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31.
In most industrialized countries, the end of the Cold War marked a change in focus from preparedness for war to an increasing focus on civil society's own vulnerability and safety. To meet new threats and changing risks, there is also a need for new analytical concepts. Societal safety is a concept developed in Norway during the last decade. It could be defined as: ‘The society's ability to maintain critical social functions, to protect the life and health of the citizens and to meet the citizens' basic requirements in a variety of stress situations’. It aims to be a systematic approach for understanding, mitigating and responding to social problems such as extraordinary stresses and losses, interferences in complex and mutual dependent systems, or lack of trust in vital social institutions. Future threats to society are not limited to specific sectors or areas, but stem from complex interactions amongst economic, technological, social and cultural factors. Thus, the main challenges to improve societal safety will be the ability to coordinate, organize and assign clear roles to different actors at the international, national and local levels. Societal safety has interfaces with other safety‐related areas such as national security, sustainable development, human security and incident management (handling of isolated accidents, common illness and ordinary criminal acts). Societal safety is, however, a sensitive political issue containing dilemmas and value choices that are hardly possible to perceive or solve as pure scientific problems. 相似文献
32.
It is well known that horizontal surfaces of high strength concrete (HSC) are susceptible to cracking in the time before and
during setting. It appears that there are two critical time periods for such cracking: An early period ranging from placing
to an hour or two, and a late period that covers the setting time and early hardening. The latter is considered here. In this
period, the cracking risk may be assessed from the ratio between strain (the volume change) and tensile strain capacity, or
from the ratio between stress generated from the volume change at restraint, and the tensile strength. All these parameters
were measured. It is shown that relatively moderate volume changes of HSC-surfaces caused by drying plus cooling, generate
restraining stress that may exceed the tensile strength, and thus, generate failure. The results indicate that crack risk
assessment from stress/strength is more reliable than using strain/strain capacity. The starting point of tensile strength
evolution of hardened concrete seems to coincide fairly well with the initial setting time. Also, the tensile strain capacity
reaches a low level at this point, but continues descending for another hour or more. 相似文献
33.
An overall model for maintenance optimization 总被引:1,自引:0,他引:1
This paper presents an approach for identifying the optimal maintenance schedule for the components of a production system. Safety, health and environment objectives, maintenance costs and costs of lost production are all taken into consideration, and maintenance is thus optimized with respect to multiple objectives. Such a global approach to maintenance optimization requires expertise from various fields, e.g., decision theory, risk analysis and reliability and maintenance modelling. Further, a close co-operation between management, maintenance personnel and analysts is required to achieve a successful result. In the past this has been a major obstacle to the extensive use of proper maintenance optimization methods in practice, and techniques to promote the communication between the involved parties of the optimization process is an essential element in the suggested approach. A simple step by step presentation of the required modelling is provided. Contrary to most current methods of RCM (Reliability Centered Maintenance), the approach is based on an analytic model, and therefore gives a sound framework for carrying out a proper maintenance optimization. The approach is also flexible as it can be carried out at various levels of detail, e.g., adopted to available resources and to the managements willingness to give detailed priorities with respect to objectives on safety vs production loss. 相似文献
34.
An executable subset of VDM-SL in an SA/RT framework 总被引:2,自引:2,他引:0
In this article we present the executable specification language IPTES Meta-IV based on the formal specification language VDM-SL. The language has been fitted to work in an SA/RT framework and the article presents how it supports the specification of the data transformation part of SA/RT. Furthermore we present some of the advanced constructs of the language seen as an executable specification language in its own right. Finally we present how an IPTES Meta-IV interpreter is used in combination with a high-level timed Petri net executor to execute SA/RT models. 相似文献
35.
A. K. Dahle P. A. Tøndel C. J. Paradies L. Arnberg 《Metallurgical and Materials Transactions A》1996,27(8):2305-2313
The effect of grain refinement on the fluidity of AlSi7Mg and AlSi11Mg has been investigated by spiral tests. Two different
types of grain refiners have been evaluated. An AlTi5Bl master alloy was added to different Ti contents. Since the commercial
alloys had a high initial content of titanium, model alloys were made to investigate the fluidity at low grain refiner additions.
Commercial alloys grain refined only by boron additions have also been investigated. The results from the fluidity measurements
have been verified by measuring the dendrite coherency point of the different cast alloys. Although different, the two methods
show similar trends. The spirals from each fraction grain refiner cast were subsequently investigated metallographically at
the tip of the spirals and at a reference point a distance behind, but no obvious difference in structure was observed. For
both alloys, an increase in fluidity is observed as the content of grain refiner increases above 0.12 pct Ti, while the fluidity
is impaired with increased grain refinement below 0.12 pct Ti. The alloys grain refined with ~0.015 pct B show the highest
fraction solid at dendrite coherency, the smallest grain size, and the best fluidity. 相似文献
36.
Abstract This study deals with the modeling of air pollution in apartments from laboratory measurements of source strengths, using formaldehyde and Total Volatile Organic Compounds (TVOCs) as model pollutants. The sources in two test apartments were grouped into two: building-related sources and occupant-related sources. The measured source strengths and ventilation rates were used for the prediction of concentrations expected in the apartments. These predictions were compared to measurements in the apartment over 12 months. The conclusions were that the model predictions based on emission rates measured in the laboratory can be used to predict the long-term concentration of the two model pollutants in the apartments. Considering the measured differences in ventilation between the apartments, an occupant emission rate of between 0.2 and 0.3 mg/h/kg body weight could be estimated. Based on previous suggested limits of acceptable exposures of humans to VOCs, an acceptable average emission rate of VOCs from building materials in general was estimated to be about 30 (μ/m2/h. The modeling showed that during the first 200 days, building materials dominated the emissions. After this, sources relating to the occupants dominated. On average about half of the VOC pollution originated from the building materials. 相似文献
37.
Jeffrey E. Marchese Matteo Cirillo Niels Grøch-Jensen 《Open Systems & Information Dynamics》2007,14(2):189-196
We present evidence for a close analogy between the nonlinear behaviour of a pulsed microwave-driven Josephson junction at
low temperature and the experimentally observed behaviour of Josephson systems operated below the quantum transition temperature
under similar conditions. We specifically address observations of Ramsey-type fringe oscillations, which can be understood
in classical nonlinear dynamics as results of slow transient oscillations in a pulsed microwave environment. Simulations are
conducted to mimic experimental measurements by recording the statistics of microwave-induced escape events from the anharmonic
potential well of a zero-voltage state. Observations consistent with experimentally obtained Ramsey-type oscillations are
found in the classical model.
An erratum to this article can be found at 相似文献
38.
39.
The estimation of the Direction-Of-Arrival (DOA) and the variance of the angular spread, using an array of sensors in the
case of a Ricean channel is considered, using the Maximum-Likelihood, Least-Squares and Weighted Least Squares criteria. The
Cramér-Rao bound is also obtained for the problem of interest. Simplification of the cost functions to reduce the dimension
of the problem has been carried out and the performance of the methods has been studied based on numerical experiments.
A major part of the work was carried out when K V S Hari was visiting the Department of Signals, Sensors and Systems during
Jul–Sep 1995, on leave from the Indian Institute of Science 相似文献
40.
A study compares two methods of reading text-based content on mobile phones: traditional scroll-based reading and Rapid Serial Visual Presentation, which displays words rapidly in a sequence. University students used a prototype called Feedo to test both methods, and their reading comprehension, efficiency, and preference ratings were measured. The results show that efficiency increases with fast RSVP, comprehension is equal, and preference rating is lower than with self-paced scroll. 相似文献