全文获取类型
收费全文 | 120665篇 |
免费 | 3924篇 |
国内免费 | 1889篇 |
专业分类
电工技术 | 2658篇 |
技术理论 | 2篇 |
综合类 | 4504篇 |
化学工业 | 17690篇 |
金属工艺 | 6903篇 |
机械仪表 | 5282篇 |
建筑科学 | 5098篇 |
矿业工程 | 1503篇 |
能源动力 | 1992篇 |
轻工业 | 5843篇 |
水利工程 | 1782篇 |
石油天然气 | 2942篇 |
武器工业 | 207篇 |
无线电 | 13740篇 |
一般工业技术 | 20911篇 |
冶金工业 | 4705篇 |
原子能技术 | 654篇 |
自动化技术 | 30062篇 |
出版年
2024年 | 150篇 |
2023年 | 645篇 |
2022年 | 967篇 |
2021年 | 1434篇 |
2020年 | 1085篇 |
2019年 | 916篇 |
2018年 | 15280篇 |
2017年 | 14391篇 |
2016年 | 10895篇 |
2015年 | 1974篇 |
2014年 | 1970篇 |
2013年 | 2409篇 |
2012年 | 5277篇 |
2011年 | 11783篇 |
2010年 | 10393篇 |
2009年 | 7520篇 |
2008年 | 8746篇 |
2007年 | 9729篇 |
2006年 | 2155篇 |
2005年 | 2980篇 |
2004年 | 2326篇 |
2003年 | 2209篇 |
2002年 | 1543篇 |
2001年 | 969篇 |
2000年 | 1077篇 |
1999年 | 1149篇 |
1998年 | 998篇 |
1997年 | 857篇 |
1996年 | 865篇 |
1995年 | 639篇 |
1994年 | 558篇 |
1993年 | 387篇 |
1992年 | 352篇 |
1991年 | 278篇 |
1990年 | 194篇 |
1989年 | 168篇 |
1988年 | 146篇 |
1987年 | 104篇 |
1986年 | 77篇 |
1985年 | 58篇 |
1984年 | 58篇 |
1982年 | 37篇 |
1968年 | 45篇 |
1967年 | 36篇 |
1966年 | 44篇 |
1965年 | 46篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
We consider the problem of rescheduling trains in the case where one track of a railway section consisting of two tracks
in opposing directions is closed due to construction activities. After presenting an appropriate model for this situation
we derive a polynomial algorithm for the subproblem of finding an optimal schedule with minimal latenesss if the subsequences
of trains for both directions outside the construction site are fixed. Based on this algorithm we propose a local search procedure
for the general problem of finding good schedules and report test results for some real world instances.
Received: December 8, 1999 / Accepted: May 2, 2001 相似文献
92.
An experimental arrangement has been developed for measuring the transient temperature responses and the thermal diffusivities of foil materials in the range of 10 to 300K by using the optical reflectivity technique. The cryogenic system with optical windows is designed to provide temperatures from 10 to 300 K. The front surface of a foil specimen is heated by a pulsed Nd:YAG laser. In situ measurement of the reflectivity of a continuous-wave He–Ne laser at the rear surface is conducted on the microsecond time scale. Using the temperature dependence of reflectivity, the transient temperature response is deduced. The thermal diffusivity is obtained by fitting Parker's formulae to the experimental data on temperature rise. Stainless-steel foils are chosen as samples and are studied in the region from 10 to 300 K. The accuracy is examined by comparing the present results with the theoretical temperature responses and thermal diffusivity data from the literature. Good agreement is observed. 相似文献
93.
94.
Three interesterified vegetable oils (IVOs) prepared from palm, cottonseed, and olive oil, respectively, have been studied for application to Frankfurters. Beef fat (10%) was replaced by one of the IVOs at 20, 60 or 100%. Fatty acid composition of the lipid fraction in the Frankfurters and saturated/unsaturated ratios were established for all batches. We found that total or partial replacement of beef fat by IVOs did not lead to significant changes in appearance, colour, texture, flavour or sensory score. We conclude that IVOs may be successfully applied as beef fat substitutes in Frankfurters. 相似文献
95.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms. 相似文献
96.
97.
һ���꾮Һ�ð�����HML���о� 总被引:3,自引:0,他引:3
钻井液润滑剂是一种重要的钻井液化学处理剂,它的作用是改善钻井液润滑性,降低井壁与钻具(或套管)之间的磨擦,降低钻柱旋转扭矩和起下钻阻力,从而减少卡钻事故的发生。文章根据目前使用的白油钻井液润滑剂存在的不足,提出研制一种新型白油钻井液润滑剂。通过正交实验优选了润滑剂配方。经室内实验和现场实验证明该产品润滑性能好,与钻井液配伍性好,无毒性对环境影响小。 相似文献
98.
99.
Less may not be more,but it still counts: The state of social capital in Yeoville,Johannesburg 总被引:2,自引:2,他引:0
Kirsten Harrison 《Urban Forum》2002,13(1):67-84
100.