全文获取类型
收费全文 | 765篇 |
免费 | 58篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 9篇 |
化学工业 | 83篇 |
金属工艺 | 4篇 |
机械仪表 | 5篇 |
建筑科学 | 3篇 |
矿业工程 | 4篇 |
能源动力 | 41篇 |
轻工业 | 552篇 |
水利工程 | 2篇 |
石油天然气 | 47篇 |
无线电 | 7篇 |
一般工业技术 | 38篇 |
冶金工业 | 7篇 |
原子能技术 | 2篇 |
自动化技术 | 19篇 |
出版年
2024年 | 21篇 |
2023年 | 58篇 |
2022年 | 69篇 |
2021年 | 53篇 |
2020年 | 61篇 |
2019年 | 50篇 |
2018年 | 29篇 |
2017年 | 38篇 |
2016年 | 34篇 |
2015年 | 36篇 |
2014年 | 52篇 |
2013年 | 42篇 |
2012年 | 37篇 |
2011年 | 37篇 |
2010年 | 17篇 |
2009年 | 22篇 |
2008年 | 5篇 |
2007年 | 32篇 |
2006年 | 19篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有824条查询结果,搜索用时 0 毫秒
12.
Lijuan Zhan Jinqiang Hu Lingyun Pang Yu Li Jianfeng Shao 《International Journal of Food Science & Technology》2014,49(2):347-353
Effects of light exposure (24 μmol m?2 s?1) on fresh‐cut celery nutritional quality were evaluated during 8‐day storage at 7 °C using darkness as control. Light exposure preserved 47% chlorophyll a and 48% chlorophyll b contents more than darkness at the end of storage. Sucrose, reducing sugar and glucose contents in light‐stored petioles were 17%, 25% and 67% higher than those in dark‐stored petioles after 8‐day storage, respectively, thus resulting in higher total soluble solids content in light condition. Moreover, l ‐ascorbic acid content increased at 2‐day storage in light condition and was 46% more than in darkness at the end of storage. The fresh weight loss significantly increased in all petioles, and this increase was markedly accelerated by light exposure with a maximum of 1.43% at the end of storage. Dry matter content was induced more by light exposure than by darkness at 2‐day storage. 相似文献
13.
Ozone was investigated as a potential alternative to control phosphine resistant strains of the lesser grain borer, Rhyzopertha dominica (F.). The efficacy of 0.21 and 0.42 g/m3 concentrations of ozone against one phosphine-susceptible laboratory and two phosphine-resistant field strains of R. dominica was evaluated. Vials holding 20 adults with 0 and 10 g of wheat were exposed to each ozone concentration for up to 24 h to estimate lethal doses required for 50 (LD50) and 99% (LD99) mortality. After ozone exposure, mortality was assessed 5 d later. There were no significant differences between LD50 values of the samples exposed to 0.21 and 0.42 g/m3, regardless of strains and presence or absence of wheat. The small amount of wheat (10 g) affected efficacy at 0.21 g/m3, but showed a non-significant effect at 0.42 g/m3. Ozone tends to react with active sites on the surface of wheat kernels prior to reaching an effective lethal concentration for insects. High ozone concentration in the supply air reduced the time to saturate all active sites and ensured that lethal levels of free ozone were available to kill insects.Ozone successfully suppressed the adult progeny production for all tested strains. Emergence of adults from eggs of all three strains was reduced by 96.3–100% only after 72 h exposure to an ozone concentration of 0.42 g/m3. At the same ozone concentration, emergence of adults from young and old larvae was reduced by 97.1–99.7% after a 24 to 34 h exposure. However, reduction in emergence of adults from ozone exposed pupae at 10 h varied among the strains and ranged from 32.8 to 96.6%. After 2 and 6 h of exposure the reduction in emergence of adults from pupae ranged from 19.6 to 76.5%. 相似文献
14.
15.
16.
Oryzaephilus surinamensis and Cryptolestes ferrugineus are serious secondary pests that infest commodities and packaged food. Both species differ in their climbing ability on smooth surfaces, such as the surfaces of packages or grains. In this study, we tested the hypothesis that tarsal and inter-claw adhesive structures of the species differ significantly. To test this hypothesis, we morphologically described and compared (quantitatively and qualitatively) the claws and setal structures on the tarsi and claws of O. surinamensis and C. ferrugineus using scanning electron microscopy (SEM). The main difference found was in the presence and/or quantity of tarsal and inter-claw adhesive structures between O. surinamensis and C. ferrugineus. The profound morphological differences regarding the presence and higher quantity of adhesive structures can explain why O. surinamensis is a better climber than C. ferrugineus on inclined smooth surfaces. The shape of the claws was similar in both species, but those of C. ferrugineus were slightly shorter and sharper (i.e., claw tip radius = 1.17 μm) than those of O. surinamensis (tip radius = 1.63 μm), indicating that C. ferrugineus is better morphologically adapted to move over rough material with smaller asperities. The obtained results suggest that the presence or absence of adhesive tarsal structures can be used for assessment of the ability of various pests to move on smooth surfaces of packaging or grains. The outcomes of the work may also provide inspiration to material and biomimetic scientists to improve pest-proof packaging material with anti-adhesive properties. 相似文献
17.
The effect of different vitamins and nitrogen sources on the yield, productivity and selectivity of erythritol production from glycerol in batch and fed-batch cultures by Yarrowia lipolytica Wratislavia K1 strain was examined in the study.Thiamine was a vitamin necessary for efficient erythritol production and the yeast extract (YE) turned out to be its best source. The YE was additionally a very good source of nitrogen in this process. Erythritol production may be efficient in the media containing only yeast extract and crude glycerol. The application of a high substrate concentration (325 kg m−3) in the fed-batch system with pulsed addition of glycerol resulted in erythritol production of 201.2 kg m−3 after 168 h of cultivation. The mass fraction of by-products, such as other polyols and organic acids, did not exceed 10%. The study showed that by-products formation could be significantly reduced by the addition of a nitrogen source after glycerol depletion from the media. Wratislavia K1 strain does not utilize erythritol in the presence of other carbon sources and this feature was used in order to increase product selectivity up to 99.7% and protein content in yeast biomass up to 28.7%. The factors determining the use of biomass as animal feed, i.e. protein concentration and presence of metal ions, were discussed as well. 相似文献
18.
Self-fermentation of cellulosic substrates to produce biohydrogen without inoculum addition nor pretreatments was investigated. Dark fermentation of two different substrates made of leaf-shaped vegetable refuses (V) and leaf-shaped vegetable refuses plus potato peels (VP), was taken in consideration. Batch experiments were carried out, under two mesophilic anaerobic conditions (28 and 37 °C), in order to isolate and to identify potential H2-producing bacterial strains contained in the vegetable extracts. The effect of initial glucose concentration (at 1, 5 and 10 g/L) on fermentative H2 production by the isolates was also evaluated.H2 production from self-fermentation of both biomasses was found to be feasible, without methane evolution, showing the highest yield for V biomass at 28 °C (24 L/kg VS). The pH control of the culture medium proved to be a critical parameter. The isolates had sequence similarities ≥98% with already known strains, belonging to the family Enterobacteriaceae (γ-proteobacteria) and Streptococcaceae (Firmicutes). Four genera found in the samples, namely Pectobacterium, Raoultella, Rahnella and Lactococcus have not been previously described for H2 production from glucose. The isolates showed higher yield (1.6–2.2 mol H2/mol glucoseadded) at low glucose concentration (1 g/L), while the maximum H2 production ranged from 410 to 1016 mL/L and was obtained at a substrate concentration of 10 g/L. The results suggested that vegetable waste can be effectively used as both, substrate and source of suitable microflora for bio-hydrogen production. 相似文献
19.
The cooperative interactions between chalcopyrite and bornite during bioleaching by mixed moderately thermophilic culture were investigated mainly by bioleaching experiments and electrochemical experiments. Bioleaching results showed that a cooperative effect existed between chalcopyrite and bornite. When the mass ratio of chalcopyrite to bornite was 3:1, an extremely high copper extraction of more than 88% was achieved after bioleaching for 27 days. One of the major reasons for the cooperative effect was that a certain redox potential range (370–450 mV vs. Ag/AgCl) could be maintained for a long period of time during bioleaching due to the mixture of chalcopyrite and bornite. Electrochemical measurements revealed that chalcopyrite was much easier to be reduced than oxidized, while bornite was prone to be directly oxidized. Hence, galvanic effect between chalcopyrite and bornite enhanced the reduction of chalcopyrite to secondary copper-iron species and promoted the oxidative dissolution of bornite. Therefore, redox potential controlling and galvanic effect both contributed to the cooperative bioleaching of chalcopyrite and bornite. 相似文献
20.
《Food Control》2017
Finnish food control authorities waived pre-inspections of food premises in 2011, leaving food business operators to begin operating with no pre-operation food control. This study aims to investigate the effects of this food policy change on the preconditions for Good Hygienic Practices (GHPs) on food premises. Of the 916 food premises that were included in this study, 379 were pre-approved whereas 537 merely notified their operations. The results show that notified food service premises (restaurants) preparing food displayed significantly more non-compliance pertaining to infrastructure than did restaurants pre-approved for food preparation (11.5% and 1.8% of the premises, respectively) (p < 0.05). Significant differences also emerged in the number of premises with non-compliance pertaining to cleaning facilities and equipment, and marked differences in the adequacy of hand and other washing sites. Such instances of non-compliance weaken the preconditions for GHPs. The results suggest that re-introducing pre-inspections of restaurants would strengthen the preconditions for GHPs and possibly provide a model for other countries with similar food control systems. 相似文献