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271.
272.
Gamma-fluorinated analogues of glutamic acid and glutamine are compounds of biological interest. Syntheses of such compounds are extensively reviewed in this article. 4-fluoroglutamic acid was prepared as a mixture of racemic diastereomers by Michael reaction, inverse-Michael reaction or by electrophilic / nucleophilic fluorination. Optically enriched 4-fluoroglutamic acids were obtained by several resolution techniques as well as by asymmetric methodologies using the chiral pool. 4-fluoroglutamine was prepared as a mixture of stereoisomers as well as in racemic erythro and threo forms from the corresponding 4-fluoroglutamic acids using aminolysis and conventional protection and deprotection strategies. Racemic 4,4-difluoroglutamic acid was synthesized by a nitroaldol reaction and its L-enantiomer obtained via three different asymmetric routes. Racemic 4,4-difluoroglutamic acid was converted into the corresponding 4,4-difluoroglutamine using a protection / aminolysis / deprotection sequence while N-Boc-L-4,4-difluoroglutamine was prepared directly from (R)-Garner's aldehyde using a Reformatsky reaction as the key step. 相似文献
273.
Pease LF Lipin DI Tsai DH Zachariah MR Lua LH Tarlov MJ Middelberg AP 《Biotechnology and bioengineering》2009,102(3):845-855
Here we characterize virus-like particles (VLPs) by three very distinct, orthogonal, and quantitative techniques: electrospray differential mobility analysis (ES-DMA), asymmetric flow field-flow fractionation with multi-angle light scattering detection (AFFFF-MALS) and transmission electron microscopy (TEM). VLPs are biomolecular particles assembled from viral proteins with applications ranging from synthetic vaccines to vectors for delivery of gene and drug therapies. VLPs may have polydispersed, multimodal size distributions, where the size distribution can be altered by subtle changes in the production process. These three techniques detect subtle size differences in VLPs derived from the non-enveloped murine polyomavirus (MPV) following: (i) functionalization of the surface of VLPs with an influenza viral peptide fragment; (ii) packaging of foreign protein internally within the VLPs; and (iii) packaging of genomic DNA internally within the VLPs. These results demonstrate that ES-DMA and AFFFF-MALS are able to quantitatively determine VLP size distributions with greater rapidity and statistical significance than TEM, providing useful technologies for product development and process analytics. 相似文献
274.
Selvarasu S Ow DS Lee SY Lee MM Oh SK Karimi IA Lee DY 《Biotechnology and bioengineering》2009,102(3):923-934
Genome-scale flux analysis of Escherichia coli DH5alpha growth in a complex medium was performed to investigate the relationship between the uptake of various nutrients and their metabolic outcomes. During the exponential growth phase, we observed a sequential consumption order of serine, aspartate and glutamate in the complex medium as well as the complete consumption of key carbohydrate nutrients, glucose and trehalose. Based on the consumption and production rates of the measured metabolites, constraints-based flux analysis of a genome-scale E. coli model was then conducted to elucidate their utilization in the metabolism. The in silico analysis revealed that the cell exploited biosynthetic precursors taken up directly from the complex medium, through growth-related anabolic pathways. This suggests that the cell could be functioning in an energetically more efficient manner by reducing the energy needed to produce amino acids. The in silico simulation also allowed us to explain the observed rapid consumption of serine: excessively consumed external serine from the complex medium was mainly converted into pyruvate and glycine, which in turn, led to the acetate accumulation. The present work demonstrates the application of an in silico modeling approach to characterizing microbial metabolism under complex medium condition. This work further illustrates the use of in silico genome-scale analysis for developing better strategies related to improving microbial growth and enhancing the productivity of desirable metabolites. 相似文献
275.
Tom Drader Kara Johnson Robert Brueggeman Dave Kudrna Andris Kleinhofs 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,118(4):811-820
Approaches utilizing microlinearity between related species allow for the identification of syntenous regions and orthologous
genes. Within the barley Chromosome 7H(1) is a region of high recombination flanked by molecular markers cMWG703 and MWG836.
We present the constructed physical contigs linked to molecular markers across this region using bacterial artificial chromosomes
(BAC) from the cultivar Morex. Barley expressed sequence tags (EST), identified by homology to rice chromosome 6 between the
rice molecular markers C425A and S1434, corresponded to the barley syntenous region of Chromosome 7H(1) Bins 2–5 between molecular
markers cMWG703-MWG836. Two hundred and thirteen ESTs were genetically mapped yielding 267 loci of which 101 were within the
target high recombination region while 166 loci mapped elsewhere. The 101 loci were joined by 43 other genetic markers resulting
in a highly saturated genetic map. In order to develop a physical map of the region, ESTs and all other molecular markers
were used to identify Morex BAC clones. Seventy-four BAC contigs were formed containing 2–102 clones each with an average
of 19 and a median of 13 BAC clones per contig. Comparison of the BAC contigs, generated here, with the Barley Physical Mapping
Database contigs, resulted in additional overlaps and a reduction of the contig number to 56. Within cMWG703-MWG836 are 24
agriculturally important traits including the seedling spot blotch resistance locus, Rcs5. Genetic and physical analysis of this region and comparison to rice indicated an inversion distal of the Rcs5 locus. Three BAC clone contigs spanning the Rcs5 locus were identified.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
276.
Kunjan R. Dave Richard Anthony DeFazio Ami P. Raval Oleksandr Dashkin Isabel Saul Kimberly E. Iceman† Miguel A. Perez-Pinzon‡ Kelly L. Drew† 《Journal of neurochemistry》2009,110(4):1170-1179
During the pre-hibernation season, arctic ground squirrels (AGS) can tolerate 8 min of asphyxial cardiac arrest (CA) without detectable brain pathology. Better understanding of the mechanisms regulating innate ischemia tolerance in AGS has the potential to facilitate the development of novel prophylactic agents to induce ischemic tolerance in patients at risk of stroke or CA. We hypothesized that neuroprotection in AGS involves robust maintenance of ion homeostasis similar to anoxia-tolerant turtles. Ion homeostasis was assessed by monitoring ischemic depolarization (ID) in cerebral cortex during CA in vivo and during oxygen glucose deprivation in vitro in acutely prepared hippocampal slices. In both models, the onset of ID was significantly delayed in AGS compared with rats. The epsilon protein kinase C (εPKC) is a key mediator of neuroprotection and inhibits both Na+ /K+ -ATPase and voltage-gated sodium channels, primary mediators of the collapse of ion homeostasis during ischemia. The selective peptide inhibitor of εPKC (εV1-2) shortened the time to ID in brain slices from AGS but not in rats despite evidence that εV1-2 decreased activation of εPKC in brain slices from both rats and AGS. These results support the hypothesis that εPKC activation delays the collapse of ion homeostasis during ischemia in AGS. 相似文献
277.
Dave Goulson 《Plant Ecology》2009,205(2):201-211
The relative importance of floral versus ecological isolation in preventing introgression remains unclear. This study examines
whether ecological isolation can explain the continuing integrity of Silene dioica and S. latifolia where floral isolation is weak and hybrids are fully viable. Eighteen small replicate founder populations of 6 individuals
(3 males and 3 females) of either S. latifolia, S. dioica or hybrids were created in woodland and in open sites in southern UK. Survival, reproduction and introgression of these populations
were examined over 9 years. S. latifolia and hybrid plants suffered higher mortality than S. dioica in woodland. In open sites, there was extensive introgression, with few or no pure S. latifolia or S. dioica surviving by the end of the experiment. The experiment suggests that the integrity of S. dioica is maintained by its ability to survive in shaded habitats where S. latifolia and hybrids cannot persist. However, how S. latifolia survives as a distinct species in the study area remains a puzzle. Immigration from regions where S. latifolia occurs in isolation (i.e. large-scale ecological isolation) may balance introgression in the study area. 相似文献
278.
279.