首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   688篇
  免费   25篇
  国内免费   2篇
电工技术   11篇
综合类   1篇
化学工业   245篇
金属工艺   19篇
机械仪表   16篇
建筑科学   31篇
矿业工程   3篇
能源动力   37篇
轻工业   77篇
水利工程   4篇
无线电   27篇
一般工业技术   98篇
冶金工业   24篇
原子能技术   1篇
自动化技术   121篇
  2024年   12篇
  2023年   13篇
  2022年   48篇
  2021年   82篇
  2020年   28篇
  2019年   41篇
  2018年   36篇
  2017年   37篇
  2016年   47篇
  2015年   28篇
  2014年   38篇
  2013年   88篇
  2012年   28篇
  2011年   32篇
  2010年   29篇
  2009年   26篇
  2008年   10篇
  2007年   2篇
  2006年   14篇
  2004年   5篇
  2003年   4篇
  2002年   1篇
  2001年   4篇
  2000年   3篇
  1999年   2篇
  1998年   6篇
  1997年   3篇
  1995年   1篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1990年   1篇
  1988年   1篇
  1987年   5篇
  1985年   5篇
  1984年   4篇
  1983年   3篇
  1982年   5篇
  1981年   4篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   3篇
  1975年   3篇
  1967年   1篇
排序方式: 共有715条查询结果,搜索用时 15 毫秒
81.
Predicting customer decisions allows companies to obtain higher profits due to better resource management. The accuracy of those predictions can be currently boosted by the application of machine learning algorithms.

We propose a new method to predict a car driver’s decision about taking a replacement car after a vehicle accident happens. We use feature engineering to create attributes of high significance. The generated attributes are related to time (e.g., school holidays), place of collision (e.g., distance from home), time and conditions (e.g., weather), vehicles (e.g., vehicle value), addresses of both the victim and the perpetrator. Feature engineering involves external sources of data.

Five machine learning methods of classification are considered: decision trees, multi-layer perceptrons, AdaBoost, logistic regression and gradient boosting. Algorithms are tested on real data from a Polish insurance company. Over 80% accuracy of prediction is achieved. Significance of the attributes is calculated using the linear vector quantization method.

Presented work shows the applicability of machine learning in the car insurance market.  相似文献   

82.
Guidelines and instructions for Environmental Impact Assessment and Strategic Environmental Assessment (together referred to as EA here) are developed to improve the quality of legal requirements’ implementation and to support EA procedure accomplishment. However, to date, it has not been checked whether they are useful for practitioners. Therefore, the aim of the study underlying this paper was to verify, based on the experience of Polish EA experts, whether guidelines and instructions are useful in their everyday work. A qualitative study comprising of a questionnaire survey and interviews tested whether (1) EA practitioners know and use the Polish and EU guidelines, (2) how EA practitioners evaluate the validity and usefulness of such instructions, and (3) in which areas there is a lack of instructions and guidelines. The results show a low level of knowledge of national and EU handbooks. Those guidelines focusing on legal procedures, road investments and designing animal passageways are considered to be the most useful. Moreover, practitioners indicate that EU guidelines should be translated into Polish. Most important for practitioners is the linking of guidelines with the EA procedure, so that they can become a platform for dialogue of all stakeholders.  相似文献   
83.
84.
In the present work, the Mg2Cu precipitates in copper-alloyed austempered ductile iron (ADI) were identified by analyzing techniques such as TEM and SEM with EDS. It was revealed that, in castings made of ADI-containing copper, highly dispersed particles of Mg2Cu are formed, whose size does not exceed <1 μm. The research work was carried out on ductile iron that was austenitized at 900 °C, followed by austempering at 380 °C. The microstructure was investigated using various techniques, including optical microscopy, XRD, SEM, and TEM. In addition to this, the exhibited impact properties of castings with Cu, Ni, and Cu+Ni were also determined. This study casts a new light on the formation of the structure of Cu-alloyed ADI. The highly-dispersive and brittle Mg2Cu particles that are located in the vicinity of the graphite nodules have a negative effect on the impact properties of ADI. It has also been shown that impact strength decreases from levels of 160-180 J (for copper-free ADI) to 90-120 J (for copper-and copper-nickel-alloyed ADI).  相似文献   
85.
With the modern tools of metrology we can measure almost all variables in the phenomenon field of a working machine, and some of measuring quantities can be symptoms of machine condition. On this basis we can form the symptom observation matrix for condition monitoring. From the other side we know that contemporary complex machines can have many modes of failure/damage, so called faults. The paper presents the method of extraction of fault information from the symptom observation matrix by means of singular value decomposition, in the form of generalized fault symptoms. However, at the beginning of monitoring we do not know the sensitivity of potential symptoms to the given machine faults and to its overall condition. Hence, some method of symptom observation matrix optimization leading to redundancy minimization is presented first time in this paper. This gives the possibility to assess the diagnostic contribution of every primary measured symptom. Also in the paper some possibility to assess symptom limit value, based on symptom reliability is considered. These concepts are illustrated by symptom observation matrix processing with the special program and the data are taken directly from the machine vibration condition monitoring area.  相似文献   
86.
The adsorption kinetics of platinum(IV) chloride complex ions on the activated carbon Norit GF40 was investigated. Experiments were carried out at different initial concentrations of Pt(IV) chloride complex ions, temperature, rate of mixing and pH. It was found that the value of activation energy of the studied process is equal to 19.7 kJ/mol. From the ICP MS analysis it was confirmed that platinum ions (Pt(IV) and Pt(II)) are removed from the solution due to the adsorption and are further reduced to the metallic state. Such mechanism was confirmed by XPS analysis which showed that on the carbon surface three forms of platinum species, i.e. Pt(0), Pt(II) and Pt(IV), exist. The presence of platinum in the solution at different oxidation states was also confirmed spectrophotometrically by identification of their characteristic absorption bands. The metallic form of Pt present on the surface of activated carbon was observed in the form of small spherical islands with the diameter not exceeding 500 nm. Those islands consist of smaller, flake-shape particles with a thickness of about 35 nm.  相似文献   
87.
    
The performance of the present‐day scanning electron microscopy (SEM) extends far beyond delivering electronic images of the surface topography. Oxide dispersion strengthened (ODS) steel is on of the most promising materials for the future nuclear fusion reactor because of its good radiation resistance, and higher operation temperature up to 750°C. The microstructure of ODS should not exceed tens of nm, therefore there is a strong need in a fast and reliable technique for their characterization. In this work, the results of low‐kV SEM characterization of nanoprecipitates formed in the ODS matrix are presented. Application of highly sensitive photo‐diode BSE detector in SEM imaging allowed for the registration of single nm‐sized precipitates in the vicinity of the ODS alloys. The composition of the precipitates has been confirmed by TEM‐EDS.  相似文献   
88.
    
This paper proposes a computationally effective framework for load‐dependent optimal sensor placement in large‐scale civil engineering structures subjected to moving loads. Two common problems are addressed: selection of modes to be monitored and computational effectiveness. Typical sensor placement methods assume that the set of modes to be monitored is known. In practice, determination of such modes of interest is not straightforward. A practical approach is proposed that facilitates the selection of modes in a quasi‐automatic way based on the structural response at the candidate sensor locations to typical operational loads. The criterion used to assess sensor placement is based on Kammer's Effective Independence (EFI). However, in contrast to typical implementations of EFI, which treat the problem as a computationally demanding discrete problem and use greedy optimization, an approach based on convex relaxation is proposed. A notion of sensor density is applied, which converts the original combinatorial problem into a computationally tractable continuous optimization problem. The proposed framework is tested in application to a real tied‐arch railway bridge located in central Poland.  相似文献   
89.
The paper presents an attempt to develop a probabilistic model for predicting an annual number of storm overflow discharges. Forecasting the occurrence of an overflow discharge event involved the application of the logistic regression, which does not require the development of complex hydrodynamic catchment models. The performed calculations showed that the logistic regression model can be successfully used to evaluate the performance of the emergency overflow weir. The resultant logit model eliminates the necessity to develop hydrodynamic models, to conduct continuous measurements of the flow intensity in the stormwater drainage system and to collect detailed information on the characteristics of the subcatchments within the analyzed catchment. The hydrodynamic model was used to simulate the annual number of discharges. The analysis of the results demonstrated that they are in the range of stochastic values, which indicates an application-related character of the method.  相似文献   
90.
    
Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in numerous products, from which they are emitted to the environment, including house dust. House dust is a source of human exposure to these compounds by ingestion. The aim of this article was to determine the levels of selected PBDEs in the house dust and indicate their potential sources of origin. PBDE congeners: BDE‐47, BDE‐99, BDE‐153 and BDE‐209, were analyzed in 129 samples. The geometric mean levels (and 95% CIs) of the aforementioned congeners amounted to 3.8 (3.1–4.7) ng/g, 4.5 (3.5–5.6) ng/g, 2.2 (2.1–2.4) ng/g and 345 (269–442) ng/g respectively. BDE‐209 was the dominant congener in the majority of tested samples. We found a statistically significant correlation between the concentrations of BDE‐47 and the computer operating time per day (rs – 0.18) and the living area (rs – 0.20). Statistically significant higher levels of BDE‐99 were found in homes where the floor was not replaced during the last 2 years.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号