全文获取类型
收费全文 | 1270篇 |
免费 | 35篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 174篇 |
金属工艺 | 22篇 |
机械仪表 | 24篇 |
建筑科学 | 53篇 |
矿业工程 | 4篇 |
能源动力 | 26篇 |
轻工业 | 181篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 152篇 |
一般工业技术 | 132篇 |
冶金工业 | 358篇 |
原子能技术 | 12篇 |
自动化技术 | 140篇 |
出版年
2023年 | 6篇 |
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 19篇 |
2017年 | 22篇 |
2016年 | 16篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 43篇 |
2012年 | 42篇 |
2011年 | 68篇 |
2010年 | 53篇 |
2009年 | 40篇 |
2008年 | 43篇 |
2007年 | 45篇 |
2006年 | 50篇 |
2005年 | 28篇 |
2004年 | 33篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 30篇 |
1998年 | 99篇 |
1997年 | 64篇 |
1996年 | 53篇 |
1995年 | 32篇 |
1994年 | 24篇 |
1993年 | 47篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 15篇 |
1976年 | 20篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有1307条查询结果,搜索用时 15 毫秒
31.
Sea-air flux of CO2 in the Caribbean Sea estimated using in situ and remote sensing data 总被引:2,自引:0,他引:2
Empirical relationships between sea surface carbon dioxide fugacity (fCO2sw) and sea surface temperature (SST) were applied to datasets of remotely sensed SST to create fCO2sw fields in the Caribbean Sea. SST datasets from different sensors were used, as well as the SST fields created by optimum interpolation of bias corrected AVHRR data. Empirical relationships were derived using shipboard fCO2sw data, in situ SST data, and SST data from the remote sensing platforms. The results show that the application of a relationship based on shipboard SST data, on fields of remotely sensed SST yields biased fCO2sw values. This bias is reduced if the fCO2sw-SST relationships are derived using the same SST data that are used to create the SST fields. The fCO2sw fields found to best reproduce observed fCO2sw are used in combination with wind speed data from QuikSCAT to create weekly maps of the sea-air CO2 flux in the Caribbean Sea in 2002. The region to the SW of Cuba was a source of CO2 to the atmosphere throughout 2002, and the region to the NE was a sink during winter and spring and a source during summer and fall. The net uptake of CO2 in the region was doubled when potential skin layer effects on fCO2sw were taken into account. 相似文献
32.
Shreesha Rao D.S Mikkel Jensen Lars Grüner-Nielsen Jesper Toft Olsen Peter Heiduschka Bj?rn Kemper Jürgen Schnekenburger Martin Glud Mette Mogensen Niels M?ller Israelsen Ole Bang 《光:科学与应用(英文版)》2021,10(7):1372-1384
We present the first demonstration of shot-noise limited supercontinuum-based spectral domain optical coherence tomography (SD-OCT) with an axial resolution of ... 相似文献
33.
34.
Zhenping Liu Alberto Passalacqua Michael G. Olsen Rodney O. Fox James C. Hill 《American Institute of Chemical Engineers》2016,62(7):2570-2578
The multi‐inlet vortex reactor (MIVR) is used for flash nanoprecipitation to manufacture functional nanoparticles. A validated computational fluid dynamics model is needed for the design, scale‐up, and optimization of the MIVR. Unfortunately, available Reynolds‐averaged Navier‐Stokes methods are unable to accurately model the highly swirling flow in the MIVR. Large‐eddy simulations (LES) are also problematic, as excessively fine grids are required to accurately model this flow. These dilemmas led to the application of the dynamic delayed detached eddy simulation (DDES) method to the MIVR. In the dynamic DDES model, the eddy viscosity has a form similar to the Smagorinsky sub‐grid viscosity in LES, which allows the implementation of a dynamic procedure to determine its model coefficient. Simulation results using the dynamic DDES model are found to match well with experimental data in terms of mean velocity and turbulence intensity, suggesting that the dynamic DDES model is a good option for modeling the turbulent swirling flow in the MIVR. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2570–2578, 2016 相似文献
35.
Albert?Camós Noguer Stefan?M?ller?Olsen S?ren?Hvilsted S?ren?KiilEmail author 《Journal of Coatings Technology and Research》2016,13(4):567-575
Poly(ethylene glycol) (PEG) is a hydrophilic polymer that has been extensively used in the biomedical and marine environment due to its antifouling properties. In the biomedical field, PEG has been successfully used to functionalize surfaces due to its resistance to cell and nonspecific protein adsorption. However, the long-term stability of PEG has limited its use in some areas. In the shipping industry, there is a great need for long-term solutions to keep the hulls of the ships fouling-free. The long-term stability of PEG in polydimethylsiloxane (PDMS) fouling-release coatings is studied here, in both accelerated laboratory tests and real seawater conditions. This article shows how PEG-based copolymers, which have been exposed in fouling-release coatings to real-life seawater conditions, are isolated and compared to those exposed to accelerated laboratory testing with successful results. The influence of the chemistry of the PEG compounds, the chosen laboratory degrading agents, and the possible degradation pathways and products are discussed. 相似文献
36.
37.
Ragni Ofstad Bjrg Egelandsdal Siw Kidman Reidar Myklebust Ragnar L Olsen Anne-Marie Hermansson 《Journal of the science of food and agriculture》1996,71(3):301-312
This study was performed in order to assess the effect of early post mortem structural changes in the muscle upon the liquid-holding capacity of wild cod, net-pen-fed cod (fed cod) and farmed salmon. The liquid-holding capacity was measured by a low speed centrifugation test. Transmission electron microscopy was used to discover ultrastructural changes both in the connective tissue and in the myofibrils. Differential scanning calorimetric thermograms of the muscle proteins were recorded to elucidate whether fundamental differences did exist between the proteins of the raw material tested. Multivariate statistics were used to explicate the main tendencies of variations in the thermograms. The salmon muscle possessed much better liquid-holding properties than the cod muscle, and wild cod better than fed cod regardless of the storage time. Both fed cod and farmed salmon, underwent the most severe structural alterations, probably caused by the low muscle pH values. The higher liquid-holding capacity of the salmon muscle was related to species specific structural features and better stability of the muscle proteins. The myofibrils of the salmon muscle were denser and intra- and extracellular spaces were filled by fat and a granulated material. The differences in thermograms of muscle from wild and fed cod were largely explained by the variations in pH. The severe liquid loss of fed cod is due to a low pH induced denaturation and shrinkage of the myofibrils. Post mortem degradation of the endomysial layer and the sarcolemma may have further facilitated the release of liquid. 相似文献
38.
Poly(para-xylylene)(PPX)/carbon fiber towpregs were produced by two different in-situ polymerization processes: Electrochemcal polymerization (ECP) and vapor deposition polymerization (VDP). The monomer used for the ECP process was α, α′ -dibromo-para-xylylene and di-para-xylylene was the starting material for the VDP process. A series of tests, including FTIR, WAXD, DSC, TG, and SEM were carried out to identify and compare these two composite towpregs. It has been confirmed that the PPX samples obtained by the two different polymerization processes were basically chemically identical. However, the polymer coating on the fiber surface produced by the VDP process was much smoother than that produced by the ECP process, which produced a porous coating. 相似文献
39.
Hoelzer K Sauders BD Sanchez MD Olsen PT Pickett MM Mangione KJ Rice DH Corby J Stich S Fortes ED Roof SE Grohn YT Wiedmann M Oliver HF 《Journal of food protection》2011,74(7):1083-1095
Despite growing concerns about cross-contamination of ready-to-eat foods with Listeria monocytogenes, our knowledge about the ecology and transmission of L. monocytogenes in retail establishments has remained limited. We conducted a cross-sectional study to characterize the prevalence, distribution, and subtype diversity of L. monocytogenes in 120 New York State retail deli establishments that were hypothesized to present an increased risk for environmental L. monocytogenes contamination (i.e., small establishments and establishments with a history of failed New York State Agriculture and Markets inspections). Analysis of these data along with previously reported data for 121 predominantly larger retail establishments in New York State identified establishment size, geographic location, and inspection history as significant predictors of L. monocytogenes presence and prevalence. The odds of an establishment being L. monocytogenes positive were approximately twice as high for large establishments, establishments located in New York City, or establishments with poor inspection history (as compared with establishments without these attributes), even though correlation between location and inspection history complicated interpretation of results. Within an establishment, L. monocytogenes was significantly more prevalent on nonfood contact surfaces than on food contact surfaces; prevalence was particularly high for floors and in floor drains, sinks, the dairy case, and milk crates. L. monocytogenes subtype diversity differed between sites, with lineage I isolates significantly associated with nonfood contact surfaces and lineage II isolates significantly associated with food contact surfaces. Isolates belonging to the same ribotype were often found dispersed across multiple sites within an operation. 相似文献
40.
Precombustion chambers (PCCs) are an ignition technology for large bore, natural gas engines enabling increased combustion stability while extending the lean limit of operation. A PCC is a small chamber, typically 1–2% of the clearance volume, in which a near-stoichiometric mixture of fuel and air is ignited by a standard spark plug. After the mixture in the PCC is ignited, its pressure rises and expels a flame jet of hot gas mixture into the main chamber. The amount of energy a typical PCC produces is roughly one million times that of a conventional spark plug. In this work the role that the PCC plays in the formation of oxides of nitrogen (NOx) is investigated. Previous research indicates that the PCC is responsible for a significant part of engine-out NOx, especially near the lean limit of engine operation. Experimental results are presented from a large bore lean-burn 2-stroke cycle engine. The data shows that the PCC is responsible for a significant part of engine-out NOx emissions. However, the PCC NOx does not form in the PCC. Rather it forms within the gas jet after it penetrates into the main chamber combustion gases. 相似文献