全文获取类型
收费全文 | 234330篇 |
免费 | 26418篇 |
国内免费 | 20710篇 |
专业分类
电工技术 | 15145篇 |
技术理论 | 10篇 |
综合类 | 23429篇 |
化学工业 | 44754篇 |
金属工艺 | 13654篇 |
机械仪表 | 12240篇 |
建筑科学 | 14814篇 |
矿业工程 | 6051篇 |
能源动力 | 10356篇 |
轻工业 | 11321篇 |
水利工程 | 9160篇 |
石油天然气 | 11419篇 |
武器工业 | 2582篇 |
无线电 | 20618篇 |
一般工业技术 | 26860篇 |
冶金工业 | 9187篇 |
原子能技术 | 2721篇 |
自动化技术 | 47137篇 |
出版年
2024年 | 1074篇 |
2023年 | 3966篇 |
2022年 | 7599篇 |
2021年 | 8634篇 |
2020年 | 7987篇 |
2019年 | 7183篇 |
2018年 | 6725篇 |
2017年 | 8215篇 |
2016年 | 9294篇 |
2015年 | 9469篇 |
2014年 | 12902篇 |
2013年 | 14277篇 |
2012年 | 16113篇 |
2011年 | 18671篇 |
2010年 | 14603篇 |
2009年 | 15898篇 |
2008年 | 14908篇 |
2007年 | 16977篇 |
2006年 | 14991篇 |
2005年 | 12541篇 |
2004年 | 10303篇 |
2003年 | 8904篇 |
2002年 | 7079篇 |
2001年 | 5733篇 |
2000年 | 5050篇 |
1999年 | 3908篇 |
1998年 | 3245篇 |
1997年 | 2592篇 |
1996年 | 2448篇 |
1995年 | 2107篇 |
1994年 | 1815篇 |
1993年 | 1325篇 |
1992年 | 1063篇 |
1991年 | 844篇 |
1990年 | 700篇 |
1989年 | 562篇 |
1988年 | 350篇 |
1987年 | 233篇 |
1986年 | 197篇 |
1985年 | 172篇 |
1984年 | 161篇 |
1983年 | 80篇 |
1982年 | 118篇 |
1981年 | 84篇 |
1980年 | 87篇 |
1979年 | 76篇 |
1978年 | 29篇 |
1977年 | 22篇 |
1959年 | 21篇 |
1951年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
A Cd analogue of the Tl and Hgn =3 series with nominal composition CdBa2Ca2Cu3Oy has been synthesized. The samples were superconducting according to magnetic susceptibility measurements. The critical temperature was 103 or 107 K depending on the preparation conditions. The EDX analysis revealed the presence of Cd-1111, Cd-1121, and Cd-2333 as minor phases. The observed diamagnetic effects were attributed to the differentT
c of these phases. 相似文献
72.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
73.
Giampiero Sacchetti Paola Pittia Manuela Biserni Gian G. Pinnavaia & Marco D. Rosa 《International Journal of Food Science & Technology》2003,38(2):135-143
Summary Ready‐to‐eat breakfast cereals immersed in milk undergo undesirable changes in texture because of sudden moisture uptake. The textural changes are ascribable to a plasticizing effect of water, which modifies the mechanical strength of products by softening the starch/protein matrix. In this work, some textural parameters of different cereal flakes were derived from the force–displacement curves monitored during 300 s of immersion in milk. Hardness loss, deformability increment and changes in the force–displacement curve profile were calculated and plotted against soaking time. The application of a sugar coating process to a model cereal flake increased the initial product hardness and improved the preservation of the textural parameters during immersion. The Peleg model closely fitted the experimental data, with regression coefficients from 0.967 to 0.999. 相似文献
74.
Al2O3对唐钢高炉炉渣性能的影响 总被引:14,自引:1,他引:13
针对唐钢近2年提高进口矿配比后,Al2O3含量升高对炉渣流动性带来的不利影响,对唐钢高炉的炉渣性能进行了试验研究。并结合国内同行业的生产实践经验,从理论上分析了炉渣中Al2O3及MgO的适宜含量范围,着重论述了唐钢所处冀东矿区条件下降低Al2O3的主要途径及适应高Al2O3炉渣的具体措施。 相似文献
75.
Hong Kong is known as a migrant city because its population was sourced from mainland China, and because there has always been outflows of people to overseas countries, especially from the mid-1980s to mid-1990s. Emigration to mainland China has become a significant recent trend. This article discusses this phenomenon in the theoretical contexts of migration and trans-border residential development. It contends that the trend will intensify more quickly than other cross-border movements because the two systems are separated by a political border within one country, and because there are common cultural ties and rapid economic integration. 相似文献
76.
A statistical study of the particle shape and size of pure V2O5 and TiO2, and samples of coprecipitated V2O5---TiO2 catalysts with different V/Ti ratios, has been performed. They were also characterized by XRD, EDAX, SEM and XPS. The results showed that pure vanadium pentoxide is compose by large square or needle-shaped particles, while pure titanium dioxide has small and rounded ones. VTiO samples presented an area and shape, depending on the V/Ti ratio.
These results and the spectroscopical characterization conducted to a particle model of the catalysts. Those VOTi samples with high V/Ti ratio would have large V2O5 crystals acting as support of a V/TiO2 solid solution. In contrast, those samples with a low V/Ti ratio, would have the solid solution supporting vanadium pentoxide crystals. 相似文献
77.
78.
J. R. Prez-Correa F. R. Sepúlveda M. A. Duarte 《International Journal of Adaptive Control and Signal Processing》1995,9(2):183-197
This paper presents experimental results obtained in temperature adaptive control of a heating vessel. A non-linear model of the process showed that the feed flow rate causes severe variations in time constant and process gain. An extended horizon self-tuning controller and two different model reference adaptive controllers were tested. The influence of design parameters on control performance for each algorithm was assessed. The control system was disturbed with load and setpoint changes. 相似文献
79.
研究了Al2O3-TiB2陶瓷刀具材料在1000℃下的氧化行为,用XRD、SEM分析了氧化后的相组成及显微结构。结果表明:Al2O3-TiB2陶瓷材料在1000℃空气中氧化增重符合抛物线规律;随TiB2含量的增加,该材料的抗氧化能力下降。 相似文献
80.
许进 《西安电子科技大学学报(自然科学版)》1994,(3)
文中解决了2-重自补图的计数问题,获得了具有p个顶点的2-重自补图的数目是其中Z(A)表示置换群A的圈指标,S ̄(2)_p表示p次对称群的对群. 相似文献