全文获取类型
收费全文 | 462篇 |
免费 | 7篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 49篇 |
金属工艺 | 6篇 |
机械仪表 | 7篇 |
建筑科学 | 36篇 |
能源动力 | 15篇 |
轻工业 | 53篇 |
水利工程 | 9篇 |
无线电 | 35篇 |
一般工业技术 | 27篇 |
冶金工业 | 163篇 |
自动化技术 | 64篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 9篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 17篇 |
1998年 | 51篇 |
1997年 | 49篇 |
1996年 | 21篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有469条查询结果,搜索用时 15 毫秒
31.
Elaine Sterrett Isely Paul Isely Saichon Seedang Kenneth Mulder Kurt Thompson Alan D. Steinman 《Journal of Great Lakes research》2010
Land use change is profoundly influencing the environmental resources of the Great Lakes region. In West Michigan, population growth and rapid land use change have resulted in urbanization and a loss in the diversity of green infrastructure that provides a variety of benefits–ecosystem services–to regional residents and visitors. To address these changes in land use and cover in ways that are objective, transparent, and defensible, local policy makers need tools to help inform local and regional land use decisions. An interdisciplinary team, engaged by a regional policy organization, developed one such online tool, the INtegrated Valuation of Ecosystem Services Tool (INVEST). INVEST utilizes static GIS maps, graphs, and tables, to help educate local and regional decision-makers about the underlying values of ecosystem services associated with green infrastructure, particularly those services that do not pass through traditional commercial markets. In this article we provide a general overview of the development of INVEST and examine its current application as an educational tool, including the specific challenges associated with addressing the information gaps. 相似文献
32.
Atmospheric deposition of nitrogen at five subtropical forested sites in South China 总被引:5,自引:0,他引:5
Elevated concentrations of reactive nitrogen (N) in precipitation have been reported for many cities in China. Due to increased use of fossil fuels and expansion in agriculture, further increases in deposition of ammonia (NHx) and reactive N oxides (NOy) are predicted. Increased deposition of reactive N is likely to affect N dynamics and N runoff in forest ecosystems. Yet, in China little work has been done to quantify the levels of atmospheric N deposition in such systems. Here, we assess the deposition of inorganic N (ammonium, NH4+ and nitrate, NO3-) for five subtropical forest ecosystems in remote and urban areas of South China. Annual volume-weighted concentrations in bulk precipitation range from 0.18 to 1.55 mg NH4+ -N L(-1) and from 0.12 to 0.74 mg NO3- -N L(-1). These values are large and several times greater than those reported for remote sites of the world. The fluxes of total inorganic N (TIN) in wet-only deposition range from 0.8 to 2.3 g N m(-2) yr(-1), with NH4+ -N contributing 54% to 77%. Both the tree canopy and the ground vegetation layer are important in determining the net N flux reaching the forest floor, but the net effect varies from site to site. At TieShanPing (TSP), close to Chongqing city, and at CaiJiaTang (CJT), near Shaoshan (Hunan province), the canopy represents a net source of N, probably due to dry deposition. At the other three sites (LiuChongGuan (LCG), LeiGongShan (LGS), both in Guizhou province, and LiuXiHe (LXH) in Guangdong), a net loss of reactive N from precipitation water occurs in the canopy, probably due to uptake processes. The total annual atmospheric TIN load is estimated to range from at least 0.8 g N m(-2) yr(-1) to 4.0 g N m(-2) yr(-1), with a considerable contribution from dry deposition. Concentrations and fluxes of inorganic N in tree canopy throughfall are greater than those in North America. Also the contribution of NH4+ -N to TIN fluxes in throughfall (40% to 70%) is greater than in North America. Our sites have N deposition levels and NH4+ -N contributions similar to those found in Northwest and central Europe. The TIN loads at TSP and CJT far exceed 2.5 g N m(-2) yr(-1), which is the N deposition load above which NO3- leaching is expected in temperate and boreal forests. 相似文献
33.
Mg attracts much research interest as anode material for Ni-MH batteries thanks to its lightweight, cost-effectiveness and high theoretical capacity (2200 mA h g?1). However, its practical application is tremendously challenged by the poor hydrogen sorption kinetics, passivation from aggressive aqueous electrolytes, and insulating nature of MgH2. Mg-based alloys exhibit enhanced hydrogen sorption kinetics and electrical conductivity, but significant amount of costly transition metal elements are required. In this work, we have, for the first time, utilized non-alloyed but catalyzed Mg as anode for Ni-MH batteries. 5 mol.% TiF3 was added to nanosized Mg for accelerating the hydrogen sorption kinetics. Several strategies for preventing the problematic passivation of Mg have been studied, including protective encapsulation of the electrode and utilizing room-temperature/high-temperature ionic liquids and an alkaline polymer membrane as working electrolyte. Promising electrochemical performance has been achieved in this Mg–TiF3 composite anode based Ni-MH batteries with room for further improvements. 相似文献
34.
35.
van de Schoot Rens; Hoijtink Herbert; Mulder Joris; Van Aken Marcel A. G.; Orobio de Castro Bram; Meeus Wim; Romeijn Jan-Willem 《Canadian Metallurgical Quarterly》2011,47(1):203
Researchers often have expectations about the research outcomes in regard to inequality constraints between, e.g., group means. Consider the example of researchers who investigated the effects of inducing a negative emotional state in aggressive boys. It was expected that highly aggressive boys would, on average, score higher on aggressive responses toward other peers than moderately aggressive boys, who would in turn score higher than nonaggressive boys. In most cases, null hypothesis testing is used to evaluate such hypotheses. We show, however, that hypotheses formulated using inequality constraints between the group means are generally not evaluated properly. The wrong hypotheses are tested, i.e.. the null hypothesis that group means are equal. In this article, we propose an innovative solution to these above-mentioned issues using Bayesian model selection, which we illustrate using a case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
KT Koch JJ Piek RJ de Winter K Mulder GK David KI Lie 《Canadian Metallurgical Quarterly》1997,80(8):1084-1086
The safety and feasibility of early ambulation was evaluated prospectively in 907 patients undergoing elective coronary angioplasty and stenting with the use of 6Fr guiding catheters, low-dose heparin (5,000 IU), and immediate postprocedural sheath removal by comparing ambulation after 4 hours with immobilization for at least 12 hours. Because no excess in puncture site complications (2.3% vs 2.2%) could be demonstrated after 4-hour ambulation, it is concluded that early ambulation after 6Fr guiding catheter angioplasty by the femoral route with low-dose heparin is feasible, safe, and may facilitate a shorter hospital stay. 相似文献
37.
Mulder J. Ward C.M. Chi-Hung Lin Kruse D. Westra J.R. Lugthart M. Arslan E. van de Plassche R.J. Bult K. van der Goes F.M.L. 《Solid-State Circuits, IEEE Journal of》2004,39(12):2116-2125
This paper presents an 8-b two-step subranging analog-to-digital (ADC) using interpolation, averaging, offset compensation, and pipelining techniques to accomplish an effective number of bits of 7.6 b at 125 MSample/s. The 0.13-/spl mu/m CMOS ADC occupies 0.09 mm/sup 2/ and consumes 21 mW. 相似文献
38.
RM Hoetelmans RP van Heeswijk M Profijt JW Mulder PL Meenhorst JM Lange P Reiss JH Beijnen 《Canadian Metallurgical Quarterly》1998,12(17):F211-F216
OBJECTIVE: To compare the plasma pharmacokinetics of didanosine during once daily (qd) and twice daily (bid) dosing. DESIGN: Open-label, randomized, cross-over study. METHODS: HIV-1 infected patients who used didanosine were randomized to either a qd or a bid dosing regimen of didanosine. The total daily dose of didanosine was identical in both regimens. Seven days after the start of the study, the pharmacokinetic profile of didanosine in plasma and urine was assessed during an 8-h period. The next day, the patient was switched to the opposite dosing regimen, and after another 7 days, the study was concluded by again assessing the plasma and urine pharmacokinetics of didanosine during 8 h. RESULTS: A total of 19 patients completed the study. The pharmacokinetics of didanosine in plasma (with maximum plasma concentration adjusted for dose) and urine were not significantly different in the qd and bid dosing regimen (P > 0.28 for all parameters). CONCLUSION: We conclude that qd dosing of didanosine leads to a similar exposure in plasma as bid dosing (using the same total daily dose). Since qd dosing may lead to improved compliance of patients to regimens containing didanosine, these results provide a rationale for prescribing didanosine in a qd regimen, and is reassuring when we realize that the drug is being administered in a qd dosing regimen on a large scale in clinical practice. 相似文献
39.
Vreugdenhil Hestien J. I.; Mulder Paul G. H.; Emmen Harry H.; Weisglas-Kuperus Nynke 《Canadian Metallurgical Quarterly》2004,18(1):185
PCBs are known for their neurotoxic properties, especially on the developing brain. To increase insight into the neurotoxic effects of PCB exposure, the authors studied the effects of perinatal exposure to environmental levels of these compounds on different neuropsychological domains. In 9-year-old children of the Rotterdam PCB--dioxin cohort, higher prenatal PCB levels were associated with longer response times (RTs), more variation in RTs, and lower scores on the Tower of London (TOL; Shallice, 1982). A longer breast-feeding duration was associated with lower TOL scores and with better spatial organizational skills. There was some evidence of negative effects of lactational exposure to PCBs on scores on the TOL. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
J.-M. Duval A. J. B. Kemperman B. Folkers M. H. V. Mulder G. Desgrandchamps C. A. Smolders 《应用聚合物科学杂志》1994,54(4):409-418
The incorporation of zeolite particles in the micrometer range into polymeric matrices was investigated as a way to improve the gas separation properties of the polymer materials used in the form of membranes. The adhesion between the polymer phase and the external surface of the particles appeared to be a major problem in the preparation of such membranes when the polymer is in the glassy state at room temperature. Various methods were investigated to improve the internal membrane structure, that is, surface modification of the zeolite external surface, preparation above the glass-transition temperature, and heat treatment. Improved structures were obtained as observed by scanning electron microscopy, but the influence on the gas separation properties was not in agreement with the observed structural improvements. © 1994 John Wiley & Sons, Inc. 相似文献