全文获取类型
收费全文 | 1292篇 |
免费 | 76篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 295篇 |
金属工艺 | 32篇 |
机械仪表 | 18篇 |
建筑科学 | 61篇 |
矿业工程 | 2篇 |
能源动力 | 41篇 |
轻工业 | 80篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 63篇 |
一般工业技术 | 295篇 |
冶金工业 | 256篇 |
原子能技术 | 7篇 |
自动化技术 | 205篇 |
出版年
2024年 | 5篇 |
2023年 | 34篇 |
2022年 | 41篇 |
2021年 | 59篇 |
2020年 | 42篇 |
2019年 | 46篇 |
2018年 | 53篇 |
2017年 | 49篇 |
2016年 | 39篇 |
2015年 | 33篇 |
2014年 | 38篇 |
2013年 | 86篇 |
2012年 | 65篇 |
2011年 | 57篇 |
2010年 | 52篇 |
2009年 | 58篇 |
2008年 | 60篇 |
2007年 | 40篇 |
2006年 | 41篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 65篇 |
1997年 | 35篇 |
1996年 | 39篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 26篇 |
1992年 | 18篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1976年 | 15篇 |
1969年 | 3篇 |
1957年 | 3篇 |
1954年 | 3篇 |
1943年 | 4篇 |
排序方式: 共有1370条查询结果,搜索用时 24 毫秒
81.
Passive air sampling using semipermeable membrane devices at different wind-speeds in situ calibrated by performance reference compounds 总被引:1,自引:0,他引:1
Semipermeable membrane devices (SPMDs) are passive samplers used to measure the vapor phase of organic pollutants in air. This study tested whether extremely high wind-speeds during a 21-day sampling increased the sampling rates of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), and whether the release of performance reference compounds (PRCs) was related to the uptakes at different wind-speeds. Five samplers were deployed in an indoor, unheated, and dark wind tunnel with different wind-speeds at each site (6-50 m s(-1)). In addition, one sampler was deployed outside the wind tunnel and one outside the building. To test whether a sampler, designed to reduce the wind-speeds, decreased the uptake and release rates, each sampler in the wind tunnel included two SPMDs positioned inside a protective device and one unprotected SPMD outside the device. The highest amounts of PAHs and PCBs were found in the SPMDs exposed to the assumed highest wind-speeds. Thus, the SPMD sampling rates increased with increasing wind-speeds, indicating that the uptake was largely controlled by the boundary layer at the membrane-air interface. The coefficient of variance (introduced by the 21-day sampling and the chemical analysis) for the air concentrations of three PAHs and three PCBs, calculated using the PRC data, was 28-46%. Thus, the PRCs had a high ability to predict site effects of wind and assess the actual sampling situation. Comparison between protected and unprotected SPMDs showed that the sampler design reduced the wind-speed inside the devices and thereby the uptake and release rates. 相似文献
82.
We have developed a novel strategy to identify enzyme inhibitors that interact directly with their enzyme targets. In the approach, an enzyme is immobilized on a sensor chip, and it is determined whether the immobilized enzyme is still active by incubation with model substrates and mass spectrometric analysis of the products. Putative inhibitors or mixtures containing putative inhibitors are then injected over the sensor chip for binding analysis with surface plasmon resonance. It is then tested whether the bound compounds inhibit the enzymatic activity by subsequent incubation with the model substrate and mass spectrometric analysis. If the bound compound inhibits the enzyme, the inhibitor is eluted from the enzyme and characterized by mass spectrometry. To test the strategy, it has been applied to the well-characterized interaction between trypsin and pure bovine pancreas trypsin inhibitor. Furthermore, fractions of plant extracts were screened for binding to and inhibition of carboxypeptidase B. 相似文献
83.
Jonas Beskow 《International Journal of Speech Technology》2004,7(4):335-349
This paper deals with the problem of modelling the dynamics of articulation for a parameterised talking head based on phonetic input. Four different models are implemented and trained to reproduce the articulatory patterns of a real speaker, based on a corpus of optical measurements. Two of the models, (Cohen-Massaro and Öhman) are based on coarticulation models from speech production theory and two are based on artificial neural networks, one of which is specially intended for streaming real-time applications. The different models are evaluated through comparison between predicted and measured trajectories, which shows that the Cohen-Massaro model produces trajectories that best matches the measurements. A perceptual intelligibility experiment is also carried out, where the four data-driven models are compared against a rule-based model as well as an audio-alone condition. Results show that all models give significantly increased speech intelligibility over the audio-alone case, with the rule-based model yielding highest intelligibility score. 相似文献
84.
Nonpolar lipids and sound velocity at different distances from the skin surface within a sample of pilot whale melon were
studied. Thin layer chromatography, sensitive radioisotopic methods, and an ultrasonic echo scanner were used. Wax esters
had a maximum concentration at 11–12 cm from the skin surface. Non- and monoisovalero triglycerides both exhibited a minimum
at 8–10 cm, whereas the diisovalero species increased steadily from the skin surface towards the center of the pilot whale
head. A minimum of sound velocity, ca. 1340 m/s, was found at 9–11 cm, thus coinciding with a region rich in isovaleric acid
esterified in wax and diisovalero triglycerides. These findings are compatible with predictions based on the known correlations
between lipid structure and sound velocity. Consequently, additional evidence for refraction of sound in pilot whale melon
is presented. This is important in understanding the system of echolocation of toothed whales. 相似文献
85.
Anselmo Antunes Montenegro Luiz Velho Paulo C. P. Carvalho Jonas Sossai Jr. 《Journal of Mathematical Imaging and Vision》2007,29(2-3):119-130
In this work we propose a method for computing mesh representations of 3D objects reconstructed from a set of silhouette images.
Our method is based on the polygonization of volumetric reconstructions by using a modified version of the dual contouring method. In order to apply dual contouring on volumetric reconstruction from silhouettes we devised a method that is able
to determine the discrete topology of the surface in relation to the octree cells. We also developed a new scheme for computing
hermitian data representing the intersections of conic volumes with the octree cells and their corresponding normals with
subpixel accuracy. Due to the discrete and extremely noisy nature of the data used in the reconstruction we had to devise
a different criterion for mesh simplification that applies topological consistency tests only when the geometric error measure
is beyond a given tolerance. We present results of the application of the proposed method in the extraction of a mesh corresponding
to the surface of objects of a real scene. 相似文献
86.
Sylwia Nowakowska Aneliia Wäckerlin Ignacio Piquero‐Zulaica Jan Nowakowski Shigeki Kawai Christian Wäckerlin Manfred Matena Thomas Nijs Shadi Fatayer Olha Popova Aisha Ahsan S. Fatemeh Mousavi Toni Ivas Ernst Meyer Meike Stöhr J. Enrique Ortega Jonas Björk Lutz H. Gade Jorge Lobo‐Checa Thomas A. Jung 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(28):3757-3763
87.
Two-tier streaming settings are a typical dynamic environment where continuous skylines represent an important semantic indicator for multiple attributes. To monitor skylines over the dynamic data in such settings, one needs to continuously update the skyline query results in order to reflect the new data values. This paper tackles the problem of continuous skyline monitoring on a central query server over dynamic data from multiple data sites. Simply sending the updates of tuple values to the server is cost-prohibitive. Therefore, we propose an approach that allows the central server to collaborate with the data sites to monitor the possible skyline changes. By doing so, the processing load is distributed over all the data sites instead of only on the central server. Furthermore, this collaborative approach minimizes the bandwidth consumption between the server and the data sites, which is often critical in a widely distributed environment such as a wide-area sensor network. We give theoretical upper bounds for the computation costs and communication costs of the proposed collaborative approach. We also conduct extensive experiments on both synthetic and real data sets. The experimental results demonstrate that our collaborative approach is efficient, scalable and well-balanced in terms of communication costs and computation costs. 相似文献
88.
This study develops a model for inventory management consisting of a two-echelon supply chain (SC) with profit sharing and deteriorating items. The retailer and the supplier act as the leader and follower, in which the supplier faces a huge setup cost and economic order quantity ordering strategy. The market demand is affected by the sale price of the product, and the inventory has a deterioration rate following a Weibull distribution. The retailer executes three profit-sharing mechanisms to motivate the supplier to participate in SC optimisation and to extend the life cycle of the product. A search algorithm is developed to determine the solutions as using the profit-sharing mechanisms. The outcomes from numerical experiments demonstrate the profitability of the proposed model. 相似文献
89.
Hülsheger Ute R.; Lang Jonas W. B.; Maier Günter W. 《Canadian Metallurgical Quarterly》2010,15(4):505
Models of emotional labor suggest that emotional labor leads to strain and affects job performance. Although the link between emotional labor, strain, and performance has been well documented in cross-sectional field studies, not much is known about the causal direction of relationships between emotional labor, strain, and performance. Goal of the present study was therefore to test the direction of effects in a two-wave longitudinal panel study using a sample of 151 trainee teachers. Longitudinal lagged effects were tested using structural equation modeling. Results revealed that the emotional labor strategy of surface acting led to increases in subsequent strain while deep acting led to increases in job performance. In contrast, there was no indication of reverse causation: Neither strain nor job performance had a significant lagged effect on subsequent surface or deep acting. Overall, results support models of emotional labor suggesting that surface and deep acting causally precede individual and organizational well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.
The Avrami kinetics of dynamic recrystallization 总被引:2,自引:0,他引:2
Twenty-six flow curves determined under dynamic recrystallization (DRX) conditions on 11 different steels were analyzed. The double-differentiation method was used to define the critical strain εc for initiation of DRX. The “athermal” hardening parameter h and the dynamic recovery parameter r were evaluated from the work-hardening behavior prior to εc. The saturation stresses σsat pertaining to the unrecrystallized regions as well as the associated work-hardening curves, σrecov, were derived in this way. The net softening attributable to DRX was then defined as the difference between the σrecov and experimental curves. Avrami plots were prepared from all 26 sets of data. The time exponents were all in the neighborhood of 3.0; however, the strain rate and temperature dependences differed considerably from their static values. The dependence of the time of half-softening, t50, on strain rate and temperature is used to predict the DRX curves expected under industrial conditions. 相似文献