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101.
102.
Dung fauna plays an important role in dung decomposition, a key ecosystem process in nutrient cycling in grazed grasslands. The diversity of a three‐species community (dung beetles, dung flies and epigeic earthworms) was systematically manipulated to produce different relative abundance distributions (evenness levels) and the resulting communities were introduced to standardised dung pats in laboratory experiments. Dung decomposition was modelled using an analysis that disentangled species identity effects and the interactions among species that contribute to the diversity effect. This revealed that the net diversity effect was composed of positive (fly–earthworm), negative (beetle–earthworm) and neutral (fly–beetle) effects of species interaction. These pairwise interactions resulted in complex, but systematically varying and predictable effects on dung decomposition as the relative abundances of species changed. Decomposition was consistently greater in communities with higher decomposer biomass. The utility of the adopted analytical approach was emphasised by comparison with an ANOVA that found that dung decomposition did not differ among evenness levels. Thus, the averaging of decomposition across different community structures within evenness levels masked the different effects of species interactions. These results highlight methodological insights into the quantification of diversity–function relationships. 相似文献
103.
Variation in the gut microbiota of laboratory mice is related to both genetic and environmental factors 总被引:1,自引:0,他引:1
During recent years, the composition of the gut microbiota (GM) has received increasing attention as a factor in the development of experimental inflammatory disease in animal models. Because increased variation in the GM might lead to increased variation in disease parameters, determining and reducing GM variation between laboratory animals may provide more consistent models. Both genetic and environmental aspects influence the composition of the GM and may vary between laboratory animal breeding centers and within an individual breeding center. This study investigated the variation in cecal microbiota in 8-wk-old NMRI and C57BL/6 mice by using denaturing gradient gel electrophoresis to profile PCR-derived amplicons from bacterial 16S rRNA genes. Comparison of the cecal microbiotas revealed that the similarity index of the inbred C57BL/6Sca strain was 10% higher than that of the outbred Sca:NMRI stock. Comparing C57BL/6 mice from 2 vendors revealed significant differences in the microbial profile, whereas the profiles of C57BL/6Sca mice raised in separate rooms within the same breeding center were not significantly different. Furthermore, housing in individually ventilated cages did not lead to intercage variation. These results show that denaturing gradient gel electrophoresis is a simple tool that can be used to characterize the gut microbiota of mice. Including such characterizations in future quality-control programs may increase the reproducibility of mouse studies. 相似文献
104.
Csillag C Nielsen OH Borup R Nielsen FC Olsen J 《American journal of physiology. Gastrointestinal and liver physiology》2007,292(1):G298-G304
The clinical course varies significantly among patients with Crohn's disease (CD). This study investigated whether gene expression profiles generated by DNA microarray technology might predict disease progression. Biopsies from the descending colon were obtained colonoscopically from 40 CD patients. Gene profiling analyses were performed using a Human Genome U133 Plus 2.0 GeneChip Array, and summarization into a single expression measure for each probe set was performed using the robust multiple array procedure. Principal component analysis demonstrated that three components explain two-thirds of the total variation. The most important parameters for the determination of the colonic gene expression patterns were the presence of disease (CD) and presence of inflammation. Superimposition of clinical phenotype data revealed a grouping of the samples from patients with stenosis toward negative values on the axis of the second principal component. The functional annotation analysis suggested that the expression of genes involved in intracellular transport and cytoskeletal organization might influence the development of stenosis. In conclusion, even though most variation in the colonic gene expression patterns is due to presence or absence of CD and inflammation status, the development of stenosis is a parameter that affects colonic gene expression to some extent. 相似文献
105.
Rat cytomegalovirus gene expression in cardiac allograft recipients is tissue specific and does not parallel the profiles detected in vitro
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106.
Tor F. Næsje Amber-Robyn Childs Paul D. Cowley Warren M. Potts Eva B. Thorstad Finn Økland 《Hydrobiologia》2007,582(1):25-34
The purpose of this study was to test the hypothesis that an estuarine species as the spotted grunter Pomadasys commersonnii is evenly distributed within the estuary and uniformly exploited by different groups of fishers. This was done by investigating
the movements and area use of spotted grunter in relation to the fisheries. The position of 20 acoustically tagged fish was
recorded during 36 days in February and March 2003, by manual tracking and automated data logging receivers. Information on
the fisheries in the estuary was collected through visual registration of fishing effort and interviews. The spotted grunter
moved on average 1.0 km (SD ± 0.7) between positional fixes. Most of the fish were positioned in the lower part of the 12
km long estuary, as 70% of the positional fixes were within the first 3 km, and 89% within the first 6 km. Approximately half
(49%) of all the fixes were between 1.0 and 1.5 km from the estuary mouth. The spotted grunter used on average 4.9 km (SD
± 4.9) of the length of the estuary, and there was no significant relationship between the length of the estuary used and
the body length of the fish (26–39 cm TL). Subsistence fishers accounted for 73% of fishing lines in the water, while recreational
fishers accounted for the rest. Ninety-three percent of the lines were recorded within the first 6 km from the estuary mouth,
of which 80% were recorded within the first 3 km. Almost 1/3 of the fishing effort was recorded between 1.0 and 1.5 km from
the mouth. The hypothesis that the estuarine dependent species spotted grunter was evenly distributed within the estuary was
rejected. However, there was a significant relationship between the distribution of the fishing effort of the subsistence
fishers and the fish, indicating that the spotted grunter was uniformly exploited within the estuary by this group of fishers.
In contrast, there was no relationship between the distribution of fish and recreational anglers. 相似文献
107.
Transposon Tn7 directs transposition into the genome of filamentous bacteriophage M13 using the element-encoded TnsE protein
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The bacterial transposon Tn7 has a pathway of transposition that preferentially targets conjugal plasmids. We propose that this same transposition pathway recognizes a structure or complex found during filamentous bacteriophage replication, likely by targeting negative-strand synthesis. The ability to insert into both plasmid and bacteriophage DNAs that are capable of cell-to-cell transfer would help explain the wide distribution of Tn7 relatives. 相似文献
108.
Mid-Tertiary dispersal, not Gondwanan vicariance explains distribution patterns in the wax palm subfamily (Ceroxyloideae: Arecaceae) 总被引:2,自引:0,他引:2
Trénel P Gustafsson MH Baker WJ Asmussen-Lange CB Dransfield J Borchsenius F 《Molecular phylogenetics and evolution》2007,45(1):272-288
The Ceroxyloideae is a small but heterogeneous subfamily of palms (Arecaceae, Palmae). It includes a Caribbean lineage (tribe Cyclospathae), a southern hemisphere disjunction (tribe Ceroxyleae), and an amphi-Andean element (tribe Phytelepheae), until recently considered a distinct subfamily (Phytelephantoideae) due to its highly derived morphology. A variety of hypotheses have been proposed to account for the biogeography of the subfamily, involving Gondwanan vicariance, austral interplate dispersal from South America to Australia via Antarctica, Andean orogeny, and Pleistocene refuges. We assessed the systematic classification and biogeography of the group based on a densely sampled phylogeny using >5.5kb of DNA sequences from three plastid and two nuclear genomic regions. The subfamily and each of its three tribes were resolved as monophyletic with high support. Divergence time estimates based on penalized likelihood and Bayesian dating methods indicate that Gondwanan vicariance is highly unlikely as an explanation for basic disjunctions in tribe Ceroxyleae. Alternative explanations include a mid-Tertiary trans-Atlantic/trans-African dispersal track and the "lemurian stepping stones" hypothesis. Austral interplate dispersal of Oraniopsis to Australia could have occurred, but apparently only in the mid-Eocene/early Oligocene interval after global cooling had begun. Our data do not support Pleistocene climatic changes as drivers for speciation in the Andean-centered Phytelepheae as previously proposed. Radiation in this tribe coincides largely with the major uplift of the Andes, favoring Andean orogeny over Pleistocene climatic changes as a possible speciation-promoting factor in this tribe. 相似文献
109.
Funke BH Lencz T Finn CT DeRosse P Poznik GD Plocik AM Kane J Rogus J Malhotra AK Kucherlapati R 《Molecular medicine (Cambridge, Mass.)》2007,13(7-8):407-414
A significant portion of patients with 22q11 deletion syndrome (22q11DS) develop psychiatric disorders, including schizophrenia and other psychotic and affective symptoms, and the responsible gene/s are assumed to also play a significant role in the etiology of nonsyndromic psychiatric disease. The most common psychiatric diagnosis among patients with 22q11DS is schizophrenia, thought to result from neurotransmitter imbalances and also from disturbed brain development. Several genes in the 22q11 region with known or suspected roles in neurotransmitter metabolism have been analyzed in patients with isolated schizophrenia; however, their contribution to the disease remains controversial. Haploinsufficiency of the TBX1 gene has been shown to be sufficient to cause the core physical malformations associated with 22q11DS in mice and humans and via abnormal brain development could contribute to 22q11DS-related and isolated psychiatric disease. 22q11DS populations also have increased rates of psychiatric conditions other than schizophrenia, including mood disorders. We therefore analyzed variations at the TBX1 locus in a cohort of 446 white patients with psychiatric disorders relevant to 22q11DS and 436 ethnically matched controls. The main diagnoses included schizophrenia (n = 226), schizoaffective disorder (n = 67), bipolar disorder (n = 82), and major depressive disorder (n = 29). We genotyped nine tag SNPs in this sample but did not observe significant differences in allele or haplotype frequencies in any of the analyzed groups (all affected, schizophrenia and schizoaffective disorder, schizophrenia alone, and bipolar disorder and major depressive disorder) compared with the control group. Based on these results we conclude that TBX1 variation does not make a strong contribution to the genetic etiology of nonsyndromic forms of psychiatric disorders commonly seen in patients with 22q11DS. 相似文献
110.
Nieto M Finn S Loda M Hahn WC 《The international journal of biochemistry & cell biology》2007,39(9):1562-1568
Prostate cancer is the most common, non-dermatologic cancer in men. Since prostate cancer is highly associated with increased age, the incidence of this disease is expected to increase as the population ages. In its initial stages prostate cancer depends upon the actions of androgen, and androgen deprivation therapy induces tumor regression. Currently, androgen deprivation is achieved by either surgical or chemical androgen blockade. Unfortunately, nearly all prostate cancer patients develop tumors that grow despite androgen blockade and ultimately relapse. Many alterations in prostate cancer cells contribute to this state. Although chemotherapy induces short remissions in some patients, there are no curative therapies for metastatic disease. This review summarizes our current understanding in androgen signaling and the mechanisms that allow tumor cells to bypass androgen manipulation therapy. The identification of novel survival pathways and effector molecules that drive androgen independent growth is necessary to develop effective therapies for advanced prostate cancers. 相似文献