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81.
Animal diversity is shaped by the origin and diversification of new morphological structures. Many examples of evolutionary innovations are provided by male-specific traits involved in mating and sexual selection. The origin of new sex-specific characters requires the evolution of new regulatory interactions between sex-determining genes and genes that control spatial patterning and cell differentiation. Here, we show that sex-specific regulation of the HOX gene Sex combs reduced (Scr) is associated with the origin and evolution of the Drosophila sex comb — a novel and rapidly diversifying male-specific organ. In species that primitively lack sex combs, Scr expression shows little spatial modulation, whereas in species that have sex combs, Scr is upregulated in the presumptive sex comb region and is frequently sexually dimorphic. Phylogenetic analysis shows that sex-specific regulation of Scr has been gained and lost multiple times in Drosophila evolution and correlates with convergent origin of similar sex comb morphologies in several independent lineages. Some of these transitions occurred on microevolutionary timescales, indicating that HOX gene expression can evolve with surprising ease. This is the first example of a sex-specific regulation of a HOX gene contributing to the development and evolution of a secondary sexual trait. 相似文献
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Chorionic gonadotropin (CG) is a placental derived hormone that plays a crucial role in successful implantation and establishment of early pregnancy in the primates. The rhesus monkey was chosen as a model to understand the feasibility of developing human DNA immuno-contraceptive. The coding region of rhesus monkey CG -subunit (rmCG) was isolated by the TDRT-PCR method. The nucleotide sequence including the leader peptide was 499 nucleotide long and encoded 166 amino acids. In comparing with the previous known primates CG -subunits, the rmCG was the highest degree of homology with baboon CG -subunit at the deduced amino acid sequence (94%), 79.5% homology with human CG -subunit and 70.4% homology with marmoset monkey CG -subunit. The eukaryotic expression vector pCMV4-rmCG inserted full-coding cDNA sequence of rmCG was constructed, and the expression of rmCG -subunit in HeLa cells transient expressing system in vitro and BALB/c mice in vivo was determined. The results demonstrated that the recombinant PCMV4-rmCG eukaryotic expression vector could express rmCG -subunit in vitro and in vivo. 相似文献
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We present a nearest neighbor lattice model of the effects of modifiers on two-state enzyme catalysis of the reaction s ? p-We do not in general make the assumptions of the classical approach to cooperative catalysis that yield (1) adsorption isotherms of the same form as those for the corresponding equilibrium system and (2) a rate of the catalyzed reaction proportional to the number of occupied catalytic sites. Closed form results are obtained for two approximations, the Bragg-Williams and the quasi-chemical. The latter requires (l),but is exact for several simple cases, including the concerted model, under this condition. Under (1) it is found that an interaction between modifier and catalytic sites, whether attractive or repulsive, increases the magnitudes of the slopes of the adsorption isotherms but that interactions between identical sites (catalytic or modifier) increase these magnitudes if attractive and decrease them if repulsive. Thus, the former interaction allows for phase transitions if sufficiently attractive or repulsive, but the latter only if sufficiently attractive. Herein also lies the explanation for why the concerted model displays only “positive cooperativity”. It is further seen that it is not possible to classify a modifier as an activator or inhibitor of the catalyzed reaction solely on the basis of the sign of the interaction energy between catalytic and modifier sites. For agiven energy, the rate of the reaction may increase or decrease in response to the modifier, or it may respond biphasically. Similarly, the rate may respond biphasically to the activities of s or p, lead- ing to instabilities. Thus, possibilities of multiple nonequilibrium stationary states or spatio-temporal patterns are raised- 相似文献
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An NMR spectroscopy study ((31)P, (1)H, (13)C) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl alpha-D-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPP(g)). On the one hand, STTP(g) can react with a second alcohol functionality to give a crosslinked monophosphate. On the other hand, a monophosphate (grafted phosphate) could be obtained by alkaline degradation of STPP(g). NMR spectroscopy allows to detect the various species formed and to obtain the crosslinking density of STMP-polysaccharides hydrogels. 相似文献
88.
In the project “The hidden world of bacteria” students from six classes from high schools around Salzburg work for two years together with staff members of the Research Department for Limnology, Mondsee (University of Innsbruck). The aim is to isolate new bacterial strains from surrounding inland waters and to describe them as new species or higher taxonomic units. 相似文献
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