全文获取类型
收费全文 | 88965篇 |
免费 | 10021篇 |
国内免费 | 5823篇 |
专业分类
电工技术 | 7743篇 |
技术理论 | 6篇 |
综合类 | 7322篇 |
化学工业 | 12593篇 |
金属工艺 | 5114篇 |
机械仪表 | 6209篇 |
建筑科学 | 7480篇 |
矿业工程 | 3271篇 |
能源动力 | 2704篇 |
轻工业 | 6584篇 |
水利工程 | 2234篇 |
石油天然气 | 4160篇 |
武器工业 | 1239篇 |
无线电 | 10841篇 |
一般工业技术 | 8824篇 |
冶金工业 | 3542篇 |
原子能技术 | 1126篇 |
自动化技术 | 13817篇 |
出版年
2024年 | 499篇 |
2023年 | 1603篇 |
2022年 | 3405篇 |
2021年 | 4616篇 |
2020年 | 3365篇 |
2019年 | 2639篇 |
2018年 | 2910篇 |
2017年 | 3252篇 |
2016年 | 2852篇 |
2015年 | 4283篇 |
2014年 | 5112篇 |
2013年 | 5998篇 |
2012年 | 7151篇 |
2011年 | 7260篇 |
2010年 | 6584篇 |
2009年 | 6226篇 |
2008年 | 6091篇 |
2007年 | 5472篇 |
2006年 | 5064篇 |
2005年 | 4233篇 |
2004年 | 2940篇 |
2003年 | 2271篇 |
2002年 | 2337篇 |
2001年 | 2072篇 |
2000年 | 1570篇 |
1999年 | 1210篇 |
1998年 | 669篇 |
1997年 | 599篇 |
1996年 | 560篇 |
1995年 | 454篇 |
1994年 | 318篇 |
1993年 | 281篇 |
1992年 | 232篇 |
1991年 | 145篇 |
1990年 | 121篇 |
1989年 | 82篇 |
1988年 | 76篇 |
1987年 | 48篇 |
1986年 | 50篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1959年 | 13篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Attacks by adult stages of the soft tick Argas (Argas) neghmei (Acari: Argasidae) on inhabitants of the High Andean plateau of Argentina are reported. This is the first local report of this species, which was previously found in the north of Chile. Taxonomic differences between A. (A.) neghmei and other neotropical and exotic species of the genus are underlined. The status of the knowledge about the Argentine argasid fauna is briefly described. 相似文献
2.
3.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
4.
Electromigration reliability of interconnect under bidirectional current stress has been studied in a wide frequency range (mHz to 200 MHz). Experimental results show that the AC lifetime rises with the stress current frequency. The current density exponent and the activation energy of AC lifetime are found to be twice that of DC lifetime. Pure AC current stress failure at extremely high current density is believed to result from thermal migration of metal at hot/cold transition points 相似文献
5.
In this paper, we investigate the problem of determining the optimal bandwidth allocation for a Dynamic Bandwidth Allocation Scheme (DBAS). The objective is to minimize the total amount of bandwidth required to satisfy the Quality of Service (QoS) requirements of all traffic streams. It is shown that when the performance functions satisfy a certain number of conditions, there exists a unique optimal bandwidth allocation such that, for each traffic stream, either its QoS is just satisfied or its QoS is over-satisfied and it is allocated zero bandwidth. Such an allocation is said to be efficient. It is also shown that there exists a unique efficient allocation in the entire feasible region. An iterative algorithm is developed to compute the efficient allocation employing its special properties. Numerical examples are presented to demonstrate how the algorithm works. Future extensions of this work are also discussed.Partially supported by NSERC of Canada through grants OGP14020 and STRIN-200. 相似文献
6.
Fanggao Chang Tao Li Yongxia Ge Zhenping Chen Zhongshi Liu Xiping Jing 《Journal of Materials Science》2007,42(17):7109-7115
DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1−x
Ho
x
)TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1−x
Ho
x
)TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ∼1,300 to ∼4,000), with only a slight increase in the corresponding dielectric loss. The
local electron density and defect concentration estimated using positron annihilation technique conforms well to the features
found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model. 相似文献
7.
Haiquan Guo Shiquan Tao 《IEEE sensors journal》2007,7(3):323-328
Palladium-doped silica nanocomposites were synthesized via a sol-gel technique combined with a template of Triton X-100 micelle. The freshly prepared sol sample of Pd-doped silica nanocomposites was investigated by TEM. Determined from the TEM image, the sizes of the Pd nanoparticles are narrowly distributed, which are around 30 nm in diameter. The prepared sol solution of the sample was injected into a Tygon Microbore Autoanalysis tubing. After 14 days gelatinization, a transparent porous optical fiber was obtained. The response of the fiber to hydrogen gas was tested by using a fiber-optic spectrometric method. The palladium-doped silica nanocomposite fiber is sensitive upon exposure to hydrogen gas and the response is reversible. This palladium-doped silica nanocomposite fiber can be applied as a new kind of hydrogen gas sensor 相似文献
8.
9.
火电厂实施废水零排放的可行性探讨 总被引:1,自引:0,他引:1
对合肥发电厂的用排水现状进行了介绍,并提出了实施废水零排放的可行性方案。 相似文献
10.
石油系油浆与煤系闪蒸油的焦化性能——I.热解条件的影响 总被引:3,自引:2,他引:1
通过偏光显微镜观察了石油系油浆(LH)与煤系闪蒸油(SN)焦化后所得焦块的光学结构。结果表明,在较宽条件下两种原料单独焦化均得不到取向度高的流线型结构。将两种原料以一定比例混合后先热解丙焦化所得焦块的光学结构明显好于二者混合后直接焦化所得焦块的光学结构,其中LH和SN以3:2的重量比混合后在440℃、1MPa下热解3.5h然后再在530℃、1MPa下焦化8h所得焦块为具有较高取向度的流线型结构,适合于作为针状焦的起始原料。 相似文献