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991.
Growth-related traits, such as greater height, greater biomass, faster growth rate and early flowering, are thought to enhance competitiveness of agricultural weeds. However, weedy rice, a conspecific weed of cultivated rice (Oryza sativa L.), displays variation for growth traits. In the United States, separately evolved weedy rice groups have been shown to share genomic identity with exotic domesticated cultivars. Through a common garden experiment, we investigated whether growth trait divergence has occurred among U.S. weeds and their putative cultivated progenitors. We also determined polymorphism patterns in the growth candidate gene, SD1, to assess its possible role in the evolution of divergent phenotypes. We found considerable growth trait variation among weed groups, suggesting that growth trait convergence is not evident among weedy populations. Phenotypic divergence of weedy rice from cultivated ancestors is most apparent for flowering time. Introgression of a chromosomal block containing the SD1 allele from tropical japonica, the predominant U.S. rice cultivar, was detected in one weedy rice population and is associated with a change in growth patterns in this group. This study demonstrates the role of introgressive hybridization in evolutionary divergence of an important weed. 相似文献
992.
A key question in many genetic studies on marine organisms is how to interpret a low but statistically significant level of genetic differentiation. Do such observations reflect a real phenomenon, or are they caused by confounding factors such as unrepresentative sampling or selective forces acting on the marker loci? Further, are low levels of differentiation biologically trivial, or can they represent a meaningful and perhaps important finding? We explored these issues in an empirical study on coastal Atlantic cod, combining temporally replicated genetic samples over a 10‐year period with an extensive capture–mark–recapture study of individual mobility and population size. The genetic analyses revealed a pattern of differentiation between the inner part of the fjord and the open skerries area at the fjord entrance. Overall, genetic differentiation was weak (average FST = 0.0037), but nevertheless highly statistical significant and did not depend on particular loci that could be subject to selection. This spatial component dominated over temporal change, and temporal replicates clustered together throughout the 10‐year period. Consistent with genetic results, the majority of the recaptured fish were found close to the point of release, with <1% of recaptured individuals dispersing between the inner fjord and outer skerries. We conclude that low levels of genetic differentiation in this marine fish can indeed be biologically meaningful, corresponding to separate, temporally persistent, local populations. We estimated the genetically effective sizes (Ne) of the two coastal cod populations to 198 and 542 and found a Ne/N (spawner) ratio of 0.14. 相似文献
993.
Kulahin N Kristensen O Rasmussen KK Olsen L Rydberg P Vestergaard B Kastrup JS Berezin V Bock E Walmod PS Gajhede M 《Structure (London, England : 1993)》2011,19(2):203-211
The ectodomain of olfactory cell adhesion molecule (OCAM/NCAM2/RNCAM) consists of five immunoglobulin (Ig) domains (IgI-V), followed by two fibronectin-type 3 (Fn3) domains (Fn3I-II). A complete structural model of the entire ectodomain of human OCAM has been assembled from crystal structures of six recombinant proteins corresponding to different regions of the ectodomain. The model is the longest experimentally based composite structural model of an entire IgCAM ectodomain. It displays an essentially linear arrangement of IgI-V, followed by bends between IgV and Fn3I and between Fn3I and Fn3II. Proteins containing IgI-IgII domains formed stable homodimers in solution and in crystals. Dimerization could be disrupted in?vitro by mutations in the dimer interface region. In conjunction with the bent ectodomain conformation, which can position IgI-V parallel with the cell surface, the IgI-IgII dimerization enables OCAM-mediated trans-interactions with an intercellular distance of about 20?nm, which is consistent with that observed in synapses. 相似文献
994.
995.
Kevin Huvaere Karsten Olsen Mogens L Andersen Leif H Skibsted Arne Heyerick Denis De Keukeleire 《Photochemical & photobiological sciences》2004,3(4):337-340
Isohumulones, the bitter principles in beer, are decomposed by light-induced reactions, thereby adversely affecting beer quality. Upon absorption of visible light, riboflavin is excited and interacts with isohumulones, as well as with oxidized and reduced derivatives thereof. Reaction kinetics were investigated by laser flash photolysis at 355 nm and at 440 nm, and analysis of kinetic data afforded detailed insights into the reaction mechanism. 相似文献
996.
Jørgen A. Mølmann A. T. Berhanu Svein K. Stormo Arild Ernstsen Olavi Junttila Jorunn E. Olsen 《Physiologia plantarum》2003,119(2):278-286
Application experiments have suggested that short‐day‐induced cessation of elongation growth in trees is caused by photoperiodic regulation of the conversion of gibberellin GA19 to GA20. In the present study we examined further the photoperiodic control of GA metabolism in trees with focus on the conversion of GA19 in Salix pentandra, hybrid aspen (Populus tremula × tremuloides) and silver birch (Betula pendula) using [17,17‐2H2]‐GA19 or unlabelled GAs in application studies. GA20 and GA1 were able to restore growth also in hybrid aspen and silver birch under short days (SD), whereas GA19 had no or only a very small activity. Contrary to hybrid aspen and S. pentandra, the activity of GA20 in silver birch was significantly lower than that of GA1. Gas chromatography‐mass spectrometry (GC‐MS) analysis revealed a smaller turnover of [2H2]‐GA19 in SD than in long days (LD) in hybrid aspen. No such difference in turnover of [2H2]‐GA19 was observed in photoperiod‐insensitive hybrid aspen overexpressing PHYA. Application of unlabelled GAs to seedlings of S. pentandra, hybrid aspen and silver birch under SD followed by quantification of metabolites by GC‐MS analysis, showed that applied GA19 was not readily converted to GA20 and GA1. Although the sensitivity to GAs is also known to decrease under SD, the present data are in favour of a photoperiodic regulation of the metabolism of GA19in vivo in the woody species S. pentandra, hybrid aspen and silver birch. The data might also suggest that silver birch differs from S. pentandra and hybrid aspen by exhibiting a possible photoperiodic control also of the conversion of GA20 to GA1. 相似文献
997.
998.
Jens Kvist Nielsen Ole Olsen Lars Haastrup Pedersen Hilmer Sørensen 《Phytochemistry》1984,23(8):1741-1743
The cotyledons, leaves and inflorescences of the radish, Raphanus sativus, have been examined for their content of hydroxylated cinnamic acid malate esters. 2-O-(p-coumaroyl)-l-malate, 2-O-caffeoyl-l-malate and 2-O-feruloyl-l-malate were found to be quantitatively predominating compounds in the fraction of carboxylic acids isolated from radish leaves and inflorescences. Identifications were based on PC, TLC, HVE, GC, HPLC, UV and NMR spectroscopy. The l- or (2S)-configuration of malic acid released by hydrolysis from the esters was determined by using l-malate dehydrogenase. A combined column chromatography technique applied prior to HVE, HPLC and GC was useful for separating the malate esters from most other low MW plant constituents. The significance of the present investigation is briefly discussed in relation to the metabolism of phenolic constituents of glucosinolate-containing plants, and the effects of these compounds in relation to insect feeding behaviour. 相似文献
999.
1000.
Multiple paternity analysis in the thornback ray Raja clavata L 总被引:1,自引:0,他引:1
Skates (Rajidae) are characterized by slow growth rate, low fecundity, and late maturity and are thus considered to be vulnerable to exploitation. Although understanding mating systems and behavior are important for long-term conservation and fisheries management, this aspect of life history is poorly understood in skates. Using 5 highly polymorphic microsatellite loci, we analyzed egg clutches collected from 4 female Raja clavata captured in the wild to test for multiple paternity. Using the reconstructed multilocus genotypes method to explain the progeny genotype array, we showed that all 4 clutches were sired by a minimum of 4-6 fathers and, thus, female thornback rays are polyandrous. Whether polyandry in R. clavata is natural or a consequence of overexploitation remains uncertain. This is the first report of multiple paternity in a rajiform species and any oviparous elasmobranch. 相似文献