全文获取类型
收费全文 | 39898篇 |
免费 | 3085篇 |
国内免费 | 1547篇 |
专业分类
电工技术 | 1996篇 |
技术理论 | 2篇 |
综合类 | 2392篇 |
化学工业 | 6845篇 |
金属工艺 | 2272篇 |
机械仪表 | 2359篇 |
建筑科学 | 3100篇 |
矿业工程 | 955篇 |
能源动力 | 943篇 |
轻工业 | 2663篇 |
水利工程 | 554篇 |
石油天然气 | 2698篇 |
武器工业 | 211篇 |
无线电 | 4757篇 |
一般工业技术 | 5057篇 |
冶金工业 | 2129篇 |
原子能技术 | 449篇 |
自动化技术 | 5148篇 |
出版年
2024年 | 178篇 |
2023年 | 725篇 |
2022年 | 1108篇 |
2021年 | 1617篇 |
2020年 | 1209篇 |
2019年 | 1001篇 |
2018年 | 1109篇 |
2017年 | 1301篇 |
2016年 | 1157篇 |
2015年 | 1474篇 |
2014年 | 1854篇 |
2013年 | 2383篇 |
2012年 | 2306篇 |
2011年 | 2605篇 |
2010年 | 2316篇 |
2009年 | 2149篇 |
2008年 | 2108篇 |
2007年 | 2069篇 |
2006年 | 2090篇 |
2005年 | 1804篇 |
2004年 | 1229篇 |
2003年 | 1056篇 |
2002年 | 1016篇 |
2001年 | 877篇 |
2000年 | 910篇 |
1999年 | 1098篇 |
1998年 | 955篇 |
1997年 | 836篇 |
1996年 | 826篇 |
1995年 | 636篇 |
1994年 | 553篇 |
1993年 | 386篇 |
1992年 | 342篇 |
1991年 | 258篇 |
1990年 | 198篇 |
1989年 | 170篇 |
1988年 | 139篇 |
1987年 | 107篇 |
1986年 | 78篇 |
1985年 | 59篇 |
1984年 | 58篇 |
1983年 | 30篇 |
1982年 | 37篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1973年 | 5篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
本文全面分析了DH80—16型离心压缩机可倾轴瓦油封漏油的原因,并介绍了可倾轴瓦油封漏油问题的解决及具体实施方案。 相似文献
82.
A method to design a microstrip filter has been proposed. The multiple capacitively loaded coupled lines are adopted for the design of the microstrip filter. The filter shows different stopband behaviour with respect to even or odd total number of resonators. The transmission zeros may be located around the lower, higher or both regions of the passband's skirt. The coupling among the capacitively loaded lines can produce another transmission zero particularly in the higher stopband. A bandpass filter and a duplexer utilising these features are designed. The equivalent model is also proposed to illustrate the filter's coupling among these capacitively loaded coupled lines. The design has been verified by experimental results 相似文献
83.
The molten iron allocation problem (MIAP) is to allocate molten iron from blast furnaces to steel-making furnaces. The allocation needs to observe the release times of the molten iron defined by the draining plan of the blast furnaces and the transport time between the iron-making and steel-making stages. Time window constraints for processing the molten iron must be satisfied to avoid freezing. The objective is to find a schedule with minimum total weighted completion time. This objective reflects the practical consideration of improving steel-making efficiency and reducing operation cost caused by the need for reheating. Such a problem can be viewed as a parallel machine scheduling problem with time windows which is known to be NP-hard. In this paper, we first formulate the molten iron allocation problem as an integer programming model and then reformulate it as a set partitioning model by applying the Dantzig–Wolfe decomposition. We solve the problem using a column generation-based branch-and-price algorithm. Since the subproblem of column generation is still NP-hard, we propose a state-space relaxation-based dynamic programming algorithm for the subproblem. Computational experiments demonstrate that the proposed algorithm is capable of solving problems with up to 100 jobs to optimality within a reasonable computation time. 相似文献
84.
Duringthelastdecade ,thedesignandsynthesisoftripodalligandsandtheirmetalcomplexeshaveattractedconsiderableattentionduetotheirpotentialusesaslumi nescentprobesinmedicineandbiochemistry[1~ 7] ,ascatalysts[8] andelectrochemicalmaterials[9] .However ,thecomplexesofrareearthmetalwithtripodalligandshavefewreported[10 ] .Asanextensionofourstudiesoncomplexesofmetalwithtripodalligands ,anewtripodalligand (tris { 2 [N (pyridine methanoyl)amino]ethyl}amine ,L)anditscomplexeswithrareearthnitratesweresyn… 相似文献
85.
A Ml (NiCoMnA1)5 hydrogen storage alloys was prepared by double-roller rapid quenching.Its microstructure, electrochemically and kinetic characteristic were studied.A uniform crystal phase with CaCu5 structure could be detected by XRD analyses, whose average grain size is 30 ~ 50 nm and the ratio of c/a of nano-crystal hydrogen storage alloy is larger.The hydrogen absorption/desertion p - C isotherms of alloy show that its fiat-performance is perfect and the magnetic stagnant effect is very little.An simulate cell is used for electrochemical measurement.Electrode is 10C, the capacity decreasing rate via the 450 cycles at 7C is less than 20%. 相似文献
86.
本文对2002年国际国内白银市场做了全面分析,对2003年白银市场走势进行了分析预测。白银作为一种贵金属,同时又具有工业金属的特性,世界经济形势,世界政治局势的变化,都对白银价格走势产生影响。鉴于该金属的双重特性,本文就从白银的供应、需求、消费及世界经济的发展等方面论述白银市场前进趋势。 相似文献
87.
Xianpeng Wang Lixin Tang 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):431-441
This paper investigates the hot rolling production scheduling problem in the steel industry and proposes a new mixed integer
programming model for this problem based on the monolithic modeling strategy that integrates batching and scheduling. Using
this strategy, the new model can simultaneously schedule multiple turns and simultaneously determine the production timetable
of these turns in a global optimal view. A long-term tabu search heuristic using frequency-based memory is developed to obtain
near-optimal solutions for this problem. Three kinds of speed-up strategies are developed to accelerate the search procedure
of the proposed tabu search. A practical scheduling system combining the proposed mathematical model and the tabu search heuristic
has been developed and tested on instances collected from practical production data. The experimental results show that the
proposed mathematical model and the tabu search heuristic outperform both the current manual scheduling method and the traditional
serial method. 相似文献
88.
乳化炸药的乳化物理模型和理想乳化模态 总被引:3,自引:1,他引:2
文章以平推流模拟了乳化炸药乳胶质的形成过程,并建立了机械强制乳化的物理模型及理想模态。 相似文献
89.
The purpose of this paper was to examine the characteristics of the victims and abusers of child abuse cases on the Child Protection Registry in Hong Kong as of March 1995 and to compare findings with a similar community report of child abuse in Hong Kong conducted approximately 15 years earlier. As of March 31, 1995, there were 457 active cases of child abuse or suspected child abuse (44% male and 56% female) on the computerized Child Protection Registry. Fifty percent of the victims were grade school age children between 7-12, and 62.4% suffered physical abuse. The abusers or suspected abusers were 52% male and 48% female with nearly half (49%) in their thirties. The majority of abusers were married/cohabiting (75%) with only a grade school education (60%). As compared to 1979, there was an increase of sexual child abuse cases, female victims of child abuse, and an increase in male abusers or suspected abusers. 相似文献
90.
汤炳谦 《固体电子学研究与进展》1996,16(1):48-55
叙述了Ba(Zn1/3Ta2/3)O3介质谐振器材料的制备、结构、微波性能及典型应用。Ba(Zn1/3Ta2/3)O3介质材料介电常数εr为29.5,频率温度系数τ≈0(-55~+85℃),10GHz下最大无载Q值14700,在28GHz测得Q值约为4800。这种材料具有高Q值,特别适用于X以上波段作为振荡器电路中频率稳定元件。用这种介质谐振器已研制出8mm介质稳频微带耿氏振荡器,频率稳定度小于10×10-6/℃,最大输出功率达180mW。 相似文献