全文获取类型
收费全文 | 13685篇 |
免费 | 1392篇 |
国内免费 | 1071篇 |
专业分类
电工技术 | 842篇 |
综合类 | 1806篇 |
化学工业 | 438篇 |
金属工艺 | 200篇 |
机械仪表 | 614篇 |
建筑科学 | 844篇 |
矿业工程 | 342篇 |
能源动力 | 310篇 |
轻工业 | 845篇 |
水利工程 | 403篇 |
石油天然气 | 213篇 |
武器工业 | 195篇 |
无线电 | 1091篇 |
一般工业技术 | 915篇 |
冶金工业 | 1243篇 |
原子能技术 | 57篇 |
自动化技术 | 5790篇 |
出版年
2024年 | 39篇 |
2023年 | 151篇 |
2022年 | 253篇 |
2021年 | 328篇 |
2020年 | 381篇 |
2019年 | 371篇 |
2018年 | 346篇 |
2017年 | 392篇 |
2016年 | 417篇 |
2015年 | 470篇 |
2014年 | 688篇 |
2013年 | 921篇 |
2012年 | 796篇 |
2011年 | 895篇 |
2010年 | 798篇 |
2009年 | 812篇 |
2008年 | 835篇 |
2007年 | 1073篇 |
2006年 | 900篇 |
2005年 | 804篇 |
2004年 | 715篇 |
2003年 | 668篇 |
2002年 | 595篇 |
2001年 | 483篇 |
2000年 | 350篇 |
1999年 | 324篇 |
1998年 | 234篇 |
1997年 | 206篇 |
1996年 | 145篇 |
1995年 | 126篇 |
1994年 | 150篇 |
1993年 | 92篇 |
1992年 | 59篇 |
1991年 | 51篇 |
1990年 | 51篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1966年 | 8篇 |
1955年 | 7篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The authors report a meta-analysis of age differences in everyday problem-solving/decision-making effectiveness (EPSE). Effect sizes were calculated to reflect 3 age group comparisons: old versus young, young versus middle-aged, and middle-aged versus old. Findings from the meta-analysis of 28 separate studies with an aggregate of 4,482 participants do not support theories of preserved EPSE in late adulthood. Although significant age differences of moderate magnitude persisted across methodological and theoretical domains, rating criteria (experimenter vs. participant) emerged as a significant moderator of the effect magnitude and direction. In addition, EPSE in older adults was bolstered when problem content was interpersonal and when samples were highly educated. Finally, the current results support the conceptual integration of findings from the everyday problem-solving and everyday decision-making literatures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
Hovius Marjolijn; Kellenbach Marion L.; Graham Kim S.; Hodges John R.; Patterson Karalyn 《Canadian Metallurgical Quarterly》2003,17(1):100
The authors investigated the impact of semantic knowledge on visual object analysis by assessing the performance of patients with semantic dementia on a different-views object matching test and on 2 object decision tests differing, for example, in whether the nonreal items were nonsense objects or chimeras of 2 real objects. On average, the patients scored normally on both the object matching and the object decision test including nonsense objects but were impaired on the object decision test including chimeras; this latter was also the only visual object test that correlated significantly with degree of semantic impairment. These findings demonstrate that object decision is not a single task or ability and that it is not necessarily independent of conceptual knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
A manufacturability evaluation decision model is formulated and analyzed based on fuzzy logic and multiple attribute decision-making under the concurrent engineering environment. The study emphasizes on the treatment of the linguistic and vagueness at the early product development stage. The study also considers the function integration of the total life cycle of a product. Hence, the integrated decision model covers the multi-level, multi-goal requirements of the products. Multiple criteria such as the goal space, the decision space, the function space, the development (i.e., product & process design) space, and the activity space, are then applied under different analysis of decision-making methods. For instances, the fuzzy multiple attribute decision-making (FMADM) combined with activity-based costing (ABC) can be used in the activity decision space. The fuzzy logic decision model can be applied in the goal decision space. The results of this study point out the importance of early decision making capability. An example of a high-pressure vessel is provided to demonstrate the proposed model for evaluating the manufacturability. 相似文献
34.
随着无线网络所支持的业务种类的增加和具有弹性服务质量要求的业务的大量出现,与服务质量保证密切相关的呼叫接纳控制问题成了近年来无线网络研究的热点之一。本文研究了基于准马尔可夫决策过程方法的多业务最优呼叫接纳控制问题。根据业务的特点,首先引入了带宽分配满意度函数和收益率函数,在此基础上,提出了基于带宽分配满意度的最优带宽分配算法和基于准马尔可夫决策过程方法的最优呼叫接纳控制策略。计算结果表明,本文方案能够在对各类业务的呼叫阻塞率进行适当权衡的前提下,进一步提高网络的期望收益率和期望带宽利用率,同时满足了各类业务的最低服务质量要求。 相似文献
35.
36.
It was hypothesized that exposure to complementary representations of the poor as happier and more honest than the rich would lead to increased support for the status quo. In Study 1, exposure to "poor but happy" and "rich but miserable" stereotype exemplars led people to score higher on a general measure of system justification, compared with people who were exposed to noncomplementary exemplars. Study 2 replicated this effect with "poor but honest" and "rich but dishonest" complementary stereotypes. In Studies 3 and 4, exposure to noncomplementary stereotype exemplars implicitly activated justice concerns, as indicated by faster reaction times to justice-related than neutral words in a lexical decision task. Evidence also suggested that the Protestant work ethic may moderate the effects of stereotype exposure on explicit system justification (but not implicit activation). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
张鸿宾 《计算机应用与软件》1994,11(5):15-19,53
使用BP算法训练多层网络的速度很慢而且事先难于确定隐节点和隐层的适当数目。本文提出一个有效的算法,先构造决策树,然后将构造的决策树转换为神经网。文中使用一个全局准则函数控制决策树的增长,它较好地匹配了树的复杂性和训练样本量及错分率界。实验结果,本文的算法比用BP算法训练多层网络要快,而其分类精度不低于用BP算法训练的多层神经网。 相似文献
38.
本文利用模糊集理论,提出一种非确定环境的描述方法,并且针对机器人在该类环境中的避障轨迹规划,建立了相应的决策函数和规划策略,最后,给出在PC-386计算机上的仿真试验结果。 相似文献
39.
本文讨论了在一条通讯通道上执行基本控制决策的信息传输问题。结果表明当且仅当第一条通道可模拟另一条通道的操作时,则第一条通道在任何情况下比另一条通道都有优势。 相似文献
40.
钢铁企业价格预测决策模型体系研究 总被引:1,自引:0,他引:1
通过对钢铁企业现行价格管理体系的分析 ,建立了钢铁企业价格预测决策模型体系。充分利用大量的定性、定量信息 ,并把趋势预测和因果预测技术相结合 ,采用组合预测模型对价格进行预测 ,最后对预测出来的多方案进行模糊综合评价 ,给出推荐方案顺序。实际应用表明 ,模型体系是有效的。 相似文献