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91.
All living organisms on earth are almost totally made up of biomolecules of only one chiral form. For example, proteins are built almost exclusively of L-amino acids, and sugars are composed of D-saccharides, a fact that is usually referred to as biohomochirality. Its origin is the center of numerous investigations and theories but is not really elucidated yet. The results of experimental investigations of peptide formation in a prebiotically relevant scenario, as described in this paper, give indications on a possible pathway for the synthesis of homochiral L-peptides in the course of the Salt-induced Peptide Formation (SIPF) reaction. 相似文献
92.
Nahrstedt H Waldeck J Gröne M Eichstädt R Feesche J Meinhardt F 《Journal of biotechnology》2005,119(3):245-254
By introducing defined deletions in recA and an essential sporulation gene (spoIV), stable mutant strains of Bacillus licheniformis were obtained which are totally asporogenous and severely affected in DNA repair, and thus being UV-hypersensitive. Studies on growth in various liquid media as well as on amylase production revealed no differences of the mutants when compared to the wild type. Hence, such genes appear to be suitable disruption targets for achieving passive biological containment in this industrially exploited species. 相似文献
93.
94.
The removal of the signal peptide from a precursor protein is a crucial step of protein secretion. In order to improve Bacillus megaterium as protein production and secretion host, the influence of homologous type I signal peptidase SipM overproduction on recombinant Leuconostoc mesenteroides dextransucrase DsrS synthesis and export was investigated. The dsrS gene was integrated as a single copy into the chromosomal bgaM locus encoding beta-galactosidase. Desired clones were identified by blue-white selection. In this strain, the expression of sipM from a multicopy plasmid using its own promoter increased the amount of secreted DsrS 3.7-fold. This increase in protein secretion by SipM overproduction was next transferred to a high level DsrS production strain using a multicopy plasmid encoding sipM with its natural promoter and dsrS under control of a strong xylose-inducible promoter. No further increase in DsrS export were observed when this vector was carrying two sipM copies. Similarly, bicistronic sipM and dsrS high level expression did not enhance DsrS secretion, indicating the natural limitation of the approach. Interestingly, SipM-enhanced DsrS secretion also resulted in an overall increase of DsrS production. 相似文献
95.
A network of stimulatory and inhibitory Galpha-subunits regulates olfaction in Caenorhabditis elegans 总被引:3,自引:0,他引:3
The two pairs of sensory neurons of C. elegans, AWA and AWC, that mediate odorant attraction, express six Galpha-subunits, suggesting that olfaction is regulated by a complex signaling network. Here, we describe the cellular localization and functions of the six olfactory Galpha-subunits: GPA-2, GPA-3, GPA-5, GPA-6, GPA-13, and ODR-3. All except GPA-6 localize to sensory cilia, suggesting a direct role in sensory transduction. GPA-2, GPA-3, GPA-5, and GPA-6 are also present in cell bodies and axons and GPA-5 specifically localizes to synaptic sites. Analysis of animals with single- to sixfold loss-of-function mutations shows that olfaction involves a balance between multiple stimulatory and inhibitory signals. ODR-3 constitutes the main stimulatory signal and is sufficient for the detection of odorants. GPA-3 forms a second stimulatory signal in the AWA and AWC neurons, also sufficient for odorant detection. In AWA, signaling is suppressed by GPA-5. In AWC, GPA-2 and GPA-13 negatively and positively regulate signaling, respectively. Finally, we show that only ODR-3 plays a role in cilia morphogenesis. Defects in this process are, however, independent of olfactory behavior. Our findings reveal the existence of a complex signaling network that controls odorant detection by C. elegans. 相似文献
96.
Following several years of occasional occurrence, several wolvesCanis lupus Linnaeus, 1758 have established a resident population in northeastern Saxony (Eastern Germany). From 2001 to 2003, we collected
and analysed 192 scats ofC. lupus. Results of our study are expressed as the frequency of occurrence of prey species and the percentage of biomass consumed
using coefficients of digestibility as well as two variants of an equation for prey mass per collectable scat. Diet composition
of the wolves was restricted to a few food items, mostly wild ungulates. These remains were found in 97% of the scats, representing
99% of the biomass consumed by the wolves. Roe deerCapreolus capreolus was the most frequent and most important prey, constituting nearly of one half the biomass. Red deerCervus elaphus was recorded in one-third of the samples, followed by wild boarSus scrofa, mouflonOvis am mon musimon and brown hareLepus europaeus. Compared with game occurrence, roe deer was clearly preferred over the other species. A difference between winter and summer
diets was mainly due to the high occurrence of young wild boar in summer. The general diet pattern of the wolf in Saxony corresponds
with that found in the naturally occurring populations in Europe. 相似文献
97.
In this work, two different genetic algorithms were applied to improve culture media composition for the autotrophic cyanobacteria Synechococcus PCC 7942. Biomass yield and conversion of the asymmetric reduction of 2', 3', 4', 5', 6'-pentafluoroacetophenone were considered as simultaneous objectives, resulting in a multi-objective optimization problem. Even when similar performances of both algorithms were observed, it could be shown that a novel strength pareto approach was able to achieve remarkable results with a reduced number of experiments (160 instead of 320). Handling a high number of media components (13), their concentrations were adjusted, delivering high improvements in comparison to the standard BG 11 culture media. The quality of the Synechococcus biocatalyst could be increased up to fivefold compared to the initial state of the optimization. 相似文献
98.
99.
Beyeen AD Adzemovic MZ Ockinger J Stridh P Becanovic K Laaksonen H Lassmann H Harris RA Hillert J Alfredsson L Celius EG Harbo HF Kockum I Jagodic M Olsson T 《Journal of immunology (Baltimore, Md. : 1950)》2010,185(11):6883-6890
Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the CNS. Recent advances in whole-genome screening tools have enabled discovery of several MS risk genes, the majority of which have known immune-related functions. However, disease heterogeneity and low tissue accessibility hinder functional studies of established MS risk genes. For this reason, the MS model experimental autoimmune encephalomyelitis (EAE) is often used to study neuroinflammatory disease mechanisms. In this study, we performed high-resolution linkage analysis in a rat advanced intercross line to identify an EAE-regulating quantitative trait locus, Eae29, on rat chromosome 1. Eae29 alleles from the resistant strain both conferred milder EAE and lower production of proinflammatory molecules in macrophages, as demonstrated by the congenic line, DA.PVG-Eae29 (Dc1P). The soluble IL-22R α2 gene (Il-22ra2) lies within the Eae29 locus, and its expression was reduced in Dc1P, both in activated macrophages and splenocytes from immunized rats. Moreover, a single nucleotide polymorphism located at the end of IL-22RA2 associated with MS risk in a combined Swedish and Norwegian cohort comprising 5019 subjects, displaying an odds ratio of 1.26 (p = 8.0 × 10(-4)). IL-22 and its receptors have been implicated in chronic inflammation, suggesting that IL-22RA2 regulates a central immune pathway. Through a combined approach including genetic and immunological investigation in an animal model and large-scale association studies of MS patients, we establish IL-22RA2 as an MS risk gene. 相似文献
100.
Abdallah AM Verboom T Hannes F Safi M Strong M Eisenberg D Musters RJ Vandenbroucke-Grauls CM Appelmelk BJ Luirink J Bitter W 《Molecular microbiology》2006,62(3):667-679
Mycobacterial genomes contain two unique gene families, the so-called PE and PPE gene families, which are highly expanded in the pathogenic members of this genus. Here we report that one of the PPE proteins, i.e. PPE41, is secreted by pathogenic mycobacteria, both in culture and in infected macrophages. As PPE41 lacks a signal sequence a dedicated secretion system must be involved. A single gene was identified in Mycobacterium marinum that showed strongly reduced PPE41 secretion. This gene was located in a gene cluster whose predicted proteins encode components of an ESAT-6-like secretion system. This cluster, designated ESX-5, is conserved in various pathogenic mycobacteria, but not in the saprophytic species Mycobacterium smegmatis. Therefore, different regions of this cluster were introduced in M. smegmatis. Only introduction of the complete ESX-5 locus resulted in efficient secretion of heterologously expressed PPE41. This PPE secretion system is also involved in the virulence of pathogenic mycobacteria, as the ESX-5 mutant of M. marinum was affected in spreading to uninfected macrophages. 相似文献