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排序方式: 共有768条查询结果,搜索用时 15 毫秒
1.
Joshua C. Price Simon J. Levett Valentin Radu David A. Simpson Aina Mogas Barcons Christopher F. Adams Melissa L. Mather 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits. 相似文献
2.
Lázaro Valentin Zuquette Janaina Barrios Palma Osni José Pejon 《Bulletin of Engineering Geology and the Environment》2005,64(3):257-271
There are more than 20,000 uncontrolled sanitary landfill areas in Brazil. The paper reports an integrated study undertaken
to develop an environmental assessment of the uncontrolled sanitary landfill area of the city of Po?os de Caldas, State of
Minas Gerais, Brazil. A number of remedial alternatives were evaluated. The USGS modular 3D finite difference groundwater
flow model (Modflow) and Modular 3D Finite Difference Mass Transport Model (MT3D) software were used to simulate groundwater
flow and contaminant transport modelling, as well as to predict changes due to the proposed remediation measures. The remedial
alternatives considered for normal conditions from 20 to 40 year periods were waste removal, vertical cut-off barriers, extraction
wells and top capping. The results indicated that extraction wells and waste removal are the best alternatives because they
significantly reduce both the extension and levels of the contamination plume even after 5 years. The extraction well proved
a less expensive remedial alternative than waste removal.
相似文献
3.
Magnetic Flux Controllers for Induction Heating Applications 总被引:3,自引:0,他引:3
ValentinNemkov RobertGoldstein RobertRuffini 《材料热处理学报》2004,25(5):567-572
Application of magnetic flux controllers/concentrators to induction heating coils can drastically improve the process efficiency and heat pattern control. Presentation includes: benefits provided by flux controllers, materials available for controllers, application techniques, computer assisted design of induction coils with concentrators, examples of applications. Depending on induction system design, magnetic flux controllers can concentrate heating in a specified area,change heat source distribution and shield a particular part zone or external area preventing unintended eddy current heating.Besides of the coil efficiency improvement and optimal power distribution, magnetic flux controllers reduce the coil current demand from a supplying circuitry thus strongly reducing losses in busswork, cables, transformers and inverter components.Improvement that can be achieved due to magnetic flux controllers is case dependable. 2D and 3D computer simulation allows the designer to predict accurately effect of controllers on the coil parameters and temperature distribution and optimize the whole electromagnetic system. Special attention in presentation is paid to new magnetodielectric materials optimized for induction heating conditions. These materials have high magnetic permeability and saturation flux density,excellent machinability, good chemical and temperature resistance. Concentrators from these materials can work in a wide range of frequencies and specific powers. Examples of magnetic flux controller application include surface hardening of shafts and gears, induction surface hardfacing and brazing. 相似文献
4.
Valentin I. Gibalov 《臭氧:科学与工程》2006,28(2):119-124
The parameters, which determine the performance of ozone generators, are efficiency and maximum ozone concentration. The efficiency from oxygen has been found to be nearly independent on the kind of barrier discharge arrangement (volume, surface, coplanar), while the ozone concentration saturation level depends on the specific design of the generator. These phenomena are explained with features of the discharge process and the properties of chemical reactions, respectively. The importance of a limit in the energy density of the discharge is highlighted. 相似文献
5.
Electrochemical ferrate generation for waste water treatment using cast irons with high silicon contents 总被引:5,自引:0,他引:5
This paper deals with the electrochemical preparation of ferrate in 15 M NaOH media, with a view to treatment of waste waters. Grey cast irons with high silicon contents were shown to allow current yields in the range 20–40% depending on the applied current density, up to 34 mA cm–2. Ferrate solutions with contents up to 0.08 M could be produced in a divided cell of simple design, and provided with flat or packed-bed electrodes. Deactivation of the anode surface was shown to be of moderate significance for hour-long runs. The ferrate produced was tested for treatment of industrial liquid wastes: coagulation efficiency of the suspended matter was comparable with that of an electrocoagulation process with sacrificial Al anodes. The potential of waste water treatment by addition of ferrate is discussed. 相似文献
6.
Helmut Alt Esther M. Arkin Alon Efrat George Hart Ferran Hurtado Irina Kostitsyna Alexander Kröller Joseph S. B. Mitchell Valentin Polishchuk 《Theory of Computing Systems》2014,54(4):689-714
We show how to compute the smallest rectangle that can enclose any polygon, from a given set of polygons, in nearly linear time; we also present a PTAS for the problem, as well as a linear-time algorithm for the case when the polygons are rectangles themselves. We prove that finding a smallest convex polygon that encloses any of the given polygons is NP-hard, and give a PTAS for minimizing the perimeter of the convex enclosure. We also give efficient algorithms to find the smallest rectangle simultaneously enclosing a given pair of convex polygons. 相似文献
7.
Valentin G. Greb Martin Bertau Axel Düker Andreas Geisbauer Peter Fröhlich 《化学,工程师,技术》2021,93(11):1827-1832
Petrochemical catalysts are widely used in the industry. For the production of cumene, zeolite-based catalysts containing phosphoric acid are applied. Over the time, coking deactivates the surface, and the catalyst has to be exchanged and disposed of. Different process approaches for recycling the phosphoric acid-containing catalysts were investigated. Related preliminary investigations have shown that calcination of the used catalyst is necessary prior to reprocessing. By digesting the catalyst with hydrofluoric acid, ∼96 % phosphate was recovered. However, this process is very costly in terms of process technology. More promising is digestion by basic or acidic routes. Several options are possible here, and digestion with H3PO4 proved to be particularly suitable. Here, phosphate yields reached up to 98.8 %, with a positive balance of economic efficiency at the same time. The catalyst can be produced and recycled in the same plant with the same reagents, what constitutes a major breakthrough towards sustainability in industrial catalysis. 相似文献
8.
Valentin Hamon 《Journal in Computer Virology》2013,9(2):65-76
Nowadays, PDF (Portable Document Format) is used very frequently, especially by companies and even more and more by normal users. This can be a good explanation of the rising appeal of cybercriminals for this vector of attack. PDF is also often considered as safer as other document formats like those of Microsoft Office for example. Knowing the many possibilities offered by this format, we can wonder about the question of the confidence which should be given to such a document. Indeed, the use of HTTP(Hypertext Transfert Protocol) requests allows us to execute some arbitrary code outside of the PDF. Including, for example, JavaScript in Internet Explorer. It sill works, despite the updates from Adobe, this is still a pretty good open door to malicious actions. Basically, the purpose of this paper is to show that the simple use of an HTTP request from a PDF can be a pretty good vector for an attacker. Furthermore, this paper deals about how it can be relatively easy to reuse some vulnerabilities from outside the document. In addition, we will see that it’s possible to call an external PDF from another PDF. In fact, it can allow the attacker to adapt his attack by knowing the Adobe software version of the victim even before launching any malicious PDF. Knowledge of this security problem is not new but this article aims to show in detail how the attacker could place his attack. 相似文献
9.
The documented data regarding the three-dimensional structure of the air capillaries (ACs), the ultimate sites of gas exchange in the avian lung is contradictory. Further, the mode of gas exchange, described as cross-current has not been clearly elucidated. We studied the temporal and spatial arrangement of the terminal air conduits of the chicken lung and their relationship with the blood capillaries (BCs) in embryos as well as the definitive architecture in adults. Several visualization techniques that included corrosion casting, light microscopy as well as scanning and transmission electron microscopy were used. Two to six infundibulae extend from each atrium and give rise to numerous ACs that spread centrifugally. Majority of the ACs are tubular structures that give off branches, which anastomose with their neighboring cognates. Some ACs have globular shapes and a few are blind-ending tapering tubes. During inauguration, the luminal aspects of the ACs are characterized by numerous microvillus-like microplicae, which are formed during the complex processes of cell attenuation and canalization of the ACs. The parabronchial exchange BCs, initially inaugurated as disorganized meshworks, are reoriented via pillar formation to lie predominantly orthogonal to the long axes of the ACs. The remodeling of the retiform meshworks by intussusceptive angiogenesis essentially accomplishes a cross-current system at the gas exchange interface in the adults, where BCs form ring-like patterns around the ACs, thus establishing a cross-current system. Our findings clarify the mode of gas exchange in the parabronchial mantle and illuminate the basis for the functional efficiency of the avian lung. 相似文献
10.
Baoju Li Zitao Wang Zhuangzhuang Gao Jinquan Suo Ming Xue Yushan Yan Valentin Valtchev Shilun Qiu Qianrong Fang 《Advanced functional materials》2023,33(16):2300219
Covalent organic frameworks (COFs) are proposed as promising candidates for engineering advanced molecular sieving membranes due to their precise pore sizes, modifiable pore environment, and superior stability. However, COFs are insoluble in common solvents and do not melt at high temperatures, which presents a great challenge for the fabrication of COF-based membranes (COFMs). Herein, for the first time, a new synthetic strategy is reported to prepare continuous and intact self-standing COFMs, including 2D N-COF membrane and 3D COF-300 membrane. Both COFMs show excellent selectivity of H2/CO2 mixed gas (13.8 for N-COF membrane and 11 for COF-300 membrane), and especially ultrahigh H2 permeance (4319 GPU for N-COF membrane and 5160 GPU for COF-300 membrane), which is superior to those of COFMs reported so far. It should be noted that the overall separation performance of self-standing COFMs exceeds the Robeson upper bound. Furthermore, a theoretical study based on Grand Canonical Monte Carlo (GCMC) simulation is performed to explain the excellent separation of H2/CO2 through COFMs. Thus, this facile preparation method will provide a broad prospect for the development of self-standing COFMs with highly efficient H2 purification. 相似文献