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31.
The treatment of massive upper gastrointestinal hemorrhage by gastric hypothermia was studied clinically in 23 patients: five with peptic ulcer, six with multiple gastric erosions, nine with portal hypertension and varices, and three with coagulation defects. Hemorrhage was controlled in 13 of the patients. The high mortality (14 out of 23 patients) was attributed to the severity of the bleeding and to the underlying disease, particularly in patients with liver failure. This form of treatment is a useful method of treating selected patients with upper gastrointestinal hemorrhage. 相似文献
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A key question in barnacle biology is the nature of cues that induce gregarious settlement. One of the characterised cues is the waterborne settlement pheromone (WSP). This study aimed to identify WSP homologues in Balanus improvisus and to investigate their expression during settlement. Six WSP homologues were identified, all containing an N-terminal signal peptide, a conserved core region, and a variable C-terminus comprising several -GR- and -HDDH- motifs. The B. improvisus WSP homologues were expressed in all settlement stages but showed different expression patterns. The homologue most similar to the B. amphitrite WSP was the most abundant and was constantly expressed during settlement. In contrast, several of the other WSP homologues showed the greatest expression in the juvenile stage. The presence of several WSP homologues suggests the existence of a pheromone mix, where con-specificity might be determined by a combination of sequence characteristics and the concentration of the individual components. 相似文献
36.
From 2001 to 2003, leaf rust was collected in different regions of Germany and the Russian Federation to generate single spore isolates and to study the structure of the pathogen populations by analyses of virulence. The virulence of isolates was tested with 38 near‐isogenic lines each carrying a different resistance gene. The analyses of variance revealed significant effects for the frequency of virulent isolates, the regions and most interactions with years and regions, but no significance was found for the effects of years. In Germany, an increase of virulence frequencies was detected for Lr1 and Lr2a while a decrease was found for Lr3a, Lr3bg and Lr3ka. Such clear trends did not occur in Russia which may be due to the great agroclimatic differences between regions. The variance of the frequency of virulent isolates was used to estimate adequate sample sizes for the analysis of regional populations of leaf rust. This procedure resulted in more reliable information about the dynamic processes within the pathogen populations. In 2002 and 2003, all pathotypes in Germany had a combined virulence to Lr1, Lr2a, Lr2b, Lr15, Lr17 and Lr20 supplemented by a few other genes. The complexity of virulence was lower in the most frequent pathotypes. In Russia virulence to the alleles at locus Lr3 was very common. Using detached leaf segments in Germany and Russia it turned out that the most virulent pathotypes carry 34 and 32 virulence genes, respectively. Virulence to Lr9, Lr19, Lr24 and Lr38 was rare or even absent. The use of major genes, not overcome by corresponding virulent pathotypes, may contribute to more durable types of resistance in case they are combined with genes having different effects, e.g. adult plant resistance. 相似文献
37.
Study of the Infectivity of Saline-Stored Campylobacter jejuni for Day-Old Chicks 总被引:1,自引:0,他引:1 下载免费PDF全文
The culturability of three Campylobacter jejuni strains and their infectivity for day-old chicks were assessed following storage of the strains in saline. The potential for colonization of chicks was weakened during the storage period and terminated 3 to 4 weeks before the strains became nonculturable. The results from this study suggest that the role of starved and aged but still culturable campylobacters may be diminutive, but even more, that the role of viable but nonculturable stages in campylobacter epidemiology may be negligible. Even high levels of maternally derived anti-campylobacter outer membrane protein serum antibodies in day-old chicks did not protect the chicks from campylobacter colonization. 相似文献
38.
Tobias Maierhofer Christof Lind Stefanie Hüttl S?nke Scherzer Melanie Papenfu? Judy Simon Khaled A.S. Al-Rasheid Peter Ache Heinz Rennenberg Rainer Hedrich Thomas D. Müller Dietmar Geiger 《The Plant cell》2014,26(6):2554-2567
In contrast to animal cells, plants use nitrate as a major source of nitrogen.
Following the uptake of nitrate, this major macronutrient is fed into the vasculature
for long-distance transport. The Arabidopsis thaliana shoot
expresses the anion channel SLOW ANION CHANNEL1 (SLAC1) and its homolog SLAC1
HOMOLOGOUS3 (SLAH3), which prefer nitrate as substrate but cannot exclude chloride
ions. By contrast, we identified SLAH2 as a nitrate-specific channel that is
impermeable for chloride. To understand the molecular basis for nitrate selection in
the SLAH2 channel, SLAC1 and SLAH2 were modeled to the structure of HiTehA, a
distantly related bacterial member. Structure-guided site-directed mutations
converted SLAC1 into a SLAH2-like nitrate-specific anion channel and vice versa. Our
findings indicate that two pore-occluding phenylalanines constrict the pore. The
selectivity filter of SLAC/SLAH anion channels is determined by the polarity of
pore-lining residues located on alpha helix 3. Changing the polar character of a
single amino acid side chain (Ser-228) to a nonpolar residue turned the
nitrate-selective SLAH2 into a chloride/nitrate-permeable anion channel. Thus, the
molecular basis of the anion specificity of SLAC/SLAH anion channels seems to be
determined by the presence and constellation of polar side chains that act in concert
with the two pore-occluding phenylalanines. 相似文献
39.
Klas H. Pettersen Henrik Lindén Tom Tetzlaff Gaute T. Einevoll 《PLoS computational biology》2014,10(11)
Power laws, that is, power spectral densities (PSDs) exhibiting behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency power laws with power-law exponents analytically identified as for the soma membrane current, for the current-dipole moment, and for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink () noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how power laws with a wide range of values for the power-law exponent α may arise from a simple, linear partial differential equation. 相似文献
40.
Recently, Dclk1 expression was identified to be an intestinal cancer stem cell specific biomarker in mouse models, implicating a potential role for targeting the DCLK1-postive cancer cells as a treatment for colorectal cancer. Using quantitative methylation specific PCR (qMSP) we here demonstrated that the DCLK1 promoter is hypermethylated in the vast majority of colorectal cancers (134/164; 82%), with no methylation in the normal mucosa samples (0/106). We further showed by Affymetrix exon arrays that DCLK1 is significantly downregulated in human colorectal cancer (n = 125) compared with normal colonic mucosa (n = 15), which was further confirmed by real-time RT-PCR of a subgroup of the samples. Additionally, a significant negative correlation was observed between methylation and DCLK1 expression in 74 cancer cell lines derived from 15 different tissues, and gene expression increased significantly after epigenetic drug treatment of initially methylated cancer cell lines. These findings underscore the potential of DCLK1 as a colorectal cancer biomarker for early detection, but may also have clinical implications regarding the previously proposed therapy toward DCLK1-positive cancer cells. This therapy would at best affect the cancer stem cell population, but will, based on the present results, not be efficient to treat the bulk of the tumor. 相似文献