全文获取类型
收费全文 | 17146篇 |
免费 | 2561篇 |
国内免费 | 1782篇 |
专业分类
电工技术 | 1115篇 |
综合类 | 2594篇 |
化学工业 | 1233篇 |
金属工艺 | 374篇 |
机械仪表 | 1027篇 |
建筑科学 | 1222篇 |
矿业工程 | 464篇 |
能源动力 | 455篇 |
轻工业 | 1112篇 |
水利工程 | 783篇 |
石油天然气 | 574篇 |
武器工业 | 269篇 |
无线电 | 1882篇 |
一般工业技术 | 2250篇 |
冶金工业 | 394篇 |
原子能技术 | 127篇 |
自动化技术 | 5614篇 |
出版年
2024年 | 82篇 |
2023年 | 305篇 |
2022年 | 666篇 |
2021年 | 738篇 |
2020年 | 814篇 |
2019年 | 687篇 |
2018年 | 684篇 |
2017年 | 754篇 |
2016年 | 810篇 |
2015年 | 818篇 |
2014年 | 1087篇 |
2013年 | 1299篇 |
2012年 | 1312篇 |
2011年 | 1367篇 |
2010年 | 1014篇 |
2009年 | 1007篇 |
2008年 | 1041篇 |
2007年 | 1127篇 |
2006年 | 966篇 |
2005年 | 751篇 |
2004年 | 626篇 |
2003年 | 508篇 |
2002年 | 461篇 |
2001年 | 395篇 |
2000年 | 335篇 |
1999年 | 254篇 |
1998年 | 227篇 |
1997年 | 210篇 |
1996年 | 167篇 |
1995年 | 171篇 |
1994年 | 120篇 |
1993年 | 106篇 |
1992年 | 95篇 |
1991年 | 87篇 |
1990年 | 83篇 |
1989年 | 66篇 |
1988年 | 58篇 |
1987年 | 27篇 |
1986年 | 37篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1961年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
The operational optimisation of coal-fired power units is important for saving energy and reducing losses in the electric power industry. One of the key issues is how to determine the benchmark values of the energy efficiency indexes of the units. Therefore, a new framework for determining these benchmark values is proposed, based on data mining methods. First, the energy efficiency key performance indicators (KPIs) associated with the net coal consumption rate (NCCR) were selected based on the domain knowledge. Second, the decision-making samples with minimal NCCR were acquired with the fuzzy C-means (FCM) clustering algorithm, and the corresponding clustering centres were employed as the benchmark values. Finally, based on the support vector regression (SVR) algorithm, the target values of the NCCR were obtained with the KPIs as input, and the energy saving potential was evaluated by comparing the target values with the historical values of the NCCR. An actual on-duty 1000 MW unit was taken as study unit, and the results show that the energy saving potential is remarkable when the operators adjust the KPIs based on the calculated benchmark values. 相似文献
12.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
13.
14.
基于深度学习的人体姿态估计方法旨在通过构建合适的神经网络,直接从二维的图像特征中回归出人体姿态信息。主要按照2D人体姿态估计到3D人体姿态估计的顺序,并从单人检测与多人检测、稀疏的关节点检测与密集的模型构建等方面,对近年来基于深度学习的人体姿态估计方法进行系统介绍,从而初步了解如何通过深度学习的方法得到人体姿态的各个要素,包括肢体部件的相对朝向和比例尺度、骨骼关节点的位置坐标和连接关系,甚至更为复杂的人体蒙皮模型信息。最后,对当前研究面临的挑战以及未来的热点动向进行概述,清晰地呈现出该领域的发展脉络。 相似文献
15.
In this paper, the development of the models for the prediction of rock mass P wave velocity is presented. For model development, the database of 53 cases including widely used and recorded drilling parameters and P wave velocity was constructed from the field studies conducted in 13 open pit lignite mines. Both conventional linear, non-linear multiple regression and Adaptive Neuro Fuzzy Inference System (ANFIS) were used for model development. Prediction performance indicators showed that ANFIS model presented the best performance and it can successfully be used for the preliminary prediction of P wave velocities of rock masses. 相似文献
16.
超高性能混凝土(UHPC)在钢桥面铺装结构中由于铺装材料受到钢板、栓钉等的约束,加上材料本身水胶比小,更易收缩,早期容易承受拉应力导致开裂。通过在拌和过程中添加膨胀剂可以起到减小收缩的作用,但该方法对于约束条件下的UHPC铺装的早期抗裂性能提升是否有促进作用,仍需通过更多试验进行合理评估和深入研究。通过圆环法对3组不同配方的UHPC在均匀约束条件下的早期抗裂性能进行定量测试,并将试验数据进行回归分析和计算,得到了各组的平均应力发展速率,进而评估了各组的开裂风险等级。试验结果表明,通过在UHPC中加入适量膨胀剂,可使其最终收缩应力减小,并可降低其收缩应力发展速率,进一步降低其在约束条件下的开裂风险。 相似文献
17.
1-read/1-write (1R1W) register file (RF) is a popular memory configuration in modern feature rich SoCs requiring significant amount of embedded memory. A memory compiler is constructed using the 8T RF bitcell spanning a range of instances from 32 b to 72 Kb. An 8T low-leakage bitcell of 0.106 μm2 is used in a 14 nm FinFET technology with a 70 nm contacted gate pitch for high-density (HD) two-port (TP) RF memory compiler which achieves 5.66 Mb/mm2 array density for a 72 Kb array which is the highest reported density in 14 nm FinFET technology. The density improvement is achieved by using techniques such as leaf-cell optimization (eliminating transistors), better architectural planning, top level connectivity through leaf-cell abutment and minimizing the number of unique leaf-cells. These techniques are fully compatible with memory compiler usage over the required span. Leakage power is minimized by using power-switches without degrading the density mentioned above. Self-induced supply voltage collapse technique is applied for write and a four stack static keeper is used for read Vmin improvement. Fabricated test chips using 14 nm process have demonstrated 2.33 GHz performance at 1.1 V/25 °C operation. Overall Vmin of 550 mV is achieved with this design at 25 °C. The inbuilt power-switch improves leakage power by 12x in simulation. Approximately 8% die area of a leading 14 nm SoC in commercialization is occupied by these compiled RF instances. 相似文献
18.
19.
20.
随机减量技术中周期激励的影响及消除方法 总被引:3,自引:2,他引:1
本文针对机械系统中通常存在确定性周期激励的事实 ,论证了周期干扰成分的存在对提取的随机减量特征信号的影响 ,基于数字滤波技术提出了一种从周期干扰环境中提取随机减量特征信号的简便方法。在回转机械稳定性监测中的应用实例表明本文提出的方法是有效的。 相似文献