全文获取类型
收费全文 | 6299篇 |
免费 | 483篇 |
国内免费 | 284篇 |
专业分类
电工技术 | 600篇 |
综合类 | 729篇 |
化学工业 | 339篇 |
金属工艺 | 97篇 |
机械仪表 | 261篇 |
建筑科学 | 1663篇 |
矿业工程 | 203篇 |
能源动力 | 290篇 |
轻工业 | 310篇 |
水利工程 | 160篇 |
石油天然气 | 240篇 |
武器工业 | 37篇 |
无线电 | 477篇 |
一般工业技术 | 243篇 |
冶金工业 | 275篇 |
原子能技术 | 43篇 |
自动化技术 | 1099篇 |
出版年
2024年 | 12篇 |
2023年 | 44篇 |
2022年 | 131篇 |
2021年 | 147篇 |
2020年 | 164篇 |
2019年 | 123篇 |
2018年 | 107篇 |
2017年 | 136篇 |
2016年 | 187篇 |
2015年 | 190篇 |
2014年 | 494篇 |
2013年 | 329篇 |
2012年 | 547篇 |
2011年 | 532篇 |
2010年 | 469篇 |
2009年 | 467篇 |
2008年 | 390篇 |
2007年 | 501篇 |
2006年 | 413篇 |
2005年 | 331篇 |
2004年 | 314篇 |
2003年 | 243篇 |
2002年 | 192篇 |
2001年 | 133篇 |
2000年 | 104篇 |
1999年 | 79篇 |
1998年 | 59篇 |
1997年 | 43篇 |
1996年 | 28篇 |
1995年 | 34篇 |
1994年 | 27篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1959年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有7066条查询结果,搜索用时 15 毫秒
1.
In the past, thinking of carrying electronic devices inside our bodies was only posed by non-real scenarios. The emergence of insertable devices has changed this. Since this technology is still in its initial development stages, few studies have investigated factors that influence its acceptance. This paper analyzes the predictors of the intention to use non-medical insertable devices in two Latin American contexts. We used partial least squares structural equation modeling to examine whether six constructs predicted intention to use insertable devices. A questionnaire was administered to undergraduate students located in Colombia and Chile (n = 672). We also examined whether these predictors influenced intention differently for both of them. Four common constructs significantly and positively influenced both Chilean and Colombian respondents to use insertable devices (hedonic motivation, habit, performance expectancy, and social influence). Also, the habit has a complementary mediating effect on the relationship between social influence and behavioral intention. By contrast, effort expectations were a positive and significant predictor, but only among Chilean respondents. Findings suggest that when technologies are emerging, well-known predictors of intention (e.g., performance and effort expectations) are less influential than predictors related to self-efficacy (e.g., habit and hedonic motivation). The use of insertable devices has a significant impact on society. Thus, a better understanding of what motivates their use has implications for both academia and industry. 相似文献
2.
This study explored adolescents’ opinions about how Internet use supports the achievement of their developmental tasks. Qualitative data were collected in focus groups interviews with 127 Italian Internet users (11–20) attending middle and high schools. Discussions were recorded, transcribed and analyzed using content analysis. Results showed that the Internet plays important functions in identity formation, personal autonomy, and relationships outside the family. It allows teens to develop their own interests, to identify with others and, at the same time, differentiate from others. The Internet is also an arena in which adolescents develop and practice autonomy. The Internet can be a source of conflict with parents, because of parents’ concerns about Internet use. However, the Internet can also be a meeting ground with parents. Finally, participants indicated the Internet is used to form close relationships with peers. Gender and age differences are discussed. Although the study is cross-sectional and relies only on adolescent report, findings illustrate how the conceptual framework of developmental goals may be helpful for understanding how the Internet can affect adolescents’ lives. 相似文献
3.
4.
在充分调研阵列声波测井分波提取方法的基础上,针对阿特拉斯公司的交叉多极子阵列声波测井(XMACⅡ)提供的单极波形信息,研究纵波时差提取及高分辨率处理方法。首先利用相关-互功谱法高精度地提取纵波时差,然后针对XMACⅡ仪器的接收阵列,研究组合子阵列的方法,形成共发射子阵列和共接收子阵列,最后利用子阵列对提取的纵波时差做高分辨率处理。处理现场实际测井资料,并将高分辨率处理成果与引进的eXpress软件处理成果、实测的国产高分辨率声波(纵波)测井曲线及岩心纵波时差对比分析,表明该方法提取的纵波时差曲线的纵向分辨率有很大提高,时差计算准确可靠,提取的单极纵波时差与国产高分辨率声波时差及岩心纵波时差的平均相对误差均小于7%。该方法具有较高的实用价值和广阔的应用前景。 相似文献
5.
6.
从图像的二维谱可以得出现行广播电视图像为什么不能满足人眼的视觉匹配以及现行电视制度的不足 ,从而对未来的高清晰度电视发展提出要求。 相似文献
7.
8.
浅谈冲压模具的维修要领及常见故障的排除 总被引:1,自引:0,他引:1
介绍冲压模具修理和检查各环节的主要工作内容及维修要领 ,列举了常见故障的排除方法 ,通过总结实际生产中的修模经验 ,对缩短修模周期 ,降低成本 ,延长模具寿命有一定的参考价值。。 相似文献
9.
茅金根 ,梁秀文 ,杨午阳 ,冯有奎 .等偏移距自动初至静校正 .石油地球物理勘探 ,2 0 0 2 ,37(5 ) :4 6 9~ 4 72 本文提出一种自动计算静校正量的新方法。它首先在等偏移距道集内对相邻道的初至波采用高精度相关构建一个关于炮、检时差的超大矩阵方程 ,然后采用优化统计迭代算法求解炮点和检波点的静校正量 ,并用概率分布函数确定精确的炮、检静校正量 ,最后用误差校正函数消除炮、检静校正误差。实际资料处理结果表明 ,本方法自动、省时、精度高。 相似文献
10.
We compare two link analysis ranking methods of web pages in a site. The first, called Site Rank, is an adaptation of PageRank to the granularity of a web site and the second, called Popularity Rank, is based on the frequencies of user clicks on the outlinks in a page that are captured by navigation sessions of users through
the web site. We ran experiments on artificially created web sites of different sizes and on two real data sets, employing
the relative entropy to compare the distributions of the two ranking methods. For the real data sets we also employ a nonparametric
measure, called Spearman's footrule, which we use to compare the top-ten web pages ranked by the two methods. Our main result
is that the distributions of the Popularity Rank and Site Rank are surprisingly close to each other, implying that the topology
of a web site is very instrumental in guiding users through the site. Thus, in practice, the Site Rank provides a reasonable
first order approximation of the aggregate behaviour of users within a web site given by the Popularity Rank. 相似文献