全文获取类型
收费全文 | 132篇 |
免费 | 9篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 234 毫秒
1.
Consequences of methylation on the amino group of adenine. A proton two-dimensional NMR study of d(GGATATCC) and d(GGm6ATATCC) 总被引:7,自引:0,他引:7
E Quignard G V Fazakerley R Teoule A Guy W Guschlbauer 《European journal of biochemistry》1985,152(1):99-105
A two-dimensional 500-MHz 1H-NMR study of two oligonucleotides, d(GGATATCC) and d(GGm6ATATCC), is presented in which we have investigated the effects of adenine methylation. The two-dimensional nuclear Overhauser spectra (NOESY) show that both oligonucleotides adopt a normal right-handed B-type helix and one-dimensional nuclear Overhauser enhancement (NOE) studies demonstrate that any difference in conformation must be small. However methylation drastically slows down the helix in equilibrium coil exchange which becomes slow on a proton NMR time scale. While d(GGATATCC) fits a two-site exchange model, d(GGm6ATATCC) does not and we invoke the presence of a third species which may be an intermediate in helix formation. NMR and ultraviolet spectroscopy show that methylation destabilizes the helix, measured by the melting temperature and enthalpy of dissociation. 相似文献
2.
Female reproductive biology of the sand smelt in brackish lagoons of southern France 总被引:2,自引:0,他引:2
The breeding season of Atherina boyeri living in the brackish lagoons of Mauguio, Pérols and Méjean (Hérault, southern France) was very protracted (February-September). The peak of the reproductive effort occurred in April, May and June. Larger fishes started spawning earlier, and stopped later, than smaller ones. Batch fecundity varied from 4 to 447 oocytes and was positively related to female length and weight. Monthly mean fecundity increased at the beginning of the breeding season and decreased between June and July. Individual mean oocyte diameter ranged from 1.34 to 1.94 mm and was not related to fish length. Monthly mean oocyte size declined throughout the breeding season as water temperature rose. There was no trade-off between number and egg size. The strategy of these sand smelts seemed well adapted to ensure spawning success without endangering their survival. The highest reproductive effort period occurred in such a way that environmental conditions were suitable to the best survival and growth of hatched larvae. When breeding ceased, fishes, particularly the youngest ones, had enough time to improve their condition before overwintering. 相似文献
3.
Comparison of the conformation of an oligonucleotide containing a central G-T base pair with the non-mismatch sequence by proton NMR. 总被引:3,自引:3,他引:0 下载免费PDF全文
E Quignard G V Fazakerley G van der Marel J H van Boom W Guschlbauer 《Nucleic acids research》1987,15(8):3397-3409
We have recorded NOESY spectra of two non-selfcomplementary undecanucleotide duplexes. From the observed NOEs we do not detect any significant distortion of the helix when a G-C pair is replaced by a G-T pair and the normal interresidue connectivities can be followed through the mismatch site. We conclude that the 2D spectra of the non-exchangeable protons do not allow differentiation between a wobble or rare tautomer form for the mismatch. NOE measurements in H2O, however, clearly show that the mismatch adopts a wobble structure and give information on the hydration in the minor groove for the G-T base pair which is embedded between two A-T base pairs in the sequence. 相似文献
4.
E.?Tapia-VenegasEmail author L.?Cabrol B.?Brandhoff J.?Hamelin E.?Trably JP?Steyer G.?Ruiz-Filippi 《Applied microbiology and biotechnology》2015,99(19):8295-8308
Hydrogen is a promising alternative as an energetic carrier and its production by dark fermentation from wastewater has been recently proposed, with special attention to crude glycerol as potential substrate. In this study, two different feeding strategies were evaluated for replacing the glucose substrate by glycerol substrate: a one-step strategy (glucose was replaced abruptly by glycerol) and a step-by-step strategy (progressive decrease of glucose concentration and increase of glycerol concentration from 0 to 5 g L?1), in a continuous stirred tank reactor (12 h of hydraulic retention time (HRT), pH 5.5, 35 °C). While the one-step strategy led to biomass washout and unsuccessful H2 production, the step-by-step strategy was efficient for biomass adaptation, reaching acceptable hydrogen yields (0.4?±?0.1 molH2?mol?1 glycerol consumed) around 33 % of the theoretical yield independently of the glycerol concentration. Microbial community structure was investigated by single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) fingerprinting techniques, targeting either the total community (16S ribosomal RNA (rRNA) gene) or the functional Clostridium population involved in H2 production (hydA gene), as well as by 454 pyrosequencing of the total community. Multivariate analysis of fingerprinting and pyrosequencing results revealed the influence of the feeding strategy on the bacterial community structure and suggested the progressive structural adaptation of the community to increasing glycerol concentrations, through the emergence and selection of specific species, highly correlated to environmental parameters. Particularly, this work highlighted an interesting shift of dominant community members (putatively responsible of hydrogen production in the continuous stirred tank reactor (CSTR)) according to the gradient of glycerol proportion in the feed, from the family Veillonellaceae to the genera Prevotella and Clostridium sp., putatively responsible of hydrogen production in the CSTR. 相似文献
5.
Lindström Irene Bontell Neil Hall Kevin E Ashelford JP Dubey Jon P Boyle Johan Lindh Judith E Smith 《Genome biology》2009,10(5):R53-17
Background
Toxoplasma gondii is a zoonotic parasite of global importance. In common with many protozoan parasites it has the capacity for sexual recombination, but current evidence suggests this is rarely employed. The global population structure is dominated by a small number of clonal genotypes, which exhibit biallelic variation and limited intralineage divergence. Little is known of the genotypes present in Africa despite the importance of AIDS-associated toxoplasmosis. 相似文献6.
J Klein J Gonzalez J Duchene L Esposito JP Pradère E Neau C Delage D Calise A Ahluwalia P Carayon JB Pesquero M Bader JP Schanstra JL Bascands 《FASEB journal》2009,23(1):134-142
Renal fibrosis is the common histological feature of advanced glomerular and tubulointerstitial disease leading to end-stage renal disease (ESRD). However, specific antifibrotic therapies to slow down the evolution to ESRD are still absent. Because persistent inflammation is a key event in the development of fibrosis, we hypothesized that the proinflammatory kinin B1 receptor (B1R) could be such a new target. Here we show that, in the unilateral ureteral obstruction model of renal fibrosis, the B1R is overexpressed and that delayed treatment with an orally active nonpeptide B1R antagonist blocks macrophage infiltration, leading to a reversal of the level of renal fibrosis. In vivo bone marrow transplantation studies as well as in vitro studies on renal cells show that part of this antifibrotic mechanism of B1R blockade involves a direct effect on resident renal cells by inhibiting chemokine CCL2 and CCL7 expression. These findings suggest that blocking the B1R is a promising antifibrotic therapy. 相似文献
7.
Cassava is infected by numerous geminiviruses in Africa and India that cause devastating losses to poor farmers. We here describe the molecular diversity of seven representative cassava mosaic geminiviruses (CMGs) infecting cassava from multiple locations in Tanzania. We report for the first time the presence of two isolates in East Africa: (EACMCV-[TZ1] and EACMCV-[TZ7]) of the species East African cassava mosaic Cameroon virus, originally described in West Africa. The complete nucleotide sequence of EACMCV-[TZ1] DNA-A and DNA-B components shared a high overall sequence identity to EACMCV-[CM] components (92% and 84%). The EACMCV-[TZ1] and -[TZ7] genomic components have recombinations in the same genome regions reported in EACMCV-[CM], but they also have additional recombinations in both components. Evidence from sequence analysis suggests that the two strains have the same ancient origin and are not recent introductions. EACMCV-[TZ1] occurred widely in the southern part of the country. Four other CMG isolates were identified: two were close to the EACMV-Kenya strain (named EACMV-[KE/TZT] and EACMV-[KE/TZM] with 96% sequence identity); one isolate, TZ10, had 98% homology to EACMV-UG2Svr and was named EACMV-UG2 [TZ10]; and finally one isolate was 95% identical to EACMV-[TZ] and named EACMV-[TZ/YV]. One isolate of African cassava mosaic virus with 97% sequence identity with other isolates of ACMV was named ACMV-[TZ]. It represents the first ACMV isolate from Tanzania to be sequenced. The molecular variability of CMGs was also evaluated using partial B component nucleotide sequences of 13 EACMV isolates from Tanzania. Using the sequences of all CMGs currently available, we have shown the presence of a number of putative recombination fragments that are more prominent in all components of EACMV than in ACMV. This new knowledge about the molecular CMG diversity in East Africa, and in Tanzania in particular, has led us to hypothesize about the probable importance of this part of Africa as a source of diversity and evolutionary change both during the early stages of the relationship between CMGs and cassava and in more recent times. The existence of multiple CMG isolates with high DNA genome diversity in Tanzania and the molecular forces behind this diversity pose a threat to cassava production throughout the African continent. 相似文献
8.
9.
Ducret T El Arrouchi J Courtois A Quignard JF Marthan R Savineau JP 《Cell calcium》2010,48(5):251-259
Stretch-activated channels (SACs) act as membrane mechanotransducers since they convert physical forces into biological signals and hence into a cell response. Pulmonary arterial smooth muscle cells (PASMCs) are continuously exposed to mechanical stimulations e.g., compression and stretch, that are enhanced under conditions of pulmonary arterial hypertension (PAH). Using the patch-clamp technique (cell-attached configuration) in PASMCs, we showed that applying graded negative pressures (from 0 to -60 mmHg) to the back end of the patch pipette increases occurrence and activity of SACs. The current-voltage relationship (from -80 to +40 mV) was almost linear with a reversal potential of 1 mV and a slope conductance of 34 pS. SACs were inhibited in the presence of GsMTx-4, a specific SACs blocker. Using microspectrofluorimetry (indo-1), we found that hypotonic-induced cell swelling increases intracellular Ca(2+) concentration ([Ca(2+)](i)). This [Ca(2+)](i) increase was markedly inhibited in the absence of external Ca(2+) or in the presence of the following blockers of SACs: gadolinium, streptomycin, and GsMTx-4. Interestingly, in chronically hypoxic rats, an animal model of PAH, SACs were more active and hypotonic-induced calcium response in PASMCs was significantly higher (nearly a two-fold increase). Moreover, unlike in normoxic rats, intrapulmonary artery rings from hypoxic rats mounted in a Mulvany myograph, exhibited a myogenic tone sensitive to SAC blockers. In conclusion, this work demonstrates that SACs in rat PASMCs can be activated by membrane stretch as well as hypotonic stimulation and are responsible for [Ca(2+)](i) increase. The link between SACs activation-induced calcium response and myogenic tone in chronically hypoxic rats suggests that SACs are an important element for the increased pulmonary vascular tone in PAH and that they may represent a molecular target for PAH treatment. 相似文献
10.
A Plonquet S Bastuji-Garin F Tahmasebi C Brisacier K Ledudal JP Farcet E Paillaud 《Immunity & ageing : I & A》2011,8(1):1-7