全文获取类型
收费全文 | 65563篇 |
免费 | 10307篇 |
国内免费 | 4924篇 |
专业分类
电工技术 | 5969篇 |
技术理论 | 5篇 |
综合类 | 8748篇 |
化学工业 | 4999篇 |
金属工艺 | 2374篇 |
机械仪表 | 5298篇 |
建筑科学 | 11546篇 |
矿业工程 | 3125篇 |
能源动力 | 2055篇 |
轻工业 | 1739篇 |
水利工程 | 3356篇 |
石油天然气 | 2212篇 |
武器工业 | 1211篇 |
无线电 | 5035篇 |
一般工业技术 | 6500篇 |
冶金工业 | 2089篇 |
原子能技术 | 380篇 |
自动化技术 | 14153篇 |
出版年
2025年 | 32篇 |
2024年 | 1534篇 |
2023年 | 1475篇 |
2022年 | 2062篇 |
2021年 | 2244篇 |
2020年 | 2385篇 |
2019年 | 2005篇 |
2018年 | 1868篇 |
2017年 | 2286篇 |
2016年 | 2649篇 |
2015年 | 2735篇 |
2014年 | 4015篇 |
2013年 | 3915篇 |
2012年 | 4833篇 |
2011年 | 5022篇 |
2010年 | 4057篇 |
2009年 | 4147篇 |
2008年 | 4033篇 |
2007年 | 4875篇 |
2006年 | 4247篇 |
2005年 | 3542篇 |
2004年 | 2903篇 |
2003年 | 2470篇 |
2002年 | 2089篇 |
2001年 | 1762篇 |
2000年 | 1538篇 |
1999年 | 1190篇 |
1998年 | 929篇 |
1997年 | 772篇 |
1996年 | 630篇 |
1995年 | 516篇 |
1994年 | 443篇 |
1993年 | 338篇 |
1992年 | 263篇 |
1991年 | 204篇 |
1990年 | 176篇 |
1989年 | 157篇 |
1988年 | 113篇 |
1987年 | 58篇 |
1986年 | 32篇 |
1985年 | 36篇 |
1984年 | 42篇 |
1983年 | 32篇 |
1982年 | 24篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
通过热灌装线洁净室设计的基本要求、良好的GMP控制与洁净室运行管理、严格的检测监控措施3方面介绍了控制灌装环境的空气清洁度的有效措施。从而为洁净室在热灌装线的应用提供了较有借鉴意义的资料。 相似文献
994.
995.
996.
Claudine A Rasolohery Monique Berger Anatoliy V Lygin Vera V Lozovaya Randall L Nelson Jean Daydé 《Journal of the science of food and agriculture》2008,88(2):218-228
BACKGROUND: Isoflavone content in soybean seeds is strongly influenced by both environment and genotype. However, little is known about the effect of environment and genotype on isoflavones in germ versus cotyledons. To determine the effect of temperature and soil moisture status during soybean seed development on seed isoflavone concentration and composition, a set of two French and three US cultivars of similar maturity were grown in the greenhouse. At the R6 growth stage, plants were subjected to one of three night/day temperature regimes (13/23°, 18/28° or 23/33 °C) in either optimal or sub‐optimal soil water conditions. RESULTS: In cotyledons, a three‐ to six‐fold variation in total isoflavone content was observed between the high and low temperature treatments, whereas the germ contents had less than a two‐fold variation. Soil water supply had less effect than temperature on the isoflavone contents and compositions. In both seed parts, the isoflavone concentrations were highly dependent on the cultivar. CONCLUSION: These results show that isoflavone content and composition in cotyledon and germ are unrelated and it should be possible to independently manipulate these seed traits through plant breeding and crop management systems. Copyright © 2007 Society of Chemical Industry 相似文献
997.
Karina Jensen Lars P Christensen Merete Hansen Ulla Jrgensen Karl Kaack 《Journal of the science of food and agriculture》2001,81(2):237-244
Aroma compounds emitted from elderberry juices processed from seven cultivars were collected by the dynamic headspace technique and analysed by GC–FID and GC–MS. Forty aroma compounds were identified and quantified, including nine compounds which had not previously been detected in elderberry juice. Significant differences were found among cultivars in the concentration levels of 30 compounds. The sensory characteristics of the individual aroma compounds in elderberry juice were determined by a GC‐sniffing technique, and the compounds were grouped according to their odour. The characteristic elderberry odour is due to dihydroedulan and β‐damascenone, of which the former occurs in relatively high concentrations in the headspace of elderberry juice. The fruity group consisted of aliphatic alcohols and aldehydes and aromatic esters, of which 1‐pentanal, 2‐methyl‐1‐propanol, 2‐ and 3‐methyl‐1‐butanol, 1‐octanal, 1‐octanol and methyl and ethyl benzoate contributed with fruity notes. In the flowery group, 1‐nonanal, nerol oxide and (Z)‐ and (E)‐rose oxide contributed with characteristic elder flower odour, whereas other flowery notes were associated with hotrienol, linalool and α‐terpineol. Fresh and grassy odours were correlated with 1‐hexanal, (E)‐2‐hexen‐1‐al, (Z)‐3‐hexen‐1‐ol, (E)‐2‐hexen‐1‐ol and (E)‐2‐octen‐1‐al of the grassy group, whereas 1‐octen‐3‐ol and 1‐octen‐3‐one of the agrestic group contributed significantly with the characteristic aroma of mushrooms. © 2000 Society of Chemical Industry 相似文献
998.
Dan B. Jensen Mariska van der Voort Henk Hogeveen 《Journal of dairy science》2018,101(11):10428-10439
Accurate forecasting of dairy cow milk yield is useful to dairy farmers, both in relation to financial planning and for detection of deviating yield patterns, which can be an indicator of mastitis and other diseases. In this study we developed a dynamic linear model (DLM) designed to forecast milk yields of individual cows per milking, as they are milked in milking robots. The DLM implements a Wood's function to account for the expected total daily milk yield. It further implements a second-degree polynomial function to account for the effect of the time intervals between milkings on the proportion of the expected total daily milk yield. By combining these 2 functions in a dynamic framework, the DLM was able to continuously forecast the amount of milk to be produced in a given milking. Data from 169,774 milkings on 5 different farms in 2 different countries were used in this study. A separate farm-specific implementation of the DLM was made for each of the 5 farms. To determine which factors would influence the forecast accuracy, the standardized forecast errors of the DLM were described with a linear mixed effects model (lme). This lme included lactation stage (early, middle, or late), somatic cell count (SCC) level (nonelevated or elevated), and whether or not the proper farm-specific version of the DLM was used. The standardized forecast errors of the DLM were only affected by SCC level and interactions between SCC level and lactation stage. Therefore, we concluded that the implementation of Wood's function combined with a second-degree polynomial is useful for dynamic modeling of milk yield in milking robots, and that this model has potential to be used as part of a mastitis detection system. 相似文献
999.
Jia Liu Michael Wisniewski Zhigang Xie Yiqing Liu Yuming You 《Critical reviews in food science and nutrition》2018,58(10):1681-1687
Postharvest decay of fruits, vegetables, and grains by fungal pathogens causes significant economic losses. Infected produce presents a potential health risk since some decay fungi produce mycotoxins that are hazardous to human health. Infections are the result of the interplay between host resistance and pathogen virulence. Both of these processes, however, are significantly impacted by environmental factors, such as temperature, UV, oxidative stress, and water activity. In the present review, the impact of various physical postharvest treatments (e.g., heat and UV) on the viability and virulence of postharvest pathogens is reviewed and discussed. Oxidative injury, protein impairment, and cell wall degradation have all been proposed as the mechanisms by which these abiotic stresses reduce fungal viability and pathogenicity. The response of decay fungi to pH and the ability of pathogens to modulate the pH of the host environment also affect pathogenicity. The effects of the manipulation of the postharvest environment by ethylene, natural edible coatings, and controlled atmosphere storage on fungal viability are also discussed. Lastly, avenues of future research are proposed. 相似文献
1000.