全文获取类型
收费全文 | 195篇 |
免费 | 14篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1968年 | 3篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1958年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 0 毫秒
31.
Debbaut C Vierendeels J Casteleyn C Cornillie P Van Loo D Simoens P Van Hoorebeke L Monbaliu D Segers P 《Journal of biomechanical engineering》2012,134(1):011003
The perfusion of the liver microcirculation is often analyzed in terms of idealized functional units (hexagonal liver lobules) based on a porous medium approach. More elaborate research is essential to assess the validity of this approach and to provide a more adequate and quantitative characterization of the liver microcirculation. To this end, we modeled the perfusion of the liver microcirculation using an image-based three-dimensional (3D) reconstruction of human liver sinusoids and computational fluid dynamics techniques. After vascular corrosion casting, a microvascular sample (±0.134 mm(3)) representing three liver lobules, was dissected from a human liver vascular replica and scanned using a high resolution (2.6 μm) micro-CT scanner. Following image processing, a cube (0.15?×?0.15?×?0.15 mm(3)) representing a sample of intertwined and interconnected sinusoids, was isolated from the 3D reconstructed dataset to define the fluid domain. Three models were studied to simulate flow along three orthogonal directions (i.e., parallel to the central vein and in the radial and circumferential directions of the lobule). Inflow and outflow guidances were added to facilitate solution convergence, and good quality volume meshes were obtained using approximately 9?×?10(6) tetrahedral cells. Subsequently, three computational fluid dynamics models were generated and solved assuming Newtonian liquid properties (viscosity 3.5 mPa s). Post-processing allowed to visualize and quantify the microvascular flow characteristics, to calculate the permeability tensor and corresponding principal permeability axes, as well as the 3D porosity. The computational fluid dynamics simulations provided data on pressure differences, preferential flow pathways and wall shear stresses. Notably, the pressure difference resulting from the flow simulation parallel to the central vein (0-100 Pa) was clearly smaller than the difference from the radial (0-170 Pa) and circumferential (0-180 Pa) flow directions. This resulted in a higher permeability along the central vein direction (k(d,33)?=?3.64?×?10(-14) m(2)) in comparison with the radial (k(d,11)?=?1.56?×?10(-14) m(2)) and circumferential (k(d,22)?=?1.75?×?10(-14) m(2)) permeabilities which were approximately equal. The mean 3D porosity was 14.3. Our data indicate that the human hepatic microcirculation is characterized by a higher permeability along the central vein direction, and an about two times lower permeability along the radial and circumferential directions of a lobule. Since the permeability coefficients depend on the flow direction, (porous medium) liver microcirculation models should take into account sinusoidal anisotropy. 相似文献
32.
33.
Background
Determination and quantification of nucleic acid components in a mixture is usually accomplished by microarray approaches, where the mixtures are hybridized against specific probes. As an alternative, we propose here that a single sequencing reaction from a mixture of nucleic acids holds enough information to potentially distinguish the different components, provided it is known which components can occur in the mixture. 相似文献34.
35.
36.
37.
J. Mattanovich M. Ehrenhöfer C. Schafellner M. Tausz & E. Führer 《Journal of Applied Entomology》2001,125(8):425-431
Bark beetles, especially Ips typographus L. represent a severe biotic threat for spruce ( Picea abies [L.] Karst.) at low altitudes in Europe. We compared sulphur (total S, SO4 2− , glutathione, cysteine, methionine), nitrogen (total N, NO3 − , total protein, free amino acids), carbon, total phosphorus and PO4 3− , tree vigour index (TVI) and water content of the phloem after felling, and their dependent changes (tdc) with the breeding success of I. typographus . Twenty trees were classified according to age (34/90 years) and crown density (high/intermediate/low). Water content was higher in young trees than in old trees, higher in the crown than at breast height, and decreased significantly within the 8-week study period. In old trees, breeding success, length of mother galleries and SO4 2− were significantly higher, while total protein, NO3 − and water content were significantly lower than in young trees. Trees with intermediate crown density provided the best breeding success for I. typographus and had significantly higher arginine content and C/N ratio as well as low amounts of phosphate and glutamine. During the period of bark beetle breeding, total sulphur, glutathione, protein, NO3 − , aspartate, glutamine, glutamate, arginine and γ-aminobutyrate decreased significantly. The results support previous investigations that I. typographus develops best in physiologically weakened trees. 相似文献
38.
Diethard Köhler 《Molecular & general genetics : MGG》1958,89(3):437-447
Zusammenfassung Der Vererbungsmodus der Monözie bei Hanf wurde untersucht. Monözisten sind Pflanzen mit der Wuchsform der Weibchen aus diözischem Hanf; sie tragen anstelle einzelner oder mehrerer weiblicher Blüten männliche. Die zugrunde liegenden Faktoren sind als schwach wirksame männliche Realisatoren aufzufassen. Sie haben keinen Einfluß auf die Wuchsform und wirken sich bei Männchen nicht aus. Es sind 2 intermediäre additive und gleichsinnig wirkende Gene. Sie werden unabhängig voneinander und von den Faktoren, die die primären und sekundären Geschlechtsmerkmale im diözischen Hanf bestimmen, verteilt.Mit 4 TextabbildungenHerrn Professor Dr. Dr. h. c.R. Harder, meinem verehrten Lehrer, zum 70. Geburtstag gewidmet. 相似文献
39.
40.
Several thousand genes in the human genome have been linked to a heritable genetic disease. The majority of these appear to be nonessential genes (i.e., are not embryonically lethal when inactivated), and one could therefore speculate that they are late additions in the evolutionary lineage toward humans. Contrary to this expectation, we find that they are in fact significantly overrepresented among the genes that have emerged during the early evolution of the metazoa. Using a phylostratigraphic approach, we have studied the evolutionary emergence of such genes at 19 phylogenetic levels. The majority of disease genes was already present in the eukaryotic ancestor, and the second largest number has arisen around the time of evolution of multicellularity. Conversely, genes specific to the mammalian lineage are highly underrepresented. Hence, genes involved in genetic diseases are not simply a random subset of all genes in the genome but are biased toward ancient genes. 相似文献