全文获取类型
收费全文 | 570篇 |
免费 | 18篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 102篇 |
金属工艺 | 8篇 |
机械仪表 | 14篇 |
建筑科学 | 51篇 |
矿业工程 | 3篇 |
能源动力 | 20篇 |
轻工业 | 48篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 50篇 |
一般工业技术 | 129篇 |
冶金工业 | 77篇 |
原子能技术 | 2篇 |
自动化技术 | 73篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 32篇 |
2012年 | 30篇 |
2011年 | 49篇 |
2010年 | 33篇 |
2009年 | 42篇 |
2008年 | 45篇 |
2007年 | 36篇 |
2006年 | 32篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有588条查询结果,搜索用时 15 毫秒
581.
The goal of the study was to assess how protective disposable (Safeskin) and chemical protective (Sol-Vex) nitrile gloves were against Comite emulsifiable concentrate formulation containing propargite (PROP) as active pesticidal ingredient, because there were no explicit recommendations for the gloves that should be worn for hand protection. The glove material was exposed in ASTM-type I-PTC-600 permeation cells at 30.0+/-0.5 degrees C, and gas chromatography-mass spectrometry used for PROP analysis. Aqueous solutions of Comite at 40.4 mg/mL permeated both Safeskin and Sol-Vex nitrile by 8h. Safeskin showed a mean PROP mass permeated of 176+/-27 microg after 8h compared with a mean mass permeated for Sol-Vex of 3.17+/-4.08 microg. Thus, Sol-Vex was about 56 times more protective than Safeskin for an 8-h exposure. However, the kinetics of the permeation revealed that Safeskin can be worn for at least 200 min before disposal. When undiluted Comite challenged both types of nitrile, much faster permeation was observed. Safeskin gloves showed two steady state periods. The first had lag times (t(l)) values of about 1h, although normalized breakthrough times (t(b)) were < 10 min. The second steady state rate (P(s)) was on average four times the rate of the first period, and the second steady state period t(l) was about three times as long as that of the first steady state period, and about the same t(l) as for the aqueous solution. Sol-Vex gloves exposed continuously to undiluted Comite permeated above the normalized breakthrough threshold beyond 2.7h. A risk assessment revealed that the PROP skin permeation rate of 7.1 ng cm(-2)h(-1) was much slower than the first steady state Safeskin glove P(s) of 62,000 ng cm(-2)h(-1). Infrared analysis showed that the glove surfaces were not degraded by the Comite challenge. The chemically protective Sol-Vex gloves protected adequately against undiluted formulation for about 2.7h, whereas they provided protection for nearly 8h when the formulation was diluted with water to the highest concentration for field application. In contrast, the disposable Safeskin gloves did not protect at all for the undiluted formulation, but did for 200 min when the formulation was diluted with water to the highest concentration for spraying. 相似文献
582.
Nisha Naicker Shane A. Norris Angela Mathee 《The Science of the total environment》2010,408(21):4949-4954
Introduction
One of the suggested, yet under-researched, causes of pubertal delay is lead exposure. In South Africa blood lead levels are generally higher than in resource-rich countries. Thus the effects of lead exposure on pubertal development may be significant.Objective
The objective of this study is to determine the association between lead exposure and pubertal development in adolescent females in the Birth to Twenty cohort (Bt20).Methods
Bt20 is a Johannesburg based birth cohort study that commenced in 1990 and includes 1682 girls. At 13 years of age venous blood samples were collected from 725 adolescent female participants for lead content analyses; of these, 712 had menarche data. Pubertal measurement was based on age of menarche and self-reported Tanner staging for pubic hair (n = 684) and breast development (n = 682).Results
The mean blood lead level for the sample was 4.9 μg/dl. Fifty percent had blood lead levels < 5.0 μg/dl, 49% were ≥ 5.0 μg/dl and 1% was > 10.0 μg/dl. The average age of menarche was 12.7 years. At 13 years, 4% and 7% had reached Tanner stage 5 for pubic hair and breast development, respectively. Analyses showed that higher blood lead levels were associated with significant delays in the onset of puberty (p < 0.001).Conclusion
The study found that higher blood lead levels were associated with a delay in the onset of puberty, after adjustment for confounders. Lead exposure in resource-poor countries is generally higher compared to resource-rich countries and thus the effects of high blood levels have personal and public health significance. 相似文献583.
Fate of endocrine-disruptor, pharmaceutical, and personal care product chemicals during simulated drinking water treatment processes 总被引:24,自引:0,他引:24
The potential occurrence of endocrine-disrupting compounds (EDCs) as well as pharmaceuticals and personal care products (PPCPs) in drinking water supplies raises concern over the removal of these compounds by common drinking water treatment processes. Three drinking water supplies were spiked with 10 to 250 ng/L of 62 different EDC/ PPCPs; one model water containing an NOM isolate was spiked with 49 different EDC/PPCPs. Compounds were detected by LC/MS/MS or GC/MS/MS. These test waters were subjected to bench-scale experimentation to simulate individual treatment processes in a water treatment plant (WTP). Aluminum sulfate and ferric chloride coagulants or chemical lime softening removed some polyaromatic hydrocarbons (PAHs) but removed <25% of most other EDC/ PPCPs. Addition of 5 mg/L of powder activated carbon (PAC) with a 4-h contact time removed 50% to >98% of GC/ MS/MS compounds (more volatile) and 10% to >95% of LC/ MS/MS compounds (more polar); higher PAC dosages improved EDC/PPCP removal. EDC/PPCP percentage removal was independent of the initial compound concentration. Octanol-water partition coefficients served as a reasonable indicator of compound removal under controlled PAC test conditions, except for EDC/PPCPs that were protonated or deprotonated at the test pH and some that contained heterocyclic or aromatic nitrogen. Separate chlorine or ozone experiments decreased the EDC/PPCP initial concentration by <10% to >90%; EDC/PPCPs were likely transformed to oxidation byproducts. Ozone oxidized steroids containing phenolic moieties (estradiol, ethynylestradiol, or estrone) more efficiently than those without aromatic or phenolic moieties (androstenedione, progesterone, and testosterone). EDC/PPCP reactivity with oxidants were separated into three general groups: (1) compounds easily oxidized (>80% reacted) by chlorine are always oxidized at least as efficiently by ozone; (2) 6 of the -60 compounds (TCEP, BHC, chlordane, dieldrin, heptachlor epoxide, musk ketone) were poorly oxidized (<20% reacted) by chlorine or ozone; (3) compounds (24 of 60) reacting preferentially (higher removals) with ozone rather than chlorine. Conventional treatment (coagulation plus chlorination) would have low removal of many EDC/PPCPs, while addition of PAC and/or ozone could substantially improve their removals. Existing strategies that predict relative removals of herbicides, pesticides, and other organic pollutants by activated carbon or oxidation can be directly applied for the removal of many EDC/PPCPs, but these strategies need to be modified to account for charged (protonated bases or deprotonated acids) and aliphatic species. Some compounds (e.g., DEET, ibuprofen, gemfibrozil) had low removals unless ozonation was used. Other compounds had low removals by all the WTP processes considered (atrazine, iopromide, meprobamate, TCEP), and removal processes capable of removing these types of compounds should be investigated. 相似文献
584.
Peper S Telting-Diaz M Almond P Albrecht-Schmitt T Bakker E 《Analytical chemistry》2002,74(6):1327-1332
The 2,3,4,5,6,7,8,9,10,1 1,12-undecabromocarborane anion, 1-HCB11Br11- (UBC-) has been evaluated for its suitability as an ion exchanger in solvent polymeric membrane electrodes and bulk optodes. Experiments comparing the chemical stability of the perhalogenated carborane anion to that of the best lipophilic tetraphenylborate, 3,5-[bis(trifluoromethyl)phenyl]borate (TFPB-), demonstrated that in the presence of 0.2 M acetic acid TFPB- was completely lost within 6 h, while the concentration of UBC- decreased by less than 10% in the same time period. Thin-film bulk optodes containing BME-44 as potassium-selective ionophore, ETH 5294 as chromo-ionophore, and UBC- as ionic sites exhibited a K+ response similar to analogous optodes containing TFPB-, with comparable selectivities over Na+ and Ca2+. Potentiometric measurements evaluating the selectivity behavior of UBC- in both ionophore-free and ionophore-containing electrodes were performed. Ionophore-free PVC membranes containing UBC- as ion exchanger and either DOS or NPOE as plasticizer also demonstrated selectivity similar to TFPB--containing membranes. Sodium-selective membranes containing the ionophore 4-tert-butylcalix[4]arenetetraacetic acid tetraethyl ester (sodium ionophore X) and UBC- as ionic sites showed a Nernstian response for sodium and selectivity comparable to that found in analogous electrodes containing TFPB-. 相似文献
585.
Frederick Stern Tao Xing Donald B. Yarbrough Alric Rothmayer Ganesh Rajagopalan Shourya Prakashotta David Caughey Rajesh Bhaskaran Sonya Smith Barbara Hutchings Shane Moeykens 《工程教育杂志》2006,95(1):63-83
This study describes the development, implementation, and evaluation of an effective curriculum for students to learn computational fluid dynamics (CFD) in introductory and intermediate undergraduate and introductory graduate level courses/laboratories. The curriculum is designed for use at different universities with different courses/laboratories, learning objectives, applications, conditions, and exercise notes. The common objective is to teach students from novice to expert users who are well prepared for engineering practice. The study describes a CFD Educational Interface for hands‐on student experience, which mirrors actual engineering practice. The Educational Interface teaches CFD methodology and procedures through a step‐by‐step interactive implementation automating the CFD process. A hierarchical system of predefined active options facilitates use at introductory and intermediate levels, encouraging self‐learning, and eases transition to using industrial CFD codes. An independent evaluation documents successful learning outcomes and confirms the effectiveness of the interface for students in introductory and intermediate fluid mechanics courses. 相似文献
586.
Kai-Hung Yang Parand Riley Keith B. Rodenhausen Shelby A. Skoog Shane J. Stafslien Lyndsi Vanderwal Roger J. Narayan 《International Journal of Applied Ceramic Technology》2022,19(5):2545-2555
Silicon-incorporated diamond-like carbon (Si-DLC), an amorphous material containing Si atoms with sp3- and sp2-hybridized carbon, is a promising biomaterial for versatile biomedical applications due to its excellent mechanical properties, chemical inertness, biocompatibility, and antimicrobial capability. However, the antifungal properties of plasma-treated Si-DLC have not been systematically evaluated. In this study, Si-DLC coatings were deposited by chemical vapor deposition and further treated with either oxygen or fluorine plasma to render the surface anchored with different functional groups and hydrophobicity. Surface roughness was probed with atomic force microscopy, whereas bonding character and surface composition were assessed using Raman and X-ray photoelectron spectroscopy. Wettability and surface charge were investigated via water contact angle and zeta potential measurements. Antifungal assessment was performed using a Candida albicans multi-well plate screening technique and crystal violet biomass quantification. The results demonstrate that oxygen plasma–treated Si-DLC exhibited hydrophilic properties, lower negative zeta potential, and significant antifungal behavior. This material can potentially be applied on surfaces for the prevention of reduced nosocomial infections. 相似文献
587.
Yuan-Wen Hsiao Bi Shane Cheng Hung-Chieh Hsu Shih-Hsiung Wu Hsuan-Ta Wu Ching-Chich Leu Chuan-Feng Shih 《Advanced functional materials》2023,33(21):2300169
This research demonstrates a state-of-the-art vertical-transport photodetector with an n-type 3D MAPbI3/p-type quasi-2D (Q-2D) BA2MA2Pb3I10 perovskite heterojunction. This structure introduces a ≈0.6 V built-in electric field at the n-p junction that greatly improves the characteristics of the perovskite photodetector, and the presence of Q-2D perovskite on the surface improves the life. The electrical polarities of the 3D and the Q-2D perovskite layers are simply controlled by self-constituent doping, making clearly defined n-p characteristics. Doctor-blade coating is used to fabricate the photodetector with a large area. The Q-2D materials with highly oriented (040) Q-2D (n = 2,3) planes are near the surface, and the (111) preferred planes mixed with high index Q-2D materials (n = 4,5) are found near the 3D/Q-2D interface. The stacking and interface are beneficial for carrier extraction and transport, yielding an external quantum efficiency of 77.9%, a carrier lifetime long as 295.7 ns, and a responsibility of 0.41 A W−1. A low dark current density of 6.2 × 10−7 mA cm−2 and a high detectivity of 2.82 × 1013 Jones are obtained. Rise time and fall time are fast as 1.33 and 10.1 µs, respectively. The results show the application potential of 3D/Q-2D n-p junction perovskite photodetectors. 相似文献