全文获取类型
收费全文 | 83945篇 |
免费 | 8099篇 |
国内免费 | 4644篇 |
专业分类
电工技术 | 6255篇 |
技术理论 | 4篇 |
综合类 | 6037篇 |
化学工业 | 12393篇 |
金属工艺 | 5274篇 |
机械仪表 | 6092篇 |
建筑科学 | 6468篇 |
矿业工程 | 2684篇 |
能源动力 | 2518篇 |
轻工业 | 5043篇 |
水利工程 | 1733篇 |
石油天然气 | 4439篇 |
武器工业 | 888篇 |
无线电 | 9902篇 |
一般工业技术 | 9588篇 |
冶金工业 | 4187篇 |
原子能技术 | 1004篇 |
自动化技术 | 12179篇 |
出版年
2024年 | 305篇 |
2023年 | 1248篇 |
2022年 | 2400篇 |
2021年 | 3633篇 |
2020年 | 2620篇 |
2019年 | 2258篇 |
2018年 | 2517篇 |
2017年 | 2645篇 |
2016年 | 2455篇 |
2015年 | 3527篇 |
2014年 | 4523篇 |
2013年 | 5330篇 |
2012年 | 6040篇 |
2011年 | 6602篇 |
2010年 | 5683篇 |
2009年 | 5447篇 |
2008年 | 5576篇 |
2007年 | 5236篇 |
2006年 | 5070篇 |
2005年 | 4244篇 |
2004年 | 3104篇 |
2003年 | 2493篇 |
2002年 | 2297篇 |
2001年 | 1972篇 |
2000年 | 1772篇 |
1999年 | 1553篇 |
1998年 | 1167篇 |
1997年 | 975篇 |
1996年 | 867篇 |
1995年 | 668篇 |
1994年 | 540篇 |
1993年 | 348篇 |
1992年 | 307篇 |
1991年 | 243篇 |
1990年 | 209篇 |
1989年 | 192篇 |
1988年 | 118篇 |
1987年 | 98篇 |
1986年 | 64篇 |
1985年 | 52篇 |
1984年 | 38篇 |
1983年 | 40篇 |
1982年 | 32篇 |
1981年 | 25篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1976年 | 18篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
目前军事领域的信息化建设已经离不开地理信息系统(GIS)的支持。针对地理信息系统的实际应用,立足于军事需求,充分考虑学员特点,将GIS知识与指挥作战知识结合,精心设计了"地理信息系统"的实验内容,通过目标导向型分步骤的实施以及问题导向型学习指导学员学习地理信息系统相关知识,为学员将来使用信息化的应用系统打下了良好的基础。 相似文献
992.
为实现高频数据采集,采用多媒体定时器的方法实现上位机精确定时,同时研究实现了MFC中跨线程窗口类消息传递问题的解决方案。实验表明,定时精度高,达到10毫秒精确定时,不会出现数据丢失,运行良好。 相似文献
993.
Interfacial reaction of highly-branched polyethyleneimine (PEI) with octadecanoic acid (OA) was performed to prepare a series of supramolecular complexes (PEI(OA)x). The complexes at solid state have typical lamellar structure, and the interlamellar distance can be modulated by the OA content. The long period values of the supramolecular complexes measured by SAXS were found to be dependent on the compositions, which are in good consistency with those measured by TEM. For example, the long period values from SAXS for PEI(OA)0.76, PEI(OA)1.03, and PEI(OA)1.67 were 46.5, 62.7, and 56.2 Å, respectively. The corresponding data from TEM were 45.7, 60.7, and 56.6 Å, respectively. A model was proposed for the construction mode of the side alkyl chains (crystallization region) associated with PEI backbone (amorphous region), in which the side alkyl chains were arranged to be ‘end-to-end’ packing for the x=1 complex, while an ‘interdigitated structure’ of the side alkyl chains was deduced for the x>1 and x<1 complexes. Temperature variable FT-IR combination investigation of the scissoring band, rocking band, and stretching band of methylene (CH2) and vibrational band of carbonyl group (CO) indicated that the crystalline form of the crystallization region in the lamellae can be transformed from orthorhombic to hexagonal with the temperature increasing, and vice versa. 相似文献
994.
纳米陶瓷的发展及研究现状 总被引:5,自引:1,他引:5
综述了纳米陶瓷材料近年来的发展与应用,重点论述了纳米陶瓷的制备、性能及应用现状,并对纳米陶瓷的未来发展进行了展望。 相似文献
995.
The direct synthesis of hydrogen peroxide from H2 and O2 using zeolite-supported Au catalysts is described and their activity is contrasted with silica- and alumina-supported Au catalysts. Two zeolites were investigated, ZSM-5 and zeolite Y. The effect of calcination of these catalysts is studied and it is found that for uncalcined catalysts high rates of hydrogen peroxide formation are observed, but these catalysts are unstable and lose Au during use. Consequently, reuse of these catalysts leads to lower rates of hydrogen peroxide formation. However, catalysts calcined at 400 °C are more stable and can be reused without loss of gold. The use of zeolites as a support for Au gives comparable rates of hydrogen peroxide formation to alumina-supported Au catalysts and higher rates when compared with silica-supported catalysts. prepared using a similar method. Zeolite Y-supported catalysts are more active than ZSM-5-supported catalysts for the stable calcined materials. It is considered that the overall activity of these supported catalysts may be related to the aluminium content as the activity increases with increasing aluminium content. 相似文献
996.
997.
Image decomposition refers to the splitting of an image into two or more components.In this paper,a clean image is separated into two parts:one is the cartoon component,consisting only of geometric structure,and the other is the oscillatory component,consisting of texture.Three parts for noisy image are considered:cartoon,texture,and noise.To better decompose an image,we propose two new variational models.In our models,two adaptive regularization terms are introduced.The two regularization terms are determined by an adaptive function which can discriminate the cartoon and texture of an image automatically.Experimental results illustrate the efectiveness of the proposed models for image decomposition. 相似文献
998.
Seong Ik Yoo Tae Yeon Lee Jin‐San Yoon Ik‐Mo Lee Mal‐Nam Kim Han Sup Lee 《应用聚合物科学杂志》2002,83(4):767-776
The interfacial reaction of the polyethylene (PE)/starch blend system containing the reactive compatibilizer maleated polyethylene (m‐PE) was directly characterized by Fourier transform infrared (FTIR) spectroscopy. A significant amount of anhydride groups on m‐PE existed as hydrolyzed forms, resulting in a large amount of carboxyl groups. Using a vacuum‐heating‐cell designed in the laboratory, the carboxyl groups were successfully transformed into the dehydrolyzed state (i.e., anhydride group). This result enabled the direct spectroscopic observation of chemical reaction occurring at the interface. For the PE/starch blend system containing m‐PE, the chemical reaction at the interface was verified by the evolution of ester and carboxyl groups in the FTIR spectra. The effect of the reactive compatibilizer on the interfacial morphology was also examined by scanning electron micrography (SEM). Enhanced interfacial adhesion was clearly observed for the blend system containing reactive compatibilizer. Tensile strengths of blend systems containing m‐PE also increased noticeably compared with the corresponding system without compatibilizer. A similar observation was made for the breaking elongation data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 767–776, 2002 相似文献
999.
1000.
二维码技术已经在社会生活各个领域得到了广泛的应用,由于二维码可以存储多种格式的信息且能够被自动识别,本文基于二维码技术结合公安户口迁移业务,设计并实现了一个基于二维码的户口迁移系统,并且详细分析了系统设计和实现的原理。 相似文献