Korsholm Andersen 《Building Simulation》2014,7(6):683-694
Existing dynamic energy simulation tools exceed the static dimension of the simplified methods through a better and more accurate prediction of energy use; however, their ability to predict real energy consumption is undermined by a weak representation of human interactions with the control of the indoor environment. The traditional approach to building dynamic simulation considers energy consumption as fully deterministic, taking into account standardized input parameters and using fixed and unrealistic schedules (lighting level, occupancy, ventilation rate, thermostat set-point). In contrast, in everyday practice occupants interact with the building plant system and building envelope in order to achieve desired indoor environmental conditions. In this study, occupant behavior in residential building was modelled accordingly to a probabilistic approach. A new methodology was developed to combine probabilistic user profiles for both window opening and thermostat set-point adjustments into one building energy model implemented in the dynamic simulation tool IDA Ice. The aim of the study was to compare mean values of the probabilistic distribution of the obtained results with a singular heating energy consumption value obtained by means of standard deterministic simulations. Major findings of this research demonstrated the weakness of standardized occupant behavior profile in energy simulation tools and the strengths of energy models based on measurements in fields and probabilistic modelling providing scenarios of occupant behavior in buildings. 相似文献
995.
Management practices and forage quality affecting the contamination of milk with anaerobic spore‐forming bacteria
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
996.
Sanjeewa R. Karunathilaka Betsy Jean Yakes Samantha Farris Tara Jade Michael Keqin He Jin Kyu Chung Romina Shah Magdi M. Mossoba 《Food Analytical Methods》2018,11(4):969-979
Rapid, direct, and reagent-free screening tools using vibrational spectroscopy in combination with partial least squares regression (PLSR) were developed for the determination of sodium saccharin and sodium cyclamate in tabletop formulations. The four vibrational spectroscopic instruments employed were a portable Raman spectrometer, a NIR handheld device, and two FT-NIR benchtop spectrometers. Wavenumber ranges and type of spectral pretreatment were optimized for each PLSR calibration model using an independent validation set. Each sweetener model provided reliable predictions (low errors in validation and r 2 above 0.90) for both saccharin and cyclamate samples. Optimized models were tested with four commercially available tabletop formulations in order to simulate the application of the developed models towards routine sweetener analysis. With the exception of one model, the sweetener concentration predictions in commercial tabletop formulations using the portable devices were not significantly different from those based on spectra collected on the benchtop spectrometers. PLSR-predicted mean sweetener concentrations were within 80–120% of the label declared values, while the sweetener without a label declaration had consistent concentrations across the analytical methods used. As shown by the good agreement between spectroscopic and chromatographic analyses, the portable spectrometers offer an alternative to traditional chromatographic methods. To our knowledge, this is the first time portable Raman and handheld NIR devices with PLSR calibration models have been employed to evaluate sweeteners, and these analytical methods hold potential to be used for rapid screening of tabletop formulations for quality assurance and for regulatory labeling verification. 相似文献
997.
Agnieszka Kapa?ka Stéphane Fierro Zacharias Frontistis Alexandros Katsaounis Stefano Neodo Olivier Frey Nico de Rooij Kai M. Udert Christos Comninellis 《Electrochimica acta》2011,56(3):1361
The electrochemical oxidation of ammonia (NH4+/NH3) in sodium perchlorate was investigated on IrO2 electrodes prepared by two techniques: the thermal decomposition of H2IrCl6 precursor and the anodic oxidation of metallic iridium. The electrochemical behaviour of Ir(IV)/Ir(III) surface redox couple differs between the electrodes indicating that on the anodic iridium oxide film (AIROF) both, the surface and the interior of the electrode are electrochemically active whereas on the thermally decomposed iridium oxide films (TDIROF), mainly the electrode surface participates in the electrochemical processes.On both electrodes, ammonia is oxidized in the potential region of Ir(V)/Ir(IV) surface redox couple activity, thus, may involve Ir(V). During ammonia oxidation, TDIROF is deactivated, probably by adsorbed products of ammonia oxidation. To regenerate TDIROF, it is necessary to polarize the electrode in the hydrogen evolution region. On the contrary, AIROF seems not to be blocked during ammonia oxidation indicating its fast regeneration during the potential scan. The difference between both electrodes results from the difference in the activity of the iridium oxide surface redox couples. 相似文献
998.
999.
1000.
Tianyu Li Stefano Menegatti Nathan Crook 《American Institute of Chemical Engineers》2023,69(12):e18228
Poly(ethylene terephthalate) (PET) is a highly recyclable plastic that has been extensively used and manufactured. Like other plastics, PET resists natural degradation, thus accumulating in the environment. Several recycling strategies have been applied to PET, but these tend to result in downcycled products that eventually end up in landfills. This accumulation of landfilled PET waste contributes to the formation of microplastics, which pose a serious threat to marine life and ecosystems, and potentially to human health. To address this issue, our project leveraged synthetic biology to develop a whole-cell biocatalyst capable of depolymerizing PET in seawater environments by using the fast-growing, nonpathogenic, moderate halophile Vibrio natriegens. By leveraging a two-enzyme system—comprising a chimera of IsPETase and IsMHETase from Ideonella sakaiensis—displayed on V. natriegens, we constructed whole-cell catalysts that depolymerize PET and convert it into its monomers in salt-containing media and at a temperature of 30°C. 相似文献