全文获取类型
收费全文 | 403篇 |
免费 | 27篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 148篇 |
金属工艺 | 1篇 |
机械仪表 | 5篇 |
建筑科学 | 14篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 48篇 |
水利工程 | 8篇 |
石油天然气 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 78篇 |
冶金工业 | 52篇 |
原子能技术 | 1篇 |
自动化技术 | 38篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 21篇 |
2017年 | 11篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 18篇 |
2012年 | 26篇 |
2011年 | 24篇 |
2010年 | 22篇 |
2009年 | 24篇 |
2008年 | 25篇 |
2007年 | 19篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1963年 | 2篇 |
1961年 | 1篇 |
1960年 | 3篇 |
排序方式: 共有430条查询结果,搜索用时 31 毫秒
101.
Maya Gussmann Kaare Græsbøll Nils Toft Søren S. Nielsen Michael Farre Carsten Kirkeby Tariq Halasa 《Journal of dairy science》2018,101(1):505-517
Societal pressure to limit the use of antibiotics in livestock production systems, including dairy cattle systems, is consistently increasing. To motivate farmers to reduce antibiotic usage, it is important to understand the factors that determine whether a cow will be treated with antibiotics or not. If farmers' usual practices regarding antibiotic treatments are taken into account, they may be motivated to adopt control measures that can facilitate prudent use of antibiotics and are at the same time cost-effective. In this study, we analyzed database recordings of milk yield and somatic cell count from the routine milk recording scheme, clinical registrations of mastitis and PCR results, and cow factors such as days in milk and parity in relation to antibiotic treatments for 518 dairy herds in Denmark. Farm-wise logistic regressions were used to predict antimicrobial treatment based on these factors. The resulting regression coefficients of 422 herds were further analyzed by principal component analysis and clustering to determine the driving predictors for treatment in different groups of farms. The results showed that determinants that were most important for predicting antibiotic treatments vary from one farm to another. Health indicators such as PCR or somatic cell count were most indicative for treatment on some farms, whereas other groups seemed to depend more on production factors (milk yield) or later culling of the cows. This shows that farmers behave differently and differences can be identified in register data. This information can be considered when developing cost-effective herd-specific control measures of mastitis to promote prudent use of antibiotics in Danish dairy cattle farms. 相似文献
102.
We draw on cognitive and behavioural theories and on the artificial intelligence literature in order to propose a framework of future operator – workstation interaction in the ‘Industry 4.0’ era. We name the proposed framework ‘Operator – Workstation Interaction 4.0’. The latter’s capabilities permit an adaptive, ongoing interaction that aims to improve operator safety, performance, well-being, and satisfaction as well as the factory’s production measures. The framework is composed of three subsystems: (1) the observation subsystem which observes the operator and the processes occurring in the workstation, (2) the analysis subsystem which generates understanding and implications of the observations output, (3) the reaction subsystem which determines if and how to respond. The paper describes these elements and illustrate them using an example of a fatigued worker. The contributions, implications, and limitations of the proposed framework are discussed, and future research directions are presented. 相似文献
103.
Eva M. Maya 《Polymer》2005,46(25):11247-11254
Three new aromatic polyimides containing one or two replaceable halogen atoms in the repeat unit have been prepared by one-pot polycondensation at high temperature from dianhydrides and diamines containing halogen atoms. The halogenated polyimides exhibited good thermal properties and great solubility in a wide range of organic solvents, which make them good candidates to prepare functional polymers. They also showed film-forming capabilities, good mechanical properties, and a very low ability to take water, with values of only around 1% water uptake. To show the usefulness of these polyimides as functional polymers, the halogen group of two of them was successfully replaced by 4-tert-butyl phenyl or 4-tert-butyl phenyl ethynyl groups by a Suzuki or a Sonogashira reaction, respectively. 相似文献
104.
We review our experience with the construction of models of subsurface fracturing in geothermal fields by the inversion of shear-wave splitting (SWS) observations from natural and induced seismic events recorded by local arrays of three-component digital seismometers. SWS is a phenomenon whereby shear seismic waves split into two as a result of the mechanical anisotropy created in an otherwise isotropic rock by aligned micro-fractures. The two split waves travel at different speeds, and the polarization of the faster wave is usually parallel to crack orientation. The time delay between the two split S-waves is proportional to the number of cracks per unit volume.Success in the inversion of SWS data hinges on the assumption that the observed SWS is due solely to the mechanical anisotropy induced by aligned cracks and micro-cracks in an otherwise isotropic matrix. The presence of lithologic anisotropy and/or strong heterogeneity in the reservoir rock limits the resolvability of the method. However, despite the large amount of data and diversity of geologic settings we have studied so far, the above assumption has been found to be reliable. In practice, stability and resolution in the inversion of SWS data are the issues of utmost importance since both are critically dependent on the distribution of the two SWS measured parameters (polarization and time delay) around each seismic sensor.In this paper we discuss a few lessons we have learned as to the value of SWS for geothermal exploration, its limitations and potential extensions, from nearly a decade of practice. 相似文献
105.
M. Guncheva D. Zhiryakova N. Radchenkova M. Kambourova 《Journal of the American Oil Chemists' Society》2008,85(2):129-132
The catalytic efficiency of a lipase from Bacillus stearothermophilus MC7 (lipase MC7) was evaluated in acidolysis of tripalmitin with oleic acid to yield dioleoylpalmitoylglycerol, a structured
triglyceride used in health food. The immobilized enzyme exhibits good operational thermostability with a half-life of 50 days
at 60 °C in a solvent-free system. The degree of conversion exceeded 50% after 48 h. The side reaction of hydrolysis was suppressed.
However, the monosubstituted product was prevalent in the product mixture. Tested in a broad range of solvents, lipase MC7
showed tolerance towards medium polarity. 相似文献
106.
Alexander G. Volkov Maya I. Volkova-Gugeshashvili Albert J. Osei 《Electrochimica acta》2007,52(8):2905-2912
Electrochemical multielectron reactions in photosynthesis and respiration are evaluated by thermodynamic and kinetic analysis. Kharkats and Volkov [Yu.I. Kharkats, A.G. Volkov, Biochim. Biophys. Acta 891 (1987) 56] were the first to present proof that cytochrome c oxidase reduces molecular oxygen by synchronous multielectron mechanism without O2− intermediate formation. After this pioneering observation, it became clear that the first step of oxygen reduction is two-electron concerted process. The energy for the H+-pump of cytochrome oxidase is liberated when the third and fourth electrons are added in the last two steps of water formation independent of the reaction pathway. Electrochemical principles govern many biological properties of organisms, such as the generation of electric fields, and the conduction of fast excitation waves. These properties are supported by the function of a variety of natural nanodevices. Ionic channels, as natural nanodevices, control the plasma membrane potential, and the movement of ions across membranes; thereby, regulating various biological functions. Some voltage-gated ion channels work as plasma membrane nanopotentiostats. In plants, excitation waves are possible mechanisms for intercellular and intracellular communication in response to environmental changes. The role of electrified nanointerface of the plasma membrane in signal transduction is discussed as well. 相似文献
107.
Abstract
We study the numerical approximation of solutions for parabolic integro-differential equations (PIDE). Similar models arise
in option pricing, to generalize the Black–Scholes equation, when the processes which generate the underlying stock returns
may contain both a continuous part and jumps. Due to the non-local nature of the integral term, unconditionally stable implicit
difference schemes are not practically feasible. Here we propose using implicit-explicit (IMEX) Runge-Kutta methods for the
time integration to solve the integral term explicitly, giving higher-order accuracy schemes under weak stability time-step
restrictions. Numerical tests are presented to show the computational efficiency of the approximation.
Mathematics Subject Classification (1991): Primary: 65M12; Secondary: 35K55, 49L25 相似文献
108.
Maya Gadzheva 《Information & Communications Technology Law》2007,16(3):217-231
Human Radio Frequency Identification (RFID) implants are currently being marketed as a way to limit access to secure areas or as anti-kidnapping devices, as well as means to track and quickly identify in emergency situations individuals with serious medical conditions or mental disabilities or to serve as cashless payment devices with a wave of the hand. While in certain instances, such as in some medical applications, this technology can have positive and benign effects there are also serious privacy implications. Although at present, technological and financial challenges prevent the wide take-up of these highly controversial devices, privacy advocates fear the technology might be abused by governments and big corporations and used to constantly locate and profile people. A detailed critique of the complex privacy, security, ethical and health implications in the light of this emerging technology is still lacking and this article attempts to contribute to this process. 相似文献
109.
We consider the problem of document binarization as a pre-processing step for optical character recognition (OCR) for the purpose of keyword search of historical printed documents. A number of promising techniques from the literature for binarization, pre-filtering, and post-binarization denoising were implemented along with newly developed methods for binarization: an error diffusion binarization, a multiresolutional version of Otsu's binarization, and denoising by despeckling. The OCR in the ABBYY FineReader 7.1 SDK is used as a black box metric to compare methods. Results for 12 pages from six newspapers of differing quality show that performance varies widely by image, but that the classic Otsu method and Otsu-based methods perform best on average. 相似文献
110.