全文获取类型
收费全文 | 140084篇 |
免费 | 16523篇 |
国内免费 | 10757篇 |
专业分类
电工技术 | 13156篇 |
技术理论 | 5篇 |
综合类 | 13541篇 |
化学工业 | 17652篇 |
金属工艺 | 9468篇 |
机械仪表 | 9996篇 |
建筑科学 | 10839篇 |
矿业工程 | 4663篇 |
能源动力 | 3819篇 |
轻工业 | 16314篇 |
水利工程 | 5422篇 |
石油天然气 | 4438篇 |
武器工业 | 1881篇 |
无线电 | 15256篇 |
一般工业技术 | 12645篇 |
冶金工业 | 5132篇 |
原子能技术 | 2350篇 |
自动化技术 | 20787篇 |
出版年
2024年 | 792篇 |
2023年 | 2352篇 |
2022年 | 5463篇 |
2021年 | 7023篇 |
2020年 | 5029篇 |
2019年 | 3623篇 |
2018年 | 3853篇 |
2017年 | 4151篇 |
2016年 | 3823篇 |
2015年 | 6036篇 |
2014年 | 7598篇 |
2013年 | 9243篇 |
2012年 | 11179篇 |
2011年 | 11523篇 |
2010年 | 11090篇 |
2009年 | 10776篇 |
2008年 | 11028篇 |
2007年 | 10819篇 |
2006年 | 9371篇 |
2005年 | 7557篇 |
2004年 | 5716篇 |
2003年 | 4089篇 |
2002年 | 4140篇 |
2001年 | 3756篇 |
2000年 | 2808篇 |
1999年 | 1367篇 |
1998年 | 538篇 |
1997年 | 469篇 |
1996年 | 413篇 |
1995年 | 340篇 |
1994年 | 267篇 |
1993年 | 219篇 |
1992年 | 173篇 |
1991年 | 121篇 |
1990年 | 125篇 |
1989年 | 88篇 |
1988年 | 82篇 |
1987年 | 53篇 |
1986年 | 45篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 35篇 |
1979年 | 22篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1959年 | 23篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
In this article, the silver-plated polyamide fabrics (SPPAFs) with high electroconductibility and shielding effectiveness were fabricated by using in situ reduction of polydopamine and chemical silvering. The effects of SPPAFs dopamine (C8H11O2N) and silver nitrate (AgNO3) concentration on surface resistivity and electromagnetic interference shielding effectiveness were studied. The results showed that the surface resistivity of SPPAFs can reach a minimum value of 0.06 ± 0.014 Ω cm−1, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 120 g L−1. The shielding effectiveness of SPPAFs in the wide frequency range of 10–3000 MHz increases with the increase in the concentration of AgNO3, and increases first and stabilizes afterward with increasing C8H11O2N concentration. When the concentration of C8H11O2N and AgNO3 is 3 and 120 g L−1, respectively, mean shielding effectiveness values in the low-, medium-, and high-frequency bands are 71.3, 73.8, and 76.1 dB, respectively. Moreover, the mean shielding effectiveness values is 83.79 dB in the frequency range of 1.2–2.3 GHz. The dominant shielding mechanism of SPPAFs is the reflected electromagnetic waves and the absorption shielding effectiveness is less than 2 dB. The average electromagnetic shielding values of SPPAFs are above 67 dB after 16 weeks of storage, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 80 and 100 g L−1. The prepared SPPAFs show promising applications in military textiles and smart wearable clothing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48227. 相似文献
32.
Lei He Yan Xuan Feng Zhang Xue Wang Huaqing Pan Junfeng Ren Meina Chen 《International Journal of Hydrogen Energy》2021,46(1):1096-1105
Bulk and surface properties of proton stability and transportation in Y and Nd co-doped BaCeO3 (BCYN), especially the effect of Nd segregation, were investigated by first-principles calculations. Since the structure of doped BaCeO3 at the operating temperature of proton-conducting has been unclear for a long time, we have summarized the latest experimental results and calculated the structure of the asymmetric BCYN for the first time. The results show that compared with Y, Nd doping promotes oxygen vacancy formation, however reduces proton stability. Our calculation can also provide a possible explanation for the formation of space charge layer at the grain boundary of doped BaCeO3 in experiment. Unlike the stable Y in BCYN, Nd is calculated to be easily segregated, which can facilitate both proton hydration and proton transportation near the surface. Moreover, Nd segregation at the grain boundary is predicted to be beneficial for proton transportation between grains. 相似文献
33.
针对目前运动想象脑电(EEG)信号识别率较低的问题,考虑到脑电信号蕴含着丰富的时频信息,提出一种基于时频域的卷积神经网络(CNN)运动想象脑电信号识别方法。首先,利用短时傅里叶变换(STFT)对脑电信号的相关频带进行预处理,并将多个电极的时频图组合构造出一种二维时频图;然后,针对二维时频图的时频特性,通过一维卷积的方法设计了一种新颖的CNN结构;最后,通过支持向量机(SVM)对CNN提取的特征进行分类。基于BCI数据集的实验结果表明,所提方法的平均识别率为86.5%,优于其他传统运动想象脑电信号识别方法;同时将该方法应用在智能轮椅上,验证了其有效性。 相似文献
35.
36.
37.
本研究以人急性髓性白血病细胞株THP-1为研究对象,初步探讨其抗癌活性及作用机制。通过光学显微镜观察N6-2-苄胺羟基腺苷(oTR)作用后THP-1细胞形态学和数目变化;CCK-8法检测oTR对THP-1细胞的增殖抑制作用,并用核苷转运体拮抗剂和腺苷受体拮抗剂预处理细胞检测oTR进入细胞的方式;用流式细胞仪分析oTR作用对THP-1细胞凋亡和分化的影响。结果表明,oTR可显著(P<0.05)抑制THP-1细胞的增殖能力,且呈浓度依赖性;核苷转运体拮抗剂Dipyridamole预处理THP-1细胞后,可明显逆转oTR的增殖抑制作用,而4种腺苷受体拮抗剂(DPCPX、SCH58261、MRS1754和MRA1191)则无显著影响;oTR可诱导处理组细胞亚倍体峰比例显著(P<0.05)高于对照组,且细胞髓系分化标志蛋白CD11b表达明显升高。以上结果表明细胞分裂素oTR通过核苷转运体途径进入THP-1细胞,显著(P<0.05)抑制细胞的增殖,并可诱导THP-1细胞发生凋亡和髓系分化。 相似文献
38.
PROfound研究——前列腺癌精准治疗新希望 总被引:1,自引:0,他引:1
转移性去势抵抗性前列腺癌(metastatic castrate-resistant prostate cancer,mCRPC)是前列腺癌发展的终末阶段。患者生存预后很差。尽管不断地有新的治疗手段出现,比如新型内分泌治疗以及紫杉醇类化疗,mCRPC患者的生存期依然很有限。奥拉帕利是一款聚腺苷酸二磷酸核糖基聚合酶(poly ADP-ribose polymerase,PARP)抑制剂,PARP酶在DNA修复中扮演着重要的角色。奥拉帕利已经获批用于卵巢癌和乳腺癌的治疗。目前,奥拉帕利用于mCRPC治疗的III期临床研究PROfound的结果在2019年的欧洲肿瘤内科学会(ESMO)年会与2020年的美国临床肿瘤学会-泌尿生殖系统肿瘤研讨会(ASCO-GU)已经发布。本文将带来PROfound研究的结果以及最新的结果更新。 相似文献
39.
Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride)
下载免费PDF全文
![点击此处可从《Polymer International》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mengjiao Zhang Weihong Wu Shaorui He Xue Wang Yunhong Jiao Hongqiang Qu Jianzhong Xu 《Polymer International》2018,67(4):445-452
The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO3) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO3 and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO3. In addition, the incorporation of AC and MoO3 greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO3 was 10 phr, PVC/AC/MoO3 had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m?2 and 0.1472 m2 s?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO3, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO3 produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry 相似文献
40.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)