全文获取类型
收费全文 | 2408篇 |
免费 | 175篇 |
专业分类
电工技术 | 22篇 |
综合类 | 29篇 |
化学工业 | 974篇 |
金属工艺 | 25篇 |
机械仪表 | 42篇 |
建筑科学 | 104篇 |
矿业工程 | 6篇 |
能源动力 | 55篇 |
轻工业 | 387篇 |
水利工程 | 44篇 |
石油天然气 | 4篇 |
无线电 | 84篇 |
一般工业技术 | 377篇 |
冶金工业 | 124篇 |
原子能技术 | 7篇 |
自动化技术 | 299篇 |
出版年
2024年 | 16篇 |
2023年 | 29篇 |
2022年 | 180篇 |
2021年 | 179篇 |
2020年 | 99篇 |
2019年 | 87篇 |
2018年 | 91篇 |
2017年 | 97篇 |
2016年 | 114篇 |
2015年 | 95篇 |
2014年 | 125篇 |
2013年 | 172篇 |
2012年 | 142篇 |
2011年 | 204篇 |
2010年 | 119篇 |
2009年 | 117篇 |
2008年 | 126篇 |
2007年 | 97篇 |
2006年 | 70篇 |
2005年 | 49篇 |
2004年 | 46篇 |
2003年 | 49篇 |
2002年 | 41篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 28篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2583条查询结果,搜索用时 15 毫秒
21.
Workers in physically demanding occupations require work breaks to recover from exertion. In a laboratory setting, we investigated the impact of ergometer cycling for 7 h in two conditions with an identical total break time but with two different activity-rest schedules. We hypothesised that more frequent but shorter breaks lead to less psychophysical strain and its effects than do less frequent but longer breaks, particularly for older workers. Twenty-nine participants representing three different age groups were tested in both conditions. Heart rate, perceived exertion/tension and feelings of fatigue were assessed and used as dependent variables. Results indicate no general activity-rest differences as well as no age-related differences of break effects under the condition of subjectively equal straining load. However, heart rate was found to be lower at some measurement points in the frequent-short-break condition and perceived exertion was lower in the infrequent-long-break condition. PRACTITIONER SUMMARY: Design of activity-rest schedules in physically demanding occupations is a key issue in the prevention of strain and hence of interest to ergonomists. Our study suggests that breaks during physically demanding work have the same effect if they are frequent and short or infrequent and long, regardless of age. 相似文献
22.
Claudia Tarantola Paola Vicard Ioannis Ntzoufras 《Expert systems with applications》2012,39(11):10103-10111
Mystery shopping is a well known marketing technique used by companies and marketing analysts to measure quality of service, and gather information about products and services. In this article, we analyse data from mystery shopping surveys via Bayesian Networks in order to examine and evaluate the quality of service offered by the loan departments of Greek Banks. We use mystery shopping visits to collect information about loan products and services and, by this way, evaluate the customer satisfaction and plan improvement strategies that will assist banks to reach their internal standards. Bayesian Networks not only provide a pictorial representation of the dependence structure between the characteristics of interest but also allow to evaluate, interpret and understand the effects of possible improvement strategies. 相似文献
23.
John Clarke Claudia D. Tesche R. P. Giffard 《Journal of Low Temperature Physics》1979,37(3-4):405-420
We calculate the signal-to-noise ratio in a dc SQUID system as a function of source impedance, taking into account the effects of current and voltage noise sources in the SQUID. The optimization of both tuned and untuned voltmeters and magnetometers is discussed and typical sensitivities are predicted using calculated noise spectra. The calculations are based on an ideal symmetric dc SQUID with % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaHYoGycqGH9a% qpcaaIYaacbaGaa8htaiaa-LeadaWgaaWcbaacbiGaa4hmaaqabaGc% caGGVaGaeuOPdy0aaSbaaSqaaiaa+bdaaeqaaOGaeyypa0JaaGymaa% aa!3D23!\[\beta = 2LI_0 /\Phi _0 = 1\] and moderate noise rounding % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaaiiGacqWFOaakcq% WFtoWrcqWF9aqpcqWFYaGmcqaHapaCcaWGRbWaaSbaaSqaaiaadkea% aeqaaGqaaOGaa4hvaiaac+cacaGFjbWaaSbaaSqaaerbbjxAHXgaiu% GacaqFWaaabeaakiab-z6agnaaBaaaleaacaqGGaacbiGaaWhmaaqa% baGccqGH9aqpcaaIWaGaaiOlaiaaicdacaaI1aGaaiykaaaa!471A!\[(\Gamma = 2\pi k_B T/I_0 \Phi _{{\rm{ }}0} = 0.05)\], where 0 is the flux quantum, T is the temperature, L is the SQUID inductance, and I
0 is the critical current of each junction. The optimum noise temperatures of tuned and untuned voltmeters are found to be 2.8(L/R)T and 8(L/R)T (1 + 1.52 + 0.74)1/2/2 respectively, where /2 is the signal frequency, assumed to be much less than the Josephson frequency, and is the coupling coefficient between the SQUID and its input coil. It is found that tuned and untuned magnetometers can be characterized by optimum effective signal energies given by (16k
B
TLE/2
R)[1 + (1 + 1.52 + 0.72)1/2 + 0.752] and 2kB
T
iRiB/2
L
p respectively, where B is the bandwidth, R
i is the resistance representing the losses in the tuned circuit at temperature T
i and L
p is the inductance of the pickup coil.This work was supported by the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, and by the U.S. Office of Naval Research.Guggenheim Fellow. 相似文献
24.
There is an implicit assumption in electronic commerce that induces the buyers to believe that their deals will be handled appropriately. However, after a seller has already committed to a buyer, he may be tempted by several requests though he will not be able to supply them all. We analyze markets in which a finite set of automated buyers interacts repeatedly with a finite set of automated sellers. These sellers can satisfy one buyer at a time, and they can be tempted to break a commitment they already have. We have found the perfect equilibria that exist in markets with a finite horizon, and with an unrestricted horizon. A significant result stemming from our study reveals that sellers are almost always tempted to breach their commitments. However, we also show that if markets' designers implement an external mechanism that restricts the automated buyers actions, then sellers will keep their commitments. 相似文献
25.
Margherita Passariello Veronica Ferrucci Emanuele Sasso Lorenzo Manna Rosa Rapuano Lembo Stefano Pascarella Giovanna Fusco Nicola Zambrano Massimo Zollo Claudia De Lorenzo 《International journal of molecular sciences》2022,23(10)
The dramatic experience with SARS-CoV-2 has alerted the scientific community to be ready to face new epidemics/pandemics caused by new variants. Among the therapies against the pandemic SARS-CoV-2 virus, monoclonal Antibodies (mAbs) targeting the Spike glycoprotein have represented good drugs to interfere in the Spike/ Angiotensin Converting Enzyme-2 (ACE-2) interaction, preventing virus cell entry and subsequent infection, especially in patients with a defective immune system. We obtained, by an innovative phage display selection strategy, specific binders recognizing different epitopes of Spike. The novel human antibodies specifically bind to Spike-Receptor Binding Domain (RBD) in a nanomolar range and interfere in the interaction of Spike with the ACE-2 receptor. We report here that one of these mAbs, named D3, shows neutralizing activity for virus infection in cell cultures by different SARS-CoV-2 variants and retains the ability to recognize the Omicron-derived recombinant RBD differently from the antibodies Casirivimab or Imdevimab. Since anti-Spike mAbs, used individually, might be unable to block the virus cell entry especially in the case of resistant variants, we investigated the possibility to combine D3 with the antibody in clinical use Sotrovimab, and we found that they recognize distinct epitopes and show additive inhibitory effects on the interaction of Omicron-RBD with ACE-2 receptor. Thus, we propose to exploit these mAbs in combinatorial treatments to enhance their potential for both diagnostic and therapeutic applications in the current and future pandemic waves of coronavirus. 相似文献
26.
Jamie Afghani Claudia Traidl-Hoffmann Philippe Schmitt-Kopplin Matthias Reiger Constanze Mueller 《International journal of molecular sciences》2022,23(15)
Atopic eczema (AE) is an inflammatory skin disorder affecting approximately 20% of children worldwide and early onset can lead to asthma and allergies. Currently, the mechanisms of the disease are not fully understood. Metabolomics, the analysis of small molecules in the skin produced by the host and microbes, opens a window to observe the mechanisms of the disease which then may lead to new drug targets for AE treatment. Here, we review the latest advances in AE metabolomics, highlighting both the lipid and non-lipid molecules, along with reviewing the metabolites currently known to reside in the skin. 相似文献
27.
28.
Giulia Gizzi Samuela Cataldi Claudia Mazzeschi Elisa Delvecchio Maria Rachele Ceccarini Michela Codini Elisabetta Albi 《International journal of molecular sciences》2022,23(13)
The relationship between cholesterol and cancer has been widely demonstrated. Clinical studies have shown changes in blood cholesterol levels in cancer patients. In parallel, basic research studies have shown that cholesterol is involved in the mechanisms of onset and progression of the disease. On the other hand, anorexic patients have high cholesterol levels and a high susceptibility to cancer. In this review, we first present a brief background on the relations among nutrition, eating disorders and cancer. Using several notable examples, we then illustrate the changes in cholesterol in cancer and in anorexia nervosa, providing evidence for their important relationship. Finally, we show a new possible link between cholesterol disorder in cancer and in anorexia nervosa. 相似文献
29.
Claudia F. Castillo Vicente Feliu Batlle 《International journal of systems science》2014,45(4):714-727
A two-degree-of-freedom flexible antenna sensor platform was designed to physically simulate the ability of a robotic arm, which rapidly reorients and targets itself towards specific surfaces from different approachable angles. An accurate antenna model involves non-linear expressions that represent the system dynamics. Therefore, a comprehensive study along with experimental work has been carried out in order to achieve accurate system identification and validate the dynamic model. The model developed has proven useful in controlling the antenna tip, minimising the effects of the non-linear flexural dynamics and the Coulomb friction. The system was driven by servo motors. Algebraic controllers were developed for the antenna tip to track the reference trajectory. The platform system used encoders to measure the joint angles and a loadcell sensor to obtain the flexible link tip position. To validate the sensory information, the results obtained by the integrated sensors were compared to that of an external camera system. 相似文献
30.
Claudia Archetti Nicola Bianchessi Stefan Irnich M. Grazia Speranza 《International Transactions in Operational Research》2014,21(3):353-374
In this paper, we present and compare formulations for the inventory routing problem (IRP) where the demand of customers has to be served, over a discrete time horizon, by capacitated vehicles starting and ending their routes at a depot. The objective of the IRP is the minimization of the sum of inventory and transportation costs. The formulations include known and new mathematical programming formulations. Valid inequalities are also presented. The formulations are tested on a large set of benchmark instances. One of the most significant conclusions is that the formulations that use vehicle‐indexed variables are superior to the more compact, aggregate formulations. 相似文献