全文获取类型
收费全文 | 122107篇 |
免费 | 12282篇 |
国内免费 | 7241篇 |
专业分类
电工技术 | 9435篇 |
技术理论 | 8篇 |
综合类 | 9459篇 |
化学工业 | 18421篇 |
金属工艺 | 6963篇 |
机械仪表 | 8221篇 |
建筑科学 | 9776篇 |
矿业工程 | 3606篇 |
能源动力 | 3434篇 |
轻工业 | 8923篇 |
水利工程 | 2778篇 |
石油天然气 | 5715篇 |
武器工业 | 1465篇 |
无线电 | 15256篇 |
一般工业技术 | 13553篇 |
冶金工业 | 5049篇 |
原子能技术 | 1600篇 |
自动化技术 | 17968篇 |
出版年
2024年 | 613篇 |
2023年 | 1978篇 |
2022年 | 4033篇 |
2021年 | 5572篇 |
2020年 | 4027篇 |
2019年 | 3305篇 |
2018年 | 3604篇 |
2017年 | 4066篇 |
2016年 | 3827篇 |
2015年 | 5481篇 |
2014年 | 6566篇 |
2013年 | 7833篇 |
2012年 | 8992篇 |
2011年 | 9567篇 |
2010年 | 8640篇 |
2009年 | 8100篇 |
2008年 | 8002篇 |
2007年 | 7238篇 |
2006年 | 6978篇 |
2005年 | 5963篇 |
2004年 | 4152篇 |
2003年 | 3361篇 |
2002年 | 3542篇 |
2001年 | 2983篇 |
2000年 | 2519篇 |
1999年 | 2122篇 |
1998年 | 1524篇 |
1997年 | 1304篇 |
1996年 | 1201篇 |
1995年 | 1049篇 |
1994年 | 825篇 |
1993年 | 640篇 |
1992年 | 495篇 |
1991年 | 362篇 |
1990年 | 278篇 |
1989年 | 212篇 |
1988年 | 184篇 |
1987年 | 108篇 |
1986年 | 93篇 |
1985年 | 55篇 |
1984年 | 42篇 |
1983年 | 25篇 |
1982年 | 33篇 |
1981年 | 35篇 |
1980年 | 32篇 |
1979年 | 12篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1959年 | 13篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
42.
Colour Centres and Energy Transfer in BaF2-xClx:Eu2+ Phosphors 总被引:1,自引:1,他引:0
The optical absorption spectra of BaF2-xClx:Eu2 after ultraviolet (UV) light excitation were investigated.The differences between the absorption spectra after and before excitation (DAS) were observed.The DAS increase at both the high and the low energy side of F band in BaF2-xClx:Eu2 after 245 nm UV light excitation.The bleach effect of UV light and the absorption of electrons in the valence band may account for the former and the formation of Fa centres (association of F(Cl-) centres), whose absorption band matches the HeNe laser better, may explain the latter.In the write-in process, the transfer of electrons is via tunneling.In the readout process, the transfer of electrons captured in F(F-) and Fa centres is more likely via tunneling, and that of F(Cl-) centres is more likely via conduction band. 相似文献
43.
�Ĵ������Ȼ�����������б�����Դ̽�� 总被引:11,自引:0,他引:11
本文应用天然气中甲烷、乙烷的碳同位素,甲烷的氢同位素,汞含量及天然气成分等指标,探讨了四川盆地天然气成因分类;并结合地质情况对气源层进行了探讨。 相似文献
44.
利用引进的制造技术和设备,制作出了 APT(STLRI)—1.78型系列化光纤连接器。 相似文献
45.
46.
Y. K. Cheung W. G. Jin O. C. Zienkiewicz 《International journal for numerical methods in engineering》1991,32(1):63-78
The application of the Trefftz method for calculating wave forces on offshore structures is presented. Indirect and direct formulations using complete and non-singular systems of Trefftz functions for the Helmholtz equation are posed in this paper. An effective technique using different interpolation functions for the velocity potential and wave force are suggested to improve the computational accuracy of the wave force. The numerical examples show that the present method is highly efficient and accurate. 相似文献
47.
48.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress. 相似文献
49.
50.