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排序方式: 共有167条查询结果,搜索用时 15 毫秒
1.
Feasibility of expanded granular sludge bed reactors for the anaerobic treatment of low-strength soluble wastewaters 总被引:5,自引:0,他引:5
The application of the expanded granular sludge bed (EGSB) reactor for the anaerobic treatment of low-strength soluble wastewaters using ethanol as a model substrate was investigated in laboratory-scale reactors at 30oC. Chemical oxygen demand (COD) removal efficiency was above 80% at organic loading rates up to12 g COD/L . d with influent concentrations as low as 100 to 200 mg COD/L. These results demonstrate the suitability of the EGBS reactor for the anaerobic treatment of low-strength wastewaters. The high treatment performance can be attributed to the intense mixing regime obtained by high hydraulic and organic loads. Good mixing of the bulk liquid phase for the substrate-biomass contact and adequate expansion of the substrate-biomass contact and adequate expansion of the sludge bed for the degassing were obtained when the liquid upflow velocity (V(up)) was greater than 2.5 m/h. Under such conditions, an extremely low apparent K(s) value for acetoclastic methanogenesis of 9.8 mg COD/L was observed. The presence of dissolved oxygen in the wastewater had no detrimental effect on the treatment performance. Sludge piston flotation from pockets of biogas accumulating under the sludge bed occurred at V(up) lower than 2.5 m/h due to poor bed expansion. This problem is expected only in small diameter laboratory-scale reactors. A. more important restriction of the EGSB reactor was the sludge washout occurring at V(up) higher than 5.5 m/h and which was intensified at organic loads higher than 7 g COD/L. d due to buoyancy forces from the gas production. To achieve an equilibrium between the mixing intensity and the sludge hold-up, the operation should be limited to an organic loading rate of 7 g COD/L d. and to a liquid up-flow velocity between 2.5 and 5.5 m/h (c) 1994 John Wiley & Sons, Inc. 相似文献
2.
Alastair A. Macdonald Ben Colenbrander Dirk H. G. Versteeg Alfred Heilhecker Cees J. G. Wensing 《Development genes and evolution》1984,193(1):19-23
Summary Dopamine, norepinephrine and epinephrine were measured by radioenzymatic assay in blood plasma samples drawn from the umbilical arteries of 30 anaesthetised Landrace pig fetuses. Just prior to term, the concentrations of dopamine (0.46±0.14 ng·ml–1) and norepinephrine (1.74±0.60 ng·mg–1) were lower than earlier in gestation, whereas epinephrine concentrations at term (0.80±0.31 ng·ml–1) were similar to those at mid-gestation, intervening stages of gestation having higher levels of plasma epinephrine. Fetal hypoxia was induced by clamping the umbilical cord for 2 min and the catecholamines determined in arterial blood samples immediately thereafter, then again 3 min after removal of the clamp. Inconsistent effects of cord clamping on catecholamine levels were seen at 55 days, but thereafter, in all but one instance, the hormone levels were increased. Fetuses near term tended to respond less than fetuses at 75 and 96 days gestation (term=114±1 day). Catecholamines were also present in the circulation of fetuses decapitated at 42 days gestation and studied at 109±1 days. The average concentrations of dopamine (1.12±0.27 ng·ml–1) and norepinephrine (8.23±3.04 ng·ml–1) were greater than in intact fetuses, the plasma epinephrine levels being comparable to, or slightly higher than, those in intact fetuses. The results demonstrate that catecholamines are present in the circulation of the intact and decapitated pig fetus and that the actual concentrations and the type of response to umbilical cord clamping are dependent on gestation age. 相似文献
3.
Robin E. Everts Serge A. Versteeg Corinne Renier Francoise Vignaux Peter C. Groot Jan Rothuizen Bernard A. van Oost 《Mammalian genome》2000,11(9):741-747
Genomic Representational Difference Analysis (gRDA) is a subtractive DNA method to clone the differences between two related
genomes, called tester and driver. We have evaluated this method to obtain polymorphic DNA markers for pedigree dogs. Amplified
size-selected genomic restriction fragments (amplicons) of two dog littermates were repeatedly hybridized to each other in
order to remove (subtract) those restriction fragments common to both sibs. Already after two rounds of subtractive hybridization,
a clear enrichment of presumably tester-specific restriction fragments was observed, which was even more pronounced after
the third round of subtraction. A plasmid library of 3000 recombinant clones was constructed of the second round and of the
third round difference product. DNA sequence determination of randomly chosen clones of each difference product showed that
approximately 1000 unique clones were obtained in the second-round difference product and approximately 500 in the third-round
difference product. About half of the clones identified in the second-round difference product were also present in the third-round
difference product. Of the second-round difference product, 39 different gRDA fragments could be identified, of which 21 were
tester specific. In the third-round difference product, 22 different gRDA fragments were identified, of which 18 were tester
specific. There were 13 fragments in common, resulting in a total of 48 different fragments. In order to establish the localization
of these markers, we performed mapping using the dog radiation hybrid panel RHDF5000. Of 39 mapped clones, 29 were mapped
to 20 existing RH groups, and 10 remained unlinked. It is concluded that gRDA is suitable to generate DNA markers to track
disease genes within lines of pedigree dogs.
Received: 26 April 2000 / Accepted: 11 May 2000 相似文献
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Kristoffer von Stedingk Jan Koster Marta Piqueras Rosa Noguera Samuel Navarro Sven Påhlman Rogier Versteeg Ingrid Øra David Gisselsson David Lindgren Håkan Axelson 《Translational oncology》2013,6(4):447-IN6
Amplification of the MYCN oncogene is strongly associated with poor prognosis in neuroblastoma (NB). In addition to MYCN amplification, many studies have focused on identifying patients with a poor prognosis based on gene expression profiling. The majority of prognostic signatures today are comprised of large gene lists limiting their clinical application. In addition, although of prognostic significance,most of these signatures fail to identify cellular processes that can explain their relation to prognosis. Here, we determined prognostically predictive genes in a data set containing 251 NBs. Gene Ontology analysis was performed on significant genes with a positive hazard ratio to search for cellular processes associated with poor prognosis. An enrichment in ribonucleoproteins (RNPs) was found. Genes involved in the stabilization and formation of the central small nucleolar RNP (snoRNP) complex were scrutinized using a backward conditional Cox regression resulting in an snoRNP signature consisting of three genes: DKC1, NHP2, and GAR1. The snoRNP signature significantly and independently predicted prognosis when compared to the established clinical risk factors. Association of snoRNP protein expression and prognosis was confirmed using tissue microarrays. Knockdown of snoRNP expression in NB cell lines resulted in reduced telomerase activity and an increase in anaphase bridge frequency. In addition, in patient material, expression of the snoRNP complex was significantly associated with telomerase activity, occurrence of segmental aberrations, and expression-based measurements of chromosomal instability. Together, these results underscore the prognostic value of snoRNP complex expression in NB and suggest a role for snoRNPs in telomere maintenance and genomic stability. 相似文献
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Sangkyun Lee J?rg Rahnenführer Michel Lang Katleen De Preter Pieter Mestdagh Jan Koster Rogier Versteeg Raymond L. Stallings Luigi Varesio Shahab Asgharzadeh Johannes H. Schulte Kathrin Fielitz Melanie Schwermer Katharina Morik Alexander Schramm 《PloS one》2014,9(10)
Identifying relevant signatures for clinical patient outcome is a fundamental task in high-throughput studies. Signatures, composed of features such as mRNAs, miRNAs, SNPs or other molecular variables, are often non-overlapping, even though they have been identified from similar experiments considering samples with the same type of disease. The lack of a consensus is mostly due to the fact that sample sizes are far smaller than the numbers of candidate features to be considered, and therefore signature selection suffers from large variation. We propose a robust signature selection method that enhances the selection stability of penalized regression algorithms for predicting survival risk. Our method is based on an aggregation of multiple, possibly unstable, signatures obtained with the preconditioned lasso algorithm applied to random (internal) subsamples of a given cohort data, where the aggregated signature is shrunken by a simple thresholding strategy. The resulting method, RS-PL, is conceptually simple and easy to apply, relying on parameters automatically tuned by cross validation. Robust signature selection using RS-PL operates within an (external) subsampling framework to estimate the selection probabilities of features in multiple trials of RS-PL. These probabilities are used for identifying reliable features to be included in a signature. Our method was evaluated on microarray data sets from neuroblastoma, lung adenocarcinoma, and breast cancer patients, extracting robust and relevant signatures for predicting survival risk. Signatures obtained by our method achieved high prediction performance and robustness, consistently over the three data sets. Genes with high selection probability in our robust signatures have been reported as cancer-relevant. The ordering of predictor coefficients associated with signatures was well-preserved across multiple trials of RS-PL, demonstrating the capability of our method for identifying a transferable consensus signature. The software is available as an R package rsig at CRAN (http://cran.r-project.org). 相似文献
10.
de Rooij MM Schimmer B Versteeg B Schneeberger P Berends BR Heederik D van der Hoek W Wouters IM 《PloS one》2012,7(2):e32108