全文获取类型
收费全文 | 23433篇 |
免费 | 3444篇 |
国内免费 | 1701篇 |
学科分类
工业技术 | 28578篇 |
出版年
2024年 | 154篇 |
2023年 | 557篇 |
2022年 | 784篇 |
2021年 | 978篇 |
2020年 | 947篇 |
2019年 | 830篇 |
2018年 | 860篇 |
2017年 | 1052篇 |
2016年 | 1092篇 |
2015年 | 1255篇 |
2014年 | 1983篇 |
2013年 | 1616篇 |
2012年 | 1990篇 |
2011年 | 1930篇 |
2010年 | 1323篇 |
2009年 | 1343篇 |
2008年 | 1191篇 |
2007年 | 1451篇 |
2006年 | 1285篇 |
2005年 | 1025篇 |
2004年 | 857篇 |
2003年 | 729篇 |
2002年 | 571篇 |
2001年 | 520篇 |
2000年 | 411篇 |
1999年 | 315篇 |
1998年 | 261篇 |
1997年 | 190篇 |
1996年 | 167篇 |
1995年 | 137篇 |
1994年 | 138篇 |
1993年 | 94篇 |
1992年 | 91篇 |
1991年 | 53篇 |
1990年 | 92篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 27篇 |
1986年 | 63篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
L. K. Rihko-Struckmann Y. Ye L. Chalakov Y. Suchorski H. Weiss K. Sundmacher 《Catalysis Letters》2006,109(1-2):89-96
In the first part of this work, the electrical conductivity of vanadium phosphorous oxide (VPO) catalyst was investigated
by means of the 2-probe EIS method. The VPO showed an extremely low conductivity at low oxygen partial pressure, which is
the prevailing condition in the anodic compartment in an electrochemical membrane reactor (EMR). In the second part of this
study, fresh as well as VPO catalyst already used in an EMR were characterised with XRD, XPS and temperature programmed oxidation
(TPO). The XRD measurements revealed an unchanged bulk phase structure after operation in the EMR. Significant differences
in the average oxidation states of vanadium in the catalyst layer in the EMR were determined via XPS, where the catalyst surface
facing the electrolyte membrane was more oxidised than the surface facing the anodic gas compartment. The lowered uptake and
release of oxygen was observed in TPO experiments for the catalyst used in the EMR. 相似文献
102.
A thin film of yttrium Y (150 nm) protected by a 6 nm coating of nickel Ni on a glass substrate was completely hydrogenated in a 1 M NaOH electrolyte at a constant negative current until the transparent Y tri-hydride phase was achieved and hydrogen gas evolution from the electrode began. A series of impedance measurements were performed in situ during the electrochemical experiment to study the properties of the system as dependent on hydrogenation degree and time of relaxation. The equivalent electrical circuit (EEC) simulations were performed with a Randles-like scheme R0[R1CPE1], where R0 is the thin film electrode resistance, R1 the charge transfer resistance and CPE1 is the capacitive constant phase element. The behavior of all the components of the EEC undergoes a clear transition when the hydrogenation degree of the electrode is approximated to its maximum value (H to Y ratio 2.7) and electrochemical process changes from hydrogen uptake to hydrogen evolution. 相似文献
103.
Sang Woo Kim Jong-Ho Lee Joosun Kim Hae-Weon Lee 《Journal of the American Ceramic Society》2004,87(12):2213-2217
The effect of zinc ions added to silica film on the electrical and structural properties of a silica/indium tin oxide two-layer film which had been prepared by solution coating for electromagnetic shielding of displays was studied. The volume resistivity of the undoped silica/indium tin oxide film was more than 3 times as high as that of the zinc-doped silica/indium tin oxide film. The addition of divalent cations, zinc ions, to the overcoated layer led volume resistivity of the two-layer film to decrease significantly and also caused a long-term increase in stability. The decrease in volume resistivity was due to the addition of zinc ions that changed the interface ionization and helped to enhance the electrical conductivity in the two-layer film. 相似文献
104.
A technique to test electrodialysis (ED) stacks designed to desalt dilute solutions is developed. The technique permits obtaining reproducible data on laboratory and medium-scale units useful for predicting mass transfer characteristics of large ED stacks. Quasi-steady state of desalination process is the main condition to obtain such data. This state can be attained by applying recycling hydraulic modes and special devices to maintain constant pH, or pH and concentration of the feed solution. To obtain data for scaling, it is necessary to apply a fixed voltage on the stack and to use a constant flow rate of the feed solution during the experiment, the feed solution concentration may vary with the time. Specifications of the stacks studied, rational hydraulic and electrical modes of testing are considered. 相似文献
105.
发动机组是火电厂各生产环节中重要的组成部分,其运行效率不但决定了生产效率,还关系着各类生产资源应用的有效性,对实现节能降耗具有重要意义,所以,必须加强对其运行稳定性的管理。分析了火电厂发动机组常见电气故障,并提出了相应的解决措施。 相似文献
106.
机电安装在建筑工程中涉及的专业面非常广泛,学科跨度较大。虽然机电安装有自身的固有特征,但它的通用性很强。分析了机电安装工程的概况、特点和相关技术,研究了机电安装中出现的问题,并提出相应的解决措施。 相似文献
107.
防火审核是建筑电气设计审核中的一个重要组成部分,要严格按照相关的防火规范设计和审核其设计,为建筑安全打下坚实的基础。分析、探讨了电气系统设计中防火审核的方法和相关技术,并提出了相关的设计对策和建议,以期能为相关人员提供参考。 相似文献
108.
109.
变电运行与人们和社会生产的各个方面息息相关,而跳闸故障是变电运行中的主要故障。通过对变电运行系统中的跳闸故障进行分析,探讨了跳闸故障的处理技术,以供参考。 相似文献
110.
为了保证电厂的生产效率,必须要分析电气的运行特征,确定电气故障发生的原因,综合考虑多方面因素,选择切实可行的措施解决问题。简要分析了电厂电气运行常见故障发生原因,并提出了相应的解决措施。 相似文献