全文获取类型
收费全文 | 59571篇 |
免费 | 7302篇 |
国内免费 | 4498篇 |
专业分类
电工技术 | 6134篇 |
技术理论 | 1篇 |
综合类 | 5614篇 |
化学工业 | 7239篇 |
金属工艺 | 3650篇 |
机械仪表 | 4329篇 |
建筑科学 | 4805篇 |
矿业工程 | 2216篇 |
能源动力 | 1591篇 |
轻工业 | 5622篇 |
水利工程 | 1834篇 |
石油天然气 | 1965篇 |
武器工业 | 848篇 |
无线电 | 6999篇 |
一般工业技术 | 5545篇 |
冶金工业 | 2260篇 |
原子能技术 | 905篇 |
自动化技术 | 9814篇 |
出版年
2024年 | 409篇 |
2023年 | 1111篇 |
2022年 | 2440篇 |
2021年 | 3505篇 |
2020年 | 2386篇 |
2019年 | 1759篇 |
2018年 | 1940篇 |
2017年 | 2037篇 |
2016年 | 1911篇 |
2015年 | 3013篇 |
2014年 | 3469篇 |
2013年 | 4117篇 |
2012年 | 4851篇 |
2011年 | 5127篇 |
2010年 | 4729篇 |
2009年 | 4391篇 |
2008年 | 4275篇 |
2007年 | 4206篇 |
2006年 | 3609篇 |
2005年 | 2894篇 |
2004年 | 2113篇 |
2003年 | 1502篇 |
2002年 | 1450篇 |
2001年 | 1305篇 |
2000年 | 1050篇 |
1999年 | 497篇 |
1998年 | 240篇 |
1997年 | 191篇 |
1996年 | 149篇 |
1995年 | 140篇 |
1994年 | 79篇 |
1993年 | 69篇 |
1992年 | 71篇 |
1991年 | 35篇 |
1990年 | 33篇 |
1989年 | 53篇 |
1988年 | 20篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 18篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1959年 | 16篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
针对PTA装置的工艺生产特点,对自动控制系统当中出现的不同种类的问题,进行了多方面的简要探讨与分析,并提出实现安稳运行相应的对策。 相似文献
82.
The oxidation behavior of a Cu60Hf25Ti15 bulk metallic glass was studied over the temperature range of 375–520 °C in dry air. The oxidation kinetics of the amorphous
alloy generally followed the parabolic law at all temperatures, with an oxidation rate increasing with temperature. The oxidation
rates of the amorphous alloy were much higher than those of polycrystalline pure-Cu, implying that the additions of Hf and
Ti accelerated the oxidation reaction. The composition of the scales formed on the amorphous alloy was strongly temperature-dependent,
since they consisted mostly of Cu4O3 and CuO with minor amounts of HfO2 at T ≤ 450 °C, while mostly CuO with minor amounts of HfO2 and Cu2TiO3 were detected at higher temperatures. In addition, nanocrystalline Cu51Hf14 and Cu3Ti2 phases were detected on the substrate after oxidation at T ≥ 450 °C, indicating the occurrence of phase transformation. 相似文献
83.
Effects of Heat Treatment on the Transformation Temperature and the Microstructure of Ni-Ti-Nb Shape Memory Alloy 总被引:1,自引:0,他引:1
The effects of heat treatment on the phase transformation temperature and the microstructure of Ni-Ti-Nb alloy have been investigated by means of R-T method, TEM and EPMA. With the increase of annealing temperature, cooling rate and ageing temperature, the Ms temperature increases. TEM observations show no new precipitated phase was found in the B2 parent phase after heat treatment, but EPMA shows the content of Ni (or Ni/Ti ratio) in the B2 matrix changed. The main reason for the change of transformation temperature lies in the change of the matrix composition (or Ni/Ti ratio) with the variation of heat treatment procedure. 相似文献
84.
Kanamaluru S. Ming-Yi Li Kai Chang 《Antennas and Propagation, IEEE Transactions on》1996,44(7):964-974
This paper presents the analysis and design of aperture-coupled microstrip patch antennas and arrays fed by an dielectric image line. A theory based on the cavity model of the microstrip patch antenna and the change in the modal voltage of the image line at the aperture was developed to analyze the single element aperture-coupled microstrip patch antenna. The theory developed was combined with the array theory to design linear traveling wave arrays at X-band and Ka-band frequencies. The required taper in the excitations of the individual patches of the array was achieved by varying the aperture dimensions. Experiments show very good results for the antennas and the arrays 相似文献
85.
In this paper,we address the need for better hands-on learning materials in computing education and the need for integrating mobile computing education into computing curricular.We propose an innovative learning approach that uses state-of-the-art mobile computing technologies and devices to design a highly accessible and real-world relevant hands-on labware for computing education.The labware employs a modular design such that the learning materials can both be combined together into a single course of mobile program development and be integrated into the related computing courses as building blocks.The labware will help students understand the concepts,improve their problem solving skills,and prepare them for the mobile computing industrial workforce.The pilot modules of the labware have been presented to undergraduate students and have received positive feedbacks. 相似文献
86.
A new formation navigation approach derived from multi-robots cooperative online FastSLAM is proposed. In this approach,the leader and follower robots are defined.The posteriori estimation of the leader robot state is treated as a relative reference for all follower robots to correct their state priori estimations.The control volume of individual follower will be achieved from the results of the corrected estimation.All robots are observed as landmarks with known associations by the others and are considered in their landmarks updating.By the method,the errors of the robot posterior estimations are reduced and the formation is well kept.The simulation and physical experiment results show that the multi-robots relative localization accuracy is improved and the formation navigation control is more stable and efficient than normal leader-following strategy.The algorithm is easy in implementation. 相似文献
87.
88.
CAE技术在汽轮机高温强度计算中的应用 总被引:1,自引:0,他引:1
为分析某百万千瓦超超临界汽轮机高压缸旋转部件在高温以及高离心力载荷下的强度状况,建立高压缸第一级动叶片的模型.根据蠕变试验数据,采用最小二乘法拟合幂蠕变方程中的各个参数,并详细介绍各参数的拟合、优化和验算过程;用CFD分析软件计算流体域内的对流传热系数并插值到有限元计算程序中,分析叶根倒角处危险区域的蠕变应力状况.数据验算结果表明,利用拟合数据计算得到的蠕变应力值与试验值比较接近,证明该方法可靠;CAE计算结果表明,叶根倒角处危险区域蠕变应力考核合格,并且有充足的安全裕量. 相似文献
89.
武凯 《电脑编程技巧与维护》2012,(18):82-83,109
神东煤炭公司信息网络发展至今已经形成规模,在整个神华集团广域网中神东也是重要节点之一,肩负着周边各兄弟公司的广域网接入以及旗下众多煤矿和分公司业务数据的传输。由于神东网络属于自然发展型网络,在网络规模建设初期,问题容易规避,在形成规模以后,各种潜在的问题都可能导致网络故障从而影响整体网络的正常运行。分别从神东煤炭集团公司局域网、宽带网、井下工业以太网3个方面分别进行详细阐述。 相似文献
90.
叶锴 《电脑编程技巧与维护》2012,(6):90-91,100
信息化建设在环境监测行业中日渐成熟,对于该行业的稳步提升有着不可或缺的作用,然而由于该行业信息化建设处于起步阶段,尤其是在应用的信息系统在安全问题上还需强化,基于目前现状,列举环境监测领域信息系统出现的一些突出问题,并对其中的原因进行分析,同时提出了环境监测信息系统安全问题的防御措施。 相似文献