全文获取类型
收费全文 | 322141篇 |
免费 | 35008篇 |
国内免费 | 11990篇 |
专业分类
电工技术 | 16983篇 |
技术理论 | 30篇 |
综合类 | 19223篇 |
化学工业 | 63047篇 |
金属工艺 | 17102篇 |
机械仪表 | 19460篇 |
建筑科学 | 23909篇 |
矿业工程 | 9266篇 |
能源动力 | 8787篇 |
轻工业 | 24955篇 |
水利工程 | 5194篇 |
石油天然气 | 19811篇 |
武器工业 | 2254篇 |
无线电 | 37097篇 |
一般工业技术 | 42963篇 |
冶金工业 | 15822篇 |
原子能技术 | 2925篇 |
自动化技术 | 40311篇 |
出版年
2024年 | 1170篇 |
2023年 | 4468篇 |
2022年 | 8034篇 |
2021年 | 11356篇 |
2020年 | 9926篇 |
2019年 | 9920篇 |
2018年 | 10764篇 |
2017年 | 12137篇 |
2016年 | 11670篇 |
2015年 | 14768篇 |
2014年 | 17712篇 |
2013年 | 21391篇 |
2012年 | 20705篇 |
2011年 | 22015篇 |
2010年 | 20013篇 |
2009年 | 18964篇 |
2008年 | 18211篇 |
2007年 | 17427篇 |
2006年 | 17676篇 |
2005年 | 15217篇 |
2004年 | 10793篇 |
2003年 | 9304篇 |
2002年 | 8638篇 |
2001年 | 7704篇 |
2000年 | 7770篇 |
1999年 | 8049篇 |
1998年 | 6291篇 |
1997年 | 5183篇 |
1996年 | 4819篇 |
1995年 | 3997篇 |
1994年 | 3242篇 |
1993年 | 2277篇 |
1992年 | 1777篇 |
1991年 | 1415篇 |
1990年 | 1074篇 |
1989年 | 850篇 |
1988年 | 620篇 |
1987年 | 403篇 |
1986年 | 322篇 |
1985年 | 232篇 |
1984年 | 157篇 |
1983年 | 136篇 |
1982年 | 130篇 |
1981年 | 113篇 |
1980年 | 89篇 |
1979年 | 42篇 |
1978年 | 28篇 |
1977年 | 21篇 |
1976年 | 37篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
H.‐G. Boyen G. Kstle K. Zürn T. Herzog F. Weigl P. Ziemann O. Mayer C. Jerome M. Mller J.P. Spatz M.G. Garnier P. Oelhafen 《Advanced functional materials》2003,13(5):359-364
Starting with Co‐salt‐loaded inverse micelles, which form if the diblock copolymer polystyrene‐block‐poly(2‐vinylpyridine) is dissolved in a selective solvent like toluene and CoCl2 is added to the solution, monomicellar arrays of such micelles exhibiting a significant hexagonal order can be prepared on top of various substrates with tailored intermicellar distances and structure heights. In order to remove the polymer matrix and to finally obtain arrays of pure Co nanoparticles, the micelles are first exposed to an oxygen plasma, followed by a treatment in a hydrogen plasma. Applying in‐situ X‐ray photoelectron spectroscopy, it is demonstrated that: 1) The oxygen plasma completely removes the polymer, though conserving the original order of the micellar array. Furthermore, the resulting nanoparticles are entirely oxidized with a chemical shift of the Co 2p3/2 line pointing to the formation of Co3O4. 2) By the subsequent hydrogen plasma treatment the nanoparticles are fully reduced to metallic Co. 3) By exposing the pure Co nanoparticles for 100 s to various oxygen partial pressures pequation/tex2gif-inf-5.gif, a stepwise oxidation is observed with a still metallic Co core surrounded by an oxide shell. The data allow the extraction of the thickness of the oxide shell as a function of the total exposure to oxygen (pequation/tex2gif-inf-7.gif × time), thus giving the opportunity to control the ferromagnetic–antiferromagnetic composition of an exchange‐biased magnetic system. 相似文献
942.
悬浮床加氢裂化油溶性催化剂与沥青质的作用 总被引:1,自引:1,他引:0
在高压釜反应器中对添加了油溶性 Ni 催化剂(UPC-O)和水溶性 Ni 催化剂(UPC-W)的辽河稠油常压渣油(LHAR)进行了悬浮床加氢裂化实验。通过元素分析和傅里叶变换红外光谱(FTIR)分析对抑制反应生焦效果好的 UPC-O 与 LHAR 沥青质的作用进行了研究。元素分析结果显示,在 LHAR 中加入 UPC-O1000μg/g,沥青质和脱沥青质油中 Ni 含量分别出476μg/g和110μg/g 增加到7 559μg/g 和1 024μg/g,表明 UPC-O 在沥青质中有富集的趋势。FTIR 表征结果显示,UPC-O 和沥青质发生了相互作用。UPC-O 可在沥青质原位硫化为活性组分,对沥青质在悬浮床加氢裂化反应中的缩合起到好的抑制作用。 相似文献
943.
岩性圈闭储层描述技术及应用 总被引:4,自引:1,他引:3
本文以高分辨率地震资料为基础,应用测井、钻井等资料,从沉积微相分析入手,建立了以河道砂体、河口坝砂体为主的地质及地震响应模型,并根据地震反射波组特征、地震反演的阻抗值及其他地震属性参数,确定了研究区的砂体变化及其分布规律,总结出一套针对薄互层特点的岩性圈闭识别技术。本文方法在大庆长垣以西古龙和他拉哈西地区的实际应用中取得了明显的效果。 相似文献
944.
945.
946.
947.
本文对氨基酸营养条件下植物体内硝酸盐含量变化及其机理,土施植物激素前体色氨酸和蛋氨酸对高等植物生长和化学组成的影响。氨基酸和氨基酸肥料对植物产量和品质的影响作了综述。 相似文献
948.
风水联动放炮自动喷雾装置设计 总被引:2,自引:0,他引:2
矿尘始终是困扰井下安全生产的重要因素之一,危害很大。长期从事采掘和粉尘作业环境的职工易引起尘肺病,另外,在粉尘作业场所工作的职工的视线易受阻挡,操作中易造成人身事故。 相似文献
949.
F Javier Álvarez‐Hornos Carmen Gabaldón Vicente Martínez‐Soria Paula Marzal Josep‐Manuel Penya‐roja 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(5):643-653
BACKGROUND: Two peat biofilters were used for the removal of toluene from air for one year. One biofilter was fed with pure toluene and the other received 1:1 (by weight) ethyl acetate:toluene mixture. RESULTS: The biofilters were operated under continuous loading: the toluene inlet load (IL) at which 80% removal occurred was 116 g m?3 h?1 at 57 s gas residence time. Maximum elimination capacity of 360 g m?3 h?1 was obtained at an IL of 745 g m?3 h?1. The elimination of toluene was inhibited by the presence of ethyl acetate. Intermittent loading, with pollutants supplied for 16 h/day, 5 days/week, did not significantly affect the removal efficiency (RE). Biomass was fully activated in 2 h after night closures, but 6 h were required to recover RE after weekend closures. Live cell density remained relatively constant over the operational period, while the dead cell fraction increased. Finally, a 15 day starvation period was applied and operation then re‐started. Performance was restored with similar re‐acclimatization period to that after weekend closures, and a reduction in dead cell fraction was observed. CONCLUSION: This study demonstrates the capacity of the system to handle intermittent loading conditions that are common in industrial practices, including long‐term starvation. Copyright © 2008 Society of Chemical Industry 相似文献
950.
Jiang-Li Chen Zhuo Xu Shao-Bo Qu Xiao-Yong Wei Xiao-Hui Liu 《Ceramics International》2008,34(4):803-807
The NiFe2O4 and Pb(Zr0.52Ti0.48)O3 ceramic composites are prepared by conventional solid state reaction method. The microstructural and morphological properties of the composites are studied by X-ray diffraction analysis and scanning electron microscopy. Results indicate that the ferrite and piezoelectric phases can co-exist in the composites. The relationship between the dielectric constant and frequency (40 Hz–40 MHz) as well as temperature is also investigated. It is noted that the transition temperature of the composites is about 380 °C. A double electric hysteresis loop is observed in our composites. The magnetic properties are relatively weak according to the magnetic hysteresis loop. With increase in the content of the ferrite phase, the permeability increases. The electromagnetic properties of the as-prepared composites are tunable according to the content of the NiFe2O4 phase. 相似文献