全文获取类型
收费全文 | 857篇 |
免费 | 42篇 |
国内免费 | 17篇 |
专业分类
综合类 | 35篇 |
化学工业 | 271篇 |
金属工艺 | 1篇 |
机械仪表 | 43篇 |
建筑科学 | 65篇 |
矿业工程 | 3篇 |
能源动力 | 5篇 |
轻工业 | 376篇 |
水利工程 | 28篇 |
石油天然气 | 9篇 |
无线电 | 6篇 |
一般工业技术 | 54篇 |
冶金工业 | 6篇 |
原子能技术 | 3篇 |
自动化技术 | 11篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 29篇 |
2020年 | 28篇 |
2019年 | 33篇 |
2018年 | 30篇 |
2017年 | 25篇 |
2016年 | 39篇 |
2015年 | 33篇 |
2014年 | 39篇 |
2013年 | 75篇 |
2012年 | 58篇 |
2011年 | 63篇 |
2010年 | 40篇 |
2009年 | 42篇 |
2008年 | 33篇 |
2007年 | 54篇 |
2006年 | 58篇 |
2005年 | 37篇 |
2004年 | 33篇 |
2003年 | 30篇 |
2002年 | 19篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有916条查询结果,搜索用时 15 毫秒
1.
Florence Lacoste Patrick Carré Sylvie Dauguet Catarina Petisca Fernando Campos Daniel Ribera 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2020,37(9):1491-1502
ABSTRACT Processing Factors (PFs) reflect the concentration or dilution of pesticide residues resulting from food processing. PFs are key elements to demonstrate the compliance of processed foods with Maximum residue levels (MRLs) as set by Regulation 396/2005. While efforts have been made by the European Food Safety Authority (EFSA) and by national authorities to compile PFs from processing studies, such PFs are not available for all pesticides/processed product combinations. The EU vegetable oil and proteinmeal industry association (FEDIOL) has therefore developed a theoretical approach to approximate MRLs in crude vegetable oils and fats, based on the partition coefficient (log Pow) of the pesticides and on the oil content of the raw materials. To substantiate this approach, a pilot-scale processing study was initiated with rapeseeds spiked with selected pesticides and the experimental PFs for these pesticides determined. The aims of this study were (i) to study the reliability of pilot-scale conditions for PF determination and (ii) to assess the experimental PFs obtained in comparison to the theoretical PFs proposed by FEDIOL. This study demonstrated that production yields obtained for crude oil and meal in this processing study are similar to those in industrial processes even if differences were observed in the individual production steps (mechanical or solvent extraction steps). The experimental PFs obtained confirmed that the chosen fat-soluble pesticides did concentrate in the oil fraction. For metalaxyl-M having a log Pow lower than 3, a partitioning between the oil and the meal was observed, as expected. By comparing the experimental PFs and theoretical PFs, it can be concluded that the FEDIOL approach can be recommended as a suitable tool when PFs derived from specific processing studies are missing. Similar studies on pesticides with wider ranges of log Pow are required in order to complete our conclusions on default PFs for vegetable oils. 相似文献
2.
结合QuEChERS前处理方法,建立了采用高效液相色谱法(HPLC)测定食品中4种氨基甲酸酯类农药残留的方法。以乙腈作为提取溶剂,无水硫酸镁、PSA和GCB净化,C18柱为色谱分离柱,甲醇-水为流动相,检测波长范围190~300 nm进行检测。结果表明,4种农药在6.5 min内实现了基线分离,线性相关系数(R2)≥0.999 8,检出限为2~5 μg/kg,样品加标平均回收率为82.5%~99.3%,精密度试验结果相对标准偏差(RSD)为1.64%~3.30%。该方法操作简单,灵敏度高,结果准确可靠。 相似文献
3.
Protective coatings from diethylphosphatoethyltriethoxysilane (DEPETS) have been deposited on different polymer substrates in a plasma discharge operated at atmospheric pressure. Plasma polymer chemistry and structure were characterized by means of Fourier transform infrared spectroscopy (FTIR), laser desorption ionization-mass spectrometry (LDI-MS), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). A chemical structure of the plasma polymer has been proposed based on the coating molecular characterization. Coatings were deposited on polycarbonate (PC) and polyamide 6 (PA6) substrates. The flame retardant properties of coated substrate samples were assessed using cone calorimetry and compared to those of bare substrates. A significant increase in the time to ignition (TTI), up to +143%, was recorded after coating deposition due to the formation of a high-performance barrier layer at the surface of both polymer substrates. 相似文献
4.
Luca Maria Chiesa Maria Nobile Federica Ceriani Francesco Arioli 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1340-1355
Demand for honey is increasing, especially if it is organic and if its nutritional properties are linked to untreated environments in order to guarantee quality for health. Sources of contamination of honey can be divided into environmental and apicultural. Therefore, the distribution of persistent organic pollutants, pesticides and antibiotic residues from geographical areas with different contamination sources (high anthropic impact, intensive farming, husbandry and low anthropic impact) was investigated in order to confirm the potential transfer of xenobiotics into the supply chain and to give beekeepers tools for the selection of areas dedicated to organic production. The presence of polychlorinated biphenyls, polybrominated diphenyl ether and polycyclic aromatic hydrocarbons was confirmed, not only in proximity to highly urbanised centres, where the concentrations were higher, but in all environment contexts, confirming their ubiquity. No antibiotics or neonicotinoids were detected in 95 organic honeys, demonstrating the absence of apicultural treatments and consequently the good quality of honey of different areas. These results are important due to the undefined regulatory European situation on honey antibiotic limits. 相似文献
5.
6.
7.
R. C. HARRIS MSc BSc CGeol FGS MIWM A. C. SKINNER PhD BSc CGeol FGS 《Water and Environment Journal》1992,6(6):569-574
The greatest threat of contamination to groundwater resources is posed by pollutants from diffuse sources, yet legislation in the UK has until recently been focused on point sources. The problem of widespread pollution from industrial sources is described and compared with that from agriculture. The legislative controls available under the Water Resources Act 1991 are outlined, and the approach adopted by the National Rivers Authority in its Groundwater Protection Policy is discussed with respect to the concept of groundwater vulnerability. 相似文献
8.
This study was conducted in Los Padres Lake from Argentina in order to assess the ability of Schoenoplectus californicus to bioconcentrate organochlorine pesticides (OCPs). Bulrush tissues, superficial and near root sediments were collected from the input and the output creek areas. OCP analyses were carried out by GC-ECD. Samples from the input creek area showed the higher OCP levels as a result of contaminants washed down from upstream agricultural fields. Bulrush roots accumulated the highest concentrations of pollutants (30.2-45.7ngg(-1) dry weight). DDTs and chlordanes predominated in sediments and roots besides endosulfan sulfate. The sediments constitute the main source for these OCPs partitioning to bulrush. Stems mainly exposed to water column accumulated preferentially the less hydrophobic pesticides, such as HCHs and endosulfans. We have confirmed the important role of S. californicus in the contaminant removal from sediments. Therefore, this macrophyte can be used as a tool for field studies of OCP pollution monitoring and remediation. 相似文献
9.
Chemical contaminants, health indicators, and reproductive biomarker responses in fish from the Colorado River and its tributaries 总被引:2,自引:1,他引:2
Hinck JE Blazer VS Denslow ND Echols KR Gross TS May TW Anderson PJ Coyle JJ Tillitt DE 《The Science of the total environment》2007,378(3):376-402
Common carp (Cyprinus carpio), black bass (Micropterus spp.), and channel catfish (Ictalurus punctatus) were collected from 14 sites in the Colorado River Basin (CRB) to document spatial trends in accumulative contaminants, health indicators, and reproductive biomarkers. Organochlorine residues, 2,3,7,8-tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ), and elemental contaminants were measured in composite samples of whole fish, grouped by species and gender, from each site. Selenium (Se) and mercury (Hg) concentrations in fish were elevated throughout the CRB, and pesticide concentrations were greatest in fish from agricultural areas in the Lower Colorado River and Gila River. Selenium concentrations exceeded toxicity thresholds for fish (>1.0 microg/g ww) at all CRB sites except the Gila River at Hayden, Arizona. Mercury concentrations were elevated (>0.1 microg/g ww) in fish from the Yampa River at Lay, Colorado; the Green River at Ouray National Wildlife Refuge (NWR), Utah and San Rafael, Utah; the San Juan River at Hogback Diversion, New Mexico; and the Colorado River at Gold Bar Canyon, Utah, Needles, California, and Imperial Dam, Arizona. Concentrations of p,p'-DDE were relatively high in fish from the Gila River at Arlington, Arizona (>1.0 microg/g ww) and Phoenix, Arizona (>0.5 microg/g ww). Concentrations of other formerly used pesticides including toxaphene, total chlordanes, and dieldrin were also greatest at these two sites but did not exceed toxicity thresholds. Currently used pesticides such as Dacthal, endosulfan, gamma-HCH, and methoxychlor were also greatest in fish from the Gila River downstream of Phoenix. Total polychlorinated biphenyls (PCBs; >0.11 microg/g ww) and TCDD-EQs (>5 pg/g ww) exceeded wildlife guidelines in fish from the Gila River at Phoenix. Hepatic ethoxyresorufin O-deethylase (EROD) activity was also relatively high in carp from the Gila River at Phoenix and in bass from the Green River at Ouray NWR. Fish from some sites showed evidence of contaminant exposure as indicated by fish health indicators and reproductive biomarker results. Multiple health indicators including altered body and organ weights and high health assessment index scores may be associated with elevated Se concentrations in fish from the Colorado River at Loma, Colorado and Needles. Although grossly visible external or internal lesions were found on most fish from some sites, histopathological analysis determined many of these to be inflammatory responses associated with parasites. Edema, exophthalmos, and cataracts were noted in fish from sites with elevated Se concentrations. Intersex fish were found at seven of 14 sites and included smallmouth bass (M. dolomieu), largemouth bass (M. salmoides), catfish, and carp and may indicate exposure to endocrine disrupting compounds. A high proportion of smallmouth bass from the Yampa River at Lay (70%) was intersex but the cause of this condition is unknown. Male carp, bass, and catfish with low concentrations of vitellogenin were common in the CRB. Comparatively high vitellogenin concentrations (>0.2 mg/mL) were measured in male bass from the Green River at Ouray NWR and the Colorado River at Imperial Dam and indicate exposure to estrogenic or anti-androgenic chemicals. Anomalous reproductive biomarkers including low GSI and gonadal abnormalities (calcifications, edema, and parasites) observed in fish downstream of Phoenix are likely related to the poor water-quality of the Gila River in this area. 相似文献
10.