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991.
Virginie Le Brun Wolfgang Friess Torsten Schultz-Fademrecht Silke Muehlau Patrick Garidel Dr. 《Biotechnology journal》2009,4(9):1305-1319
The purpose of the presented study is to understand the physicochemical properties of proteins in aqueous solutions in order to identify solution conditions with reduced attractive protein-protein interactions, to avoid the formation of protein aggregates and to increase protein solubility. This is assessed by measuring the osmotic second virial coefficient (B22), a parameter of solution non-ideality, which is obtained using self-interaction chromatography. The model protein is lysozyme. The influence of various solution conditions on B22 was investigated: protonation degree, ionic strength, pharmaceutical relevant excipients and combinations thereof. Under acidic solution conditions B22 is positive, favoring protein repulsion. A similar trend is observed for the variation of the NaCl concentration, showing that with increasing the ionic strength protein attraction is more likely. B22 decreases and becomes negative. Thus, solution conditions are obtained favoring attractive protein-protein interactions. The B22 parameter also reflects, in general, the influence of the salts of the Hofmeister series with regard to their salting-in/salting-out effect. It is also shown that B22 correlates with protein solubility as well as physical protein stability. 相似文献
992.
Stefanie Graewe Silke Retzlaff Nicole Struck Chris J. Janse Volker T. Heussler Dr. 《Biotechnology journal》2009,4(6):895-902
Fluorescent proteins have proven to be important tools for in vitro live imaging of parasites and for imaging of parasites within the living host by intravital microscopy. We observed that a red fluorescent transgenic malaria parasite of rodents, Plasmodium berghei-RedStar, is suitable for in vitro live imaging experiments but bleaches rapidly upon illumination in intravital imaging experiments using mice. We have therefore generated two additional transgenic parasite lines expressing the novel red fluorescent proteins tdTomato and mCherry, which have been reported to be much more photostable than first- and second-generation red fluorescent proteins including RedStar. We have compared all three red fluorescent parasite lines for their use in in vitro live and intravital imaging of P. berghei blood and liver parasite stages, using both confocal and wide-field microscopy. While tdTomato bleached almost as rapidly as RedStar, mCherry showed improved photostability and was bright in all experiments performed. 相似文献
993.
Silke Metzger Carolin Walter Olaf Riess Raymund A. C. Roos J?rgen E. Nielsen David Craufurd REGISTRY Investigators of the European Huntington’s Disease Network Huu Phuc Nguyen 《PloS one》2013,8(7)
The cause of Huntington disease (HD) is a polyglutamine repeat expansion of more than 36 units in the huntingtin protein, which is inversely correlated with the age at onset of the disease. However, additional genetic factors are believed to modify the course and the age at onset of HD. Recently, we identified the V471A polymorphism in the autophagy-related gene ATG7, a key component of the autophagy pathway that plays an important role in HD pathogenesis, to be associated with the age at onset in a large group of European Huntington disease patients. To confirm this association in a second independent patient cohort, we analysed the ATG7 V471A polymorphism in additional 1,464 European HD patients of the “REGISTRY” cohort from the European Huntington Disease Network (EHDN). In the entire REGISTRY cohort we could not confirm a modifying effect of the ATG7 V471A polymorphism. However, analysing a modifying effect of ATG7 in these REGISTRY patients and in patients of our previous HD cohort according to their ethnic origin, we identified a significant effect of the ATG7 V471A polymorphism on the HD age at onset only in the Italian population (327 patients). In these Italian patients, the polymorphism is associated with a 6-years earlier disease onset and thus seems to have an aggravating effect. We could specify the role of ATG7 as a genetic modifier for HD particularly in the Italian population. This result affirms the modifying influence of the autophagic pathway on the course of HD, but also suggests population-specific modifying mechanisms in HD pathogenesis. 相似文献
994.
Iris Eisermann Fabian Weihmann Jorrit-Jan Krijger Christian Kröling Gerd Hause Matthias Menzel Silke Pienkny Andreas Kiesow Holger B. Deising Stefan G. R. Wirsel 《Environmental microbiology》2019,21(12):4773-4791
To avoid pathogen-associated molecular pattern recognition, the hemibiotrophic maize pathogen Colletotrichum graminicola secretes proteins mediating the establishment of biotrophy. Targeted deletion of 26 individual candidate genes and seven gene clusters comprising 32 genes of C. graminicola identified a pathogenicity cluster (CLU5) of five co-linear genes, all of which, with the exception of CLU5b, encode secreted proteins. Targeted deletion of all genes of CLU5 revealed that CLU5a and CLU5d are required for full appressorial penetration competence, with virulence deficiencies independent of the host genotype and organ inoculated. Cytorrhysis experiments and microscopy showed that Δclu5a mutants form pressurized appressoria, but they are hampered in forming penetration pores and fail to differentiate a penetration peg. Whereas Δclu5d mutants elicited WT-like papillae, albeit at increased frequencies, papillae induced by Δclu5a mutants were much smaller than those elicited by the WT. Synteny of CLU5 is not only conserved in Colletotrichum spp. but also in additional species of Sordariomycetes including insect pathogens and saprophytes suggesting importance of CLU5 for fungal biology. Since CLU5a and CLU5d also occur in non-pathogenic fungi and since they are expressed prior to plant invasion and even in vegetative hyphae, the encoded proteins probably do not act primarily as effectors. 相似文献
995.
Lena‐Maria Holtz Silke Thoms Gerald Langer Dieter A. Wolf‐Gladrow 《Journal of phycology》2013,49(2):417-426
Over the last four decades, different hypotheses of Ca2+ and dissolved inorganic carbon transport to the intracellular site of calcite precipitation have been put forth for Emiliania huxleyi (Lohmann) Hay & Mohler. The objective of this study was to assess these hypotheses by means of mathematical models. It is shown that a vesicle‐based Ca2+ transport would require very high intravesicular Ca2+ concentrations, high vesicle fusion frequencies as well as a fast membrane recycling inside the cell. Furthermore, a kinetic model for the calcification compartment is presented that describes the internal chemical environment in terms of carbonate chemistry including calcite precipitation. Substrates for calcite precipitation are transported with different stoichiometries across the compartment membrane. As a result, the carbonate chemistry inside the compartment changes and hence influences the calcification rate. Moreover, the effect of carbonic anhydrase (CA) activity within the compartment is analyzed. One very promising model version is based on a Ca2+/H+ antiport, CO2 diffusion, and a CA inside the calcification compartment. Another promising model version is based on an import of Ca2+ and HCO3? and an export of H+. 相似文献
996.
Jürg Brendan Logue Silke Langenheder Anders F Andersson Stefan Bertilsson Stina Drakare Anders Lanzén Eva S Lindstr?m 《The ISME journal》2012,6(6):1127-1136
A central goal in ecology is to grasp the mechanisms that underlie and maintain biodiversity and patterns in its spatial distribution can provide clues about those mechanisms. Here, we investigated what might determine the bacterioplankton richness (BR) in lakes by means of 454 pyrosequencing of the 16S rRNA gene. We further provide a BR estimate based upon a sampling depth and accuracy, which, to our knowledge, are unsurpassed for freshwater bacterioplankton communities. Our examination of 22 669 sequences per lake showed that freshwater BR in fourteen nutrient-poor lakes was positively influenced by nutrient availability. Our study is, thus, consistent with the finding that the supply of available nutrients is a major driver of species richness; a pattern that may well be universally valid to the world of both micro- and macro-organisms. We, furthermore, observed that BR increased with elevated landscape position, most likely as a consequence of differences in nutrient availability. Finally, BR decreased with increasing lake and catchment area that is negative species–area relationships (SARs) were recorded; a finding that re-opens the debate about whether positive SARs can indeed be found in the microbial world and whether positive SARs can in fact be pronounced as one of the few ‘laws'' in ecology. 相似文献
997.
998.
Sascha H?velmann Silke H Hoffmann Ronald Kühne Ton ter Laak Helmut Reil?nder Thomas Beckers 《Biochemistry》2002,41(4):1129-1136
To investigate the impact of aromatic residues within transmembrane helix 6 (TMH6) of the human gonadotropin-releasing hormone receptor (GnRH-R) on agonist and antagonist binding, residues Y(283), Y(284), W(289), Y(290), W(291), and F(292) were exchanged to alanine and analyzed comprehensively in functional reporter gene and ligand binding assays. Whereas receptor mutants Y(283)A, Y(284)A, and W(291)A were capable of neither ligand binding nor signal transduction, mutants W(289)A, Y(290)A, and F(292)A were functional: the F(292)A mutant behaved like wild-type receptor, while mutants W(289)A and Y(290)A differentiated between agonistic and antagonistic ligands. On the basis of the high-resolution X-ray structure of bovine rhodopsin as well as available data on GnRH-R mutants, models for ligand-receptor interactions are proposed. The model for D-Trp(6)-GnRH (Triptorelin) binding, representing a superagonistic ligand, is in full accordance to available data. Furthermore, new interactions are proposed: pGlu(1) interacts with N(212) in transmembrane helix 5, Tyr(5) with Y(290), and D-Trp(6) with W(289). The binding behavior of mutants W(289)A and Y(290)A corresponds to the proposed binding model for the antagonist Cetrorelix. In summary, our data as presented indicate that Y(290) plays a key function in agonist but not antagonist binding. 相似文献
999.
1000.