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91.
In the vertebrate CNS, glycine acts as an inhibitory neurotransmitter and as the obligatory coagonist of glutamate at N-methyl-d-aspartate receptors. These roles depend on extracellular glycine levels, regulated by Na+/Cl−-dependent transporters GLYT1, present mainly in glial cells, and GLYT2, predominantly neuronal. In Bergmann glia, GLYT1 mediates
both, glycine uptake and efflux, which, in turn, influences excitatory neurotransmission at Purkinje cell synapses. The biochemical
properties of GLYTs and their regulation by signaling pathways in these cells are largely unknown. We characterized Gly uptake
in confluent primary cultures of Bergmann glia from chick cerebellum. Transport was found to be energy- and Na+-dependent, and was resolved into a high (Km=25 μM) and a low affinity (Km=1.1 mM) components identified as GLYT1 and transport
System A, respectively. Results show that high affinity transport by GLYT1 is regulated by calcium from intracellular stores,
calmodulin, and myosin light chain kinase through an actin cytoskeleton-mediated action.
Special issue dedicated to Dr. Simo S. Oja 相似文献
92.
Radial positions of centromeres of human chromosomes X, 1, and 19 were determined in the nuclei of primary fibroblasts before and after removal of 60%-80% of chromatin. It has been demonstrated that the specific radial positions of these centromeres (more central for the chromosome 19 centromere and more peripheral for the centromeres of chromosomes 1 and X) remain unchanged in chromatin-depleted nuclei. Additional digestion of nuclear RNA did not influence this specific distribution. These results strongly suggest that the characteristic organization of interphase chromosomes is supported by the proteinous nuclear matrix and is not maintained by simple repulsing of negatively charged chromosomes. 相似文献
93.
Accumulation of the carcinogenic mycotoxin aflatoxin B, has been reported from members of three different groups of Aspergilli (4) Aspergillus flavus, A. flavus var. parvisclerotigenus, A. parasiticus, A. toxicarius, A. nomius, A. pseudotamarii, A. zhaoqingensis, A. bombycis and from the ascomycete genus Petromyces (Aspergillus section Flavi), (2) Emericella astellata and E. venezuelensis from the ascomycete genus Emericella (Aspergillus section Nidulantes) and (3) Aspergillus ochraceoroseus from a new section proposed here: Aspergillus section Ochraceorosei. We here describe a new species, A. rambellii referable to Ochraceorosei, that accumulates very large amounts of sterigmatocystin, 3-O-methylsterigmatocystin and aflatoxin B1, but not any of the other known extrolites produced by members of Aspergillus section Flavi or Nidulantes. G type aflatoxins were only found in some of the species in Aspergillus section Flavi, while the B type aflatoxins are common in all three groups. Based on the cladistic analysis of nucleotide sequences of ITS1 and 2 and 5.8S, it appears that type G aflatoxin producers are paraphyletic and that section Ochraceorosei is a sister group to the sections Flavi, Circumdati and Cervini, with Emericella species being an outgroup to these sister groups. All aflatoxin producing members of section Flavi produce kojic acid and most species, except A. bombycis and A. pseudotamarii, produce aspergillic acid. Species in Flavi, that produce B type aflatoxins, but not G type aflatoxins, often produced cyclopiazonic acid. No strain was found which produce both G type aflatoxins and cyclopiazonic acid. It was confirmed that some strains of A. flavus var. columnaris produce aflatoxin B2, but this extrolite was not detected in the ex type strain of that variety. A. flavus var. parvisclerotigenus is raised to species level based on the specific combination of small sclerotia, profile of extrolites and rDNA sequence differences. A. zhaoqingensis is regarded as a synonym of A. nomius, while A. toxicarius resembles A. parasiticus but differs with at least three base pair differences. At least 10 Aspergillus species can be recognized which are able to biosynthesize aflatoxins, and they are placed in three very different clades. 相似文献
94.
Non-linear cancer classification using a modified radial basis function classification algorithm 总被引:1,自引:0,他引:1
Summary This paper proposes a modified radial basis function classification algorithm for non-linear cancer classification. In the
algorithm, a modified simulated annealing method is developed and combined with the linear least square and gradient paradigms
to optimize the structure of the radial basis function (RBF) classifier. The proposed algorithm can be adopted to perform
non-linear cancer classification based on gene expression profiles and applied to two microarray data sets involving various
human tumor classes: (1) Normal versus colon tumor; (2) acute myeloid leukemia (AML) versus acute lymphoblastic leukemia (ALL).
Finally, accuracy and stability for the proposed algorithm are further demonstrated by comparing with the other cancer classification
algorithms. 相似文献
95.
Astur RS St Germain SA Baker EK Calhoun V Pearlson GD Constable RT 《Applied psychophysiology and biofeedback》2005,30(3):307-317
Numerous studies have shown that the hippocampus is critical for spatial memory. Within nonhuman research, a task often used to assess spatial memory is the radial arm maze. Because of the spatial nature of this task, this maze is often used to assess the function of the hippocampus. Our goal was to extrapolate this task to humans and examine whether healthy undergraduates utilize their hippocampus while performing a virtual reality version of the radial arm maze task. Thirteen undergraduates performed a virtual radial arm maze during functional magnetic resonance imaging. The brain maps of activity reveal bilateral hippocampal BOLD signal changes during the performance of this task. However, paradoxically, this BOLD signal change decreases during the spatial memory component of the task. Additionally, we note frontal cortex activity reflective of working memory circuits. These data reveal that, as predicted by the rodent literature, the hippocampus is involved in performing the virtual radial arm maze in humans. Hence, this virtual reality version may be used to assess the integrity of hippocampus so as to predict risk or severity in a variety of psychiatric disorders. 相似文献
96.
An in situ hybridization protocol for planarian embryos: monitoring myosin heavy chain gene expression 总被引:3,自引:3,他引:0
The monitoring of gene expression is fundamental for understanding developmental biology. Here we report a successful experimental
protocol for in situ hybridization in both whole-mount and sectioned planarian embryos. Conventional in situ hybridization
techniques in developmental biology are used on whole-mount preparations. However, given that the inherent lack of external
morphological markers in planarian embryos hinders the proper interpretation of gene expression data in whole-mount preparations,
here we used sectioned material. We discuss the advantages of sectioned versus whole-mount preparations, namely, better probe
penetration, improved tissue preservation, and the possibility to interpret gene expression in relation to internal morphological
markers such as the epidermis, the embryonic and definitive pharynges, and the gastrodermis. Optimal fixatives and embedding
methods for sectioning are also discussed.
A. Cardona and J. Fernández have contributed equally to this work. 相似文献
97.
DNA methylation plays a key role in the regulation of gene expression. The most common type of DNA modification consists of the methylation of cytosine in the CpG dinucleotide. At the present time, there is no method available for the prediction of DNA methylation sites. Therefore, in this study we have developed a support vector machine (SVM)-based method for the prediction of cytosine methylation in CpG dinucleotides. Initially a SVM module was developed from human data for the prediction of human-specific methylation sites. This module achieved a MCC and AUC of 0.501 and 0.814, respectively, when evaluated using a 5-fold cross-validation. The performance of this SVM-based module was better than the classifiers built using alternative machine learning and statistical algorithms including artificial neural networks, Bayesian statistics, and decision trees. Additional SVM modules were also developed based on mammalian- and vertebrate-specific methylation patterns. The SVM module based on human methylation patterns was used for genome-wide analysis of methylation sites. This analysis demonstrated that the percentage of methylated CpGs is higher in UTRs as compared to exonic and intronic regions of human genes. This method is available on line for public use under the name of Methylator at http://bio.dfci.harvard.edu/Methylator/. 相似文献
98.
Regulation of motile 9+2 cilia and flagella depends on interactions between radial spokes and a central pair apparatus. Although the central pair rotates during bend propagation in flagella of many organisms and rotation correlates with a twisted central pair structure, propulsive forces for central pair rotation and twist are unknown. Here we compared central pair conformation in straight, quiescent flagella to that in actively beating flagella using wild-type Chlamydomonas reinhardtii and mutants that lack radial spoke heads. Twists occur in quiescent flagella in both the presence and absence of spoke heads, indicating that spoke--central pair interactions are not needed to generate torque for twisting. Central pair orientation in propagating bends was also similar in wild type and spoke head mutant strains, thus orientation is a passive response to bend formation. These results indicate that bend propagation drives central pair rotation and suggest that dynein regulation by central pair--radial spoke interactions involves passive central pair reorientation to changes in bend plane. 相似文献
99.
100.
损伤冷蒿挥发性有机化合物(VOCs)成分分析及其对牧草根系生长发育的影响 总被引:1,自引:0,他引:1
采用GC-MS测定损伤冷蒿VOCs的主要成分,并通过生物测定的方法研究损伤冷蒿VOCs对牧草幼苗根系生长发育的影响。结果表明:损伤冷蒿释放30种VOCs,包含萜烯类、醇类、酯类、醛类和酮类等5类化合物,其中相对含量高于1%的化合物共占VOCs总量的97.37%,桉树脑含量最高(22.43%)。损伤冷蒿释放的VOCs极显著(P0.01)的抑制草木樨、苏丹草、披碱草和冰草幼根的伸长,以及苏丹草侧根与冰草须根的发育,抑制率分别为51.55%、55.34%、37.57%、48.68%、93.04%和25.00%;同时也极显著抑制4种牧草幼根生物量的积累(P0.01)。损伤冷蒿VOCs影响牧草根部中柱组织结构的分化,使草木樨中柱内木质部、韧皮部与形成层不能正常分化;苏丹草、披碱草和冰草的凯氏带发育不完整。由此可见,损伤冷蒿VOCs对牧草根系生长发育具有明显的抑制作用。 相似文献