全文获取类型
收费全文 | 589885篇 |
免费 | 50758篇 |
国内免费 | 28363篇 |
专业分类
电工技术 | 44122篇 |
技术理论 | 80篇 |
综合类 | 68486篇 |
化学工业 | 70778篇 |
金属工艺 | 28702篇 |
机械仪表 | 32331篇 |
建筑科学 | 81726篇 |
矿业工程 | 30210篇 |
能源动力 | 21226篇 |
轻工业 | 37091篇 |
水利工程 | 27325篇 |
石油天然气 | 27413篇 |
武器工业 | 6382篇 |
无线电 | 40526篇 |
一般工业技术 | 45158篇 |
冶金工业 | 32552篇 |
原子能技术 | 6214篇 |
自动化技术 | 68684篇 |
出版年
2024年 | 2329篇 |
2023年 | 6809篇 |
2022年 | 13152篇 |
2021年 | 16333篇 |
2020年 | 16728篇 |
2019年 | 13295篇 |
2018年 | 12715篇 |
2017年 | 16074篇 |
2016年 | 18614篇 |
2015年 | 20442篇 |
2014年 | 37140篇 |
2013年 | 33222篇 |
2012年 | 41067篇 |
2011年 | 44373篇 |
2010年 | 33713篇 |
2009年 | 34992篇 |
2008年 | 32308篇 |
2007年 | 40755篇 |
2006年 | 37734篇 |
2005年 | 32455篇 |
2004年 | 27428篇 |
2003年 | 24228篇 |
2002年 | 19869篇 |
2001年 | 16798篇 |
2000年 | 14208篇 |
1999年 | 11314篇 |
1998年 | 8482篇 |
1997年 | 7308篇 |
1996年 | 6403篇 |
1995年 | 5350篇 |
1994年 | 4722篇 |
1993年 | 3458篇 |
1992年 | 2978篇 |
1991年 | 2239篇 |
1990年 | 1922篇 |
1989年 | 1691篇 |
1988年 | 1265篇 |
1987年 | 853篇 |
1986年 | 683篇 |
1985年 | 608篇 |
1984年 | 529篇 |
1983年 | 399篇 |
1982年 | 322篇 |
1981年 | 256篇 |
1980年 | 254篇 |
1979年 | 166篇 |
1978年 | 89篇 |
1977年 | 103篇 |
1975年 | 87篇 |
1959年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
对耐火材料——棕刚玉粉的质量分析控制,提出了用实用性的检测方法测定其Al2O3含量。通过与国家标准分析方法的对比试验,证实快速实用分析方法测定棕刚玉粉中Al2O3含量是可行的。 相似文献
92.
Morteza Khayrollah Abdollah 《AEUE-International Journal of Electronics and Communications》2008,62(8):588-596
A new open-loop high-speed CMOS sample-and-hold is presented. Based on new method for further reduction of voltage-dependent charge injection, a new CMOS sample-and-hold was designed. Simulation results confirm the effectiveness of this method. Over 10 dB improvement in signal-to-noise ratio, compared to the signal-to-noise ratio of conventional bottom plate sampling S/Hs was achieved with this method. A comparison between newly designed S/H and the bottom-plate sampling S/H is presented. 相似文献
93.
本文分析了锌基合金模具制造及使用过程中容易出现热裂、翘曲、收缩的问题,并提出了解决这些问题的措施。 相似文献
94.
Excel在大学物理实验中的应用 总被引:1,自引:0,他引:1
利用Excel的强大功能,对实验数据进行处理、分析,对实验过程及实验结果的监控。 相似文献
95.
In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability. 相似文献
96.
The introduction of multiple, independent production lines has helped many firms to increase their production flexibility, provide for redundancy when equipment breaks down, reduce idle time and labor costs, and achieve many other benefits. This paper introduces and formalizes the multiple U-line balancing problem. Optimal solution methodologies are provided for Type I (minimize the number of stations for a given cycle time), Type II (minimize the cycle time for a given number of stations), and cost-minimization line-balancing problems. A branch-and-bound algorithm is also developed for the situation in which equipment requirements are dependent on the line configuration and the task assignment to stations. Computational results indicate that the greatest benefit of exploiting multiple lines occurs for smaller cycle-time problems that require higher output. 相似文献
97.
论社区服务产业化 总被引:2,自引:0,他引:2
刘波 《重庆理工大学学报(自然科学版)》2003,17(1):127-131
社区经济作为一种优化的资源配置方式,利用社区服务为载体,将社区内互不相联的各种经济成份变为利益共同体,建立一种新的经济生产方式,从而带动社区乃至更广区域的经济发展。 相似文献
98.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
99.
This article theoretically investigates the drying of uncoated paper with gas-fired infrared (IR) emitters installed within the drying section of a given commercial paper machine. Specifically, it presents the ideal location of two opposing IR emitters within the drying section. The ideal location of the two opposing IR emitters corresponds to the highest machine speed with specified average moisture content of paper sheet at the end of the drying section. This article also presents the average evaporation rate, temperature, and moisture content of the paper sheet as it travels through the drying section with the two opposing IR emitters operating at the optimum location. In addition, the temperature and moisture profiles in the sheet thickness direction, before and after the IR emitters, are provided. This article is not concerned with the potential effects of drying with IR emitters on paper sheet properties and machine runnability issues. 相似文献
100.
Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献