全文获取类型
收费全文 | 79605篇 |
免费 | 7636篇 |
国内免费 | 3959篇 |
学科分类
工业技术 | 91200篇 |
出版年
2024年 | 441篇 |
2023年 | 1558篇 |
2022年 | 2851篇 |
2021年 | 3785篇 |
2020年 | 2893篇 |
2019年 | 2319篇 |
2018年 | 2568篇 |
2017年 | 2809篇 |
2016年 | 2460篇 |
2015年 | 3472篇 |
2014年 | 4144篇 |
2013年 | 4876篇 |
2012年 | 5339篇 |
2011年 | 5557篇 |
2010年 | 5116篇 |
2009年 | 4787篇 |
2008年 | 4743篇 |
2007年 | 4255篇 |
2006年 | 4245篇 |
2005年 | 3477篇 |
2004年 | 2400篇 |
2003年 | 2112篇 |
2002年 | 2270篇 |
2001年 | 1991篇 |
2000年 | 1725篇 |
1999年 | 1827篇 |
1998年 | 1332篇 |
1997年 | 1130篇 |
1996年 | 1039篇 |
1995年 | 829篇 |
1994年 | 718篇 |
1993年 | 490篇 |
1992年 | 422篇 |
1991年 | 289篇 |
1990年 | 234篇 |
1989年 | 191篇 |
1988年 | 121篇 |
1987年 | 99篇 |
1986年 | 68篇 |
1985年 | 52篇 |
1984年 | 34篇 |
1983年 | 26篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 27篇 |
1979年 | 10篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Homophily of Network Ties and Bonding and Bridging Social Capital in Computer-Mediated Distributed Teams 总被引:1,自引:0,他引:1
This research studied homophily of network ties in distributed teams in both task-related instrumental networks and non-task related expressive networks. Homophily of network ties was examined in terms of demographic and social characteristics, including gender, race, geographic location, and group assignment. Social network data were collected from 32 students enrolled in a distance learning class from two universities. MQAP regression analysis showed that homophily in gender and in race had no significant impact on the development of either instrumental or expressive ties. In instrumental networks, both homophily in group assignment and in location had significant impact on the development of network ties. In expressive networks, homophily in location had significant impact on the development of network ties, but the impact of homophily in group membership was only marginally significant. Further analysis of bonding ties with people of the same group and bridging ties with people from different groups showed that bonding social capital can exert significant influence on performance. 相似文献
72.
胜科1井钻井事故的预防与处理 总被引:2,自引:1,他引:1
胜科1井设计井深7 000 m,完钻井深7 026 m。在该井钻井过程中,针对上部大尺寸钻头破岩效率低、大井眼井壁稳定性差、大段盐膏层、膏岩层的塑性蠕变和塑性流动造成井眼复杂、超深井高温高压给钻井液性能的控制和水泥浆调控等带来的一系列技术难题,制定了一整套预防井下事故和复杂情况的技术措施,从而确保了该井的钻探成功。该井在钻井过程发生了2次断钻具事故和1次卡钻事故,根据超深井的特点,采取了较为稳妥的处理措施,同时,有针对性地研制了高效铣环和PDC钻头专用打捞器,3次事故处理均获得了成功,共耗时38.5 d。详细介绍了该井所采取的预防和处理钻井事故的技术措施,可为其他超深井的钻井施工提供一定的借鉴。 相似文献
73.
74.
In this paper, a novel approach of automated multirobot nanoassembly planning is presented. This approach uses an improved self-organizing map to coordinate assembly tasks of nanorobots while generating optimized motion paths at run time with a modified shunting neural network. It is capable of synchronizing multiple nanorobots working simultaneously and efficiently on the assembly of swarms of objects in the presence of obstacles and environmental uncertainty. Operation of the presented approach is demonstrated with experiments at the end of the paper. 相似文献
75.
This paper deals with the trajectory planning problem for redundant manipulators. A genetic algorithm (GA) using a floating point representation is proposed to search for the optimal end-effector trajectory for a redundant manipulator. An evaluation function is defined based on multiple criteria, including the total displacement of the end-effector, the total angular displacement of all the joints, as well as the uniformity of Cartesian and joint space velocities. These criteria result in minimized, smooth end-effector motions. Simulations are carried out for path planning in free space and in a workspace with obstacles. Results demonstrate the effectiveness and capability of the proposed method in generating optimized collision-free trajectories. 相似文献
76.
袁永强 《有色冶金设计与研究》2003,24(3):39-42
结合工程实例,对采用传统的短木桩加新兴的土工合成材料——土工网及碎石垫层构成复合基础,处理河岸挡墙软基进行探讨,该方法在软土层厚度不超过4.0m的条件下,技术可靠,施工简单,工期短,造价低。 相似文献
77.
78.
79.
按照2000年示范电厂的思路,电厂MIS已经作为电厂建设的一部分被列入基建程序。面对电力行业重组的新局面,为了提高电厂MIS设计水平,更好地为业主服务,以适应当前日益激烈的竞争,适时地总结电厂MIS设计中的共性问题是很有必要的。文中叙述的内容不是探讨如何设计电厂MIS,而是就设计中容易出现的问题进行研讨。 相似文献
80.
Jia-sheng Tian Tian-lin Dong 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(6):981-988
Based on the established rigorous theory for two-dimensionally periodic (2DP) medium, Longitudinal propagation in Dielectric Waveguide Array (DWA) was analyzed in detail. Firstly, given longitudinal wave vector (k z), Brillouin dispersion relations between transversal wave vectors were analyzed. Interactions between space harmonics were also studied. Secondly, on condition that transversal wave vector k x equaled k y, dispersion relations between longitudinal and transversal wave vectors were analyzed in detail. Because of interactions between space harmonics increasingly getting stronger with k z or modulation coefficients increasing, stop-bands could be distinctly displayed and thus longitudinal propagation in DWA could be comprehensively analyzed. The applications about longitudinal propagation in DWA were also discussed. 相似文献