全文获取类型
收费全文 | 581篇 |
免费 | 35篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 20篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 33篇 |
2014年 | 38篇 |
2013年 | 39篇 |
2012年 | 55篇 |
2011年 | 41篇 |
2010年 | 28篇 |
2009年 | 19篇 |
2008年 | 25篇 |
2007年 | 38篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 29篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有616条查询结果,搜索用时 15 毫秒
41.
42.
Separate taurine and chloride efflux pathways activated during regulatory volume decrease 总被引:6,自引:0,他引:6
Stutzin Andres; Torres Ruben; Oporto Macarena; Pacheco Patricio; Eguiguren Ana Luisa; Cid L. Pablo; Sepulveda Francisco V. 《American journal of physiology. Cell physiology》1999,277(3):C392
Organic osmolyte and halide permeability pathways activated inepithelial HeLa cells by cell swelling were studied by radiotracer efflux techniques and single-cell volume measurements. The replacement of extracellular Cl byanions that are more permeant through the volume-activated Cl channel, as indicated byelectrophysiological measurements, significantly decreasedtaurine efflux. In the presence of less-permeant anions, an increase intaurine efflux was observed. Simultaneous measurement of the125I, used as a tracer forCl, and[3H]taurine effluxshowed that the time courses for the two effluxes differed. InCl-rich medium the increasein I efflux was transient,whereas that for taurine was sustained. OsmosensitiveCl conductance, assessed bymeasuring changes in cell volume, increased rapidly after hypotonicshock. The influx of taurine was able to counteractCl conductance-dependentcell shrinkage but only ~4 min after triggering cell swelling. Thistaurine-induced effect was blocked by DIDS. Differences in anionsensitivity, the time course of activation, and sensitivity to DIDSsuggest that the main cell swelling-activated permeability pathways fortaurine and Cl are separate. 相似文献
43.
44.
We estimated fusion frequency with respect to coancestry in the bryozoan Celleporella hyalina, whose briefly planktonic sexually produced larvae settle on algal substrata and proceed to form encrusting colonies by iterative budding. Frequency of fusion between paired colonies growing on an artificial substratum was positively correlated with coefficient of relatedness, with allorecognition ability increasing during the early stages of colonial growth after larval settlement. Parents repressed the growth of F1 progeny with which they had fused. The results are concordant with the Feldgarden-Yund model of selection for self-recognition, which regards fusion with kin as an inevitable source of error whose cost diminishes with increasing relatedness. Contrary to fusion compatibility, gametic compatibility is negatively correlated with coancestry, indicating a need for further research on the possibility of common or linked genetic control that has opposite effect at somatic and gametic levels. 相似文献
45.
Revisiting the mouse mitochondrial DNA sequence 总被引:9,自引:1,他引:8
Bayona-Bafaluy MP Acín-Pérez R Mullikin JC Park JS Moreno-Loshuertos R Hu P Pérez-Martos A Fernández-Silva P Bai Y Enríquez JA 《Nucleic acids research》2003,31(18):5349-5355
The existence of reliable mtDNA reference sequences for each species is of great relevance in a variety of fields, from phylogenetic and population genetics studies to pathogenetic determination of mtDNA variants in humans or in animal models of mtDNA-linked diseases. We present compelling evidence for the existence of sequencing errors on the current mouse mtDNA reference sequence. This includes the deletion of a full codon in two genes, the substitution of one amino acid on five occasions and also the involvement of tRNA and rRNA genes. The conclusions are supported by: (i) the re-sequencing of the original cell line used by Bibb and Clayton, the LA9 cell line, (ii) the sequencing of a second L-derivative clone (L929), and (iii) the comparison with 12 other mtDNA sequences from live mice, 10 of them maternally related with the mouse from which the L cells were generated. Two of the latest sequences are reported for the first time in this study (Balb/cJ and C57BL/6J). In addition, we found that both the LA9 and L929 mtDNAs also contain private clone polymorphic variants that, at least in the case of L929, promote functional impairment of the oxidative phosphorylation system. Conse quently, the mtDNA of the strain used for the mouse genome project (C57BL/6J) is proposed as the new standard for the mouse mtDNA sequence. 相似文献
46.
47.
Diosque P Barnabé C Padilla AM Marco JD Cardozo RM Cimino RO Nasser JR Tibayrenc M Basombrío MA 《International journal for parasitology》2003,33(10):997-1003
A set of 65 Trypanosoma cruzi stocks from dogs, opossums, insect vectors and humans was isolated in a geographically restricted endemic area for Chagas' disease in Argentina and was analysed by multilocus enzyme electrophoresis for 15 loci. The results show that at least five multilocus genotypes (clonets) circulate in the study area, one belonging to T. cruzi IIe, one to T. cruzi IId and three clonets belonging to T. cruzi I; and they confirm the presence of these lineages in the country. The three clonets attributed to T. cruzi I were identical to each other for all loci except for Sod-2, where three different patterns were identified. These patterns suggest the presence of two homozygous genotypes and one heterozygous genotype. Our results also suggest association of clonet IIe with dogs, clonet IId with humans and the three T. cruzi I clonets with Didelphis albiventris. On the other hand, there was no significant association between Triatoma infestans and any particular clonet circulating in the area. These findings are consistent with the hypothesis of natural selection, from mixed populations of T. cruzi in vectors, toward more restricted populations in mammals. The epidemiological implications of the possible selection of different clonets by different mammal hosts and the significance of two homozygous genotypes and one heterozygous genotype for the Sod-2 locus are discussed. 相似文献
48.
Cabrera R Guixé V Alfaro J Rodríguez PH Babul J 《Archives of biochemistry and biophysics》2002,402(2):289-295
An isoform (rhesus UGT1A01) orthologus to the human UGT1A1 was cloned and sequenced from female rhesus monkey liver cDNA using primers designed from the human nucleotide sequences. Open reading frame analysis of the PCR-generated product encodes a 533-amino acid protein with a proposed 27-residue signal peptide. Nucleotide sequence comparison of rhesus UGT1A01 to other rhesus UGT1A isoforms detected a single-transition mutation at nucleotide 1520 (T-->C), resulting in a neutral F to S substitution at position 507. Rhesus UGT1A01 was greater than 99 and 95% identical to cynomolgus UGT1A01 and human UGT1A1, respectively. The rhesus UGT1A01 was expressed in HK-293 cells for functional analysis. Catalytic activity of UGT1A01 was determined with 7-hydroxy-4-(trifluoromethyl)-coumarin and more specific human UGT1A1 substrates (1-naphthol, beta-estradiol, 17 alpha-ethinylestradiol, and bilirubin). Expression of UGT1A01 protein was also detected by a Western blot utilizing a polyclonal antibody developed against the human UGT1A family. 相似文献
49.
Immunolocalization of an FGF-binding protein reveals a widespread expression pattern during different stages of mouse embryo development 总被引:5,自引:1,他引:4
Fibroblast growth factors (FGFs) play important roles during fetal and embryonic development. FGF-2 (basic FGF, bFGF) is widely expressed in the embryo and has been linked to tissue growth and remodeling. However, it is tightly bound to heparin sulfate proteoglycans of the extracellular matrix which quenches its biological activity. We showed previously that a secreted FGF-binding protein (FGF-BP) can mobilize and activate FGF-2 from the extracellular matrix. While considerable data exist on the expression and pivotal role of FGF-BP in tumor growth, less is known about FGF-BP during embryonic development. In this immunohistochemical study in mice, we show FGF-BP protein expression in a broad spectrum of tissues at various stages between day 8 and day 16 of embryonal development, and compare FGF-BP and FGF-2 immunolocalization. FGF-BP is detected in the digestive system, thymus, skin, hair follicles, dental germ, respiratory tract, various glandular tissues, kidney, liver, and certain areas of the CNS, with immunoreactivity being mainly confined to cells of primitive epithelia. The putative significance of these findings with regard to mobilization of FGF-2 or other molecules is discussed. From the locally confined, time-dependent, and apparently tightly regulated FGF-BP expression we propose that FGF-BP may play an important role in embryonic development. 相似文献
50.
p53 codon 72 polymorphism and risk of cervical cancer 总被引:7,自引:0,他引:7
Ojeda JM Ampuero S Rojas P Prado R Allende JE Barton SA Chakraborty R Rothhammer F 《Biological research》2003,36(2):279-283
Storey et al. (1998) implicated the proline/argine polymorphism of the codon 72 of the tumor-suppressor gene p53 in the development of cervical cancer (CC) with the observation that the p53 protein is more efficiently inactivated by the E6 oncoprotein of human papillomavirus in p53 arginine as compared with its proline isoform. These authors further noted that in the United Kingdom, individuals homozygous for the arginine allele were several times more susceptible to HPV-associated tumorigenesis that proline/arginine heterozygotes. Subsequent studies in different countries failed to unanimously confirm this association. Motivated by the high incidence of CC in Chile, we undertook a case control study obtaining the following frequencies for genotypes PP, AP and AA in 60 ICC cases and 53 carefully selected controls: 0.067, 0.250, 0.683 and 0.075, 0.453, 0.472 respectively. A significant difference (X2 = 3.19 p < 0.02) and an odds ratio of 2.62 supported Storey et al (1998)'s results. In addition, rejecting previous hypotheses about the world distribution of the p53 codon 72 polymorphism, we conclude that this distribution most likely represents ancient human dispersal routes. Several methodological and biological explanations for the results obtained in previous negative association studies are briefly discussed. 相似文献