全文获取类型
收费全文 | 9200篇 |
免费 | 1399篇 |
国内免费 | 1112篇 |
专业分类
电工技术 | 590篇 |
技术理论 | 1篇 |
综合类 | 924篇 |
化学工业 | 804篇 |
金属工艺 | 247篇 |
机械仪表 | 306篇 |
建筑科学 | 957篇 |
矿业工程 | 416篇 |
能源动力 | 284篇 |
轻工业 | 233篇 |
水利工程 | 299篇 |
石油天然气 | 524篇 |
武器工业 | 57篇 |
无线电 | 1008篇 |
一般工业技术 | 621篇 |
冶金工业 | 514篇 |
原子能技术 | 67篇 |
自动化技术 | 3859篇 |
出版年
2024年 | 89篇 |
2023年 | 227篇 |
2022年 | 568篇 |
2021年 | 600篇 |
2020年 | 498篇 |
2019年 | 338篇 |
2018年 | 284篇 |
2017年 | 374篇 |
2016年 | 453篇 |
2015年 | 420篇 |
2014年 | 657篇 |
2013年 | 515篇 |
2012年 | 674篇 |
2011年 | 663篇 |
2010年 | 574篇 |
2009年 | 532篇 |
2008年 | 535篇 |
2007年 | 599篇 |
2006年 | 541篇 |
2005年 | 512篇 |
2004年 | 409篇 |
2003年 | 331篇 |
2002年 | 291篇 |
2001年 | 216篇 |
2000年 | 176篇 |
1999年 | 111篇 |
1998年 | 100篇 |
1997年 | 91篇 |
1996年 | 66篇 |
1995年 | 58篇 |
1994年 | 41篇 |
1993年 | 35篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1957年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Holahan Matthew R.; Taverna Franco A.; Emrich Stephen M.; Louis Meira; Muller Robert U.; Roder John C.; McDonald Robert J. 《Canadian Metallurgical Quarterly》2005,119(6):1563
Male Long-Evans rats were injected with 32 ng/μl of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediodorsal striatum had similar latencies to locate the platform on the reversal day. Rats infused with CPP into the dorsal hippocampus or mediodorsal striatum failed to search preferentially in the novel location during a 24-hr, drug-free retention test, whereas all other groups searched preferentially in this location. Therefore, blocking dorsal hippocampal or mediodorsal striatal NMDA receptors selectively blocked long-term spatial retention without producing short-term performance deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
142.
Carver Charles S.; Smith Roselyn G.; Antoni Michael H.; Petronis Vida M.; Weiss Sharlene; Derhagopian Robert P. 《Canadian Metallurgical Quarterly》2005,24(5):508
In considering well-being among survivors of life-threatening illnesses such as breast cancer, 2 important questions are whether there is continuity between initial adjustment and longer term adjustment and what role personality plays in long-term adjustment. In this research, a sample of 163 early stage breast cancer patients whose psychosocial adjustment was first assessed during the year after surgery completed the same measures 5-13 years after surgery. Initial reports of well-being were relatively strong predictors of follow-up well-being on the same measures. Initial optimism and marital status also predicted follow-up adjustment, even controlling for earlier adjustment, which exerted a substantial unique effect in multivariate analyses. In contrast, initial medical variables played virtually no predictive role. There is substantial continuity of subjective well-being across many years among survivors of breast cancer, rooted partly in personality and social connection. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
143.
Switch costs in task switching are commonly attributed to an executive control process of task-set reconfiguration, particularly in studies involving the explicit task-cuing procedure. The authors propose an alternative account of explicitly cued performance that is based on 2 mechanisms: priming of cue encoding from residual activation of cues in short-term memory and compound cue retrieval of responses from long-term memory. Their short-term priming account explains the repeated cue encoding benefit, switch cost, reduction in switch cost with preparation time, and other effects. The authors develop a mathematical model of their priming account and fit it to data from 3 experiments, demonstrating that a set of basic psychological processes can produce several effects--including putative switch costs--without switching tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
144.
145.
146.
Topic Identification in Dynamical Text by Complexity Pursuit 总被引:4,自引:0,他引:4
The problem of analysing dynamically evolving textual data has arisen within the last few years. An example of such data is
the discussion appearing in Internet chat lines. In this Letter a recently introduced source separation method, termed as
complexity pursuit, is applied to the problem of finding topics in dynamical text and is compared against several blind separation algorithms
for the problem considered. Complexity pursuit is a generalisation of projection pursuit to time series and it is able to
use both higher-order statistical measures and temporal dependency information in separating the topics. Experimental results
on chat line and newsgroup data demonstrate that the minimum complexity time series indeed do correspond to meaningful topics
inherent in the dynamical text data, and also suggest the applicability of the method to query-based retrieval from a temporally
changing text stream.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
147.
Graphical CASE (Computer Aided Software Engineering) tools provide considerable help in documenting the output of the Analysis and Design stages of software development and can assist in detecting incompleteness and inconsistency in an analysis. However, these tools do not contribute to the initial, difficult stage of the analysis process, that of identifying the object classes, attributes and relationships used to model the problem domain. This paper describes an NL-Based CASE tool called Class Model Builder (CM-Builder) which aims at supporting this aspect of the Analysis stage of software development in an Object-Oriented framework. CM-Builder uses robust Natural Language Processing techniques to analyse software requirements texts written in English and constructs, either automatically or interactively with an analyst, an initial UML Class Model representing the object classes mentioned in the text and the relationships among them. The initial model can be directly input to a graphical CASE tool for further refinement by a human analyst. CM-Builder has been quantitatively evaluated in blind trials against a collection of unseen software requirements texts and we present the results of this evaluation, together with the evaluation method. The results are very encouraging and demonstrate that tools such as CM-Builder have the potential to play an important role in the software development process. 相似文献
148.
This study describes and evaluates twoessay-based discourse analysis systems thatidentify thesis and conclusion statements fromstudent essays written on six different essaytopics. Essays used to train and evaluate thesystems were annotated by two human judges,according to a discourse annotation protocol. Using a machine learning approach, a number ofdiscourse-related features were automaticallyextracted from a set of annotated trainingdata. Using these features, two discourseanalysis models were built using C5.0 withboosting: a topic-dependent and atopic-independent model. Both systemsoutperformed a positional algorithm. While thetopic-dependent system showed somewhat higherperformance, the topic-independent systemshowed similar results, indicating that asystem can generalize to unseen data – thatis, essay responses on topics that the systemhas not seen in training. 相似文献
149.
150.