全文获取类型
收费全文 | 146865篇 |
免费 | 17036篇 |
国内免费 | 11318篇 |
专业分类
电工技术 | 12768篇 |
技术理论 | 5篇 |
综合类 | 14287篇 |
化学工业 | 18990篇 |
金属工艺 | 9447篇 |
机械仪表 | 10809篇 |
建筑科学 | 11952篇 |
矿业工程 | 6081篇 |
能源动力 | 4129篇 |
轻工业 | 13866篇 |
水利工程 | 4203篇 |
石油天然气 | 6016篇 |
武器工业 | 2233篇 |
无线电 | 17153篇 |
一般工业技术 | 13171篇 |
冶金工业 | 5843篇 |
原子能技术 | 2199篇 |
自动化技术 | 22067篇 |
出版年
2024年 | 960篇 |
2023年 | 2716篇 |
2022年 | 6005篇 |
2021年 | 8118篇 |
2020年 | 5850篇 |
2019年 | 4083篇 |
2018年 | 4468篇 |
2017年 | 5209篇 |
2016年 | 4545篇 |
2015年 | 7180篇 |
2014年 | 8903篇 |
2013年 | 10311篇 |
2012年 | 12713篇 |
2011年 | 13076篇 |
2010年 | 12043篇 |
2009年 | 11251篇 |
2008年 | 11190篇 |
2007年 | 10445篇 |
2006年 | 8915篇 |
2005年 | 7144篇 |
2004年 | 4911篇 |
2003年 | 3253篇 |
2002年 | 3023篇 |
2001年 | 2548篇 |
2000年 | 2165篇 |
1999年 | 1192篇 |
1998年 | 547篇 |
1997年 | 469篇 |
1996年 | 404篇 |
1995年 | 324篇 |
1994年 | 255篇 |
1993年 | 196篇 |
1992年 | 141篇 |
1991年 | 126篇 |
1990年 | 95篇 |
1989年 | 89篇 |
1988年 | 64篇 |
1987年 | 41篇 |
1986年 | 32篇 |
1985年 | 20篇 |
1984年 | 24篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 41篇 |
1979年 | 30篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 25篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
2.
应用事故树法对深水井控进行风险评估 总被引:5,自引:0,他引:5
深水井喷事故危害极大,严重时可导致井眼报废、船毁人亡等恶性后果,预防和控制深水井喷是国内外石油界的一个技术难题。文中利用风险树分析引发深水钻井工程事故的顶事件,重点讨论各底事件的相互联系及对系统的影响程度,分析顶事件的发生概率,为最大程度地减少深水井控事故的发生提供理论依据。通过对深水钻井过程中存在的风险进行分析,构建了深水井控风险分析事故树,并对其进行了定性与定量分析。通过风险分析,认为深水井控最主要的影响因素是关井及压井时设备故障、设计方法及操作失误的影响超过安全极限。分析表明,降低基本事件的发生概率对预防井喷作用明显,基本事件发生概率提高1倍,井喷发生概率提高近10倍。针对深水井控过程中存在的风险因素,从工艺、装备及人员要求方面提出了预防深水井喷的措施。 相似文献
3.
4.
Xue‐Bing Zhao Lei Wang De‐Hua Liu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):950-956
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry 相似文献
5.
6.
Young Sil Jeon Jing Lei Ji-Heung Kim 《Journal of Industrial and Engineering Chemistry》2008,14(6):726-731
This study examined the removal of some basic dyes, such as Methylene Blue, Malachite Green and Methyl Orange, using alginate or alginate/polyaspartate composite gel beads. The adsorption of dyes from aqueous solutions at 25 °C was examined using a batch sorption technique. The effects of CaCl2 and the dye concentration on the adsorption were examined. Type-S adsorption isotherms were obtained, which is characteristic of a weak solute–solid interaction. The ionic interaction between the dye molecule and gel matrix appears to be responsible for the efficient adsorption of cationic dyes in this system. These results suggest that an alginate/polyaspartate gel can be used as an effective sorbent for water pollutants such as dyes, and the immobilization of these organic contaminants in the hydrogels from wastewater can solve one of the most important environmental problems in the related industry. 相似文献
7.
根据某雷达系统对测量信号的快速传输要求,提出采用滑动帧的处理方法并在FPGA中实现,克服了传统帧处理难以满足快速传输要求的不足。阐述了滑动帧结构的构造思想,详述了滑动帧结构的特点及具体功能模块的实现。根据实际应用需求构造了滑动帧结构处理器,试验和应用结果表明设计可行有效,能充分满足实时数据传输的要求。 相似文献
8.
9.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
10.
Alia-Klein Nelly; Goldstein Rita Z.; Tomasi Dardo; Zhang Lei; Fagin-Jones Stephanie; Telang Frank; Wang Gene-Jack; Fowler Joanna S.; Volkow Nora D. 《Canadian Metallurgical Quarterly》2007,7(4):735
Reports an error in "What is in a word? No versus Yes differentially engage the lateral orbitofrontal cortex" by Nelly Alia-Klein, Rita Z. Goldstein, Dardo Tomasi, Lei Zhang, Stephanie Fagin-Jones, Frank Telang, Gene-Jack Wang, Joanna S. Fowler and Nora D. Volkow (Emotion, 2007[Aug], Vol 7[3], 649-659). The supplemental materials link should appear as follows: http://dx.doi.org/10.1037/1528-3542.7.3.649.supp. (The following abstract of the original article appeared in record 2007-11660-018.) The words "No" and "Yes" are involved in conditioning to prohibit or encourage behavior, respectively. The authors, therefore, hypothesized that these words would be attributed to endogenous valence, activating neuronal circuits involved with valence and emotional control. Functional MRI (fMRI) at 4 Tesla was used to record regional brain activity while participants were exposed to emphatic vocalizations of the words. Results showed that No and Yes were associated with opposite brain-behavior responses; while No was negatively valenced, produced slower response times, and evoked a negative signal in the right lateral orbitofrontal cortex (OFC), Yes was positively valenced, produced faster response times, and evoked a positive signal in a contiguous region of the OFC. Attribution of negative valence to No and trait anger control were associated with increased responsivity of the OFC to No. Inasmuch as sensitivity to the prohibitive command No develops during childhood through interaction with primary caregivers as the first social objects, our findings may implicate the lateral OFC in the neurobiology of emotion regulation and subsequent social development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献