全文获取类型
收费全文 | 23396篇 |
免费 | 2286篇 |
国内免费 | 847篇 |
专业分类
电工技术 | 731篇 |
综合类 | 1390篇 |
化学工业 | 6188篇 |
金属工艺 | 2052篇 |
机械仪表 | 954篇 |
建筑科学 | 715篇 |
矿业工程 | 636篇 |
能源动力 | 1164篇 |
轻工业 | 2911篇 |
水利工程 | 136篇 |
石油天然气 | 1366篇 |
武器工业 | 617篇 |
无线电 | 1131篇 |
一般工业技术 | 2889篇 |
冶金工业 | 2522篇 |
原子能技术 | 235篇 |
自动化技术 | 892篇 |
出版年
2025年 | 176篇 |
2024年 | 591篇 |
2023年 | 574篇 |
2022年 | 670篇 |
2021年 | 841篇 |
2020年 | 916篇 |
2019年 | 853篇 |
2018年 | 725篇 |
2017年 | 920篇 |
2016年 | 924篇 |
2015年 | 781篇 |
2014年 | 1189篇 |
2013年 | 1266篇 |
2012年 | 1397篇 |
2011年 | 1489篇 |
2010年 | 1159篇 |
2009年 | 1137篇 |
2008年 | 939篇 |
2007年 | 1268篇 |
2006年 | 1318篇 |
2005年 | 1161篇 |
2004年 | 1067篇 |
2003年 | 887篇 |
2002年 | 816篇 |
2001年 | 671篇 |
2000年 | 577篇 |
1999年 | 429篇 |
1998年 | 308篇 |
1997年 | 281篇 |
1996年 | 213篇 |
1995年 | 181篇 |
1994年 | 177篇 |
1993年 | 120篇 |
1992年 | 125篇 |
1991年 | 87篇 |
1990年 | 75篇 |
1989年 | 43篇 |
1988年 | 38篇 |
1987年 | 29篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
P. S. Lawson 《Biomass & bioenergy》1992,2(1-6):319-330
In recent years it has been recognised by an increasing number of nations that there is considerable energy potential within MSW. As a result many countries have established R,D& D programmes to examine methods of exploiting this potential. The IEA's MSW Conversion Activity was set up in 1986 to provide an infrastructure for sharing information and co-ordinating work in this area internationally. This Activity was extended in 1989 and currently a total of 9 nations participate in it.
To cope with the wide scope of the area (encompassing both biological and thermal processing of MSW) the Activity was divided into three subgroups or Expert Working Groups (EWGs). Each of these dealt with a distinct area of expertise:
- 1. •Downstream effects of source separation and screening of MSW
- 2. •Sampling and analytical protocols
- 3. •Landfill gas
In addition to these groups a central secretariat based at Harwell (UK) has provided guidance, established and administered databases of contacts and produced a series of national reports.
This paper describes the achievements of the Activity and discusses work proposed for the future. 相似文献
2.
Hong Jin Mohammad S. Uddin Yu L. Huang Wah K. Teo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(1):67-72
High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography. 相似文献
3.
Savitree Jungsakulrujirek & Athapol Noomhorm 《International Journal of Food Science & Technology》1998,33(4):367-374
The effect of fruit size and harvesting of Thai tangerine fruit ( Citrus reticulata , Blanco) at different growth stages, 8–12 months after fruit set, on the distribution of limonin in whole fruit as well as in the individual fruit parts and extracted juice was investigated. The highest limonin concentration was observed in seed, followed by albedo, flavedo, segment membrane and juice sacs in decreasing order. The limonin concentration in juice as well as in whole fruit was decreased when fruit was harvested 8–12 months of fruit set. Increasing harvesting time from 8 to 12 months showed corresponding decreases in the amount of limonin in flavedo, albedo and seed. There was a decrease in titrable acidity and increase in total soluble solid and total soluble solid/titrable acidity ratio of juice with a later than normal harvesting time. However, fruit size showed no effect on limonin content and other properties of juice extracted from tangerine. 相似文献
4.
5.
A. N. Zolotko Ya. I. Vovchuk V. G. Shevchuk N. I. Poletaev 《Combustion, Explosion, and Shock Waves》2005,41(6):611-621
The ignition and combustion of dust-gas suspensions are considered. It is shown that the ability of these systems to accumulate
heat is determined not only by their kinetic and thermal properties but also by the relation between their reaction surface
and the heat-removal surface (f). Experimental information on flame temperatures, ignition delays, and flame propagation over gas suspensions is processed
using the parameter f, and the postulate on the stimulating role of the developed reaction surface in activating these processes is validated.
It is shown that during overall burning, diffusion combustion of particles occurs only for rather small values of f. The ambiguous effect of the parameter f on the ignition and combustion processes leads to the necessity of optimizing the fuel size distribution and concentration
for the effective operation of the power devices. The role of the macroparameters of two-phase flames of refractory metals
in the synthesis of combustion nanoproducts is analyzed.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 3–14, November–December, 2005. 相似文献
6.
The preparation of pseudoionones by aldol condensation reaction between citral and acetone have been carried out in the presence of acid (HY and beta zeolites), an acid–base (amorphous aluminophosphate) and basic catalysts such as an aluminophosphate oxynitride, MgO and different activated hydrotalcites. The results showed that acid or acid–base catalysts were not successful for performing in one pot the preparation of ionones. MgO and calcined hydrotalcites showed excellent activity and selectivity to pseudoionones, with calcined hydrotalcite more selective than MgO. Moreover, the rate of reaction can be improved by activating the hydrotalcite through rehydration. This activation can be successfully done by simply adding the optimum amount of water to the calcined hydrotalcite before reaction. The inhibiting effect of the concentration citral on the catalytic activity of rehydrated hydrotalcites that has been reported to occur at 273 K can be avoided by working at a reaction temperature of 333 K. 相似文献
7.
介绍了ZAG100-1000/35型全自动压滤机的研制与应用情况.表明机组主机结构、生产能力、自控水平均比引进产品有所提高,整机性能良好。 相似文献
8.
《Advanced Powder Technology》2023,34(1):103880
The momentum exchange between the phases plays a vital role in modelling of gas–solid flows and it is mathematically described by drag models. However, no consensus exists on which drag model gives the most accurate prediction of the drag force, and, despite the increase in available computing power, the same drag models are used in two-dimensional and three-dimensional simulations. In this study, direct numerical simulations of gas flow through multiple random configurations of static monodisperse particles are performed. The variations of solid volume fraction and particle Reynolds number are in the ranges of 0.05–0.4 and 13.7–136.9, respectively. The drag force exerted on particles is calculated and properly averaged. Based on the simulation results, thirteen drag models are compared and correction factors are introduced using the stochastic gradient descent algorithm. The correction factors provide a simple adjustment for the models to be used in 2D modelling. 相似文献
9.
10.
基于边界表示的曲面实体造型系统的数据结构 总被引:2,自引:0,他引:2
实体造型是CAD系统的核心模块,而二次曲面在工程中常用来描述轴,孔及圆角等形状特征。讨论了在微机上实现的一个基于边界表示的实体模型的数据结构,并针对二次曲面的特点,实现了对自封闭曲面的无二义性拓扩定义,为顺利进行曲面的拼合运算打下了基础。 相似文献