全文获取类型
收费全文 | 41709篇 |
免费 | 5965篇 |
国内免费 | 2392篇 |
专业分类
电工技术 | 15771篇 |
技术理论 | 2篇 |
综合类 | 3465篇 |
化学工业 | 1411篇 |
金属工艺 | 1288篇 |
机械仪表 | 4477篇 |
建筑科学 | 1576篇 |
矿业工程 | 990篇 |
能源动力 | 1120篇 |
轻工业 | 709篇 |
水利工程 | 643篇 |
石油天然气 | 907篇 |
武器工业 | 432篇 |
无线电 | 7299篇 |
一般工业技术 | 3631篇 |
冶金工业 | 683篇 |
原子能技术 | 278篇 |
自动化技术 | 5384篇 |
出版年
2024年 | 134篇 |
2023年 | 713篇 |
2022年 | 1038篇 |
2021年 | 1517篇 |
2020年 | 1711篇 |
2019年 | 1328篇 |
2018年 | 1293篇 |
2017年 | 1662篇 |
2016年 | 1713篇 |
2015年 | 2031篇 |
2014年 | 3015篇 |
2013年 | 2609篇 |
2012年 | 3650篇 |
2011年 | 3682篇 |
2010年 | 2658篇 |
2009年 | 2629篇 |
2008年 | 2494篇 |
2007年 | 2828篇 |
2006年 | 2513篇 |
2005年 | 2083篇 |
2004年 | 1669篇 |
2003年 | 1322篇 |
2002年 | 976篇 |
2001年 | 935篇 |
2000年 | 727篇 |
1999年 | 611篇 |
1998年 | 489篇 |
1997年 | 405篇 |
1996年 | 347篇 |
1995年 | 283篇 |
1994年 | 232篇 |
1993年 | 165篇 |
1992年 | 136篇 |
1991年 | 97篇 |
1990年 | 80篇 |
1989年 | 92篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
C. BOULOGNE C. GILLET L. HUGHES R. LE BARS A. CANETTE C.R. HAWES B. SATIAT-JEUNEMAITRE 《Journal of microscopy》2020,280(2):86-103
Up-to-date imaging approaches were used to address the spatiotemporal organisation of the endomembrane system in secretory cells of Dionaea muscipula. Different ‘slice and view’ methodologies were performed on resin-embedded samples to finally achieve a 3D reconstruction of the cell architecture, using ultrastructural tomography, array tomography, serial block face-scanning electron microscopy (SBF-SEM), correlation, and volume rendering at the light microscopy level. Observations of cryo-fixed samples by high-pressure freezing revealed changes of the endomembrane system that occur after trap activation and prey digestion. They provide evidence for an original strategy that adapts the secretory machinery to a specific and unique case of stimulated exocytosis in plant cells. A first secretion peak is part of a rapid response to deliver digestive fluids to the cell surface, which delivers the needed stock of digestive materials ‘on site’. The second peak of activity could then be associated with the reconstruction of the Golgi apparatus (GA), endoplasmic reticulum (ER) and vacuolar machinery, in order to prepare for a subsequent round of prey capture. Tubular continuum between ER and Golgi stacks observed on ZIO-impregnated tissues may correspond to an efficient transfer mechanism for lipids and/or proteins, especially for use in rapidly resetting the molecular GA machinery. The occurrence of one vacuolar continuum may permit continuous adjustment of cell homeostasy. The subcellular features of the secretory cells of Dionaea muscipula outline key innovations in the organisation of plant cell compartmentalisation that are used to cope with specific cell needs such as the full use of the GA as a protein factory, and the ability to create protein reservoirs in the periplasmic space. Shape-derived forces of the pleiomorphic vacuole may act as signals to accompany the sorting and entering flows of the cell. 相似文献
72.
73.
Shoue Chen Sandrayee Brahma Jonathon Mackay Changyong Cao Bahar Aliakbarian 《Journal of food science》2020,85(3):517-525
Food supply chain is a rapidly growing integrated sector and covers all the aspects from farm to fork, including manufacturing, packaging, distribution, storing, as well as further processing or cooking for consumption. Along this chain, smart packaging could impact the quality, safety, and sustainability of food. Packaging systems have evolved to be smarter with integration of emerging electronics and wireless communication and cloud data solutions. Although there are many factors causing the loss and waste issues for foods throughout the whole supply chain of food and there have been several articles showing the recent advances and breakthroughs in developing smart packaging systems, this review integrates these conceptual frameworks and technological applications and focuses on how innovative smart packaging solutions are beneficial to the overall quality and safety of food supply by enhancing product traceability and reducing the amount of food loss and waste. We start by introducing the concept of the management for the integrated food supply chain, which is critical in tactical and operational components that can enhance product traceability within the entire chain. Then we highlight the impact of smart packaging in reducing food loss and waste. We summarize the basic information of the common printing techniques for smart packaging system (sensor and indicator). Then, we discuss the potential challenges in the manufacturing and deployment of smart packaging systems, as well as their cost-related drawbacks and further steps in food supply chain. 相似文献
74.
75.
During the last few decades, photothermal radiometry (PTR) has been greatly developed and widely applied in the field of nondestructive testing. However, the traditional PTR system employs an expensive lock-in amplifier to detect the weak photothermal signal, which leads to high cost and long test time. In this paper, a fast transmission PTR system based on sampling by using an internal computer sound card was developed to lower the system cost and shorter the test time. A piece of amorphous silicon (a:Si) thin film solar cells with artificial defects was prepared and tested by the system. The results show that the sharpened defects can be identified easily and quickly according to the significant peaks of the original infrared signal sampled by the internal computer sound card. Furthermore, more detailed defects can be investigated by processing the infrared signal. These validate the effectiveness of the proposed transmission PTR system as a low cost and efficient non-destructive test technique. 相似文献
76.
77.
78.
VSC-HVDC transmission system is going to become the most economical way of power delivery for large and remote offshore wind farms. An accurate and fast fault detection method is necessary to protect sensitive devices of these systems and maintain uninterrupted power delivery. This paper investigates an innovative technique for recognizing DC zone faults including HVDC cable faults and unbalancing of DC capacitor bank. Sheath voltage is presented as a novel criterion for detecting abnormal situations in the system. Transient voltage of cable sheath and Wavelet transform are used to identify different types of DC faults. Extensive simulation examples are performed on EMTDC–PSCAD platform and post-processed using MATLAB. The results illustrate that the proposed technique gives a robust performance and can be applied to protection scheme of offshore wind farms. 相似文献
79.
80.
动力头是旋挖钻机的关键部件,其性能好坏直接影响钻机整机性能的。文中介绍了TR 180旋挖钻机动力头的结构设计,着重分析了齿轮箱传动系统、滑动支架总成和缓冲装置。 相似文献