全文获取类型
收费全文 | 18590篇 |
免费 | 1954篇 |
国内免费 | 1109篇 |
专业分类
电工技术 | 477篇 |
综合类 | 1250篇 |
化学工业 | 4775篇 |
金属工艺 | 1838篇 |
机械仪表 | 1008篇 |
建筑科学 | 1273篇 |
矿业工程 | 912篇 |
能源动力 | 556篇 |
轻工业 | 1616篇 |
水利工程 | 413篇 |
石油天然气 | 617篇 |
武器工业 | 184篇 |
无线电 | 876篇 |
一般工业技术 | 3093篇 |
冶金工业 | 1466篇 |
原子能技术 | 229篇 |
自动化技术 | 1070篇 |
出版年
2024年 | 59篇 |
2023年 | 289篇 |
2022年 | 533篇 |
2021年 | 628篇 |
2020年 | 679篇 |
2019年 | 640篇 |
2018年 | 581篇 |
2017年 | 758篇 |
2016年 | 740篇 |
2015年 | 710篇 |
2014年 | 1016篇 |
2013年 | 1311篇 |
2012年 | 1198篇 |
2011年 | 1330篇 |
2010年 | 928篇 |
2009年 | 1061篇 |
2008年 | 938篇 |
2007年 | 1085篇 |
2006年 | 1067篇 |
2005年 | 917篇 |
2004年 | 744篇 |
2003年 | 699篇 |
2002年 | 597篇 |
2001年 | 485篇 |
2000年 | 409篇 |
1999年 | 420篇 |
1998年 | 297篇 |
1997年 | 277篇 |
1996年 | 181篇 |
1995年 | 164篇 |
1994年 | 155篇 |
1993年 | 130篇 |
1992年 | 101篇 |
1991年 | 88篇 |
1990年 | 80篇 |
1989年 | 70篇 |
1988年 | 51篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1964年 | 7篇 |
1959年 | 8篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
111.
Dr. C. R. Nagarajah W. Thompson 《The International Journal of Advanced Manufacturing Technology》1994,9(5):333-342
There are two aspects to cell formation in flexible manufacturing systems, cell sizing or deciding on the optimum number of machines to be allocated to each cell, and then allocation of specific machines to each cell. Although the latter problem has been investigated extensively there is a paucity of published work on the former. This paper discusses the effects of cell sizing on operational flexibility.Operational flexibility is that aspect of flexibility that enables manufacturing systems to respond with speed and efficiency to changes in the manufacturing environment while maintaining an effective level of control. 相似文献
112.
G. Mestres F. Niefloud R. Fortune J. M. Devoisselle R. Marti H. Maillols 《Drug development and industrial pharmacy》1996,22(12):1193-1199
This paper reports a study undertaken using techniques of static and dynamic light scattering to investigate the influence of sodium salicylate and methyl salicylate on droplet size of oil-in-water emulsions. The rates of changes were measured by determining the size and distribution of the oil droplet in the material. All emulsions showed a bimodal size distribution; the mean diameters and polydispersity were calculated from intensity. These data were analyzed with nonlinear regressions and bootstrap methodology. An amount of methyl salicylate component induced a decrease of mean diameter and standard deviation. On the contrary, sodium salicylate entailed the growth of all droplet populations and coalescence for the highest concentration. 相似文献
113.
CH_4、CO_2与O_2制合成气的研究 Ⅱ工艺条件的影响 总被引:1,自引:0,他引:1
在固定床反应器中考察了12%Ni-5%RE-2%Cu-2%Li/Al2O3(mass)催化剂在CH4、CO2与O2催化氧化重整制合成气反应中催化剂粒径、工艺操作条件(空速与温度)及原料气配比对反应的影响,确定了较佳的操作条件:催化剂粒径20~40目,反应最佳温度为800℃,SV=4×104ml/(g·h)。同时看到在不同的原料气配比的条件下该催化剂的活性亦很稳定,不仅达到了反应平衡,且产物V(CO)/V(H2)比有很强的调变性。 相似文献
114.
本文利用相变扩张理论分析了粒界缓冲型展宽效应对BaTiO_3系PTC陶瓷的介电系数及温度系数a_r的影响,指出了晶粒尺寸和温度系数的关系。 相似文献
115.
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
116.
云母粒径对云母/聚丙烯性能的影响 总被引:2,自引:0,他引:2
朱静安 《现代塑料加工应用》1994,6(6):19-22
研究了云母填充改性聚丙烯(云母/PP)中云母粒径对其性能的影响。实验结果表明:云母粒径越小使得云母/聚丙烯材料强度提高越大、断裂伸长率增加,加工流动性变好;同时也促进和有利于聚丙烯结晶过程中的成核作用。 相似文献
117.
118.
研制了稀土六硼化物单晶LaB_6、CeB_6、PrB_6和NdB_6电子探针分析标样。根据X-射线峰位表和实测的特征X-射线谱,考察分析了La、Ce、Pr和Nd元素谱线之间的干扰情况,发现分析谱线PrLα_1受到L_αLβ_1线严重的干扰。以混合稀土金属为试样,采用扣除谱线重叠强度的背底非对称测量等方法对L_n、Ce、Pr和Nd进行了电子探针定量分析,其结果与荧光X-射线光谱分析结果符合较好。 相似文献
119.
介绍了铁合金冶炼时需要准备的原料,对不合格原料需要进行加工处理,达到合格粒度。并提出了影响铁合金冶炼过程有原料的粒度,配料称量,混合等重要因素。 相似文献
120.
W. L. Pearn M. H. Shu B. M. Hsu 《The International Journal of Advanced Manufacturing Technology》2004,24(1-2):140-147
The multiprocess performance analysis chart (MPPAC) based on the process capability index
Cpm, called Cpm MPPAC, is developed for analysing the manufacturing quality of a group of processes in a multiple process environment. The Cpm MPPAC conveys critical information of multiple processes regarding the departure of the process and process variability from one single chart. Existing research works on MPPAC are restricted to obtaining quality information from one single sample of each process ignoring sampling errors. The information provided from existing MPPAC charts, therefore, is unreliable and misleading and results in incorrect decisions. In this paper, we consider the natural estimator of Cpm based on multiple samples. Based on the natural estimator of Cpm, we consider the sampling errors by providing an explicit formula with the Matlab program to obtain the estimation accuracy of the Cpm. We tabulate the sampling accuracy of Cpm for sample size determination so that the engineers/practitioners can use it for their in-plant applications. An example of multiple precision voltage reference (PVR) processes is presented to illustrate the applicability of
Cpm MPPAC for manufacturing quality control. 相似文献