全文获取类型
收费全文 | 15643篇 |
免费 | 1280篇 |
国内免费 | 599篇 |
专业分类
电工技术 | 791篇 |
技术理论 | 1篇 |
综合类 | 1018篇 |
化学工业 | 2578篇 |
金属工艺 | 820篇 |
机械仪表 | 961篇 |
建筑科学 | 1478篇 |
矿业工程 | 459篇 |
能源动力 | 463篇 |
轻工业 | 876篇 |
水利工程 | 250篇 |
石油天然气 | 1072篇 |
武器工业 | 87篇 |
无线电 | 1844篇 |
一般工业技术 | 1973篇 |
冶金工业 | 731篇 |
原子能技术 | 187篇 |
自动化技术 | 1933篇 |
出版年
2024年 | 62篇 |
2023年 | 246篇 |
2022年 | 447篇 |
2021年 | 666篇 |
2020年 | 481篇 |
2019年 | 382篇 |
2018年 | 429篇 |
2017年 | 506篇 |
2016年 | 428篇 |
2015年 | 591篇 |
2014年 | 724篇 |
2013年 | 974篇 |
2012年 | 955篇 |
2011年 | 993篇 |
2010年 | 913篇 |
2009年 | 830篇 |
2008年 | 879篇 |
2007年 | 787篇 |
2006年 | 833篇 |
2005年 | 760篇 |
2004年 | 490篇 |
2003年 | 446篇 |
2002年 | 479篇 |
2001年 | 399篇 |
2000年 | 437篇 |
1999年 | 445篇 |
1998年 | 356篇 |
1997年 | 291篇 |
1996年 | 279篇 |
1995年 | 241篇 |
1994年 | 193篇 |
1993年 | 120篇 |
1992年 | 103篇 |
1991年 | 110篇 |
1990年 | 74篇 |
1989年 | 55篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
81.
Guoxing Zhang Ju’e Guo Guorong Chai Li Gong Xuejun Wang 《Frontiers of Computer Science in China》2010,4(2):263-270
In infrastructure financed projects, in order to attract private investors, host governments often provide some guarantees.
This paper develops a value model of minimum revenue guarantee with multiple-exercise real options under the impact of the
emergency incident. The model is applied to infrastructure financed projects using the minimum revenue guarantee under simulation.
The simulation results indicate that, before quantifying the value of the minimum revenue guarantee, it is necessary to forecast
the jump degree and intensity of the emergency incident, as well as prevent and control risks arising from such emergencies.
Otherwise, underestimation of the guarantee value will occur and the government will have to bear huge debt in this condition.
We also analyze the dependence of the guaranteed value on the minimum guaranteed revenue level, initial revenue and number
of exercise rights. For various conditions, the diagrams of the guaranteed value are also presented. 相似文献
82.
This paper presents a new multi-objective optimization algorithm in which multi-swarm cooperative strategy is incorporated into particle swarm optimization algorithm, called multi-swarm cooperative multi-objective particle swarm optimizer (MC-MOPSO). This algorithm consists of multiple slave swarms and one master swarm. Each slave swarm is designed to optimize one objective function of the multi-objective problem in order to find out all the non-dominated optima of this objective function. In order to produce a well distributed Pareto front, the master swarm is developed to cover gaps among non-dominated optima by using a local MOPSO algorithm. Moreover, in order to strengthen the capability locating multiple optima of the PSO, several improved techniques such as the Pareto dominance-based species technique and the escape strategy of mature species are introduced. The simulation results indicate that our algorithm is highly competitive to solving the multi-objective optimization problems. 相似文献
83.
在分析传统互信息法缺陷的基础上,提出一种基于二次TF*IDF的互信息特征选择算法,对仅在一个类别中出现的特征词的重要程度给予再次的衡量,解决了互信息值相等而无法进行有效特征选择的问题。利用贝叶斯分类器对该方法进行验证的结果表明该算法在文本分类效率和正确率上比原有方法有一定的提高。 相似文献
84.
Lexi Zhang Jianghong Zhao Haiqiang Lu Liming Gong Li Li Jianfeng Zheng Hui Li Zhenping ZhuAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):364
Nanoparticle-assembled ZnO micro-octahedrons were synthesized by a facile homogeneous precipitation method. The ZnO micro-octahedrons are hexagonal wurtzite with high crystallinity. Abundant structure defects were confirmed on ZnO surface by photoluminescence. Gas sensors based on the ZnO micro-octahedrons exhibited high response, selectivity and stability to 1–1000 ppm formaldehyde at 400 °C. Especially, even 1 ppm formaldehyde could be detected with high response (S = 22.7). It is of interest to point out that formaldehyde could be easily distinguished from ethanol or acetaldehyde with a selectivity of about 3. The high formaldehyde response is mainly attributed to the synergistic effect of high contents of electron donor defects (Zni and VO) and highly active oxygen species (O2−) on the ZnO surface. 相似文献
85.
A class of optimal control problems of a system governed by linear dynamic equations on time scales with quadratic cost functional is considered. By the Lebesgue Δ-integral theory and the Sobolev-type space H1 on time scales the weak solution of linear dynamic equations on time scales for both initial value problem and backward problem are introduced, therefore the necessary conditions of optimality are presented. Some typical examples are given for demonstration. 相似文献
86.
87.
88.
89.
Similarity-based image organization and browsing using multi-resolution self-organizing map 总被引:1,自引:0,他引:1
Grant Strong Minglun Gong 《Image and vision computing》2011,29(11):774-786
An algorithm is presented in this paper to facilitate the exploration of large image collections based on visual similarities. Starting with an unordered and unannotated set of images, the algorithm first extracts the salient details into feature vectors using both color and gradient information. The feature vectors are then used to train a self-organizing map which maps high-dimensional feature vectors onto a 2D canvas so that images with similar feature vectors are grouped together. When users browse the image collection, an image collage is generated that selects and displays the most pertinent set of images based on which portion of the 2D canvas is currently in view. Flowing from an overview to details is a seamless operation controlled simply by pan and zoom, with representative images selected in a consistent and predictable way. To make organizing larger image collections practical in interactive time, the organization algorithm is designed to run in parallel on graphics processing units. Overall this paper presents an end-to-end solution that facilitates the surfing of image collections in a fresh way. 相似文献
90.