全文获取类型
收费全文 | 816篇 |
免费 | 118篇 |
出版年
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 29篇 |
2014年 | 30篇 |
2013年 | 51篇 |
2012年 | 40篇 |
2011年 | 34篇 |
2010年 | 34篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 21篇 |
2006年 | 38篇 |
2005年 | 27篇 |
2004年 | 25篇 |
2003年 | 22篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 18篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 17篇 |
1972年 | 8篇 |
1970年 | 5篇 |
1969年 | 6篇 |
1965年 | 6篇 |
1930年 | 5篇 |
排序方式: 共有934条查询结果,搜索用时 187 毫秒
131.
Gibbons CE Maldonado-Pérez D Shah AN Riccardi D Ward DT 《Biochimica et biophysica acta》2008,1782(3):188-195
The aminoglycoside antibiotic gentamicin elicits proximal tubular toxicity and cell death. In calcium-sensing receptor (CaR)-transfected HEK-293 (CaR-HEK) cells and CaR-expressing proximal tubule-derived opossum kidney (OK) cells, chronic gentamicin treatment elicits dose-dependent, caspase-mediated apoptotic cell death. Here we investigated whether the renal cell toxicity of the CaR agonist gentamicin could be prevented by CaR antagonism or by lithium cotreatment which may interfere with receptor-mediated signalling. Chronic treatment of OK and CaR-HEK cells with low concentrations of gentamicin elicited cell death, an effect that was ameliorated by cotreatment with the CaR negative allosteric modulator (calcilytic) NPS-89636. This calcilytic also attenuated CaR agonist-induced ERK activation in these cells. In addition, 1 mM LiCl, equivalent to its therapeutic plasma concentration, also inhibited gentamicin-induced toxicity in both cell types. This protective effect of lithium was not due to the disruption of phosphatidylinositol-mediated gentamicin uptake as the cellular entry of Texas red-conjugated gentamicin into OK and CaR-HEK cells was unchanged by lithium treatment. However, the protective effect of lithium was mimicked by glycogen synthase 3beta inhibition. Together, these data implicate CaR activation and a lithium-inhibitable signalling pathway in the induction of cell death by gentamicin in renal epithelial cells in culture. 相似文献
132.
Daniel D. Reidpath David Crawford Linda Tilgner Carl Gibbons 《Obesity (Silver Spring, Md.)》2002,10(6):526-531
Objective: To examine the relationship between body mass index (BMI) and the use of medical and preventive health services. Research Methods and Procedures: This study involved secondary analysis of weighted data from the Australian 1995 National Health Survey. The study was a population survey designed to obtain national benchmark information about a range of health‐related issues. Data were available from 17,033 men and 17,174 women, ≥20 years or age. BMI, based on self‐reported weight and height, was analyzed in relation to the use of medical services and preventive health services. Results: A positive relationship was found between BMI and medical service use, such as medication use, visits to hospital accident and emergency departments (for women only); doctor visits, visits to a hospital outpatient clinics; and visits to other health professionals (for women only). A negative relationship was found in women between BMI and preventive health services. Underweight women were found to be significantly less likely to have Papanicolaou smear tests, breast examinations, and mammograms. Discussion: This research shows that people who fall outside the healthy weight range are more likely to use a range of medical services. Given that the BMI of industrialized populations appears to be increasing, this has important ramifications for health service planning and reinforces the need for obesity prevention strategies at a population level. 相似文献
133.
Habitat requirements and local persistence of three damselfly species (odonata: coenagrionidae) 总被引:1,自引:1,他引:0
Habitat requirements and population persistence were investigated in three damselfly species, all coastal plain pond specialists: Enallagma recurvatum, E. laterale, and E. pictum. Because of geographic restriction, two are of special concern to conservation, E. recurvatum and E. laterale. We surveyed more than 70 ponds on Cape Cod, Massachusetts, and collected adult presence-absence data during the summers of 1999 and 2000. We achieved a detection rate approaching 100% for each species by visiting each pond up to three times. We looked for relationships between the presence of each damselfly species and presence of specific aquatic vegetation, the presence of the other Enallagma species, and the number of ponds within various distances of the 72 surveyed ponds. Using stepwise logistic regression, we found the following significant associations: E. recurvatum with the rush Juncus militaris; E. laterale with water lilies (Nuphar variegatum and Brasenia schreberi) the damselfly E. pictum, and the number of ponds within 2 km; and E. pictum with the water lily Nymphaea odorata, the damselfly E. laterale, and the number of ponds within 1.5 km and 2.5 km. Presence-absence data were used to calculate turnover and local extinction rates for each species between the two years. E. recurvatum's turnover and local extinction rates (33.3% and 41% respectively) were much higher than either E. laterale (9.8%, 11.5%) or E. pictum (7.7%, 10%). These results suggest that E. recurvatum occurs in a metapopulation, and that patch colonization rates might be important to local population persistence. 相似文献
134.
135.
136.
The stability of different regions of the beta heavy chain of dynein has been investigated by examining the perturbing effects of methanol, temperature, salt, and nucleotide on the pattern of tryptic digestion. In standard low-salt medium, tryptic proteolysis cleaves the beta heavy chain into three principal polypeptides of 130, 215, and 110 kDa, with the 215-kDa central peptide containing the ATP binding site as well as the vanadate and iron photocleavage sites (Mocz, G., Tang, W.-J. Y., & Gibbons, I. R. (1988) J. Cell Biol. 106, 1607-1614). The 130-kDa peptide is the most stable, and its susceptibility to trypsin appears unaffected by methanol concentrations up to 25% or temperatures up to 45 degrees C, although a 5-kDa region at one end is lost in the presence of salt (greater than 20 mM NaCl). The 215-kDa tryptic peptide contains two regions of different stability: its 123-kDa portion adjoining the 130-kDa peptide is destabilized by mild heat (37 degrees C) or by 25% methanol and becomes digested away to leave the more stable region of 92 kDa that is located toward the 110-kDa peptide and retains the V1 photocleavage site and most of the ATP binding site. The 110-kDa peptide is the least stable and at 37 degrees C, or in the presence of low concentrations of methanol or salt, it rapidly digested to small peptides. The presence of ATP during digestion of the beta heavy chain retards the formation of the 130- and 215-kDa peptides and also protects the 215-kDa peptide from further digestion at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
137.
138.
A family group of tenS. fuscicollis, housed in a greenhouse and subjected to natural variations in day length, was observed for a period of three months. All
animals ordinarily slept together in the same hutch box. The order in which the various animals emerged in the morning was
almost the precise inverse of the order in which they retired at night. Each of these orders was quite reliable and was related
in nonlinear fashion to age—the ranks of the youngest offspring being the closest to those of the parents. Time of emergence
and eating in the morning consistently preceded sunrise by about 30 min and was initiated by the oldest offspring; retiring
was much more variable and was led by the parents. 相似文献
139.
N Niccolai M P Miles W A Gibbons 《Biochemical and biophysical research communications》1979,91(1):157-163
We report mono and bi-selective excitation proton relaxation studies of internal motion of three side chaing in a peptide fragment of angiotensin of sequence Tyr1. Ile2. His3. Pro4. Phe5. The motion of this peptide does not satisfy the extreme narrowing conditions and the general approach to the interpretation of proton relaxation rates given here can be used in larger peptides and proteins. 相似文献
140.
The K88 antigen of Escherichia coli specifically adheres to the piglet intestinal cell; a solution of this antigen agglutinates guinea-pig red cells at 4 degrees C. The latter reaction was used as a model of the former, using inhibition of haemagglutination as an index of specific combination with the K88 adhesin. Inhibition was found with mucous glycoproteins and chemical modification of their heterosaccharide residues by mild acid hydrolysis, periodate oxidation or the Smith degradation procedure suggested that the terminal beta-D-galactosyl structure in a heterosaccharide sidechain of a glycoprotein might combine specifically with the K88 adhesin and inhibit haemagglutination. One serum glycoprotein (fetuin), after exposure of its subterminal beta-D-galactosyl residue, also inhibited haemagglutination, but high inhibitory activity was exhibited by some submaxillary glycoproteins in which this structure was absent or not prominent. It was concluded that in some cases inhibition of haemagglutination by glycoprotein was non-specific. No inhibition was found using glycosaminoglycans, glycogen or any simple sugar or glycoside. Sow colostrum was inhibitory but this was associated mainly with its gamma-globulin fraction. Some inhibitory activity was traced to a colostral glycopeptide fraction of low molecular weight but the smaller colostral oligosaccharides were not inhibitory; the composition of these components in sow colostrum is reported. 相似文献