全文获取类型
收费全文 | 902篇 |
免费 | 81篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 288篇 |
金属工艺 | 18篇 |
机械仪表 | 20篇 |
建筑科学 | 40篇 |
矿业工程 | 4篇 |
能源动力 | 21篇 |
轻工业 | 207篇 |
水利工程 | 16篇 |
石油天然气 | 5篇 |
无线电 | 43篇 |
一般工业技术 | 145篇 |
冶金工业 | 89篇 |
原子能技术 | 1篇 |
自动化技术 | 84篇 |
出版年
2024年 | 6篇 |
2023年 | 13篇 |
2022年 | 15篇 |
2021年 | 67篇 |
2020年 | 31篇 |
2019年 | 45篇 |
2018年 | 37篇 |
2017年 | 26篇 |
2016年 | 36篇 |
2015年 | 27篇 |
2014年 | 39篇 |
2013年 | 82篇 |
2012年 | 77篇 |
2011年 | 86篇 |
2010年 | 40篇 |
2009年 | 44篇 |
2008年 | 48篇 |
2007年 | 43篇 |
2006年 | 32篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有983条查询结果,搜索用时 156 毫秒
91.
Phillips VJ St Louis VL Cooke CA Vinebrooke RD Hobbs WO 《Environmental science & technology》2011,45(6):2042-2047
We reconstructed historical trends in mercury (Hg) accumulation over the past ~ 150 years in nine western Canadian alpine lakes. Recent Hg accumulation rates (fluxes) ranged between ~ 7 and 75 μg m(-2) yr(-1), which were an average of 1.8 times higher than preindustrial (i.e., pre-1850) fluxes. Increased Hg fluxes in these lakes were less than at lower elevation sites, showing that despite the potential for increased deposition, alpine lakes are no more susceptible to Hg accumulation. Unlike other studies, we found that geographic setting, changes in chlorophyll-inferred algal production, and climate were not significant predictors of [Hg] or Hg flux in lakes. Instead, our findings highlight how a combination of atmospheric deposition and site-specific processes, including organic matter supply and catchment weathering, better explain sequestration of Hg in alpine lakes. 相似文献
92.
Sean Sweetnam Thomas SöderströmFranz-Josef Haug Oscar CuberoXavier Niquille Vanessa Terrazzoni-DaudrixChristophe Ballif 《Thin solid films》2011,519(16):5567-5570
We study the effects of a-Si:H and μc-Si:H covering layers and an H2 treatment on the characteristics of μc-Si:H thin film solar cells deposited in open single chamber very high frequency plasma enhanced chemical vapor deposition systems. Secondary ion mass spectrometry is used to evaluate the phosphor concentration in the μc-Si:H material. Compared to use of an a-Si:H covering layer, use of a μc-Si:H covering layer reduces dopant contamination by a relative 50%, and improves efficiency by a relative 6%, and use of an H2 treatment reduces dopant contamination by a relative 64%, and improves efficiency by a relative 17%. 相似文献
93.
The individual response of saline lakes to a severe drought 总被引:1,自引:0,他引:1
Tweed S Grace M Leblanc M Cartwright I Smithyman D 《The Science of the total environment》2011,409(19):3919-3933
A severe protracted drought between 1997 and 2009 has altered the physical and chemical hydrology of a series of lakes in the Corangamite Basin of southeast Australia. Leading up to the drying out of most lakes (many for the first time on record), we document the changes in lakes' water quantity (water levels and inundation), salinity (Cl concentrations), salinity processes (Cl/Br ratios), nutrient concentrations and ratios (ammonia, phosphate and NOx (nitrate and nitrite)) and algae (as chlorophyll-a) for six lakes. All lakes show record declines in inundated areas and increases in salinity from pre-drought (< 1997) to drought conditions. However, the magnitude of change in salinity varies for different lakes, and there is no systematic change in the controls on lake salinity processes. Four lakes show no change in salinity processes, one lake shows the beginnings of change; where halite dissolution reactions increased closer to the time of the lake drying up, and another lake shows a marked shift from predominantly evaporation to the cyclic dissolution and precipitation of halite. Changes in filterable reactive phosphorus (FRP) values and lake N and P limitation predictions also showed little systematic correlation with changes in lake salinity, and nutrient values varied between lakes and over time. The decline in NOx concentrations in lakes where electrical conductivity (EC) values were above 100 mS/cm indicates some correlation with changes in salinity. Largely, these lakes exhibit individual changes in water quality parameters and salinity processes in response to the drought, indicating that while the stress of drought is regional, the hydrochemical response is local. In future changing climates, these results suggest that the catchment adaption strategies will require comprehensive plans for individual lake systems. 相似文献
94.
Photo‐Induced Functionalization of Spherical and Planar Surfaces via Caged Thioaldehyde End‐Functional Polymers 下载免费PDF全文
Michael Kaupp Alexander S. Quick Cesar Rodriguez‐Emmenegger Alexander Welle Vanessa Trouillet Ognen Pop‐Georgievski Martin Wegener Christopher Barner‐Kowollik 《Advanced functional materials》2014,24(36):5649-5661
The synthesis and application of a novel reversible addition‐fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λmax = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol?1 ≤ Mn ≤ 15 000 g mol?1; 1.07 ≤ ? ≤ 1.20) with excellent end‐group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels–Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene‐reactive polymeric microspheres. The grafted particles are in‐depth characterized via scanning electron microscopy, elemental analysis, X‐ray photoelectron spectroscopy, and high resolution FT‐IR microscopy, leading to a qualitative as well as quantitative image of the core–shell objects. Grafting densities up to 0.10 molecules nm?2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)‐coated glass slides and silicon wafers via two‐photon direct laser writing (DLW) imaged by ToF‐SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub‐micrometer resolution. 相似文献
95.
96.
R Guesde B Barrou I Leblanc S Ourahma JP Goarin P Coriat B Riou 《Canadian Metallurgical Quarterly》1998,352(9135):1178-1181
BACKGROUND: Diabetes insipidus is common among brain-dead donors and may lead to decreased graft function. The use of desmopressin to limit the consequences of diabetes insipidus is controversial. We assessed the effects of desmopressin administered to brain-dead donors on early and long-term graft function in kidney recipients. METHODS: In a randomised controlled study, 97 brain-dead donors received desmopressin as 1 microg bolus every 2 h when diuresis was more than 300 mL/h (desmopressin group n=49) or no desmopressin (control group n=48). In 175 kidney recipients (controls n=89, desmopressin group n=86) we measured serum concentrations of creatinine and haemodialysis requirements to assess early renal function in the first 15 days after transplantation. We assessed long-term results of transplantation (median time 45 months) for a homogeneous subgroup of 95 recipients (48 in the desmopressin group). FINDINGS: We found no significant differences between the two groups of brain-dead donors, except for final diuresis, which was lower in the desmopressin group than among controls. Haemodialysis requirement in controls and the desmopressin group (20 vs 23%, p=0.63) and serum creatinine concentrations (decrease from 903 micromol/L to 206 micromol/L vs 814 micromol/L to 193 micromol/L, p=0.14) did not differ significantly in the first 15 days after transplantation. Long-term graft survival was similar in the two groups (88 vs 87%). INTERPRETATION: Desmopressin can be given to brain-dead donors to limit the harmful effects of diabetes insipidus without any substantial effects to graft function in recipients. 相似文献
97.
S Ta?eb V Cabaret F Bonodeau E Leblanc P Besson 《Canadian Metallurgical Quarterly》1998,22(6):896-898
PURPOSE: The aim of this study was the assessment of atresia formation after syngeneic fetal small bowel transplantation (SBTx) to clarify its pathogenesis. METHODS: Seventy Lewis rat fetuses (gestational age, 18 to 19 days) were obtained by hysterotomy, and a 30-mm long section of small bowel was excised from each fetus. Each bowel graft was then transplanted into the space between the peritoneum and the rectus abdominis in 70 adult Lewis rats to expose the grafts to ischemic stress. Transplantation was successful in 63 of 70 grafts (90%). Successfully transplanted bowel grafts were harvested for macroscopic and microscopic examination 10 days posttransplantation. RESULTS: Of the successfully transplanted grafts, only two (3%) were atresia free; 127 atretic segments were found in the remaining 61 grafts. Twenty-four grafts (38%) had a single atresia comprised of membranous stenosis (MS) in two, membranous atresia (MA) in 10, and blind ends (BEs) with or without a connecting tissue remnant in 12. Thirty-seven grafts (59%) had multiple atresias, comprised of MS, MA, or both in six, BEs alone in seven, and a combination of BEs with MS or MA in 24. CONCLUSIONS: Our model is the first to succeed in inducing experimentally membranous stenosis and a high incidence (59%) of multiple atresias. These results suggest that bowel ischemia is responsible for multiple bowel atresia formation. 相似文献
98.
A methodology for developing product platforms in the specific setting of the housebuilding industry 总被引:1,自引:1,他引:0
Vanessa S. Veenstra Johannes I. M. Halman Johannes T. Voordijk 《Research in Engineering Design》2006,17(3):157-173
Platform based strategies have proved to be a successful approach for achieving optimum balances between standardization and variation in many industries. However, application of this concept in the housebuilding industry is relatively new. This article describes a new methodology for developing product platform architectures in the specific setting of the housebuilding industry. This methodology comprises a reference framework describing the basic elements that constitutes a product platform, supported by a protocol for developing product platforms. The applicability of the proposed methodology has been tested at a Dutch housebuilding company. In this study, the methodology demonstrated its added value in determining which modules to standardize and defining a product platform. This article also describes a distinctive method of housing classification that is based on the spatial use of houses. Compared to the traditional classification system based on technical construction elements, the proposed new classification system facilitates a better translation of functional requirements into technical specifications. 相似文献
99.
Tsang H.K. Grant R.S. Penty R.V. White I.H. Soole J.B.D. Colas E. Leblanc H.P. Andreadakis N.C. Kim M.S. Sibbett W. 《Electronics letters》1991,27(22):1993-1995
The first measurements of selfphase modulation and nonlinear absorption in a GaAs/GaAlAs multiquantum well (MQW) waveguide near the half-bandgap resonance are reported. An intensity-dependent refractive index coefficient n/sub 2/ of 9*10/sup -14/ cm/sup 2//W and a two-photon absorption coefficient of 0.15 cm/Gw at 1.55 mu m wavelength for TM light were obtained. This corresponds to an intensity-independent figure of merit of 24 rad phase change in one nonlinear absorption length, high enough to allow the implementation of subpicosecond all-optical switches at 1.55 mu m wavelength.<> 相似文献
100.
Y Leblanc 《Canadian Metallurgical Quarterly》1989,39(12):3731-3744