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Interaction of the TEK and TIE receptor tyrosine kinases during cardiovascular development. 总被引:8,自引:0,他引:8
TEK (TIE2) and TIE (TIE1) are structurally related receptor tyrosine kinases expressed in endothelial cells and their precursors. Genetic studies in the mouse have revealed essential functions of both receptors in angiogenic expansion of the vasculature during development. As previously shown, mouse embryos homozygous for a disrupted Tek allele die by day 10.5 of embryogenesis due to endocardial defects, hemorrhaging, and impaired vascular network formation. Furthermore, TIE is required cell autonomously for endothelial cell survival and extension of the vascular network during late embryogenesis. Here we have investigated possible redundancy in the TEK and TIE signalling pathways during vascular development. Vasculogenesis proceeds normally in embryos lacking both TEK and TIE, although such embryos die early in gestation of multiple cardiovascular defects. Mosaic analysis revealed an absolute requirement for TEK in the endocardium at E10.5, whereas TEK and TIE are dispensable for the initial assembly of the rest of the vasculature. In contrast, both receptors are required in the microvasculature during late organogenesis and in essentially all blood vessels of the adult. This analysis demonstrates essential functions for TEK and TIE in maintaining the integrity of the mature vasculature. 相似文献
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Restricted lateral mobility of plasma membrane CD4 impairs HIV-1 envelope glycoprotein mediated fusion 总被引:2,自引:0,他引:2
Rawat SS Zimmerman C Johnson BT Cho E Lockett SJ Blumenthal R Puri A 《Molecular membrane biology》2008,25(1):83-94
We investigated the effect of receptor mobility on HIV-1 envelope glycoprotein (Env)-triggered fusion using B16 mouse melanoma cells that are engineered to express CD4 and CXCR4 or CCR5. These engineered cells are resistant to fusion mediated CD4-dependent HIV-1 envelope glycoprotein. Receptor mobility was measured by fluorescence recovery after photobleaching (FRAP) using either fluorescently-labeled antibodies or transient expression of GFP-tagged receptors in the cells. No significant differences between B16 and NIH3T3 (fusion-permissive) cells were seen in lateral mobility of CCR5 or lipid probes. By contrast CD4 mobility in B16 cells was about seven-fold reduced compared to its mobility in fusion-permissive NIH3T3 cells. However, a CD4 mutant (RA5) that localizes to non-raft membrane microdomains exhibited a three-fold increased mobility in B16 cells as compared with WT-CD4. Interestingly, the B16 cells expressing the RA5 mutant (but not the wild type CD4) and coreceptors supported HIV-1 Env-mediated fusion. Our data demonstrate that the lateral mobility of CD4 is an important determinant of HIV-1 fusion/entry. 相似文献
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Single-nucleotide polymorphism (SNP) arrays have become a popular technology for disease-association studies, but they also have potential for studying the genetic differentiation of human populations. Application of the Affymetrix GeneChip Human Mapping 500K Array Set to a population of 102 individuals representing the major ethnic groups in the United States (African, Asian, European, and Hispanic) revealed patterns of gene diversity and genetic distance that reflected population history. We analyzed allelic frequencies at 388,654 autosomal SNP sites that showed some variation in our study population and 10% or fewer missing values. Despite the small size (23-31 individuals) of each subpopulation, there were no fixed differences at any site between any two subpopulations. As expected from the African origin of modern humans, greater gene diversity was seen in Africans than in either Asians or Europeans, and the genetic distance between the Asian and the European populations was significantly lower than that between either of these two populations and Africans. Principal components analysis applied to a correlation matrix among individuals was able to separate completely the major continental groups of humans (Africans, Asians, and Europeans), while Hispanics overlapped all three of these groups. Genes containing two or more markers with extraordinarily high genetic distance between subpopulations were identified as candidate genes for health differences between subpopulations. The results show that, even with modest sample sizes, genome-wide SNP genotyping technologies have great promise for capturing signatures of gene frequency difference between human subpopulations, with applications in areas as diverse as forensics and the study of ethnic health disparities. 相似文献
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Life cycle assessment of Australian automotive door skins 总被引:1,自引:0,他引:1
Prateek Puri Paul Compston Victor Pantano 《The International Journal of Life Cycle Assessment》2009,14(5):420-428
Background, aim, and scope Policy initiatives, such as the EU End of Life Vehicle (ELV) Directive for only 5% landfilling by 2015, are increasing the
pressure for higher material recyclability rates. This is stimulating research into material alternatives and end-of-life
strategies for automotive components. This study presents a Life Cycle Assessment (LCA) on an Australian automotive component,
namely an exterior door skin. The functional unit for this study is one door skin set (4 exterior skins). The material alternatives
are steel, which is currently used by Australian manufacturers, aluminium and glass-fiber reinforced polypropylene composite.
Only the inputs and outputs relative to the door skin production, use and end-of-life phases were considered within the system
boundary. Landfill, energy recovery and mechanical recycling were the end-of-life phases considered. The aim of the study
is to highlight the most environmentally attractive material and end-of-life option.
Methods The LCA was performed according to the ISO 14040 standard series. All information considered in this study (use of fossil
and non fossil based energy resources, water, chemicals etc.) were taken up in in-depth data. The data for the production,
use and end-of-life phases of the door skin set was based upon softwares such as SimaPro and GEMIS which helped in the development
of the inventory for the different end-of-life scenarios. In other cases, the inventory was developed using derivations obtained
from published journals. Some data was obtained from GM-Holden and the Co-operative research Centre for Advanced Automotive
Technology (AutoCRC), in Australia. In cases where data from the Australian economy was unavailable, such as the data relating
to energy recovery methods, a generic data set based on European recycling companies was employed. The characterization factors
used for normalization of data were taken from (Saling et. al. Int J Life Cycle Assess 7(4):203–218 2002) which detailed the method of carrying out an LCA.
Results The production phase results in maximum raw material consumption for all materials, and it is higher for metals than for the
composite. Energy consumption is greatest in the use phase, with maximum consumption for steel. Aluminium consumes most energy
in the production phase. Global Warming Potential (GWP) also follows a trend similar to that of energy consumption. Photo
Oxidants Creation Potential (POCP) is the highest for the landfill scenario for the composite, followed by steel and aluminium.
Acidification Potential (AP) is the highest for all the end-of-life scenarios of the composite. Ozone Depletion Potential
(ODP) is the highest for the metals. The net water emissions are also higher for composite in comparison to metals despite
high pollution in the production phases of metallic door skins. Solid wastes are higher for the metallic door skins.
Discussion The composite door skin has the lowest energy consumption in the production phase, due to the low energy requirements during
the manufacturing of E-glass and its fusion with polypropylene to form sheet molding compounds. In general, the air emissions
during the use phase are strongly dependent on the mass of the skins, with higher emissions for the metals than for the composite.
Material recovery through recycling is the highest in metals due to efficient separation techniques, while mechanical recycling
is the most efficient for the composite. The heavy steel skins produce the maximum solid wastes primarily due to higher fuel
consumption. Water pollution reduction benefit is highest in case of metals, again due to the high efficiency of magnetic
separation technique in the case of steel and eddy current separation technique in the case of aluminium. Material recovery
in these metals reduces the amount of water needed to produce a new door skin set (water employed mainly in the ingot casting
stage). Moreover, the use of heavy metals, inorganic salts and other chemicals is minimized by efficient material recovery.
Conclusions The use of the studied type of steel for the door skins is a poor environmental option in every impact category. Aluminium
and composite materials should be considered to develop a more sustainable and energy efficient automobile. In particular,
this LCA study shows that glass-fiber composite skins with mechanical recycling or energy recovery method could be environmentally
desirable, compared to aluminium and steel skins. However, the current limit on the efficiency of recycling is the prime barrier
to increasing the sustainability of composite skins.
Recommendations and perspectives The study is successful in developing a detailed LCA for the three different types of door skin materials and their respective
recycling or end-of-life scenarios. The results obtained could be used for future work on an eco-efficiency portfolio for
the entire car. However, there is a need for a detailed assessment of toxicity and risk potentials arising from each of the
four different types of door skin sets. This will require greater communication between academia and the automotive industry
to improve the quality of the LCA data. Sensitivity analysis needs to be performed such as the assessment of the impact of
varying substitution factors on the life cycle of a door skin. Incorporation of door skin sets made of new biomaterials need
to be accounted for as another functional unit in future LCA studies.
Discussion contributions to this article from the readership would the highly welcome. The authors 相似文献