全文获取类型
收费全文 | 22628篇 |
免费 | 4946篇 |
国内免费 | 3664篇 |
专业分类
电工技术 | 1238篇 |
综合类 | 2716篇 |
化学工业 | 1914篇 |
金属工艺 | 1390篇 |
机械仪表 | 1793篇 |
建筑科学 | 1112篇 |
矿业工程 | 611篇 |
能源动力 | 373篇 |
轻工业 | 788篇 |
水利工程 | 993篇 |
石油天然气 | 1112篇 |
武器工业 | 224篇 |
无线电 | 2726篇 |
一般工业技术 | 1807篇 |
冶金工业 | 1452篇 |
原子能技术 | 131篇 |
自动化技术 | 10858篇 |
出版年
2024年 | 333篇 |
2023年 | 705篇 |
2022年 | 1391篇 |
2021年 | 1318篇 |
2020年 | 1390篇 |
2019年 | 1133篇 |
2018年 | 978篇 |
2017年 | 1064篇 |
2016年 | 1148篇 |
2015年 | 1156篇 |
2014年 | 1552篇 |
2013年 | 1508篇 |
2012年 | 1989篇 |
2011年 | 1948篇 |
2010年 | 1548篇 |
2009年 | 1451篇 |
2008年 | 1397篇 |
2007年 | 1571篇 |
2006年 | 1360篇 |
2005年 | 1174篇 |
2004年 | 947篇 |
2003年 | 789篇 |
2002年 | 673篇 |
2001年 | 525篇 |
2000年 | 482篇 |
1999年 | 370篇 |
1998年 | 270篇 |
1997年 | 224篇 |
1996年 | 183篇 |
1995年 | 139篇 |
1994年 | 109篇 |
1993年 | 85篇 |
1992年 | 70篇 |
1991年 | 47篇 |
1990年 | 49篇 |
1989年 | 37篇 |
1988年 | 21篇 |
1987年 | 11篇 |
1986年 | 21篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
焦化废水除氟技术及其应用 总被引:1,自引:0,他引:1
阐述了焦化废水中氟离子的降解机理,分析了化学沉淀法和混凝沉降法等除氟工艺及其处理效果,并对宝钢焦化废水的除氟工艺的进行了评价。 相似文献
93.
94.
Behavioral cues to deception are instrumental in detecting deception. As one of the primary sources of deception behavior, text has been analyzed at the level of sub-sentence or message but not the discourse of interaction. Additionally, empirical studies on cues to deception in the case of multiple receivers remain nonexistent. To fill these voids, we propose a discourse framework and six hypotheses about deception behaviors in a multi-receiver environment. The deception behaviors are operationalized by discourse features based on an analysis of real-world data. The results of statistical analysis validate the efficacy of discourse features in discriminating deceivers from truth-tellers. 相似文献
95.
A new method is presented for preparing highly monodispersed silica particles using a two-stage semibatch/batch hydrolysis reaction of Si(OC2 H5 )4 . The slower rate of hydrolysis of the tetraethylorthosilicate (TEOS) that occurred during the semibatch process resulted in larger silica particles with a higher yield and narrower size distribution. This was in direct contrast to the batch process. In addition, the ability of four different mixed processes to produce silica particles with good packing density, narrower particle-size distribution, and higher yield were evaluated. These were batch/batch (B-B), batch/semibatch (B-S), semibatch/batch (S-B), and semibatch/semibatch (S-S) processes. The S-S system produced the largest particles with the highest yields. The size of the silica particles obtained by the S-B method decreased with increasing reaction time, while the particles obtained by the B-S process had the best particle-size distribution and packing density. In conclusion, a mixed batch/semibatch system was the best way to produce an extremely narrow particle-size distribution and a good packing density. 相似文献
96.
97.
简单介绍了双组分环氧胶粘剂的特点、组成及固化反应机理 ,并且详细叙述了我厂双组分环氧胶粘剂的组分、配制工艺和灌胶工艺以及讨论了双组分环氧胶粘剂在我厂的应用情况 ,为我厂的军品及民用电器产品的灌封胶接提供了广泛的前景 相似文献
98.
丁文荣 《南水北调与水利科技(中英文)》2017,15(1):107-112
基于MODIS NDVI数据及标准气象站数据、退耕还林资料,辅以空间统计、叠置分析和趋势分析等方法,研究了金沙江下段植被NDVI时空变化特征及其影响因素,结果表明:从年内来看,金沙江下段植被NDVI变化呈单峰型,3月份为最低值0.55,而9月份为最高值0.75,年际上10年以来植被覆盖总体呈现出增长趋势,且这种增长存在显著的空间异质性;研究区植被覆盖较好,植被NDVI平均值为0.65,海拔3 850m以下植被覆盖随海拔上升而增加,超过3 850m后随海拔升高呈降低趋势;年内植被NDVI受降水量的影响较气温更为明显,对两者均有2个月的滞后期,而年际上植被NDVI则受气温变化的影响较降水量更为突出,且大规模的植被恢复工程对金沙江下段植被覆盖的增加有重要贡献。 相似文献
99.
The nano-CeO2/ZnO catalysts were prepared using a novel combination of homogeneous precipitation with micro-emulsion for oxidative coupling of methane with CO2 as an oxidant. The prepared catalysts were compared with those prepared using the conventional impregnation. The catalysts prepared in two ways were characterized with FTIR, TEM, XRD and CO2-TPD. The effects of the reaction temperature, the amount of ZnO doped in the catalysts and the average size were investigated. The experimental investigation demonstrated that methane conversion over the nano-CeO2/ZnO catalysts prepared by the combined technique was higher than that obtained over catalysts prepared by the conventional impregnation. A better low-temperature activity has also been achieved over the nanocatalysts. There was no clear trend between the average size of nano-CeO2/ZnO catalysts and their catalytic performance but methane conversion increased with increasing fractal dimension of nanocatalysts. 相似文献
100.
The improvement of safety and dependability in systems that physically interact with humans requires investigation with respect to the possible states of the user’s motion and an attempt to recognize these states. In this study, we propose a method for real-time visual state classification of a user with a walking support system. The visual features are extracted using principal component analysis and classification is performed by hidden Markov models, both for real-time fall detection (one-class classification) and real-time state recognition (multi-class classification). The algorithms are used in experiments with a passive-type walker robot called “RT Walker” equipped with servo brakes and a depth sensor (Microsoft Kinect). The experiments are performed with 10 subjects, including an experienced physiotherapist who can imitate the walking pattern of the elderly and people with disabilities. The results of the state classification can be used to improve fall-prevention control algorithms for walking support systems. The proposed method can also be used for other vision-based classification applications, which require real-time abnormality detection or state recognition. 相似文献