全文获取类型
收费全文 | 27905篇 |
免费 | 2520篇 |
国内免费 | 1417篇 |
专业分类
电工技术 | 1742篇 |
技术理论 | 1篇 |
综合类 | 1986篇 |
化学工业 | 4639篇 |
金属工艺 | 1454篇 |
机械仪表 | 1784篇 |
建筑科学 | 2167篇 |
矿业工程 | 911篇 |
能源动力 | 767篇 |
轻工业 | 2478篇 |
水利工程 | 543篇 |
石油天然气 | 1760篇 |
武器工业 | 206篇 |
无线电 | 2795篇 |
一般工业技术 | 2974篇 |
冶金工业 | 1320篇 |
原子能技术 | 320篇 |
自动化技术 | 3995篇 |
出版年
2024年 | 141篇 |
2023年 | 505篇 |
2022年 | 891篇 |
2021年 | 1190篇 |
2020年 | 864篇 |
2019年 | 739篇 |
2018年 | 845篇 |
2017年 | 932篇 |
2016年 | 828篇 |
2015年 | 1107篇 |
2014年 | 1476篇 |
2013年 | 1793篇 |
2012年 | 1865篇 |
2011年 | 2140篇 |
2010年 | 1828篇 |
2009年 | 1767篇 |
2008年 | 1787篇 |
2007年 | 1616篇 |
2006年 | 1541篇 |
2005年 | 1381篇 |
2004年 | 921篇 |
2003年 | 758篇 |
2002年 | 715篇 |
2001年 | 625篇 |
2000年 | 612篇 |
1999年 | 579篇 |
1998年 | 450篇 |
1997年 | 412篇 |
1996年 | 349篇 |
1995年 | 283篇 |
1994年 | 255篇 |
1993年 | 170篇 |
1992年 | 147篇 |
1991年 | 82篇 |
1990年 | 66篇 |
1989年 | 38篇 |
1988年 | 47篇 |
1987年 | 28篇 |
1986年 | 15篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
82.
熔喷生产最终产品质量的控制,对于过程优化具有重要的意义。产品质量的在线检测是过程监测与质量控制必不可少的。本文首次在熔喷系统中引入人工智能的研究方法,对熔喷非织造布的厚度与纤维直径进行在线预测。实测数据与人工神经网络的预测结果吻合较好,从而证实了人工神经网络用于模拟熔喷过程的可行性。网络的输入包括:挤出机温度、喷头温度、熔融体挤出速率、空气流率及接收距离。神经元计算的输出是纤维直径与熔喷非织布的厚度。文中进一步提出了将神经网络与专家系统相结合的研究路线,以实现熔喷过程的优化控制。 相似文献
83.
Randomized trial of breast self-examination in Shanghai: methodology and preliminary results 总被引:3,自引:0,他引:3
DB Thomas DL Gao SG Self CJ Allison Y Tao J Mahloch R Ray Q Qin R Presley P Porter 《Canadian Metallurgical Quarterly》1997,89(5):355-365
BACKGROUND: The efficacy of breast self-examination in helping to reduce mortality from breast cancer has not been rigorously demonstrated. PURPOSE: To assess efficacy, a large, randomized trial was initiated in Shanghai, China. METHODS: From October 1989 to October 1991, 267040 current and retired female employees associated with 520 factories in the Shanghai Textile Industry Bureau were randomly assigned on the basis of factory to either a self-examination instruction group (133375 women) or a control group (133665 women). The women were born within the period from 1925 through 1958. Women in the instruction group were given intensive training in breast self-examination, including the use of silicone breast models and personalized instruction, plus two subsequent reinforcement sessions and multiple reminders to practice the technique. Women in the control group were asked to attend training sessions on the prevention of low back pain. All women have been followed for the development of breast diseases and for death from breast cancer. RESULTS: A high level of participation during the first 4-5 years of the trial was documented among women in the instruction group. Randomly sampled women in this group demonstrated greater proficiency in detecting lumps in breast models than did randomly sampled women in the control group. Approximately equal numbers of breast cancers were detected in the two groups (331 in the instruction group and 322 in the control group) through 1994, which is the last year for which case-finding efforts have been completed. The breast cancers detected in the instruction group were not diagnosed at an appreciably earlier stage or smaller size than those in the control group. More benign breast lesions were detected in the instruction group than in the control group (1457 versus 623, respectively), suggesting a higher index of suspicion for women who received training. Cumulative breast cancer mortality rates through 5 years from entry into the study were nearly equivalent for the two groups. CONCLUSIONS: Breast self-examination has not led to a reduction in mortality from breast cancer in this study cohort in the first several years since the trial began. A shift toward the diagnosis of disease at a less advanced stage in women given instruction has also not been demonstrated. Longer follow-up of participants in this trial is required before final assessment can be made of the efficacy of breast self-examination. IMPLICATIONS: At this time, there is insufficient evidence to recommend for or against the teaching of breast self-examination. 相似文献
84.
This paper presents stability results for discrete-time model-based predictive control system subject to an input amplitude constraint. It is shown that the input amplitude constrained control system may provide a stable control system in the sense of BIBO when the system to be controlled is of a class of the system poles which consist of multiple integrators and a stable polynomial. The solution of Diophantine equations and their properties are addressed. Simulation study is also carried out and it is shown that the output of the system may converge to the reference signal for certain degree of constraints. 相似文献
85.
随着计算机技术的发展和水平的提高,图像,声音,图形等多媒体信息逐步应用于管理信息系统之中。文章中提出了图文数据库系统设计中存在的三个基本问题。讨论了介绍了图文数据库系统的设计方法和实现技术。 相似文献
86.
由电压型运算放大器组成的精密整流电路要严格地匹配电阻才能获得精密全波整流波形.本文给出一种具有CCⅡ电路特性由运算放大器AD844所构成的电流模精密整流电路.无需匹配电阻就可输出良好的精密全波整流波形.且具有输入电压范围大,频带宽等特点. 相似文献
87.
在已经得到的描述鱼雷罐喷粉处理基本参数具体表达式的基础上,运用多目标非线性优化方法,对工艺操作参数进行优化。 相似文献
88.
The synthesis of rare-earth perovskite-type composition thin films of LaNiO3 by means of the inorganic-sol-gel (ISG) method was studied. The structural stability under high temperature in reducing atmospheres and the oxygen-sensitivity mechanism of the LaNiO3 thin films were examined. It is shown that under the experimental conditions, LaNiO3 decomposes and the valance states of nickel are +2 and +3. 相似文献
89.
对收入再分配模型的现状和问题进行了分析,结合对机会成本理论的深度挖掘,创新性地建立了基于资本机会成本的收入再分配系数测算模型(单位业务能力匹配网络资源投资比例分摊法)。 相似文献
90.