全文获取类型
收费全文 | 8532篇 |
免费 | 276篇 |
国内免费 | 147篇 |
专业分类
电工技术 | 184篇 |
综合类 | 2668篇 |
化学工业 | 432篇 |
金属工艺 | 126篇 |
机械仪表 | 181篇 |
建筑科学 | 908篇 |
矿业工程 | 175篇 |
能源动力 | 73篇 |
轻工业 | 186篇 |
水利工程 | 465篇 |
石油天然气 | 191篇 |
武器工业 | 13篇 |
无线电 | 265篇 |
一般工业技术 | 222篇 |
冶金工业 | 1926篇 |
原子能技术 | 12篇 |
自动化技术 | 928篇 |
出版年
2023年 | 38篇 |
2022年 | 84篇 |
2021年 | 156篇 |
2020年 | 130篇 |
2019年 | 84篇 |
2018年 | 72篇 |
2017年 | 119篇 |
2016年 | 168篇 |
2015年 | 182篇 |
2014年 | 527篇 |
2013年 | 398篇 |
2012年 | 566篇 |
2011年 | 659篇 |
2010年 | 585篇 |
2009年 | 616篇 |
2008年 | 520篇 |
2007年 | 588篇 |
2006年 | 501篇 |
2005年 | 439篇 |
2004年 | 453篇 |
2003年 | 407篇 |
2002年 | 333篇 |
2001年 | 244篇 |
2000年 | 137篇 |
1999年 | 104篇 |
1998年 | 52篇 |
1997年 | 52篇 |
1996年 | 26篇 |
1995年 | 29篇 |
1994年 | 31篇 |
1993年 | 18篇 |
1989年 | 22篇 |
1988年 | 25篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1975年 | 14篇 |
1965年 | 25篇 |
1964年 | 32篇 |
1963年 | 25篇 |
1962年 | 21篇 |
1961年 | 29篇 |
1960年 | 23篇 |
1959年 | 28篇 |
1958年 | 32篇 |
1957年 | 26篇 |
1956年 | 31篇 |
1955年 | 41篇 |
1954年 | 26篇 |
排序方式: 共有8955条查询结果,搜索用时 21 毫秒
1.
如何在互联网时代打造一个信息化的管理模式,已经成为广大学校图书管理发展过程中亟待处理的问题。文章就互联网时代下的高职图书管理信息化建设进行了详细探讨,以期能够给广大同仁提供一些借鉴参考,共同为图书管理工作的现代化改革和发展贡献力量。 相似文献
2.
在新时期下,传统的英语教学方法已经不适合学生的学习和发展了,经过笔者的研究和分析发现,小学生对故事似乎是非常感兴趣,所以就针对多媒体技术在小学英语故事教学中的应用进行了几点尝试。 相似文献
3.
Vegetable intake is far below recommendations among African-American adolescents living in economically-underserved urban areas. While the National School Lunch Program (NSLP) helps overcome access barriers, vegetable intake remains challenging and novel interventions are required. A two-year, multi-phase, school-based intervention was conducted at an urban, economically-underserved, and predominantly African-American high school in Baltimore, Maryland to determine whether stakeholder-informed addition of spices and herbs to NSLP vegetables would increase intake. The stakeholder engagement phase included assessment of NSLP vegetable attitudes/preferences among 43 school stakeholders and subsequent student sensory testing. The second phase was conducted in the school cafeteria and consisted of eight weeks comparing student intake of typical vegetable recipes versus otherwise-identical recipes with spices and herbs. 4570 student lunch plates were included in the vegetable intake comparison. Vegetable intake was measured by lunch tray plate waste. Willingness to try vegetables was assessed by the difference between plate waste and estimated mean vegetable served weight. Intake of typical vegetable recipes and vegetable recipes with spices and herbs was compared with student’s t-test. Chi-square test was used to compare willingness to try vegetables. Total vegetable intake was 18.2% higher (8.22 g per meal, p < 0.0001) with spices and herbs than with typical recipes. There were no differences in trying vegetables with spices and herbs, although student-led advocacy was associated with increased trying vegetables with spices and herbs (78.8% with advocacy, 67.5% without advocacy, p < 0.0001). The addition of spices and herbs to vegetables in the NSLP was feasible and associated with small increases in vegetable intake at an urban, economically-underserved, and predominantly African-American high school. 相似文献
4.
Bong Gu Lee Jun IL Yang Euna Kim Sun Woo Geum Ju-Hyeong Park Min-Kyeong Yeo 《Indoor air》2021,31(5):1553-1562
The advent of high-throughput sequencing methods allowed researchers to fully characterize microbial community in environmental samples, which is crucial to better understand their health effects upon exposures. In our study, we investigated bacterial and fungal community in indoor and outdoor air of nine classrooms in three elementary schools in Seoul, Korea. The extracted bacterial 16S rRNA gene and fungal ITS regions were sequenced, and their taxa were identified. Quantitative polymerase chain reaction for total bacteria DNA was also performed. The bacterial community was richer in outdoor air than classroom air, whereas fungal diversity was similar indoors and outdoors. Bacteria such as Enhydrobacter, Micrococcus, and Staphylococcus that are generally found in human skin, mucous membrane, and intestine were found in great abundance. For fungi, Cladosporium, Clitocybe, and Daedaleopsis were the most abundant genera in classroom air and mostly related to outdoor plants. Bacterial community composition in classroom air was similar among all classrooms but differed from that in outdoor air. However, indoor and outdoor fungal community compositions were similar for the same school but different among schools. Our study indicated the main source of airborne bacteria in classrooms was likely human occupants; however, classroom airborne fungi most likely originated from outdoors. 相似文献
5.
6.
As the development of cloud computing and the convenience of wireless sensor netowrks, smart devices are widely used in daily life, but the security issues of the smart devices have not been well resolved. In this paper, we present a new NTRU-type public-key cryptosystem over the binary field. Specifically, the security of our scheme relies on the computational intractability of an unbalanced sparse polynomial ratio problem (DUSPR). Through theoretical analysis, we prove the correctness of our proposed cryptosystem. Furthermore, we implement our scheme using the NTL library, and conduct a group of experiments to evaluate the capabilities and consuming time of encryption and decryption. Our experiments result demonstrates that the NTRU-type public-key cryptosystem over the binary field is relatively practical and effective. 相似文献
7.
为了提高中硬煤层综采工作面的块煤率,根据矿井的地质条件及设备选型,从开采工艺和装备两方面进行了研究。采用微差爆破技术对工作面煤壁进行了弱化;对采煤机参数进行了优化,并采用数值模拟方法进行校验。研究结果表明:采用煤层弱化与采煤机参数优化相结合的技术措施后,井下工作面的块煤率提高了4.34%,地面块煤率提高了8.59%,块煤率得到了明显提高,给煤矿带来了显著的经济效益。 相似文献
8.
9.
Although the unprecedented prevalence of social media has infiltrated into international students’ daily trajectories and become an indispensable component of their intercultural communication, yet surprisingly few attempts have been implemented to systematically unpack how the innovative technology could play a role in these sojourners’ acculturation experiences and the consequences of migration and cross-cultural adaption. In order to address such research gap, the objective of this present article is to provide a review of academic, peer-reviewed journal studies that examined the potential effect of social media engagement on international university students’ acculturation process, coping strategies, and psychological adjustments during the period from 2010 to 2019. Moreover, building upon conceptualizations from new media and transcultural research literature, a conceptual framework was developed to classify the relevant studies for further analysis. Overall, these theories and studies synthesized in this paper emphasize the vital role of social media in the acculturation, coping behaviors and mental health for ethnic minorities in the host country. Additionally, certain dimensions of attitudes and behaviors through social media could exert the important influence on the psychological adaption. Therefore, conclusions of the research may assist to further inform practitioners who may encounter newcomers’ experiencing intercultural adjustments and psychological issues in the digital media age. Furthermore, this current review may also help educators determine certain barriers that have not been resolved in campus tactics which may influence the acculturation of sojourning populations. 相似文献
10.
采用中红外光谱结合化学计量学的方法对车用保险杠碎片进行鉴别,分别对52个车用保险杠碎片样本的全波段光谱数据、指纹区光谱数据和主成分分析降维后的光谱数据建立Fisher判别分析和K近邻算法2种分类模型,并对分类结果进行比较。结果表明,主成分分析提取特征变量后构建的分类模型,分类的准确率更高,对聚丙烯(PP)、PP/滑石粉、PP/滑石粉/碳酸钙(CaCO3)3种类型的样本分类准确率达到92.3 %,对PP/滑石粉类型中的10种品牌样本分类准确率达到88.9 %,分类结果理想;在构建的2种分类模型中,Fisher判别分析模型的分类率远高于K近邻算法模型,分析认为K近邻算法模型受到样本不均衡的影响;中红外光谱结合化学计量学可以实现对车用保险杠碎片的准确区分,且满足快速、无损的检验要求。 相似文献