全文获取类型
收费全文 | 23519篇 |
免费 | 2374篇 |
国内免费 | 934篇 |
专业分类
电工技术 | 461篇 |
综合类 | 1881篇 |
化学工业 | 8355篇 |
金属工艺 | 738篇 |
机械仪表 | 716篇 |
建筑科学 | 2299篇 |
矿业工程 | 898篇 |
能源动力 | 684篇 |
轻工业 | 2366篇 |
水利工程 | 824篇 |
石油天然气 | 1718篇 |
武器工业 | 75篇 |
无线电 | 1119篇 |
一般工业技术 | 1782篇 |
冶金工业 | 1528篇 |
原子能技术 | 334篇 |
自动化技术 | 1049篇 |
出版年
2024年 | 131篇 |
2023年 | 407篇 |
2022年 | 730篇 |
2021年 | 827篇 |
2020年 | 922篇 |
2019年 | 776篇 |
2018年 | 726篇 |
2017年 | 842篇 |
2016年 | 892篇 |
2015年 | 895篇 |
2014年 | 1319篇 |
2013年 | 1500篇 |
2012年 | 1803篇 |
2011年 | 1661篇 |
2010年 | 1344篇 |
2009年 | 1376篇 |
2008年 | 1205篇 |
2007年 | 1459篇 |
2006年 | 1389篇 |
2005年 | 1145篇 |
2004年 | 928篇 |
2003年 | 782篇 |
2002年 | 712篇 |
2001年 | 531篇 |
2000年 | 425篇 |
1999年 | 386篇 |
1998年 | 271篇 |
1997年 | 222篇 |
1996年 | 194篇 |
1995年 | 152篇 |
1994年 | 116篇 |
1993年 | 103篇 |
1992年 | 95篇 |
1991年 | 80篇 |
1990年 | 74篇 |
1989年 | 52篇 |
1988年 | 44篇 |
1987年 | 60篇 |
1986年 | 45篇 |
1985年 | 58篇 |
1984年 | 52篇 |
1983年 | 26篇 |
1982年 | 22篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1957年 | 4篇 |
1955年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
针对双河油田的注采结构的现状及特征,通过近几年来在注采结构调整方面的实践与应用,总结出了油田在特高含水后期开发阶段,实现油田控水稳油目标的途径和方法,注水结构调整主要是结合地质特点,减少欠注层段,减少和控制不合理超注井层段和改善吸水剖面;在采液结构调整上,控制高含水层段的注入,加强中低渗透层段的注入,封堵高渗透、高水淹干扰层段,解放动用较差的中低渗透层段,改善平面上采出不平衡的状况。通过实施注采结构调整,双河油田在特高含水后期实现了高效开发。 相似文献
13.
Occupational airway diseases are now receiving attention in industry, although study is hampered by a lack of readily-available data. The interpretation of the data that is available, and also of the root problems themselves, is itself a difficult problem. This paper has been written as a literature review which it is hoped that other researchers can take either as a starting point or as a refresher. 相似文献
14.
15.
T. A. Hall 《Journal of microscopy》1991,164(1):67-79
When a microregion in a thin section of frozen-dried and embedded tissue is analysed by the conventional electron-probe X-ray continuum-normalization method, the measured quantity is in mmol of element per kg of embedded specimen. As each microregion contains an unknown amount of embedding medium, this quantity generally lies indeterminately somewhere within the wide range between mmol of element per kg of hydrated tissue and mmol of element per kg of dehydrated tissue. However, if a ‘tag’ element is incorporated in the embedding medium, the contribution of the medium to the local continuum count in each probed field should be measurable, and the X-ray data may then unambiguously yield mmol of element per kg of dehydrated tissue. This result should not be affected by shrinkage on freeze-drying or by incomplete replacement of water by embedding medium. The same X-ray data can additionally provide estimates of mmol of element per unit volume, mmol of element per kg of hydrated tissue and local dry-mass fraction. However, these estimates are subject to errors due to tissue shrinkage, incomplete replacement of water and beam damage. 相似文献
16.
17.
M. Lipow 《Quality and Reliability Engineering International》1985,1(1):27-35
This paper presents a demonstration of a methodology for fault removal during software development. The methodology encompasses the entire development history, from system and software requirements generation to system test. Thus it considers not only the faults during software testing after formal configuration controls have been invoked, but also the faults discovered prior to that phase: during system and software requirements generation, preliminary design, detailed design and code and unit testing. The agents for fault discovery used in verification and validation are called activities, techniques and tools (AT & Ts) in this paper, each having a certain maximum potential or capability for fault discovery. The AT & Ts considered include the usual specification review activities, and also certain tools not normally applied in ‘standard’ software development, such as automated requirements aids. Application of the methodology yields numbers of residual faults as of each phase of development, including those remaining to be discovered during operations and maintenance. Some previous experience and data on residual faults correspond to these results, indicating that the methodology and choice of parameters are reasonable. The methodology also allows one to calculate a relative loss due to delay in fault discovery, which, as is well known, rises rapidly when faults are not discovered during the phase in which they are generated. 相似文献
19.
Injun Lee Taeseong Jung Junggi Kim Suho Ro Chulsu Kim Yeji Lee Youngmi Kim Juhyun Lee Misook Kang 《Journal of Industrial and Engineering Chemistry》2008,14(6):869-873
This study focuses on the relationship between photo-catalytic performance and optical property over Si-incorporated TiO2. The Si-incorporated TiO2 particles exhibited a pure structure of anatase having a particle size of less than 20 nm and surface area of more than 190 m2/g. The absorbance did not shift to a higher wavelength in spite of the incorporation of the Si ions, but the intensity of the photoluminescence (PL) curve was the smallest in the case of the 2.0 mol% Si-TiO2, which was related to the recombination between the excited electrons and holes. Based on these results, the photodecomposition of methyl orange in the liquid reaction was enhanced over the 2.0 mol% Si-incorporated TiO2 compared with that over pure TiO2: Methyl orange at 10.0 ppm was completely decomposed after 100 min when 1.0 g of the 2.0 mol% Si-incorporated TiO2 was used. 相似文献
20.
P. M. Solozhenkin E. A. Deliyanni V. N. Bakoyannakis A. I. Zouboulis K. A. Matis 《Journal of Mining Science》2003,39(3):287-296
The original method is developed for producing the new inorganic sorption material of akaganeite bgr-FeO(OH). The material in question is characterized relative to arsenic contained in aqua. The possibility is established for removing arsenate ions from water by contemporary physicochemical methods. 相似文献