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111.
A novel role of the hedgehog pathway in lens regeneration 总被引:4,自引:0,他引:4
Tsonis PA Vergara MN Spence JR Madhavan M Kramer EL Call MK Santiago WG Vallance JE Robbins DJ Del Rio-Tsonis K 《Developmental biology》2004,267(2):450-461
Lens regeneration in the adult newt is a classic example of replacing a lost organ by the process of transdifferentiation. After lens removal, the pigmented epithelial cells of the dorsal iris proliferate and dedifferentiate to form a lens vesicle, which subsequently differentiates to form a new lens. In searching for factors that control this remarkable process, we investigated the expression and role of hedgehog pathway members. These molecules are known to affect retina and pigment epithelium morphogenesis and have been recently shown to be involved in repair processes. Here we show that Shh, Ihh, ptc-1, and ptc-2 are expressed during lens regeneration. The expression of Shh and Ihh is quite unique since these genes have never been detected in lens. Interestingly, both Shh and Ihh are only expressed in the regenerating and developing lens, but not in the intact lens. Interfering with the hedgehog pathway results in considerable inhibition of the process of lens regeneration, including decreased cell proliferation as well as interference with lens fiber differentiation in the regenerating lens vesicle. Down-regulation of ptc-1 was also observed when inhibiting the pathway. These results provide the first evidence of a novel role for the hedgehog pathway in specific regulation of the regenerating lens. 相似文献
112.
113.
J Kindermann Y El-Ayouti GJ Samuels CP Kubicek 《Fungal genetics and biology : FG & B》1998,24(3):298-309
Sequences of the internal transcribed spacer region 1 (ITS1) of the ribosomal DNA were used to determine the phylogenetic relationships of species of Trichoderma sect. Pachybasium. To this end, 85 strains-including all the available ex-type strains-were analyzed. Parsimony analysis demonstrated that the section is nonmonophyletic, distributing the 85 strains among three main groups that were supported by bootstrap values. Group A comprises two clades (A1 and A2), with A1 including T. polysporum, T. piluliferum, and T. minutisporum, while A2 included T. hamatum, T. pubescens, and T. strigosum in addition to species previously included in sect. Trichoderma (i.e., T. viride, T. atroviride, and T. koningii). The ex-type strain of T. fasciculatum formed a separate branch basal to clade A. Clade B contained the sect. Pachybasium members T. harzianum, T. fertile, T. croceum, T. longipile, T. strictipile, T. tomentosum, T. oblongisporum, T. flavofuscum, T. spirale, and the anamorphs of Hypocrea semiorbis and H. cf. gelatinosa. Sequence differences among clades A1, A2, and B were in the same order of magnitude as between each of them and T. longibrachiatum, which was used as an outgroup in these analyses. Sequence differences within clades A1, A2, and B were considerably smaller: in some cases (i.e., T. virens and T. flavofuscum; T. strictipile and H. cf. gelatinosa), the ITS1-sequences were identical, suggesting conspecifity. In other cases (e.g., T. crassum and T. longipile; T. harzianum, T. inhamatum, T. croceum, T. fertile, and H. semiorbis; T. hamatum and T. pubescens; and T. viride, T. atroviride, and T. koningii) differences were in the range of 1-3 nt only, suggesting a very close phylogenetic relationship. The sequence of a previously described aggressive mushroom competitor group of T. harzianum strains (Th2) was strikingly different from that of the ex-type strain of T. harzianum and closely related species and is likely to be a separate species. Copyright 1998 Academic Press. 相似文献
114.
Light quality affects morphology and polysaccharide yield and composition of Gelidium sesquipedale (Rhodophyceae) 总被引:3,自引:0,他引:3
Raquel Carmona Juan J. Vergara Marc Lahaye F. X. Niell 《Journal of applied phycology》1998,10(3):323-332
Morphology and polysaccharide characterization of Gelidium sesquipedale (Clem.) Bornet et Thuret were studied in cultures
grown under various light qualities. White light (WL), blue light (BL) and red light (RL) (all at photon fluence rate of 40
μmol m-2 s-1) were used for the study of morphological characteristics, and in addition yellow light (YL) for polysaccharide
characterization. RL and BL induced a proliferating growth, which resulted in bushy plants under RL. Cortical cells of BL-grown
plants were smaller and presented a higher density per unit area, whereas those of WL- and RL-grown alga were larger. Medullary
cells followed the inverse pattern. Light quality also affected polysaccharide yield and composition, with the yield being
higher under BL, RL or YL than WL. Most of the polysaccharide was extracted in distilled water at 100 °C, while a low amount
was solubilized at 22 °C and 120 °C. Extracts from BL-grown alga presented the highest galactan content. The starch concentration
was lower in extracts from RL-, BL- and YL-cultivated alga than in those from the initial plants. The degree of substitution
with methoxyl groups and precursor was very low in all the agar fractions, but fractions extracted from BL- and WL-grown alga
were more substituted by precursor. The highest sulfate content was reached under BL (about 9% w/w) and the highest 2-O-methyl-3,6-anhydro-L-galactose
and 6-O-methyl-D-galactose content were found in extracts from alga grown under YL.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
115.
Evidence about the potential of mobile marine invertebrates to act as algal spore dispersal agents is presently circumstantial. Using a field correlational and experimental protocol, our study tested the hypothesis that amphipods can increase the spore recruitment of the red alga Iridaea laminarioides Bory. Iridaea laminarioides spore recruitment onto glass slides was measured at a site with high amphipod abundance and a site with low density of amphipods. To evaluate the effect of an Ulva canopy on recruitment, replicated glass slides with and without a surrounding Ulva canopy were installed at both sites. The number of I. laminarioides spores recruited on the glass slides was four to eight times higher at the high amphipod abundance site than at the low density site. However, the presence of an Ulva canopy covering the glass slides did not significantly increase the recruitment of I. laminarioides. Because the abundance of I. laminarioides, the proportion of cystocarpic plants, and the percentage of open cystocarps only differed slightly between the low and high abundance amphipod sites, we suggest that the variation in recruitment between the sites is due to the differences in amphipod abundance (and their movements) and not to differences in spore production. Moreover, the presence of I. laminarioides cystocarps showing amphipod grazing scars was significantly higher at the high amphipod density site than at the low density site. 相似文献
116.
Augusta Amargier S. Abol-Ela S. Vergara G. Meynadier D. Martouret G. Croizier 《BioControl》1981,26(3):319-332
Résumé Une polyédrose nucléaire de la tordeuse de la pelure,Pandemis heparana
Denis & Schiffermuller (Lep.: Tortricidae) due à un baculovirus isolé dans un verger de pommiers en France est étudiée. Le baculovirus, uniquement actif sur les larves
nouvelles nées, induit un arrêt de développement des larves au stade L3 et une mortalité ultérieue des larves aux stades L5
et L6. L'étude en microscopie optique et en microscopie électronique des larves L5 et L6 présentant des sympt?mes très prononcés
de la viroise (début de paralysie et couleur blanchatre des segments abdominaux) montre que c'est essentiellement le tissu
adipeux et accessoirement certains hémocytes et quelques cellules de l'hypoderme qui sont le siège de la multiplication virale.
La morphogénèse virale dans les cellules du tissu adipeux est décrite en détail. Certains aspects de l'étude ultrastructurale
liés à la forme en massue des virions, au processus de cristallisation des polyèdres et à l'accumulation de masses fibrillaires
viro-induites sont discutés.
Summary A nuclear polyhedrosis virus infecting the torticidPandemis heparana Denis & Schiffermuller, collected in an apple-orchard in France was isolated and studied. The baculovirus is active only in the newly hatched larvae. It induces a delayed arrest of development in the L3 larvae and subsequently the death of L5 and L6 larvae. Study by light and electron microscopy of L5 and L6 larvae exhibiting very marked symptoms of the virus disease (early stages of paralysis and whitish colour of abdominal segments) shows that the site of multiplication of the virus is mainly located in the fat body cells and occasionally in some hemocytes or hypoderm cells. Virus morphogenesis within the fat body cells is described in detail. Some aspects of the ultrastructure such as clubbed virions, process of crystallization of polyhedral bodies and clumps of fibrous material induced by the virus, are discussed.相似文献
117.
118.
Juan A. Correa Juan C. Castilla Marco Ramírez Manuel Varas Nelson Lagos Sofia Vergara Alejandra Moenne Domingo Román Murray T. Brown 《Journal of applied phycology》1999,11(1):57-67
Results are presented of a long-term research programme on the effect of copper contamination on biota in Chilean coastal
waters. In spite of the magnitude of the copper mining tailings that affected Caleta Palito and surroundings in northern Chile,
the effects on the intertidal assemblages remain restricted to a small geographic area. Even within the affected area, the
effects are not homogeneous and there is evidence of active recovery in biological diversity in recent few years. Experimental
evidence suggests that the current low algal diversity and abundance is strongly influenced by herbivory, although chronic
effects of the discharges cannot be ruled out. Cellular changes in Enteromorpha compressa from the impacted area were characterised
by abnormal granules in the cytoplasm, though these granules did not contain detectable levels of copper or other heavy metals.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
119.
Nonglucosylated oligosaccharides are transferred to protein in MI8-5 Chinese hamster ovary cells 总被引:3,自引:2,他引:1
A CHO mutant MI8-5 was found to synthesize Man9-GlcNAc2-P-P-dolichol rather
than Glc3Man9GlcNAc2-P-P-dolichol as the oligosaccharide-lipid intermediate
in N-glycosylation of proteins. MI8-5 cells were incubated with labeled
mevalonate, and the prenol was found to be dolichol. The mannose-labeled
oligosaccharide released from oligosaccharide-lipid of MI8-5 cells was
analyzed by HPLC and alpha-mannosidase treatment, and the data were
consistent with a structure of Man9GlcNAc2. In addition, MI8-5 cells did
not incorporate radioactivity into oligosaccharide- lipid during an
incubation with tritiated galactose, again consistent with MI8-5 cells
synthesizing an unglucosylated oligosaccharide-lipid. MI8-5 cells had
parental levels of glucosylphosphoryldolichol synthase activity. However,
in two different assays, MI8-5 cells lacked dolichol-
P-Glc:Man9GlcNAc2-P-P-dolichol glucosyltransferase activity. MI8-5 cells
were found to synthesize glucosylated oligosaccharide after they were
transfected with Saccharomyces cerevisiae ALG 6, the gene for
dolichol-P-Glc:Man9GlcNAc2-P-P-dolichol glucosyltransferase. MI8-5 cells
were found to incorporate mannose into protein 2-fold slower than parental
cells and to approximately a 2-fold lesser extent.
相似文献
120.
Several Cape species of the genus Erica are known to present seeder and resprouter phenotypes, and this variation seems to have a genetic basis. Therefore, this genus provides ideal model systems for using to elucidate the evolution of nonsprouting or seeder and resprouter life-histories in woody, fire-recruiting plants. A simple simulation model was developed to identify, under life-history optimality, the ecological conditions (viz. rainfall conditions and fire frequency) that conferred a selective advantage to the seeder phenotype over the resprouter in a given Cape Erica species. The model illustrated that the seeder life-history was able to invade and replace a resprouter population only under a mild mediterranean climate, with short, moderate summer droughts. This simulation approach will contribute to a better understanding of the biogeographical pattern of seeder and resprouter lineages of one of the paradigmatic fynbos woody taxa throughout the Cape floristic region. 相似文献