首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   99篇
  免费   12篇
  国内免费   1篇
工业技术   112篇
  2022年   1篇
  2021年   6篇
  2020年   2篇
  2019年   1篇
  2018年   8篇
  2017年   3篇
  2016年   4篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2012年   2篇
  2011年   2篇
  2010年   6篇
  2009年   9篇
  2008年   4篇
  2007年   8篇
  2006年   5篇
  2005年   4篇
  2004年   8篇
  2003年   5篇
  2002年   2篇
  2001年   2篇
  2000年   2篇
  1999年   4篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1993年   1篇
  1992年   1篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1973年   1篇
排序方式: 共有112条查询结果,搜索用时 31 毫秒
1.
Intensive fertilizer use has led to nitrate contamination of groundwater in many areas. This article examines the possibility of removing nitrates through the construction of artificial wetlands. A pilot study conducted in Denmark has found that the method is effective and economical, at least for small waterworks, though further treatment is necessary before an acceptable microbiological water quality is attained.  相似文献   
2.
The G-protein coupled receptor GPR39 is abundantly expressed in various tissues and can be activated by changes in extracellular Zn2+ in physiological concentrations. Previously, genetically modified rodent models have been able to shed some light on the physiological functions of GPR39, and more recently the utilization of novel synthetic agonists has led to the unraveling of several new functions in the variety of tissues GPR39 is expressed. Indeed, GPR39 seems to be involved in many important metabolic and endocrine functions, but also to play a part in inflammation, cardiovascular diseases, saliva secretion, bone formation, male fertility, addictive and depression disorders and cancer. These new discoveries offer opportunities for the development of novel therapeutic approaches against many diseases where efficient therapeutics are still lacking. This review focuses on Zn2+ as an endogenous ligand as well as on the novel synthetic agonists of GPR39, placing special emphasis on the recently discovered physiological functions and discusses their pharmacological potential.  相似文献   
3.
Despite the existence of patterns able to discriminate between consensual and non-consensual intercourse, the relevance of genital lesions in the corroboration of a legal rape complaint is currently under debate in many countries. The testimony of the physicians when assessing these lesions has been questioned in court due to several factors (e.g., a lack of comprehensive knowledge of lesions, wide spectrum of background area, among others). Therefore, it is relevant to provide automated tools to support the decision process in an objective manner. In this work, we evaluate the performance of state-of-the-art deep learning architectures for the forensic assessment of sexual assault. We propose a deep architecture and learning strategy to tackle the class imbalance on deep learning using ranking. The proposed methodologies achieved the best results when compared with handcrafted feature engineering and with other deep architectures.  相似文献   
4.
5.
Insulin-like growth factor-1 (IGF-1) is a serum protein whichunexpectedly folds to yield two stable tertiary structures withdifferent disulphide connectivities; native IGF-1 [18–61,6–48,47–52]and IGF-1 swap [18–61,6–47, 48–52]. Here we demonstratein detail the biological properties of recombinant human nativeIGF-1 and IGF-1 swap secreted from Saccharomyces cerevisiae.IGF-1 swap had a ~30 fold loss in affinity for the IGF-1 receptoroverexpressed on BHK cells compared with native IGF-1.The parallelincrease in dose required to induce negative cooperativity togetherwith the parallel loss in mitogenicity in NIH 3T3 cells impliesthat disruption of the IGF-1 receptor binding interaction ratherthan restriction of a post-binding conformational change isresponsible for the reduction in biological activity of IGF-1swap. Interestingly, the affinity of IGF-1 swap for the insulinreceptor was ~200 fold lower than that of native IGF-1 indicatingthat the binding surface complementary to the insulin receptor(or the ability to attain it) is disturbed to a greater extentthan that to the IGF-1 receptor. A 1.0 ns high-temperature moleculardynamics study of the local energy landscape of IGF-1 swap resultedin uncoiling of the first A-region -helix and a rearrangementin the relative orientation of the A- and B-regions. The modelof IGF-1 swap is structurally homologous to the NMR structureof insulin swap and CD spectra consistent with the model arepresented. However, in the model of IGF-1 swap the C-regionhas filled the space where the first A-region -helix has uncoiledand this may be hindering interaction of Val44 with the secondinsulin receptor binding pocket.  相似文献   
6.
In many popular texture analysis methods, second or higher order statistics on the relation between pixel gray level values are stored in matrices. A high dimensional vector of predefined, nonadaptive features is then extracted from these matrices. Identifying a few consistently valuable features is important, as it improves classification reliability and enhances our understanding of the phenomena that we are modeling. Whatever sophisticated selection algorithm we use, there is a risk of selecting purely coincidental "good" feature sets, especially if we have a large number of features to choose from and the available data set is limited. In a unified approach to statistical texture feature extraction, we have used class distance and class difference matrices to obtain low dimensional adaptive feature vectors for texture classification. We have applied this approach to four relevant texture analysis methods. The new adaptive features outperformed the classical features when applied to the most difficult set of 45 Brodatz texture pairs. Class distance and difference matrices also clearly illustrated the difference in texture between cell nucleus images from two different prognostic classes of early ovarian cancer. For each of the texture analysis methods, one adaptive feature contained most of the discriminatory power of the method.  相似文献   
7.
Renewable energy sources have received increased interest from the international community with biomass being one of the oldest and the most promising ones. In the concept of exploitation of agro-industrial residues, the present study investigates the pre-treatment and ethanol fermentation potential of the olive pulp, which is the semi solid residue generated from the two-phase processing of the olives for olive oil production. Wet oxidation and enzymatic hydrolysis have been applied aiming at the enhancement of carbohydrates' bioavailability. Different concentrations of enzymes and enzymatic durations have been tested. Both wet oxidation and enzymic treatment were evaluated based on the ethanol obtained in a subsequent fermentation step by Saccharomyces cerevisiae and Thermoanaerobacter mathranii. It was found that a four-day hydrolysis time was adequate for a satisfactory release of glucose and xylose. The combination of wet oxidation and enzymatic hydrolysis resulted in the glucose and xylose concentration increase of 138 and 444%, respectively, compared to 33 and 15% with only enzymes added. However, the highest ethanol production was obtained when only enzymic pre-treatment was applied, implying that wet oxidation is not a recommended pre-treatment process for olive pulp at the conditions tested. It was also showed that increased dry matter concentration did not have a negative effect on the release of sugars, indicating that the cellulose and xylan content of the olive pulp is relatively easily available. The results of the experiments in batch processes clearly emphasize that the simultaneous saccharification and fermentation (SSF) mode is advantageous in comparison with the separate hydrolysis and fermentation (SHF) mode concerning process contamination.  相似文献   
8.
ABSTRACT:  In this study, photooxidation of sour cream packaged in cups with different light barrier properties was investigated. The sour cream was light exposed for 36 h with a standard fluorescent light tube, simulating storage conditions in many Norwegian grocery stores. Three different cups were evaluated: a white cup, a cup with medium light barrier (LB), and a cup with high LB. The quality of the sour cream was evaluated by sensory analysis and front face fluorescence spectroscopy. The sour cream stored in white cups became very rancid during the light exposure, with a rancid flavor score of 7.8 on a scale from 1 to 9, where 9 is the highest intensity. Cups with high LB gave best protection against the light. The sensory assessors could not distinguish between sour cream stored in cups with high LB and sour cream stored in the dark. The rancid flavor intensity for the cups with medium LB was significantly different ( P  < 0.05) from both the white cup and the cup with high LB. The sensory flavor intensities indicated that with 36 h of light exposure, only a cup with high LB will protect the sour cream sufficiently. The fluorescence measurements corresponded well with the sensory analysis as the photosensitizers were somewhat degraded for sour cream stored in cups with medium LB and most degraded in the white cups. For the cups with high LB, the fluorescence peaks that originated from the photosensitizers were all intact.
PRACTICAL APPLICATION: Dairy products such as sour cream will develop off-odor and taste faults ("sunlight taste") in a few hours if exposed to sufficient fluorescent lightning in the grocery stores. A light barrier can be incorporated in the packaging material to protect the dairy products from the light. Our experiment showed that the incorporation of a black pigment into 1 of the 3 plastic layers in the cup for packaging of sour cream protected the sour cream from degradation when exposed to light.  相似文献   
9.
Woody yard waste with high lignin content (22% of dry matter (DM)) was subjected to wet oxidation pre‐treatment for subsequent enzymatic conversion and fermentation. The effects of temperature (185–200 °C), oxygen pressure (3–12 bar) and addition of sodium carbonate (0–3.3 g per 100 g DM biomass) on enzymatic cellulose and hemicellulose (xylan) convertibility were studied. The enzymatic cellulose conversion was highest after wet oxidation for 15 min at 185 °C with addition of 12 bars of oxygen and 3.3 g Na2CO3 per 100 g waste. At 25 FPU (filter paper unit) cellulase g?1 DM added, 58–67% and 80–83% of the cellulose and hemicellulose contained in the waste were converted into monomeric sugars. The cellulose conversion efficiency during a simultaneous saccharification and fermentation (SSF) assay at 10% DM was 79% for the highest enzyme loading (25 FPU g?1 DM) while 69% conversion efficiency was still reached at 15 FPU g?1 DM. Total carbohydrate recoveries were high (91–100% for cellulose and 72–100% for hemicellulose) and up to 49% of the original lignin and 79% of the hemicellulose could be solubilized during wet oxidation treatment and converted into carboxylic acids mainly (total carboxylic acids = 3.1–7.4% on DM basis). Copyright © 2004 Society of Chemical Industry  相似文献   
10.
A series of bioisosteric N1‐ and N2‐substituted 5‐(piperidin‐4‐yl)‐3‐hydroxypyrazole analogues of the partial GABAAR agonists 4‐PIOL and 4‐PHP have been designed, synthesized, and characterized pharmacologically. The unsubstituted 3‐hydroxypyrazole analogue of 4‐PIOL ( 2 a ; IC50~300 μM ) is a weak antagonist at the α1β2γ2 GABAAR, whereas substituting the N1‐ or N2‐position with alkyl or aryl substituents resulted in antagonists with binding affinities in the high nanomolar to low micromolar range at native rat GABAARs. Docking studies using a α1β2γ2 GABAAR homology model along with the obtained SAR indicate that the N1‐substituted analogues of 4‐PIOL and 4‐PHP, 2 a – k , and previously reported 3‐substituted 4‐PHP analogues share a common binding mode to the orthosteric binding site in the receptor. Interestingly, the core scaffold of the N2‐substituted analogues of 4‐PIOL and 4‐PHP, 3 b – k , are suggested to flip 180° thereby adapting to the binding pocket and addressing a cavity situated above the core scaffold.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号