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21.
Direct differentiation of somatic embryos occurs in high-frequency and at high density in response to 1.0 microM TDZ, on different regions-hypocotyl, epicotyl, cotyledonary-node, cotyledons and leaves-of intact seedlings of Azadirachta. One-week-old seedlings on this medium exhibited stress symptoms as visible by the loss of root formation and reduction in the elongation of hypocotyl and epicotyl. Globular somatic embryos were more abundant on hypocotyl, epicotyl, stem tip and leaves. The arrest of embryos at this stage was possibly due to their presence in high density. Well-developed somatic embryos were present on the cotyledons and the cotyledonary-node. These embryos on isolation and transfer to hormone-free medium regenerated readily to form plantlets. The possible role of stress in thidiazuron-induced somatic embryo formation is discussed. 相似文献
22.
In Population Genetics, two populations are distinguished from each other on the basis of the differences in the distributions
of the alleles at the locus or loci under consideration. These differences are measured by a “genetic distance” between the
two populations (not to be confused with genetic distance between two loci, which is based on recombination fractions) and
they play a major role in inferences at the population level. Several measures of genetic distance have been proposed by different
authors (Sanghvi 1953; Cavalli-Sforza and Edwards 1967; Jukes and Cantor 1969; Nei 1972; Kimura 1980; Reynoldset al 1983; reviews in Felsenstein 1991; Nei and Kumar 2000). Most of these measures are actually dissimilarity measures and not
mathematically true distance measures (B-Rao and Majumdar 1999). Independently, and much before the geneticists, statisticians
too were concerned with the idea of distinguishing between two (statistical) populations. In order to discriminate between
two populations on the basis of one or more characters, divergence measures like “Mahalanobis’D
2 statistic” or “Mahalanobis’ generalized distance” (1936) and “Bhattacharyya’s distance” (1943, 1946), Kullback-Leibler’s
divergence measure (1951) etc. have been proposed by statisticians. Mukherjee and Chattopadhyaya (1986) have mentioned measures
based on distances, association between two attributes and discrimination function. There are similarities between the distance
measures defined by applied scientists and by theoreticians. Felsenstein (1985) shows that three of the allele frequency-based
genetic distance measures were anticipated by Bhattacharyya (1946). Nei and Takezaki (1994) have also studied the effectiveness
of several genetic distance measures in the context of phylogenetic analysis, including Bhattacharyya’s distance measure. 相似文献
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Zhang H Berg JS Li Z Wang Y Lång P Sousa AD Bhaskar A Cheney RE Strömblad S 《Nature cell biology》2004,6(6):523-531
Unconventional myosins are actin-based motors with a growing number of attributed functions. Interestingly, it has been proposed that integrins are transported by unidentified myosins to facilitate cellular remodelling. Here we present an interaction between the unconventional myosin-X (Myo10) FERM (band 4.1/ezrin/radixin/moesin) domain and an NPXY motif within beta-integrin cytoplasmic domains. Importantly, knock-down of Myo10 by short interfering RNA impaired integrin function in cell adhesion, whereas overexpression of Myo10 stimulated the formation and elongation of filopodia in an integrin-dependent manner and relocalized integrins together with Myo10 to the tips of filopodia. This integrin relocalization and filopodia elongation did not occur with Myo10 mutants deficient in integrin binding or with a beta(1)-integrin point mutant deficient in Myo10 binding. Taken together, these results indicate that Myo10-mediated relocalization of integrins might serve to form adhesive structures and thereby promote filopodial extension. 相似文献
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Macroaffinity ligand-facilitated three-phase partitioning (MLFTPP) for purification of xylanase 总被引:2,自引:0,他引:2
It is shown that eudragit S-100, a copolymer of methylacrylic acid and methylmethacrylate, undergoes three-phase partitioning. It was found that 95% eudragit S-100 could be recovered as the interfacial precipitate by using 30% (w/v) ammonium sulfate, 1:1 ratio of t-butanol to polymer solution at 40 degrees C. Three-phase partitioning of proteins uses simultaneous addition of ammonium sulfate and t-butanol to precipitate proteins in an interfacial layer separating the aqueous phase and organic solvent. Exploiting the affinity of xylanases towards eudragit S-100, it was possible to purify xylanase from Aspergillus niger; 60% recovery of activity with 95-fold purification could be obtained by this process. The purified enzyme showed A single band on SDS-PAGE. The technique shows promise to develop into a general method that could be termed "macroaffinity ligand-facilitated three-phase partitioning (MLFTPP). 相似文献
30.
Kotekar A Bhisey R 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》2002,60(3):255-260
Several ethnic groups have been genotyped for polymorphisms at the CYP1A1 gene locus that encodes the enzyme that catalyzes the initial step in the metabolism of polycyclic aromatic hydrocarbons. Two of the CYP1A1 polymorphisms, namely, CYP1A1*2 and CYP1A1*3 are reported to cosegregate among the Japanese and to a lesser extent in Caucasians, but not in people of African descent. In the absence of such information in the Indian population, the frequency of the CYP1A1*2 polymorphism was determined in this study, using DNA samples from 649 ethnic Indians who had been earlier genotyped for the CYP1A1*3 polymorphism. Analysis of the combined genotype data revealed that the two polymorphisms cosegregate in the Indian population. 相似文献