全文获取类型
收费全文 | 556730篇 |
免费 | 48497篇 |
国内免费 | 21032篇 |
专业分类
电工技术 | 29611篇 |
技术理论 | 44篇 |
综合类 | 33569篇 |
化学工业 | 102044篇 |
金属工艺 | 28886篇 |
机械仪表 | 33219篇 |
建筑科学 | 43362篇 |
矿业工程 | 15209篇 |
能源动力 | 15258篇 |
轻工业 | 39187篇 |
水利工程 | 9227篇 |
石油天然气 | 31464篇 |
武器工业 | 3880篇 |
无线电 | 65121篇 |
一般工业技术 | 70051篇 |
冶金工业 | 28018篇 |
原子能技术 | 5464篇 |
自动化技术 | 72645篇 |
出版年
2024年 | 2019篇 |
2023年 | 7490篇 |
2022年 | 13515篇 |
2021年 | 19261篇 |
2020年 | 15277篇 |
2019年 | 14279篇 |
2018年 | 15747篇 |
2017年 | 18126篇 |
2016年 | 16990篇 |
2015年 | 22176篇 |
2014年 | 27465篇 |
2013年 | 34146篇 |
2012年 | 34145篇 |
2011年 | 37515篇 |
2010年 | 33136篇 |
2009年 | 31952篇 |
2008年 | 30785篇 |
2007年 | 29924篇 |
2006年 | 30768篇 |
2005年 | 27130篇 |
2004年 | 18738篇 |
2003年 | 16764篇 |
2002年 | 16214篇 |
2001年 | 14450篇 |
2000年 | 14158篇 |
1999年 | 15137篇 |
1998年 | 12400篇 |
1997年 | 10407篇 |
1996年 | 9567篇 |
1995年 | 7992篇 |
1994年 | 6644篇 |
1993年 | 4923篇 |
1992年 | 3898篇 |
1991年 | 2938篇 |
1990年 | 2261篇 |
1989年 | 1834篇 |
1988年 | 1488篇 |
1987年 | 1049篇 |
1986年 | 787篇 |
1985年 | 624篇 |
1984年 | 414篇 |
1983年 | 333篇 |
1982年 | 295篇 |
1981年 | 243篇 |
1980年 | 210篇 |
1979年 | 132篇 |
1978年 | 74篇 |
1977年 | 76篇 |
1976年 | 92篇 |
1975年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Dong Zhang 《Korean Journal of Chemical Engineering》2008,25(5):1205-1207
Ceria-zirconia solid particles have been recognized as a key material of the automotive exhaust catalysts since they can release
and uptake oxygen owing to the rapid reversible oxidation states of cerium between Ce3+ and Ce4+. Several methods have recently been described to prepare the CeO2-ZrO2 solid particles used in the catalysts. In this paper, a new coprecipitation method is used to prepare the CeO2-ZrO2 solid particles. The Ce-Zr alcogel is dried and calcined in flowing N2 not in flowing air under atmospheric pressure. The results show that the ceria-zirconia sample calcined at 650 °C has high
surface area over 90 m2g−1, which drops to 40 m2g−1 following treatment at 900°C. 相似文献
102.
103.
徐州地区采暖教室内CO2污染影响因素分析 总被引:1,自引:1,他引:0
在徐州市采暖季节期间,实测3所高校3栋教学楼典型教室的室内CO2浓度、室内人员密度、室外空气流速等参数,分析不同状态的教室、不同的人员密度和不同的室外空气流速对室内CO2浓度的影响,提出改善采暖教室内CO2浓度的措施。 相似文献
104.
Fan Zhang To-yat Cheung 《IEEE transactions on pattern analysis and machine intelligence》2003,29(1):1-14
The fault-state detection approach for blackbox testing consists of two phases. The first is to bring the system under test (SUT) from its initial state to a targeted state t and the second is to check various specified properties of the SUT at t. This paper investigates the first phase for testing systems specified as observable nondeterministic finite-state machines with probabilistic and weighted transitions. This phase involves two steps. The first step transfers the SUT to some state t' and the second step identifies whether t' is indeed the targeted state t or not. State transfer is achieved by moving the SUT along one of the paths of a transfer tree (TT) and state identification is realized by using diagnosis trees (DT). A theoretical foundation for the existence and characterization of TT and DT with minimum weighted height or minimum average weight is presented. Algorithms for their computation are proposed. 相似文献
105.
106.
Lie‐Fern Hsu 《Quality and Reliability Engineering International》2007,23(2):269-272
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
107.
磷矿中七种金属元素的光谱法测定 总被引:2,自引:0,他引:2
研究了磷矿样品中7种金属元素锰、钴、镍,锌、铬、钼及铋的分析方法,选择了灵敏度高干扰少的谱线,绘制出工作曲线,对样品进行了科学处理,不必进行化学分离即可对七种元素同时测定,经合成样分析、回收实验及样品测定,证明此方法精确可靠,其回收率在98%-102%之间。 相似文献
108.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
109.
110.
Yun‐Hwei Shen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):581-586
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry 相似文献