全文获取类型
收费全文 | 37676篇 |
免费 | 5597篇 |
国内免费 | 2190篇 |
专业分类
电工技术 | 3559篇 |
技术理论 | 6篇 |
综合类 | 3964篇 |
化学工业 | 4266篇 |
金属工艺 | 1438篇 |
机械仪表 | 2402篇 |
建筑科学 | 5071篇 |
矿业工程 | 2645篇 |
能源动力 | 2328篇 |
轻工业 | 3966篇 |
水利工程 | 3260篇 |
石油天然气 | 2684篇 |
武器工业 | 432篇 |
无线电 | 2237篇 |
一般工业技术 | 2480篇 |
冶金工业 | 2439篇 |
原子能技术 | 382篇 |
自动化技术 | 1904篇 |
出版年
2024年 | 294篇 |
2023年 | 798篇 |
2022年 | 1629篇 |
2021年 | 1896篇 |
2020年 | 1902篇 |
2019年 | 1472篇 |
2018年 | 1235篇 |
2017年 | 1438篇 |
2016年 | 1552篇 |
2015年 | 1622篇 |
2014年 | 2507篇 |
2013年 | 2231篇 |
2012年 | 2772篇 |
2011年 | 2963篇 |
2010年 | 2286篇 |
2009年 | 2267篇 |
2008年 | 1808篇 |
2007年 | 2265篇 |
2006年 | 2017篇 |
2005年 | 1747篇 |
2004年 | 1452篇 |
2003年 | 1285篇 |
2002年 | 1049篇 |
2001年 | 878篇 |
2000年 | 803篇 |
1999年 | 651篇 |
1998年 | 452篇 |
1997年 | 348篇 |
1996年 | 332篇 |
1995年 | 276篇 |
1994年 | 251篇 |
1993年 | 176篇 |
1992年 | 142篇 |
1991年 | 112篇 |
1990年 | 99篇 |
1989年 | 86篇 |
1988年 | 55篇 |
1987年 | 51篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1980年 | 16篇 |
1978年 | 7篇 |
1966年 | 7篇 |
1964年 | 14篇 |
1959年 | 10篇 |
1957年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This study focuses on how to assess the optimal environmental investment decisions under economic and ecological uncertainty, and establishes the continuous time model using the real option approach to optimize environmental pollution policy. Unlike traditional cost benefit analysis, this work extends the model of [Pindyck, R.S., 2002. Optimal timing problems in environmental economics. Journal of Economic Dynamics and Control 26(9–10), 1677–1697], and attempts to identify the storage threshold of pollution stocks and the optimal timing for implementing environmental pollution decisions. 相似文献
92.
93.
94.
95.
介绍工业污染源大气污染物排放连续监测系统的系统结构和应用范围。重点讨论一体化工作站在此系统中实际应用和性能特点。 相似文献
96.
NiTi形状记忆合金激光气体氮化层表面特征 总被引:2,自引:0,他引:2
为改善NiTi合金的表面性能,利用2kW连续波Nd:YAG对NiTi合金进行激光气体氮化处理。采用SEM、TEM、XRD、XPS和纳米压痕研究了氮化层的显微组织及表面特征.结果表明:激光气体氮化可以在NiTi合金表面制备连续、无裂纹、厚度为2μm的TiN表面层,该表面层中基本不合有Ni元素且具有很高的硬度,其纳米压痕硬度为29.28GPa. 相似文献
97.
98.
The operating conditions of this study are close to the typical operating conditions of flue gas desulfurization system in coal-fired power plants. The aim of this study is to investigate the absorption kinetics of SO2 and NO from simulated flue gas into an aqueous solution of acidic sodium chlorite using a bench-scale spraying column. The range of absorption rates measured in this study is between 1.91×10?11 and 9.59×10?10?mol?s?1?cm?2. The range of rate constants measured in this study is between 1.32×107 and 1.21×108?(L?mol?1)1.9?s?1, and the average rate constant is 6.16×107?(L?mol?1)1.9?s?1. The activation energy and frequency factor are 129 Kcal/mol (53.97 KJ/mol) and 6.93×1016?[(L/mol)1.9/s], respectively. 相似文献
99.
This article reports research intended to assess and extend a recent theory of peer responses to low-performing team members (J. A. LePine & L. Van Dyne, 2001a). An instrument that assesses 4 types of peer responses to low performers (compensating for, training, motivating, and rejecting) was developed and then cross-validated in a subsequent study. Results of the study supported the validity of the peer responses measure and were generally consistent with the attributional theory of peer responses. Low-performer characteristics influenced the peer responses. These effects were mediated in part by peer attributions, affect, and cognitions, which explained variance in the peer responses over and above the variance explained by respondents' personality characteristics (i.e., The Big Five). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
100.
Much research has examined gender and age effects on compensation, concluding that a wage gap exists favoring men and negative stereotypes against older workers persist. Although the effect of an employee's gender or age has been widely studied, little work has examined the impact of the demographic characteristics of a focal employee's immediate referent groups (e.g., subordinates, peers, or supervisors) on pay. The effect of the gender and age composition of a focal manager's subordinates, peers, and supervisor on the manager's compensation levels was investigated in a sample of 2,178 managers across a wide range of organizations and functional areas. After controlling for a number of human capital variables, results indicated that not only does a wage gap favoring men exist, but also managerial pay is lower when managers' referent groups are largely female, when subordinates are outside the prime age group, and when peers and supervisors are younger. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献