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101.
In this study, the acute copper sensitivity of field-collected cladoceran species was determined using their natural surface waters and a standard reconstituted test water as test medium. A total of 43 species were collected on two occasions from six different sites, representing different water types and chemistries in Europe. The collected species belonged to four different families (Daphniidae, Bosminidae, Macrothricidae, Chydoridae) and 11 different genera (Daphnia, Ctenodaphnia, Ceriodaphnia, Simocephalus, Scapholeberis, Alona, Acroperus, Chydorus, Eurycercus, Disparalona, Pleuroxus). In acute experiments with immobilization as end point, the 48-h median effective concentrations (48-h EC50) for the cladoceran species ranged from 5.30 to 70.6 microg of Cu L(-1) in standard test water and from 9.60 to 853 microg of Cu L(-1) in natural waters. The mean site sensitivity (the geometric mean of 48-h EC50 values of species within a community) ranged from 10.1 to 27.4 microg of Cu L(-1) in standard water and from 16.4 to 281 microg of Cu L(-1) in natural water. This indicates that bioavailability is more importantthan inter-community (species composition) differences in determining the variability of copper toxicity across different aquatic systems. For the four surface waters that had a pH within the range for which the acute Daphnia magna biotic ligand model (BLM) has previously been successfully validated, the BLM predicted 48-h EC50 values for 27 of the 28 tested cladoceran species within factor of 2 of the observed values. For the same sites, all community sensitivities were predicted within a factor of 2.3. The BLM was clearly over-protective for the two acidic surface waters tested. Hence, the BLM can be considered a valuable tool for estimating the potentially harmful effects of copperto natural cladoceran communities, but more research will be needed for acidic surface waters. 相似文献
102.
Rui Loureiro Farshid Amirabdollahian Michael Topping Bart Driessen William Harwin 《Autonomous Robots》2003,15(1):35-51
Stroke is a leading cause of disability in particular affecting older people. Although the causes of stroke are well known and it is possible to reduce these risks, there is still a need to improve rehabilitation techniques. Early studies in the literature suggest that early intensive therapies can enhance a patient's recovery. According to physiotherapy literature, attention and motivation are key factors for motor relearning following stroke. Machine mediated therapy offers the potential to improve the outcome of stroke patients engaged on rehabilitation for upper limb motor impairment. Haptic interfaces are a particular group of robots that are attractive due to their ability to safely interact with humans. They can enhance traditional therapy tools, provide therapy on demand and can present accurate objective measurements of a patient's progression. Our recent studies suggest the use of tele-presence and VR-based systems can potentially motivate patients to exercise for longer periods of time. The creation of human-like trajectories is essential for retraining upper limb movements of people that have lost manipulation functions following stroke. By coupling models for human arm movement with haptic interfaces and VR technology it is possible to create a new class of robot mediated neuro rehabilitation tools. This paper provides an overview on different approaches to robot mediated therapy and describes a system based on haptics and virtual reality visualisation techniques, where particular emphasis is given to different control strategies for interaction derived from minimum jerk theory and the aid of virtual and mixed reality based exercises. 相似文献
103.
Paolo Tonella Marco Torchiano Bart Du Bois Tarja Systä 《Empirical Software Engineering》2007,12(5):551-571
Starting with the aim of modernizing legacy systems, often written in old programming languages, reverse engineering has extended its applicability to virtually every kind of software system. Moreover, the methods originally designed to recover a diagrammatic, high-level view of the target system have been extended to address several other problems faced by programmers when they need to understand and modify existing software. The authors’ position is that the next stage of development for this discipline will necessarily be based on empirical evaluation of methods. In fact, this evaluation is required to gain knowledge about the actual effects of applying a given approach, as well as to convince the end users of the positive cost–benefit trade offs. The contribution of this paper to the state of the art is a roadmap for the future research in the field, which includes: clarifying the scope of investigation, defining a reference taxonomy, and adopting a common framework for the execution of the experiments. 相似文献
104.
Philip J. Murray Bart Cornelissen Katherine A. Vallis S. Jon Chapman 《Journal of the Royal Society Interface》2016,13(114)
DNA double-strand breaks (DSBs) are formed as a result of genotoxic insults, such as exogenous ionizing radiation, and are among the most serious types of DNA damage. One of the earliest molecular responses following DSB formation is the phosphorylation of the histone H2AX, giving rise to γH2AX. Many copies of γH2AX are generated at DSBs and can be detected in vitro as foci using well-established immuno-histochemical methods. It has previously been shown that anti-γH2AX antibodies, modified by the addition of the cell-penetrating peptide TAT and a fluorescent or radionuclide label, can be used to visualize and quantify DSBs in vivo. Moreover, when labelled with a high amount of the short-range, Auger electron-emitting radioisotope, 111In, the amount of DNA damage within a cell can be increased, leading to cell death. In this report, we develop a mathematical model that describes how molecular processes at individual sites of DNA damage give rise to quantifiable foci. Equations that describe stochastic mean behaviours at individual DSB sites are derived and parametrized using population-scale, time-series measurements from two different cancer cell lines. The model is used to examine two case studies in which the introduction of an antibody (anti-γH2AX-TAT) that targets a key component in the DSB repair pathway influences system behaviour. We investigate: (i) how the interaction between anti-γH2AX-TAT and γH2AX effects the kinetics of H2AX phosphorylation and DSB repair and (ii) model behaviour when the anti-γH2AX antibody is labelled with Auger electron-emitting 111In and can thus instigate additional DNA damage. This work supports the conclusion that DSB kinetics are largely unaffected by the introduction of the anti-γH2AX antibody, a result that has been validated experimentally, and hence the hypothesis that the use of anti-γH2AX antibody to quantify DSBs does not violate the image tracer principle. Moreover, it provides a novel model of DNA damage accumulation in the presence of Auger electron-emitting 111In that is supported qualitatively by the available experimental data. 相似文献
105.
Impact of the Nanoscale Gap Morphology on the Plasmon Coupling in Asymmetric Nanoparticle Dimer Antennas 下载免费PDF全文
Paul S. Popp Janning F. Herrmann Eva‐Corinna Fritz Bart Jan Ravoo Christiane Höppener 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(12):1667-1675
Coupling of plasmon resonances in metallic gap antennas is of interest for a wide range of applications due to the highly localized strong electric fields supported by these structures, and their high sensitivity to alterations of their structure, geometry, and environment. Morphological alterations of asymmetric nanoparticle dimer antennas with (sub)‐nanometer size gaps are assigned to changes of their optical response in correlative dark‐field spectroscopy and high‐resolution transmission electron microscopy (HR‐TEM) investigations. This multimodal approach to investigate individual dimer structures clearly demonstrates that the coupling of the plasmon modes, in addition to well‐known parameters such as the particle geometry and the gap size, is also affected by the relative alignment of both nanoparticles. The investigations corroborate that the alignment of the gap forming facets, and with that the gap area, is crucial for their scattering properties. The impact of a flat versus a rounded gap structure on the optical properties of equivalent dimers becomes stronger with decreasing gap size. These results hint at a higher confinement of the electric field in the gap and possibly a different onset of quantum transport effects for flat and rounded gap antennas in corresponding structures for very narrow gaps. 相似文献
106.
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108.
In this paper we show that finding solutions of a system of multivariate polynomial equalities and inequalities in the max algebra is equivalent to solving an Extended Linear Complementarity Problem. This allows us to find all solutions of such a system of multivariate polynomial equalities and inequalities and provides a geometrical insight in the structure of the solution set. We also demonstrate that this enables us to solve many important problems in the max algebra and the max-min-plus algebra such as matrix decompositions, construction of matrices with a given characteristic polynomial, state space transformations and the (minimal) state space realization problem.Research assistant with the N.F.W.O. (Belgian National Fund for Scientific Research).Senior research associate with the N.F.W.O. 相似文献
109.
In this paper, a social capital perspective is applied to the relationship between the IT department and the Business organization. IT and Business are conceptualized as different occupational communities, with different understandings of their work. Our focus is on the level of social capital and the process of knowledge sharing between these occupational communities. We analyze the role that these factors play in reaching a mutual understanding within the process of IS development, and the influence this has on the perceived performance of the IT organization. Our study, combining qualitative and quantitative methods, points out that a lack of social capital (structural, relational as well as cognitive) can serve as an explanation for the often problematic relationship between these communities. Our analyses also show that social capital is especially relevant for the Business organization's perception of IT performance, whereas the IT department's perception is that performance is primarily dependent on the exchange of information. 相似文献
110.
Jan Smans Bart Jacobs Frank Piessens Wolfram Schulte 《Formal Aspects of Computing》2010,22(3-4):423-457
Framing in the presence of data abstraction is a challenging and important problem in the verification of object-oriented programs Leavens et al. (Formal Aspects Comput (FACS) 19:159–189, 2007). The dynamic frames approach is a promising solution to this problem. However, the approach is formalized in the context of an idealized logical framework. In particular, it is not clear the solution is suitable for use within a program verifier for a Java-like language based on verification condition generation and automated, first-order theorem proving. In this paper, we demonstrate that the dynamic frames approach can be integrated into an automatic verifier based on verification condition generation and automated theorem proving. The approach has been proven sound and has been implemented in a verifier prototype. The prototype has been used to prove correctness of several programming patterns considered challenging in related work. 相似文献