全文获取类型
收费全文 | 25446篇 |
免费 | 2247篇 |
国内免费 | 1031篇 |
专业分类
电工技术 | 509篇 |
技术理论 | 4篇 |
综合类 | 1882篇 |
化学工业 | 2844篇 |
金属工艺 | 5585篇 |
机械仪表 | 5262篇 |
建筑科学 | 1307篇 |
矿业工程 | 1123篇 |
能源动力 | 523篇 |
轻工业 | 608篇 |
水利工程 | 743篇 |
石油天然气 | 814篇 |
武器工业 | 676篇 |
无线电 | 499篇 |
一般工业技术 | 4009篇 |
冶金工业 | 1484篇 |
原子能技术 | 177篇 |
自动化技术 | 675篇 |
出版年
2024年 | 188篇 |
2023年 | 514篇 |
2022年 | 744篇 |
2021年 | 890篇 |
2020年 | 954篇 |
2019年 | 765篇 |
2018年 | 849篇 |
2017年 | 1063篇 |
2016年 | 1067篇 |
2015年 | 1032篇 |
2014年 | 1354篇 |
2013年 | 1529篇 |
2012年 | 1533篇 |
2011年 | 1696篇 |
2010年 | 1298篇 |
2009年 | 1288篇 |
2008年 | 1156篇 |
2007年 | 1537篇 |
2006年 | 1515篇 |
2005年 | 1160篇 |
2004年 | 1066篇 |
2003年 | 863篇 |
2002年 | 736篇 |
2001年 | 673篇 |
2000年 | 562篇 |
1999年 | 456篇 |
1998年 | 390篇 |
1997年 | 366篇 |
1996年 | 329篇 |
1995年 | 278篇 |
1994年 | 216篇 |
1993年 | 125篇 |
1992年 | 122篇 |
1991年 | 89篇 |
1990年 | 84篇 |
1989年 | 65篇 |
1988年 | 54篇 |
1987年 | 29篇 |
1986年 | 9篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
分析了型钢厂试制热轧美标H型钢低温冲击韧性偏低的原因,并在此基础上提出了对生产工艺的优化与改进。 相似文献
62.
Barry D. Solomon 《Energy Policy》1985,13(1):97-101
The prospects for rapid near-term development of a synfuel industry in the USA have decreased, due to depressed world oil prices, synfuel project cost overruns, and the lukewarm support of the Reagan administration. Nonetheless, socioeconomic and environmental impact analysis studies can provide valuable information for determining the regional welfare effects of proposed projects. The author discusses the results of a regional econometric analysis of the synfuel projects planned for Western Kentucky, which focuses on environmental impacts, and reveals the inevitable trade-offs that would accompany synfuel development. Some policy issues are briefly reviewed, especially that of efficient energy pricing. 相似文献
63.
该文研究了T300碳纤维单向增强的环氧复合材料,在应变率从10~(-3)/s到10~3/s范围内的冲击拉伸行为.通过对实验数据进行拟合,得出该范围内材料对应变率具有弱的敏感性,表现在破坏强度及破坏应变随应变率增加不显著变化,平均模量几乎不受应变率的影响.分析了试件的几何尺寸效应,讨论了应力波作用对破坏形态的影响以及实验中观察到的拔出现象.从应变率在10~2~10~3/s附近材料行为某些非确定性,指出在更宽范围内了解其性能的必要性. 相似文献
64.
65.
水电站的技术供水系统要根据水电站的基本技术参数及设备要求的技术供水参数进行详细设计和论证,并结合电站所在区域的实际情况,使系统满足机组在各种工况下的正常安全稳定运行。主要阐述米角河一级水电站立轴冲击式水轮发电机组技术供水系统的优化设计,采用一次冷却供水和冷却水二次循环供水相结合的设计方案,避免供水水质变化时停机造成的经济损失,提高了供水系统的运行可靠性,减少了检修维护量,为电站"无人值班,少人值守"创造了必要条件。 相似文献
66.
Seepage well is an emerging Low Impact Development (LID) technology that can effectively control the storm runoff. However, its rainwater infiltration rate and storage capacity still require further enhancement. By setting a horizontal infiltration structure at the bottom of conventional rainwater seepage well (CSW), an enhanced seepage well (ESW) was proposed in this study, and its infiltration performances compared with the permeable pavement (PP) and the CSW were systemically investigated using static infiltration experiment and HYDRUS-2D simulation. The results showed that the infiltration efficiency of ESW was significantly higher than that of PP and CSW, and the process of water infiltrated through soil mainly controlled the macroscopic infiltration rate. The Nash-Sutcliff Efficient (NSE) index was used to evaluate the accuracy and reliability of the HYDRUS-2D model, and the results of NSE values greater than 0.75 (varied between 0.75 and 0.91) confirmed the applicability of HYDRUS-2D to describe correctly the hydraulic behavior of the ESW system. Simulation infiltration tests showed that the ESW performed a higher average infiltration rate and fewer total runoff volume than the CSW, indicating the effectively enhancement of the infiltration and water retention capacity of ESW, especially under heavy rainfall intensities. Additionally, the ESW system exhibited an excellent runoff-control and rainwater retention capacity in an actual rainfall scenario. 相似文献
67.
Effective tool wear monitoring (TWM) is essential for accurately assessing the degree of tool wear and for timely preventive maintenance. Existing data-driven monitoring methods mainly rely on complex feature engineering, which reduces the monitoring efficiency. This paper proposes a novel TWM model based on a parallel residual and stacked bidirectional long short-term memory (PRes–SBiLSTM) network. First, a parallel residual network (PResNet) is used to extract the multi-scale local features of sensor signals adaptively. Subsequently, a stacked bidirectional long short-term memory (SBiLSTM) network is used to obtain the time-series features related to the tool wear characteristics. Finally, the predicted tool wear value is outputted through a fully connected network. A smoothing correction method is applied to improve the prediction accuracy. The proposed model is experimentally verified to have a high prediction accuracy without sacrificing its generalization ability. A TWM system framework based on the PRes–SBiLSTM network is proposed, which has a certain reference value for TWM in actual industrial environments. 相似文献
68.
69.
Discusses retouching of the Kallikak family photographs in H. H. Goddard's (1912) study of mental retardation and heredity, with reference to analyses by R. E. Fancher (see record 1987-31600-001) and S. J. Gould (1981), and concurs with Fancher that the retouching was probably not done for deceitful purposes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
It appears that those federal agencies responsible for enforcement persist in the belief that a given test score can mean one thing in one subgroup and something else in another and/or that inferences from a set of test scores can be valid for one subgroup but not for another. First surfacing in early agency regulations in connection with the now discontinued "differential validity" requirement, the belief still manifests itself in the concepts of "unfairness" and "adverse impact." Furthermore, the determination of the presence or absence of adverse impact on the basis of the impact ratio involves numerous statistical and measurement issues. Use of the impact ratio to establish the prosecutorial posture of an enforcement agency is clearly flawed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献