全文获取类型
收费全文 | 106208篇 |
免费 | 11413篇 |
国内免费 | 7398篇 |
专业分类
电工技术 | 7314篇 |
技术理论 | 5篇 |
综合类 | 10458篇 |
化学工业 | 9459篇 |
金属工艺 | 8219篇 |
机械仪表 | 8603篇 |
建筑科学 | 18138篇 |
矿业工程 | 5157篇 |
能源动力 | 3058篇 |
轻工业 | 5376篇 |
水利工程 | 5241篇 |
石油天然气 | 6298篇 |
武器工业 | 1848篇 |
无线电 | 6661篇 |
一般工业技术 | 12089篇 |
冶金工业 | 5013篇 |
原子能技术 | 969篇 |
自动化技术 | 11113篇 |
出版年
2024年 | 454篇 |
2023年 | 1442篇 |
2022年 | 3621篇 |
2021年 | 3882篇 |
2020年 | 3749篇 |
2019年 | 3062篇 |
2018年 | 2890篇 |
2017年 | 3772篇 |
2016年 | 4072篇 |
2015年 | 4348篇 |
2014年 | 6545篇 |
2013年 | 6452篇 |
2012年 | 7821篇 |
2011年 | 8266篇 |
2010年 | 6293篇 |
2009年 | 6323篇 |
2008年 | 5812篇 |
2007年 | 6945篇 |
2006年 | 6238篇 |
2005年 | 5450篇 |
2004年 | 4494篇 |
2003年 | 3791篇 |
2002年 | 3250篇 |
2001年 | 2749篇 |
2000年 | 2317篇 |
1999年 | 1898篇 |
1998年 | 1558篇 |
1997年 | 1301篇 |
1996年 | 1208篇 |
1995年 | 976篇 |
1994年 | 785篇 |
1993年 | 595篇 |
1992年 | 520篇 |
1991年 | 353篇 |
1990年 | 330篇 |
1989年 | 283篇 |
1988年 | 169篇 |
1987年 | 118篇 |
1986年 | 93篇 |
1985年 | 65篇 |
1984年 | 72篇 |
1983年 | 35篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 79篇 |
1979年 | 68篇 |
1964年 | 42篇 |
1959年 | 40篇 |
1956年 | 30篇 |
1955年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
通过对国内外大量石油套管螺纹参数的测量和全尺寸的模拟试验,以及对测量和试验数据的理论分析,找出了影响国产套管发生粘扣的原因,并在实际生产中实施验证。采取相应的措施改善了套管的抗粘结性能,同时套管的密封和抗滑脱性能并未下降。 相似文献
12.
介绍了天铁炼钢厂中间包水模实验原理和过程,分析了斜、直、圆三种型式挡渣墙模拟结果,提出了合理的挡渣控流方案,在生产实践中使用效果良好。 相似文献
13.
In this paper we design an experiment which can be depicted as a simple scenario, a very limited 'world'. In this world, there are an actor that can pursue a project and an observer that is keeping its eyes on the actor. We try to show in the experiment that the observer can to some degree understand the actor based on its knowledge and some metaphors, i.e. understand what the actor is doing and why. As the conclusion of this experiment, we try to show some features of 'understanding'. These are (1) that 'understanding' has to be based on some preliminary knowledge; (2) that 'understanding' is a process of incremental learning; (3) that, as for symbolic systems, some metaphors are necessary for mapping real entities into concepts in mind. 相似文献
14.
梁民基 《小型微型计算机系统》1994,15(12):41-46
本文给出了作者开发的一个单处理机实时多任务操作系统的响应性能(响应时间,同步时间)的实验结果和/或估算。与国外同期文献发表的数据相比,指标先进。 相似文献
15.
The results of study of the effects of yttria stabilization (0–6 mol.%) on the room-temperature fracture behavior and toughening mechanisms in zirconia-reinforced MoSi2 are presented in this paper. Transformation toughening is shown to occur only in composites reinforced with zirconia particles stabilized with 2 mol.% yttria. However, the fracture toughness levels are comparable in the other composites with yttria levels between 0 and 6 mol.%. Toughening in the other composites is attributed to the combined effects of residual stress, microcrack shielding/anti-shielding and/or crack deflection. A rigorous micromechanics-based model is presented for the estimation of residual stress levels in brittle materials reinforced with phases that can transform during cooling or under stress. The model is applied successfully to the rationalization of the observed fracture and toughening phenomena. 相似文献
16.
Electronic BITE is poor at identifying hardware failure and in present design approaches tends to create the reviled ‘unconfirmed failure’. A different approach to BITE and unconfirmed failure could improve both operational performance and the cost of maintenance. 相似文献
17.
18.
The causes of lightning outage are subdivided into direct lightning strokes and induced lightning strokes, which are identified by the characteristics of the lightning overvoltage. In the past, lightning protection devices were directed mainly toward the latter, and attention has been focused on the installation of lightning protection devices, ground wires, and reinforcement of insulators. However, lightning outages continue to occur. Thus it is extremely important to clarify the fault characteristics of lightning surges and to study the effectiveness of various lightning protection devices by considering both direct lightning stroke and induced lightning stroke in order to prevent lightning outage in the future. In this research, the electromagnetic transients program (EMTP) has been applied to the direct lightning stroke, and the induced lightning outage analysis program for multiple conductor systems has been applied to the induced lightning stroke to study the effectiveness of lightning protection devices provided by combination of various lightning protection devices. The most effective lightning protection schemes are analyzed and evaluated based on verification tests on the full scale models as well as economic considerations. 相似文献
19.
20.
It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010. 相似文献