全文获取类型
收费全文 | 25846篇 |
免费 | 2451篇 |
国内免费 | 1252篇 |
专业分类
电工技术 | 1454篇 |
技术理论 | 5篇 |
综合类 | 1881篇 |
化学工业 | 4451篇 |
金属工艺 | 1480篇 |
机械仪表 | 1506篇 |
建筑科学 | 1967篇 |
矿业工程 | 761篇 |
能源动力 | 635篇 |
轻工业 | 2787篇 |
水利工程 | 424篇 |
石油天然气 | 1380篇 |
武器工业 | 173篇 |
无线电 | 3136篇 |
一般工业技术 | 2909篇 |
冶金工业 | 1118篇 |
原子能技术 | 233篇 |
自动化技术 | 3249篇 |
出版年
2024年 | 169篇 |
2023年 | 534篇 |
2022年 | 949篇 |
2021年 | 1260篇 |
2020年 | 918篇 |
2019年 | 830篇 |
2018年 | 906篇 |
2017年 | 922篇 |
2016年 | 838篇 |
2015年 | 1116篇 |
2014年 | 1375篇 |
2013年 | 1539篇 |
2012年 | 1721篇 |
2011年 | 1621篇 |
2010年 | 1492篇 |
2009年 | 1421篇 |
2008年 | 1339篇 |
2007年 | 1244篇 |
2006年 | 1215篇 |
2005年 | 982篇 |
2004年 | 748篇 |
2003年 | 940篇 |
2002年 | 1195篇 |
2001年 | 969篇 |
2000年 | 689篇 |
1999年 | 611篇 |
1998年 | 359篇 |
1997年 | 325篇 |
1996年 | 299篇 |
1995年 | 246篇 |
1994年 | 187篇 |
1993年 | 150篇 |
1992年 | 107篇 |
1991年 | 84篇 |
1990年 | 77篇 |
1989年 | 45篇 |
1988年 | 37篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 12篇 |
1959年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
51.
Xin-Ge Fu Ke Shi Jian-Liang Xue Chuan Chen Yu Bai Yan-Lu Qiao Yi-Xuan Liu Xiang-Ming Hu Yu Gao Hao Yu 《石油科学(英文版)》2021,(5):1543-1550
In order to effectively control petroleum hydrocarbon pollution by immobilisation technology,it is necessary to understanding the degradation pathways of petrol... 相似文献
52.
存储虚拟化能够全面提升存储区域网络的服务质量,而带外虚拟化与带内虚拟化相比具有性能高和扩展性好等优点.提出了运用按序操作、REDO日志以及日志完整性鉴别,共同保证带外虚拟化跨越系统崩溃或断电事故后仍旧可用;设计了一种基于关系模型的磁盘上虚拟化元数据组织方式,它具有可读性好和容易修改的优点;给出了通过分析磁盘分区表兼容典型遗留存储系统的有效方法,它具有庞大遗留系统零切割时间的特点.基于上述关键技术实现的原型系统,在典型实验中表现了很好的性能. 相似文献
53.
54.
Tong Gu Zhenghu Tong Xue Zhang Zhiyong Wang Zhen Zhang Tzann-Shun Hwang Lin Li 《International journal of molecular sciences》2022,23(11)
Mn(II)-oxidizing microorganisms are generally considered the primary driving forces in the biological formation of Mn oxides. However, the mechanistic elucidation of the actuation and regulation of Mn oxidation in soilborne bacteria remains elusive. Here, we performed joint multiple gene-knockout analyses and comparative morphological and physiological determinations to characterize the influence of carbon metabolism on the Mn oxide deposit amount (MnODA) and the Mn oxide formation of a soilborne bacterium, Escherichia coli MB266. Different carbon source substances exhibited significantly varied effects on the MnODA of MB266. A total of 16 carbon metabolism-related genes with significant variant expression levels under Mn supplementation conditions were knocked out in the MB266 genome accordingly, but only little effect on the MnODA of each mutant strain was accounted for. However, a simultaneous four-gene-knockout mutant (namely, MB801) showed an overall remarkable MnODA reduction and an initially delayed Mn oxide formation compared with the wild-type MB266. The assays using scanning/transmission electron microscopy verified that MB801 exhibited not only a delayed Mn-oxide aggregate processing, but also relatively smaller microspherical agglomerations, and presented flocculent deposit Mn oxides compared with normal fibrous and crystalline Mn oxides formed by MB266. Moreover, the Mn oxide aggregate formation was highly related to the intracellular ROS level. Thus, this study demonstrates that carbon metabolism acts as a pronounced modulator of MnODA in MB266, which will provide new insights into the occurrence of Mn oxidation and Mn oxide formation by soilborne bacteria in habitats where Mn(II) naturally occurs. 相似文献
55.
Lei Wang Dewei Yang Xiaohan Li Xinyi Zhu Jungang Jiang Yifan Zhang Xue Chen Hongbo Yu 《International journal of molecular sciences》2022,23(12)
Lignin, a by-product of pulping and biorefinery, has great potential to replace petrochemical resources for wastewater purification. However, the defects of lignin, such as severe heterogeneity, inferior reactivity and poor solubility, characterize the production process of lignin-based products by high energy consumption and serious pollution. In this study, several lignin fractions with relatively homogeneous structure were first obtained by organic solvent fractionation, and their structures were fully deciphered by various characterization techniques. Subsequently, each lignin component was custom-valued for wastewater purification based on their structural characteristics. Benefiting from the high reactivity and reaction accessibility, the lignin fraction (lignin-1) refined by dissolving in ethanol and n-butanol could been used as a raw material to produce cationic lignin-based flocculant (LBF) in a copolymerization system using green, cheap and recyclable ethanol as solvent. The lignin fraction (lignin-2) extracted by methanol and dioxane showed low reactivity and high carbon content, which was used to produce lignin-based activated carbon (LAC) with phosphoric acid as activator. Moreover, the influences of synthetic factors on the purification capacity were discussed, and the LBF and LAC produced under the optimal conditions showed distinguished purification effect on kaolin suspension and heavy metal wastewater, respectively. Furthermore, the corresponding purification mechanism and external factors were also elaborated. It is believed that this cleaner production strategy is helpful for the valorization of lignin in wastewater resources. 相似文献
56.
应用于超薄栅氧化CMOS器件的两种电荷泵改进技术的比较 总被引:2,自引:0,他引:2
王庆学 《功能材料与器件学报》2008,14(3):656-662
本文提出了High-low multi-frequency(HLMF)和Average bottom-top-pulse(ABTP)两种电荷泵改进技术,用于提高表征超薄栅氧化CMOS器件界面缺陷的精度.结果表明,在电荷泵技术测量过程中,这两种改进技术能非常有效地扣除漏电流.同时,也分析了电荷泵电流曲线的几个典型特性.由于ABTP技术是用静态模式测量漏电流,所以,在大的负Vbase端,电荷泵电流曲线的尾部出现大的波动.通过比较,我们发现HLMF具有更高的精度,可以作为用于提升表征超薄栅氧化CMOS器件界面缺陷精度的一种重要技术. 相似文献
57.
Weizeng Lv Xue He Haojuan Guo Haibin Lan Yanqing Jiao Le Li Yanhao Lian Zhiqiang Wang Zeyu Xin Yongzhe Ren Tongbao Lin 《International journal of molecular sciences》2022,23(14)
Excessive input of nitrogen fertilizer not only causes a great waste of resources but brings about a series of ecological and environmental problems. Although Small Auxin Up-regulated RNAs (SAURs) participate in diverse biological processes, the function of SAURs in the nitrogen starvation response has not been well-studied. Here, we identified 308 TaSAURs in wheat and divided them into 10 subfamilies. The promoter regions of most TaSAURs contain hormone responsive elements, and their expression levels change under the treatment of different hormones, such as IAA, MeJA, and ABA. Interestingly, overexpression of one of the TaSAUR family members, a nitrogen starvation responsive gene, TaSAUR66-5B, can promote the growth of Arabidopsis and wheat roots. In addition, overexpression of TaSAUR66-5B in Arabidopsis up-regulates the expression levels of auxin biosynthesis related genes, suggesting that overexpression TaSAUR66-5B may promote root growth by increasing the biosynthesis of auxin. Furthermore, overexpression of TaSAUR66-5B in wheat can increase the biomass and grain yields of transgenic plants, as well as the nitrogen concentration and accumulation of both shoots and grains, especially under low nitrogen conditions. This study provides important genomic information of the TaSAUR gene family and lays a foundation for elucidating the functions of TaSAURs in improving nitrogen utilization efficiency in wheat. 相似文献
58.
Chen Xiuqing Ma Kai Geng Deqin Zhai Jingxuan Liu Wei Zhang Hongwei Zhu Tingting Piao Xue 《Wireless Personal Communications》2019,109(3):1747-1767
Wireless Personal Communications - In order to support robust implementation of IoT, many schemes have been done to provide privacy, anonymity, scalability and customizability. Ray et al.’s... 相似文献
59.
60.