全文获取类型
收费全文 | 237598篇 |
免费 | 7382篇 |
国内免费 | 3387篇 |
专业分类
电工技术 | 6544篇 |
技术理论 | 6篇 |
综合类 | 4196篇 |
化学工业 | 38275篇 |
金属工艺 | 11545篇 |
机械仪表 | 8888篇 |
建筑科学 | 9055篇 |
矿业工程 | 3067篇 |
能源动力 | 6615篇 |
轻工业 | 19828篇 |
水利工程 | 2759篇 |
石油天然气 | 7653篇 |
武器工业 | 459篇 |
无线电 | 26230篇 |
一般工业技术 | 40362篇 |
冶金工业 | 36416篇 |
原子能技术 | 5008篇 |
自动化技术 | 21461篇 |
出版年
2022年 | 2468篇 |
2021年 | 3703篇 |
2020年 | 2720篇 |
2019年 | 2874篇 |
2018年 | 3909篇 |
2017年 | 4091篇 |
2016年 | 3983篇 |
2015年 | 3896篇 |
2014年 | 5687篇 |
2013年 | 11200篇 |
2012年 | 8161篇 |
2011年 | 10328篇 |
2010年 | 8675篇 |
2009年 | 9145篇 |
2008年 | 9078篇 |
2007年 | 9009篇 |
2006年 | 8180篇 |
2005年 | 7425篇 |
2004年 | 6494篇 |
2003年 | 6274篇 |
2002年 | 6574篇 |
2001年 | 6184篇 |
2000年 | 5521篇 |
1999年 | 5744篇 |
1998年 | 11619篇 |
1997年 | 8438篇 |
1996年 | 6751篇 |
1995年 | 5121篇 |
1994年 | 4244篇 |
1993年 | 4028篇 |
1992年 | 2967篇 |
1991年 | 2807篇 |
1990年 | 2622篇 |
1989年 | 2601篇 |
1988年 | 2528篇 |
1987年 | 2214篇 |
1986年 | 2135篇 |
1985年 | 2404篇 |
1984年 | 2220篇 |
1983年 | 2038篇 |
1982年 | 1905篇 |
1981年 | 1958篇 |
1980年 | 1818篇 |
1979年 | 1820篇 |
1978年 | 1778篇 |
1977年 | 2110篇 |
1976年 | 2687篇 |
1975年 | 1557篇 |
1974年 | 1550篇 |
1973年 | 1607篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
105.
106.
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。 相似文献
107.
108.
Enhancement of the dissolution rate of the poorly water-soluble hypoglycemic agent, gliclazide, by the aid of lyophilization was investigated. Mannitol, sodium lauryl sulfate (SLS) and polyvinyl pyrrolidone (PVP-k-30) were employed in different weight ratios (43%, 56% and 64% w/w, respectively) as water-soluble excipients in the formulation. Lyophilized systems were found to exhibit extremely higher in vitro dissolution rate compared to the unprocessed drug powder. Solid state characterization of the lyophilized systems using X-ray powder diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques revealed that dissolution enhancement was attributable to transformation of gliclazide from the crystalline to an amorphous state in the solid dispersion formed during the lyophilization process. The gastrointestinal absorption and hypoglycemic effect of the lyophilized gliclazide/SLS system were investigated following oral administration to Albino rabbits. Cmax and area under the plasma concentration–time curve of gliclazide (AUC0–12) after administration of the lyophilized formulations were significantly higher than those obtained after administration of the unprocessed gliclazide. 相似文献
109.
Physical Stability of Octenyl Succinate–Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems 下载免费PDF全文
The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications. 相似文献
110.