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961.
缺乏叶绿素的油菜突变体的叶绿体组成和结构变化
赵云 杜林方* 杨胜洪 李世崇 张义正
(四川大学生命科学学院,成都610064) 相似文献
962.
We cultured retinal pigment epithelial (RPE) cells dissociated from adult newt eye and analyzed their voltage-gated ion channels during culture using whole-cell patch-clamp techniques. The results were compared with those of retinal neurons under identical experimental conditions. After 6–9 days in culture (early stage), > 60% of RPE cells developed voltage-gated Na+ and Ca2+ channels that were not observed in freshly dissociated RPE cells. The number of cells expressing Na+ channels and Na+ current density were high after 12–15 days in culture (intermediate stage), while the number of Ca2+ channel-expressing cells and Ca2+ current density were high after 20–30 days in culture (late stage). The activation voltage of the Na+ current in the RPE cells was similar to that in neurons. The voltage dependence of Na+ current inactivation was somewhat different between two cell types. The steepness of the inactivation curve tended to be less in cultured RPE cells than in neurons, and the half-inactivation voltage was about −54 mV for the RPE cells and −45 mV for neurons. The Ca2+ current expressed in cultured RPE cells was too small to detect without replacement of external Ca2+ with Ba2+. The Ba2+ current, like Ca2+ current in neurons, was enhanced by Bay-K 8644 and blocked by nicardipine. These results suggest that the RPE cells, like neurons, expressed L-type Ca2+ channels in culture. The possibility that the development of both Na2+ and Ca2+ channels in cultured RPE cells is a manifestation of the transdifferentiation of RPE cells into neurons is discussed. © 1997 John Wiley & Sons, Inc. J Neurobiol 32: 377–390, 1997. 相似文献
963.
David M. Parichy 《Journal of morphology》1998,237(1):53-67
Developmental relationships among characters are expected to bias patterns of morphological variation at the population level. Studies of character development thus can provide insights into processes of adaptation and the evolutionary diversification of morphologies. Here I use experimental manipulations to test whether larval and adult pigment patterns are coupled across metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum (Ambystomatidae). Previous investigations showed that the early larval pigment pattern depends on interactions between pigment cells and the lateral line sensory system. In contrast, the results of this study demonstrate that the major features of the adult pigment pattern develop largely independently of both the early larval pattern and the lateral lines. These results suggest that ontogenetic changes that occur across metamorphosis decouple larval and adult pigment patterns and could thereby facilitate independent evolutionary modifications to the patterns during different stages of the life cycle. J. Morphol. 237:53–67, 1998. © 1998 Wiley-Liss, Inc. 相似文献
964.
Yu Xia Yimeng Cui Aishan Wang Fangnan Liu Hai Chi Joshua H T Potter Joseph Williamson Xiaolan Chen Stephen J Rossiter Yang Liu 《Molecular biology and evolution》2021,38(12):5726
Rhodopsin comprises an opsin attached to a retinal chromophore and is the only visual pigment conferring dim-light vision in vertebrates. On activation by photons, the retinal group becomes detached from the opsin, which is then inactive until it is recharged. Of all vertebrate species, those that dive face unique visual challenges, experiencing rapid decreases in light level and hunting in near darkness. Here, we combine sequence analyses with functional assays to show that the rhodopsin pigments of four divergent lineages of deep-diving vertebrates have undergone convergent increases in their retinal release rate. We compare gene sequences and detect parallel amino acids between penguins and diving mammals and perform mutagenesis to show that a single critical residue fully explains the observed increases in retinal release rate in both the emperor penguin and beaked whale. At the same time, we find that other shared sites have no significant effect on retinal release, implying that convergence does not always signify adaptive significance. We propose that accelerated retinal release confers rapid rhodopsin recharging, enabling the visual systems of diving species to adjust quickly to changing light levels as they descend through the water column. This contrasts with nocturnal species, where adaptation to darkness has been attributed to slower retinal release rates. 相似文献
965.
棉铃虫幼虫小网膜细胞对光暗的反应 总被引:2,自引:1,他引:1
用透射电镜观察了棉铃虫Heliothis armigers(Hübnner)5龄幼虫小网膜细胞内一些细胞器的昼夜变化.其中色素颗粒,内质网,多泡体和多片层体变化特别显著.天亮3小时后,细胞内出现大量多泡体,多片层体和形态介于两者之间的细胞器.它们的数量随光照时间的延长而下降.天亮10小时后,大部分在细胞内消失.从天黑后2小时至天亮前2小时的细胞内含有大量的由滑而内质网构成的髓样体.天亮后它们在细胞内消失.昼夜交替还导致细胞内屏蔽色素颗粒周期性的水平和垂直移动.结合现有资料,我们对上述现象的意义进行了探讨. 相似文献
966.
The combined effects of osmotic stress and light on the generation of singlet oxygen (102) and its relation to the breakdown of photosynthetic pigments in leaves of hybrid rice (Oryza sativa L. subsp, indica cv. Shanyou 63) seedlings were studied under the condition of incubating the leaves with –0.8 MPa polyethylene glycol (PEG) solution. Under osmotic stress and increasing light intensity, the production of ¹O2 monitored as p-nitrosodimethylaniline (NDA) bleaching were increased in chloroplasts, degradation of chloro- phyll (Chl) and carotenoid (Car) were accelerated and Car loss preceded Chl causing a significant increase of Chl/Car ratio. A close correlation was observed between ¹O2 production and the contents of Chl, Car and malondialdehyde (MDA). Pretreatment with scavengers for ¹O2. such as β-carotene (β-Car) and histidine (His) reduced MDA content and retarded the degradation of photosynthetic pigments in rice leaves exposed to osmotic stress of -0.8 MPa and light intensity of 250 μmol · m- 2 · s-1, in contrast to that with photosensitizer riboflavin (RF). These results indicate that ¹O2 which generated in chloroplast from photosensitized reactions involving triplet Chl may play a significant role in the breakdown of photo- synthetic pigments and the preferential destruction of Car in the leaves under combined osmotic stress with light. 相似文献
967.
禽类的蛋壳具有白色、青色及褐色3种颜色, 特别是鸡和鸭的青壳蛋因外观美观, 口感好, 营养价值高, 蛋壳硬度和强度高于白壳蛋而具有较好的市场前景。但依据表型培育青壳鸡或鸭品系存在误选, 因而研究蛋壳颜色的形成及控制机理具有重要的理论及现实意义。文章主要介绍了禽类蛋壳颜色的种类、色素组成及其合成, 它的可遗传性、遗传力大小、遗传模式, 控制蛋壳颜色的基因数量及其相互之间的显隐性关系, 以期为揭示蛋壳颜色的形成机理提供参考。 相似文献
968.
E N Spudich R A Bogomolni J L Spudich 《Biochemical and biophysical research communications》1983,112(1):332-338
Leupeptin is a potent inhibitor of cathepsin B in vitro and is presumed to act in a similar manner in vivo. It is currently being used in several laboratories to examine the role of lysosomal proteinases such as cathepsin B in mouse models of muscular dystrophy. This report clearly demonstrates that leupeptin in adequate concentrations in vivo, is a potent stimulator of cathepsin B activity in striated muscle, heart, liver and kidney of the mouse. This paradoxical effect indicates that care is required in the interpretation of the results of the use of leupeptin as a cathepsin B inhibitor in vivo and that its use as an antiprotease for therapeutic purposes may be limited. Studies on CBZ-Phe-Ala-CHN2 demonstrated that this agent, when administered in vivo, inhibited Cathepsin B in the tissues assayed. 相似文献
969.
970.
Improvement of microalgal photosynthetic productivity by reducing the content of light harvesting pigment 总被引:3,自引:0,他引:3
Microalgal productivity was examined using both a wild type and a phycocyanin-deficient mutant of Synechocystis PCC 6714 (PD-1).
The culture was conducted at various light intensities under low and high cell densities in a continuous culture system. At
low light intensity, photosynthetic productivity was almost the same for both low and high cell densities. However, at higher
light intensities photosynthetic productivity was higher in mutant PD-1 than in the wild type. At 2000 μmol photon m−2 s−1 the productivity was 50% higher in mutant PD-1. This result is consistent with our first report (Nakajima & Ueda, 1997),
which showed that photosynthetic productivity can be improved by reducing the light harvesting pigment content in high cell
density cultures at high light intensities. It is concluded that the technology for reducing LHP content is a useful method
for improving photosynthetic productivity in algal mass production.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献