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651.
Yiqun Bao Benedikt Kost Nam-Hai Chua 《The Plant journal : for cell and molecular biology》2001,28(2):145-157
Different alpha-tubulin cDNA sequences fused in an antisense orientation to a CaMV 35S promoter were introduced into Arabidopsis thaliana plants. Several independent transgenic lines that showed a moderate but clear reduction of alpha-tubulin gene expression (TUA6/AS lines) were obtained and phenotypically characterized. Although no apparent abnormalities were detected in the aerial parts of TUA6/AS plants, root development was severely affected. Cells in TUA6/AS root tips were found to contain aberrant microtubular structures, to expand abnormally and to be unable to undergo regular cell division. These cellular defects caused a dramatic radial expansion of the root tip and inhibited root elongation. In addition, TUA6/AS roots displayed ectopic formation of root hairs, root hair branching and a reduced ability to respond to gravitropic challenges. Our results contribute to an improved understanding of the different roles microtubules play during root development and demonstrate that reverse genetics is a powerful tool to analyze cytoskeletal functions during plant organogenesis. 相似文献
652.
Rhythmic sensory or electrical stimulation will produce rhythmic brain responses. These rhythmic responses are often interpreted as endogenous neural oscillations aligned (or “entrained”) to the stimulus rhythm. However, stimulus-aligned brain responses can also be explained as a sequence of evoked responses, which only appear regular due to the rhythmicity of the stimulus, without necessarily involving underlying neural oscillations. To distinguish evoked responses from true oscillatory activity, we tested whether rhythmic stimulation produces oscillatory responses which continue after the end of the stimulus. Such sustained effects provide evidence for true involvement of neural oscillations. In Experiment 1, we found that rhythmic intelligible, but not unintelligible speech produces oscillatory responses in magnetoencephalography (MEG) which outlast the stimulus at parietal sensors. In Experiment 2, we found that transcranial alternating current stimulation (tACS) leads to rhythmic fluctuations in speech perception outcomes after the end of electrical stimulation. We further report that the phase relation between electroencephalography (EEG) responses and rhythmic intelligible speech can predict the tACS phase that leads to most accurate speech perception. Together, we provide fundamental results for several lines of research—including neural entrainment and tACS—and reveal endogenous neural oscillations as a key underlying principle for speech perception.Just as a child on a swing continues to move after the pushing stops, this study reveals similar entrained rhythmic echoes in brain activity after hearing speech and electrical brain stimulation; perturbation with tACS shows that these brain oscillations help listeners to understand speech. 相似文献
653.
Benedikt Hallgrímsson 《International journal of primatology》1999,20(1):121-151
I address the question of how fluctuating asymmetry (FA)—the distribution of random deviations from bilateral symmetry—varies ontogenetically in the mammalian skeleton. This question is significant because of the light that such patterns can shed on the causes of variation in developmental stability in bone as well as other structures. Based on large ontogenetic skeletal series of Macaca mulatta and Homo sapiens, I report that the FA variances of skeletal metric traits increase ontogenetically. Coupled with the finding that FA variances also accumulate to greater magnitudes in slower growing mammals, this result is consistent with the hypotheses that FA in bone is primarily caused by (a) cumulative effects of asymmetrical mechanical factors, (b) accumulation of variation in the (local) regulation of growth, or (c) a tendency for bone morphology to drift through undirected remodeling. I discuss the implications of these optional explanations for primate evolution and bone development. 相似文献
654.
Benjamin Dannenmann Maksim Klimiankou Benedikt Oswald Anna Solovyeva Jehan Mardan Masoud Nasri Malte Ritter Azadeh Zahabi Patricia Arreba-Tutusaus Perihan Mir Frederic Stein Siarhei Kandabarau Nico Lachmann Thomas Moritz Tatsuya Morishima Martina Konantz Claudia Lengerke Tim Ripperger Julia Skokowa 《Cell Stem Cell》2021,28(5):906-922.e6
655.
J. A. Werner Stefan Gottschlich Benedikt J. Folz Tibor Goeroegh Burkard M. Lippert J.-D. Maass Heinrich Rudert 《Cancer immunology, immunotherapy : CII》1997,44(2):112-116
p53 antibodies are a new serological parameter of unknown potential in patients with malignancies. Their occurrence has been
described in various types of cancer patients. The mechanism underlying the immunization process is still unclear. We investigated
the incidence of p53 serum antibodies in 143 head and neck cancer patients with an enzyme-linked immunosorbent assay. The
post-therapy course of two matched study groups (n = 38 each), one p53-antibody-seropositive and one p53-antibody-seronegative, was followed up for 24 months. Thirty-nine head
and neck cancer patients (27.3%) were seropositive for p53 antibodies. During the follow-up, the p53-antibody-seropositive
patients accounted for more local tumor recurrences (n = 12 versus n = 8) and more tumor-related deaths (n = 11 versus n = 5) than did seronegative patients, and second primary tumors (n = 9 versus n = 0) occurred exclusively in seropositive patients. In total, therapy failures (recurrences, tumor-related deaths,
second primaries) were observed in 17/38 cases (44.7%) in the p53-antibody-seropositive group and in 8/38 cases (21.1%) in
the p53-antibody-seronegative group. These results, after a follow-up of 2 years, seem to indicate a prognostic value of p53
serum antibodies for therapy failure in patients with head and neck cancer.
Received: 5 December 1996 / Accepted: 4 January 1997 相似文献
656.
Benedikt Hallgrímsson 《International journal of primatology》1993,14(3):421-443
Fluctuating asymmetry was determined for six cranial measurements in an age-diverse sample of 138 individuals ofMacaca fascicularis. These data were used to choose among four hypotheses concerning the etiology of developmental noise. The hypotheses considered are (1) that developmental noise represents asymmetry in the causal history of a developing organism's interaction with the environment, (2) that it represents stochasticity in the mechanics of growth and induction, (3) that it reflects variation in the initial conditions of a developmental process, and (4) that it represents the random accumulation of noise at a level below that of morphogenetic mechanism. These hypotheses were tested against predictions concerning the intraspecific patterning of fluctuating asymmetry against age and size and the covariation of asymmetry values. Only the predictions of the fourth hypothesis were confirmed by results of this study. These results provide evidence for the view that developmental noise, as reflected by fluctuating asymmetry, is an intrinsic property of developmental systems, and not merely produced by the complexity of the organism's interaction with the environment. 相似文献
657.
International Journal of Primatology - 相似文献
658.
659.
660.
Benedikt Hallgrímsson Heather Jamniczky Nathan M. Young Campbell Rolian Trish E. Parsons Julia C. Boughner Ralph S. Marcucio 《Evolutionary biology》2009,36(4):355-376
Organisms represent a complex arrangement of anatomical structures and individuated parts that must maintain functional associations
through development. This integration of variation between functionally related body parts and the modular organization of
development are fundamental determinants of their evolvability. This is because integration results in the expression of coordinated
variation that can create preferred directions for evolutionary change, while modularity enables variation in a group of traits
or regions to accumulate without deleterious effects on other aspects of the organism. Using our own work on both model systems
(e.g., lab mice, avians) and natural populations of rodents and primates, we explore in this paper the relationship between
patterns of phenotypic covariation and the developmental determinants of integration that those patterns are assumed to reflect.
We show that integration cannot be reliably studied through phenotypic covariance patterns alone and argue that the relationship
between phenotypic covariation and integration is obscured in two ways. One is the superimposition of multiple determinants
of covariance in complex systems and the other is the dependence of covariation structure on variances in covariance-generating
processes. As a consequence, we argue that the direct study of the developmental determinants of integration in model systems
is necessary to fully interpret patterns of covariation in natural populations, to link covariation patterns to the processes
that generate them, and to understand their significance for evolutionary explanation. 相似文献