全文获取类型
收费全文 | 590篇 |
免费 | 29篇 |
国内免费 | 38篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 24篇 |
2019年 | 23篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 23篇 |
2013年 | 31篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 15篇 |
2006年 | 34篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有657条查询结果,搜索用时 15 毫秒
641.
《Biotechnic & histochemistry》2013,88(2):92-93
Transverse paraffin sections of mature greenwood stems of rose (Rosa x hybrida) and flowering dogwood (Cornus florida L.) were stained with Bismarck brown followed by azure B or tolnidine blue O. The Bismarck brown was replaced by thiazin dye metachromasia in all structures except the cuticle which remained brown or yellow. The interface between the cuticle and exterior cell walls of the epidermis was delineated clearly. 相似文献
642.
《Biotechnic & histochemistry》2013,88(2):87-89
In three papers published on pituicytes, of the ox by Bucy (1930), of the human by Shanklin (1940), and of the horse by Vazquez-Lopez (1942) the pituitaries were sectioned by the freezing method and stained by the Hortega silver carbonate technic. Since that time, as a routine procedure in our laboratory, frozen sections have been replaced by paraffin which in no way interferes with the Hortega silver carbonate staining. 相似文献
643.
644.
645.
646.
Rugosa rose (Rosa rugosa Thunb.) is one of the most common rose species in Poland. It has mild soil and climate requirements and is resistant to low temperatures. Rugosa rose hips are a valuable raw material used in food and pharmaceutical industries, while flowers and petals may be a source of fragrant products, such as essential oil and hydrolate. The main aim of this study was to verify usefulness of dried R. rugosa petals for essential oil and hydrolate production. We also assessed the use of rugosa rose petals remaining after oil distillation for hydrolate production.The R. rugosa dried petals immersed in water were subjected to simple distillation and five fractions of primary rose hydrolate were obtained. In parallel, essential oil from the second sample of petals was obtained by hydrodistillation in Clevenger-type apparatus. The distillation residue was used for obtaining four fractions of secondary hydrolate. The volatiles from hydrolate fractions were isolated by liquid–liquid extraction with diethyl ether. The essential oil and hydrolate volatiles were analyzed by GC–FID–MS.Hydrolate fractions contained similar amounts of volatiles (20–30 mg/L) with the exception of the first fraction of primary hydrolate (60 mg/L). β-Phenylethanol, citronellol, geraniol, and nerol were the main volatile constituents of primary hydrolate. β-Phenylethanol, citronellic acid, and geranic acid were the main volatile constituents of secondary hydrolate. The content of alcohols decreased, while the content of monoterpene esters (citronellyl, neryl, and geranyl acetate) as well as monoterpene acids (citronellic, neric, and geranic acid) increased in successive fractions of both hydrolates.The scent and composition of essential oil and hydrolate obtained from R. rugosa petals were similar to those of rose oil and rose water produced from damask rose (Rosa damascena Mill.). This proves, that rugosa rose distillation products may become an alternative to fragrant damask rose products. 相似文献
647.
An adenosine triphosphate (ATP) bioluminescence‐based protocol was tested to assess the viability of fungal species in old documents damaged by foxing. Foxing appears as scattered yellow brownish‐red stains, damaging the aesthetics of documents and their long‐term readability. In the field of cultural heritage conservation, the debate over the mechanism of foxing is ongoing. Previous studies found evidence of mold‐like structures in some coloured areas; however, many species have not yet been identified and their role in the phenomenon is not understood. To better understand their involvement in this type of paper decay, we focused our attention first on their viability. We demonstrated the reliability and sensitivity of the ATP bioluminescence assay compared with conventional methods based on cultivation, which has rarely given rise to in vitro growth from foxed papers. From nine books dating back from the 19th and 20th centuries, the mean ATP amount of foxed spots ranged from 0.29 to 3.63 ng/cm2, suggesting the presence of strains inside the brownish spots and providing evidence of their viability. Outside the spots, ATP content was considered negligible, with a mean ATP amount of 0 to 0.03 ng/cm2. ATP assay appears to be a useful and robust method for the detection and quantification of viable elements in foxing spots. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
648.
649.
650.
James L. Sumich 《Marine Mammal Science》2021,37(3):870-887
A bioenergetic model is developed from empirically derived equations of morphometric, ventilatory and thermoregulatory variables to compare estimated field metabolic rates (FMR) of gray whale calves to estimates of unregulated body heat losses and consequent required thermogenesis at birth, natal lagoon departure, and weaning. Estimates of FMR are based on rates of oxygen consumption. Body surface and ventilatory heat fluxes are evaluated separately, then combined to estimate minimum total heat losses from birth to weaning at three ambient water temperature regimes typical of winter natal lagoons and Oregon coastal waters and arctic conditions during summer. Modeled heat losses of neonates in winter lagoons are half their estimated mean FMR. Neonates in good body condition appear to be capable of tolerating heat losses experienced in 10°C water without additional thermogenic activities above their estimated resting metabolic rates. This study provides new evidence that no thermoregulatory advantage accrues to neonates or to their mothers by being born in warm winter natal lagoons or by remaining there several weeks longer than other gray whales. Consequently, avoidance or reduced risk of killer whale predation seems a more likely candidate than reduced heat loss as the principal fitness benefit of low-latitude winter migrations. 相似文献