全文获取类型
收费全文 | 116099篇 |
免费 | 3815篇 |
国内免费 | 1702篇 |
专业分类
电工技术 | 2612篇 |
技术理论 | 2篇 |
综合类 | 4178篇 |
化学工业 | 16888篇 |
金属工艺 | 6778篇 |
机械仪表 | 5235篇 |
建筑科学 | 4836篇 |
矿业工程 | 1661篇 |
能源动力 | 2059篇 |
轻工业 | 5490篇 |
水利工程 | 1886篇 |
石油天然气 | 2562篇 |
武器工业 | 256篇 |
无线电 | 12731篇 |
一般工业技术 | 20156篇 |
冶金工业 | 4322篇 |
原子能技术 | 675篇 |
自动化技术 | 29289篇 |
出版年
2024年 | 125篇 |
2023年 | 663篇 |
2022年 | 1024篇 |
2021年 | 1589篇 |
2020年 | 1228篇 |
2019年 | 939篇 |
2018年 | 15388篇 |
2017年 | 14386篇 |
2016年 | 10896篇 |
2015年 | 1914篇 |
2014年 | 1859篇 |
2013年 | 2208篇 |
2012年 | 5237篇 |
2011年 | 11477篇 |
2010年 | 10131篇 |
2009年 | 7361篇 |
2008年 | 8457篇 |
2007年 | 9413篇 |
2006年 | 1910篇 |
2005年 | 2691篇 |
2004年 | 2084篇 |
2003年 | 2050篇 |
2002年 | 1340篇 |
2001年 | 771篇 |
2000年 | 903篇 |
1999年 | 909篇 |
1998年 | 760篇 |
1997年 | 666篇 |
1996年 | 615篇 |
1995年 | 486篇 |
1994年 | 376篇 |
1993年 | 284篇 |
1992年 | 216篇 |
1991年 | 187篇 |
1990年 | 116篇 |
1989年 | 101篇 |
1988年 | 89篇 |
1987年 | 52篇 |
1986年 | 51篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
高分子铁盐絮凝剂制备及其应用研究 总被引:5,自引:0,他引:5
研究了以废铁屑和工业硫酸亚铁为原料,在常压和加热条件下,用氯酸钾作为氧化剂制取聚合硫酸铁(PFS)的工艺条件,并在PFS制备的基础上,合成了聚磷硫酸铁(PPFS)和聚氯硫酸铁(PFCS)。将所制备的聚铁用于污水处理实验,结果表明:用该方法制备的聚铁絮凝剂对实际水样具有较好的混凝处理效果,且制备工艺简单、速度快,从根本上消除了用NaNO_2催化氧化法制备聚铁对环境造成的二次污染。 相似文献
963.
964.
NCT310型常温氧化锌脱硫剂的研究 总被引:1,自引:0,他引:1
介绍了NCT310型常温氧化锌脱硫剂实验室研究情况。结果表明,在常温(20~60℃)下,该脱硫剂对气体中的硫化氢有优越的脱除性能。在40℃、1000h-1、进口H2S~1.5g/m3条件下,可控制出口H2S<7×10-4g/m3,穿透硫容(重量比)>10%。 相似文献
965.
利用缩聚聚合,在纳米TiO2颗粒表面接枝聚对苯二甲酸乙二醇酯的预聚物(prePET).通过红外(FT-IR),热失重(TGA)和X射线电子能谱(XPS)分析表明prePET成功接枝在纳米TiO2的表面.透射电子显微镜(TEM)观察表明prePET-TiO2纳米复合粒子粒径大约在30 nm,分散性好.原子力显微镜(AFM)观察表明prePET-TiO2纳米复合粒子在1,1,2,2-四氯乙烷中均匀分散,无团聚.同时发现反应真空度影响了TiO2表面的接枝率,真空度小,接枝率大.扫描电子显微镜(SEM)观察表明prePET-TiO2纳米复合粒子能够在聚碳酸酯(PC)基体中具有良好的分散性,复合粒子填充量的上升增强了prePET-TiO2/PC复合材料的拉伸强度. 相似文献
966.
HDPE耐环境应力开裂性能的研究及改进 总被引:1,自引:0,他引:1
对HDPE的耐环境应力开裂性能进行了研究。试验表明:采用共混及化学改性的方法,HDPE的耐环境应力开裂性能有了很大提高,为解决HDPE树脂在制作管材时出现的短时间内应力开裂问题提供了依据。 相似文献
967.
锌基重防腐双涂层防护技术在高速公路护栏上的应用 总被引:1,自引:0,他引:1
介绍了双涂层防护技术的进展以及锌基重防腐双涂层防护技术在高速公路护栏上的应用。 相似文献
968.
The coupled photocatalyst WO3/TiO2 is prepared by ball milling by doping WO3 into TiO2 and using H2O solution as disperser. The coupled photocatalyst WO3/TiO2 is characterized by UV–VIS diffuse reflection spectrum, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Transmission electron microscopy (TEM). The results show that the optimum percentage of WO3 doped is 3% and that the photocatalytic activity of the coupled WO3/TiO2 photocatalyst is much higher than that of TiO2 and WO3–TiO2 with no ball milling. Compared with TiO2, the photoexcited wavelength range of the WO3/TiO2 photocatalyst red-shifts about 50 nm, and the light absorption intensity is also improved. The crystal phase of TiO2 is not changed and new crystal phases are not found during the process of ball milling. WO3 and TiO2 coupled highly, forming the WO3/TiO2 photocatalyst. The increased photocatalytic activity of the coupled photocatalyst may be attributed to the enhance charge separation efficiency and the extend wavelength range of photoexcitation. 相似文献
969.
Nanocrystalline hydroxyapatite (HAp) was prepared by a precipitation method with aid of ultrasonic irradiation using Ca(NO3)2 and NH4H2PO4 as source material and carbamide (NH2CONH2) as precipitator. The crystallization and morphology of the prepared nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanism and kinetics of the nano-hydroxyapatite were considered in particular, and the influence of the temperature and time on the HAp formation rate was also investigated. The results show that the needle-like HAp crystalline was prepared by the ultrasonic precipitation process. The HAp content increases with the preparation temperature and time. The adding of carbamide is helpful for formation of HAp nanoparticles. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 59.9 kJ/mol was obtained by calculation. 相似文献
970.
Simone C. Godoy Marco Flôres Ferrão Annelise E. Gerbase 《Journal of the American Oil Chemists' Society》2007,84(6):503-508
A rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy
is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined
by the official method of AOCS Tx 1a-66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares
(PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions
between 3,150 and 990 cm−1 and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The
resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method
was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained
by the AOCS standard method. A correlation coefficient of R
2 = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer,
the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages
of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce
residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation
reaction. 相似文献