全文获取类型
收费全文 | 7212篇 |
免费 | 296篇 |
国内免费 | 93篇 |
专业分类
电工技术 | 250篇 |
综合类 | 112篇 |
化学工业 | 972篇 |
金属工艺 | 142篇 |
机械仪表 | 171篇 |
建筑科学 | 241篇 |
矿业工程 | 96篇 |
能源动力 | 122篇 |
轻工业 | 585篇 |
水利工程 | 87篇 |
石油天然气 | 50篇 |
武器工业 | 53篇 |
无线电 | 602篇 |
一般工业技术 | 785篇 |
冶金工业 | 2690篇 |
原子能技术 | 76篇 |
自动化技术 | 567篇 |
出版年
2022年 | 36篇 |
2021年 | 82篇 |
2020年 | 68篇 |
2019年 | 73篇 |
2018年 | 82篇 |
2017年 | 91篇 |
2016年 | 101篇 |
2015年 | 109篇 |
2014年 | 154篇 |
2013年 | 259篇 |
2012年 | 217篇 |
2011年 | 286篇 |
2010年 | 231篇 |
2009年 | 197篇 |
2008年 | 260篇 |
2007年 | 263篇 |
2006年 | 234篇 |
2005年 | 194篇 |
2004年 | 165篇 |
2003年 | 119篇 |
2002年 | 137篇 |
2001年 | 119篇 |
2000年 | 124篇 |
1999年 | 142篇 |
1998年 | 815篇 |
1997年 | 477篇 |
1996年 | 320篇 |
1995年 | 187篇 |
1994年 | 185篇 |
1993年 | 199篇 |
1992年 | 93篇 |
1991年 | 80篇 |
1990年 | 87篇 |
1989年 | 97篇 |
1988年 | 73篇 |
1987年 | 100篇 |
1986年 | 57篇 |
1985年 | 87篇 |
1984年 | 65篇 |
1983年 | 56篇 |
1982年 | 67篇 |
1981年 | 58篇 |
1980年 | 66篇 |
1979年 | 40篇 |
1978年 | 56篇 |
1977年 | 94篇 |
1976年 | 197篇 |
1975年 | 39篇 |
1974年 | 38篇 |
1972年 | 34篇 |
排序方式: 共有7601条查询结果,搜索用时 20 毫秒
1.
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
2.
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
3.
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
4.
IH Bjerkli R Myklebust S R?is?nen S Telimaa LE Stenfors 《Canadian Metallurgical Quarterly》1996,36(3):205-213
Dopaminergic agents and carbidopa/levodopa have become the preferred treatment for both the restless legs (RL) syndrome and for periodic limb movements in sleep (PLMS). For once-nightly treatments with carbidopa/ levodopa, a problem with morning end-of-dose rebound increases in leg movements has been reported to occur in the about one-fourth of the patients. In our clinical studies a previously unreported but far more significant problem of markedly augmented RL symptoms occurred in the afternoon and the evening prior to taking the next nightly dose. A systematic prospective evaluation of this augmentation in 46 consecutive patients treated with carbidopa/ levodopa for RL syndrome or PLMS disorder found this augmentation to be the major adverse effect of treatment. Augmentation occurred for 31% of PLMS patients and 82% of all RL patients. It was greater for subjects with more severe RL symptoms and for patients on higher doses (> or = 50/200 mg carbidopa/levodopa) but was unrelated to gender, age or baseline severity of PLMS. This augmentation was severe enough to require medication change for 50% of the RL patients and 13% of PLMS patients. Augmentation resolved with cessation of the medication and could be minimized by keeping the dose low. 相似文献
5.
Recurrent erosion of the corneal epithelium has been treated successfully by phototherapeutic keratectomy when convention therapy has failed. We present a case of recurrent corneal erosion occurring 1 year after photorefractive keratectomy in a 55-year-old myopic woman. No corneal abnormalities were previously identified in either the affected or the fellow eye. This case demonstrates the potential for ineffective healing of the corneal epithelial basement membrane complex after excimer laser photorefractive keratectomy. 相似文献
6.
7.
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
8.
LE Lindner 《Canadian Metallurgical Quarterly》1993,41(3):439-445
The silver-staining technique for nucleolar organizer regions (AgNOR) of Ploton et al., as popularized by Crocker, is being widely used for evaluation of nucleolar function, especially in neoplasia. It suffers from limited reliability, background staining, precipitates, and fading of the sections. Factors were identified that affect these problems. The oxidation-reduction level and gelatin used are particularly important. An improved procedure is presented which incorporates pre-reduction of the sections, selection of an optimal gelatin, and post-treatment of the sections to produce a permanent preparation. It is compatible with many fixatives and with other stains used before or after the silver stain. 相似文献
9.
D Averill D Blockus B Brabson J Brom C Jung H Ogren DR Rust M Derrick P Kooijman JS Loos B Musgrave LE Price J Repond K Sugano B Cork C Akerlof J Chapman D Errede MT Ken DI Meyer H Neal D Nitz R Thun R Tschirhart S Abachi P Baringer BG Bylsma R DeBonte D Koltick EH Low RL McIlwain DH Miller CR Ng EI Shibata 《Canadian Metallurgical Quarterly》1989,39(1):123-137
10.