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81.
The Bacillus cereus bceT enterotoxin sequence reappraised 总被引:2,自引:0,他引:2
Bacillus cereus is a known opportunistic human pathogen belonging to the B. cereus group. Establishment of the pathogenesis most likely involves several gene products. One of these gene products, a single gene component named bceT, has been cloned and described from B. cereus B-4ac [Agata et al., Microbiology 141 (1995) 983-988]. However, our sequences of the bceT region from 16 B. cereus group strains showed inconsistency with the published bceT sequence. Only part of the bceT sequence had homology to our sequences. This initiated a more thorough investigation of the bceT sequence. Restriction site search and database searches intimated that the cloned bceT was created by an incidental joining of four DNA fragments during ligation. One of these fragments had 93% homology to an open reading frame (ORF 101) located within the pathogenic island of the Bacillus anthracis pXO1 virulence plasmid. We suggest that the reported enterotoxic activity of the original cloned bceT construct could be due to either the fusion gene or the fragment with homology to ORF 101 in pXO1. 相似文献
82.
The patchwork nature of rolling-circle plasmids: comparison of six plasmids from two distinct Bacillus thuringiensis serotypes 总被引:1,自引:0,他引:1
Bacillus thuringiensis, the entomopathogenic bacteria from the Bacillus cereus group, harbors numerous extrachromosomal molecules whose sizes vary from 2 to more than 200kb. Apart from the genes coding for the biopesticide delta-endotoxins located on large plasmids, little information has been obtained on these plasmids and their contribution to the biology of their host. In this paper, we embarked on a detailed comparison of six small rolling-circle replicating (RCR) plasmids originating from two major B. thuringiensis strains. The complete nucleotide sequences of plasmid pGI1, pGI2, pGI3, pTX14-1, pTX14-2, and pTX14-3 have been obtained and compared. Replication functions, comprising, for each plasmid, the gene encoding the Rep-protein, double-strand origin of replication (dso), single-strand origin of replication (sso), have been identified and analyzed. Two new families, or homology groups, of RCR plasmids originated from the studies of these plasmids (Group VI based on pGI3 and Group VII based on pTX14-3). On five of the six plasmids, loci involved in conjugative mobilization (Mob-genes and origin of transfer (oriT)) were identified. Plasmids pTX14-1, pTX14-2, and pTX14-3 each harbor an ORF encoding a polypeptide containing a central domain with repetitive elements similar to eukaryotic collagen (Gly-X-Y triplets). These genes were termed bcol for Bacillus-collagen-like genes. 相似文献
83.
84.
Overeem S Kok SW Lammers GJ Vein AA Frölich M Meinders AE Roelfsema F Pijl H 《American journal of physiology. Endocrinology and metabolism》2003,284(3):E641-E647
Narcolepsy is a sleep disorder caused by impaired hypocretin (orexin) neurotransmission. Growth hormone (GH) secretion may be altered in narcolepsy for various reasons. Slow-wave sleep episodes, which are closely associated with GH-secretory events, are more randomly dispersed over 24 h in narcoleptics. Furthermore, hypocretins may inhibit pituitary GH release. We assessed the function of the somatotropic axis in narcolepsy by deconvolving 24-h (10-min sampling interval) plasma GH concentration profiles in seven hypocretin-deficient narcoleptic patients and in seven healthy controls matched for age, sex, and body weight. Both basal and pulsatile GH secretion rate and secretagogue-induced GH release were similar in patients and controls. However, narcoleptics secreted approximately 50% of their total production during the daytime, whereas controls secreted only 25% during the day. Also, the GH output pattern of narcoleptics was significantly less regular. We propose that hypocretin deficiency disrupts the circadian distribution of hypothalamic GH-releasing hormone release in narcoleptic patients to simultaneously cause daytime GH release and promote their propensity to fall asleep during the day. 相似文献
85.
van Loon LJ Schrauwen-Hinderling VB Koopman R Wagenmakers AJ Hesselink MK Schaart G Kooi ME Saris WH 《American journal of physiology. Endocrinology and metabolism》2003,285(4):E804-E811
Intramuscular triglycerides (IMTG) are assumed to form an important substrate source during prolonged endurance exercise in trained males. This study investigated the effects of endurance exercise and recovery diet on IMTG content in vastus lateralis muscle. Nine male cyclists were provided with a standardized diet for 3 days, after which they performed a 3-h exercise trial at a 55% maximum workload. Before and immediately after exercise and after 24 and 48 h of recovery, magnetic resonance spectroscopy (MRS) was performed to quantitate IMTG content. Muscle biopsies were taken after 48 h of recovery to determine IMTG content by using quantitative fluorescence microscopy. The entire procedure was performed two times; in one trial, a normal diet containing 39% energy (En%) as fat was provided (NF) and in the other a typical carbohydrate-rich athlete's diet (LF: 24 En% fat) was provided. During exercise, IMTG content decreased by 21.4 +/- 3.1%. During recovery, IMTG content increased significantly in the NF trial only, reaching preexercise levels within 48 h. In accord with MRS, fluorescence microscopy showed significantly higher IMTG content in the NF compared with the LF trial, with differences restricted to the type I muscle fibers (2.1 +/- 0.2 vs. 1.4 +/- 0.2% area lipid staining, respectively). In conclusion, IMTG content in the vastus lateralis muscle declines significantly during prolonged endurance exercise in male cyclists. When a normal diet is used, IMTG contents are subsequently repleted within 48 h of postexercise recovery. In contrast, IMTG repletion is impaired substantially when a typical, carbohydrate-rich athlete's diet is used. Data obtained by quantitative fluorescence microscopy correspond well with MRS results, implying that both are valid methods to quantify IMTG content. 相似文献
86.
87.
Loss of HR6B ubiquitin-conjugating activity results in damaged synaptonemal complex structure and increased crossing-over frequency during the male meiotic prophase 总被引:7,自引:0,他引:7 下载免费PDF全文
Baarends WM Wassenaar E Hoogerbrugge JW van Cappellen G Roest HP Vreeburg J Ooms M Hoeijmakers JH Grootegoed JA 《Molecular and cellular biology》2003,23(4):1151-1162
The ubiquitin-conjugating enzymes HR6A and HR6B are the two mammalian homologs of Saccharomyces cerevisiae RAD6. In yeast, RAD6 plays an important role in postreplication DNA repair and in sporulation. HR6B knockout mice are viable, but spermatogenesis is markedly affected during postmeiotic steps, leading to male infertility. In the present study, increased apoptosis of HR6B knockout primary spermatocytes was detected during the first wave of spermatogenesis, indicating that HR6B performs a primary role during the meiotic prophase. Detailed analysis of HR6B knockout pachytene nuclei showed major changes in the synaptonemal complexes. These complexes were found to be longer. In addition, we often found depletion of synaptonemal complex proteins from near telomeric regions in the HR6B knockout pachytene nuclei. Finally, we detected an increased number of foci containing the mismatch DNA repair protein MLH1 in these nuclei, reflecting a remarkable and consistent increase (20 to 25%) in crossing-over frequency. The present findings reveal a specific requirement for the ubiquitin-conjugating activity of HR6B in relation to dynamic aspects of the synaptonemal complex and meiotic recombination in spermatocytes. 相似文献
88.
The N and C termini of the splice variants of the human mitogen-activated protein kinase-interacting kinase Mnk2 determine activity and localization 下载免费PDF全文
Scheper GC Parra JL Wilson M Van Kollenburg B Vertegaal AC Han ZG Proud CG 《Molecular and cellular biology》2003,23(16):5692-5705
The cap-binding eukaryotic initiation factor eIF4E is phosphorylated by the mitogen-activated protein (MAP) kinase-interacting kinases (Mnk's). Three forms of the Mnk's exist in human cells: Mnk1, Mnk2a, and Mnk2b. These last two are derived from the same gene by alternative splicing and differ only at their C termini. While Mnk2a contains a MAP kinase-binding site in this region, Mnk2b lacks such a sequence and is much less readily activated by MAP kinases in vitro. Expression of Mnk2b in mammalian cells leads to increased phosphorylation of eIF4E, showing that it acts as an eIF4E kinase in vivo. While Mnk2a is cytoplasmic, a substantial amount of Mnk2b is found in the nucleus. Both enzymes contain a stretch of basic residues in their N termini that plays a role in binding to eIF4G and functions as a nuclear localization signal. Binding of eIF4G or nuclear import appears to be regulated by the C terminus of Mnk2a. Furthermore, the MAP kinase-binding site of Mnk2a regulates nuclear entry. Within the nucleus, Mnk2b and certain variants of Mnk2a that are present in the nucleus colocalize with the promyelocytic leukemia protein PML, which also binds to eIF4E. 相似文献
89.
Butler M Quelhas D Critchley AJ Carchon H Hebestreit HF Hibbert RG Vilarinho L Teles E Matthijs G Schollen E Argibay P Harvey DJ Dwek RA Jaeken J Rudd PM 《Glycobiology》2003,13(9):601-622
The fundamental importance of correct protein glycosylation is abundantly clear in a group of diseases known as congenital disorders of glycosylation (CDGs). In these diseases, many biological functions are compromised, giving rise to a wide range of severe clinical conditions. By performing detailed analyses of the total serum glycoproteins as well as isolated transferrin and IgG, we have directly correlated aberrant glycosylation with a faulty glycosylation processing step. In one patient the complete absence of complex type sugars was consistent with ablation of GlcNAcTase II activity. In another CDG type II patient, the identification of specific hybrid sugars suggested that the defective processing step was cell type-specific and involved the mannosidase III pathway. In each case, complementary serum proteome analyses revealed significant changes in some 31 glycoproteins, including components of the complement system. This biochemical approach to charting diseases that involve alterations in glycan processing provides a rapid indicator of the nature, severity, and cell type specificity of the suboptimal glycan processing steps; allows links to genetic mutations; indicates the expression levels of proteins; and gives insight into the pathways affected in the disease process. 相似文献
90.
Luther Hans Peter Podlowski Svenia Schulze Wolfgang Morwinski Rosemarie Buchwalow Igor Baumann Gert Luther Hans Peter 《Molecular and cellular biochemistry》2001,224(1-2):69-79
Three 1AR subtypes have been cloned so far and are designated as 1a, 1b, and 1d. Organspecific distribution pattern and subtype-specific effects are known but not fully understood. To address a cell-type specific expression pattern in the heart we investigated expression pattern of 1AR subtypes on RNA and proteinlevel in heart tissue, cultured cardiomyocytes and nonmyocytes of the rat. Each 1ARsubtype mRNA was present in neonatal and adult rat heart culture but the relative distribution pattern was significantly different. While the 1aAR subtype is preferentially expressed in adult cardiomyocytes, the 1bAR subtype was preferentially expressed in the nonmyocyte cell fraction. The RTPCR results were confirmed by Westernblotting (1b) and immunocytochemical studies. Incubation with an 1agonist (phenylephrine) for 72 h led to a significant reduction of the 1bAR in neonatal heart cell culture on both mRNA and protein level. In contrast, incubation with an 1antagonist (prazosin) induced a 1.6 fold upregulation of the 1aAR mRNA without significant effects on radioligand binding and functional assay. The results indicate a distribution pattern of the 1AR subtype which is specific for cell type and ontogeny of the rat heart and may be regulated by adrenergic agents. 相似文献