全文获取类型
收费全文 | 5218篇 |
免费 | 129篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 62篇 |
综合类 | 1篇 |
化学工业 | 986篇 |
金属工艺 | 60篇 |
机械仪表 | 76篇 |
建筑科学 | 139篇 |
矿业工程 | 64篇 |
能源动力 | 100篇 |
轻工业 | 400篇 |
水利工程 | 38篇 |
石油天然气 | 6篇 |
无线电 | 497篇 |
一般工业技术 | 800篇 |
冶金工业 | 1648篇 |
原子能技术 | 48篇 |
自动化技术 | 430篇 |
出版年
2021年 | 38篇 |
2020年 | 35篇 |
2019年 | 51篇 |
2018年 | 63篇 |
2017年 | 67篇 |
2016年 | 62篇 |
2015年 | 56篇 |
2014年 | 91篇 |
2013年 | 204篇 |
2012年 | 114篇 |
2011年 | 185篇 |
2010年 | 127篇 |
2009年 | 127篇 |
2008年 | 165篇 |
2007年 | 152篇 |
2006年 | 137篇 |
2005年 | 139篇 |
2004年 | 110篇 |
2003年 | 102篇 |
2002年 | 109篇 |
2001年 | 80篇 |
2000年 | 108篇 |
1999年 | 113篇 |
1998年 | 448篇 |
1997年 | 264篇 |
1996年 | 181篇 |
1995年 | 128篇 |
1994年 | 126篇 |
1993年 | 120篇 |
1992年 | 86篇 |
1991年 | 66篇 |
1990年 | 82篇 |
1989年 | 94篇 |
1988年 | 63篇 |
1987年 | 89篇 |
1986年 | 59篇 |
1985年 | 79篇 |
1984年 | 73篇 |
1983年 | 78篇 |
1982年 | 74篇 |
1981年 | 60篇 |
1980年 | 57篇 |
1979年 | 55篇 |
1978年 | 62篇 |
1977年 | 76篇 |
1976年 | 105篇 |
1975年 | 45篇 |
1974年 | 46篇 |
1972年 | 43篇 |
1971年 | 32篇 |
排序方式: 共有5355条查询结果,搜索用时 31 毫秒
1.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
2.
3.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献
4.
Alan Bivens Rashim Gupta Ingo McLean Boleslaw Szymanski Jerome White 《International Journal of Network Management》2004,14(2):131-146
Rapid growth of computer network sizes and uses necessitate analysis of network application middleware in terms of its scalability as well as performance. In this paper we analyze a distributed network management middleware based on agents that can be dispatched to locations where they can execute close to the managed nodes. The described middleware operates between the network protocol layer and the application layer and uses standard TCP protocol and SNMP probes to interface the network. By aggregating requests from many users into a single agent, our system allows multiple managers to probe problem areas with minimal management traffic overhead. We discuss and quantify the benefits of the described middleware by implementing real‐time network managers using our system. The main result of this paper is a comparison of scalability and efficiency of our agent‐based management middleware and traditional SNMP‐based data collection. To this end, we measured traffic in both real and simulated networks. In the latter case, we designed, used and described here a method of separating simulated application flow into separate subflows to simplify design of simulations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
5.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
6.
Dual command travel times and miniload system throughput with turnover-based storage 总被引:2,自引:0,他引:2
Byung Chun Park Robert D. Foley John A. White Edward H. Frazelle 《IIE Transactions》2003,35(4):343-355
We analyze travel times for automated storage/retrieval systems. In particular, we apply our travel time model to turnover-based storage systems and determine the mean and variance of dual command travel times. We present detailed numerical results for selected rack shape factors and ABC inventory profiles. We then investigate the effect of alternative rack configurations on travel time performance measures. We also show how to determine the throughput of miniload systems with turnover-based storage and exponentially distributed pick times. 相似文献
7.
Albrecht Jason E.; O'Brien Edward J.; Mason Robert A.; Myers Jerome L. 《Canadian Metallurgical Quarterly》1995,21(2):364
An implicit assumption of several causal reasoning models is that readers adopt the goals of a narrative's protagonist during text comprehension. In apparent violation of this assumption, readers participating in Experiment 1 of the present study drew inferences relevant to a protagonist's goal even when that goal was already satisfied from the perspective of the protagonist. In Experiments 2 and 3, participants were explicitly asked to view the text situation from the point of view of the protagonist. In this case, the goals of the reader and the protagonist should be the same. In these experiments, participants focused on the goals of the protagonist only when those goals had not been satisfied from the perspective of the protagonist. These results are discussed in terms of reader- and character-based perspectives and in terms of text characteristics that cue perspective taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
Twenty-six patients with an intracardiac myxoma underwent surgical resection at our institution from 1977 through 1992. Left atrial myxoma was diagnosed in 22 patients, left ventricular in 1, right atrial in 2, and right ventricular in 1. Six patients were asymptomatic; preoperative symptoms included dyspnea, arrhythmias, embolic episodes, and syncope. The diagnosis was established with transthoracic echocardiography in all cases but one. Surgery was performed in all cases with the aid of cardiopulmonary bypass with moderate hypothermia and cold crystalloid cardioplegia. One patient with a left ventricular myxoma died in a comatose state during the immediate postoperative period. Long-term clinical and echocardiographic evaluation was performed in 19 patients; results were excellent (all the patients were in New York Heart Association functional class I or II), and no recurrences were documented. The clinical characteristics, diagnostic methods, and surgical approach are presented and discussed. 相似文献
10.