全文获取类型
收费全文 | 276篇 |
免费 | 18篇 |
国内免费 | 51篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 37篇 |
2018年 | 24篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 28篇 |
2010年 | 5篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有345条查询结果,搜索用时 62 毫秒
91.
Summary Samples of shoots ofPistacia lentiscus carrying galls of the aphid,Aploneura lentisci, were collected at three localities in Israel.
Shoots growing near pruning scars carried more galls than elsewhere on the plant, but these galls weighed less and contained
fewer aphids (smaller clones). The proportion of empty galls increased with gall density. Crowding of galls at such sites
may be due to the early burst of buds at the time of aphid emergence from the overwintering eggs, and not to active search
for preferred sites.
Shoots bearing larger numbers of leaves carried heavier galls, which contained larger aphid clones. The position of the galled
leaf on the shoot had no effect on gall weight nor on clone size.
The physiological condition of the plant may be an important environmental (ecological) factor affecting the variation in
clone-size and in aphid morphology among galls. 相似文献
92.
Summary Ethylene production was studied in shaken cultures ofPseudomonas putida andPseudomonas fluorescens isolated from soil and in unsterile garden soil samples moistened to 60% of the water holding capacity. The highest ethylene
accumulation in bacterial cultures was reached under conditions of delayed aeration,i.e. when the culture was closed and the aeration started after the oxygen content decreased to 4%. The ethylene production rose
immediately after the beginning of aeration. Under these conditions ethylene production was inP. fluorescens 2–3 times and in glucosecultivatedP. putida 6 times higher than in the fully aerated cultures. Methionine stimulated ethylene production byP. fluorescens, whereas glucose proved to be more suitable forP. putida. This strain was incapable of growth on methionine as the sole carbon source. Samples of nonsterile garden soil produced
the highest amounts of ethylene under anaerobic conditions. Artificial inoculation of soil samples byP. putida resulted in an increase of ethylene formation in samples with delayed aeration. Addition of glucose or glucose with methionine
stimulated ethylene production in all soil samples. 相似文献
93.
Dietary supplement Standard Reference Materials 总被引:1,自引:0,他引:1
A new category of Standard Reference Materials (SRMs) based on dietary supplements is under development by the National Institute of Standards and Technology (NIST), with certified values for organic constituents and selected trace elements. These materials are provided primarily for use in method development and as control materials. The SRMs will assist manufacturers of dietary supplements in characterizing raw materials for potency, authenticity, and contamination or adulteration. In addition, the SRMs will assist in assessment of consistency and quality in finished products. The goal of this ongoing effort is to provide tools to the dietary supplement industry and measurement communities that will lead to improved quality of dietary supplements, and ultimately reduce public health risks that could potentially be associated with these products. 相似文献
94.
Azetidine-2-carboxylic acid (L-Aze) is a toxic and teratogenic non-protein amino acid. In many species, including man, L-Aze is misincorporated into protein in place of proline, altering collagen, keratin, hemoglobin, and protein folding. In animal models of teratogenesis, it causes a wide range of malformations. The role of L-Aze in human disease has been unexplored, probably because the compound has not been associated with foods consumed by humans. Herein we report the presence of L-Aze in the garden or table beet (Beta vulgaris). 相似文献
95.
Govindjee 《Photosynthesis research》2006,87(2):151-158
This Editorial has four goals: (1) to inform the readers of ‘Photosynthesis Research‘ about the past of the ‘Historical corner’; which began 20 years ago; (2) to encourage photosynthesis researchers and historians of science to contact me for publishing papers of historical interest; these include: (a) Obituaries and Tributes; (b) historical papers on current and past discoveries and controversies; (c) history of research in specific laboratories, or in specific countries, or at specific conferences; (d) Personal perspectives (not discussed any further); (3) to encourage researchers not to discard, but to save correspondence and data of their discoveries for the future historians by donating them to their Archives, when appropriate (not discussed any further); and (4) to reinforce to the readers that the concept of two-light reaction and two-pigment system was already there in 1959. I mention here three key papers presented at the IXth International Botanical Congress, held at Montreal Canada (in August, 1959) prior to the famous April 9, 1960 paper by Robert Hill and Fay Bendall on the ‘Z-scheme’ of photosynthesis, that was based on thermodynamic and energetic considerations.
★ This Historical corner Editorial is dedicated to Bessel Kok (1918–1978). 相似文献
96.
In this study the authors analyse the incidence inthe airborne pollen from exotic plants that grow inthe Botanical Gardens of the University of Cagliari.It was possible to collect the pollen grains of 52 ofthe species cultivated in the Botanical Gardens, mostof which belong to the Leguminosae, the Moraceae and the Myrtaceae. Casuarinastricta Aiton of Australian origin shows the highestconcentration with 137 grains per cubic metre of air. 相似文献
97.
Y. -O. Lee A. Kanno T. Kameya 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(1):10-14
The genus Asparagus consists of 100–300 species of both dioecious and hermaphrodite plants. Since there are diploid, tetraploid, and hexaploid plants in this genus, RFLP (restriction fragment length polymorphism) analysis of chloroplast DNA (ctDNA) is suitable for examining the phylogenetic relationships. We have constructed a physical map of the ctDNA of garden asparagus (A. officinalis L. cv Mary Washington 500 W) using five restriction endonucleases, namely, BamHI, PstI, SalI, HindIII, and XhoI. Asparagus ctDNA was digested with restriction enzymes and cloned into plasmid and phage vectors, and a clone bank was constructed that covered 70% of the genome. A physical map was constructed by Southern hybridization of total DNA from asparagus with homologous and heterologous probes. The asparagus ctDNA was about 155 kb long and it contained two inverted repeats (23kb each) separated by a large single-copy region (90kb) and a small single-copy region (19kb). Fifteen genes, encoding photosynthesis-related proteins, rDNAs, and tRNAs, were localized on the physical map of asparagus ctDNA. Comparing the length and the gene order of asparagus ctDNA with that of other plants, we found that asparagus ctDNA was similar to tobacco ctDNA but different from rice ctDNA. The restriction patterns of the ctDNAs from several varieties of A. officinalis and three species of Asparagus were analyzed. The restriction patterns of the varieties of A. officinalis were very similar, but polymorphisms were detected among the three species of Asparagus. 相似文献
98.
D.M. Anderson E.L. Fredrickson P. Nachman R.E. Estell K.M. Havstad L.W. Murray 《Animal Feed Science and Technology》1998,70(4):1905
Filtrate from pre- and post-digested plant material was exposed to 355-nm pulsed laser light and the subsequent laser-induced fluorescence (LIF) was recorded. Similarities and differences among spectra from 20 materials are discussed. Each material was replicated once, dried, ground, and exposed to chloroform (CHCl3) for 24 h. The material represented aged (1 to 18 years old) plants from different herbaceous (grasses and forbs) and woody plant life forms. Mean peak fluorescence recorded among materials differed (P<0.0001) in both wavelength and peak amplitude (counts) across the spectral range (387 to 788 nm). Peak fluorescence was evaluated within each of three arbitrary color categories, blue near 455 nm and red near 674 nm, while only 16 of the materials produced a green peak near 528 nm. In general, the blue and green fluorescence peaks were broad while the red peak was narrow. Mean peak counts were largest in the red range. Varying amounts of laser beam absorption occurred among the materials evaluated due to different concentrations of filtrate and different absorption efficiencies; therefore, amplitude data (counts) were not used to determine statistical differences among materials. To overcome difficulties attributed to the raw count data, red/blue, red/green and blue/green count ratios within replicates were calculated. Using all three count ratios in a multivariate analysis of variance, the 16 materials could be separated into nine different (P<0.05) material groupings. The LIF technique may provide a reliable means to separate ground pre- and post-digested plant materials following further research into determining what fluorophores are producing the spectral signatures and how sample preparation affect peak wavelengths. 相似文献
99.
100.
Energetics of fattening and starvation in the long-distance migratory garden warbler,Sylvia borin,during the migratory phase 总被引:5,自引:2,他引:3
M. Klaassen H. Biebach 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(5):362-371
Garden warblers (Sylvia borin) were subjected to starvation trials during their autumnal migratory phase in order to simulate a period of non-stop migration. Before, during and after this treatment the energy expenditure, activity, food intake and body mass of the subjects were monitored. Assimilation efficiency was constant throughout the experiments. The catabolized (during starvation) and deposited body tissue (during recovery) consisted of 73% fat. Basal metabolic rate was decreased during the starvation period and tended to a gradual increase during the recovery period. The reduced basal metabolic rate can possibly be attributed to a reduced size/function of the digestive system, which is consistent with the sub-maximal food intake immediately after resuming the supply of food to the experimental birds. The observed reductions in basal metabolic rate during starvation and activity during recovery can be viewed as adaptations contributing to a higher economization of energy supplies. The experimental birds were unable to eat large quantities of food directly after a period of starvation leading to a comparatively low, or no increase in body mass. Such a slow mass increase is in agreement with observations of migratory birds on arrival at stop-over sites.Abbreviations BM
body mass
- BMR
basal metabolic rate
- LBM
lean body mass
- RQ
respiratory quotient 相似文献