全文获取类型
收费全文 | 109628篇 |
免费 | 9087篇 |
国内免费 | 4681篇 |
专业分类
电工技术 | 6466篇 |
技术理论 | 9篇 |
综合类 | 7473篇 |
化学工业 | 18705篇 |
金属工艺 | 6498篇 |
机械仪表 | 6883篇 |
建筑科学 | 9522篇 |
矿业工程 | 3303篇 |
能源动力 | 3090篇 |
轻工业 | 6778篇 |
水利工程 | 2080篇 |
石油天然气 | 6184篇 |
武器工业 | 893篇 |
无线电 | 11857篇 |
一般工业技术 | 12935篇 |
冶金工业 | 5425篇 |
原子能技术 | 1274篇 |
自动化技术 | 14021篇 |
出版年
2024年 | 479篇 |
2023年 | 1892篇 |
2022年 | 3153篇 |
2021年 | 4354篇 |
2020年 | 3403篇 |
2019年 | 2779篇 |
2018年 | 3250篇 |
2017年 | 3625篇 |
2016年 | 3155篇 |
2015年 | 4152篇 |
2014年 | 5283篇 |
2013年 | 6349篇 |
2012年 | 7016篇 |
2011年 | 7443篇 |
2010年 | 6415篇 |
2009年 | 6135篇 |
2008年 | 5987篇 |
2007年 | 5613篇 |
2006年 | 5877篇 |
2005年 | 5127篇 |
2004年 | 3527篇 |
2003年 | 3195篇 |
2002年 | 3082篇 |
2001年 | 2712篇 |
2000年 | 2793篇 |
1999年 | 3042篇 |
1998年 | 2439篇 |
1997年 | 1982篇 |
1996年 | 2055篇 |
1995年 | 1651篇 |
1994年 | 1326篇 |
1993年 | 937篇 |
1992年 | 774篇 |
1991年 | 613篇 |
1990年 | 450篇 |
1989年 | 372篇 |
1988年 | 302篇 |
1987年 | 201篇 |
1986年 | 136篇 |
1985年 | 96篇 |
1984年 | 61篇 |
1983年 | 39篇 |
1982年 | 48篇 |
1981年 | 39篇 |
1980年 | 24篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1965年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.
Yang Lüyun 《中国稀土学报(英文版)》2006,24(Z2)
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm. 相似文献
102.
二硫代磷酸硫化氧钼与硫,磷添加剂的复配特性研究 总被引:1,自引:0,他引:1
研究了二烷基二硫代磷酸硫化氧钼(MoDTP)摩擦改进剂及其与硫、磷、硫-磷型添加剂复合的抗磨减摩性能。试验表明,经过适当复配后,这类合活性元素的添加剂对MoDTP的抗磨减摩性能均有增效作用,同一类型添加剂的活性愈高,增效作用愈显著。同时利用扫描电镜和X-射线能谱仪进行摩擦副表面膜的形貌照相及元素分析,对复合作用的机理进行了初步探讨。 相似文献
103.
PURPOSE: To evaluate the accuracy of measuring intraocular pressure by handheld non-contact applanation tonometer. METHOD: 58 patients' (113 eyes) intraocular pressure were measured by Keeler, non-contact tonometer and R 900 Goldmann applanation tonometer and the results of measurement of intraocular pressure by the two kinds of tonometers were compared. RESULT: The mean intraocular pressure measured by non-contact is 16.31 +/- 5.59 mmHg and 17.49 +/- 6.13 mmHg (1 mmHg = 0.1333 kPa) by Goldmann applanation tonometer, respectively. There was no statistical significance to be found (P > 0.05) between the two methods. By linear correlation and regression analysis, a positive correlation was found between the two methods (r = 0.8942, b = 0.8154). CONCLUSION: The handheld non-contact tonometer has the same accuracy and reliability of measurement of intraocular pressure comparing with Goldmann applanation tonometer, and it can be used in glaucoma clinic and screening. 相似文献
104.
通常的数据采集与记录装置不易实现多量程测量。通过对标度方程进行分析得知,要改变量程只须改变两个参数——标度因子和量程下限。我们设计了一个使用单片机的多量程数据采集和记录装置,能处理多达256种量程。本文叙述了算法分析、硬件和软件的设计以及该装置的性能指标。 相似文献
105.
锆(Ⅳ)-3,5-diBr-PADAP-安替比林三元配合物的分光光度研究与应用 总被引:1,自引:0,他引:1
本文提出在安替比林存在下,以3,5-diBr-PADAP为显色剂,分光光度测定微量锆的新方法。在pH1~2的HCl介质中,锆(W)与试剂和安替比林形成配合比为1:1:1的红色三元配合物,最大吸收值在615nm波长处,摩尔吸光系数ε=1.35×10~5。锆(Ⅳ)量在0~25μg/25ml范围内,遵守比尔定律。方法简单、快速、准确。若采用钽试剂—苯萃取法分离共存离子,可适用于钽铌矿和合金中痕量锆的测定。 相似文献
106.
简要地介绍了氢离子敏场效应晶体管(H~+-ISFET)的基本结构和工作原理,提出了一种新型背面接触式H~+-ISFET。对该结构在版图、工艺设计中的有关问题,进行了探讨。最后指出:它在pH值的测量中有较好的实用价值。 相似文献
107.
Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.
IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported
that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method
can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to
study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni
immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening
the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress. 相似文献
108.
109.
Material removal and surface damage of Ti3SiC2 ceramic during electrical discharge machining (EDM) were investigated. Melting and decomposition were found to be the main material removal mechanisms during the machining process. Material removal rate was enhanced acceleratively with increasing discharge current, ie, working voltage, ui, but increased deceleratively with pulse duration, te. Microcracks in the surface and loose grains in the subsurface resulted from thermal shock were confirmed, and the surface damage in Ti3SiC2 ceramic led to a degradation of both strength and reliability. 相似文献
110.
Xinsheng Zhu Hansong Xu Jianmei Lu Juying Wang Shunhua Zhou 《Journal of Polymer Research》2008,15(4):295-300
Poly(ethylene terephthalate) (PET) is of excellent mechanical properties and melt processability and is widely used as raw
material for textile fibers. However, the flame retardant properties of PET were rather poor, and both reactive and additive
phosphorus- and halogen-containing compounds have been employed to enhance the reaction-to-fire properties while the meltdripping
behaviour during burning hasn’t been handled properly with the flame retardants. In this work, fluoropolymer was blended with
both pure PET (pPET) and reactive phosphorus-containing flame retarded copolyester (fPET), and the flame retardance and char
formation and mechanical properties of the resulted pPET and fPET blends were investigated. The tensile strengths of modified
pPET samples were worsen whereas those of modified fPET samples were improved at low concentrations. The initial thermal degradation
in nitrogen was accelerated remarkably for the two polyesters with fluoropolymer. The oxygen indices of the all modified samples
were reduced while char formation and meltdripping suppression were encouraged. The apparent melt viscosity and elasticity
for the two polyesters were gained much with antidripping agent. Therefore, fluoropolymer improved char formation of the two
polyesters based on the gaseous phase mechanism while the partial suppression of meltdripping behavior and the decrease of
mechanical properties mainly originated from the increase of melt viscosity via fibrillation for pPET. 相似文献