全文获取类型
收费全文 | 3968篇 |
免费 | 364篇 |
国内免费 | 216篇 |
专业分类
电工技术 | 256篇 |
技术理论 | 1篇 |
综合类 | 270篇 |
化学工业 | 777篇 |
金属工艺 | 241篇 |
机械仪表 | 234篇 |
建筑科学 | 264篇 |
矿业工程 | 108篇 |
能源动力 | 79篇 |
轻工业 | 398篇 |
水利工程 | 115篇 |
石油天然气 | 275篇 |
武器工业 | 31篇 |
无线电 | 389篇 |
一般工业技术 | 442篇 |
冶金工业 | 142篇 |
原子能技术 | 46篇 |
自动化技术 | 480篇 |
出版年
2024年 | 14篇 |
2023年 | 67篇 |
2022年 | 156篇 |
2021年 | 217篇 |
2020年 | 151篇 |
2019年 | 128篇 |
2018年 | 110篇 |
2017年 | 130篇 |
2016年 | 111篇 |
2015年 | 190篇 |
2014年 | 194篇 |
2013年 | 234篇 |
2012年 | 278篇 |
2011年 | 257篇 |
2010年 | 253篇 |
2009年 | 252篇 |
2008年 | 260篇 |
2007年 | 248篇 |
2006年 | 208篇 |
2005年 | 153篇 |
2004年 | 119篇 |
2003年 | 144篇 |
2002年 | 155篇 |
2001年 | 130篇 |
2000年 | 94篇 |
1999年 | 95篇 |
1998年 | 42篇 |
1997年 | 33篇 |
1996年 | 30篇 |
1995年 | 26篇 |
1994年 | 25篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 2篇 |
排序方式: 共有4548条查询结果,搜索用时 15 毫秒
1.
Fenqi Du Dongmei Yang Yue Sun Yang Jiao Feng Teng Haibo Fan 《Ceramics International》2021,47(4):4963-4971
Ultrawide band gap semiconductor materials have attracted considerable attention in recent years owing to their great potential in the photocatalytic field. In this study, Zn-doped Ga2O3 nanofibers with various concentrations were synthesized via electrospinning; they exhibited a superior photocatalytic degradation performance of rhodamine B dye compared to that of undoped Ga2O3 nanofibers. The Zn dopant replaced Ga sites via replacement doping, which could increase the concentration of oxygen vacancies and lead to enhanced photocatalytic properties. When the Zn concentration increased, a Ga2O3/ZnGa2O4 hybrid structure formed, which could further enhance the photocatalytic performance. The separation of photogenerated carriers due to Zn doping and heterojunctions were the primary causes of the enhanced photocatalytic performance. This study provides experimental data for the fabrication of high-performance photocatalysts based on Ga2O3 nanomaterials. 相似文献
2.
3.
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth. 相似文献
4.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献
5.
PP-g-AA的制备和表征 总被引:6,自引:0,他引:6
用熔融接枝方法制备了聚丙烯-g-丙烯酸(PP-g-AA)。用光电子能谱,广角X射线衍射,红外光谱和化学滴定方法对接枝物进行了定性和定量表征。讨论了单体和引发剂浓度对接枝率的影响,确定了用红外光谱法测定接枝物含量的经验公式 相似文献
6.
7.
Reorganisation and evolution of class hierarchies is important for object-oriented system development and has received considerable attention in the literature. The contributions of this paper are: (1) a formal study of a set of extension relations and transformations on class hierarchies; (2) a presentation of a small set of primitive transformations which form a minimal and complete basis for the extension relations; and (3) an analysis of the impact of these transformations at the object level.The study leads to a better understanding of evolution and reuse of object-oriented software and class hierarchies. It also provides a terminology and a means of classification for design reuse. The theory presented in this paper is based on the Demeter data model, which gives a concise mathematical foundation for classes and their inheritance and part-of relationships. Parts of the theory have been implemented in the Demeter System
TM
C++, a CASE tool for object-oriented design and programming. 相似文献
8.
9.
10.
介绍了一套基于微机局域网的ICF综合实验数据采集和处理系统,从基本物理实验需求的分析到系统软硬件的选择,物理测试节点的入网和实验数据的共享和管理等方面阐述了其整个建立过程,给出了实用系统的结构和其应用情况。 相似文献