全文获取类型
收费全文 | 24288篇 |
免费 | 3226篇 |
国内免费 | 2590篇 |
专业分类
电工技术 | 1318篇 |
技术理论 | 5篇 |
综合类 | 3081篇 |
化学工业 | 1126篇 |
金属工艺 | 624篇 |
机械仪表 | 1276篇 |
建筑科学 | 1683篇 |
矿业工程 | 593篇 |
能源动力 | 425篇 |
轻工业 | 1244篇 |
水利工程 | 657篇 |
石油天然气 | 1562篇 |
武器工业 | 263篇 |
无线电 | 2925篇 |
一般工业技术 | 1473篇 |
冶金工业 | 426篇 |
原子能技术 | 236篇 |
自动化技术 | 11187篇 |
出版年
2024年 | 100篇 |
2023年 | 319篇 |
2022年 | 593篇 |
2021年 | 626篇 |
2020年 | 739篇 |
2019年 | 614篇 |
2018年 | 643篇 |
2017年 | 766篇 |
2016年 | 861篇 |
2015年 | 979篇 |
2014年 | 1423篇 |
2013年 | 1411篇 |
2012年 | 1758篇 |
2011年 | 1970篇 |
2010年 | 1593篇 |
2009年 | 1737篇 |
2008年 | 1822篇 |
2007年 | 2072篇 |
2006年 | 1740篇 |
2005年 | 1520篇 |
2004年 | 1254篇 |
2003年 | 1000篇 |
2002年 | 813篇 |
2001年 | 607篇 |
2000年 | 518篇 |
1999年 | 430篇 |
1998年 | 343篇 |
1997年 | 265篇 |
1996年 | 254篇 |
1995年 | 232篇 |
1994年 | 220篇 |
1993年 | 152篇 |
1992年 | 137篇 |
1991年 | 83篇 |
1990年 | 75篇 |
1989年 | 72篇 |
1988年 | 33篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 42篇 |
1984年 | 36篇 |
1983年 | 32篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 17篇 |
1976年 | 8篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
In a graph theory model, clustering is the process of division of vertices into groups, with a higher density of edges within groups than between them. In this paper, we introduce a new clustering method for detecting such groups and use it to analyse some classic social networks. The new method has two distinguished features: non-binary hierarchical tree and the feature of overlapping clustering. A non-binary hierarchical tree is much smaller than the binary-trees constructed by most traditional methods and, therefore, it clearly highlights meaningful clusters which significantly reduces further manual efforts for cluster selections. The present method is tested by several bench mark data sets for which the community structure was known beforehand and the results indicate that it is a sensitive and accurate method for extracting community structure from social networks. 相似文献
65.
Luis Garcés-Erice 《Parallel Computing》2011,37(8):379-391
The software in modern systems has become too complex to make accurate predictions about their performance under different configurations. Real-time or even responsiveness requirements cannot be met because it is not possible to perform admission control for new or changing tasks if we cannot tell how their execution affects the other tasks already running. Previously, we proposed a resource-allocation middleware that manages the execution of tasks in a complex distributed system with real-time requirements. The middleware behavior can be modeled depending on the configuration of the tasks running, so that the performance of any given configuration can be calculated. This makes it possible to have admission control in such a system, but the model requires knowledge of run-time parameters. We propose the utilization of machine-learning algorithms to obtain the model parameters, and be able to predict the system performance under any configuration, so that we can provide a full admission control mechanism for complex software systems. In this paper, we present such an admission control mechanism, we measure its accuracy in estimating the parameters of the model, and we evaluate its performance to determine its suitability for a real-time or responsive system. 相似文献
66.
单苯环氯取代指数法预测二噁类化合物PCDDs的正辛醇/水分配系数 总被引:1,自引:0,他引:1
采用单苯环氯取代指数作为氯代二苯并二口恶口英类化合物 (PCDDs)的分子结构描述符 ,通过正向逐步线性回归方法建立了PCDDs的logKow与分子结构描述符之间的定量关系模型。与文献报道的MOD模型相比 ,该模型不仅具有显著的相关性 (n =43,Radj=0 898,SE =0 195 ,在α =0 0 5时 ,F =2 0 45 5 ,p =0 0 0 0 0 ) ,而且对于分子结构具有更好的区分能力。利用建立的模型 ,对没有logKow文献值的其他 33种PCDDs化合物给出了预测值 相似文献
67.
The antioxidant -tocopherol (vitamin E), applied in a basal trunk band to the green ash tree,Fraxinus pennsylvanica var.subintergerrinia, elicited an alteration of foliar feeding byMalacosoma disstria larvae (Lepidoptera: Lasiocampidae). The bioassayed effects were dependent on the dosage of elicitor, the time after elicitation, and the position in the tree. Leaves for chemical analysis were collected from trees receiving two dosages and at two intervals after elicitation. Compounds in the ethyl acetate extractables from the ash tree leaves were separated by TLC and HPLC. TLC separations showed differences in the nonhydrolyzed extractables attributable to elicitor dosage and time after elicitation. TLC-resolved differences were also evident among acid-hydrolyzed samples. HPLC-resolved profiles revealed eight peaks in the nonhydrolyzed extractables that were quantitatively negatively correlated with larval feeding preference between elicited versus control foliage on at least one of the two sampling dates. Results from this study and other investigations reported in the literature indicate that the antioxidant-tocopherol (vitamin E) can function as an environmental-stress elicitor of alterable defensive chemistry in green ash and other plants. 相似文献
68.
This paper presents a novel global localization approach for mobile robots by exploring line-segment features in any structured environment. The main contribution of this paper is an effective data association approach, the Line-segment Relation Matching (LRM) technique, which is based on a generation and exploration of an Interpretation Tree (IT). A new representation of geometric patterns of line-segments is proposed for the first time, which is called as Relation Table. It contains relative geometric positions of every line-segment respect to the others (or itself) in a coordinate-frame independent sense. Based on that, a Relation-Table-constraint is applied to minimize the searching space of IT therefore greatly reducing the processing time of LRM. The Least Square algorithm is further applied to estimate the robot pose using matched line-segment pairs. Then a global localization system can be realized based on our LRM technique integrated with a hypothesis tracking framework which is able to handle pose ambiguity. Sufficient simulations were specially designed and carried out indicating both pluses and minuses of our system compared with former methods. We also presented the practical experiments illustrating that our approach has a high robustness against uncertainties from sensor occlusions and extraneous observation in a highly dynamic environment. Additionally our system was demonstrated to easily deal with initialization and have the ability of quick recovery from a localization failure. 相似文献
69.
宁夏寒冷地区骨干渠道砌护技术研究 总被引:2,自引:0,他引:2
对宁夏灌区骨干渠道砌护情况进行了调查,分析了渠道结构破坏的形式、部位与程度,并对不同边坡砌护结构、渠底砌护结构和防渗、保温、排水方式的组合进行了试验研究。提出了适合寒冷地区的骨干渠道砌护三类模式:现浇混凝土坡脚、预制混凝土板坡脚、格宾石笼坡脚。选用砌护结构形式,要先确定渠身地下水位变化范围、边坡地质岩性、挖方渠道周围水环境,还要兼顾工程投资能力。 相似文献
70.
梅水燕 《武汉化工学院学报》2006,28(6):60-62
文学艺术教育在人格修养方面具有内涵的丰富性,层次的兼容性,方式的独特性。因此,文学艺术教育对人格修养方面起着可贵的辅助作用,它是思想道德课所代替不了的人格修养课程。 相似文献