全文获取类型
收费全文 | 7808篇 |
免费 | 367篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 159篇 |
综合类 | 21篇 |
化学工业 | 1525篇 |
金属工艺 | 218篇 |
机械仪表 | 402篇 |
建筑科学 | 170篇 |
矿业工程 | 5篇 |
能源动力 | 297篇 |
轻工业 | 605篇 |
水利工程 | 42篇 |
石油天然气 | 21篇 |
无线电 | 1457篇 |
一般工业技术 | 1357篇 |
冶金工业 | 720篇 |
原子能技术 | 89篇 |
自动化技术 | 1102篇 |
出版年
2023年 | 61篇 |
2022年 | 86篇 |
2021年 | 126篇 |
2020年 | 110篇 |
2019年 | 129篇 |
2018年 | 167篇 |
2017年 | 146篇 |
2016年 | 214篇 |
2015年 | 187篇 |
2014年 | 311篇 |
2013年 | 544篇 |
2012年 | 443篇 |
2011年 | 481篇 |
2010年 | 351篇 |
2009年 | 426篇 |
2008年 | 364篇 |
2007年 | 332篇 |
2006年 | 335篇 |
2005年 | 288篇 |
2004年 | 274篇 |
2003年 | 251篇 |
2002年 | 277篇 |
2001年 | 206篇 |
2000年 | 186篇 |
1999年 | 176篇 |
1998年 | 375篇 |
1997年 | 221篇 |
1996年 | 162篇 |
1995年 | 133篇 |
1994年 | 114篇 |
1993年 | 114篇 |
1992年 | 60篇 |
1991年 | 71篇 |
1990年 | 56篇 |
1989年 | 58篇 |
1988年 | 40篇 |
1987年 | 44篇 |
1986年 | 39篇 |
1985年 | 31篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 21篇 |
1974年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有8190条查询结果,搜索用时 15 毫秒
61.
Suk Choo Chung Chang Duck Kong Young Ha Yum 《Journal of Mechanical Science and Technology》1987,1(2):133-139
The dynamic characteristics of the Korean Yi-dynasty bell type structure, including the acoustic effects, are analyzed both theoretically and experimentally. The numerical solutions of natural frequencies and mode shape for membrane and flexural behavior are obtained by using the NASTRAN program for the finite element method with plate shell elements of triangular and quadrilateral types. Test bells, A and B types similar to the Kap-Sa bell in Kong-Ju chosen among typical Korean Yi-dynasty bells, are manufactured on different scales to the original bell. To consider the effects of the variation of the structural dimension on the dynamic response, these bells are analyzed with respect to the variation of the thickness of the wall and the bottom rim and the asymmetric Dang-Jwas. The impact method with the Fast Fourier Transform Analyzer is adopted to experimentally assess the dynamic response. Results are in good agreement with the numerical solutions. 相似文献
62.
PVC/EVA blends were studied with an extrusion plastometer in order to examine the effect of EVA on the processability of PVC. The melt flow of PVC/EVA blends containing from 4 to 30 weight percent EVA follows a simple power law between 160 and 180°C. EVA reduced the melt viscosity and enhanced processability. Blends of PVC and EVA were morphologically incompatible. The molecular weight of extruded PVC in the blends was unchanged. 相似文献
63.
Our laboratory recently published several analytical equations that can be used to predict the melting rate of fully compacted solid polymers sliding on a heated metal surface, modeling the melting mechanism inside an extruder. These equations were obtained by seeking asymptotic solutions to the differential equations describing the melting mechanism, temperature, and shear-dependent viscosity of polymer melts. Following the same asymptotic approach, we successfully developed accompanying analytical equations for predicting the stress required to slide fully compacted solid polymers on a heated metal surface. The accuracy of these analytical stress equations was found to be reasonable, although not fully satisfactory, by comparing their predictions to the experimentally measured values. The accuracy of the stress calculation is directly related to the accuracy of the viscosity values at high shear rates. The consideration of the temperature and shear dependencies of melt viscosity is most important for accurate prediction of the stress, just as it is for the melting rate. The stress not only depends on the melt rheological properties of the polymer but also on the thermodynamic properties. 相似文献
64.
Seng F. Chung 《加拿大化工杂志》1972,50(5):657-662
A mathematical model of a through-circulation dryer is proposed. This model approximates the drying time of constantrate drying and fallingrate drying processes. Based on the proposed model, the optimal drying conditions of maximizing the drying production rate in a continuous through-circulation dryer are obtained. The drying production rate, in terms of the independent operating variables, is a nonlinear objective function, and is optimized under the nonlinear inequality constraint functions by a differential algorithm. 相似文献
65.
Wu-Chun Chung Hung-Pin Lin Shih-Chang Chen Mon-Fong Jiang Yeh-Ching Chung 《Automated Software Engineering》2014,21(4):489-508
As data exploration has increased rapidly in recent years, the datastore and data processing are getting more and more attention in extracting important information. To find a scalable solution to process the large-scale data is a critical issue in either the relational database system or the emerging NoSQL database. With the inherent scalability and fault tolerance of Hadoop, MapReduce is attractive to process the massive data in parallel. Most of previous researches focus on developing the SQL or SQL-like queries translator with the Hadoop distributed file system. However, it could be difficult to update data frequently in such file system. Therefore, we need a flexible datastore as HBase not only to place the data over a scale-out storage system, but also to manipulate the changeable data in a transparent way. However, the HBase interface is not friendly enough for most users. A GUI composed of SQL client application and database connection to HBase will ease the learning curve. In this paper, we propose the JackHare framework with SQL query compiler, JDBC driver and a systematical method using MapReduce framework for processing the unstructured data in HBase. After importing the JDBC driver to a SQL client GUI, we can exploit the HBase as the underlying datastore to execute the ANSI-SQL queries. Experimental results show that our approaches can perform well with efficiency and scalability. 相似文献
66.
In this paper, we investigated an approach for robots to learn to adapt dance actions to human’s preferences through interaction and feedback. Human’s preferences were extracted by analysing the common action patterns with positive or negative feedback from the human during robot dancing. By using a buffering technique to store the dance actions before a feedback, each individual’s preferences can be extracted even when a reward is received late. The extracted preferred dance actions from different people were then combined to generate improved dance sequences, i.e. performing more of what was preferred and less of that was not preferred. Together with Softmax action-selection method, the Sarsa reinforcement learning algorithm was used as the underlining learning algorithm and to effectively control the trade-off between exploitation of the learnt dance skills and exploration of new dance actions. The results showed that the robot learnt, using interactive reinforcement learning, the preferences of human partners, and the dance improved with the extracted preferences from more human partners. 相似文献
67.
Chlorinated isotactic polypropylenes (CPP) having various chlorine contents were blended with poly(ethylene-co-vinyl acetate)s (EVA) having various vinyl acetate (VA) contents. The blends were made by casting films from dilute THF solutions and miscibility of the blends was identified by single glass transition temperature, which was confirmed by DSC and dynamic mechanical measurements. Based on the miscibility data from a large number of CPP/EVA combinations, a miscibility map was depicted where CO equivalent weight (CO-EQW) of EVA was plotted against chlorine equivalent weight (Cl-EQW) of CPP. Though an attractive interaction between CPP and EVA could be detected in all the miscible and immiscible blend pairs, miscibility of the CPP/EVA blends could solely be observed in a relatively narrow range of Cl-EQW ca. 65–100 and CO-EQW ca. 170–230. 相似文献
68.
Kim-Choy Chung 《Behaviour & Information Technology》2014,33(7):743-756
This study investigates perceived risk and trust in relationship to the Diffusion of Innovation Theory [Rogers, E.M., 1962. Diffusion of innovations. Glencoe, IL: The Free Press; 1983. Diffusion of innovations. 3rd ed. New York: The Free Press] from a cultural perspective to understand the determinants of behavioural intent to adopt mobile commerce among the Y Generation in Kazakhstan. Surveys from 345 university-level students and subsequent structural equation modelling revealed perceived risk, trustworthiness and Rogers’ five innovation characteristics are important determinants. Perceived risk and trustworthiness are important determinants because of the high uncertainty avoidance characteristics of the Kazakh society. This study advances theory regarding culture- and generation-based characteristics to transition economies by verifying theoretical proposition regarding the behavioural intent towards mobile commerce adoption, resulting in a greater understanding of mobile commerce adoption among the Y Generation in transition economies. Marketing implications are discussed. 相似文献
69.
O. K. Chung Y. Pomeranz K. F. Finney M. P. Shogren 《Journal of the American Oil Chemists' Society》1978,55(9):635-641
Petroleum ether (PE) extracted 1.00% total free lipids (0.70% nonpolar and 0.30% polar) and 2-propanol (PrOH) extracted 1.36%
total free and bound lipids (0.73% nonpolar and 0.63% polar) from wheat flour; the lipid fractions were characterized by thin
layer chromatography. PE- or PrOH-defatted flours were baked after reconstitution with total, nonpolar, or polar wheat flour
lipids; or with equivalent amounts of nonionic sucrose monopalmitate (SMP), ethoxylated monoglycerides (EMG) — each with a
hydrophile-lipophile balance (HLB) of 14.0 or anionic sodium stearoyl-2-lactylate (SSL) — with an HLB value of 9.0. Defatted
flours supplemented with surfactants alone or in combination with wheat flour lipids were used in bread with no-shortening
and with 3%-shortening. The importance of the polar flour lipids in breadmaking was verified. The lipids in wheat flour were
essential for maximizing the beneficial effects of shortening on breadmaking quality. Nonionic SMP or EMG completely replaced
both PE-extractable wheat flour free total lipids ( or their non-polar or polar fractions) and 3% shortening; nonionic surfactants
with high HLB were better than the anionic SSL for replacing free flour lipids. No surfactant completely replaced unfractionated
PrOH-extracted lipids (free + bound) and shortening or total polar flour lipids (free + bound). All surfactants, especially
anionic SSL, added with PrOH-extracted polar lipids improved the overall bread-making properties of the PrOH-defatted flour
both in the absence and in the presence of shortening.
Presented at the AOCS Meeting, New York, May 1977 相似文献
70.
A personalized service in the ubiquitous environment is to provide services or items, which reflect personal tastes, attitudes, and contexts. It is impossible to reflect the context information generated in u-healthcare environments due to the existing recommendation system performing the recommendation using the information directly input by users and application usage record only. This study develops a context-aware model using the context information provided by the context information model. The study applies it to the extraction of the missing value in a collaborative filtering process. The context-aware model reflects the information that selects items by users according to the appropriate context using the C-HMM and provides it to users. The solution of the missing value in the preference significantly affects the recommendation accuracy in a preference based item supply method. Thus, this study developed a new collaborative filtering for ubiquitous environments by reflecting the missing preference value and reflecting it to the collaborative filtering using the context-aware model. Also, the validity of this method will be evaluated by applying it to menu services in u-healthcare services. 相似文献