全文获取类型
收费全文 | 11210篇 |
免费 | 1223篇 |
国内免费 | 606篇 |
专业分类
电工技术 | 446篇 |
技术理论 | 1篇 |
综合类 | 723篇 |
化学工业 | 1659篇 |
金属工艺 | 1326篇 |
机械仪表 | 1861篇 |
建筑科学 | 750篇 |
矿业工程 | 871篇 |
能源动力 | 534篇 |
轻工业 | 139篇 |
水利工程 | 139篇 |
石油天然气 | 125篇 |
武器工业 | 54篇 |
无线电 | 1101篇 |
一般工业技术 | 1266篇 |
冶金工业 | 495篇 |
原子能技术 | 34篇 |
自动化技术 | 1515篇 |
出版年
2024年 | 52篇 |
2023年 | 284篇 |
2022年 | 459篇 |
2021年 | 586篇 |
2020年 | 472篇 |
2019年 | 311篇 |
2018年 | 247篇 |
2017年 | 331篇 |
2016年 | 285篇 |
2015年 | 305篇 |
2014年 | 910篇 |
2013年 | 979篇 |
2012年 | 1880篇 |
2011年 | 1585篇 |
2010年 | 1032篇 |
2009年 | 898篇 |
2008年 | 372篇 |
2007年 | 698篇 |
2006年 | 512篇 |
2005年 | 154篇 |
2004年 | 68篇 |
2003年 | 68篇 |
2002年 | 73篇 |
2001年 | 51篇 |
2000年 | 50篇 |
1999年 | 41篇 |
1998年 | 25篇 |
1997年 | 14篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 15篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 20篇 |
1987年 | 39篇 |
1986年 | 42篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
山西省水资源开发利用对策措施 总被引:2,自引:0,他引:2
通过对山西省水资源状况及面临的水资源形势分析,提出了山西省水资源开发和利用的对策。山西省在未来10年内水资源开发利用应继续遵循“西引黄河,东抓蓄调,腹部盆地节调并举”的战略思想,只有加强以农田水利为重点的农村基础设施建设,继续抓好大中型水利工程的立项建设,鼓励支持社会各方力量兴办中小型水利工程,加强农业节水工程建设,推广农业高效用水技术,才能使山西省大部分地区的水资源短缺状况将得到极大改善,为全省国民经济和社会可持续发展提供支撑和保障。 相似文献
12.
An account is given of some principal observations made from a series of experiments in which three-span pipe beams were subjected to central impact by indenters with different nose shapes. These pipes were filled and pre-pressurized with water in order to identify the main effects produced by the fluid–structure interaction. In comparison, the impact experiments of the pipes with no water were also carried out. The perforation failure modes and corresponding critical impact energies were obtained in different test conditions. The experimental results indicated that the critical perforation energy and the deformation of the wall of the pipe were significantly influenced by the presence of the water and the pressure. 相似文献
13.
《Materials Letters》2007,61(4-5):1134-1136
In the present study, vapor-grown carbon nanofibers with 0.5 wt.% loading were dry-mixed with polypropylene powder by mechanical means, and extruded into filaments by using a single screw extruder. TGA results showed that decomposition temperature has increased 18.9 °C by filling CNFs in polypropylene. Tensile results demonstrated that tensile modulus and tensile strength have increased by 154% and 69.5%, respectively. A SEM picture indicated that an increase in mechanical properties is due to the well dispersion and alignment of CNFs in the filaments. 相似文献
14.
《Composites Part A》2007,38(11):2283-2293
The study of the variation of the curvature of non-symmetric composite laminates with temperature provides a measure of the magnitude of the thermal stresses and the mechanical behavior of the material with temperature. In the present work, an experimental method based on the pioneer use of a digital camera and image processing method is proposed to perform such measurements. Taking advantage of the method and by comparing experimental and CLT, extended-CLT and FEM simulation results, an evaluation of the residual stresses is described and an approach providing more precise determination of the residual thermal stresses in non-symmetric laminates is proposed. 相似文献
15.
Zeolite beta with a low SiO2/Al2O3 ratio was synthesized by a novel two-step process.The synthesized sample was characterized with XRD,SEM,FTIR,and N2 adsorption-desorption and solid-state MAS NMR.The results showed that aluminium species were inserted into the framework of zeolite beta.The BET surface area,volume,and particle size of the zeolite beta sample decreased with decreasing SiO2/Al2O3 ratio.Our process was proved an efficient route to synthesize zeolite beta with a low SiO2/Al2O3 ratio. 相似文献
16.
17.
RFID复杂事件处理是一个新兴的技术领域,它用来处理大量的简单事件,并从中整理出有价值的事件。RFID事件和传统的事件相比较具有海量性、空间性和时间性、数据不准确性等特征。文中在分析RFID数据特点的基础上,对RFID复杂事件处理的关键技术进行研究和改进,主要介绍RFID数据的清洗和事件检测技术。对于RFID数据清洗部分,提出了多层次过滤的方法使得到的数据更接近真实情况,而事件检测方面则提出了局部检测和全局检测相结合的方法对相关数据进行检测以得到更有意义的数据供上层应用使用。最后,对RFID复杂事件处理的发展趋势做出展望。 相似文献
18.
Because the spatial pattern of plant communities in garden landscapes usually exhibits highly non-random distribution characteristics, the accuracy of the analysis results is not high. For this purpose, a spatial ecological distribution model of landscape landform plant communities is designed. Based on the remote sensing images of landscape plant communities, the study area was obtained. The grassland communities in this area were classified and calculated by geostatistics, and the semi variogram values of typical samples of different vegetation types were obtained. According to the calculation results, the spatial terrain factors of landscape plant community are extracted, and the annual NDVI value is taken as the ecological vitality index of landscape green vegetation, the NDVI level is divided, the spatial ecological distribution model of landscape plant community is constructed, and the evaluation index system is generated, so as to complete the spatial ecological distribution model analysis of landscape plant community. The results show that the method of this study accurately analyzes the area of coniferous and broad-leaved mixed forest, mountain meadow, road, construction land, water area land and slope grade, which is slightly different from the actual value, indicating that the method has certain reliability. 相似文献
19.
针对选煤厂运煤火车人工喷洒防冻液不均匀的问题,设计了一种基于CC-Link的火车皮防冻液自动喷洒系统。该系统采用CC-Link现场总线技术将多套喷洒装置和防冻液加压泵站构建成工业现场级控制网络,实现了各装置之间的联动和实时监控。实际应用表明,该系统避免了防冻液的浪费,提高了工作效率。 相似文献
20.
Sergio Herrerı´a-Alonso Miguel Rodrı´guez-Pérez Manuel Fernández-Veiga Cándido López-Garcı´a 《Computer Networks》2012,56(10):2456-2467
The IEEE 802.3az standard provides a new low power mode that Ethernet network interfaces can use to save energy when there is no traffic to transmit. Simultaneously with the final standard approval, several algorithms were proposed to govern the physical interface state transition between the normal active mode and the new low power mode. In fact, the standard leaves this sleeping algorithm unspecified to spur competition among different vendors and achieve the greatest energy savings. In this paper, we try to bring some light to the most well known sleeping algorithms, providing mathematical models for the expected energy savings and the average packet delay inflicted on outgoing traffic. We will then use the models to derive optimum configuration parameters for them under given efficiency constraints. 相似文献