全文获取类型
收费全文 | 64879篇 |
免费 | 5971篇 |
国内免费 | 3244篇 |
专业分类
电工技术 | 3806篇 |
技术理论 | 3篇 |
综合类 | 4792篇 |
化学工业 | 10559篇 |
金属工艺 | 3193篇 |
机械仪表 | 3933篇 |
建筑科学 | 5057篇 |
矿业工程 | 1636篇 |
能源动力 | 1830篇 |
轻工业 | 5333篇 |
水利工程 | 1292篇 |
石油天然气 | 3686篇 |
武器工业 | 484篇 |
无线电 | 7373篇 |
一般工业技术 | 7671篇 |
冶金工业 | 2788篇 |
原子能技术 | 830篇 |
自动化技术 | 9828篇 |
出版年
2024年 | 318篇 |
2023年 | 1096篇 |
2022年 | 2032篇 |
2021年 | 2659篇 |
2020年 | 2066篇 |
2019年 | 1824篇 |
2018年 | 1908篇 |
2017年 | 2271篇 |
2016年 | 2008篇 |
2015年 | 2660篇 |
2014年 | 3338篇 |
2013年 | 3991篇 |
2012年 | 4194篇 |
2011年 | 4542篇 |
2010年 | 3953篇 |
2009年 | 3733篇 |
2008年 | 3753篇 |
2007年 | 3446篇 |
2006年 | 3484篇 |
2005年 | 2859篇 |
2004年 | 2027篇 |
2003年 | 2054篇 |
2002年 | 2223篇 |
2001年 | 1954篇 |
2000年 | 1556篇 |
1999年 | 1573篇 |
1998年 | 1134篇 |
1997年 | 950篇 |
1996年 | 949篇 |
1995年 | 738篇 |
1994年 | 629篇 |
1993年 | 488篇 |
1992年 | 356篇 |
1991年 | 247篇 |
1990年 | 206篇 |
1989年 | 174篇 |
1988年 | 175篇 |
1987年 | 112篇 |
1986年 | 78篇 |
1985年 | 51篇 |
1984年 | 47篇 |
1983年 | 33篇 |
1982年 | 37篇 |
1981年 | 22篇 |
1980年 | 32篇 |
1979年 | 24篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Ming Yang Lei Wang Guanghua Li Lei Yang Zhan Shi Shouhua Feng 《Journal of Alloys and Compounds》2007,440(1-2):57-61
The hydrothermal reaction of 2,5-pyridinedicarboxylic acid (H2PDC), diethylene triamine and In(NO3)3·4.5H2O gave rise to a two-dimensional (2D) coordination polymer In(OH)(2,5-PDC). This compound crystallizes in the orthorhombic space group Iba2, with cell parameters, a = 12.656(3) Å, b = 20.114(4) Å, c = 6.2216(1) Å, V = 1583.9(5) Å3 and Z = 8. Its structure contains one-dimensional In–O–In–O– chains, which are further linked by 2,5-PDC ligands into a 2D supramolecular neutral framework. The adjacent 2D layers are parallel with each other and construct a three-dimensional framework via hydrogen bands. At room temperature, the compound exhibits intense photoluminescence. On the basis of the results of TG/DTA analyses, the structure is thermally stable up to 390 °C. 相似文献
93.
WCDMA的MBMS技术 总被引:2,自引:0,他引:2
主要介绍了基于WCDMA的MBMS技术,给出了其网络架构和技术难点,并对其应用给无线网络带来的影响作了一定深度的探讨。 相似文献
94.
95.
不同压力下气层岩样m、n值变化的实验研究 总被引:1,自引:0,他引:1
胶结指数m和饱和度指数n变化规律的研究一直是岩石物理学家和测井解释分析家关注的问题。压力是影响m、n的重要因素,但迄今为止,仍未取得可使多数人接受的一般性结论。实验开展了低孔隙度低渗透率气层岩样在不同压力条件下的电阻率测量,在考虑孔隙度随压力变化的基础上建立了m、n参数随压力变化的关系,得出结论:某些地区的气层岩样在压力增大时即使考虑孔隙度变化,m值增大,n值减小。 相似文献
96.
Densitometry determination of dioxins using gold nanoparticlemodified dioxin response element probes
Li-Fan Zhao Li Li Yu-Qiu Gao Bo-Sheng Li Yuan-Yuan Li Chang-Hua Shi Tian Chen Wen-Jie Yang Xiao-Bo Li Shun-Qing Xu 《Gold bulletin》2007,40(4):305-309
This study aims to develop a rapid and sensitive densitometry bioassay of dioxins. It is known that dioxin ligand can bind
heterodimeric aryl hydrocarbon receptor (AhR) and trigger the formation of the complex of dioxin-AhR, AhR nuclear translocator
(Arnt), and dioxin-responsive element (DRE). We have established a rapid and sensitive method using nanoparticle-modified
DRE probes based on dioxin-dependent binding of DRE to AhR complex. Dioxins can trigger the binding of nanoparticle-modified
DRE probe to AhR complex. The nanoparticle-modified DRE probes in the dioxin-AhR-Arnt-DRE complexes immobilized on the microplates
were detected by measuring optical density after silver enhancement. Results showed that as little as 0.01 pM of TCDD could
be detected. Dioxins could be quantified accurately with the linear range from 1 nM to 0.01 pM. The coefficient of variation
was 5≈8% in this bioassay. The optical density of nanoparticle-based silver enhancement was produced in a dose- and time-
dependent manner. The dioxin concentrations in fly ash samples determined by this bioassay were comparable with that by the
standard HRGC/HRMS. Thus this bioassay is a sensitive and convenient cell-free bioassay of dioxin that is suitable for screening
of dioxins in environmental or food matrices. 相似文献
97.
Ying Bai Yanfeng Yin Na Liu Bingkun Guo Hongjun Shi Jianyong Liu Zhaoxiang Wang Liquan Chen 《Journal of power sources》2007
As the continuance of our series study on LiCoO2 surface modification, the complicated traditional surface coating method is replaced with simple addition of amorphous YPO4 and Al2O3 in commercial LiCoO2 or in commercial electrolyte based on our understanding to the improvement mechanism of surface modification. Comprehensive studies by X-ray photoelectron spectroscopy (XPS), gas chromatography and mass spectroscopy (GC–MS), inductively coupled plasma (ICP) and Fourier transformed infrared (FTIR) indicate that the products of spontaneous reaction between the additive and the LiPF6 based electrolyte are responsible for the performance improvements. 相似文献
98.
99.
Stephen Shaoyi Liao Huai Qing Wang Qiu Dan Li Wei Yi Liu 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(3):660-671
This paper presents a new method for learning Bayesian networks from functional dependencies (FD) and third normal form (3NF) tables in relational databases. The method sets up a linkage between the theory of relational databases and probabilistic reasoning models, which is interesting and useful especially when data are incomplete and inaccurate. The effectiveness and practicability of the proposed method is demonstrated by its implementation in a mobile commerce system. 相似文献
100.