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951.
The effects of magnitude and frequency of distraction forces on tissue regeneration in distraction osteogenesis of the mandible. 总被引:7,自引:0,他引:7
Peter A Kessler Hans A Merten Friedrich W Neukam J?rg Wiltfang 《Plastic and reconstructive surgery》2002,109(1):171-180
Callus distraction has become an accepted treatment procedure to lengthen hypoplastic mandibles in humans. For this purpose, extraoral and intraoral devices have been applied successfully. The effects of the distraction vector, distractor stability, and rate and frequency of callus distraction on the regenerating tissues have been examined in various studies. In an experimental animal trial on pigs (n = 12), a newly developed microhydraulic osteodistractor was tested. The animals were evenly assigned to two groups to perform a continuous and noncontinuous osteodistraction of the mandible. Initially, the forces necessary to distract the pig mandibles were recorded from a noncontinuous distraction procedure; the results were then used to perform continuous bone distraction. Besides testing the new distractor, the study proved that in continuous osteodistraction, intramembranous bone regeneration occurred, whereas in noncontinuous osteodistraction the bone regeneration process followed a chondroid ossification. In continuous osteodistraction, the bone regeneration proceeded at a higher speed with the lower distraction forces compared with noncontinuous distraction, thereby reducing the consolidation period. Clinical and microscopical results are presented. 相似文献
952.
Heike Lindner Sharon A. Kessler Lena M. Müller Hiroko Shimosato-Asano Aurélien Boisson-Dernier Ueli Grossniklaus 《PLoS biology》2015,13(4)
Pollen tube (PT) reception in flowering plants describes the crosstalk between the male and female gametophytes upon PT arrival at the synergid cells of the ovule. It leads to PT growth arrest, rupture, and sperm cell release, and is thus essential to ensure double fertilization. Here, we describe TURAN (TUN) and EVAN (EVN), two novel members of the PT reception pathway that is mediated by the FERONIA (FER) receptor-like kinase (RLK). Like fer, mutations in these two genes lead to PT overgrowth inside the female gametophyte (FG) without PT rupture. Mapping by next-generation sequencing, cytological analysis of reporter genes, and biochemical assays of glycoproteins in RNAi knockdown mutants revealed both genes to be involved in protein N-glycosylation in the endoplasmic reticulum (ER). TUN encodes a uridine diphosphate (UDP)-glycosyltransferase superfamily protein and EVN a dolichol kinase. In addition to their common role during PT reception in the synergids, both genes have distinct functions in the pollen: whereas EVN is essential for pollen development, TUN is required for PT growth and integrity by affecting the stability of the pollen-specific FER homologs ANXUR1 (ANX1) and ANX2. ANX1- and ANX2-YFP reporters are not expressed in tun pollen grains, but ANX1-YFP is degraded via the ER-associated degradation (ERAD) pathway, likely underlying the anx1/2-like premature PT rupture phenotype of tun mutants. Thus, as in animal sperm–egg interactions, protein glycosylation is essential for the interaction between the female and male gametophytes during PT reception to ensure fertilization and successful reproduction. 相似文献
953.
In a squirrel monkey (Saimiri sciureus), monitored clinically for five years, histopathological review revealed diffuse lymphoblastic lymphocytes infiltrating the thyroid, kidney, liver, pancreas, adrenal medulla, internal fat, extramedullary hematopoietic foci in the spleen and liver, and a mild chronic peritonitis. 相似文献
954.
S. Goda Sporn Merijn M. Bos Michael Kessler S. Robbert Gradstein 《Biodiversity and Conservation》2010,19(3):745-760
We studied species richness, composition and vertical distribution of epiphytic bryophytes in submontane rainforest of Central
Sulawesi. Bryophytes were sampled on eight canopy trees and on eight trees in the forest understorey. Microclimate was measured
at trunk bases and at crown bases. The total recorded number of 146 epiphytic bryophyte species is among the highest ever
reported for tropical forests and underlines the importance of the Malesian region as a global biodiversity hotspot. Species
composition differed significantly between understorey trees and canopy tree trunks on the one hand, and the forest canopy
on the other. Fourty-five percent of the bryophyte species were restricted to canopy tree crowns, 12% to the understorey.
Dendroid and fan-like species mainly occurred in the forest understorey whereas tufts were most species rich in the tree crowns.
The findings reflect the different microclimatic regimes and substrates found in the understorey and in the forest canopy.
The results indicate that assessments of the bryophyte diversity of tropical forests are inadequate when understorey trees
and tree crowns are excluded. 相似文献
955.
Nicole Mandl Marcus Lehnert Michael Kessler S. Robbert Gradstein 《Biodiversity and Conservation》2010,19(8):2359-2369
We present a first comparison of patterns of alpha and beta diversity of ferns, mosses, liverworts and macrolichens in neotropical
montane rainforests, and explore the question whether specific taxa may be used as surrogates for others. In three localities
in southern Ecuador, we surveyed terrestrial and epiphytic species assemblages in ridge and slope forests in 28 plots of 400 m2
each. The epiphytic habitat was significantly richer in ferns, liverworts, and macrolichens than the terrestrial habitat;
mosses, however, were primarily terrestrial. Alpha diversity of ferns and of liverworts was congruent in both habitats. Mosses
were similar to ferns and liverworts only in the epiphytic habitat. Macrolichens did not share patterns of alpha diversity
with any other group. Beta diversity of ferns, mosses and liverworts (lichens excluded due to low species richness) was similar
in the terrestrial habitat, but not in the epiphytic habitat. Our results demonstrate that patterns of alpha diversity of
the studied taxa cannot be used to predict patterns of beta diversity. Moreover, diversity patterns observed in epiphytes
are different from terrestrial plants. We noted a general coincidence in species patterns of liverworts and ferns. Diversity
patterns of macrolichens, in contrast, were completely independent from any other taxonomic group studied. 相似文献
956.
Permanent Genetic Resources added to Molecular Ecology Resources Database 1 April 2010 - 31 May 2010
Molecular Ecology Resources Primer Development Consortium Andree K Axtner J Bagley MJ Barlow EJ Beebee TJ Bennetzen JL Bermingham E Boisselier-Dubayle MC Bozarth CA Brooks CP Brown RP Catanese G Cavers S Ceron-Souza I Chak ST Chan MN Charles-Dominique P Chen CY Chen JD Chinchilla L DA Silva D Dafreville S Daunt F Delatte H Dorge T Duncan N Durand JD Duvernell D Estep M Fan S Fattahi R Villela OF Fong Y Fréville H Funes V Gallardo-Escarate C Ganeshaiah KN Ghaffari MR Girod C Gomez-Moliner BJ 《Molecular ecology resources》2010,10(6):1098-1105
This article documents the addition of 396 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anthocidaris crassispina, Aphis glycines, Argyrosomus regius, Astrocaryum sciophilum, Dasypus novemcinctus, Delomys sublineatus, Dermatemys mawii, Fundulus heteroclitus, Homalaspis plana, Jumellea rossii, Khaya senegalensis, Mugil cephalus, Neoceratitis cyanescens, Phalacrocorax aristotelis, Phytophthora infestans, Piper cordulatum, Pterocarpus indicus, Rana dalmatina, Rosa pulverulenta, Saxifraga oppositifolia, Scomber colias, Semecarpus kathalekanensis, Stichopus monotuberculatus, Striga hermonthica, Tarentola boettgeri and Thermophis baileyi. These loci were cross-tested on the following species: Aphis gossypii, Sooretamys angouya, Euryoryzomys russatus, Fundulus notatus, Fundulus olivaceus, Fundulus catenatus, Fundulus majalis, Jumellea fragrans, Jumellea triquetra Jumellea recta, Jumellea stenophylla, Liza richardsonii, Piper marginatum, Piper aequale, Piper darienensis, Piper dilatatum, Rana temporaria, Rana iberica, Rana pyrenaica, Semecarpus anacardium, Semecarpus auriculata, Semecarpus travancorica, Spondias acuminata, Holigarna grahamii, Holigarna beddomii, Mangifera indica, Anacardium occidentale, Tarentola delalandii, Tarentola caboverdianus and Thermophis zhaoermii. 相似文献
957.
958.
As for many other taxa, hummingbird diversity declines away from the equator, but the causes for this decline are still disputed
and might involve, among others, climatic factors or the availability of food resources. Because hummingbirds are one of the
classical examples for plant–animal coevolution, it has been proposed that the diversity of hummingbird assemblages might
depend on the diversity of food plants available. We tested this hypothesis by studying the hummingbird assemblages and their
food plants for 1 year at six sites along a 660-km-long transect in Bolivian lowland forests extending from the southernmost
Amazonian rain forests to dry Chaco forests. Hummingbird diversity was higher in the northern three sites as compared to the
southern ones, with an abrupt decline in species numbers and a corresponding change in taxonomic composition at the boundary
from evergreen to drought deciduous forests. Hummingbird diversity and abundance were only weakly correlated to climatic factors
or to the diversity of humming-visited flowers, but strongly to the seasonal abundance of flowers. The overlap in nectar diet
between hummingbird species depended on the number of plant species: when numerous species were available, the hummingbirds
segregated by feeding preferences, but when few flowers were available, all hummingbirds fed on the same plants. We conclude
that the local diversity of hummingbird species is not primarily determined by the diversity of food plants, but rather by
the abundance of flowers available at any given point in time. 相似文献
959.
960.
Richter K Moser S Hagn F Friedrich R Hainzl O Heller M Schlee S Kessler H Reinstein J Buchner J 《The Journal of biological chemistry》2006,281(16):11301-11311
The molecular chaperone Hsp90 is required for the folding and activation of a large number of substrate proteins. These are involved in essential cellular processes ranging from signal transduction to viral replication. For the activation of its substrates, Hsp90 binds and hydrolyzes ATP, which is the key driving force for conformational conversions within the dimeric chaperone. Dimerization of Hsp90 is mediated by a C-terminal dimerization site. In addition, there is a transient ATP-induced dimerization of the two N-terminal ATP-binding domains. The resulting ring-like structure is thought to be the ATPase-active conformation. Hsp90 is a slow ATPase with a turnover number of 1 ATP/min for the yeast protein. A key question for understanding the molecular mechanism of Hsp90 is how ATP hydrolysis is regulated and linked to conformational changes. In this study, we analyzed the activation process structurally and biochemically with a view to identify the conformational limitations of the ATPase reaction cycle. We showed that the first 24 amino acids stabilize the N-terminal domain in a rigid state. Their removal confers flexibility specifically to the region between amino acids 98 and 120. Most surprisingly, the deletion of this structure results in the complete loss of ATPase activity and in increased N-terminal dimerization. Complementation assays using heterodimeric Hsp90 show that this rigid lid acts as an intrinsic kinetic inhibitor of the Hsp90 ATPase cycle preventing N-terminal dimerization in the ground state. On the other hand, this structure acts, in concert with the 24 N-terminal amino acids of the other N-terminal domain, to form an activated ATPase and thus regulates the turnover number of Hsp90. 相似文献