全文获取类型
收费全文 | 3424篇 |
免费 | 115篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 442篇 |
金属工艺 | 32篇 |
机械仪表 | 54篇 |
建筑科学 | 49篇 |
矿业工程 | 3篇 |
能源动力 | 40篇 |
轻工业 | 313篇 |
水利工程 | 29篇 |
石油天然气 | 16篇 |
无线电 | 84篇 |
一般工业技术 | 230篇 |
冶金工业 | 2052篇 |
原子能技术 | 16篇 |
自动化技术 | 164篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 54篇 |
2021年 | 64篇 |
2020年 | 56篇 |
2019年 | 73篇 |
2018年 | 62篇 |
2017年 | 57篇 |
2016年 | 63篇 |
2015年 | 41篇 |
2014年 | 74篇 |
2013年 | 137篇 |
2012年 | 89篇 |
2011年 | 93篇 |
2010年 | 71篇 |
2009年 | 81篇 |
2008年 | 72篇 |
2007年 | 53篇 |
2006年 | 38篇 |
2005年 | 29篇 |
2004年 | 32篇 |
2003年 | 27篇 |
2002年 | 35篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 67篇 |
1998年 | 657篇 |
1997年 | 344篇 |
1996年 | 229篇 |
1995年 | 156篇 |
1994年 | 134篇 |
1993年 | 140篇 |
1992年 | 34篇 |
1991年 | 33篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 24篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 24篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 31篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 46篇 |
1976年 | 102篇 |
1975年 | 6篇 |
1968年 | 3篇 |
排序方式: 共有3541条查询结果,搜索用时 15 毫秒
91.
Davies BL Rodriguez y Baena FM Barrett AR Gomes MP Harris SJ Jakopec M Cobb JP 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2007,221(1):71-80
A brief history of robotic systems in knee arthroplasty is provided. The place of autonomous robots is then discussed and compared to more recent 'hands-on' robotic systems that can be more cost effective. The case is made for robotic systems to have a clear justification, with improved benefits compared to those from cheaper navigation systems. A number of more recent, smaller, robot systems for knee arthroplasty are also described. A specific example is given of an active constraint medical robot, the ACROBOT system, used in a prospective randomized controlled trial of unicondylar robotic knee arthroplasty in which the robot was compared to conventional surgery. The results of the trial are presented together with a discussion of the need for measures of accuracy to be introduced so that the efficacy of the robotic surgery can be immediately identified, rather than have to wait for a number of years before long-term clinical improvements can be demonstrated. 相似文献
92.
AD Gouliamos DS Kontogiannis J Androulidakis AE Kalovidouris LJ Vlahos CG Papavasiliou 《Canadian Metallurgical Quarterly》1993,17(3):446-448
The MR studies of three histologically proven spinal neurilemmomas and neurofibromas were reviewed retrospectively. There were two benign neurilemmomas (schwannomas) and one neurofibroma. The common characteristic of these cases was a central low intensity focus ("dot") seen on postcontrast T1-weighted imaging. The low intensity foci corresponded histologically to a congeries of changes including edema, microcysts, foam cells, hyalinization of blood vessels, old hemorrhage, and dystrophic calcification. 相似文献
93.
It is emphasized that, under certain conditions, the frequency dependences of the real and imaginary parts of an electrical impedance are correlated by the Kramers-Kronig relations. The importance of these relations in electrochemistry is illustrated by the examples of certain electrochemical impedance types. Some misapprehensions appearing in the electrochemical literature are pointed out. 相似文献
94.
Decision support system to divide a large network into suitable District Metered Areas 总被引:2,自引:0,他引:2
This paper presents a new approach to divide large Water Distribution Networks (WDN) into suitable District Metered Areas (DMAs). It uses a hydraulic simulator and two operational models to identify the optimal number of DMAs, their entry points and boundary valves, and the network reinforcement/replacement needs throughout the project plan. The first model divides the WDN into suitable DMAs based on graph theory concepts and some user-defined criteria. The second model uses a simulated annealing algorithm to identify the optimal number and location of entry points and boundary valves, and the pipes reinforcement/replacement, necessary to meet the velocity and pressure requirements. The objective function is the difference between the economic benefits in terms of water loss reduction (arising from the average pressure reduction) and the cost of implementing the DMAs. To illustrate the proposed methodology, the results from a hypothetical case study are presented and discussed. 相似文献
95.
AD Lelianov IuG Novikov GA Rusanov NE Siniavskaia 《Canadian Metallurgical Quarterly》1976,116(4):24-28
In experiments on 50 dogs with toxic acute edema of the lung, induced with intravenous injection of 0.1% silver nitrate, the authors have studied the efficacy of accessory artificial circulation and "conservative" therapy. During the perfusion a discharge of the right portions, adequate extracorporeal gas metabolism, normalization of blood gas and acid-base balance were noted; an intensity of pulmonary edema is descreased. An intensive therapy for pulmonary edema was found to be more effective in association of "conservative" treatment with venoarterial perfusion and blood oxygenation. 相似文献
96.
Nitrous oxide produced a dose-related "analgesia" in mice (median effective dose, 55 percent). The analgesia was evaluated by means of a phenylquinone writhing test. Narcotic antagonists or chronic morphinization reduced nitrous oxide analgesia. Either nitrous oxide releases an endogenous analgesic or narcotic antagonists have analgesic antagonist properties heretofore unappreciated. 相似文献
97.
A New Distribution System Reconfiguration Approach Using Optimum Power Flow and Sensitivity Analysis for Loss Reduction 总被引:2,自引:0,他引:2
Gomes F.V. Carneiro S. Jr. Pereira J.L.R. Vinagre M.P. Garcia P.A.N. De Araujo L.R. 《Power Systems, IEEE Transactions on》2006,21(4):1616-1623
This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented 相似文献
98.
Single carriageway multilane roads are not, in general, a very safe type of road, mainly because of the high number of seriously injured victims in head-on collisions, when compared with dual carriageway multilane roads, with a median barrier. 相似文献
99.
M. A. Sellitto M. Borchardt G. M. Pereira L. P. Gomes 《Theoretical Foundations of Chemical Engineering》2012,46(6):691-703
This paper presents a method for assessing environmental performance in industrial operations. The method was applied to three logistical operations in an industrial supply chain performed by a single operator: road transportation, warehousing, and urban transportation. Environmental performance was treated as a complex object and was structured according to the following five criteria: atmospheric emissions, liquid effluents, solid waste, natural and energy resources, and managerial and legal regulations. The first four criteria address a direct impact on the environment, whereas the last is a necessary condition for the first four to have a satisfactory performance. Six experts in environmental management prioritized the criteria and defined sets of indicators for the field appraisal. The indicators were expected to be correlated for the same criteria. The validity of the indicators was assessed through questionnaires answered by six managers of the operation. Finally, three overall indices corresponding to the environmental performance of the three logistical operations were calculated for the operations and were found to be 73.58, 79.21, and 76.28% (higher is better). These indicate good results because the maximum performance is expected to be 100%. This environmental performance assessment can aid in reformulating the environmental strategies embedded in the operational strategy of the company. 相似文献
100.
Francieli Tiecher Denise Carpena Coitinho Dal Molin Márcia Elisa Boscato Gomes Nicole Pagan Hasparyk Paulo José Meleragno Monteiro 《Cement and Concrete Composites》2012,34(10):1130-1140
Mesostasis material present in the interstices of volcanic rocks is the main cause of the alkali-aggregate reaction (AAR) in concretes made with these rock aggregates. Mesostasis often is referred to as volcanic glass, because it has amorphous features when analyzed by optical microscopy. However, this study demonstrates that mesostasis in the interstitials of volcanic rocks most often consists of micro to cryptocrystalline mineral phases of quartz, feldspars, and clays. Mesostasis has been identified as having different characteristics, and, thus, this new characterization calls for a re-evaluation of their influence on the reactivity of the volcanic rocks. The main purpose of this study is to correlate the characteristics of mesostasis with the AAR in mortar bars containing basalts and rhyolites. 相似文献