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801.
802.
Organophosphorus and pyrethroid insecticide urinary metabolite concentrations in young children living in a southeastern United States city 总被引:1,自引:0,他引:1
Luke P. Naeher Nicolle S. Tulve Peter P. Egeghy Olorunfemi Adetona Larry L. Needham Elizabeth Bozeman Aaron Hilliard 《The Science of the total environment》2010,408(5):1145-4884
Pesticide metabolites are routinely measured in the urine of children in the United States. Although the sources of these metabolites are believed to include residues in food from agricultural applications and residues from applications in everyday environments (e.g., homes), few studies have been able to demonstrate an association between indoor residential pesticide applications and pesticide metabolite concentrations. To better quantify the effects of potential risk factors related to demographics, household characteristics, occupation, and pesticide use practices on urinary biomarker levels, we performed a study in a city (Jacksonville, Florida) previously determined to have elevated rates of pesticide use. We enrolled a convenience sample of 203 children ranging in age from 4 to 6 years; their caregivers completed a questionnaire and the children provided a urine sample, which was analyzed for a series of organophosphorus and pyrethroid insecticide metabolites. The questionnaire responses substantiated much higher pesticide use for the study participants as compared to other studies. Urinary metabolite concentrations were approximately an order of magnitude higher than concentrations reported for young children in other studies. Few statistically significant differences (at the p < 0.05 level) were observed, however, several trends are worth noting. In general, mean urinary pesticide metabolite concentrations were higher for males, Caucasians, and those children living in homes with an indoor pesticide application occurring within the past four weeks. Comparing the urinary pesticide metabolite concentrations in this study to those reported in the NHANES and GerES studies showed that the children living in Jacksonville had substantially higher pyrethroid pesticide exposures than the general populations of the United States and Germany. Further research is needed in communities where routine pesticide use has been documented to obtain information on the most important routes and pathways of exposure and to develop the most effective strategies for reducing pesticide exposures for children. 相似文献
803.
Cooperative Multi-Agent Learning: The State of the Art 总被引:1,自引:4,他引:1
Cooperative multi-agent systems (MAS) are ones in which several agents attempt, through their interaction, to jointly solve
tasks or to maximize utility. Due to the interactions among the agents, multi-agent problem complexity can rise rapidly with
the number of agents or their behavioral sophistication. The challenge this presents to the task of programming solutions
to MAS problems has spawned increasing interest in machine learning techniques to automate the search and optimization process.
We provide a broad survey of the cooperative multi-agent learning literature. Previous surveys of this area have largely focused
on issues common to specific subareas (for example, reinforcement learning, RL or robotics). In this survey we attempt to
draw from multi-agent learning work in a spectrum of areas, including RL, evolutionary computation, game theory, complex systems,
agent modeling, and robotics. We find that this broad view leads to a division of the work into two categories, each with
its own special issues: applying a single learner to discover joint solutions to multi-agent problems (team learning), or using multiple simultaneous learners, often one per agent (concurrent learning). Additionally, we discuss direct and indirect communication in connection with learning, plus open issues in task decomposition,
scalability, and adaptive dynamics. We conclude with a presentation of multi-agent learning problem domains, and a list of
multi-agent learning resources. 相似文献
804.
Lin Yan Paul Aaron Ullrich Luke P. Van Roekel Bei Wang Hanqi Guo 《Computer Graphics Forum》2023,42(6):e14799
Critical point tracking is a core topic in scientific visualization for understanding the dynamic behaviour of time-varying vector field data. The topological notion of robustness has been introduced recently to quantify the structural stability of critical points, that is, the robustness of a critical point is the minimum amount of perturbation to the vector field necessary to cancel it. A theoretical basis has been established previously that relates critical point tracking with the notion of robustness, in particular, critical points could be tracked based on their closeness in stability, measured by robustness, instead of just distance proximity within the domain. However, in practice, the computation of classic robustness may produce artifacts when a critical point is close to the boundary of the domain; thus, we do not have a complete picture of the vector field behaviour within its local neighbourhood. To alleviate these issues, we introduce a multilevel robustness framework for the study of 2D time-varying vector fields. We compute the robustness of critical points across varying neighbourhoods to capture the multiscale nature of the data and to mitigate the boundary effect suffered by the classic robustness computation. We demonstrate via experiments that such a new notion of robustness can be combined seamlessly with existing feature tracking algorithms to improve the visual interpretability of vector fields in terms of feature tracking, selection and comparison for large-scale scientific simulations. We observe, for the first time, that the minimum multilevel robustness is highly correlated with physical quantities used by domain scientists in studying a real-world tropical cyclone dataset. Such an observation helps to increase the physical interpretability of robustness. 相似文献
806.
807.
Matthew Rogers Ahasan Habib Gilberto Teobaldi Timothy Moorsom J. Olof Johansson Luke Hedley Paul S. Keatley Robert J. Hicken Manuel Valvidares Pierluigi Gargiani Nader Alosaimi Emiliano Poli Mannan Ali Gavin Burnell Bryan J. Hickey Oscar Cespedes 《Advanced functional materials》2023,33(13):2212173
The long-term future of information storage requires the use of sustainable nanomaterials in architectures operating at high frequencies. Interfaces can play a key role in this pursuit via emergent functionalities that break out from conventional operation methods. Here, spin-filtering effects and photocurrents are combined at metal-molecular-oxide junctions in a hybrid magneto-capacitive memory. Light exposure of metal-fullerene-metal oxide devices results in spin-polarized charge trapping and the formation of a magnetic interface. Because the magnetism is generated by a photocurrent, the writing time is determined by exciton formation and splitting, electron hopping, and spin-dependent trapping. Transient absorption spectroscopy measurements show changes in the electronic states as a function of the magnetic history of the device within picoseconds of the optical pumping. The stored information is read using time-resolved scanning magneto optic Kerr effect measurements during microwave irradiation. The emergence of a magnetic interface in the picosecond timescale opens new paths of research to design hybrid magneto-optic structures operating at high frequencies for sensing, computing, and information storage. 相似文献
808.
809.
Warming temperatures can have negative consequences for aquatic organisms, especially cold-adapted fishes such as Pacific salmon. The magnitude of warming is related to the thermal sensitivity of streams in salmon-bearing watersheds (i.e., change in stream temperature for every 1°C increase in air temperature), which can vary based on several factors including streamflow. Management actions to increase streamflow may therefore benefit salmon by decreasing thermal sensitivity. However, the effects of streamflow on thermal sensitivity are often complex, as the temperature of flow inputs can directly increase or decrease temperatures. This study aimed to disentangle the influence of streamflow on thermal sensitivity and stream temperature over 4 years in the Nicola River, a regulated semiarid watershed in south-central British Columbia, Canada. A statistical modeling approach was used to estimate streamflow effects on stream temperatures and thermal sensitivity (i.e., relationship of regional air temperature to stream temperature) at 12 sites from 2018 to 2021. Streamflow had a variable influence on stream temperatures across the watershed via both direct effects and by modulating thermal sensitivity. At a given site, streamflow was generally negatively associated with summer daily mean stream temperature, but the magnitude of its influence varied among locations and years. The influence of streamflow on thermal sensitivity was also highly variable both spatially and temporally. The analysis suggests that there may be complex relationships between streamflow, stream temperature, and thermal sensitivity, which complicates the efficacy of flow as a lever to mitigate high temperatures in regulated systems. 相似文献
810.
Tang Wei Fancher Chris M. Nandwana Peeyush An Ke Nycz Andrzej Wang Hsin Kannan Rangasayee Trofimov Artem Yu Dunji Leonard Donovan N. Meyer Luke Plotkowski Alex 《Metallurgical and Materials Transactions A》2023,54(3):854-868
Metallurgical and Materials Transactions A - Recent research has studied the use of low transformation temperature (LTT) martensite steel as feedstock for wire arc additive manufacturing (WAAM) and... 相似文献