全文获取类型
收费全文 | 2589篇 |
免费 | 205篇 |
出版年
2023年 | 11篇 |
2022年 | 16篇 |
2021年 | 45篇 |
2020年 | 26篇 |
2019年 | 28篇 |
2018年 | 35篇 |
2017年 | 40篇 |
2016年 | 45篇 |
2015年 | 99篇 |
2014年 | 111篇 |
2013年 | 137篇 |
2012年 | 187篇 |
2011年 | 173篇 |
2010年 | 113篇 |
2009年 | 128篇 |
2008年 | 144篇 |
2007年 | 158篇 |
2006年 | 142篇 |
2005年 | 128篇 |
2004年 | 123篇 |
2003年 | 122篇 |
2002年 | 96篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 16篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 9篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 25篇 |
1982年 | 28篇 |
1981年 | 17篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1974年 | 16篇 |
1973年 | 13篇 |
1972年 | 14篇 |
1971年 | 9篇 |
1968年 | 11篇 |
排序方式: 共有2794条查询结果,搜索用时 15 毫秒
31.
Mapping of genes on the linear chromosome of the bacterium Borrelia burgdorferi: Possible locations for its origin of replication 总被引:13,自引:0,他引:13
Iain G. Old Jane MacDougall Isabelle Saint Girons Barrie E. Davidson 《FEMS microbiology letters》1992,99(2-3):245-250
Molecular clones of Borrelia burgdorferi, aetiologic agent of Lyme borreliosis, were isolated and analysed by DNA sequence determination. This procedure yielded B. burgdorferi homologues of gidA, gyrB, gyrA, ftsA and ftsZ. The genes were located on the physical map of the B. burgdorferi linear chromosome. Also mapped were the genes fla and p60 while dnaA was mapped using a heterologous probe. gyrA and gyrB were found to be in tandem and were mapped, along with dnaA at the centre of the chromosome. gidA was located close to the left hand extremity of the chromosome. Because gyrB, dnaA and gidA are normally located within 50 kb of the origin of replication (oriC), we propose two possible sites for oriC in the B. burgdorferi linear chromosome. 相似文献
32.
Evidence that nitric oxide modulates food intake in mice 总被引:5,自引:0,他引:5
Nitric oxide (NO) may be an intercellular modulator within the central nervous system. L-arginine, which results in NO synthesis, increased food intake in mice while the inhibitor of NO synthesis, L-NG-nitro arginine (L-NO Arg) inhibited food intake in food deprived mice. L-arginine, but not D-arginine, partially reversed the inhibitory effect of L-NO Arg on food intake. These findings suggest the possibility that NO may be a physiological modulator of food intake and that the possibility of exploring the utility of L-NO arg in the treatment of obesity should be explored. 相似文献
33.
Paul W. Mamula Debra J. Morley Steven H. Larsen Robert C. Karn 《Biochemical genetics》1988,26(1-2):165-175
Human proline-rich proteins (PRPs) are polymorphic, homologous in sequence, and linked in a cluster called the human salivary protein complex (SPC). Recently this complex was localized to human chromosome band 12p13.2 (Mamulaet al., Cytogenet. Cell Genet. 39:279, 1985). We have isolated a PRP cDNA, EO27, from a human parotid gland library, identified it by DNA sequencing, and used it to study the molecular and cellular biology of PRP production. Cell-free translation and mRNA characterization with EO27 indicate that the numerous PRPs seen in saliva are produced from relatively few, large precursors, probably by posttranslational cleavage. This supports an hypothesis originally proposed by Friedman and Karn in 1977 (Am. J. Hum. Genet. 29:44A;Biochem. Genet. 15:549) and later supported by biochemical studies (Karnet al., Biochem Genet. 17:1061, 1979) and molecular studies (Mamulaet al., Fed. Proc. 43:1522, 1984; Maedaet al., J. Biol. Chem. 260:1123, 1985). EO27 was also used in this study to localize PRP mRNA production to the acinar cells of the parotid gland byin situ hybridization. 相似文献
34.
Delayed DNA methylation is an integral feature of DNA replication in mammalian cells 总被引:2,自引:0,他引:2
D M Woodcock D L Simmons P J Crowther I A Cooper K J Trainor A A Morley 《Experimental cell research》1986,166(1):103-112
In the majority of sites of methylation in the DNA of mammalian cells, the symmetry of methylation is restored within a few minutes of the passage of a replication fork. However, it has been shown that daughter strand methylation in immortalised cell lines is delayed in a substantial minority of sites for up to several hours after replication. We report here the results of two new approaches to the determination of the functional significance of delayed DNA methylation in mammalian cells. Firstly, we demonstrate that normal, nontransformed cells (human peripheral lymphocytes in short-term primary culture) have comparable proportions of delayed DNA methylation to many immortalised cell lines, showing that delayed DNA methylation is not just a secondary consequence of abnormally high methionine requirements commonly observed in transformed cells and that delayed DNA methylation would be unlikely not to occur in vivo. Secondly, we have used 5-aza-2'-deoxycytidine (5azadCyd) to derive subclones of cells from the Chinese hamster ovary cell line which have stably hypomethylated DNA. In three of these subclones which had lost on average one fourth of the methylation sites from their genomes, the proportion of daughter strand methylation which was delayed after replication was reduced by less than 10%. If delayed DNA methylation were site-specific, this implies that of the order of twice the number of "immediate" methylation sites than delayed methylation sites had been lost from the genomes of these hypomethylated subclones. Thus, delayed DNA methylation is an integral part of the process whereby replicating mammalian cells maintain the pattern of methylation in their genomes. These observations are discussed in relation to the significance of delayed DNA methylation for the accurate maintenance of methylation patterns in the genome and the consequent implications for the possible role of methylated deoxycytidines in mammalian gene control. 相似文献
35.
A rabbit reticulocyte factor which stimulates protein synthesis in several mammalian cell-free systems 总被引:3,自引:0,他引:3
Rabbit reticulocyte lysate post-ribosomal supernatant is shown to stimulate protein synthesis in a variety of mammalian cell-free systems, particularly the less efficient systems, such as those from mouse liver, HeLa cells and heat-shocked L cells. This stimulation reflects an increase in the rate of initiation, and is not due to the presence of globin mRNA. The stimulatory activity is unstable to purification, but some conditions favouring stability have been identified and partial purification has been achieved. It is free of eIF-2, but possesses eIF-2B activity. Its purification properties suggest that it is distinct from previously characterized initiation factors, including eIF-2/eIF-2B complex, and its possible relationship to known initiation factors is discussed. 相似文献
36.
C.B. Archer C.P. Page L. Juhlin J. Morley D.M. MacDonald 《Prostaglandins & other lipid mediators》1987,33(6)
The time-course of cutaneous inflammatory responses to LTB4 and PGE2 both alone and in combination has been studied in 10 healthy volunteers. LTB4 induced a transient wheal and flare response in some subjects, maximal at 15 minutes and succeeded by an erythematous, indurated lesion at 2–4 hours. PGE2 elicited a wheal and erythema response which resolved within 1–2 hours. Combination of LTB4 and PGE2 produced acute wheal and erythema responses which did not differ significantly from the summation of responses to the individual constituents of the mixture or from responses to a two-fold increase in the concentration of either component. Wheal and erythema responses persisted, however, with significant potentiation of responses 4 hours after injection. As both leukotrienes and prostaglandins are generated in acute allergic reactions, the effects of these mediators in combination could contribute to persisting and late-onset responses to allergen, in both the skin and lung. In particular, sustained responses to the combination of LTB4 and PGE2 might be important in the pathogenesis of inflammatory skin diseases such as psoriasis. 相似文献
37.
38.
The variation in the duration of mitosis ( t m ) with cell position in the small intestinal crypts of the adult rat has been measured by a stathmokinetic technique using vincristine. The value for the whole crypt column was 0.43 hr, or 26 min. At the bottom of the crypt t m was in excess of 1 hr, but rapidly decreased and throughout the greater part of the proliferative compartment was between 0.40 and 0.50 hr. At the top of the proliferative compartment an increase in t m was demonstrated.
If the value of 0.43 hr for the whole crypt column is correct, then one argument for postulating the formation of metabolic DNA during differentiation in the small bowel epithelium of the rat becomes invalid. Variations in tm within the crypt have been shown to increase the values of cell velocity obtained from cumulative birth rate diagrams. Finally further evidence has been presented for the existence of a slowly dividing subpopulation of cells at the base of the crypt. These cells may be important in crypt repopulation after damage with phase specific anti-tumour drugs. 相似文献
If the value of 0.43 hr for the whole crypt column is correct, then one argument for postulating the formation of metabolic DNA during differentiation in the small bowel epithelium of the rat becomes invalid. Variations in t
39.
R. Morley D. W. Eccleston C. P. Douglas W. E. J. Greville D. J. Scott J. Anderson 《BMJ (Clinical research ed.)》1970,3(5720):442-443
Three cases of xylene poisoning occurred after prolonged inhalation of paint fumes. Analysis showed that xylene comprised more than 90% of the solvent in the paint, the total solvent comprising 34% of the paint by weight. One patient was dead on admission, while the other two recovered after at least 15 hours'' loss of consciousness. Both patients had transient liver cell damage, and one temporary impairment of renal function. 相似文献
40.
Ultrasonic echoes can be detected from interfaces within the body. This principle has been applied to the examination of the cranial contents by the procedure of echoencephalography. The presence of a unilateral intracranial mass was correctly predicted by this technique in 30 out of 33 cases. The method of examination is simple, harmless, painless and rapid. Its general adoption as an aid in diagnosis of intracranial lesions, particularly in acute head injuries, is recommended. 相似文献