全文获取类型
收费全文 | 1060篇 |
免费 | 63篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 221篇 |
金属工艺 | 47篇 |
机械仪表 | 19篇 |
建筑科学 | 42篇 |
矿业工程 | 1篇 |
能源动力 | 41篇 |
轻工业 | 65篇 |
水利工程 | 3篇 |
无线电 | 101篇 |
一般工业技术 | 190篇 |
冶金工业 | 160篇 |
原子能技术 | 12篇 |
自动化技术 | 206篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 32篇 |
2021年 | 43篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 45篇 |
2016年 | 45篇 |
2015年 | 31篇 |
2014年 | 39篇 |
2013年 | 57篇 |
2012年 | 84篇 |
2011年 | 82篇 |
2010年 | 57篇 |
2009年 | 61篇 |
2008年 | 70篇 |
2007年 | 43篇 |
2006年 | 33篇 |
2005年 | 30篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 38篇 |
1997年 | 23篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1973年 | 3篇 |
1967年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有1123条查询结果,搜索用时 328 毫秒
21.
Mathieu Le Coz François Delclaux Pierre Genthon Guillaume Favreau 《Computers & Geosciences》2009,35(8):1661-1670
Digital Elevation Models (DEMs) are used to compute the hydro-geomorphological variables required by distributed hydrological models. However, the resolution of the most precise DEMs is too fine to run these models over regional watersheds. DEMs therefore need to be aggregated to coarser resolutions, affecting both the representation of the land surface and the hydrological simulations. In the present paper, six algorithms (mean, median, mode, nearest neighbour, maximum and minimum) are used to aggregate the Shuttle Radar Topography Mission (SRTM) DEM from 3″ (90 m) to 5′ (10 km) in order to simulate the water balance of the Lake Chad basin (2.5 Mkm2). Each of these methods is assessed with respect to selected hydro-geomorphological properties that influence Terrestrial Hydrology Model with Biogeochemistry (THMB) simulations, namely the drainage network, the Lake Chad bottom topography and the floodplain extent.The results show that mean and median methods produce a smoother representation of the topography. This smoothing involves the removing of the depressions governing the floodplain dynamics (floodplain area<5000 km2) but it eliminates the spikes and wells responsible for deviations regarding the drainage network. By contrast, using other aggregation methods, a rougher relief representation enables the simulation of a higher floodplain area (>14,000 km2 with the maximum or nearest neighbour) but results in anomalies concerning the drainage network. An aggregation procedure based on a variographic analysis of the SRTM data is therefore suggested. This consists of preliminary filtering of the 3″ DEM in order to smooth spikes and wells, then resampling to 5′ via the nearest neighbour method so as to preserve the representation of depressions. With the resulting DEM, the drainage network, the Lake Chad bathymetric curves and the simulated floodplain hydrology are consistent with the observations (3% underestimation for simulated evaporation volumes). 相似文献
22.
Frédéric Havet Martin Klazar Jan Kratochvíl Dieter Kratsch Mathieu Liedloff 《Algorithmica》2011,59(2):169-194
The notion of distance constrained graph labelings, motivated by the Frequency Assignment Problem, reads as follows: A mapping
from the vertex set of a graph G=(V,E) into an interval of integers {0,…,k} is an L(2,1)-labeling of G of span k if any two adjacent vertices are mapped onto integers that are at least 2 apart, and every two vertices with a common neighbor
are mapped onto distinct integers. It is known that for any fixed k≥4, deciding the existence of such a labeling is an NP-complete problem. We present exact exponential time algorithms that
are faster than the naive O
*((k+1)
n
) algorithm that would try all possible mappings. The improvement is best seen in the first NP-complete case of k=4, where the running time of our algorithm is O(1.3006
n
). Furthermore we show that dynamic programming can be used to establish an O(3.8730
n
) algorithm to compute an optimal L(2,1)-labeling. 相似文献
23.
Towards a continuous microfluidic rheometer 总被引:1,自引:1,他引:0
Pierre Guillot Thomas Moulin Roman Kötitz Matthieu Guirardel Arash Dodge Mathieu Joanicot Annie Colin Charles-Henri Bruneau Thierry Colin 《Microfluidics and nanofluidics》2008,5(5):619-630
In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot
et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure
sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on
both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity
of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous
fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method
allows us to measure the flow curve of a fluid with less than 250 μL of fluid. In this paper we implement this principle in
a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity
of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare
our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set
up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation
composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with
only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the
viscosity range and the behavior of the fluid to an applied stress must be evaluated. 相似文献
24.
Valence-Driven Connectivity Encoding for 3D Meshes 总被引:13,自引:0,他引:13
In this paper, we propose a valence-driven, single-resolution encoding technique for lossless compression of triangle mesh connectivity. Building upon a valence-based approach pioneered by Touma and Gotsman22 , we design a new valence-driven conquest for arbitrary meshes that always guarantees smaller compression rates than the original method. Furthermore, we provide a novel theoretical entropy study of our technique, hinting the optimality of the valence-driven approach. Finally, we demonstrate the practical efficiency of this approach (in agreement with the theoretical prediction) on a series of test meshes, resulting in the lowest compression ratios published so far, for both irregular and regular meshes, small or large. 相似文献
25.
Patrick Mullie Alice Koechlin Mathieu Boniol Peter Boyle 《Critical reviews in food science and nutrition》2016,56(1):152-159
Breast cancer is the commonest form of cancer in women worldwide. It has been suggested that chronic hyperinsulinemia associated with insulin resistance plays a role in breast cancer etiology. To test the hyperinsulinemia hypothesis, a dietary pattern associated with a high glycemic index and glycemic load, both proxies for chronic hyperinsulinemia, should be associated with an increased risk of breast cancer. A meta-analysis restricted to prospective cohort studies was undertaken using a random effects model with tests for statistical significance, publication bias and heterogeneity. The metric for analysis was the risk of breast cancer in the highest relative to the lowest glycemic index and glycemic load dietary pattern. A dietary pattern with a high glycemic index was associated with a summary relative risk (SRR) of 1.05 (95% CI: 1.00, 1.11), and a high glycemic load with a SRR of 1.06 (95% CI: 1.00, 1.13). Adjustments for body mass index [BMI], physical activity and other lifestyle factors did not influence the SRR, nor did menopausal status and estrogen receptor status of the tumor. In conclusion, the current evidence supports a modest association between a dietary pattern with high glycemic index or glycemic load and the risk of breast cancer. 相似文献
26.
27.
28.
29.
In this paper, we present a new approach for junction detection and characterization in line-drawing images. We formulate this problem as searching for optimal meeting points of median lines. In this context, the main contribution of the proposed approach is three-fold. First, a new algorithm for the determination of the support region is presented using the linear least squares technique, making it robust to digitization effects. Second, an efficient algorithm is proposed to detect and conceptually remove all distorted zones, retaining reliable line segments only. These line segments are then locally characterized to form a local structure representation of each crossing zone. Finally, a novel optimization algorithm is presented to reconstruct the junctions. Junction characterization is then simply derived. The proposed approach is very highly robust to common geometry transformations and can resist a satisfactory level of noise/degradation. Furthermore, it works very efficiently in terms of time complexity and requires no prior knowledge of the document content. Extensive evaluations have been performed to validate the proposed approach using other baseline methods. An application of symbol spotting is also provided, demonstrating quite good results. 相似文献
30.
Mathieu Allyson-Cyr 《Numerical Heat Transfer, Part A: Applications》2019,76(5):323-347
In this study, the best settings of five heuristics are determined for solving a mixed-integer non-linear multi-objective optimization problem. The algorithms treated in the article are: ant colony optimization, genetic algorithm, particle swarm optimization, differential evolution, and teaching-learning basic algorithm. The optimization problem consists in optimizing the design of a thermoelectric device, based on a model available in literature. Results showed that the inner settings can have different effects on the algorithm performance criteria depending on the algorithm. A formulation based on the weighted sum method is introduced for solving the multiobjective optimization problem with optimal settings. It was found that the five heuristic algorithms have comparable performances. Differential evolution generated the highest number of non-dominated solutions in comparison with the other algorithms. 相似文献