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71.
Liu Hsu Marcelo Carvalho Minhoto Teixeira Ramon Romankevicius Costa Edvaldo Assunção 《Asian journal of control》2015,17(5):1484-1497
A Lyapunov design of multiple input, multiple output (MIMO) model‐reference adaptive control (MRAC) systems is proposed using new generalized passivity concepts based on WSPR and WASPR properties. The new design avoids control overparameterization and leads to the simplest unnormalized gradient algorithm by means of a passivating multiplier. To this end, a necessary and sufficient condition on the high frequency gain matrix to achieve the WASPR property is established. This condition is referred to as Positive Diagonal Jordan (PDJ) form. Based on the robustness WSPR and WASPR properties, a systematic determination of a robust passivating matrix multiplier is then presented. The advantages of the new design are illustrated by numerical simulation including a robotics adaptive visual servoing problem and a 4‐input‐4‐output dynamic system. © 2014 Chinese Automatic Control Society and Wiley Publishing Asia Pty Ltd 相似文献
72.
Kefei Liu João Paulo C.L. da Costa Hing Cheung So Florian Römer Martin Haardt Luiz F. de A. Gadêlha 《Digital Signal Processing》2013,23(3):701-711
Accurate estimation of the attitude of unmanned aerial vehicles (UAVs) is crucial for their control and displacement. Errors in the attitude estimate may misuse the limited battery energy of UAVs or even cause an accident. For attitude estimation, proprioceptive sensors such as inertial measurement units (IMUs) are widely applied, but they are susceptible to inertial guidance error. With antenna arrays currently being installed in UAVs for communication with ground base stations, we can take advantage of the array structure in order to improve the estimates of IMUs via data fusion. In this paper, we therefore propose an attitude estimation system based on a hexagon-shaped 7-element electronically steerable parasitic antenna radiator (ESPAR) array. The ESPAR array is well-suited for installment in the UAVs with broad wings and short bodies. Our proposed solution returns an estimation for the pitch and roll based on the inter-element phase delay estimates of the line-of-sight path of the impinging signal over the antenna array. By exploiting the parallel and centrosymmetric structure in the hexagon-shaped ESPAR array, the 3-dimensional Unitary ESPRIT algorithm is applied for phase delay estimation to achieve high accuracy as well as computational efficiency. We devise an attitude estimation algorithm by exploiting the geometrical relationship between the UAV attitude and the estimated phase delays. An analytical closed-form expression of the attitude estimates is obtained by solving the established simultaneous nonlinear equations. Simulations results show the feasibility of our proposed solution for different signal-to-noise ratio levels as well as multipath scenarios. 相似文献
73.
Sujoy Basu Lauro Beltrão Costa Francisco Brasileiro Sujata Banerjee Puneet Sharma Sung-Ju Lee 《Peer-to-Peer Networking and Applications》2009,2(4):348-366
Large scale grid computing systems may provide multitudinous services, from different providers, whose quality of service
will vary. Moreover, services are deployed and undeployed in the grid with no central coordination. Thus, to find out the
most suitable service to fulfill their needs, or to find the most suitable set of resources on which to deploy their services,
grid users must resort to a Grid Information Service (GIS). This service allows users to submit rich queries that are normally
composed of multiple attributes and range operations. The ability to efficiently execute complex searches in a scalable and
reliable way is a key challenge for current GIS designs. Scalability issues are normally dealt with by using peer-to-peer
technologies. However, the more reliable peer-to-peer approaches do not cater for rich queries in a natural way. On the other
hand, approaches that can easily support these rich queries are less robust in the presence of failures. In this paper we
present the design of NodeWiz, a GIS that allows multi-attribute range queries to be performed efficiently in a distributed
manner, while maintaining load balance and resilience to failures. 相似文献
74.
Among healthcare workers, shiftwork (mostly if nightwork is also included), ageing and work-related stress may be factors leading to impaired health. Such risk factors may also operate in interaction, resulting in an even increased harm for health. The present study aims at evaluating these relationships in a sample of 1842 hospital workers in Northern Italy. Subjects were mainly women, 33.1% were aged > or = 45 yr, and they were almost evenly distributed between dayworkers and rotating shiftworkers (nights included). Shiftwork was associated with poor sleep, while it was protective against gastrointestinal disorders, poor work ability and job dissatisfaction. Work stress was the risk factor with the highest relevance for poor health. Ageing was associated with lower physical health. Few significant interactions were observed. Shiftwork with nights and high work stress significantly interacted in increasing the risk for poor sleep. The "healthy worker effect" may have played a strong role in study findings. 相似文献
75.
STUDY OBJECTIVE: To investigate social differences in cancer incidence in Turin, Italy in 1985-87. DESIGN: A cancer incidence follow up study of the turin population in relation to socioeconomic characteristics was performed through record linkage between the 1981 census and the cancer registry. A case-control study nested in the cohort was analysed, where cases were subjects with a new diagnosis of cancer in 1985-87 and controls were a sample of the Turin population, frequency matched by sex and age group. Incidence odd ratios (ORs) were calculated for social classes (defined by education, housing tenure, and socioeconomic group) using a logistic regression model. SETTING: The study population comprised subjects included in the 1981 Turin census (n approximately equal to 1,100,000) who were still alive, 20-69 years old, and were resident in Turin in the middle of study period. PARTICIPANTS: The analyses were based on 4215 male and 3451 female cases, and on 16,913 male and 13,838 female controls. MAIN RESULTS: Compared with the highest educational level, the men in the lowest one showed an OR > 2 for respiratory cancers; OR = 1.48 for stomach cancer; and ORs < 0.7 for skin, colorectal, and prostate cancers. Women with a primary school education were protected against colorectal (OR = 0.71), skin (OR = 0.59), and breast cancer (OR = 0.66) compared with university degree women, but were at risk for cancer of the cervix (OR = 2.33) and stomach cancer (OR = 2.84). The association between educational level (primary school v university) and lung cancer risk is negative for men (OR = 2.47) and positive for women (OR = 0.62), while the association with housing tenure is negative for both sexes (OR = 1.44). CONCLUSIONS: The socioeconomic distribution of some risk factors (for example smoking, alcohol, and diet) in Italy can partially explain the differences in respiratory and digestive cancers. "Unbalanced" health promotion interventions, targeted at social groups with the highest prevalences of risk factors, and national policies for increasing the level of education in the country may play an important role in reducing social differences in cancer risk. 相似文献
76.
A simulation of the profile of holographically recorded structures in photoresists is performed. In addition to its simplicity this simulation can be used to take into account the effects that arise from exposure, photosensitization, development, and resolution of positive photoresists. We analyzed the effects of isotropy of wet development, nonlinearity of the photoresist response curve, background light, and standing waves produced by reflection at the film-substrate interface by using this simulation, and the results agree with the experimentally recorded profiles. 相似文献
77.
SA de Oliveira WN Soares MO Dalston MT de Almeida AJ Costa 《Canadian Metallurgical Quarterly》1995,28(4):339-343
Malignant mesothelioma is caused almost exclusively by occupational exposure to asbestos. During the past few years, however, increasing evidence has mounted that background exposure to asbestos could be sufficient to cause mesothelioma. Treatment of malignant mesothelioma remains a big problem. Some new approaches are on their way, and the most exciting ones are local immunotherapy in very early cases. Some success has been reported with local interferon treatment. As for treatment of metastatic pleural disease, the main purpose is symptomatic relief of dyspnea caused by fluid accumulation. The best way to achieve a lasting palliation is pleurodesis, and the most common way to do this, is by chemical means. The drug of choice in the United States has for many years been tetracycline, but since injectable tetracycline is no longer available, some substitute must be found. The substance that will "win" is not yet clear, but the two leading contestants are talc and doxycycline. Bleomycin also has its supporters, and a dark horse is quinacrine, which although not easily available in the United States, has been used in many European centers for decades. 相似文献
78.
Costa A. Buffa G. Palmeri D. Pollara G. Fratini L. 《Journal of Intelligent Manufacturing》2022,33(7):1967-1989
Journal of Intelligent Manufacturing - It is well known that the processing parameters of selective laser melting (SLM) highly influence mechanical and physical properties of the manufactured... 相似文献
79.
Assembly lines can be employed successfully in sheltered work centres to better include persons with disabilities in the labour market as well as to improve production efficiency. The optimal assignment of a heterogeneous workforce is known as the assembly line worker assignment and balancing problem (ALWABP). These assembly lines are characterised not only by a heterogeneous workforce, but also by high levels of absenteeism, which makes it more difficult to obtain stable and efficient line balancing solutions. In this paper, an extension of the ALWABP to minimise the expected cycle time under uncertain worker availability is proposed. We model this problem as a two-stage mixed integer program, and propose local search heuristics for solving it. Computational experiments show that stochastic modelling can help to improve the line’s efficiency and that the proposed heuristics produce good results for instances of practical size. 相似文献
80.
F. A. Costa Oliveira H. Reboredo J. Cruz Fernandes 《Materialwissenschaft und Werkstofftechnik》2016,47(9):797-807
Dynamic fatigue of a low dielectric loss steatite was investigated. To this end, the values of n and B, the so‐called subcritical crack growth (SCG) parameters were experimentally determined. The steatite exhibited the expected dynamic fatigue behaviour, so that the stress corrosion susceptibility parameter, n, of 24 was obtained. In addition, the material/environment parameter B, which is a constant for a given test environment, was also attained. These parameters are instrumental in predicting the lifetime of components under stress. When the applied load is such that the resulting strength equals half of the inert strength (σi), defined as the strength of a sample tested in an inert environment or at a fast stress rate, i.e. where no subcritical crack growth occurs, the time to failure (tf) of the material was found to be ~140 h. Measurement of the fracture toughness of steatite is also of upmost importance and so it was determined using three test methods. A value of KIc = 1.91 ± 0.29 MPa m1/2 was attained by the indentation fracture method through measurement of the cracks emanating from the Vickers indentation. This value is in good agreement with those determined using the KIsc (surface crack in flexure) test method (2.21 ± 0.07 MPa m1/2) and fractography analysis test method (2.00 ± 0.44 MPa m1/2). Differences in test procedure and analysis causing the values from each test method to be different are discussed. 相似文献