全文获取类型
收费全文 | 61475篇 |
免费 | 6208篇 |
国内免费 | 3211篇 |
专业分类
电工技术 | 1657篇 |
技术理论 | 2篇 |
综合类 | 4754篇 |
化学工业 | 7475篇 |
金属工艺 | 5620篇 |
机械仪表 | 4053篇 |
建筑科学 | 1437篇 |
矿业工程 | 1799篇 |
能源动力 | 659篇 |
轻工业 | 10803篇 |
水利工程 | 566篇 |
石油天然气 | 1938篇 |
武器工业 | 1012篇 |
无线电 | 7595篇 |
一般工业技术 | 5805篇 |
冶金工业 | 3430篇 |
原子能技术 | 677篇 |
自动化技术 | 11612篇 |
出版年
2024年 | 178篇 |
2023年 | 1060篇 |
2022年 | 1505篇 |
2021年 | 2119篇 |
2020年 | 2042篇 |
2019年 | 1643篇 |
2018年 | 1558篇 |
2017年 | 1926篇 |
2016年 | 2005篇 |
2015年 | 2307篇 |
2014年 | 3243篇 |
2013年 | 3689篇 |
2012年 | 4035篇 |
2011年 | 4403篇 |
2010年 | 3235篇 |
2009年 | 3342篇 |
2008年 | 3199篇 |
2007年 | 3977篇 |
2006年 | 3658篇 |
2005年 | 3156篇 |
2004年 | 2779篇 |
2003年 | 2485篇 |
2002年 | 2050篇 |
2001年 | 1646篇 |
2000年 | 1498篇 |
1999年 | 1155篇 |
1998年 | 996篇 |
1997年 | 943篇 |
1996年 | 786篇 |
1995年 | 645篇 |
1994年 | 606篇 |
1993年 | 531篇 |
1992年 | 444篇 |
1991年 | 330篇 |
1990年 | 370篇 |
1989年 | 305篇 |
1988年 | 202篇 |
1987年 | 120篇 |
1986年 | 104篇 |
1985年 | 130篇 |
1984年 | 94篇 |
1983年 | 91篇 |
1982年 | 79篇 |
1981年 | 57篇 |
1980年 | 43篇 |
1979年 | 30篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1976年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 50 毫秒
71.
《Oil and Energy Trends》2019,44(8):49-53
Values of net oil imports(-)/exports for Austria, Belgium, Denmark, Finland, France, Germany, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, the United Kingdom, Japan, Canada, the United States and Australia. Updated on a monthly basis. Number of imports for Belgium, France, Germany, Greece, Republic of Ireland, Italy, Netherlands, Portugal, Spain, Sweden, the United Kingdom, and Other EU-15 (EU-15), Norway, Poland, Switzerland, Turkey, and Other Europe (OECD Europe), Canada, Chile, Mexico, and the United States (OECD Western Hemisphere), and Australia, Japan, Republic of Korea, New Zealand, (OECD Asia-Pacific), and Total OECED. Current data for Austria, Belgium, Finland, France, Germany, Greece, Italy, Netherlands, Portugal, Spain, Sweden, the United Kingdom, Other EU-15 (EU-15), Czech Republic, Hungary, Poland, Slovakia, Turkey, and Other Europe (OECD Europe), Canada, Mexico, and the United States (OECD Western Hemisphere), Australia, Japan, Republic of Korea, and New Zealand (OECD Asia-Pacific). Updated on a monthly basis. Current data for principal importers of natural gas and the amount in which they import from United States, Republic of Korea, United Kingdom, France, Japan, Italy, Germany and Spain (Table 19.1). Current data for principal exporters of natural gas and the amount they export to Canada, Trinidad and Tobago, the United States, Netherlands, Norway, Russia, Turkmenistan, Qatar, Algeria, Nigeria, Indonesia, Malaysia and Australia (Table 19.2). Updated on a monthly basis. 相似文献
72.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
73.
Prof. Dr.‐Ing. Falk Jaeger 《Mauerwerk》2019,23(1):50-54
Brick masonry is not only a question of building physics, building construction and durability, i.e. sustainability, but has much to do with aesthetics and making sense, which may have been forgotten in modern architecture with its absolute lack of décor. Masonry as an art form has been scarce since the era of brick expressionism. Recently, there have been some exceptions – and thoroughly welcome. The ”Fjordenhus“ in Vejle, Denmark, is an astonishing example. 相似文献
74.
75.
如何在复杂背景下持续有效地检测目标位置,一直是研究者们需要面对的主要挑战。本文在研究红外点状移动目标特征的基础上,根据目标无纹理,无形状的特性,提出一种改进的形态学目标增强算法,并利用目标连续时空不变性检测目标。首先,建立多尺度的图像金字塔,在每层上采用改进的形态学算法快速、粗糙定位小目标。然后进一步的根据目标在时空上的位置相关性,提出基于目标运动特征分析的精确检测方法。得到精确稳定的检测结果。最后实验结果表明与经典的形态学检测算法及其他算法相比,该技术能更有效地检测弱小目标,具有更高的鲁棒性。 相似文献
76.
77.
This paper presents versatile modification of the Wu-Mendel approach for linguistic summarisation and concentrates on eliminating the following main drawbacks of the approach: significant user/expert involvement, significant and rapidly increasing computational cost, some flaws in quality measures formulae. The techniques and formulae proposed to eliminate the aforesaid drawbacks are put through the experimental verification process involving several real-world datasets. The results of the experimental verification demonstrate the increased efficiency and effectiveness of the modified Wu-Mendel approach for linguistic summarisation. 相似文献
79.
80.
The Chinese Remainder Theorem (CRT) explains how to estimate an integer-valued number from the knowledge of the remainders obtained by dividing such unknown integer by co-prime integers. As an algebraic theorem, CRT is the basis for several techniques concerning data processing. For instance, considering a single-tone signal whose frequency value is above the sampling rate, the respective peak in the DFT informs the impinging frequency value modulo the sampling rate. CRT is nevertheless sensitive to errors in the remainders, and many efforts have been developed in order to improve its robustness. In this paper, we propose a technique to estimate real-valued numbers by means of CRT, employing for this goal a Kroenecker based M-Estimation (ME), specially suitable for CRT systems with low number of remainders. Since ME schemes are in general computationally expensive, we propose a mapping vector obtained via Kroenecker products which considerably reduces the computational complexity. Furthermore, our proposed technique enhances the probability of estimating an unknown number accurately even when the errors in the remainders surpass 1/4 of the greatest common divisor of all moduli. We also provide a version of the mapping vectors based on tensorial n-mode products, delivering in the end the same information of the original method. Our approach outperforms the state-of-the-art CRT methods not only in terms of percentage of successful estimations but also in terms of smaller average error. 相似文献