全文获取类型
收费全文 | 32556篇 |
免费 | 3571篇 |
国内免费 | 1904篇 |
专业分类
电工技术 | 1665篇 |
综合类 | 3395篇 |
化学工业 | 3831篇 |
金属工艺 | 1119篇 |
机械仪表 | 1757篇 |
建筑科学 | 5115篇 |
矿业工程 | 1517篇 |
能源动力 | 893篇 |
轻工业 | 1551篇 |
水利工程 | 1427篇 |
石油天然气 | 2350篇 |
武器工业 | 680篇 |
无线电 | 2486篇 |
一般工业技术 | 3965篇 |
冶金工业 | 1916篇 |
原子能技术 | 582篇 |
自动化技术 | 3782篇 |
出版年
2024年 | 100篇 |
2023年 | 373篇 |
2022年 | 696篇 |
2021年 | 974篇 |
2020年 | 927篇 |
2019年 | 831篇 |
2018年 | 864篇 |
2017年 | 1092篇 |
2016年 | 1291篇 |
2015年 | 1299篇 |
2014年 | 1844篇 |
2013年 | 1784篇 |
2012年 | 1978篇 |
2011年 | 2474篇 |
2010年 | 1810篇 |
2009年 | 1910篇 |
2008年 | 1834篇 |
2007年 | 2035篇 |
2006年 | 2006篇 |
2005年 | 1680篇 |
2004年 | 1391篇 |
2003年 | 1265篇 |
2002年 | 1158篇 |
2001年 | 1012篇 |
2000年 | 765篇 |
1999年 | 632篇 |
1998年 | 456篇 |
1997年 | 365篇 |
1996年 | 322篇 |
1995年 | 274篇 |
1994年 | 218篇 |
1993年 | 173篇 |
1992年 | 144篇 |
1991年 | 134篇 |
1990年 | 124篇 |
1989年 | 75篇 |
1988年 | 68篇 |
1987年 | 56篇 |
1986年 | 50篇 |
1985年 | 153篇 |
1984年 | 251篇 |
1983年 | 286篇 |
1982年 | 211篇 |
1981年 | 309篇 |
1980年 | 129篇 |
1979年 | 45篇 |
1978年 | 38篇 |
1977年 | 13篇 |
1975年 | 21篇 |
1974年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
符金开 《湖南冶金职业技术学院学报》2004,(1)
为了降低气体悬浮焙烧炉焙烧过程中Al_2O_3粒度的破损,对气体悬浮焙烧炉焙烧过程中氧化铝粒度的影响因素进行了分析,提出了降低粒度破损的一些措施。 相似文献
83.
84.
85.
Berrin-Wasserman Stacy; Winnick Wilma A.; Borod Joan C. 《Canadian Metallurgical Quarterly》2003,17(3):429
Does sentence generation and/or stimulus emotionality enhance verbal memory in patients with neurological impairment? This question was addressed by testing 40 patients with unilateral stroke (20 with left-brain and 20 with right-brain damage) and 20 healthy control participants for recall and recognition of 48 target words. During encoding, emotional and nonemotional words were either presented in sentences (read condition) or used to form sentences (generate condition). Both word emotionality and generative processing improved memory performance in all groups. The authors suggest that a similar influence (i.e., cognitive activation) underlies both of these memory-enhancing effects, although the putative origins of the 2 effects are quite different. Neuropsychological underpinnings and clinical implications of these phenomena are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
对小型中间下料预焙电解槽技术条件摆布的原则和具体数据进行了探讨,提出了尽可能利用从大型预焙槽上得出的先进经验,并消化吸收,掌握好各种条件的平衡,以取得好经济技术指标的观点。 相似文献
87.
Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO2 620 mm Hg) or with 100% nitrogen (PO2 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO2 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible. 相似文献
88.
Per Hovstad Liching Sung 《International Journal of Satellite Communications and Networking》2005,23(2):91-110
The 1977 Broadcasting‐Satellite Service (BSS) Plan for Region 1 & 3 had been widely acknowledged to be out‐of‐date by the late 1980s. Development of digital modulation in the early 1990s provided an opportunity to update the technical provisions of the Plan to make it more economically viable. After a decade of work and three World Radiocommunication Conferences (WRCs), the revision of Region 1 & 3 BSS Plan was finally completed in 2003. The new Plan increased channel assignments from 5 to 10 analog‐equivalent channels for each country in Region 1, and from 4 to 12 channels for each country in Region 3. Yet, despite the increase in capacity, the new Plan is surprisingly similar to the original one in terms of the technical parameters. It is still based on national coverage, and the channel plan, orbital location, orbital spacing, and polarization are also the same. As a result, the new Plan is no more economically viable to implement than the old. To create economically viable BSS systems would most likely require modifications to the assignment in the Plan. Yet, modification procedures were made more difficult to apply after replanning. Less future implementation of BSS networks than would otherwise have occurred can be expected, and an inefficient usage of these frequency bands will likely result. On the other hand, less implemented systems will mean more capacity set aside for future use. This is important for countries that currently do not have satellite operations. In the end, BSS replanning reflects the eternal conflict between efficient usage and guaranteed future access. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
89.
李桂敏 《中国材料科技与设备》2007,4(4):92-93
本文介绍了一种作业效率高、省时省力新型的转炉炉底车,其特点是转盘转动灵活,炉底车上项盘径向任意方向均能平稳倾斜一定角度,以保证炉底圆周所受项力均匀可靠,满足炉底安装要求。 相似文献
90.
In many legal proceedings, fact finders scrutinize the demeanor of a defendant or witness, particularly his or her nonverbal behavior, for indicators of deception. This meta-analysis investigated directly observable nonverbal correlates of deception as a function of different moderator variables. Although lay people and professionals alike assume that many nonverbal behaviors are displayed more frequently while lying, of 11 different behaviors observable in the head and body area, only 3 were reliably associated with deception. Nodding, foot and leg movements, and hand movements were negatively related to deception in the overall analyses weighted by sample size. Most people assume that nonverbal behaviors increase while lying; however, these behaviors decreased, whereas others showed no change. There was no evidence that people avoid eye contact while lying, although around the world, gaze aversion is deemed the most important signal of deception. Most effect sizes were found to be heterogeneous. Analyses of moderator variables revealed that many of the observed relationships varied as a function of content, motivation, preparation, sanctioning of the lie, experimental design, and operationalization. Existing theories cannot readily account for the heterogeneity in findings. Thus, practitioners are cautioned against using these indicators in assessing the truthfulness of oral reports. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献