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711.
Susanne I. Schmidt Marie König-Rinke Katja Kornek Carola Winkelmann Markus A. Wetzel Jochen H. E. Koop Jürgen Benndorf 《Aquatic Ecology》2009,43(1):169-179
Defining the reference condition is one of the most critical aspects of ecosystem investigations since it describes the baseline
against which the experimental sites will be evaluated and compared. In large-scale ecosystem experiments, this reference
is ideally another ecosystem which is similar to the experimental system. We investigated two streams for their potential
as experimental sites for a full-size pairwise ecosystem experiment. Temporal (2 years) and spatial (pool, riffle) variabilities
of abiotic factors and as biotic element the structure of the macroinvertebrate communities were investigated. Criteria of
similarity that we applied at the two streams were: (1) high similarity in abiotic factors, (2) only small differences in
the faunal assemblages (abundance structures, composition, feeding types), and (3) that the differences between the two systems
should not exceed the temporal and spatial differences within each system. Among the abiotic factors investigated, only the
inorganic nutrients (nitrate and soluble reactive phosphorus), major ions (magnesium, calcium), electric conductivity, and
pH showed significant differences between the two streams. Discharge rate, current velocity, temperature, and oxygen concentrations
did not significantly differ between the streams. Also, the community structure did not differ in species richness, abundance,
and biomass; and only small differences in dominance structure and feeding-type composition were observed. The differences
between habitats within each stream were always higher than those between the streams. Thus, both the streams are characterized
by a similar structure of the macroinvertebrate community, a main component of the stream food-web, which make them suitable
for a full size pairwise ecosystem experiment. The present case study can form a basis for other full-size field experiments. 相似文献
712.
713.
714.
Weekes R Deppe C Allnutt T Boffey C Morgan D Morgan S Bilton M Daniels R Henry C 《Transgenic research》2005,14(5):749-759
From 2000–2003 a range of Farm Scale Evaluation (FSE) trials were established in the UK to assess the effect of the release
and management of herbicide tolerant (HT) crops on the abundance and diversity of farmland wildlife compared with their conventionally
managed non-GM-equivalents. The objective of this research project was to investigate gene flow within the winter (WOSR) and
spring oilseed rape (SOSR) FSE trials and to develop a statistical model for the prediction of cross-pollination frequency
that can be used to evaluate current separation distance guidelines. Seed samples were collected from the non-GM half of the
trial sites and were tested for evidence of cross-pollination from the GM HT halves using a quantitative PCR assay specific
to the HT (bar) gene. Rates of cross-pollination were found to decrease rapidly with increasing distance from the GM source. The quantitative
data were subjected to statistical analysis and a two-step model was found to provide the best fit for the data. Significant
differences were found between the results for WOSR, SOSR and varietal association (VA) crops. The model predicted that the
%GM content (including upper 95% confidence limits) of a sample taken at a distance of 50 m away from the GM source would
be 0.04% (0.84%) for WOSR, 0.02% (0.39%) for SOSR, 0.77% (21.72%) for WOSR VA and 0.37% (5.18%) for SOSR VA. The data and
models presented here are discussed in the context of necessary separation distances to meet various possible thresholds for
adventitious presence of GM in OSR.
The British Crown's right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged. 相似文献
715.
Evaluation of new broth media for microdilution antibiotic susceptibility testing of Lactobacilli, Pediococci, Lactococci, and Bifidobacteria 总被引:7,自引:0,他引:7
Klare I Konstabel C Müller-Bertling S Reissbrodt R Huys G Vancanneyt M Swings J Goossens H Witte W 《Applied and environmental microbiology》2005,71(12):8982-8986
Nine pure or mixed broth media were evaluated for their suitabilities to determine MICs in a microdilution test of 19 antibacterial agents for lactic acid bacteria (LAB) of the genera Lactobacillus, Pediococcus, Lactococcus, and Bifidobacterium. A mixed formulation of Iso-Sensitest broth (90%) and deMan-Rogosa-Sharpe broth (10%) with or without supplementation with L-cysteine, referred to as the LAB susceptibility test medium, provided the most optimal medium basis in terms of growth support of nonenterococcal LAB and correct indication of MICs of international control strains. 相似文献
716.
Timing of the absence of <Emphasis Type="Italic">FMR1</Emphasis> expression in full mutation chorionic villi 总被引:5,自引:0,他引:5
Fragile X syndrome is caused by the expansion of the CGG repeat in the 5' untranslated region of the FMR1 gene. This expansion leads to methylation of the FMR1 promoter region thereby blocking FMR1 protein (FMRP) expression. Prenatal diagnosis can be performed on chorionic villi samples (CVS) by Southern blot analysis. Alternatively, for males, an immunohistochemical method has been introduced for CVS. In this study, we have used this immunocytochemical method for CVS in full mutation male fetuses at different times of gestational age, varying from 10.0-12.5 weeks, and in two cases of full mutation female fetuses (>13 weeks). FMRP expression studies in CVS from full mutation male fetuses (10.0-12.5 weeks) illustrate the timing of the disappearance of FMRP expression in these CVS. Until approximately 10 weeks of gestation, FMRP is expressed normally in full mutation male CVS, whereas FMRP is completely absent at 12.5 weeks of gestation. FMRP expression in full mutation female CVS (>13 weeks) is completely absent in a number of villi, whereas other villi show normal FMRP expression. Unlabelled villi can only be present in the absence of the expression of the full mutation FMR1 gene on one X-chromosome together with the X-inactivation of the normal X allele. FMRP positive villi can be explained by an active normal X allele. The presence of both positive and negative villi indicates that X-inactivation in human CVS is a random process. No villi are found with a mixture of both FMRP-expressing and non-FMRP-expressing cells. This indicates that X-inactivation occurs very early in development, before the villi start to proliferate, and that X-inactivation in villi is a clonal process. In addition, our results indicate that the timing of both X-inactivation and full mutation FMR1 allele inactivation is different, i.e. X-inactivation occurs earlier in development than inactivation of the full mutation. 相似文献
717.
Antiplasmodial activity of sesquilignans and sesquineolignans from Bonamia spectabilis 总被引:2,自引:0,他引:2
Kraft C Jenett-Siems K Köhler I Tofern-Reblin B Siems K Bienzle U Eich E 《Phytochemistry》2002,60(2):167-173
Phytochemical re-investigation of the aerial parts of Bonamia spectabilis (Convolvulaceae) led to the isolation of four minor tetrahydrofuran-type sesquilignans (bonaspectins E-H) together with the known neolignan virolongin A and the known lignan rel-(7S,8R,7'R,8'R)-3,3',4,4',5,5'-hexamethoxylignan. Their structures were established on the basis of spectral data. These six compounds as well as further seven lignanoids from B. spectabilis, characterised previously, were tested for their antiplasmodial activity against a chloroquine-sensitive strain (PoW) and a chloroquine-resistant clone (Dd2) of Plasmodium falciparum. Bonaspectin C 4"-O-glucoside, its aglycone, and bonaspectin D 4"-O-glucoside revealed the highest antiplasmodial activities (IC50 values: 1.3, 2.0, 6.5 microM [PoW]; 1.7, 4.6, 3.7 microM [Dd2], respectively). 相似文献
718.
Aerial parts of Croton hieronymi furnished in addition to a large number of plant sterols and triterpenes the C-25 analog of trans-phytol, the squalene derivatives all-trans-2,6,15,19,23-pentamethyltetracosa-2,6,10,(28),14,22,28-hexaene-11-ol and all-trans-10-methylene-2,6,10,14,18,22-pentamethyltetracosa-1,6,10,14,18,22-hexaen-3-ol, the sesquiterpenes epicubenol and T-cadinol, the acetophenone derivative xanthoxylin and the peptide derivatives aurentiamide acetate and N-benzoylphenylalanyl-N-benzoylphenylalaninate. 相似文献
719.
Helicobacter pylori has a particular affinity to cholesterol. It is not known, however, whether other steroidal substances are bound as well. In order to characterize the specificity and nature of the H. pylori-steroid interaction, the affinity of H. pylori to cholesterol and several steroidal hormones was investigated. Seven strains of H. pylori (five reference strains, two wild strains) and one strain each of Staphylococcus epidermidis and Escherichia coli were cultured on a cholesterol-free medium. Cholesterol-free bacteria were incubated with cyclodextrin-mediated cholesterol and several cyclodextrin-mediated steroidal hormones (beta-estradiol, testosterone, progesterone, hydrocortisone, dexamethasone). The steroid contents of the bacteria were determined by gas liquid chromatography. High amounts of cholesterol were detected in all H. pylori strains, whilst steroidal hormones were not found. Neither S. epidermidis nor E. coli showed an appreciable amount of cholesterol in the chromatographic examinations. Bacterial pretreatment with proteinase K diminished cholesterol adsorption of H. pylori. These data indicate a specific affinity of H. pylori to cholesterol. This unique property might serve as a pathogenicity component enabling survival and colonization of H. pylori in the gastric environment. 相似文献
720.
van der Knaap MS van Berkel CG Herms J van Coster R Baethmann M Naidu S Boltshauser E Willemsen MA Plecko B Hoffmann GF Proud CG Scheper GC Pronk JC 《American journal of human genetics》2003,73(5):1199-1207
Leukoencephalopathy with vanishing white matter, also called "childhood ataxia with central nervous system hypomyelination," is the first human disease related to mutations in any of the five genes encoding subunits of eukaryotic initiation factor eIF2B or any translation factor at all. eIF2B is essential in all cells of the body for protein synthesis and the regulation of this protein synthesis under different stress conditions. It is surprising that mutations in the eIF2B genes have been reported to lead to abnormalities of the white matter of the brain only, although it has been shown recently that ovarian failure may accompany the leukoencephalopathy. Another surprising observation is that the onset of the disease varies from early childhood to adulthood, with the exception of Cree leukoencephalopathy, a disease related to a particular mutation in one of the eIF2B genes, which invariably has its onset within the first year of life. We analyzed the eIF2B genes of nine patients with an antenatal- or early-infantile-onset encephalopathy and an early demise and found mutations in eight of the patients. In addition to signs of a serious encephalopathy, we found oligohydramnios, intrauterine growth retardation, cataracts, pancreatitis, hepatosplenomegaly, hypoplasia of the kidneys, and ovarian dysgenesis. Until now, no evidence had been found for a genotype-phenotype correlation, but the consistently severe phenotype in affected siblings among our patients and in Cree encephalopathy patients suggests an influence of the genotype on the phenotype. 相似文献