全文获取类型
收费全文 | 11022篇 |
免费 | 662篇 |
国内免费 | 308篇 |
专业分类
电工技术 | 383篇 |
综合类 | 379篇 |
化学工业 | 1630篇 |
金属工艺 | 437篇 |
机械仪表 | 426篇 |
建筑科学 | 612篇 |
矿业工程 | 156篇 |
能源动力 | 308篇 |
轻工业 | 546篇 |
水利工程 | 127篇 |
石油天然气 | 292篇 |
武器工业 | 34篇 |
无线电 | 1490篇 |
一般工业技术 | 1324篇 |
冶金工业 | 2561篇 |
原子能技术 | 79篇 |
自动化技术 | 1208篇 |
出版年
2024年 | 18篇 |
2023年 | 113篇 |
2022年 | 194篇 |
2021年 | 315篇 |
2020年 | 191篇 |
2019年 | 191篇 |
2018年 | 255篇 |
2017年 | 254篇 |
2016年 | 268篇 |
2015年 | 260篇 |
2014年 | 390篇 |
2013年 | 559篇 |
2012年 | 500篇 |
2011年 | 621篇 |
2010年 | 555篇 |
2009年 | 520篇 |
2008年 | 575篇 |
2007年 | 459篇 |
2006年 | 468篇 |
2005年 | 341篇 |
2004年 | 302篇 |
2003年 | 308篇 |
2002年 | 275篇 |
2001年 | 231篇 |
2000年 | 215篇 |
1999年 | 279篇 |
1998年 | 945篇 |
1997年 | 509篇 |
1996年 | 428篇 |
1995年 | 265篇 |
1994年 | 229篇 |
1993年 | 214篇 |
1992年 | 74篇 |
1991年 | 72篇 |
1990年 | 70篇 |
1989年 | 70篇 |
1988年 | 64篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 27篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 21篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1977年 | 30篇 |
1976年 | 116篇 |
1975年 | 9篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
61.
62.
陈籁民 《建筑科学与工程学报》1996,(2)
基圆半径的确定方法,除了用图解法和试算法外,还可用解析法和图解分析法求解。4种方法各有优缺点,设计时要根据具体情况选择。 相似文献
63.
64.
SH Braat B Leclercq R Itti A Lahiri B Sridhara P Rigo 《Canadian Metallurgical Quarterly》1994,35(10):1581-1585
There is no evidence of myocardial redistribution after tetrofosmin injection, therefore, two separate injections are needed to differentiate scar from ischemia with this tracer. The injections can be given on the same day (one-day protocol) or on separate days (two-day protocol). As part of a Phase II clinical study, a one-day protocol was compared with a two-day protocol. METHODS: Fifty-five patients with suspected coronary artery disease were studied according to the following protocol: on the first day at rest, anterior, left lateral, left anterior oblique 40 degrees and 70 degrees images were acquired 30 min after injection of 8 mCi of tetrofosmin for 5 min each. Two days later, exercise and rest images were acquired on the same day. At peak exercise, 8 mCi of tetrofosmin were injected and 30 min later the same four standard planar images were recorded as on Day one. Four hours after the exercise injection, 24 mCi of tetrofosmin were injected at rest and imaging was repeated 30 min later. Qualitative comparisons between the one- and two-day protocols were performed in 50 patients in whom all data were available following blinded evaluation of images by three readers. RESULTS: All three readers reported identical results for the 26 patients. A difference in extent or location between the observers was found in seven patients, differences between normal and abnormal in eight patients, while discrepancies between ischemia and necrosis were noted in four patients. In five patients, an ischemic area was found according to the one-day protocol, but according to the data of the two-day protocol, this area was judged to be necrotic. One observer reported the opposite in one patient. These discrepancies between the reversibility of defects were restricted to the inferior wall. Comparison with 201Tl data showed no systematic pattern of variation. CONCLUSION: Tetrofosmin can be used in a one-day protocol. However, in planar imaging, the inferior wall should be reported with caution. 相似文献
65.
许多国家大多没有严格意义上的保健品概念,美国等国家将其统称为“功能食品”。我国应用“保健品”一词,旨在将其与药品和食品两大门类区分开来。美国的“保健品”发展速度和规模比较大,同时由于其先进的制造和科研技术,引领着世界功能食品的潮流。随着我国社会的发展,保健品的生产和研发也逐步赶上国际的步伐,而大量的进口保健品也已经进入寻常百姓家。 相似文献
66.
中频反应溅射SiO2膜与直流溅射ITO膜的在线联镀 总被引:2,自引:2,他引:0
多数ITO透明导电玻璃生产线在实现SiO2膜与ITO膜在线联镀时,应用SiO2靶射频溅射沉积SiO2膜工艺和ITO靶直流溅射沉积ITO膜工艺,如果SiO2膜应用硅靶反应磁控溅射工艺,存在这种工艺是否可以与ITO靶直流溅射沉积ITO膜工艺在线联用以及如何实现联用的问题。作者对现有的生产线进行了改造设计、加工,做了大量实验、质谱分析和多项测试研究,成功地实现反应溅射SiO2膜与ITO膜在线联镀,做到SiO2镀膜室的工作状态的变化基本上不影响ITO镀膜室的工艺条件。 相似文献
67.
68.
69.
DO浓度对SUFR系统同步硝化反硝化的影响 总被引:1,自引:1,他引:0
采用螺旋升流式反应器(SUFR)处理生活污水,考察了好氧反应池中DO浓度对其同步硝化反硝化的影响。结果表明,在好氧反应池上部溶解氧浓度为3.0~3.5mg/L时,发生了明显的同步硝化反硝化现象,其对TN的去除量占SUFR系统对TN去除总量的16%左右;好氧反应池中的同步硝化反硝化反应只发生在池的下部,其中、上部只进行了好氧硝化反应;SUFR系统中好氧反应池上部的最佳溶解氧浓度范围为3.0~3.5mg/L,此时系统的硝化和反硝化效果最佳,好氧反应池中的脱氮效果也较好,系统对TN的去除率〉84%。 相似文献
70.
Hsin-Yi Lai Chin-Tzwu Huang 《The International Journal of Advanced Manufacturing Technology》2007,31(11-12):1109-1126
This paper presents a new MSDI (mold surface data integration) method for presenting ruled mold-surface data for CAPP applications. The method makes use of adjacency and feature-data matrices to establish a framework of feature-based data. The MSDI method enables the storage, retrieval and operations of geometries, topologies, and machining information of a given ruled mold surface. The matrices of adjacency and feature-data effectively represent the relations. Boolean algebra and group technology (GT) methods are introduced to generate the desired process plans. A sample mold made of ruled surfaces is made and used to show the effectiveness of the proposed data representation and the integrated mold surface processing method. A compact computer program is implemented to enhance the speed and accuracy of the MSDI method. The numerical results indicate that the mold surface decomposition and integration procedure presented in this paper are systematic and effective. The paper provides a novel modular mold surface modeling tool and procedure that can be further extended to accommodate more features appearing in complicated ruled mold surfaces. 相似文献