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131.
Members of four sympatric species of Eupomacentrus carry out reproductive activities at the same time of the year and produce similar pulsed courtship sounds. Such sounds are known to facilitate courtship among conspecifics. Consequently, members of the four species in the field and in the laboratory were tested with the various sounds to determine if they could distinguish their own species sounds from those produced by congeners. The differential responses clearly demonstrate species specific recognition by sound and indicate that the pulse interval and the number of pulses per sound are the important parameters for this recognition.  相似文献   
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Katz E  Lagunes PM  Riov J  Weiss D  Goldschmidt EE 《Planta》2004,219(2):243-252
Mature citrus fruits, which are classified as non-climacteric, evolve very low amounts of ethylene during ripening but respond to exogenous ethylene by ripening-related pigment changes and accelerated respiration. In the present study we show that young citrus fruitlets attached to the tree produce high levels of ethylene, which decrease dramatically towards maturation. Upon harvest, fruitlets exhibited a climacteric-like rise in ethylene production, preceded by induction of the genes for 1-aminocyclopropane-1-carboxylate (ACC) synthase 1 (CsACS1), ACC oxidase 1 (CsACO1) and the ethylene receptor CsERS1. This induction was advanced and augmented by exogenous ethylene or propylene, indicating an autocatalytic system II-like ethylene biosynthesis. In mature, detached fruit, very low rates of ethylene production were associated with constitutive expression of the ACC synthase 2 (CsACS2) and ethylene receptor CsETR1 genes (system I). CsACS1 gene expression was undetectable at this stage, even following ethylene or propylene treatment, and CsERS1 gene expression remained constant, indicating that no autocatalytic response had occurred. The transition from system II-like behavior of young fruitlets to system I behavior appears to be under developmental control.Abbreviations ACC 1-Aminocyclopropane-1-carboxylate - CsACS1, CsACS2 ACC synthase - CsACO1 ACC oxidase - CsERS1, CsETR1 Ethylene receptors - DAFB Days after full bloom - 1-MCP 1-Methylcyclopropene  相似文献   
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Summary. Central neural damage caused by L-cysteine (L-Cys) was first reported more than 30 years ago. Nevertheless, the exact mechanisms of L-Cys-mediated neurotoxicity are still unclear. Preliminary study in mice demonstrated that, following L-Cys injection, animals developed tachypnea, tremor, convulsions, and death in conjunction with documented hypoglycemia. The aim of the present study was to further investigate the mechanism of L-Cys-mediated hypoglycemic effect and neural damage. Neonatal ICR mice (n=6) were injected with L-Cys (0.5–1.5mg/g body weight [BW]), and their blood glucose and insulin levels were determined up to 90min following the injection. Experiments were repeated in chemically (streptozotocin [STZ]) pancreatectomized animals. Brain histology was assessed. Mice injected with L-Cys exhibited dose-dependent neurotoxicity and higher mortality as compared with controls. L-Cys (1.2–1.5mg/g BW) caused severe hypoglycemia (glucose<42mg/dl) (P<0.001). In STZ-treated (diabetic) animals, L-Cys (1.5mg/g BW) increased plasma insulin levels 2.3-fold and decreased serum glucose levels by 50% (P<0.01). Brain histology revealed destruction of as much as 51% of hippocampal neurons in the L-Cys-treated mice but not in the glucose-resuscitated animals. These findings suggest that L-Cys injection can cause pronounced hypoglycemia and central neural damage which is glucose reversible. Since L-Cys is chemically different from the other excitatory amino acids (glutamate and aspartate), L-Cys-mediated neurotoxicity may be connected to its hypoglycemic effect.  相似文献   
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Amyloid fibril formation is the hallmark of major human maladies including Alzheimer's disease, type II diabetes, and prion diseases. Prion-like phenomena were also observed in yeast. Although not evolutionarily related, one similarity between the animal PrP and the yeast Sup35 prion proteins is the occurrence of short peptide repeats that are assumed to play a key role in the assembly of the amyloid structures. It was recently demonstrated that typical amyloid fibril formation is associated with biofilm formation by Escherichia coli. Here, we note the functional and structural similarity between oligopeptide repeats of the major curli protein and those of animal and yeast prions. We demonstrate that synthetic peptides corresponding to the repeats form fibrillar structures. Furthermore, conjugation of beta-breaker elements to the prion-like repeat significantly inhibits amyloid formation and cell invasion of curli-expressing bacteria. This implies a functional role of the repeat in the self-assembly of the fibrils. Since mammal prion, yeast prion, and curli protein are evolutionarily distinct, the conserved peptide repeats most likely define an optimized self-association motif that was independently evolved by diverse systems.  相似文献   
138.
The use of oligonucleotide-assisted cleavage and ligation (ONCL), a novel approach to the capture of gene repertoires, in the construction of a phage-display immune antibody library is described. ONCL begins with rapid amplification of cDNA ends to amplify all members equally. A single, specific cut near 5′ and/or 3′ end of each gene fragment (in single stranded form) is facilitated by hybridization with an appropriate oligonucleotide adapter. Directional cloning of targeted DNA is accomplished by ligation of a partially duplex DNA molecule (containing suitable restriction sites) and amplification with primers in constant regions. To demonstrate utility and reliability of ONCL, a human antibody repertoire was cloned from IgG mRNA extracted from human B-lymphocytes engrafted in Trimera mice. These mice were transplanted with peripheral blood lymphocytes from Candida albicans infected individuals and subsequently immunized with C.albicans glyceraldehyde-3-phosphate dehydrogenase (GAPDH). DNA sequencing showed that ONCL resulted in efficient capture of gene repertoires. Indeed, full representation of all VH families/segments was observed showing that ONCL did not introduce cloning biases for or against any VH family. We validated the efficiency of ONCL by creating a functional Fab phage-display library with a size of 3.3 × 1010 and by selecting five unique Fabs against GAPDH antigen.  相似文献   
139.
Tombola F  Pathak MM  Isacoff EY 《Neuron》2005,48(5):719-725
Despite tremendous progress in the study of voltage-gated channels, the molecular mechanism underlying voltage sensing has remained a matter of debate. We review five new studies that make major progress in the field. The studies employ a battery of distinct approaches that have the common aim of measuring the motion of the voltage sensor. We interpret the results in light of the recent crystal structure of the mammalian potassium channel Kv1.2. We focus on the transmembrane movement of the voltage sensor as a key element to the detection of membrane potential and to the control of channel gating.  相似文献   
140.
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