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31.
This paper assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. First, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends, and trend reversals in the groundwater nitrate concentration. Second, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Third, groundwater recharge CFC (chlorofluorocarbon) age determination allows linking of the first two data sets. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s, while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark. 相似文献
32.
Rong Chai Huili Zhang Xiaoyu Dong Qianbin Chen Tommy Svensson 《Wireless Networks》2014,20(6):1557-1571
The rapid development of mobile broadband services with continuously increasing traffic volumes has resulted in a number of challenges, including ubiquitous network coverage, high bandwidth, and reliable services for reasonable price, etc. To address these challenges, evolved packet system (EPS) is proposed as the evolution of the packet core network. While resource management and load balancing issues in EPS are discussed in 3GPP standardization, relatively few research works consider mechanism design for load information monitoring and evaluation. Furthermore, even though some load balancing algorithms have been proposed for integrated networks, the load balancing scheme design which achieves the optimization of joint system performance has not been extensively studied. In this paper, an inter-access system anchor based load balancing mechanism is introduced which performs load monitoring and evaluation for access gateways and networks, and an optimal load balancing algorithm is proposed for heterogeneous integrated networks. To characterize the performance of integrated networks, the concept of utility function is introduced and the comprehensive performance of integrated networks which support both single type service and multimedia service is modeled mathematically. Applying vertical handoff as an efficient mechanism for achieving load balancing, the optimal number of handoff users is obtained through solving the optimization problem. Numerical results demonstrate that load balancing between access networks can be achieved, and the optimal number of handoff users corresponding to the maximal joint network utility can be obtained. 相似文献
33.
Dealing with high-dimensional data has always been a major problem in many pattern recognition and machine learning applications. Trace ratio criterion is a criterion that can be applicable to many dimensionality reduction methods as it directly reflects Euclidean distance between data points of within or between classes. In this paper, we analyze the trace ratio problem and propose a new efficient algorithm to find the optimal solution. Based on the proposed algorithm, we are able to derive an orthogonal constrained semi-supervised learning framework. The new algorithm incorporates unlabeled data into training procedure so that it is able to preserve the discriminative structure as well as geometrical structure embedded in the original dataset. Under such a framework, many existing semi-supervised dimensionality reduction methods such as SDA, Lap-LDA, SSDR, SSMMC, can be improved using our proposed framework, which can also be used to formulate a corresponding kernel framework for handling nonlinear problems. Theoretical analysis indicates that there are certain relationships between linear and nonlinear methods. Finally, extensive simulations on synthetic dataset and real world dataset are presented to show the effectiveness of our algorithms. The results demonstrate that our proposed algorithm can achieve great superiority to other state-of-art algorithms. 相似文献
34.
Tommy S. W. Wong 《Canadian Metallurgical Quarterly》2005,131(2):210-217
By applying the kinematic wave method to a homogeneous, rectangular overland plane, the influence of the constant and proportional-loss models on the design discharge are examined. The examination shows that with the use of the proportional-loss model, there is no partial-area effect and the design discharge is governed by the full-area contribution. On the other hand, with the use of the constant-loss model, there is no partial-area effect if the loss rate is small. For larger loss rates, there is a partial-area effect; and for this case, the design is complicated, since there is a need to search for the critical storm that governs the partial-area effect. The characteristic of the critical storm is that its rate of decrease in rainfall intensity with duration equals the corresponding rate of increase in the contributing area. The preceding findings are consistent with the design concept in the rational method that uses the proportional-loss model, and the results from earlier studies that used the constant-loss model. 相似文献
35.
John M. Halloin Thomas G. Cooper E. James Potchen Tommy E. Thompson 《Journal of the American Oil Chemists' Society》1993,70(12):1259-1262
Magnetic resonance images of plant tissues typically are manifestations of water protons in tissues. Within oilseeds, however,
lipids contain a major portion of the mobile protons, which should enable specific imaging of lipids. In this study, experiments
were done to demonstrate spin-echo imaging (SEI) and chemical-shift imaging (CSI) of lipid within nonimbibed and imbibed embryos
of pecan (Carya illinoensis), a high-lipid seed. Magnetic resonance spectra of airdry embryos contained a single major peak for lipid, whereas those
of imbibed embryos contained separate peaks for water and lipid. This separation of spectral peaks enabled CSI of distributions
of either lipids or water in imbibed embryos. A longer spin-spin relaxation time of lipid protons than of water protons in
imbibed embryos allowed selective SEI of lipids in those embryos. SEI of normal, dry embryos revealed fairly uniform distribution
of lipids across tissues. Similar images of embryos damaged by the fungusPhoma exocarpina or the insectZerara viridula were less intense than those of a normal embryo, reflecting the lower oil contents of the damaged embryos. Magnetic resonance
imaging should provide a useful technology for studying lipid distribution and metabolism within oil seeds. 相似文献
36.
The Dynamics of Indonesia's Urbanisation, 1980-2006 总被引:1,自引:0,他引:1
This study examines continuity and change in patterns of Indonesia's urbanisation during the boom economy until the decentralisation era, using data mainly from the National Population Census 1980-2000 and from the Village Potential (PODES) 2006. Urbanisation in Indonesia is still characterised by a heavy concentration of the urban population in a few large cities, notably the Jakarta Metropolitan Area (JMA), which might reflect an integration of Jakarta into the global economy. It might also reflect an interurban disparity, between large and smaller cities. The population on the fringes of large cities is growing rapidly, while in the inner cities it is increasing at a very low rate of growth. Urban spatial development in Java is shaping belts, which connect many of the large cities. The intermediate cities and small towns on the outer islands have a relatively higher population growth rate compared with those in Java, which might suggest that those towns and cities are playing a more significant role in regional development. 相似文献
37.
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39.
Ryan Henkensiefken Javier Castro Dale Bentz Tommy Nantung Jason Weiss 《Cement and Concrete Research》2009,39(10):883-892
The increased propensity for shrinkage cracking in low water-to-cement ratio (w/c) concrete has inspired the development of new technologies that can reduce the risk of early-age cracking. One of these is internal curing. Internal curing uses saturated lightweight aggregate to supply ‘curing water’ to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development; however, relatively little detailed information exists about the effects of internal curing on fluid transport properties such as water absorption or diffusivity. This study examines the absorption of water into mortar specimens made with saturated lightweight aggregates (SLWA). These results indicate that the inclusion of SLWA can reduce the water absorption of mortar specimens. This observation was reinforced with electrical conductivity measurements that exhibited similar reductions. 相似文献
40.
Ida Louise G. Borlaug Jan Tommy Gravdahl Jrgen Sverdrup‐Thygeson Kristin Y. Pettersen Antonio Loria 《Asian journal of control》2019,21(1):208-223
The underwater swimming manipulator (USM) is a snake‐like, multi‐articulated, underwater robot that is equipped with thrusters. One of the main purposes of the USM is to act like an underwater floating base manipulator. As such, it is essential to achieve good station‐keeping and trajectory tracking performance for the USM by using the thrusters and by using the joints to attain the desired position and orientation of the head and tail of the USM. In this ‘paper, we propose a sliding mode control (SMC) law, specifically the super‐twisting algorithm with adaptive gains, for the trajectory tracking of the USM's centre of mass. A higher‐order sliding mode observer is proposed for state estimation. Furthermore, we show the ultimate boundedness of the tracking errors. We demonstrate the applicability of the proposed control law and show that it leads to better performance than a linear PD‐controller. 相似文献