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Dominik Linz Eva Hesselkilde Rayed Kutieleh Thomas Jespersen Rikke Buhl Prashanthan Sanders 《Journal of cardiovascular electrophysiology》2020,31(5):1211-1212
Atrial fibrillation is triggered by the pulmonary veins in humans. Although atrial fibrillation is known to occur in other species, the mechanisms of disease in these are not known. Here we present evidence for pulmonary vein triggers in the horse, where 3D HD Grid mapping was undertaken in the conscious state in the absence of fluoroscopy. 相似文献
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Chien-Cheng Chen Melody Ying-Yu Huang Konrad P. Weber Dominik Straumann Christopher J. Bockisch 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2014,232(9):2891-2898
The afternystagmus that occurs in the dark after gaze fixation during optokinetic stimulation is directed in the opposite direction relative to the previous optokinetic stimulus. The mechanism responsible for such afternystagmus after suppression of optokinetic nystagmus (ASOKN) is unclear. Several hypotheses have been put forward to explain it, but none is conclusive. We hypothesized that ASOKN is driven by the interaction of two mechanisms: (1) motion-aftereffect (MAE)-induced eye movements and (2) retinal afterimages (RAIs) produced by fixation during the suppression of optokinetic nystagmus (OKN). We examined the correlation among ASOKN, MAE-induced eye movements, and RAIs in healthy subjects. Adapting stimuli consisted of moving random dot patterns and a fixation spot and their brightness was adjusted to induce different RAI durations. Test patterns were a stationary random dot pattern (to test for the presence of a MAE), a dim homogeneous background (to test for MAE driven eye movements), and a black background (to test for ASOKN and RAIs). MAEs were reported by 16 out of 17 subjects, but only 7 out of 17 subjects demonstrated MAE-induced eye movements. Importantly, ASOKN was only found when these seven subjects reported a RAI after suppression of OKN. Moreover, the duration of ASOKN was longer for high-brightness stimuli compared with low-brightness stimuli, just as RAIs persist longer with increasing brightness. We conclude that ASOKN results from the interaction of MAE-induced eye movements and RAIs. 相似文献
98.
Dominik Wiemuth Cathérine M. T. Lefèvre Hannelore Heidtmann Stefan Gründer 《Pflügers Archiv : European journal of physiology》2014,466(9):1725-1733
The epithelial Na+ channel (ENaC) is a key regulator of Na+ absorption in various epithelia including the distal nephron and the distal colon. ENaC is a constitutively active channel, but its activity is modulated by a number of mechanisms. These include proteolytic activation, ubiquitination and cell surface expression, phosphorylation, intracellular Na+ concentration, and shear stress. ENaC is related to the bile acid-sensitive ion channel (BASIC), a channel that is expressed in the epithelial cells of bile ducts. BASIC is activated by millimolar concentrations of extracellular bile acids. Bile acids are synthesized by the liver and secreted into the duodenum to aid lipolysis. A large fraction of the secreted bile acids is absorbed by the ileum and recirculated into the liver, but a small fraction passes the colon and is excreted. Bile acids can influence the ion transport processes in the intestinal tract including the colon. In this study, we show that various bile acids present in rat bile potently and reversibly increase the activity of rat ENaC expressed in Xenopus oocytes, suggesting that bile acids are natural modulators of ENaC activity. 相似文献
99.
Ulrike Rottensteiner Bapi Sarker Dominik Heusinger Diana Dafinova Subha N. Rath Justus P. Beier Ulrich Kneser Raymund E. Horch Rainer Detsch Aldo R. Boccaccini Andreas Arkudas 《Materials》2014,7(3):1957-1974
In addition to good mechanical properties needed for three-dimensional tissue engineering, the combination of alginate dialdehyde, gelatin and nano-scaled bioactive glass (45S5) is supposed to combine excellent cellular adhesion, proliferation and differentiation properties, good biocompatibility and predictable degradation rates. The goal of this study was to evaluate thein vitro and in vivo biocompatibility as a first step on the way to its use as a scaffold in bone tissue engineering. In vitro evaluation showed good cell adherence and proliferation of bone marrow derived mesenchymal stem cells seeded on covalently crosslinked alginate dialdehyde-gelatin (ADA-GEL) hydrogel films with and without 0.1% nano-Bioglass®(nBG). Lactate dehydrogenase (LDH)- and mitochondrial activity significantly increased in both ADA-GEL and ADA-GEL-nBG groups compared to alginate. However, addition of 0.1% nBG seemed to have slight cytotoxic effect compared to ADA-GEL. In vivo implantation did not produce a significant inflammatory reaction, and ongoing degradation could be seen after four weeks. Ongoing vascularization was detected after four weeks. The good biocompatibility encourages future studies using ADA-GEL and nBG for bone tissue engineering application. 相似文献
100.
Emily L. Doolittle Bruno Gingras Dominik M. Endres W. Tecumseh Fitch 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(46):16616-16621
Many human musical scales, including the diatonic major scale prevalent in Western
music, are built partially or entirely from intervals (ratios between adjacent
frequencies) corresponding to small-integer proportions drawn from the harmonic
series. Scientists have long debated the extent to which principles of scale
generation in human music are biologically or culturally determined. Data from animal
“song” may provide new insights into this discussion. Here, by
examining pitch relationships using both a simple linear regression model and a
Bayesian generative model, we show that most songs of the hermit thrush
(Catharus guttatus) favor simple frequency ratios derived from
the harmonic (or overtone) series. Furthermore, we show that this frequency selection
results not from physical constraints governing peripheral production mechanisms but
from active selection at a central level. These data provide the most rigorous
empirical evidence to date of a bird song that makes use of the same mathematical
principles that underlie Western and many non-Western musical scales, demonstrating
surprising convergence between human and animal “song cultures.”
Although there is no evidence that the songs of most bird species follow the overtone
series, our findings add to a small but growing body of research showing that a
preference for small-integer frequency ratios is not unique to humans. These findings
thus have important implications for current debates about the origins of human
musical systems and may call for a reevaluation of existing theories of musical
consonance based on specific human vocal characteristics.Many human musical scales, including the diatonic major scale
prevalent in Western music, are built partially or entirely from intervals (ratios between
adjacent frequencies) corresponding to small-integer ratios drawn from the harmonic series
(1). A long-running debate concerns the extent to
which principles underlying the structure of human musical scales derive from biological
aspects of auditory perception and/or vocal production or are historical cultural
“accidents” (2–4). The songs of nonhuman
animals, such as birds or whales, potentially offer a valuable perspective on this debate.
On the one hand, features of human music that are culturally bound, or dependent on
specific characteristics of the human voice or auditory system, should be absent in animal
vocalizations. On the other hand, aspects of human music observed in the vocalizations of
other species seem likely to be partially determined by general physical or biological
constraints rather than solely by cultural practices. Such shared features would complement
recent research suggesting that common motor constraints shape both human song and that of
some bird species (5).The physical principles underlying vocal production in songbirds are well understood (6–10) and do not differ fundamentally from those of other vertebrates. Sound is
produced by tissue vibrations in the syrinx, a bird-specific organ located at the base of
the trachea. Flow-driven vibrations of fleshy membranes within the syrinx (in songbirds,
the medial and lateral labia) generate a periodic source signal that is filtered by the air
column within the trachea and mouth and then emitted to the environment. These principles
are important in formulating various alternative hypotheses considered below.Naturalists have long wondered whether birdsong could be said to have musical properties
(11–13). However, early studies on pitch selection tended
to be anecdotal, based on a small sample size, or lacking in analytical rigor. Two more
recent studies specifically comparing pitch selection in bird song and human musical scales
concluded that birdsong does not make preferential use of musical intervals found in
commonly used Western musical scales (14, 15). However, because these studies each only examined
one species [the white-throated sparrow (Zonotrichia albicollis) and the
nightingale wren (Microcerculus philomela), respectively], a conclusion
that birdsong in general does not exhibit musical properties seems premature. Indeed, other
studies have shown preferential use of consonant intervals in tropical boubou shrikes
(Laniarius aethiopicus) (16) and
musician wrens (Cyphorhinus arada) (17), although in the first case no rigorous statistical analysis was
presented.Here, we investigated songs of the hermit thrush (Catharus guttatus), a
medium-sized North American songbird whose famously “musical”-sounding song
has attracted the attention of ornithologists and musicians alike (18) but has not yet been subjected to detailed pitch analysis. Its
songs are composed of elements (the smallest unit of song construction, seen as continuous
uninterrupted traces on spectrograms) that may exhibit either a variable pitch, such as
trills and slides, or a stable pitch—pure, non-frequency-modulated,
“flutelike” sounds. These stable sounds, which we refer to as
“notes” (Fig. 1), are characterized
by strong fundamental frequencies and very weak higher harmonics, making them ideally
suited for an analysis of pitch relationships (15).
Males typically sing 6–10 different song types, defined as nearly identical
sequences of elements, durations, and frequencies. In a number of early- and
mid-20th-century studies, hermit thrush song was variously attributed with use of major,
minor, and pentatonic scales (19, 20) and claimed to follow the overtone series (21). However, these early studies again suffered from
small sample sizes and anecdotal reporting and were not based on rigorous acoustic
analysis. More recent hermit thrush studies have focused on regional differences and
song-type ordering, rather than pitch selection (22, 23).Open in a separate windowFig. 1.Song of the hermit thrush (C. guttatus). One song type of a single
male hermit thrush, illustrating the various elements that can be observed in songs
of this species. Only “notes” (elements with stable pitch) were
analyzed in this study because the other element types have no clearly defined or
measurable pitch.Here we tested the overtone hypothesis, which predicts that the frequencies of the
individual song notes are integer multiples (harmonics) of an implied (but not actually
sung) base frequency (hereafter fi). This hypothesis seems
plausible because, unlike some previous claims, it does not attribute human-specific
music-theoretical concepts to hermit thrush song. Moreover, the subjective impression of
trained musicians listening to hermit thrush songs (played at one-sixth of the original
speed to shift the speed and frequency of the songs into a range more suitable for human
hearing) was that most notes indeed seemed to follow an overtone series (see Fig. 2 and Audio File S1 for the corresponding sound example). However,
determining whether a set of notes are harmonics of a frequency not present in the set
requires a rigorous procedure to estimate and evaluate fi. To
this end, we used two different statistical approaches, an ordinary least-squares
regression model and a generative Bayesian estimator. Both approaches were used to test the
hypothesis that a song is an exchangeable sequence of frequencies that are integer
multiples of some implied fi, versus the null hypothesis that
songs are generated by drawing frequencies out of a random log-normal distribution (see
Materials and Methods for
details). By using a Bayesian approach in addition to the least-squares regression model we
evaluate whether our analyses represent a rigorous test of our overtone hypothesis and not
simply a post hoc explanation that minimizes an error measure by “memorizing”
the data. These properties make the Bayesian evaluation statistically more rigorous than
least-squares fitting.Open in a separate windowFig. 2.Frequency distribution of a hermit thrush song compared with an overtone series.
(A) Notes of a hermit thrush song. (B) The same
notes rearranged in ascending order to show how they correspond to overtones 3, 4, 5,
and 6 of an overtone series fitted to the frequencies corresponding to these notes
(the complete stacked overtone series is shown on the right). 相似文献