全文获取类型
收费全文 | 1493篇 |
免费 | 100篇 |
国内免费 | 105篇 |
专业分类
电工技术 | 9篇 |
综合类 | 41篇 |
化学工业 | 73篇 |
金属工艺 | 23篇 |
机械仪表 | 16篇 |
建筑科学 | 167篇 |
矿业工程 | 19篇 |
能源动力 | 60篇 |
轻工业 | 167篇 |
水利工程 | 118篇 |
石油天然气 | 627篇 |
武器工业 | 5篇 |
无线电 | 62篇 |
一般工业技术 | 64篇 |
冶金工业 | 31篇 |
原子能技术 | 27篇 |
自动化技术 | 189篇 |
出版年
2023年 | 15篇 |
2022年 | 37篇 |
2021年 | 39篇 |
2020年 | 46篇 |
2019年 | 51篇 |
2018年 | 51篇 |
2017年 | 46篇 |
2016年 | 57篇 |
2015年 | 60篇 |
2014年 | 65篇 |
2013年 | 108篇 |
2012年 | 96篇 |
2011年 | 141篇 |
2010年 | 115篇 |
2009年 | 87篇 |
2008年 | 58篇 |
2007年 | 99篇 |
2006年 | 77篇 |
2005年 | 74篇 |
2004年 | 62篇 |
2003年 | 61篇 |
2002年 | 31篇 |
2001年 | 37篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 33篇 |
1997年 | 18篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1989年 | 9篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1698条查询结果,搜索用时 687 毫秒
61.
George A. Sorial Albert D. Venosa Karen M. Koran Edith Holder Dennis W. King 《Canadian Metallurgical Quarterly》2004,130(10):1073-1084
The current U.S. Environmental Protection Agency protocol for testing the effectiveness of dispersants, the swirling flask test, has been found to give widely varying results in the hands of different testing laboratories. The sources of the ambiguities in the test were determined by considering several options in a rigorous systematic fashion. Options considered were variability among three operators and the variability and limitations of three analytical instruments in establishing a calibration curve for oil/dispersant mixtures. Other options included flask type, impact of operational variables (rotational speed, mixing time, settling time, and oil:dispersant ratio), development of a revised procedure for dispersant effectiveness, reproducibility and repeatability of the revised procedure, and development of selection criteria for screening of dispersants. A redesign of the test flask, which is characterized by having baffles with a stopcock at the bottom for sample collection, was deemed necessary to accomplish reproducibility within operator and between operators. The results indicated that the baffled flask provided a total coefficient of variation (variations within operator and between operators) less than 11% compared to above 100% in some cases for the swirling flask. 相似文献
62.
George A. Sorial Albert D. Venosa Karen M. Koran Edith Holder Dennis W. King 《Canadian Metallurgical Quarterly》2004,130(10):1085-1093
The current U.S. Environmental Protection Agency (EPA) protocol for testing the effectiveness of dispersants for use in treating oil spills on the open water, the swirling flask test (SFT), has been found to give widely varying results in the hands of different testing laboratories. Part I addressed the sources of the ambiguities in the EPA SFT and the development of a new test referred to as the baffled flask test (BFT). In this part of the series, further experiments were conducted for estimating the repeatability of three operators in determining the effectiveness of 18 dispersants by both the EPA SFT and the BFT methods. Overall statistical analysis of the results indicated that the coefficient of variation by the BFT was only 7.8% compared to 21.9% for the EPA SFT. The mean percent effectiveness of the EPA SFT was only 19.7% as compared to 64.6% for the BFT. Proposed selection criteria for screening of dispersants for listing on the National Contingency Plan Product Schedule have been developed. 相似文献
63.
A negotiation support system for resolving an international trans-boundary natural resource conflict
Post-Soviet legal governance regime of Caspian Sea – the largest inland body of water on earth – remains a source of conflict among the five coastal states of Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. Although different division methods have been suggested for sharing the sea and its valuable resources, the actual gain of the countries is unclear as the proposed methods focus either on the oil and gas or the areal share of the parties. The Caspian Sea Negotiation Support System (Caspian Sea NSS) is developed in this study to delineate optimal boundaries for sharing the sea through simultaneous consideration of the countries' areal and resource shares under different sharing methods. This NSS is a complex optimization model, with a solver engine that provides reliable results with a reasonable computational effort using a heuristic method. The model is run under different division scenarios to evaluate the sensitivity of each party's gain and locations of nautical boundaries to the division rules and the economic values of the resources. Results show a high sensitivity of the optimal nautical boundaries to the division rules and an indirect relationship between the allocated area and resource shares. The findings highlight the necessity for considering utility shares in negotiations as opposed to adopting areal division rules which ignore the utilities and might result in unfair resource allocation. The main policy implication of the study is that clarification of the countries' resource and areal gain under any suggested legal regime for governing the Caspian Sea is essential to the success of the negotiations. 相似文献
64.
65.
Yanchao Wang Wei SuCuiyu Zhang Changhu XueYaoguang Chang Xiaolin WuQingjuan Tang Jingfeng Wang 《Food chemistry》2012
Sea cucumber is a nutritional aquatic food that is widely consumed in East Asian countries. Employing a rat model of ethanol-induced gastric ulcer, we examined the protective effect of sea cucumber fucoidan (SC-FUC) extracted from Acaudina molpadioides and explored the related mechanisms. Oral administration with 100 mg/kg body weight SC-FUC for 5 days can significantly prevent the formation of gastric ulcer. Moreover, SC-FUC pretreatment could alleviate ethanol-induced histological damage, reverse changes in tissue oxidation and antioxidase activities, and regulate the signalling pathways of mitogen-activated protein kinases and matrix metalloproteinases. This study investigated the ethanol-induced gastric ulcer protective effect of SC-FUC for the first time, and elucidated that the protective mechanisms included anti-oxidation, gastric matrix hydrolysis suppression, and anti-inflammation. 相似文献
66.
Maurizio Masci Teresina Nevigato 《Food Additives and Contaminants: Part B: Surveillance Communications》2016,9(3):159-169
A sampling campaign from 21 sites in Italy was conducted: 15 species from fishery and three species from aquaculture, for a total of 40 determinations, were considered. A careful sample preparation preceded the instrumental analysis that was carried out by means of GC–ECD and GC–MS. Good laboratory practice was achieved by the participation in proficiency tests, by the use of certified reference materials and by applying other directives recommended by international organisations. Concentrations measured in this work were compared with a TDI proposed by some international bodies: for a person weighing 70 kg one-third of the samples from fishery, when consumed, lead to exceed this TDI if the average fish daily consumption per capita is considered. Based on the data obtained here some hypotheses on environmental spreading and influence of PCBs on human health are made. Some suggestions about the preparation of fish for consumption are also given. 相似文献
67.
Soo-Yeong ParkHee Kyoung Lim Seogjae LeeHyeong Cheol Hwang Somi K. ChoMoonjae Cho 《Food chemistry》2012,132(1):487-492
Pepsin-solubilised collagen (PSC) from Red Sea cucumber (Stichopus japonicus) was studied with respect to its wound-healing effects on a human keratinocyte (HaCaT) cell line. Disaggregated collagen fibres were treated with 0.1 M NaOH for 24 h and digested with pepsin for 72 h to reach maximum yield of 26.6%. The results of an in vitro wound-healing test showed that migration of HaCaT cells was 1.5-fold faster on PSC-coated plates than on untreated plates. The migration rate of sea cucumber PSC was similar to that of rat PSC, but five times higher than that of bovine gelatin. HaCaT cells grown on PSC-coated plates revealed increased fibronectin synthesis (6-fold and 3-fold compared to gelatin and rat PSC, respectively). Additionally, sea cucumber PSCs induced HaCaT cell proliferation by decreasing the G1 phase by 5% and maintaining a larger population (8%) of cells in mitosis. Collagen from Red Sea cucumber might be useful as an alternative to mammalian collagen in the nutraceutical and pharmaceutical industries. 相似文献
68.
渤海海域辽西构造带S型走滑转换带特征及控藏作用定量表征 总被引:1,自引:0,他引:1
S型走滑转换带是走滑环境下广泛发育的一类构造。以往的研究认识多集中在对走滑转换带类型划分的探讨上,缺乏对其控藏作用的精细研究。本次研究利用渤海海域辽东湾地区连片三维地震资料,结合油气田实例,运用统计学方法分析了辽西构造带S型走滑转换带的控藏作用。辽西带新生代构造变形总体表现为NE向伸展构造系统和NNE向右旋走滑构造系统的叠加构造变形,S型走滑转换带可分为增压段和释压段两大类。按照走滑转换带演化阶段的不同,将增压段进一步细分为压扭低凸起段、平缓增压段和强烈增压段等3个亚类。将释压段同样细分为纺锤形浅凹、平缓释压段和菱形释压段等3个亚类。将走滑断裂末端发育的转换带归纳为增压型或释压型马尾扇。应用S型走滑转换带“油气富集指数”的分析方法,论证了S型走滑转换带弯曲度与走滑调节断层活动性具有正相关性,并成功应用于辽西凹陷南次洼旅大5-2北油田成藏分析工作中,为勘探决策提供了定量化依据。 相似文献
69.
Gabriella Di Lena Irene Casini Roberto Caproni Elena Orban 《Food Additives and Contaminants: Part B: Surveillance Communications》2018,11(3):175-182
This study investigated mercury contamination levels in eight commercially valuable crustacean species caught off the Central Adriatic and Tyrrhenian coasts of Italy. Total mercury levels were measured by Thermal Decomposition-Amalgamation-Atomic Absorption Spectrophotometry. Results showed a high variability among species with values ranging from 0.070 to 1.24 (mg kg?1 wet weight). The lowest mercury levels were detected in caramote prawn (Penaeus kerathurus), warty crab (Eriphia verrucosa) and European spider crab (Maja squinado), decapods living in shallow waters. Levels exceeding the limits established by the European Commission were found in species living in close contact with bottom sediments: deepwater rose shrimp (Parapenaeus longirostris), blue and red shrimp (Aristeus antennatus) and Norway lobster (Nephrops norvegicus). For shrimps, the inter-individual variability observed was mostly related to the body size, indicating the accumulation of mercury with age. An estimation of the human intake of mercury associated to the consumption of the crustaceans sampled and its comparison with the Tolerable Weekly Intake are provided. 相似文献
70.
渤海海域浅层油气运移新认识与勘探新进展 总被引:4,自引:3,他引:1
浅层新近系是渤海海域油田储量和产量的主要层系。随着勘探程度的提高,大—中型油气田发现的难度也越来越大。基于渤海海域的勘探实践,结合浅层大—中型油田源外成藏的特性,通过分析油气深层运移与浅层富集的耦合关系,明确了古近系烃源层油气初次、二次运移所形成的"汇聚脊"对其上浅层油气富集、聚集的控制作用,并根据输导体系的组合划分出油气汇聚样式。在"汇聚脊"控藏模式的指导下,渤海海域多个构造带的油气勘探都取得突破,获得一系列亿吨级新发现,由此保证了渤海海域浅层规模优质油气储量持续发现,指导后续勘探进展。 相似文献