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Extracellular proteases have been shown to be virulence factors in fungal pathogenicity toward insects. We examined the production
of extracellular proteases, subtilisin-like activity (Pr1) and trypsin-like activity (Pr2), by Beauveria bassiana CG425, which is a fungus of interest for control of the grasshopper Rhammatocerus schistocercoides. To access the role of these proteases during infection of R. schistocercoides, we analyzed their secretion during fungus growth either in nitrate-medium or in cuticle-containing medium supplemented with
different amino acids. The enhancing effect of cuticle on Pr1 and Pr2 production suggests that these protease types may be
specifically induced by components of the grasshopper cuticle. In medium supplemented with methionine a high level of Pr1
was observed. The remaining amino acids tested did not induce the protease to the levels seen with cuticle. The amino acid
methionine seems to play a regulatory role in Pr1 secretion by B. bassiana, since both induction and repression seem to be dependent on the concentration of the amino acid present in the culture medium. 相似文献
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75.
Rangarajan ES Ruane KM Sulea T Watson DC Proteau A Leclerc S Cygler M Matte A Young NM 《Biochemistry》2008,47(7):1827-1836
Campylobacter jejuni is highly unusual among bacteria in forming N-linked glycoproteins. The heptasaccharide produced by its pgl system is attached to protein Asn through its terminal 2,4-diacetamido-2,4,6-trideoxy-d-Glc (QuiNAc4NAc or N,N'-diacetylbacillosamine) moiety. The crucial, last part of this sugar's synthesis is the acetylation of UDP-2-acetamido-4-amino-2,4,6-trideoxy-d-Glc by the enzyme PglD, with acetyl-CoA as a cosubstrate. We have determined the crystal structures of PglD in CoA-bound and unbound forms, refined to 1.8 and 1.75 A resolution, respectively. PglD is a trimer of subunits each comprised of two domains, an N-terminal alpha/beta-domain and a C-terminal left-handed beta-helix. Few structural differences accompany CoA binding, except in the C-terminal region following the beta-helix (residues 189-195), which adopts an extended structure in the unbound form and folds to extend the beta-helix upon binding CoA. Computational molecular docking suggests a different mode of nucleotide-sugar binding with respect to the acetyl-CoA donor, with the molecules arranged in an "L-shape", compared with the "in-line" orientation in related enzymes. Modeling indicates that the oxyanion intermediate would be stabilized by the NH group of Gly143', with His125' the most likely residue to function as a general base, removing H+ from the amino group prior to nucleophilic attack at the carbonyl carbon of acetyl-CoA. Site-specific mutations of active site residues confirmed the importance of His125', Glu124', and Asn118. We conclude that Asn118 exerts its function by stabilizing the intricate hydrogen bonding network within the active site and that Glu124' may function to increase the pKa of the putative general base, His125'. 相似文献
76.
Dagmar Malun Niels Plath Martin Giurfa Ariane D. Moseleit Uli Müller 《Developmental neurobiology》2002,50(1):31-44
Hydroxyurea (HU) treatment of first instar honeybee larvae was previously shown to cause mushroom body (MB) ablations. Predominantly, either one or both median MB subunits were ablated. This prompted us to analyze the effects of asymmetrical or symmetrical HU‐induced MB ablation on both the morphology of the brain and on the level of three proteins (synapsin, PKA RII, and PKC), which are considered to play a role in synaptic plasticity, learning, and memory. In brains with one median MB subunit missing the volume of the overall MB calyx neuropil in the lesioned side was diminished by 35%. This strong reduction occurred although the remaining lateral MB calyx of the lesioned brain side was found to be significantly larger than that of the intact side. Accordingly, in brains with both median MB subunits missing the size of the remaining lateral calyces increased. The various types of MB ablation differentially affected the amounts of synapsin, PKA RII, and PKC expressed in the central brain. In animals with bilateral and thus symmetrical MB ablation (both median calyces ablated) the protein amount was found to be similar to that in control animals. However, unilateral MB ablation causes an increase in the amounts of the tested proteins in the intact brain side, while the levels in the ablated side were the same as in control animals. These findings not only show that HU‐induced ablation of MB subunits is accompanied by volume changes and by changes in protein expression, but also suggest that these processes are highly regulated between the brain sides. The latter is of general importance in understanding the potential contribution of the MB subunits to learning and memory and their interaction between the brain sides. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 31–44, 2002 相似文献
77.
Dagmar Malun Niels Plath Martin Giurfa Ariane D Moseleit Uli Müller 《Journal of neurobiology》2002,50(1):31-44
Hydroxyurea (HU) treatment of first instar honeybee larvae was previously shown to cause mushroom body (MB) ablations. Predominantly, either one or both median MB subunits were ablated. This prompted us to analyze the effects of asymmetrical or symmetrical HU-induced MB ablation on both the morphology of the brain and on the level of three proteins (synapsin, PKA RII, and PKC), which are considered to play a role in synaptic plasticity, learning, and memory. In brains with one median MB subunit missing the volume of the overall MB calyx neuropil in the lesioned side was diminished by 35%. This strong reduction occurred although the remaining lateral MB calyx of the lesioned brain side was found to be significantly larger than that of the intact side. Accordingly, in brains with both median MB subunits missing the size of the remaining lateral calyces increased. The various types of MB ablation differentially affected the amounts of synapsin, PKA RII, and PKC expressed in the central brain. In animals with bilateral and thus symmetrical MB ablation (both median calyces ablated) the protein amount was found to be similar to that in control animals. However, unilateral MB ablation causes an increase in the amounts of the tested proteins in the intact brain side, while the levels in the ablated side were the same as in control animals. These findings not only show that HU-induced ablation of MB subunits is accompanied by volume changes and by changes in protein expression, but also suggest that these processes are highly regulated between the brain sides. The latter is of general importance in understanding the potential contribution of the MB subunits to learning and memory and their interaction between the brain sides. 相似文献
78.
Prokaryotic mobile elements have traditionally been classified as bacteriophages, plasmids, and transposons. We propose here a global classification of these and other bacterial and archaeal mobile elements based on their modular structure. This would allow for setting up interconnected databases where mobile elements could be stored as combinations of functional modules. Such a database would be very helpful. It would, for instance, allow for analyzing the phylogeny of individual blocks within an element, to understand how modules get associated and properly express the functions they carry in various bacterial hosts. Modules of practical importance, as for instance those that encode toxins or other virulence factors, could be identified and compared, and probes devised to test bacterial populations for the presence of such modules. 相似文献
79.
Shereen Hasan Ghamartaj Hosseini Marc Princivalle Ji-Cui Dong Daniela Birsan Cristina Cagide Ariane I de Agostini 《Biology of reproduction》2002,66(1):144-158
During the reproductive cycle, ovarian follicles undergo major tissue-remodeling involving vascular changes and proteolysis. Anticoagulant heparan sulfate proteoglycans (aHSPGs) are expressed by granulosa cells during the development of the ovarian follicle. The function of aHSPGs in the ovary is unknown, but they might be involved in proteolysis control through binding and activation of serine protease inhibitors. To identify functional interactions between aHSPGs and heparin-binding protease inhibitors in the follicle, we have coordinately localized aHSPGs, antithrombin III, protease nexin-1, and plasminogen activator inhibitor-1 in the rat ovary during natural and gonadotropin-stimulated cycles. Anticoagulant HSPGs were visualized by autoradiography of cryosections incubated with 125I-antithrombin III, and protease inhibitors were assessed by immunohistochemistry and Northern blot hybridization. Anticoagulant HSPGs were expressed in follicles before ovulation, were transiently decreased in postovulatory follicles, and were abundant in the corpus luteum, mainly on capillaries. Anticoagulant HSPGs were colocalized with protease nexin-1 in follicles from the early antral stage until ovulation, with antithrombin III in the preovulatory stage and after ovulation, and with plasminogen activator inhibitor-1 in the corpus luteum. These data demonstrate that aHSPGs are critically expressed in the ovary to interact sequentially with protease nexin-1, antithrombin III, and plasminogen activator inhibitor-1 during the cycle. The specificity of these inhibitors is shifted toward thrombin inhibition in the presence of heparin, suggesting that aHSPGs direct their action to control fibrin deposition in the follicle. The occupation of aHSPGs antithrombin-binding sites by mutant R393C antithrombin III, injected in the ovarian bursa, decreased ovulation efficiency, further supporting the involvement of aHSPGs in the ovulation process. 相似文献
80.
Ariane Bernard-Laurent Claire Anceau Thierry Faivre Jean-Pierre Serres Sophie Tangis 《Bird Study》2017,64(4):513-522
Capsule: Double-nesting occurs frequently in Rock Partridges Alectoris graeca living in the southern French Alps.Aims: To investigate reproductive parameters of a Rock Partridge Alectoris graeca population.Methods: The reproductive behaviour of 62 radio-tagged birds was monitored during the breeding seasons 2012–16, to record breeding phenology, clutch sizes, hatching success, nest survival and parental care.Results: Double-nesting behaviour in the Rock Partridge was confirmed for the first time. Participation in incubation was similar for males and females (86% versus 70%). Clutch size was larger for nests incubated by males (11.0?±?1.6 eggs) than by females (9.5?±?1.2). Male nest survival rate (0.37) tended to be lower than female nest survival rate (0.62), although the difference was not significant. No significant difference was detected between male and female hatching success. Nest failures were caused by mammals taking the eggs (78%) or predation of the incubating parent (13%). Some circumstantial evidence suggests that occurrence of double-nesting behaviour could depend on previous winter and spring weather influencing the body condition of females. The reproductive biology of the Rock Partridge contrasts in some breeding traits with Red-legged Partridge and natural partridge hybrids, possibly due to climatic differences between habitats.Conclusion: Confirmation of double-nesting in Rock Partridges indicates that climatic constraints inherent to its mountain environment do not act as an impediment to this behaviour. Variation in weather conditions between years could influence the annual occurrence of double-nesting. 相似文献