全文获取类型
收费全文 | 5228篇 |
免费 | 389篇 |
国内免费 | 18篇 |
学科分类
工业技术 | 5635篇 |
出版年
2023年 | 55篇 |
2022年 | 35篇 |
2021年 | 136篇 |
2020年 | 144篇 |
2019年 | 147篇 |
2018年 | 173篇 |
2017年 | 162篇 |
2016年 | 188篇 |
2015年 | 141篇 |
2014年 | 236篇 |
2013年 | 334篇 |
2012年 | 394篇 |
2011年 | 492篇 |
2010年 | 311篇 |
2009年 | 270篇 |
2008年 | 349篇 |
2007年 | 311篇 |
2006年 | 259篇 |
2005年 | 212篇 |
2004年 | 172篇 |
2003年 | 137篇 |
2002年 | 153篇 |
2001年 | 95篇 |
2000年 | 58篇 |
1999年 | 49篇 |
1998年 | 81篇 |
1997年 | 62篇 |
1996年 | 59篇 |
1995年 | 40篇 |
1994年 | 37篇 |
1993年 | 37篇 |
1992年 | 29篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有5635条查询结果,搜索用时 15 毫秒
1.
In response to the growing interest in offshore wind energy development in California, the U.S. Bureau of Ocean Energy Management delineated three Call Areas for potential leasing. This study provides a comprehensive characterization and comparison of offshore wind power potential within the two Central California Call Areas (Diablo Canyon and Morro Bay) using 12- and 15-MW turbines under different inter-turbine spacing and wind farm size scenarios. Our analysis shows similar daily and seasonal patterns of wind power produced within the Call Areas, which peak in spring and during evening hours. Per-turbine power production is higher in the Morro Bay Call Area due to slightly higher hub-height wind speeds, whereas total power production is higher in the Diablo Canyon Call Area due to its larger size. Turbine type had a negligible impact on average power production per-unit-area because while larger turbines produce more power, they require greater inter-turbine spacing. Combined power production from the two fully built out Call Areas could equal nearly a quarter of California's current annual electrical energy production. A commercial-scale wind farm with a realized power output of 960 MW would require a footprint of at least half of the Morro Bay Call Area or at least a quarter of the Diablo Canyon Call Area. These results provide guidance on offshore wind development over the Central California Coast, and the framework demonstrated here could be applied to other wind data sets in other regions. 相似文献
2.
Mauro Zammarano John R. Shields Isaac Leventon Ickchan Kim Shonali Nazare Andre Thompson Rick D. Davis Artur Chernovsky Matthew Bundy 《火与材料》2021,45(1):114-126
Herein, we describe a reduced‐scale test (“Cube” test), measuring the fire performance of specimens including a fire barrier (FB) and a flammable core material, which acts as the main fuel load. The specimen is intended to reproduce a cross‐section of a composite product where heat/mass transfer occurs primarily in a direction perpendicular to the FB. The Cube test procedure and benefits are discussed in this work by adopting residential upholstery furniture as an exemplary study. One flexible polyurethane foam, one polypropylene cover fabric, and 10 commercially available FBs were selected. They were used to compare the fire performance of FBs, measured in terms of peak of heat release rate, in the ASTM E1474‐14 standard test and the newly developed Cube test. Edge effects severely affected the performance of FBs in the ASTM E1474‐14 standard test but not in the Cube test. Furthermore, appropriate test conditions were determined in the Cube test to measure the so‐called “wetting point,” that is, the time and value of heat release rate measured when flammable liquid products were first observed on the bottom of the specimen. The relevance of the “wetting point” in terms of full‐scale fire performance and failure mechanism of FBs is discussed. 相似文献
3.
Dr. Sven Nerdinger Eugene Kuatsjah Dr. Timothy E. Hurst Inge Schlapp‐Hackl Prof. Dr. Volker Kahlenberg Prof. Dr. Klaus Wurst Prof. Dr. Lindsay D. Eltis Prof. Dr. Victor Snieckus 《Chembiochem : a European journal of chemical biology》2018,19(16):1771-1778
A series of alkylated 2,3‐dihydroxybiphenyls has been prepared on the gram scale by using an effective Directed ortho Metalation–Suzuki–Miyaura cross‐coupling strategy. These compounds have been used to investigate the substrate specificity of the meta‐cleavage dioxygenase BphC, a key enzyme in the microbial catabolism of biphenyl. Isolation and characterization of the meta‐cleavage products will allow further study of related processes, including the catabolism of lignin‐derived biphenyls. 相似文献
4.
Ryan C. Rettinger Matthew Porter Jeffrey Canaria James L. Smith Jimmie C. Oxley 《Journal of Energetic Materials》2020,38(2):170-190
ABSTRACTImprovised explosive may be as primitive as a fuel and oxidizer mixture; yet not all fuel-oxidizer mixtures are explosive. Predicting explosive potential from laboratory-scale tests is desirable to screen a large matrix of potential threats in varying concentrations. Herein the properties of various fuel/oxidizer mixtures were measured at small scale (2 g) with bomb calorimetry and on large scale (5 kg) with high speed photography for detonation velocity and with piezoelectric pressure probes for TNT air blast equivalence. Potassium nitrate (KN), potassium chlorate (KC), potassium permanganate (KMnO4), potassium iodate (KIO3), ammonium nitrate (AN), and ammonium perchlorate (AP) were prepared with sucrose (Su) and aluminum (Al) fuel. Results were compared to each other as well as predictions from Cheetah thermochemical code. 相似文献
5.
Antimicrobial effects of pulsed electromagnetic fields from commercially available water treatment devices – controlled studies under static and flow conditions 下载免费PDF全文
6.
Zachary Welsh Matthew J. Simpson Md Imran H. Khan M. A. Karim 《Comprehensive Reviews in Food Science and Food Safety》2018,17(5):1293-1308
Plant‐based food materials are mostly porous in nature and heterogeneous in structure with huge diversity in cellular orientation. Different cellular environments of plant‐based food materials, such as intercellular, intracellular, and cell wall environments, hold different proportions of water with different characteristics. Due to this structural heterogeneity, it is very difficult to understand the drying process and associated morphological changes during drying. Transport processes and morphological changes that take place during drying are mainly governed by the characteristics of and the changes in the cells. Therefore, to predict the actual heat and mass transfer process that occurs in the drying process and associated morphological changes, development of multiscale modeling is crucial. Multiscale modeling is a powerful approach with the ability to incorporate this cellular structural heterogeneity with microscale heat and mass transfer during drying. However, due to the huge complexity involved in developing such a model for plant‐based food materials, the studies regarding this issue are very limited. Therefore, we aim in this article to develop a critical conceptual understanding of multiscale modeling frameworks for heterogeneous food materials through an extensive literature review. We present a critical review on the multiscale model formulation and solution techniques with their spatial and temporal coupling options. Food structure, scale definition, and the current status of multiscale modeling are also presented, along with other key factors that are critical to understanding and developing an accurate multiscale framework. We conclude by presenting the main challenges for developing an accurate multiscale modeling framework for food drying. 相似文献
7.
8.
Di Hu Aleksei Dolganov Mingchan Ma Biyash Bhattacharya Matthew T. Bishop George Z. Chen 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(2):129-137
The Kroll process has been employed for titanium extraction since the 1950s. It is a labour and energy intensive multi-step semi-batch process. The post-extraction processes for making the raw titanium into alloys and products are also excessive, including multiple remelting steps. Invented in the late 1990s, the Fray-Farthing-Chen (FFC) Cambridge process extracts titanium from solid oxides at lower energy consumption via electrochemical reduction in molten salts. Its ability to produce alloys and powders, while retaining the cathode shape also promises energy and material efficient manufacturing. Focusing on titanium and its alloys, this article reviews the recent development of the FFC-Cambridge process in two aspects, (1) resource and process sustainability and (2) advanced post-extraction processing. 相似文献
9.
Performance improvement being a major need of the power sector aims at increasing efficiency, lowering air pollutants and ultimately cost. This paper explores a quadruple cycle, a hybrid of solid oxide fuel cell integrated with gas turbine, steam turbine and organic Rankine cycle totaling four cycles (SOFC-GT-ST-ORC), fueled primarily by natural gas for stationary power generation. A mathematical model of the configuration of the quadruple cycle is developed and the performance investigated through a parametric study of the thermodynamic components. The power output, efficiency and other results were validated with those found in literature. The quadruple cycle produced an efficiency of 66.1% with 1,1,1,2-tetrafluoroethane, R134a as the organic working fluid. This efficiency exceeded the performance of traditional thermodynamic cycles like single steam cycle, combined and triple cycle at similar operating conditions. Lastly, the quadruple cycle presents a potential for optimization with waste heat recovery. 相似文献
10.
Michael E. Sierszen Lee S. Schoen Jessica M. Kosiara Joel C. Hoffman Matthew J. Cooper Donald G. Uzarski 《Journal of Great Lakes research》2019,45(1):129-137
Hydrologic linkages among coastal wetland and nearshore areas allow coastal fish to move among the habitats, which has led to a variety of habitat use patterns. We determined nutritional support of coastal fishes from 12 wetland-nearshore habitat pairs using stable isotope analyses, which revealed differences among species and systems in multi-habitat use. Substantial (proportions?>?0.30) nutrition often came from the habitat other than that in which fish were captured. Nearshore subsidies to coastal wetlands indicate wetlands are not exclusively exporters of energy and materials; rather, there is reciprocity in the mutual energetic support of nearshore and wetland food webs. Coastal wetland hydrogeomorphology influenced the amount of multi-habitat use by coastal fishes. Fishes from systems with relatively open interfaces between wetland and nearshore habitats exhibited less nutritional reliance on the habitat in which they were captured, and higher use of resources from the adjacent habitat. Comparisons of stable isotope analyses of nutrition with otolith analyses of occupancy indicated nutritional sources often corresponded with habitat occupancy; however, disparities among place of capture, otolith analyses, and nutritional analyses indicated differences in the types of support those analyses inform. Disparities between occupancy information and nutritional information can stem from movements for support functions other than foraging. Together, occupancy information from otolith microchemistry and nutritional information from stable isotope analyses provide complementary measures of the use of multiple habitats by mobile consumers. This work underscores the importance of protecting or restoring a diversity of coastal habitats and the hydrologic linkages among them. 相似文献