全文获取类型
收费全文 | 551864篇 |
免费 | 64482篇 |
国内免费 | 45126篇 |
专业分类
电工技术 | 49344篇 |
技术理论 | 3篇 |
综合类 | 60728篇 |
化学工业 | 68460篇 |
金属工艺 | 38366篇 |
机械仪表 | 39983篇 |
建筑科学 | 43016篇 |
矿业工程 | 23995篇 |
能源动力 | 14502篇 |
轻工业 | 57653篇 |
水利工程 | 18846篇 |
石油天然气 | 20663篇 |
武器工业 | 9074篇 |
无线电 | 57980篇 |
一般工业技术 | 45480篇 |
冶金工业 | 21538篇 |
原子能技术 | 8980篇 |
自动化技术 | 82861篇 |
出版年
2024年 | 2886篇 |
2023年 | 8427篇 |
2022年 | 21162篇 |
2021年 | 27241篇 |
2020年 | 19482篇 |
2019年 | 13636篇 |
2018年 | 14565篇 |
2017年 | 16648篇 |
2016年 | 14943篇 |
2015年 | 24075篇 |
2014年 | 30799篇 |
2013年 | 35986篇 |
2012年 | 45888篇 |
2011年 | 48057篇 |
2010年 | 45894篇 |
2009年 | 43553篇 |
2008年 | 45237篇 |
2007年 | 44212篇 |
2006年 | 37926篇 |
2005年 | 30934篇 |
2004年 | 22224篇 |
2003年 | 15015篇 |
2002年 | 14274篇 |
2001年 | 12998篇 |
2000年 | 10212篇 |
1999年 | 4500篇 |
1998年 | 1820篇 |
1997年 | 1458篇 |
1996年 | 1331篇 |
1995年 | 1077篇 |
1994年 | 855篇 |
1993年 | 771篇 |
1992年 | 597篇 |
1991年 | 400篇 |
1990年 | 365篇 |
1989年 | 383篇 |
1988年 | 291篇 |
1987年 | 185篇 |
1986年 | 146篇 |
1985年 | 81篇 |
1984年 | 90篇 |
1983年 | 74篇 |
1982年 | 69篇 |
1981年 | 102篇 |
1980年 | 176篇 |
1979年 | 117篇 |
1965年 | 16篇 |
1964年 | 10篇 |
1959年 | 106篇 |
1951年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Xuewu Li Lin Zhang Tian Shi Weining Yu Jinhui Shao Xuegang Zhou Yuxing He Binbin Zhang 《工业材料与腐蚀》2021,72(5):951-959
Ti-based amorphous metallic glasses have excellent mechanical, physical, and chemical properties, which is an important development direction and research hotspot of metal composite reinforcement. As a stable, simple, efficient, and large-scale preparation technology of metallic powders, the gas atomization process provides an effective way of preparing amorphous metallic glasses. In this study, the controllable fabrication of a Ti-based amorphous powder, with high efficiency, has been realized by using gas atomization. The scanning electron microscope, energy-dispersive spectrometer, and X-ray diffraction are used to analyze surface morphology, element distribution, and phase structure, respectively. A microhardness tester is used to measure the mechanical property. An electrochemical workstation is used to characterize corrosion behavior. The results show that as-prepared microparticles are more uniform and exhibit good amorphous characteristics. The mechanical test shows that the hardness of amorphous powder is significantly increased as compared with that before preparation, which has the prospect of being an important part of engineering reinforced materials. Further electrochemical measurement shows that the corrosion resistance of the as-prepared sample is also significantly improved. This study has laid a solid foundation for expanding applications of Ti-based metallic glasses, especially in heavy-duty and corrosive domains. 相似文献
42.
43.
44.
比喻是一种利用事物之间的相似点建立关系的修辞方式。明喻是比喻中最常见的形式,具有明显的喻词,例如"像",用于关联本体和喻体。近年来高考语文散文类鉴赏题中多有考查明喻句的试题,为了解答此类鉴赏题,需要识别比喻句中的本体和喻体要素。该文提出了基于词性特征的明喻识别及要素抽取方法。首先将句子中词向量化表示与词性特征向量化表示进行融合,将融合后的向量输入到BiLSTM中进行训练,然后利用CRF解码出全局最优标注序列;最后得到明喻识别和要素抽取的结果。公开数据集上的实验结果表明,该方法优于已有的单任务方法;同时也将该文方法应用于北京高考语文鉴赏题中比喻句的识别与要素抽取,验证了方法的可行性。 相似文献
45.
46.
Fangjun Zhu You Shi Guorong Hu Zhongdong Peng Yanbing Cao Qian Sun Zhichen Xue Yinjia Zhang Ke Du 《Ceramics International》2021,47(3):3070-3078
Titanium and boron are simultaneously introduced into LiNi0.8Co0.1Mn0.1O2 to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti4+ ion replaces Li+ ion and reduces the cation mixing; B3+ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO6] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g-1 at 1 C and 155.5 mAh·g-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi0.8Co0.1Mn0.1O2. 相似文献
47.
48.
为缓解我国水、能源和粮食资源紧张问题,促进资源可持续利用,构建水-能源-粮食系统,利用耦合协调度模型对我国的30个省(自治区、直辖市)进行测算,并利用空间杜宾模型分析主要影响因素。结果表明:2003—2017年,我国能源、粮食评价[JP]指数高于水资源评价指数,系统综合评价指数逐年递增;大部分省份耦合协调度处于初级协调水平且呈现逐年上升的态势,个别省份耦合协调度濒临失调;耦合协调度空间自相关性较强,虽有明显波动,但是呈现逐年加强的态势;影响耦合协调度的主要因素有从业人口数、固定资产投资额、人均生产总值、人口总数、[JP]文盲人口占比、工业污染排放、城镇化。 相似文献
49.
Jieyun Tu Xinghui Shi Yuanrong Jing Huimin Zou Jakub Kadlcak Zhanfu Yong Susu Liu Guangyong Liu 《Polymer Engineering and Science》2021,61(8):2213-2221
Equilibrium swelling and rheological tests were adopted to systematically investigate the effects of softener type and dosage on the crosslink densities. The results turned out that the chemical crosslink density could be distinguished from the physical crosslink density by comparing the results of equilibrium swelling and rheological tests. The liquid butadiene (LB) as a softener leads to the greatest reduction in crosslink density, followed by polyethylene wax (PW) and paraffinic oil (PO). The tensile strength decreases with increasing PO content while shows peak values with increase of LB and PW contents. The dependencies of chemical crosslink density on the aging time under 150°C are quite different for the three softeners, which can be expected from the double crosslinking networks consisting of small softener and large main crosslinking networks. Further investigation has been performed to correlate the tensile strength with chemical crosslink density of ethylene propylene diene monomer elastomer vulcanizates. Three different linear relationships can be obtained for the softeners independent of the aging time. It can now be expected from this study that the role of some new softeners in rubber compounds is not only confined to plasticization but also forms crosslinking networks in the peroxide-cured rubbers. 相似文献
50.