全文获取类型
收费全文 | 57652篇 |
免费 | 5968篇 |
国内免费 | 3756篇 |
专业分类
电工技术 | 4635篇 |
技术理论 | 1篇 |
综合类 | 4931篇 |
化学工业 | 7860篇 |
金属工艺 | 3546篇 |
机械仪表 | 3816篇 |
建筑科学 | 4539篇 |
矿业工程 | 1909篇 |
能源动力 | 1529篇 |
轻工业 | 5643篇 |
水利工程 | 1604篇 |
石油天然气 | 2170篇 |
武器工业 | 655篇 |
无线电 | 6382篇 |
一般工业技术 | 5888篇 |
冶金工业 | 2437篇 |
原子能技术 | 885篇 |
自动化技术 | 8946篇 |
出版年
2024年 | 333篇 |
2023年 | 1025篇 |
2022年 | 2011篇 |
2021年 | 2837篇 |
2020年 | 2024篇 |
2019年 | 1559篇 |
2018年 | 1604篇 |
2017年 | 1910篇 |
2016年 | 1654篇 |
2015年 | 2454篇 |
2014年 | 2945篇 |
2013年 | 3543篇 |
2012年 | 4136篇 |
2011年 | 4572篇 |
2010年 | 4203篇 |
2009年 | 3899篇 |
2008年 | 3908篇 |
2007年 | 3843篇 |
2006年 | 3465篇 |
2005年 | 3023篇 |
2004年 | 2115篇 |
2003年 | 1565篇 |
2002年 | 1452篇 |
2001年 | 1348篇 |
2000年 | 1207篇 |
1999年 | 866篇 |
1998年 | 645篇 |
1997年 | 512篇 |
1996年 | 538篇 |
1995年 | 443篇 |
1994年 | 368篇 |
1993年 | 283篇 |
1992年 | 226篇 |
1991年 | 186篇 |
1990年 | 135篇 |
1989年 | 116篇 |
1988年 | 103篇 |
1987年 | 82篇 |
1986年 | 49篇 |
1985年 | 37篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 20篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1959年 | 11篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
11.
Conventional cancer therapies, the second leading cause of death worldwide, result in serious side effects and, at best, merely extend the patient''s lifespan by a few years. Searching for effective prevention is of high priority in both basic and clinical sciences. In recent decades natural products have been considered to be an important source of cancer chemopreventive agents. Red wine polyphenols, which consisted of various powerful antioxidants such as flavonoids and stilbenes, have been implicated in cancer prevention and that promote human health without recognizable side effects. Since resveratrol, a major component of red wine polyphenols, has been studied and reviewed extensively for its chemopreventive activity to interfere with the multi-stage carcinogenesis, this review focuses on recent progress in studies on cancer chemopreventive activities of red wine polyphenol extracts and fractions as well as other red wine polyphenols, like procyanidin B5 analogues and myricetin. 相似文献
12.
13.
14.
A step-up/down single-phase AC-to-DC power converter without current sensor is proposed to achieve high performance and simple control logic. The power converter adopts a front-end diode rectifier so that only one active switch is required. The familiar state-space averaging technique for discontinuous mode DC-to-DC power converters is extended to model the proposed AC-to-DC converter. Unlike the existing model, which is valid only for a very low frequency range, namely below line frequency, the proposed model is applicable up to half switching frequency. The design of the controller is detailed. Selected experimental results are presented to verify the proposed theory 相似文献
15.
16.
17.
Freeman G. Lukaszek W. Pan Y.Y.C. 《Semiconductor Manufacturing, IEEE Transactions on》1993,6(4):306-317
An approach to computer-aided interpretation of parametric test data for integrated circuit process-problem diagnosis is presented. In contrast to a conventional expert system, which reasons with a knowledge base consisting of rules acquired from human experts, the system presented centers its knowledge around analytic device equations. By using equations as the basis of the system knowledge, a more universal, well-organized, and concise level of knowledge is encoded. With the use of objects to present this knowledge, a great deal of useful information outside that described by only the symbolic expressions can be represented, and extension to qualitative or numeric models should be straightforward. The result is an expressive, well-organized, easily built, and easily maintained knowledge base. The authors describe the system's interactive graphical displays and the automatic data interpretation algorithms. Examples evaluating n-channel metal oxide semiconductor (NMOS) parameter variations, interconnect parameter variations, and interconnect yields are used for illustration 相似文献
18.
The hydrogenation of diene‐based polymers via diimide is a very attractive alternative to the conventional catalytic hydrogenation route based on gaseous molecular hydrogen. However, serious crosslinking always accompanies it and limits the end‐use properties of the polymers. Gel formation in polymers that are hydrogenated via diimide has been investigated in detail through an inspection of all the chemical reactions involved in the process. The results indicate that hydrogen peroxide decomposition, some reactions related to oxygen, and the redox reaction between hydrogen peroxide and hydrazine are capable of generating radicals. However, radicals generated in the aqueous phase do not appear to initiate the crosslinking of diene‐based polymers in the latex form. It is proposed that the primary radicals giving rise to crosslinking are generated in the polymer phase in situ, and the step responsible for generating these organic radicals is possibly the diimide disproportionation reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1122–1125, 2005 相似文献
19.
分析了南阳石蜡精细化工厂直馏柴油碱洗乳化的原因,介绍了该厂直馏柴油碱洗抗乳化措施,这些措施包括:优化操作参数,加强生产管理,深度碱洗柴油轻组分然后轻、重组分混合出厂。这些措施的综合应用彻底解决了南阳石蜡精细化工厂直馏柴油碱洗乳化的问题,又保证了柴油收率。 相似文献
20.
研制的环氧-聚氨酯互穿网络(IPN)防腐蚀涂料具有优异的防腐蚀性能和附着力。介绍了该涂料的制法。列举了IPN涂层的性能指标。讨论了影响涂层性能的各种因素。 相似文献