全文获取类型
收费全文 | 117124篇 |
免费 | 9568篇 |
国内免费 | 5304篇 |
专业分类
电工技术 | 11361篇 |
技术理论 | 29篇 |
综合类 | 8751篇 |
化学工业 | 12309篇 |
金属工艺 | 4727篇 |
机械仪表 | 5750篇 |
建筑科学 | 11436篇 |
矿业工程 | 5312篇 |
能源动力 | 7622篇 |
轻工业 | 11984篇 |
水利工程 | 3079篇 |
石油天然气 | 4853篇 |
武器工业 | 2395篇 |
无线电 | 11819篇 |
一般工业技术 | 6979篇 |
冶金工业 | 4333篇 |
原子能技术 | 510篇 |
自动化技术 | 18747篇 |
出版年
2024年 | 384篇 |
2023年 | 1815篇 |
2022年 | 3251篇 |
2021年 | 4029篇 |
2020年 | 4011篇 |
2019年 | 2961篇 |
2018年 | 2474篇 |
2017年 | 3375篇 |
2016年 | 3630篇 |
2015年 | 4051篇 |
2014年 | 8837篇 |
2013年 | 6596篇 |
2012年 | 8716篇 |
2011年 | 9104篇 |
2010年 | 6905篇 |
2009年 | 6984篇 |
2008年 | 6461篇 |
2007年 | 7783篇 |
2006年 | 6950篇 |
2005年 | 6088篇 |
2004年 | 5308篇 |
2003年 | 4667篇 |
2002年 | 3804篇 |
2001年 | 3158篇 |
2000年 | 2422篇 |
1999年 | 1923篇 |
1998年 | 1343篇 |
1997年 | 992篇 |
1996年 | 862篇 |
1995年 | 710篇 |
1994年 | 559篇 |
1993年 | 386篇 |
1992年 | 320篇 |
1991年 | 219篇 |
1990年 | 168篇 |
1989年 | 132篇 |
1988年 | 113篇 |
1987年 | 81篇 |
1986年 | 81篇 |
1985年 | 76篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 916 毫秒
21.
22.
华治国 《混凝土与水泥制品》2020,(6):70-72
选择了几份典型的外墙外保温系统标准,通过对这几份标准中胶粘剂和抹面胶浆的成型和检测方法的比较,分析了现有检测技术的优劣,并结合工作实践提出了建议。 相似文献
23.
构建工程咨询机构BIM技术应用能力评价的指标体系,提出改进的熵权TOPSIS评价模型,以4个典型的工程咨询单位为例,进行BIM技术运用能力评价。研究表明,BIM行业的整体水平已经有了明显的提升,但是区域间的发展还存在一定差距。 相似文献
24.
《Journal of the European Ceramic Society》2020,40(1):56-62
In this work, 0.2 wt.% Mn-doped (1-x)AgNbO3-xBi0.5Na0.5TiO3 (x = 0.00–0.04) ceramics were synthesized via solid state reaction method in flowing oxygen. The evolution of microstructure, phase transition and energy storage properties were investigated to evaluate the potential as high energy storage capacitors. Relaxor ferroelectric Bi0.5Na0.5TiO3 was introduced to stabilize the antiferroelectric state through modulating the M1-M2 phase transition. Enhanced energy storage performance was achieved for the 3 mol% Bi0.5Na0.5TiO3 doped AgNbO3 ceramic with high recoverable energy density of 3.4 J/cm3 and energy efficiency of 62% under an applied field of 220 kV/cm. The improved energy storage performance can be attributed to the stabilized antiferroelectricity and decreased electrical hysteresis ΔE. In addition, the ceramics also displayed excellent thermal stability with low energy density variation (<6%) over a wide temperature range of 20−80 °C. These results indicate that Mn-doped (1-x)AgNbO3-xBi0.5Na0.5TiO3 ceramics are highly efficient lead-free antiferroelectric materials for potential application in high energy storage capacitors. 相似文献
25.
This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations. 相似文献
26.
电化学储能器件的性能很大程度上决定于其电极材料。碳材料具有来源广泛、化学稳定性好、易于调控、环境友好等优点,被广泛应用于各类能量存储系统,但仍存在能量密度低、倍率性能差等问题。本文从碳材料孔结构调控、杂原子掺杂、与金属氧化物复合三个角度,综述了构建高性能碳基储能材料的设计合成策略,介绍了其在锂/钠离子二次电池、超级电容器等领域的研究进展,对几种方法策略的优缺点进行了总结,并对未来的研究方向进行了展望。本文对高性能碳基储能电极材料的设计开发具有积极意义。 相似文献
27.
28.
Zenan Yu Julian Moore Jean Calderon Lei Zhai Jayan Thomas 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(39):5289-5295
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets. 相似文献
29.
With the emergence of distributed ledger technology (DLT), numerous practitioners and researchers have proclaimed its beneficial impact on supply chain transactions in the future. However, the vast majority of DLT initiatives are discontinued after a short period. With the full potential of DLT laying far down the road, especially managers in supply chain management (SCM) seek for short-term cost-saving effects of DLT in order to achieve long-term benefits of DLT in the future. However, the extant research has bypassed grounding long-term as well as short-term effects of DLT on supply chain transaction with empirical data. We address this shortcoming, following an abductive research approach and combining empirical data from a multiple case study design with the corresponding literature. Our study reveals that the effects of DLT on supply chain transactions are two-sided. We found six effects of DLT solutions that have a cost-reducing or cost avoidance impact on supply chain transactions. In addition, we found two effects that change the power distribution between buyers and suppliers in transactions and a single effect that reduces the dependency of supply chain transactions on third parties. While cost-reducing and avoidance as well as dependency-reducing effects are positive effects, the change in power distribution might come with disadvantages. With these findings, the paper provides the first empirical evidence of the impact of DLT on supply chain transactions, which will enable managers to improve their assessment of DLT usage in supply chains. 相似文献
30.
本文针对典型高温气冷堆乏燃料厂房在双发商用飞机撞击载荷下的响应及结构完整性开展研究,并探讨结构特性对撞击损伤的影响。对乏燃料厂房及飞机分别建立有限元模型,通过弹体-目标相互作用分析模拟了飞机撞击过程,综合IAEA与NRC的评价准则对乏燃料厂房在飞机撞击下的损伤程度进行评估。数值结果表明:厂房上对应于机身及发动机的撞击位置发生可接受的局部损伤;乏燃料贮存井墙体对于提高构筑物抗飞机撞击能力有重要作用。此外,构筑物外形对损伤有很大影响,圆柱形壳体的抗飞机撞击能力显著强于方形厂房,是核电厂厂房设计的优化方向之一。 相似文献