全文获取类型
收费全文 | 1299篇 |
免费 | 77篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 395篇 |
金属工艺 | 20篇 |
机械仪表 | 28篇 |
建筑科学 | 32篇 |
矿业工程 | 4篇 |
能源动力 | 36篇 |
轻工业 | 271篇 |
水利工程 | 10篇 |
石油天然气 | 5篇 |
无线电 | 57篇 |
一般工业技术 | 176篇 |
冶金工业 | 226篇 |
原子能技术 | 6篇 |
自动化技术 | 106篇 |
出版年
2023年 | 12篇 |
2022年 | 66篇 |
2021年 | 70篇 |
2020年 | 33篇 |
2019年 | 39篇 |
2018年 | 65篇 |
2017年 | 35篇 |
2016年 | 42篇 |
2015年 | 26篇 |
2014年 | 44篇 |
2013年 | 86篇 |
2012年 | 49篇 |
2011年 | 71篇 |
2010年 | 66篇 |
2009年 | 55篇 |
2008年 | 78篇 |
2007年 | 85篇 |
2006年 | 48篇 |
2005年 | 44篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 20篇 |
2001年 | 19篇 |
2000年 | 8篇 |
1999年 | 21篇 |
1998年 | 45篇 |
1997年 | 33篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1967年 | 3篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有1376条查询结果,搜索用时 14 毫秒
81.
82.
Popescu F Viceconti M Grazi E Cappello A 《Computer methods and programs in biomedicine》2003,71(2):117-127
The present study describes an automatic method to evaluate the efficacy of a computer aided orthopaedic surgery system by comparing the position of the joint implant, as derived from post-operative computed tomography (CT) scans, to that planned by the surgeon before the operation. The method relies on two spatial registrations, one to align the post-operative femur with the pre-operative femur, the second to compute the planned versus achieved (PVA) accuracy as the roto-translation that registers the pre-operative implant position with the post-operative position. Two surface registration algorithms (a generic average distance minimisation and the specialised iterative closest point (ICP) method) were comparatively evaluated first on a set of test cases to measure the absolute accuracy and robustness with respect to peculiar situations such as a distant starting point. The average distance method failed the registration of one test case and showed peak errors of 0.97 degrees on the rotations and 3.09 mm on the translations. The ICP method was found much more efficient and was able to register all test cases. The peak error was 0.44 degrees on the rotations and 0.67 mm on the translations. The ICP method was then used to compute the PVA accuracy on six clinical cases treated with a CT-based planning system in combination with conventional surgical procedures. The method successfully processed all cases demonstrating the efficacy of the proposed procedure in the specific application. 相似文献
83.
Francisco P. Romero Pascual Julián-Iranzo Andrés Soto Mateus Ferreira-Satler Juan Gallardo-Casero 《Language Resources and Evaluation》2013,47(1):151-178
Web 2.0 provides user-friendly tools that allow persons to create and publish content online. User generated content often takes the form of short texts (e.g., blog posts, news feeds, snippets, etc). This has motivated an increasing interest on the analysis of short texts and, specifically, on their categorisation. Text categorisation is the task of classifying documents into a certain number of predefined categories. Traditional text classification techniques are mainly based on word frequency statistical analysis and have been proved inadequate for the classification of short texts where word occurrence is too small. On the other hand, the classic approach to text categorization is based on a learning process that requires a large number of labeled training texts to achieve an accurate performance. However labeled documents might not be available, when unlabeled documents can be easily collected. This paper presents an approach to text categorisation which does not need a pre-classified set of training documents. The proposed method only requires the category names as user input. Each one of these categories is defined by means of an ontology of terms modelled by a set of what we call proximity equations. Hence, our method is not category occurrence frequency based, but highly depends on the definition of that category and how the text fits that definition. Therefore, the proposed approach is an appropriate method for short text classification where the frequency of occurrence of a category is very small or even zero. Another feature of our method is that the classification process is based on the ability of an extension of the standard Prolog language, named Bousi~Prolog , for flexible matching and knowledge representation. This declarative approach provides a text classifier which is quick and easy to build, and a classification process which is easy for the user to understand. The results of experiments showed that the proposed method achieved a reasonably useful performance. 相似文献
84.
Fishbein Harold D.; Eckart Thomas; Lauver Erika; Van Leeuwen Rachel; Langmeyer Daniel 《Canadian Metallurgical Quarterly》1990,82(1):163
Three experiments, presented within the framework of Activity Theory, deal with the relationship between adult learners' questions and subsequent comprehension in a tutorial learning setting. Students were first given verbal instructions (acquisition) to a novel card game and then asked to play one hand with the teacher (implementation). In Experiment 1, there was no correlation between number of questions asked during acquisition and comprehension, but questions during implementation were negatively correlated with comprehension. In Experiment 2, learners whose questions were answered during acquisition scored higher than those whose questions were not answered. In Experiment 3, learners whose questions were answered during implementation showed greater gains in comprehension than those whose questions were answered during acquisition. Individual differences in question-asking during implementation but not acquisition were significantly related to comprehension. The results confirm the view that questions answered during knowledge implementation more effectively aid comprehension than those answered during acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Sowa MG Smith MS Kendall C Bock ER Ko AC Choo-Smith LP Stone N 《Applied spectroscopy》2006,60(8):877-883
Identification and quantification of molecular species are central applications of molecular spectroscopy. In complex multicomponent systems like tissue samples, linear parametric models are often used to estimate the relative concentrations of the biochemical components of the sample. In situations where not all of the components of the sample are known or modeled, such parametric models can suffer from omitted variable bias and result in skewed estimates of component concentrations. We propose a semi-parametric approach that tries to avoid this omitted variable bias by effectively including unknown covariates as a non-parametric term in the regression equation. Constituent concentrations estimated with such partial linear models should outperform strict parametric linear models when the user has limited information on the composition of a multi-constituent system. 相似文献
86.
M. Pilar Vzquez-Tato Julio A. Seijas Francisco Meijide Francisco Fraga Santiago de Frutos Javier Miragaya Juan Ventura Trillo Aida Jover Victor H. Soto Jos Vzquez Tato 《International journal of molecular sciences》2021,22(13)
Lipophilicity of 15 derivatives of sodium cholate, defined by the octan-1-ol/water partition coefficient (log P), has been theoretically determined by the Virtual log P method. These derivatives bear highly hydrophobic or highly hydrophilic substituents at the C3 position of the steroid nucleus, being linked to it through an amide bond. The difference between the maximum value of log P and the minimum one is enlarged to 3.5. The partition coefficient and the critical micelle concentration (cmc) are tightly related by a double-logarithm relationship (), meaning that the Gibbs free energies for the transfer of a bile anion from water to either a micelle or to octan-1-ol differ by a constant. The equation also means that cmc can be used as a measurement of lipophilicity. The demicellization of the aggregates formed by three derivatives of sodium cholate bearing bulky hydrophobic substituents has been studied by surface tension and isothermal titration calorimetry. Aggregation numbers, enthalpies, free energies, entropies, and heat capacities, ΔCP,demic, were obtained. ΔCP,demic, being positive, means that the interior of the aggregates is hydrophobic. 相似文献
87.
Igor Studart Medeiros Erika R. M. Andreeta Antonio C. Hernandes 《Journal of Materials Science》2007,42(11):3874-3877
88.
Antibacterial activity against Escherichia coli of Cu‐BTC (MOF‐199) metal‐organic framework immobilized onto cellulosic fibers 下载免费PDF全文
Haendel S. Rodríguez Juan P. Hinestroza Cristian Ochoa‐Puentes Cesar A. Sierra Carlos Y. Soto 《应用聚合物科学杂志》2014,131(19)
A strong antimicrobial activity against Escherichia coli of Cu‐BTC metal‐organic frameworks immobilized over cellulosic fibers is hereby reported. The in situ synthesis of Cu‐BTC metal‐organic frameworks, aka MOF‐199 or HKUST‐1, onto cellulosic substrates was carried out by exposing carboxymethylated cellulosic substrates to Cu(OAC)2, 1,3,5‐benzenetricarboxylic acid and triethylamine solutions following a very specific order. Using an in vitro model, in accordance to ASTM E2149‐13a, we observed that the cellulose‐MOF system was able to completely eliminate the growth of E. coli on agar plates and liquid cultures. The antibacterial activity of the comprising components of MOF‐199 and the cellulosic substrate was also evaluated and determined to be negligible. Since the method used to synthesize MOF‐199 crystals provides a strong bond between the crystals and the cellulosic substrates, the crystals not detach from the anionic cellulosic fibers allowing the modified textile to be washed and reused hence opening a new avenue to fabricate antibacterial clinical fabrics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40815. 相似文献
89.
McCaslin Shannon E.; Jacobs Gerard A.; Meyer David L.; Johnson-Jimenez Erika; Metzler Thomas J.; Marmar Charles R. 《Canadian Metallurgical Quarterly》2005,36(3):246
The American Red Cross is the largest nongovernmental organization responding to disasters in the United States. This study investigated the impact of negative life change occurring in the year following the September 11, 2001, terrorist attacks on levels of distress among 757 Red Cross Disaster Services Human Resources (national disaster team) employees and volunteers who responded to this disaster. Negative life change in the year following disaster response fully mediated the relationship between disaster response and symptoms of depression and partially mediated the responses between disaster response and posttraumatic stress and anxiety symptoms. Results highlight the importance of life experiences in the year following disaster response and, therefore, the education and follow-up services provided to disaster workers prior to and following disaster assignment. Suggestions for monitoring disaster-related stress during and following assignment are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.