全文获取类型
收费全文 | 12615篇 |
免费 | 555篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 126篇 |
综合类 | 4篇 |
化学工业 | 2784篇 |
金属工艺 | 242篇 |
机械仪表 | 248篇 |
建筑科学 | 512篇 |
矿业工程 | 29篇 |
能源动力 | 387篇 |
轻工业 | 1075篇 |
水利工程 | 128篇 |
石油天然气 | 59篇 |
武器工业 | 7篇 |
无线电 | 852篇 |
一般工业技术 | 2314篇 |
冶金工业 | 2291篇 |
原子能技术 | 96篇 |
自动化技术 | 2036篇 |
出版年
2023年 | 74篇 |
2022年 | 109篇 |
2021年 | 208篇 |
2020年 | 199篇 |
2019年 | 192篇 |
2018年 | 246篇 |
2017年 | 263篇 |
2016年 | 314篇 |
2015年 | 228篇 |
2014年 | 350篇 |
2013年 | 883篇 |
2012年 | 620篇 |
2011年 | 794篇 |
2010年 | 511篇 |
2009年 | 552篇 |
2008年 | 723篇 |
2007年 | 640篇 |
2006年 | 585篇 |
2005年 | 495篇 |
2004年 | 434篇 |
2003年 | 388篇 |
2002年 | 331篇 |
2001年 | 201篇 |
2000年 | 210篇 |
1999年 | 205篇 |
1998年 | 223篇 |
1997年 | 196篇 |
1996年 | 189篇 |
1995年 | 181篇 |
1994年 | 197篇 |
1993年 | 178篇 |
1992年 | 156篇 |
1991年 | 118篇 |
1990年 | 117篇 |
1989年 | 131篇 |
1988年 | 109篇 |
1987年 | 108篇 |
1986年 | 113篇 |
1985年 | 132篇 |
1984年 | 112篇 |
1983年 | 100篇 |
1982年 | 103篇 |
1981年 | 108篇 |
1980年 | 76篇 |
1979年 | 76篇 |
1978年 | 87篇 |
1977年 | 73篇 |
1976年 | 62篇 |
1975年 | 72篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
With worldwide energy consumption rising, there is a need to reduce energy use of the housing stock. While this general idea is well-known, there is an overwhelming amount of product data and manufacturers claims through which the homebuilder or designer must sort to make informed selections of energy-efficient upgrades. The main objective of this research was to identify cost effective–energy efficient upgrades from a group of 16 commonly available choices, and rank them according to the most beneficial for the least cost. This study was conducted in Phoenix, Arizona, and included a sample of 30 production-style homes typical of the Phoenix metropolitan area. Energy-simulation software was used to perform energy evaluations and derive the benefits of each upgrade. The cost of each upgrade was obtained from a database of national average costs and from a local context. Differences in the selection of beneficial upgrades vary dramatically with the source of the cost information. This research provides a generic methodology that can be used by builders and designers to select appropriate energy-efficient upgrades for a given geographic area that will provide high operating benefits relative to the amount of capital investment. 相似文献
62.
M. Nyoka G. Akdogan R. H. Eric N. Sutcliffe 《Metallurgical and Materials Transactions B》2003,34(6):833-842
The process of mixing and solid-liquid mass transfer in a one-fifth scale water model of a 100-ton Creusot-Loire Uddeholm
(CLU) converter was investigated. The modified Froude number was used to relate gas flow rates between the model and its protoype.
The influences of gas flow rate between 0.010 and 0.018 m3/s and bath height from 0.50 to 0.70 m on mixing time were examined. The results indicated that mixing time decreased with
increasing gas flow rate and increased with increasing bath height. The mixing time results were evaluated in terms of specific
energy input and the following correlation was proposed for estimating mixing times in the model CLU converter: T
mix=1.08Q
−1.05
W
0.35, where Q (m3/s) is the gas flow rate and W (tons) is the model bath weight. Solid-liquid mass-transfer rates from benzoic acid specimens immersed in the gas-agitated
liquid phase were assessed by a weight loss measurement technique. The calculated mass-transfer coefficients were highest
at the bath surface reaching a value of 6.40 × 10−5 m/s in the sprout region. Mass-transfer coefficients and turbulence parameters decreased with depth, reaching minimum values
at the bottom of the vessel. 相似文献
63.
In this article, the authors seek to strengthen the theoretical foundation of team and cell formation through the inclusion of human factors. They distinguish three types of team characteristics: global, shared, and compositional attributes. In this last category, they also deal with diversity in teams by addressing three types of variables: demographic characteristics, skills and knowledge, and personality traits. In addition, the authors address the relevance of the structure of diversity in cells. For each of the above‐mentioned groups of team characteristics, their potential impact on team functioning is worked out and discussed with simultaneous consideration of the characteristics of the team task. Three industrial examples are included to illustrate the importance of including worker, team, and work characteristics when designing manufacturing cells. © 2006 Wiley Periodicals, Inc. Hum Factors Man 16: 1–15, 2006. 相似文献
64.
Pope Kenneth S.; Tabachnick Barbara G.; Keith-Spiegel Patricia 《Canadian Metallurgical Quarterly》1987,42(11):993
There is an absence of comprehensive, systematically gathered data concerning psychologists' beliefs about and compliance with ethical principles. Furthermore, we know little about which resources are valued as effective in guiding appropriate behavior. Survey data were collected from 456 APA Division 29 members regarding the degree to which they engaged in each of 83 behaviors and the degree to which they considered each behavior to be ethical. These data were categorized and examined in terms of five principles derived from the Hippocratic oath (avoiding harm, competence, avoiding exploitation, respect, and confidentiality) as well as two additional principles (informed consent; social equity and justice). Twelve of the behaviors were very difficult for participants to evaluate on the basis of ethics. Seven of the 83 behaviors were practiced by over 90% of the participants; 16 by fewer than 10%. Colleagues, the APA Ethical Principles, and internship training were rated as the most helpful resources in guiding behavior; state and federal laws, published research, and local ethics committees were rated least helpful. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
Kenneth Train 《Energy》1985,10(12):1243-1253
66.
Previous research indicates that tobacco craving predicts relapse to smoking among adult smokers attempting to quit. We hypothesized a similar relationship between craving and lapse (any smoking following a period of abstinence) among adolescent smokers during the treatment phase of a clinical trial. A visit was considered a lapse visit if the participant reported smoking or had a carbon monoxide level of 7 ppm or greater subsequent to an abstinent visit. A total of 34 participants (mean age = 14.9 years [SD = 1.3]; mean cigarettes/day = 18.0 [SD = 7.6]; mean Fagerstr?m Test for Nicotine Dependence score = 6.8 [SD = 1.34]; 65% female), were included in the present analysis of 167 treatment visits. Logistic regression analyses showed a positive relationship between degree of craving, measured by the Questionnaire on Smoking Urges, and lapse during smoking cessation treatment (p = .013). Additionally, linear regression analyses demonstrated a strong positive association between cigarettes smoked per day and craving scores (p<.001). Taken together with other data, these findings suggest that degree of craving might influence tobacco abstinence for adolescent smokers. Thus monitoring and addressing craving appears useful to increase the success of adolescent smoking cessation. 相似文献
67.
The behavioral response (e.g. changes in indoor temperatures, attention to window and door openings) to residential technical efficiency improvements (e.g. attic insulation, storm windows) is an important and largely unresolved issue. Although there is considerable discussion concerning the extent to which households take back some of the energy savings due to technical efficiency improvements in increased comfort, there is almost no empirical evidence on the subject.Detailed electricity billing data (from mid-1981 to mid-1983) were analyzed for 79 households that received financial assistance from the Bonneville Power Administration to retrofit their homes in mid-1982. The mean retrofit expenditure in these homes was $1900; the mean reduction in annual electricity use was 4700 kWh, of which 83% was due to reductions in space heating electricity use. Analysis of the electricity billing data suggests that these households increased their indoor temperature settings after retrofit by almost 1 °F on average. This temperature increase led to an estimated average loss of almost 600 kWh of electricity saving. In other words, roughly 10% of the energy saving due to retrofit was taken back in terms of increased comfort. These results concerning changes in indoor temperatures should be viewed cautiously because of limitations in the analytical method and the large variation across households. 相似文献
68.
A framework for incorporating uncertainty in risk management is developed and applied to two aspects of decision making: meeting standards or safety goals, and cost-benefit criteria. The framework is applied to several case studies including toxic chemicals in water, failure of civil engineering structures and nuclear power plants. The framework proposes that decisions be based on a level of confidence, in addition to comparing best estimate or point values with standards and goals. 相似文献
69.
This article reports the results of a study conducted to examine the ability of the Situational Outlook Questionnaire (SOQTM) to effectively discern climates that either encourage or discourage creativity and the ability to initiate change in a team setting. The purpose of the study is to examine the concurrent criterion–related validity of the SOQ. The article explores the characteristics in an organisational climate that promote teamwork and some of the tripwires one needs to be aware of in the formation and management of teams. Nine dimensions of the climate for creativity and change as measured by the Situational Outlook Questionnaire are put forward and defined in relation to teams. The methodology and results of the study are reported. The results show that when subjects (N7equals;154) complete the SOQ based on their recollection of a best– and worst–case team experience, the measure is able to consistently and significantly discriminate between the two types of experiences. Conclusions, implications, and areas for future research to further examine the validity of the SOQ are explored. 相似文献
70.
Rainwater collection as a possible water source in developing countries is introduced. The major parameters in calculating the size of the tank are defined. Six methods that have been used previously to relate demand, storage, reliability and the rainfall pattern are compared to the Ottawa Model over a wide range of demands. 相似文献