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81.
Effects of artificial ultraviolet-B radiation on growth and fatty acid composition of duckweed (Lemna minor) 总被引:1,自引:0,他引:1
D. L. W. YOUNG M. D. WIEGAND N. L. LOADMAN S. A. COLLINS A. J. BALLEVONA J. D. HUEBNER 《Freshwater Biology》2006,51(11):2029-2040
1. Duckweed (Lemna minor), collected either in summer or early fall was exposed under laboratory conditions to control (photosynthetically active and UV‐A radiation) or experimental (control plus UV‐B radiation) conditions. 2. Growth and survival were determined by counting the number of green, and brown/white fronds following 1–5 or 11 days of irradiation. Growth of duckweed was impaired by exposure to UV‐B radiation in the fall experiment but not in the summer. 3. Fatty acid compositions were analysed following 5 or 11 days of irradiation and a recovery period of 0, 5, 29 or 40 h. Concentrations of the major fatty acids, palmitic, linoleic (LA) and α‐linolenic (ALA) acids were similar in the summer and fall duckweed collections, but the summer samples had higher concentrations of the desaturation products of LA and ALA. 4. UV‐B exposure had small, but significant, and contrasting effects on duckweed fatty acid concentrations. In the summer experiment, duckweed exposed to UV‐B had slightly lower concentrations of major fatty acids than control duckweed, while the reverse was true in the fall experiments. 5. These minor effects of UV‐B on concentrations of LA and ALA would be unlikely to have a major impact on the supply of these essential fatty acids from duckweed to freshwater food webs. 相似文献
82.
几种高等水生植物的克藻效应 总被引:71,自引:2,他引:69
研究了水花生、水浮莲、满江红、紫萍、浮萍和西洋菜对雷氏衣藻的相生相克关系,并和水葫芦的作用进行了比较。试验指出前五种水生植物对雷氏衣藻表现了克制作用,但它们的克藻效能不如水葫芦强。西洋菜没有克制作用,甚至稍有促进效应。从水花生、水浮莲、水葫芦的种植水中得到的分泌物粗提物,都显示了对雷氏衣藻的抑制效应,进一步证实了有相生相克关系的存在。试验结果说明高等水生植物对藻类的克制作用似有一定的普遍性,在水生生态系统的形成和演替过程中可能起着重要的作用。 相似文献
83.
84.
The floral homeotic protein SEPALLATA3 recognizes target DNA sequences by shape readout involving a conserved arginine residue in the MADS‐domain
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85.
芬芳桔色藻的一个新变种梁良弼毕列爵(福建师范大学生物系福州350007)(湖北大学生命科学系武汉430062)关键词芬芳桔色藻,芬芳桔色藻小型变种,云南ANEWVARIETYOFTRENTEPOHLIAODORATA(WIGGERS)WITTROCK... 相似文献
86.
Images of chlorophyll-a-fluorescence oscillations were recorded using a camera-based fluorescence imaging system. Oscillations with frequencies around 1 per min were initiated by a transient decrease in light intensity during assimilation at an elevated CO2-concentration. The oscillation was inhomogenously distributed over the leaf. In cells adjacent to minor veins, frequency and damping rate was high, if there was any oscillation. In contrast, the amplitude was highest in cells most distant from phloem elements (maximal distance about 300 m). The appearance of minor veins in oscillation images is explained by a gradient in the metabolic control in the mesophyll between minor veins and by transport of sugar from distant cells to phloem elements. The potential of fluorescence imaging to visualize microscopic source-sink interactions and metabolic domains in the mesophyll is discussed.Abbreviations Pi
inorganic phosphate
- Fru2,6BP
fructose-2,6-bisphosphate
- FBPase
fructose-1,6-bisphosphatase
- SPS
sucrose-phosphate synthetase
- HP
hexosephosphate 相似文献
87.
A new, sand-dwelling, armored dinoflagellate, Roscoffia minor sp. nov., is described from Ishikari beach, Hokkaido, Japan. The dinoflagellate has been collected from sand samples taken both near the water's edge and further upshore (25 m from the water's edge at a depth of 1 m), indicating that it is a true sand-dwelling species. Roscoffia minor is heterotrophic and lacks both a chloroplast and an eye-spot. The cell consists of a flattened cap-shaped epitheca and a large hemispheroidal hypotheca, and it is quite different from cells of the typical armored dinoflagellates. The thecal plate formula is: Po, 3′, la, 5″, 3c, 3s, 5″, 1″″. Its distinct cell shape and the thecal plate arrangement indicate affinity to the monotypic genus Roscoffia. Roscoffia minor is distinguished from Roscoffia capitata, the type species, by its smaller size and the possession of a finger-like apical projection. The thecal arrangement of the epitheca is similar to those of the members of the family Podolampaceae, while the hypothecal arrangement is the same as that of members of the subfamily Diplopsalioideae (family Congruentidiaceae). The organism seems to be positioned somewhere intermediate between these two families, but the family to which this dinoflagellate should be affiliated could not be determined. 相似文献
88.
T. R. Mahalingam S. Vijayalakshmi R. Krishna Prabhu A. Thiruvengadasami Ann Wilber C. K. Mathews K. Radha Shanmugasundaram 《Biological trace element research》1997,57(3):191-206
Blood is one of the widely used specimens for biological trace element research because of its biological significance and
ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements.
For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of
blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied
for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis
of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission
spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have
also been discussed. 相似文献
89.
Abstract Ultrastructural and physiological characteristics of the C3-C4 intermediate Neurachne minor S. T. Blake (Poaceae) are compared with those of C3 and C4 relatives, and C3-C4Panicum milioides Nees ex Trin. N. minor consistently exhibits very low CO2 compensation points (τ: 1.0, usually 0.3–0.6 Pa) yet has C3-like δ13C values. CO2 assimilation rates (A) respond like those of C3 plants to a decrease in O2 partial pressure (2 × 104–1.9 × 103 Pa) at ambient CO2 levels, but this response is progressively attenuated until negligible at very low CO2. By contrast, other species of the Neurachneae are clearly either C4 (two spp.) or C3 (seven spp.). For plants grown and measured at different photon flux densities (PFDs), τ for N. minor and P. milioides increases from 0.5 to 1.0, and from 1.0 to 2.1 Pa, respectively, as PFD is decreased from 1860 to 460 μmol m?2s?1. In N. minor, the O2 response of τ is either biphasic as in P. milioides, but much diminished and with a higher transition point, or is very C4-like. As in C4 relatives, inner sheath cells contain numerous chloroplasts. Their walls possess a suberized lamella, which may make them more CO2-tight than bundle sheath cells of P. milioides, contributing to the almost C4-like τ characteristics of N. minor. The biochemical basis of C3-C4 intermediacy is considered. 相似文献
90.
Kirk Hayenga Charles Hedgcoth Mary Harrison Victor K. Lin B. J. Ortwerth 《Molecular and cellular biochemistry》1986,71(1):25-30
Summary Mouse lymphoma cells have three major isoaccepting lysine tRNAs. Two of these isoacceptors, tRNA2
Lys and tRNA4
Lys, were sequenced by rapid gel or chromatogram readout methods. They have the same primary sequence but differ in two modified nucleotides. tRNA4
Lys has an unmodified uridine replacing one dihydrouridine and an unidentified nucleotide, t6A*, replacing t6A. This unidentified nucleotide is not a hypomodified form of t6A. Thus, tRNA4ys is not a simple precursor of tRNA2
Lys. Both tRNAs have an unidentified nucleotide, U**, in the third position of the anticodon. Also, partial sequences of minor homologs of tRNA2
Lys and tRNA4
Lys were obtained. The distinctions between tRNA2
Lys and tRNA4
Lys may be part of significant cellular roles as illustrated by the differential effects of these isoacceptors on the synthesis by lysyl-tRNA synthetase of diadenosine-5,5-P1,P4-tetraphosphate, a putative signal in DNA replication. 相似文献