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931.
Cellular sensory systems often respond not to the absolute levels of inputs but to the fold-changes in inputs. Such a property is called fold-change detection (FCD) and is important for accurately sensing dynamic changes in environmental signals in the presence of fluctuations in their absolute levels. Previous studies defined FCD as input-scale invariance and proposed several biochemical models that achieve such a condition. Here, we prove that the previous FCD models can be approximated by a log-differentiator. Although the log-differentiator satisfies the input-scale invariance requirement, its response amplitude and response duration strongly depend on the input timescale. This creates limitations in the specificity and repeatability of detecting fold-changes in inputs. Nevertheless, FCD with specificity and repeatability by cells has been reported in the context of Drosophila wing development. Motivated by this fact and by extending previous FCD models, we here propose two possible mechanisms to achieve FCD with specificity and repeatability. One is the integrate-and-fire type: a system integrates the rate of temporal change in input and makes a response when the integrated value reaches a constant threshold, and this is followed by the reset of the integrated value. The other is the dynamic threshold type: a system response occurs when the input level reaches a threshold, whose value is multiplied by a certain constant after each response. These two mechanisms can be implemented biochemically by appropriately combining feed-forward and feedback loops. The main difference between the two models is their memory of input history; we discuss possible ways to distinguish between the two models experimentally. 相似文献
932.
933.
Hiraku Sasaki Eiichi Kawamoto Yoshikazu Tanaka Takuo Sawada Satoshi Kunita Ken-ichi Yagami 《Antonie van Leeuwenhoek》2009,95(4):311-317
Selected biochemical and genetic characteristics of the wild-type strains of Pasteurella pneumotropica isolated from mice and rats were investigated and compared in order to determine the significant differences among the isolates.
The isolates were divided into six groups on the basis of the patterns of carbon source utilization in the host rodents. The
genome sizes were determined by electrophoretic analysis, and the mean genome size of the isolates from mice was larger than
that of the isolates from rats (P < 0.05). Cluster analysis of the rpoB sequences discriminated five clusters; the differences might have correlated with the host associations. Principal component
analysis (PCA) based on both the biochemical and genetic characteristics revealed total 44 strains discriminated into three
groups comprising the host-dependent and host-independent groups. Although the P. pneumotropica isolates were mainly classified on the basis of the host rodents by the examinations, the existence of isolates that could
not be discriminated on the basis of the host rodents alone was confirmed by the PCA. These results indicated that the P. pneumotropica isolates could be further classified by taxonomic analysis and also suggested the existence of a host-independent group in
addition to the host-dependent groups. 相似文献
934.
Ken-ichi Kimura Noboru Kawaguchi Makoto Yoshihama Gosei Kawanishi 《Bioscience, biotechnology, and biochemistry》2013,77(11):3021-3022
The filamentous fungus Monascus pilosus was genetically transformed with a reporter plasmid, pMS-1.5hp, by aurintricarboxylic acid (ATA) treatment to obtain an efficient red-pigment producing mutant. The transformation efficiency of Monascus pilosus was higher with the ATA-treatment than with either a non-restriction-enzyme-mediated integration (REMI) or a REMI method. This valid and convenient random mutagenesis method shows that ATA can be applied in fungi for efficient genetic transformation. 相似文献
935.
Ken-ichi Amano Shin-ichi Yokota Tomonori Ishioka Shunji Hayashi Toru Kubota Nobuhiro Fujii 《Microbiology and immunology》1998,42(7):509-514
We have evaluated the use of proteinase K (PK)-treated cells isolated from Helicobacter pylori as lipopolysaccharide (LPS) antigens in an immunoblot assay and an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of H. pylori infection. The sera from patients with chronic gastritis, gastric ulcer, duodenal ulcer or gastric cancer, and from healthy adults with or without H. pylori infection were assayed with three commercial serodiagnostic kits (HM-CAP, Helico-G, and G.A.P. II) and novel methods relying on the use of PK-treated cells. The PK-treated cells used in these assays were selected on the basis of their possibility to possess a common epitope in the O-polysaccharides of H. pylori, which is known to be highly immunogenic in humans. Of the sera from these patients, 71-94% were positive with the commercial kits, 97% with immunoblot assay, and 90% with ELISA. On the other hand, of the healthy adults infected with H. pylori, 72-97% were positive with the commercial kits, 86% with immunoblot assay, and 72% with ELISA. PK-treated cells that did not contain the common epitope were unsuitable as an antigen for immunoblot assay or ELISA. Furthermore, the reactivity of these sera reacted specifically with H. pylori PK-treated cells but not with LPSs from other gram-negative bacteria, such as Campylobacter, Proteus, Bordetella, and Salmonella. These results demonstrate that the serological assays relying on the use of H. pylori PK-treated cells possessing a highly antigenic epitope are potentially useful as a serodiagnostic test for H. pylori infection. 相似文献
936.
937.
Shoichi Kawakami Kanae Mitsunaga Yara Yukie Kikuti Asako Ando Hidetoshi Inoko Ken-ichi Yamamura Kuniya Abe 《Mammalian genome》1998,9(11):874-880
Tctex3 showing restricted expression in male germ cells has been isolated during the process of chromosome walking in the mouse
t-complex region. The total sequence of Tctex3 cDNA predicts a protein of 580 amino acids with two C4HC3 type PHD fingers. The region containing this conserved motif is
shared among members of the Polycomblike proteins that include the mouse M96 and Drosophila Polycomblike. A partial cDNA for a human homolog of Tctex3, HUTEX3, has also been isolated. Mouse Tctex3 gene was mapped adjacent to Tsc2 gene on mouse Chromosome (Chr) 17, and HUTEX3 was located closely to HSET gene in the HLA class II region of chromosome 6.
Received: 10 April 1998 / Accepted: 22 June 1998 相似文献
938.
939.