全文获取类型
收费全文 | 40657篇 |
免费 | 1001篇 |
国内免费 | 5651篇 |
专业分类
电工技术 | 3119篇 |
综合类 | 5574篇 |
化学工业 | 3406篇 |
金属工艺 | 5853篇 |
机械仪表 | 2353篇 |
建筑科学 | 2115篇 |
矿业工程 | 1116篇 |
能源动力 | 722篇 |
轻工业 | 3459篇 |
水利工程 | 1031篇 |
石油天然气 | 4476篇 |
武器工业 | 335篇 |
无线电 | 3988篇 |
一般工业技术 | 2606篇 |
冶金工业 | 1262篇 |
原子能技术 | 1529篇 |
自动化技术 | 4365篇 |
出版年
2022年 | 22篇 |
2021年 | 32篇 |
2020年 | 49篇 |
2018年 | 21篇 |
2017年 | 86篇 |
2016年 | 45篇 |
2015年 | 75篇 |
2014年 | 917篇 |
2013年 | 624篇 |
2012年 | 1052篇 |
2011年 | 5479篇 |
2010年 | 2544篇 |
2009年 | 1513篇 |
2008年 | 1436篇 |
2007年 | 1066篇 |
2006年 | 1302篇 |
2005年 | 1502篇 |
2004年 | 5461篇 |
2003年 | 3098篇 |
2002年 | 2983篇 |
2001年 | 1902篇 |
2000年 | 1179篇 |
1999年 | 2009篇 |
1998年 | 1338篇 |
1997年 | 1397篇 |
1996年 | 708篇 |
1995年 | 581篇 |
1994年 | 481篇 |
1993年 | 2046篇 |
1992年 | 1589篇 |
1991年 | 1101篇 |
1990年 | 1044篇 |
1989年 | 802篇 |
1988年 | 507篇 |
1987年 | 292篇 |
1986年 | 211篇 |
1985年 | 118篇 |
1984年 | 85篇 |
1983年 | 56篇 |
1982年 | 42篇 |
1981年 | 34篇 |
1980年 | 75篇 |
1979年 | 61篇 |
1977年 | 18篇 |
1965年 | 61篇 |
1963年 | 25篇 |
1959年 | 26篇 |
1958年 | 28篇 |
1957年 | 33篇 |
1956年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
正Seo是为了什么?为了大把的流量,为了足够的成交,为了大把的获利。如,要是现在我们的中心词排名并不靠前,但是流量可大把大把的抓,或者流量并不多,但是成交不错,那么比那些排名好没流量,流量多但没成交的网站又如何呢?其实刚做seo的时候大家都知道这个问题,但做着做着就迷失到排名里面了,做个好的计划,搞好方向非常重要,最起码不迷失。那么具体我们如何不要计较那些排名利用seo来 相似文献
62.
运动发酵单胞(Zymomonas mobilis)ATCC29191菌株在含1~3g/L甘氨酸的液体培育12小时的菌体,用含20g/L的溶菌酶溶液处理12小时,可以稳定得到80%~90%的原生质球。原生质球稀释后在底层再生培养基上涂布,上面复盖一层半固体培养基,30℃培养5~7小时,再生率可达10~(-2)水平。 相似文献
63.
64.
GAO Lin LI Sheng JIN HongGuang & LIN Hu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Graduate School of Chinese Academy of Sciences Beijing 《中国科学:信息科学(英文版)》2010,(1)
On basis of adopting polygeneration systems for power and alternative fuels,capturing CO2 with near zero energy penalties,and storing CO2 on sites,a new kind of Energy Network can integrate energy utilization,CO2 capture,transportation and storage synthetically.Techno-economic analysis of this solution focusing on Inner Mongolia and the Yangtze River Delta districts had been carried with comparison to the chain method for energy utilization and CO2 sequestration.This solution can save 21.5% of energy,and re... 相似文献
65.
JIANG YuXuan LI Zheng SUN YongJian YU TongJun CHEN ZhiZhong ZHANG GuoYi ZHANG GuangChen & FENG ShiWei State Key Laboratory of Artificial Microstructure Mesoscopic Physics School of Physics Peking University Beijing China School of Electronic Information & Control Engineering Beijing University of Technology Beijing 《中国科学:信息科学(英文版)》2010,(2)
We presented the analysis of the incomplete conduction in bonding medium in high power GaN-based light-emitting diode (LED) packages. A numerical study was carried out with parametric model to understand the junction temperature variation due to bonding medium defects. Transient thermal measurement was performed to evaluate LED’s junction temperature. Thermal resistance from chip to lead frame was 20 K/W in our sample LED. It was suggested that only 60% of the surface area of the bonding medium was involved... 相似文献
66.
ZHENG Nan YANG Ping WANG QiYi YANG ZhongHai & HUANG Nan Key Laboratory of Advanced Technology for Materials of Education Ministry Key Laboratory of Artificial Organ Surface Engineering of Sichuan School of Materials Science Engineering Southwest Jiaotong University Chengdu China 《中国科学:信息科学(英文版)》2010,(1)
Microgrooves were prepared on Si(100) surface by photolithography and wet etching.Subsequently,Si-N-O films were deposited on the microgrooves by unbalanced magnetron sputtering(UBMS) and micro-patterned surfaces of Si-N-O films were obtained.The size of the micropatterns was measured by surface profilometer.The chemical composition of Si-N-O films were characterized by X-ray photoelectron spectrometry(XPS) and the wettability of the micropatterned surfaces was evaluated by contact angle measurement.The beh... 相似文献
67.
NISHI Michihiro 《中国科学:信息科学(英文版)》2010,(1)
A novel double suction shaft-less mini pump was developed for heat control of small energy systems in this study.The mini pump impeller with an exit diameter of 40 mm was combined with the motor rotor supported by the hybrid dynamic bearing.The specific speed of the pump was 125 min-1 m3 min-1 m.The hydraulic performance of the pump was investigated experimen-tally under four rotational speeds.From the test results,it was recognized that the pump could provide a flow discharge of 5 L/min and head of 1.5 m,w... 相似文献
68.
Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hol... 相似文献
69.
ZHOU HaiQiang JU Ping YANG Hui & SUN Ran Electrical Engineering School HoHai University Nanjing China Henan Power Dispatching & Communication Center Zhengzhou 《中国科学:信息科学(英文版)》2010,(4)
The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus... 相似文献
70.
Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation ... 相似文献