全文获取类型
收费全文 | 703篇 |
免费 | 54篇 |
出版年
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 40篇 |
2014年 | 39篇 |
2013年 | 44篇 |
2012年 | 57篇 |
2011年 | 53篇 |
2010年 | 34篇 |
2009年 | 29篇 |
2008年 | 49篇 |
2007年 | 47篇 |
2006年 | 35篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 22篇 |
2001年 | 20篇 |
2000年 | 3篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有757条查询结果,搜索用时 78 毫秒
1.
Owing to the exceptional intracellular distribution and the heterogeneous expression pattern during transformation and metastasis
in various tumors, the EF-hand calcium-binding protein S100A2 attracts increasing attention. Unlike the majority of S100 proteins,
S100A2 expression is downregulated in many cancers and the loss in nuclear expression has been associated with poor prognosis.
On the other hand, S100A2 is upregulated in some cancers. This mini review highlights the general characteristics of S100A2
and discusses recent findings on its putative functional implication as a suppressor or promoter in cancerogenesis. 相似文献
2.
3.
S M Garn A R Frisancho A K Poznanski J Schweitzer M B McCann 《American journal of physical anthropology》1971,34(3):431-433
Fusion of the centers of the triquetral and lunate (the os lunato-triquetrum) was observed in 1.6% of 7,543 subjects primarily of African origin as compared with 0.1% of 11,663 persons of European origin. The fusion was twice as common in females as in males, multifactorial inheritance was suggested in the lineages studied, and a possible selective disadvantage was postulated after comparison with West African fusion frequencies. 相似文献
4.
S Gilgenkrantz J P Fryns P Droulle M Schweitzer B Chadefaux M Prieur 《Journal de génétique humaine》1987,35(1):51-61
In two cases, first interpreted as mosaic tetrasomy 21, the R banding and the gene dosage studies lead us to conclude to a mosaic tetrasomy 12 p. In Pallister mosaic syndrome and in Teschler-Nicola/Killian syndrome, the very similar clinical signs and the identical abnormal chromosome, missing in leucocytes, led us to conclude that Pallister and Teschler-Nicola/Killian syndrome, as well as mosaic tetrasomy 21 are one and the same syndrome tetrasomy 12 p. This tissue limited mosaic is probably more frequent than it is assumed. Prenatal diagnosis can be made since the supernumerary chromosome is found in amniocytes. The distinctive tissue distribution is probably a selective process due to cellular differentiation gene, CD9 (or Alb 6) located to 12 p. 相似文献
5.
6.
We have used slice preparation from newborn rats to study the development of the nucleus tractus solitarius neuronal network and brain intracellular phosphorus metabolites. As shown previously on adults, the newborn preparation retains local excitatory and inhibitory synaptic connections and enables study of intrinsic electrical properties in the nucleus tractus solitarius. Electrophysiological investigation of inhibitory synaptic transmission demonstrated a maturational step at days 4-6 after birth. Nuclear magnetic resonance spectroscopy of brain slices revealed a metabolic maturation between postnatal days 11 and 17. Results emphasize the differential maturation steps during the postnatal development of rat central nervous system. Possibly, Sudden Infant Death Syndrome may result from the abnormal timing in the occurrence of these steps. 相似文献
7.
Karin Lindström Albert E. G. Kr. Von Dem Borne Michael E. Breimer Bertil Cedergren Yasuto Okubo Lennart Rydberg Susann Teneberg Bo E. Samuelsson 《Glycoconjugate journal》1992,9(6):325-329
A 12-week-old fetus and one 17-week-old fetus + placenta were obtained after spontaneous abortions from two women of blood group p. The 17-week-old fetus was dissected into intestine, liver, brain and residual tissue. Nonacid glycosphingolipid fractions were prepared from the tissues. Glycolipid characterization was carried out using thin layer chromatography immunostained with monoclonal antibodies and bacteria and by1H NMR spectroscopy and mass spectrometry. In the placental fraction substantial amounts of globotetraosylceramide (P-antigen) and globotriaosylceramide (Pk-antigen) were identified. In contrast, the fetuses contained only trace amounts of these structures, as revealed by immunostaining. These results indicate that the primary target for the antibodies of the anti-Tja serum is the placenta tissue, resulting in termination of the pregnancy. 相似文献
8.
Increasing specific leaf weight (SLW) may improve leaf apparent photosynthesis (AP) in soybean [Glycine max (L.) Merr.] but screening for SLW and AP is laborious. The Objectives of this study were (i) to determine the time course of SLW and chlorophyll concentration in experimental lines selected for differences in SLW and (ii) to evaluate the potential use of the Minolta 502 SPAD meter as a rapid estimator of SLW, AP and chlorophyll concentration in leaves of soybean. In 1991 and 1992, sixteen experimental lines representing extremes in SLW were grown at Urbana, IL, and West Lafayette, IN, with three replications at each location. SPAD values, SLW and AP were measured at the R2 (full flower), R4 (full pod) and R5 (beginning seed) growth stages. In 1992 SLW, SPAD values and chlorophyll concentration were measured weekly. Seasonal patterns of SPAD values, SLW, and chlorophyll concentration were very similar through R5. After R5, SLW continued to increase but SPAD values and chlorophyll concentration declined. SPAD values and SLW were highly correlated at the R2, R4 and R5 stages at both locations and in both years. Environmental conditions during this research were not suitable for maximum AP expression, which is likely why AP and SPAD values were correlated only at the R4 growth stage at Urbana in 1992. SPAD measurements were consistent across diverse environments and effectively separated the high SLW lines from the low SLW lines. Measuring with the Minolta 502 SPAD meter is rapid, simple and non-destructive and could be an alternative method for direct selection for SLW.Abbreviations AP-
leaf apparent photosynthesis
- CV-
coefficient of variation
- Rug-
leaf rugosity
- SLW-
specific leaf weight
- SPAD-L-
SPAD value of the most recently expanded terminal leaflet
- SPAD-P-
SPAD value of leaflet used to measure AP
- SPAD-S-
SPAD value of leaflets used to measure SLW
- SPAD-U-
SPAD value of the terminal leaflet one node above the most recently expanded terminal leaflet
The US Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged 相似文献
9.
Susann Teneberg Timothy R. Hirst Jonas Ångström Karl-Anders Karlsson 《Glycoconjugate journal》1994,11(6):533-540
The binding specificities of cholera toxin andEscherichia coli heat-labile enterotoxin were investigated by binding of125I-labelled toxins to reference glycosphingolipids separated on thin-layer chromatograms and coated in microtitre wells. The binding of cholera toxin was restricted to the GM1 ganglioside. The heat-labile toxin showed the highest affinity for GM1 but also bound, though less strongly, to the GM2, GD2 and GD1b gangliosides and to the non-acid glycosphingolipids gangliotetraosylceramide and lactoneotetraosylceramide. The infant rabbit small intestine, a model system for diarrhoea induced by the toxins, was shown to contain two receptor-active glycosphingolipids for the heat-labile toxin, GM1 ganglioside and lactoneotetraosylceramide, whereas only the GM1 ganglioside was receptor-active for cholera toxin. Preliminary evidence was obtained, indicating that epithelial cells of human small intestine also contain lactoneotetraosylceramide and similar sequences. By computer-based molecular modelling, lactoneotetraosylceramide was docked into the active site of the heat-labile toxin, using the known crystal structure of the toxin in complex with lactose. Interactions which may explain the relatively high toxin affinity for this receptor were found.Abbreviations CT
cholera toxin
- CT-B
B-subunits of cholera toxin
- LT
Escherichia coli heat-labile enterotoxin
- hLT
humanEscherichia coli heat-labile enterotoxin
- pLT
porcineEscherichia coli heat-labile enterotoxin
- EI
electron ionization 相似文献
10.
Molecular basis of intercellular adhesion in the biofilm-forming Staphylococcus epidermidis 总被引:13,自引:3,他引:10
Christine Heilmann Oliver Schweitzer Christiane Gerke Nongnuch Vanittanakom Dietrich Mack Friedrich Götz 《Molecular microbiology》1996,20(5):1083-1091
The Staphylococcus epidermidis genes icaABC are involved in the synthesis of the polysaccharide intercellular adhesin (PIA), which is located mainly on the cell surface, as shown by immunofluorescence studies with PIA-specific antiserum. PIA was shown to be a linear β-1,6-linked glucosaminoglycan composed of at least 130 2-deoxy-2-amino-D-glucopyrano-syl residues of which 80–85% are N-acetylated, the rest being non-N-acetylated and positively charged. A transposon insertion in the icaABC gene cluster (ica, intercellular adhesion) led to the loss of several traits, such as the ability to form a biofilm on a polystyrene surface, cell aggregation, and PIA production. The mutant could be complemented by transformation with the IcaABC-carrying plasmid pCN27. Transfer of pCN27 into the heterologous host Staphylococcus carnosus led to the formation of large cell aggregates, the formation of a biofilm on a glass surface, and PIA expression. The nucleotide sequence of icaABC suggests that the three genes are organized in an operon and that they are co-transcribed from the mapped ica A promoter. Ica A contains four potential transmembrane helices, indicative of a membrane location. The deduced Ica A sequence shows similarity to those of polysaccharide-polymerizing enzymes, the most pronounced being with a Rhizobium meliloti N-acetylglucosaminyltransferase involved in lipo-chitin biosynthesis (22.5% overall identity and 37.4% overall similarity). This similarity suggests that Ica A has N-acetylglucosaminyltransferase activity in the formation 相似文献