全文获取类型
收费全文 | 28187篇 |
免费 | 3057篇 |
国内免费 | 1288篇 |
专业分类
电工技术 | 1638篇 |
技术理论 | 5篇 |
综合类 | 2027篇 |
化学工业 | 4840篇 |
金属工艺 | 1631篇 |
机械仪表 | 1743篇 |
建筑科学 | 2159篇 |
矿业工程 | 838篇 |
能源动力 | 754篇 |
轻工业 | 2977篇 |
水利工程 | 489篇 |
石油天然气 | 1564篇 |
武器工业 | 204篇 |
无线电 | 3353篇 |
一般工业技术 | 3240篇 |
冶金工业 | 1233篇 |
原子能技术 | 294篇 |
自动化技术 | 3543篇 |
出版年
2025年 | 10篇 |
2024年 | 507篇 |
2023年 | 669篇 |
2022年 | 1064篇 |
2021年 | 1410篇 |
2020年 | 1043篇 |
2019年 | 900篇 |
2018年 | 981篇 |
2017年 | 1001篇 |
2016年 | 935篇 |
2015年 | 1221篇 |
2014年 | 1516篇 |
2013年 | 1684篇 |
2012年 | 1871篇 |
2011年 | 1771篇 |
2010年 | 1627篇 |
2009年 | 1557篇 |
2008年 | 1470篇 |
2007年 | 1329篇 |
2006年 | 1316篇 |
2005年 | 1070篇 |
2004年 | 833篇 |
2003年 | 1001篇 |
2002年 | 1225篇 |
2001年 | 1004篇 |
2000年 | 709篇 |
1999年 | 650篇 |
1998年 | 395篇 |
1997年 | 344篇 |
1996年 | 318篇 |
1995年 | 264篇 |
1994年 | 209篇 |
1993年 | 155篇 |
1992年 | 111篇 |
1991年 | 96篇 |
1990年 | 85篇 |
1989年 | 49篇 |
1988年 | 39篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1965年 | 1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 31 毫秒
61.
Nina Xue Tingting Du Fangfang Lai Jing Jin Ming Ji Xiaoguang Chen 《International journal of molecular sciences》2022,23(10)
The extracellular heat shock protein 90α (eHSP90α) has been reported to promote cancer cell motility. However, whether pancreatic cancer (PC) cells expressed membrane-bound or secreted HSP90α, as well as its underlying mechanism for PC progression, were still unclear. Our study demonstrated that the amounts of secreted HSP90α proteins were discrepant in multiple PC cells. In addition, highly invasive Capan-2 cells have a higher level of secreted HSP90α compared with those of less invasive PL45 cells. The conditioned medium of Capan-2 cells or recombinant HSP90α treatment stimulated the migration and invasion of PC cells, which could be prevented with a neutralizing anti-HSP90α antibody. Furthermore, secreted HSP90α promoted elements of epithelial–mesenchymal transition in PL45 cells, including increases in vimentin and Snail expressions, decreases in E-cadherin expression, and changes in cell shape towards a mesenchymal phenotype, but these phenomena were reversed by the anti-HSP90α antibody in Capan-2 cells. In addition, high levels of low-density lipoprotein receptor-related protein 1 (LRP1) were associated with worsened patient survival in pancreatic adenocarcinoma. We demonstrated LRP1 as a receptor of eHSP90α for its stimulatory role in metastasis, by activating the AKT pathway. In addition, silencing LRP1 enhanced the chemosensitivity to gemcitabine and doxorubicin in Capan-2 cells. Therefore, our study indicated that blocking secreted HSP90α underlies an aspect of metastasis and chemoresistance in PC. 相似文献
62.
63.
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
64.
新时期下,我国高层建筑数量不断增多,而且建筑物仍然在向超高层、超大面积的方向发展,这给消防防火和安全管理工作提出了比较高的要求。高层建筑与多层建筑和单层建筑在结构上存在比较大的不同,必须要制定一套符合高层建筑实际需求的防火方法,全面加强消防安全监管力度,这样才能确保高层建筑的防火安全性。文章在简要分析高层建筑火灾特征,以及高层建筑消防安全现状的基础上,提出了几点有关防火安全管理的策略。 相似文献
65.
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
66.
Formationcrossectionsofnucleiwith(n,2n)reactionsChenXueShi,XieKuanZhong,ZhouShengMo,YanQingQuan(ShanghaiInstituteofNucle... 相似文献
67.
68.
GaN nanorods have been successfully grown on Si (111) substrates by magnetron sputtering through ammoniating Ga2O3 thin films catalyzed with Mo. The influence of the ammoniating time on the growth of GaN nanorods was analyzed, in particular,
by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Fourier transform infrared (FT-IR) spectrometer, scanning electron
microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectrum. The results
demonstrate that the GaN nanorods are single crystal with hexagonal wurtzite structure, which have high crystalline quality.
The GaN nanorods after ammoniation at 1223 K (950 °C) for 20 minutes have good emission properties and the highest crystalline
quality with 100- to 200-nm diameter and several-micron length. The growth direction of these nanorods is along the orientation
of (100) crystal plane. A small red shift occurs because of the band-gap change caused by the tensile stress of the one-dimensional
GaN nanorods along the axial direction. 相似文献
69.
Photocatalysts with perovskites for hydrogen production from aqueous solution were reviewed. Among the most of metal oxide photocatalysts, the family of ABO3 Perovskite-type oxide shows higher photocatalytie activity, especially alkaline earth titanate and alkali tantalate. Therein, sodium tantalate showed the highest activity for water splitting. The reasons for the high photocatalytic activity of ABO3 perovskties are considered to the diverse and flexible crystal structure. The photocatalytic activity of ABO3 perovskties can be improved by doping other element at A site, B site or O site and loading CO-catalysts such as NiO and Pt. In this paper, the mechanism of photocatalytic water splitting, the structure of ABO3 perovsktie, and Perovskite-type photocatalysts were reviewed. 相似文献
70.
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