全文获取类型
收费全文 | 5752篇 |
免费 | 609篇 |
国内免费 | 609篇 |
专业分类
电工技术 | 130篇 |
技术理论 | 1篇 |
综合类 | 226篇 |
化学工业 | 1117篇 |
金属工艺 | 205篇 |
机械仪表 | 53篇 |
建筑科学 | 270篇 |
矿业工程 | 35篇 |
能源动力 | 208篇 |
轻工业 | 93篇 |
水利工程 | 77篇 |
石油天然气 | 150篇 |
武器工业 | 11篇 |
无线电 | 982篇 |
一般工业技术 | 1195篇 |
冶金工业 | 73篇 |
原子能技术 | 47篇 |
自动化技术 | 2097篇 |
出版年
2024年 | 4篇 |
2023年 | 87篇 |
2022年 | 63篇 |
2021年 | 115篇 |
2020年 | 146篇 |
2019年 | 95篇 |
2018年 | 73篇 |
2017年 | 139篇 |
2016年 | 160篇 |
2015年 | 197篇 |
2014年 | 310篇 |
2013年 | 417篇 |
2012年 | 560篇 |
2011年 | 653篇 |
2010年 | 512篇 |
2009年 | 607篇 |
2008年 | 466篇 |
2007年 | 616篇 |
2006年 | 532篇 |
2005年 | 276篇 |
2004年 | 162篇 |
2003年 | 104篇 |
2002年 | 119篇 |
2001年 | 83篇 |
2000年 | 105篇 |
1999年 | 91篇 |
1998年 | 62篇 |
1997年 | 54篇 |
1996年 | 39篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有6970条查询结果,搜索用时 15 毫秒
41.
RS与FNN集成在焊接缺陷识别中应用 总被引:1,自引:0,他引:1
针对焊接图像缺陷识别中提取的特征受噪声干扰比较严重,以及现有的识别算法准确率低的问题,提出了一种粗糙集(RS)和模糊神经网络(FNN)集成的缺陷识别算法.首先使用模糊C-均值聚类算法对样本属性离散化,然后使用RS对离散化后的样本数据进行属性约简得到决策规则,并使用π函数根据聚类的中心和半径对属性进行模糊化,克服RS对噪声敏感问题;根据得到的精简模糊决策规则和模糊逻辑推理确定FNN的结构,使用依赖度和规则的条件覆盖度确定网络的初始参数,考虑到样本中数据的可信度问题,用加权代价函数调整模型参数.仿真实验表明,本算法解决了分类过程中样本数据受到噪声干扰引起的不确定性、FNN结构难以确定的问题,能有效地提高焊缝图像缺陷的识别能力. 相似文献
42.
PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics
were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 104 order, low dielectric loss (lower than 3.0% in the working frequency range of 1–1 000 kHz), saturation polarization intensity
10−1 C/m2 order, and pyroelectric coefficient 10−3 C/m2·K order. 相似文献
43.
将遗传算法与参数跟踪策略有效结合,跟踪过程中进行搜索域压缩与位移操作,形成了一种功能强大的新算法,可成功应用于电磁领域中各种各样复超越方程的高精度求解问题.在算法实现过程中,使用参数跟踪策略有效地缩小了搜索区域,保证了解的单一性,提高了运算速度;使用动态搜索域提高了解的精度;应用三阶差商公式预估新的搜索中心,使运算速度得以进一步提高.应用本文发展的算法详细求解了终端短路法测量材料的复介电常数时得到的复超越方程和部分填充矩形波导的特征方程,计算结果表明该算法能够轻松地解决复超越方程中的多值问题,解集完备性好,算法鲁棒性强. 相似文献
44.
HAN Zuo-zhen YANG Ren-chao FAN Ai-ping CHEN Qing-chun SHAO Yun-tang 《中国矿业大学学报(英文版)》2009,19(1):102-107
Oil reservoirs with secondary bottom water in Ng33 members (in Guantao formation, Paleogene system) of Lin2-6 fault block in Huimin depression (Bohai Bay Basin) have entered the late stage of ultra-high water-containing-exploitation. Oil exploita-tion from vertical wells is becoming more and more inefficient. The reservoir type, with water displacing oil and the remaining oil distribution are specifically studied in order to improve the efficiency of the recovery ratio. An integrated scheme for adjusting horizontal wells has been designed and the key technique of the scheme optimized. The study shows that: 1) the positive rhythm of fluvial depositional features is the internal cause of the flooding of oil reservoirs while water injection, injection-production patterns and accumulative petroleum production are the external causes; 2) oil-water driving patterns have transferred from edge water ad-vancing to bottom-water-coning; distribution of the remaining oil mainly concentrates in the upper rhythm and top of the middle rhythm in Ng33 members; 3) a great deal of remaining oil is enriched in high positions of faults, in axes of tiny structures, in stagna-tion areas among water-injection wells and oil-wells and in tectonic saddle areas with sparse wells. Compared with vertical wells, horizontal wells have advantages such as high recovery, high off-take potential, high critical output, large controlling areas and long time of bottom-water breakthrough. 相似文献
45.
针对农村生活污水直接排放已经成为影响我国农村水环境质量主要因素之一的现状,从适合我国农村的以村落或居民点为单位进行生活污水分散式处理的思维入手,介绍了我国现今主要的分散式生活污水处理技术的原理、特点、不足及其应用现状;继而综合比较了这些技术的技术经济指标,提出了适合我国农村的分散式生活污水处理技术的设计原则;最后提出发展有较高水力负荷,并具备小规模设备化特征和多种生物处理单元复合的创新技术是我国农村生活污水处理技术发展的主要方向。 相似文献
46.
47.
Theoretical expressions and mathematical analysis in cyclic reciprocal derivative chronopotentiometry (CRDCP) are presented for totally irreversible electrode processes corresponding to the application of symmetrical and unsymmetrical programmed currents. For two successive unsymmetrical programmed currents, the effect of the currents ratio b (b = |I2(t)/I1(t)|) on the (dt/dE)–E curves is discussed. The electrochemical behavior of totally irreversible electrode processes has been studied corresponding to the application of the unique unsymmetrical programmed Φm(I0) proposed recently. CRDCP characteristic parameters obtained for totally irreversible electrode processes are different from those of reversible electrode processes. Therefore, a comparison of CRDCP between both mechanisms is presented. Based on the mathematical derivation, alternative methods for kinetic measuring are described. It is prospected that CRDCP is convenient and applicable for studying the reversibility of the electrode processes in form of CRDCP characteristic parameters. 相似文献
48.
《Journal of the European Ceramic Society》2021,41(15):7783-7791
Two 3Gd-TZP materials were manufactured from powders produced by intense mixing and milling of unstabilized zirconia starting powders and gadolinia as stabilizer oxide by hot pressing at 1250 °C – 1400 °C. The materials show a combination of high toughness and moderate strength. In detail depending on starting powder the two TZP showed distinct differences concerning transformation characteristics, sintering temperature dependence of mechanical properties and the tendency to develop R-curve related deformation features such as non-linear stress strain curves and formation of transformation bands prior to fracture. 相似文献
49.
50.