全文获取类型
收费全文 | 3437篇 |
免费 | 57篇 |
国内免费 | 90篇 |
专业分类
电工技术 | 1401篇 |
综合类 | 135篇 |
化学工业 | 68篇 |
金属工艺 | 117篇 |
机械仪表 | 75篇 |
建筑科学 | 52篇 |
矿业工程 | 28篇 |
能源动力 | 161篇 |
轻工业 | 30篇 |
水利工程 | 103篇 |
石油天然气 | 13篇 |
武器工业 | 3篇 |
无线电 | 138篇 |
一般工业技术 | 108篇 |
冶金工业 | 978篇 |
原子能技术 | 27篇 |
自动化技术 | 147篇 |
出版年
2021年 | 4篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 55篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 26篇 |
2013年 | 58篇 |
2012年 | 43篇 |
2011年 | 209篇 |
2010年 | 81篇 |
2009年 | 77篇 |
2008年 | 56篇 |
2007年 | 75篇 |
2006年 | 47篇 |
2005年 | 71篇 |
2004年 | 536篇 |
2003年 | 183篇 |
2002年 | 157篇 |
2001年 | 139篇 |
2000年 | 71篇 |
1999年 | 250篇 |
1998年 | 342篇 |
1997年 | 224篇 |
1996年 | 151篇 |
1995年 | 89篇 |
1994年 | 69篇 |
1993年 | 120篇 |
1992年 | 52篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 4篇 |
1977年 | 46篇 |
1976年 | 85篇 |
1975年 | 8篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1970年 | 13篇 |
1969年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有3584条查询结果,搜索用时 62 毫秒
41.
42.
43.
船舶用碳钢表面镀Zn及其耐蚀性 总被引:4,自引:0,他引:4
为了提高船舶舱内碳钢制品的使用寿命,以20#碳钢 为例对其表面采用无氨、无氰溶液镀Zn以及钝化处理.研究了镀Zn试样在中性盐雾以及含有 机物质气氛中的耐蚀性能.结果表明:有机物质气氛是造成船舶舱内碳钢制品腐蚀的主要 原因,而无氨、无氰溶液进行镀Zn能在很大程度上解决碳钢表面的电化学腐蚀问题. 相似文献
44.
本文介绍了冷却器盘管破裂泄漏的情况,分析了失效破坏的原因,并提出防止冷却器盘管破裂泄漏的措施。 相似文献
45.
46.
Many high Miller index metals surfaces are naturally chiral, offering opportunities for performing enantiospecific chemistry. Previous theoretical treatments of adsorption on these surfaces have used surfaces truncated from bulk crystals. This paper examines the effect of surface relaxation on enantiospecific adsorption on chiral Pt surfaces by using relaxed surface structures determined using density functional theory. 相似文献
47.
This study presents a narrative synthesis of a systematic literature review relating to multi-agency interoperability and major incident decision-making in high risk, high stake environments. The review methodology includes the identification of relevant studies, a critical appraisal of the concepts inherent in the main review question and a narrative synthesis of the central themes that relate to the study as a whole. The review firstly outlines what, currently, appear to be the perceived defining features of successful interoperability by using the SAFE-T phase model of major incident decision-making. It then considers whether these defining features are realistically achievable in major incident practice. Findings suggest that the current definition of an interoperable network is too demanding for the inherent complexity and dynamic nature of the major incident task environment. Individual teams tend to focus on agency-specific behaviour, as opposed to coordinated multi-team functioning, and so collective interoperability is not achieved. Inevitably, this reduces the ability to perform collaborative behaviours, including decision-making and action implementation. The paper concludes that aiming for the current conceptualisation of interoperability along a hierarchical command structure may actually inhibit effective decision-making. Instead, multi-agency systems would do better to work towards an improved understanding of a non-hierarchical and decentralised yet interoperable major incident management network. Recommendations include the need to relate theory and practice in the development of multi-agency decision-making via simulation-based training and to deepen our understanding of interoperability to prevent inertia in high risk, high stake major incident environments. 相似文献
48.
This study uses a hostage negotiation setting to demonstrate how a team of strategic police officers can utilize specific coping strategies to minimize uncertainty at different stages of their decision-making in order to foster resilient decision-making to effectively manage a high-risk critical incident. The presented model extends the existing research on coping with uncertainty by (1) applying the RAWFS heuristic (Lipshitz and Strauss in Organ Behav Human Decis Process 69:149–163, 1997) of individual decision-making under uncertainty to a team critical incident decision-making domain; (2) testing the use of various coping strategies during “in situ” team decision-making by using a live simulated hostage negotiation exercise; and (3) including an additional coping strategy (“reflection-in-action”; Schön in The reflective practitioner: how professionals think in action. Temple Smith, London, 1983) that aids naturalistic team decision-making. The data for this study were derived from a videoed strategic command meeting held within a simulated live hostage training event; these video data were coded along three themes: (1) decision phase; (2) uncertainty management strategy; and (3) decision implemented or omitted. Results illustrate that, when assessing dynamic and high-risk situations, teams of police officers cope with uncertainty by relying on “reduction” strategies to seek additional information and iteratively update these assessments using “reflection-in-action” (Schön 1983) based on previous experience. They subsequently progress to a plan formulation phase and use “assumption-based reasoning” techniques in order to mentally simulate their intended courses of action (Klein et al. 2007), and identify a preferred formulated strategy through “weighing the pros and cons” of each option. In the unlikely event that uncertainty persists to the plan execution phase, it is managed by “reduction” in the form of relying on plans and standard operating procedures or by “forestalling” and intentionally deferring the decision while contingency planning for worst-case scenarios. 相似文献
49.
This paper describes the cylindrical agglomerate model for oxygen/alkali gas diffusion electrodes fabricated from platinum, PTFE and porous nickel. Corrections for the increase in hydroxyl ion concentration with increasing current density have been made to the original model of Brown and Horve. Changes in performance by variation of the bulk structural parameters, e.g. agglomerate radius, porosity and tortuosity, have been studied. Theoretical modes of electrode decay have been explored.List of symbols
Transfer coefficient
-
C
Concentration of O2 in elec trolyte mol cm–3
-
C
i
Concentration of O2 atr = R mol cm–3
-
C
o
Concentration of O2 in electrolyte atr = mol cm–3
-
Diffusion coefficient of O2 in KOH cm2 sec–1
-
Film thickness cm
-
E
Overpotential of the electrode V
-
F
Faraday's constant
-
i
Electrode current density A cm–2
-
i
a
Current per agglomerate A
-
I
1(Z)
First order Bessel function
-
I
0(Z)
Zero order Bessel function
-
j
Local current density A cm–2
-
j
o
Exchange current density A cm–2
-
L
Agglomerate length (catalyst thickness) cm
-
N
Number of electrons in rate determining step
-
N
a
Number of agglomerates per cm2 of electrode
-
Potential drop along ag glomerate V
-
L
Potential drop at La V
-
r
Radial direction
-
R
Radius of agglomerate cm
-
R
o
Gas constant
-
Density of platinum g cm–3
-
S
g
Surface area per gram cm2 g–1
-
Solubility coefficient of O2 mol cm–3
- m
Electrolyte conductivity (ohm cm)–1
-
T
Absolute temperature °K
- a
Axial tortuosity
-
Porosity of platinum in the agglomerate
- r
Aadial tortuosity of the agglomerate
-
W
Catalyst loading g cm–2
-
x
Axial direction 相似文献
50.
ZHOU HaiQiang JU Ping YANG Hui & SUN Ran Electrical Engineering School HoHai University Nanjing China Henan Power Dispatching & Communication Center Zhengzhou 《中国科学:信息科学(英文版)》2010,(4)
The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus... 相似文献