全文获取类型
收费全文 | 268518篇 |
免费 | 21182篇 |
国内免费 | 13975篇 |
学科分类
工业技术 | 303675篇 |
出版年
2024年 | 832篇 |
2023年 | 2555篇 |
2022年 | 4926篇 |
2021年 | 5917篇 |
2020年 | 6321篇 |
2019年 | 5331篇 |
2018年 | 5030篇 |
2017年 | 6124篇 |
2016年 | 7262篇 |
2015年 | 8161篇 |
2014年 | 14932篇 |
2013年 | 13560篇 |
2012年 | 17756篇 |
2011年 | 18856篇 |
2010年 | 15033篇 |
2009年 | 15696篇 |
2008年 | 14716篇 |
2007年 | 19241篇 |
2006年 | 18248篇 |
2005年 | 15953篇 |
2004年 | 13583篇 |
2003年 | 12290篇 |
2002年 | 10097篇 |
2001年 | 8590篇 |
2000年 | 7254篇 |
1999年 | 5920篇 |
1998年 | 4461篇 |
1997年 | 3928篇 |
1996年 | 3645篇 |
1995年 | 3086篇 |
1994年 | 2738篇 |
1993年 | 2046篇 |
1992年 | 1838篇 |
1991年 | 1363篇 |
1990年 | 1180篇 |
1989年 | 1041篇 |
1988年 | 839篇 |
1987年 | 581篇 |
1986年 | 430篇 |
1985年 | 359篇 |
1984年 | 338篇 |
1983年 | 241篇 |
1982年 | 219篇 |
1981年 | 169篇 |
1980年 | 132篇 |
1979年 | 114篇 |
1978年 | 62篇 |
1977年 | 72篇 |
1976年 | 55篇 |
1975年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
3.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。 相似文献
4.
5.
6.
7.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation. 相似文献
8.
Specialized varieties of sugar beets (Beta vulgaris L.) may be an eligible feedstock for advanced biofuel designation under the USA Energy Independence and Security Act of 2007. These non-food industrial beets could double ethanol production per hectare compared to alternative feedstocks. A mixed-integer mathematical programming model was constructed to determine the breakeven price of ethanol produced from industrial beets, and to determine the optimal size and biorefinery location. The model, based on limited field data, evaluates Southern Plains beet production in a 3-year crop rotation, and beet harvest, transportation, and processing. The optimal strategy depends critically on several assumptions including a just-in-time harvest and delivery system that remains to be tested in field trials. Based on a wet beet to ethanol conversion rate of 110 dm3 Mg−1 and capital cost of 128 M$ for a 152 dam3 y−1 biorefinery, the estimated breakeven ethanol price was 507 $ m−3. The average breakeven production cost of corn (Zea mays L.) grain ethanol ranged from 430 to 552 $ m−3 based on average net corn feedstock cost of 254 and 396 $ m−3 in 2014 and 2013, respectively. The estimated net beet ethanol delivered cost of 207 $ m−3 was lower than the average net corn feedstock cost of 254–396$ m−3 in 2013 and 2014. If for a mature industry, the cost to process beets was equal to the cost to process corn, the beet breakeven ethanol price would be $387 m-3 (587 $ m−3 gasoline equivalent). 相似文献
10.
Salman M.A. Salman 《国际水资源开发杂志》2015,31(1):4-16
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter. 相似文献