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951.
Tine R Licht Max Hansen Anders Bergström Morten Poulsen Britta N Krath Jaroslaw Markowski Lars O Dragsted Andrea Wilcks 《BMC microbiology》2010,10(1):13
Background
Our study was part of the large European project ISAFRUIT aiming to reveal the biological explanations for the epidemiologically well-established health effects of fruits. The objective was to identify effects of apple and apple product consumption on the composition of the cecal microbial community in rats, as well as on a number of cecal parameters, which may be influenced by a changed microbiota. 相似文献952.
Liene Daukste Britta Basse Bruce C. Baguley David J.N. Wall 《Journal of theoretical biology》2009,260(4):563-571
There is increasing evidence that the growth of human tumours is driven by a small proportion of tumour stem cells with self-renewal properties. Multiplication of these cells leads to loss of self-renewal and after division for a finite number of times the cells undergo programmed cell death. Cell cycle times of human cancers have been measured in vivo and shown to vary in the range from two days to several weeks, depending on the individual. Cells cultured directly from tumours removed at surgery initially grow at a rate comparable to the in vivo rate but continued culture leads to the generation of cell lines that have shorter cycle times (1–3 days). It has been postulated that the more rapidly growing sub-population exhibits some of the properties of tumour stem cells and are the precursors of a slower growing sub-population that comprise the bulk of the tumour. We have previously developed a mathematical model to describe the behaviour of cell lines and we extend this model here to describe the behaviour of a system with two cell populations with different kinetic characteristics and a precursor–product relationship. The aim is to provide a framework for understanding the behaviour of cancer tissue that is sustained by a minor population of proliferating stem cells. 相似文献
953.
We have studied the acyl-chain conformation in stalk phases of model membranes by x-ray diffraction from oriented samples. As an equilibrium lipid phase induced by dehydration, the stalk or rhombohedral phase exhibits lipidic passages (stalks) between adjacent bilayers, representing a presumed intermediate state in membrane fusion. From the detailed analysis of the acyl-chain correlation peak, we deduce the structural parameters of the acyl-chain fluid above, at, and below the transition from the lamellar to rhombohedral state, at the molecular level. 相似文献
954.
Intracerebral Dialysis and the Blood-Brain Barrier 总被引:6,自引:1,他引:6
Irena Westergren Britta Nyström Anders Hamberger Barbro B. Johansson 《Journal of neurochemistry》1995,64(1):229-234
Abstract: The aim of the study was to evaluate how implantation of a dialysis probe influences the blood-brain barrier. Leakage of endogenous serum albumin was evaluated by Evans blue/albumin staining and by immunohistochemistry. The passage from blood to dialysate of two substances that normally do not pass into the brain, [3 H]inulin and glutamate, was studied 3 and 24 h after insertion of a dialysis probe. Evans blue, given 20 min before rats were killed, was observed around the probe and surrounding brain tissue. Albumin immunoreactivity was seen at considerable distance from the probe with larger spread at 24 h than at 3 h after probe insertion. Glutamate and [3 H]inulin were detected in the dialysate with no significant further increase of radioactivity after intracarotid infusion of protamine sulfate that enhances the permeability over the blood-brain barrier. When protamine was followed by infusion of glutamate, the concentrations of taurine increased in the dialysate in four of eight rats. That plasma constituents have access to the brain around the dialysis probe is essential to consider, particularly in studies using substances and drugs that do not pass an intact blood-brain barrier. 相似文献
955.
Virus-induced gene silencing as a tool for functional genomics in a legume species 总被引:14,自引:0,他引:14
Constantin GD Krath BN MacFarlane SA Nicolaisen M Johansen IE Lund OS 《The Plant journal : for cell and molecular biology》2004,40(4):622-631
Virus-induced gene silencing (VIGS) is an attractive reverse-genetics tool for studies of gene function. However, efficient VIGS has only been accomplished in a few plant species. In order to extend the application of VIGS, we examined whether a VIGS vector based on Pea early browning virus (PEBV) would produce recognizable phenotypes in Pisum sativum. A plasmid vector of PEBV was modified to allow agro-inoculation and insertion of heterologous sequences. cDNA fragments of the P. sativum phytoene desaturase (PDS), LEAFY (LFY) and KORRIGAN1 (KOR1) homologues were inserted into the PEBV RNA2 vector, replacing the genes required for nematode transmission. Pisum sativum inoculated with PEBV carrying a fragment of PsPDS developed characteristic photo-bleached leaves and this phenotype was associated with a significant reduction in PsPDS mRNA. The P. sativum homologue of LFY is known as UNIFOLIATA (UNI). Plants inoculated with PEBV carrying a fragment of UNI developed distorted flowers and leaves with modified architecture, which are also observed in UNI-mutants. In Arabidopsis thaliana, the KOR1-mutant is characterized by an extreme dwarf phenotype. Pisum sativum plants inoculated with PEBV carrying a fragment of PsKOR1 displayed a significant reduction in height and inhibition of root growth. The PEBV VIGS vector did not affect the ability of P. sativum to flower, set seeds, and form nodules characteristic of symbiosis with rhizobium. These results suggest that the PEBV vector can be applied to functional genomics in a legume species to study genes involved in a wide range of biological processes. 相似文献
956.
957.
Park HJ Ferko B Byun YH Song JH Han GY Roethl E Egorov A Muster T Seong B Kweon MN Song M Czerkinsky C Nguyen HH 《PloS one》2012,7(6):e39921
The nonstructural protein 1 (NS1) of influenza A virus (IAV) enables the virus to disarm the host cell type 1 IFN defense system. Mutation or deletion of the NS1 gene leads to attenuation of the virus and enhances host antiviral response making such live-attenuated influenza viruses attractive vaccine candidates. Sublingual (SL) immunization with live influenza virus has been found to be safe and effective for inducing protective immune responses in mucosal and systemic compartments. Here we demonstrate that SL immunization with NS1 deleted IAV (DeltaNS1 H1N1 or DeltaNS1 H5N1) induced protection against challenge with homologous as well as heterosubtypic influenza viruses. Protection was comparable with that induced by intranasal (IN) immunization and was associated with high levels of virus-specific antibodies (Abs). SL immunization with DeltaNS1 virus induced broad Ab responses in mucosal and systemic compartments and stimulated immune cells in mucosa-associated and systemic lymphoid organs. Thus, SL immunization with DeltaNS1 offers a novel potential vaccination strategy for the control of influenza outbreaks including pandemics. 相似文献
958.
There is both a fundamental and applied need to define expectations of changes in aquatic ecosystems due to global changes.
It is clear that programs using biological indicators and reference-based comparisons as the foundation for assessments are
likely to make increasingly erroneous decisions if the impacts of global change are ignored. Global changes influence all
aspects of water resource management decisions based on comparisons to reference conditions with impacts making it increasingly
problematic to find an “undisturbed” water body to define acceptable conditions of ecological integrity. Using a more objective
scale for characterizing reference conditions that is anchored in expectations for what would be attainable under undisturbed
conditions, such as the Biological Condition Gradient (BCG) is one approach that maintains consistent definitions for ecosystem
conditions. In addition, protection of reference stations and of unique or undisturbed aquatic resources is imperative, though
the scope of protection options is limited. Projections indicate that encroaching land use will affect 36–48% of current reference
surface waters by the year 2100. The interpretation of biological indicators is also at risk from global changes. Distinguishing
taxonomic attributes based on temperature or hydrologic preferences can be used to enhance the ability to make inferences
about global change effects compared to other stressors. Difficulties arise in categorizing unique indicators of global changes,
because of similarities in some of the temperature and hydrologic effects resulting from climate change, land use changes,
and water removal. In the quest for biological indicators that might be uniquely sensitive to one global stressor as an aid
in recognizing probable causes of ecosystem damage, the potential similarities in indicator responses among global and landscape-scale
changes needs to be recognized as a limiting factor. Many aspects of global changes are not tractable at the local to regional
scales at which water quality regulations are typically managed. Our ability to implement water policies through bioassessment
will require a shift in the scale of assessment, planning, and adaptations in order to fulfill our ultimate regulatory goals
of preserving good water quality and ecological integrity. Providing clear expectations of effects due to global change for
key species and communities in freshwater ecosystems will help water quality programs achieve their goals under changing environmental
conditions. 相似文献
959.
960.
Oxygen consumption of carp acclimated at 10 and 20° C has been measured under routine conditions. Some complications and precautions necessary in continuous flow respirometry are discussed. Routine V o2 at different levels of hypoxia have been determined. Individual variation leads to scatter in the data and different methods of plotting the relationship between V o2 and P o2 are proposed; attention is drawn to differences between inlet (or ambient) P o2 and inspired P o2 . Using certain criteria a 'critical' oxygen tension of about 95 mm Hg was found at 20° C; Q 10 values are about 2 at normoxia and some suggestions of an increase near to the critical oxygen tension were found. Blood samples from the dorsal aorta showed rising Pa,o2 of 16 mm Hg which increased to 70–80 mm Hg when P insp was 90 and they then fall as the inspired oxygen is lowered. During periods of deep hypoxia (25 mm Hg) blood lactate concentration increases steadily and indicates an increasing dependence on anaerobic mechanisms. 相似文献