全文获取类型
收费全文 | 5479篇 |
免费 | 572篇 |
国内免费 | 284篇 |
专业分类
电工技术 | 343篇 |
技术理论 | 1篇 |
综合类 | 272篇 |
化学工业 | 1007篇 |
金属工艺 | 279篇 |
机械仪表 | 304篇 |
建筑科学 | 429篇 |
矿业工程 | 162篇 |
能源动力 | 169篇 |
轻工业 | 420篇 |
水利工程 | 97篇 |
石油天然气 | 314篇 |
武器工业 | 34篇 |
无线电 | 655篇 |
一般工业技术 | 653篇 |
冶金工业 | 294篇 |
原子能技术 | 63篇 |
自动化技术 | 839篇 |
出版年
2024年 | 32篇 |
2023年 | 97篇 |
2022年 | 247篇 |
2021年 | 317篇 |
2020年 | 213篇 |
2019年 | 175篇 |
2018年 | 221篇 |
2017年 | 205篇 |
2016年 | 174篇 |
2015年 | 264篇 |
2014年 | 256篇 |
2013年 | 354篇 |
2012年 | 340篇 |
2011年 | 412篇 |
2010年 | 296篇 |
2009年 | 311篇 |
2008年 | 264篇 |
2007年 | 263篇 |
2006年 | 231篇 |
2005年 | 222篇 |
2004年 | 153篇 |
2003年 | 122篇 |
2002年 | 111篇 |
2001年 | 107篇 |
2000年 | 145篇 |
1999年 | 153篇 |
1998年 | 122篇 |
1997年 | 99篇 |
1996年 | 103篇 |
1995年 | 75篇 |
1994年 | 46篇 |
1993年 | 46篇 |
1992年 | 34篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有6335条查询结果,搜索用时 234 毫秒
1.
Food Science and Biotechnology - Aluminum based reflective nanolens arrays were developed via a series of aluminum electropolishing and anodization steps with subsequent selective dissolution of... 相似文献
2.
Chaoxin Li Yi Zhou Yuming Tian Yuanyuan Zhao Kaiyue Wang Guomin Li Yuesheng Chai 《Ceramics International》2019,45(5):5613-5616
Ceramics with mullite whiskers were prepared from coal fly ash and Al2O3 raw materials, with AlF3 used as an additive. The phase structures and microstructures of the ceramics were identified via X-ray diffraction and scanning electron microscopy, respectively. The results show that pickling of coal fly ash is an effective method for enhancing the flexural strength of ceramics. Sintering temperature and AlF3 addition were also key factors influencing the creation of ideal ceramics. The ceramic made from pickled coal fly ash, 6?wt% AlF3, and sintered at 1200?°C, exhibited the highest flexural strength of 59.1?MPa, and had a bulk density of 1.32?g/cm3 and porosity of 26.8%. The results show that ceramic materials made under these conditions are ideal candidates for manufacturing ceramic proppants for the exploitation of unconventional oil and gas resources. 相似文献
3.
针对现有技术中输送系统控制不稳定、控制能力低下等问题,本文提出基于工业CAN总线的输送系统集成化控制.在控制系统CAN通信节点利用代码进行数据的转化,通过emit关键字将数据绘制成显示曲线,由输入的代码不断对系统数据进行刷新,实现了输送系统的实时监控,提高了系统运行的安全性.通过时间同步技术将SAEAS6802时钟同步协议与时钟修正算法相结合,有效地对数据处理时间和接收时间进行校正,减少了数据接收误差,提高了时间同步精度.实验结果表明,本文研究方法提高了输送控制系统的运行安全性和可靠性. 相似文献
4.
5.
Junlan Chai 《中国耐火材料》2018,(1)
正Four issues per volume a year,CHINA’S REFRACTORIES is distributed worldwide by airspeed delivery at no extra cost to subscribers. 相似文献
6.
Shuncheng Liu Kejian Wang Zhongfeng Zhang Yueqing Ren Lanlan Chen Xiaojie Sun Wenbin Liang 《Polymer Engineering and Science》2020,60(10):2640-2652
Three kinds of ethylene-octene copolymers (POE) were melt-blended with high-density polyethylene (PE-HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE-HD. The higher molecular weight POE can improve the toughness of PE-HD. 60:40 PE-HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m2 at −30°C, which is 21-fold of PE-HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield-plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann-type models were successfully extended to describe the typical S-shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c ) and temperature (T ) for high toughness. The curves are converted into 3D graph of T -c -impact strength for illustrating their coupling-separate effects, and further into the contour map of impact strength in T -c space for finding their partial equivalence. 相似文献
7.
对己二腈工业反应器提出了两釜串联带回流的模型,通过模拟计算得出模型的级间返混系数 f=6的结论。该模型能较好地预测工业反应器中物料组分浓度变化和气、液两相的流动特性;指出了现工业反应器的鼓泡中和段体积偏小是造成己二酸浓度偏高的关键;提出了可以通过增加串连一个鼓泡预反应段的改造方案,能有效地降低己二酸的浓度,从7%降至4%左右,从而能较好地减缓腐蚀和结焦。 相似文献
8.
本文用大视场光学显微镜、电子探针观察和分析了掺钛蓝宝石激光晶体中夹杂物的形状、尺寸大小及元素组成,并提出消除和减少这些夹杂物的方法. 相似文献
9.
介绍了按日本标准设计的横板式和国内竖板式军用滑木箱的结构设计参数,从木箱抗弯、抗静压及顶盖抗弯三方面对比了两种木箱的力学性能,分析了两种木箱的特点及适用范围。 相似文献
10.
Cheng Chen Zheng Guo Li Yeng Chai Soh 《Networking, IEEE/ACM Transactions on》2007,15(3):697-708
In this paper, we shall generalize the concepts of fairness, TCP-friendliness and TCP-compatibility such that more source adaptation schemes can be designed to support diverse applications over the Internet. A simple but efficient framework, in the form of a monotonic response function (MRF), is proposed for the analysis and the design of memoryless window-based source adaptation protocols by using these concepts. We first derive a necessary and sufficient condition for step-wise convergence to the weighted fairness. It is then used to construct increase-decrease policies. The requirements of our increase-decrease policy are less conservative than those of the CYRF (Choose Your Response Function) that was proposed in . Our MRF is suitable for transmission control protocol (TCP) and user datagram protocol (UDP), and can be used to design TCP-friendly and multimedia-friendly source adaptation schemes. Meanwhile, our MRF can be applied to provide bandwidth differentiation service without any change to the router of the existing Internet. 相似文献