全文获取类型
收费全文 | 38375篇 |
免费 | 5638篇 |
国内免费 | 3262篇 |
专业分类
电工技术 | 1547篇 |
综合类 | 3208篇 |
化学工业 | 2289篇 |
金属工艺 | 4577篇 |
机械仪表 | 3338篇 |
建筑科学 | 805篇 |
矿业工程 | 536篇 |
能源动力 | 463篇 |
轻工业 | 856篇 |
水利工程 | 401篇 |
石油天然气 | 628篇 |
武器工业 | 684篇 |
无线电 | 17137篇 |
一般工业技术 | 4927篇 |
冶金工业 | 933篇 |
原子能技术 | 463篇 |
自动化技术 | 4483篇 |
出版年
2024年 | 281篇 |
2023年 | 796篇 |
2022年 | 1158篇 |
2021年 | 1381篇 |
2020年 | 1361篇 |
2019年 | 1212篇 |
2018年 | 1138篇 |
2017年 | 1454篇 |
2016年 | 1517篇 |
2015年 | 1674篇 |
2014年 | 2096篇 |
2013年 | 2257篇 |
2012年 | 2642篇 |
2011年 | 2593篇 |
2010年 | 1927篇 |
2009年 | 1929篇 |
2008年 | 2257篇 |
2007年 | 2677篇 |
2006年 | 2371篇 |
2005年 | 2055篇 |
2004年 | 1836篇 |
2003年 | 1579篇 |
2002年 | 1327篇 |
2001年 | 1283篇 |
2000年 | 1045篇 |
1999年 | 900篇 |
1998年 | 711篇 |
1997年 | 661篇 |
1996年 | 596篇 |
1995年 | 519篇 |
1994年 | 485篇 |
1993年 | 421篇 |
1992年 | 332篇 |
1991年 | 280篇 |
1990年 | 201篇 |
1989年 | 96篇 |
1988年 | 72篇 |
1987年 | 27篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1963年 | 3篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
飞秒激光烧蚀研究进展 总被引:10,自引:3,他引:7
介绍飞秒激光烧蚀材料的机理论模型,阐述飞秒激光烧蚀的特性,揭示飞秒激光烧蚀的广泛应用前景。 相似文献
93.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
94.
CDMA通信系统的MATLAB仿真 总被引:7,自引:0,他引:7
在简要介绍MATLAB语言的基础上,对使用MATLAB语方仿真的CDMA通信系统进行描述。 相似文献
95.
本文提出一种多输入多输出(MIMO)天线系统中简单的扩展空时块编码(SSTBC)分集技术,采用沃尔什码来区分各天线发送数据子流。采用这种方法,在系统带宽一定时,不降低发送信息速率,同时接收机简单。不同天线的发送信息经过了所有收一发天线对之间的空间子信道,获得了所有路径的部分空间分集增益,仿真结果表明,这种增益的获得不受限于接收分集阶数,并且随发射天线的增加以一定的线性关系增加。 相似文献
96.
A high-density gas jet supersonic nozzle is reported in this paper. The jitter and actuation time of the nozzle is determined by the pin discharge and laser spark radiation respectively. The jitter time of the nozzle is within 10μs with the backing pressure as high as 25 bar. With a nanosecond laser pulse focused on the gas jet about 1 mm below the nozzle, the actuation time is calculated to be about 15 ms by detecting the laser produced spark radiation, which reveals the existence of the gas jet and the relative gas density evolving with time. Consequently the gas density is estimated to be well above 10^19 cm^-3, compared with theoretical simulations from the nozzle parameters. 相似文献
97.
A manufacturability evaluation decision model is formulated and analyzed based on fuzzy logic and multiple attribute decision-making under the concurrent engineering environment. The study emphasizes on the treatment of the linguistic and vagueness at the early product development stage. The study also considers the function integration of the total life cycle of a product. Hence, the integrated decision model covers the multi-level, multi-goal requirements of the products. Multiple criteria such as the goal space, the decision space, the function space, the development (i.e., product & process design) space, and the activity space, are then applied under different analysis of decision-making methods. For instances, the fuzzy multiple attribute decision-making (FMADM) combined with activity-based costing (ABC) can be used in the activity decision space. The fuzzy logic decision model can be applied in the goal decision space. The results of this study point out the importance of early decision making capability. An example of a high-pressure vessel is provided to demonstrate the proposed model for evaluating the manufacturability. 相似文献
98.
激光武器对抗效能指标体系研究 总被引:1,自引:0,他引:1
武器系统的效能是规划、研制、配置和部署武器系统的基本依据,是评价武器系统优劣最重要的综合性指标,建立正确的效能指标体系是进行效能分析与评价的前提。在详细研究了激光武器对抗机理、效能指标选用原则的基础上,构建了相对完整的激光武器对抗效能指标体系结构,并提出了在不同作战任务下量度激光武器对抗能力的效能定义。 相似文献
99.
100.
D. Knig S. Carvajal-Gonzalez A. M. Downs J. Vassy P. Rigaut 《Journal of microscopy》1991,161(3):405-433
Within the concept of point processes, a review is presented of quantities which can be used in studies of three-dimensional (3-D) aggregates of particles. Suitable characteristics and estimators are given for both unmarked and marked point processes. To demonstrate the feasibility of such quantitative approaches, an application in histology, dealing with 3-D arrangements of cell nuclei in rat liver, is described. Using a confocal scanning light microscope, 3-D images are recorded and image analysis used to obtain the coordinates of the centroid, together with the volume and DNA content, of each cell nucleus. Examples of results are given, using both unmarked and marked point processes. In the latter case, cell type, nuclear volume and ploidy group are suitable marks. 相似文献