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81.
Schoustra SE Debets AJ Slakhorst M Hoekstra RF 《Journal of evolutionary biology》2006,19(4):1115-1127
We have studied compensatory evolution in a fludioxonil resistant mutant of the filamentous fungus Aspergillus nidulans. In an evolution experiment lasting for 27 weeks (about 3000 cell cycles) 35 parallel strains of this mutant evolved in three different environmental conditions. Our results show a severe cost of resistance (56%) in the absence of fludioxonil and in all conditions the mutant strain was able to restore fitness without loss of the resistance. In several cases, the evolved strain reached a higher fitness than the original sensitive ancestor. Fitness compensation occurred in one, two or three discrete steps. Genetic analysis of crosses between different evolved strains and between evolved and ancestral strains revealed interaction between compensatory mutations and provided information on the number of loci involved in fitness compensation. In addition, we discuss the opportunities for the experimental study of evolutionary processes provided by the filamentous fungus A. nidulans. 相似文献
82.
In the central nervous system, a multilayered membrane layer known as the myelin sheath enwraps axons, and is required for optimal saltatory signal conductance. The sheath develops from membrane processes that extend from the plasma membrane of oligodendrocytes and displays a unique lipid and protein composition. Myelin biogenesis is carefully regulated, and multiple transport pathways involving a variety of endosomal compartments are involved. Here we briefly summarize how the major myelin proteins proteolipid protein and myelin basic protein reach the sheath, and highlight potential mechanisms involved, including the role of myelin specific lipids and cell polarity related transport pathways. 相似文献
83.
The complex nature of blood flow in the human arterial system is still gaining more attention, as it has become clear that cardiovascular diseases localize in regions of complex geometry and complex flow fields. In this article, we demonstrate that the lattice Boltzmann method can serve as a mesoscopic computational hemodynamic solver. We argue that it may have benefits over the traditional Navier-Stokes techniques. The accuracy of the method is tested by studying time-dependent systolic flow in a 3D straight rigid tube at typical hemodynamic Reynolds and Womersley numbers as an unsteady flow benchmark. Simulation results of steady and unsteady flow in a model of the human aortic bifurcation reconstructed from magnetic resonance angiography, are presented as a typical hemodynamic application. 相似文献
84.
Gutala R Carvalho-Silva DR Jin L Yngvadottir B Avadhanula V Nanne K Singh L Chakraborty R Tyler-Smith C 《Human genetics》2006,120(4):543-551
Arab forces conquered the Indus Delta region in 711 AD and, although a Muslim state was established there, their influence was barely felt in the rest of South Asia at that time. By the end of the tenth century, Central Asian Muslims moved into India from the northwest and expanded throughout the subcontinent. Muslim communities are now the largest minority religion in India, comprising more than 138 million people in a predominantly Hindu population of over one billion. It is unclear whether the Muslim expansion in India was a purely cultural phenomenon or had a genetic impact on the local population. To address this question from a male perspective, we typed eight microsatellite loci and 16 binary markers from the Y chromosome in 246 Muslims from Andhra Pradesh, and compared them to published data on 4,204 males from East Asia, Central Asia, other parts of India, Sri Lanka, Pakistan, Iran, the Middle East, Turkey, Egypt and Morocco. We find that the Muslim populations in general are genetically closer to their non-Muslim geographical neighbors than to other Muslims in India, and that there is a highly significant correlation between genetics and geography (but not religion). Our findings indicate that, despite the documented practice of marriage between Muslim men and Hindu women, Islamization in India did not involve large-scale replacement of Hindu Y chromosomes. The Muslim expansion in India was predominantly a cultural change and was not accompanied by significant gene flow, as seen in other places, such as China and Central Asia.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.Ramana Gutala and Denise R. Carvalho-Silva contributed equally to the article. 相似文献
85.
Maier O van der Heide T Johnson R de Vries H Baron W Hoekstra D 《Experimental cell research》2006,312(4):500-511
Formation of the paranodal axo-glial junction requires the oligodendrocyte-specific 155-kDa isoform of neurofascin (NF155). Here, we report the presence of two peptides in cultured oligodendrocytes, which are recognized by distinct NF155-specific antibodies and correspond to a membrane anchor of 30 kDa and a 125 kDa peptide, which is shed from the cells, indicating that it consists of the NF155 ectodomain. Transfection of OLN-93 cells with NF155 verified that both peptides originate from NF155 cleavage, and we present evidence that metalloproteases mediate NF155 processing. Interestingly, metalloprotease activity is required for NF155 transport into oligodendrocyte processes supporting the functional significance of NF155 cleavage. To further characterize NF155 cleavage and function, we transfected MDCK cells with NF155. Although ectodomain shedding was observed in polarized and non-polarized MDCK cells, surface localization of NF155 was restricted to the lateral membrane of polarized cells consistent with a role in cell-cell adhesion. Aggregation assays performed with OLN-93 cells confirmed that NF155 accelerates cell-cell adhesion in a metalloprotease-dependent manner. The physiological relevance of NF155 processing is corroborated by the presence of NF155 cleavage products in heavy myelin, suggesting a role of NF155 ectodomain shedding for the generation and/or stabilization of the nodal/paranodal architecture. 相似文献
86.
Approximately 10% of all examined 668 representatives of black Aspergillus species, independent of worldwide location, were infected with double-stranded RNA (dsRNA) mycoviruses. These isometric viruses (25-40 nm diameter) contained a variety of often multiple segments of different dsRNA sizes ranging from 0.8 to 4.4 kb in size. In one strain the virus shows clear visible effects on its host with non-sporulating sectors. We quantified the fitness costs of these and more 'cryptic' virus infections on mycelial growth rate and spore production, and on competitive ability with respect to other strains under different growth conditions. Mycovirus infection proved detrimental in all these measures. The reduced success in interference competition due to mycovirus infection belies co-evolution of mycovirus and host to a mutually beneficial symbiosis, like in killer virus systems in yeast and smut and agrees more to recent infections. For a stable virus infection frequency in the black Aspergillus population, fitness costs and spontaneous loss should be balanced with new infections. Implications of even small viral fitness effects combined with the observed transmission limits for host and mycovirus are discussed. 相似文献
87.
Spatial structure is thought to be an important factor influencing the emergence and maintenance of genetic diversity. Previous studies have demonstrated that environmental heterogeneity, provided by spatial structure, leads to adaptive radiation of populations. In the present study, we investigate not only the impact of environmental heterogeneity on adaptive radiation, but also of population fragmentation and niche construction. Replicate populations founded by a single genotype of Escherichia coli were allowed to evolve for 900 generations by serial transfer in either a homogeneous environment, or a spatially structured environment that was either kept intact or destroyed with each daily transfer. Only populations evolving in the structured environment with intact population structure diversified: clones are significantly divergent in sugar catabolism, and show frequency-dependent fitness interactions indicative of stable coexistence. These findings demonstrate an important role for population fragmentation, a consequence of population structure in spatially structured environments, on the diversification of populations. 相似文献
88.
Vesicles prepared from cellular plasma membranes are widely used in science for different purposes. The outer membrane leaflet differs from the inner membrane leaflet of the vesicle, and during vesicle preparation procedures two types of vesicles will be generated: right-side-out vesicles, of which the outer leaflet is topologically equivalent to the outer monolayer of the cellular plasma membrane, and inside-out vesicles. Because two populations of vesicles exist, sidedness information of the vesicle preparation is indispensable. This note focuses on the ins and outs of sidedness determination of vesicles and compares various methodologies used to establish this ratio. 相似文献
89.
Menno Hoekstra Ronald J. van der Sluis Johan Kuiper Theo J.C. Van Berkel 《The Journal of nutritional biochemistry》2012,23(6):622-628
MicroRNAs modulate processes associated with cell cycle control and differentiation. Here we explored the potential of microRNAs in the modulation of hepatic lipid metabolism and the development of nonalcoholic fatty liver disease.MicroRNA profiles of hepatocytes from low-density lipoprotein (LDL) receptor knockout mice fed a chow diet or a hypertriglyceridemia/fatty liver-inducing Western-type diet (WTD) were determined using quantitative real-time polymerase chain reaction. Ninety-seven of 103 microRNAs measured were expressed by hepatocytes and low variability between hepatocyte pools was observed. Feeding WTD coincided with a marked fivefold decrease in the relative expression level of miR-216 (P<.05) and miR-302a (P<.01). Interestingly, an increased hepatic miR-216 expression was detected in response to fasting. MicroRNA/biological function linkage analysis suggested that the change in hepatocyte microRNA profiles in response to high dietary lipid levels is associated with changes in cell cycle control and proliferation. In accordance with a diminished miR-302a expression on the WTD, hepatocyte mRNA expression levels of miR-302a target genes ABCA1 and in particular ELOVL6 were increased in response to WTD (twofold to ninefold). This suggests a role for miR-302a in hepatic cholesterol, fatty acid and glucose metabolism.In conclusion, we have shown that fatty liver development in LDL receptor knockout mice is associated with a significant change in the hepatocyte microRNA profile, i.e., a fivefold decrease in miR-216 and miR-302a expression. Based upon our comparative gene and microRNA expression studies it is anticipated that miR-302a may prove to be a valuable therapeutic target in the regulation of hepatic fatty acid utilization and insulin resistance. 相似文献
90.
Stefan TG Bruijnen Mignon AC van der Weijden Joannes P Klein Otto S Hoekstra Ronald Boellaard J Christiaan van Denderen Ben AC Dijkmans Alexandre E Voskuyl Irene E van der Horst-Bruinsma Conny J van der Laken 《Arthritis research & therapy》2012,14(2):R71