全文获取类型
收费全文 | 1828篇 |
免费 | 192篇 |
国内免费 | 1篇 |
出版年
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 35篇 |
2017年 | 17篇 |
2016年 | 36篇 |
2015年 | 56篇 |
2014年 | 81篇 |
2013年 | 75篇 |
2012年 | 91篇 |
2011年 | 99篇 |
2010年 | 72篇 |
2009年 | 45篇 |
2008年 | 103篇 |
2007年 | 64篇 |
2006年 | 74篇 |
2005年 | 66篇 |
2004年 | 77篇 |
2003年 | 65篇 |
2002年 | 54篇 |
2001年 | 56篇 |
2000年 | 54篇 |
1999年 | 47篇 |
1998年 | 35篇 |
1997年 | 20篇 |
1996年 | 23篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 31篇 |
1990年 | 28篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 20篇 |
1980年 | 13篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 15篇 |
1972年 | 17篇 |
1971年 | 15篇 |
1970年 | 14篇 |
1969年 | 16篇 |
1968年 | 12篇 |
排序方式: 共有2021条查询结果,搜索用时 39 毫秒
31.
Masato Tawata Ryoji Kobayashi Myles L. Mace Thor B. Nielsen James B. Field 《Biochemical and biophysical research communications》1983,111(2):415-423
An actin polymerization stimulator was purified from bovine thyroid plasma membranes by DNase I affinity column chromatography. Although the molecular weight of the protein was about 42,000 (42K) by sodium dodecyl sulfate polyacrylamide gel electrophoresis, it did not comigrate with actin. In the presence of 30 mM KCl, the 42K protein facilitated formation of actin filaments when analyzed by a centrifugation method, accelerated the initial phase of actin polymerization as measured in an Ostwald viscometer and increased the length of filaments as shown by electron microscopy. The 42K protein also accelerated the initial phase of actin polymerization in the presence of 100 mM KCl and 2 mM MgCl2 but did not affect the final viscosity. The effect of the 42K protein was diminished by 5 uM cytochalasin B or 1 uM cytochalasin D. This 42K protein may anchor actin filaments onto the thyroid plasma membrane. 相似文献
32.
33.
Jane E. Langridge-Smith Joseph H. Sellin Michael Field 《The Journal of membrane biology》1983,72(1-2):131-139
Summary In intact ileal mucosa, uptake of SO4 across the brush border membrane requires the presence of Na and is saturable, withK1/2=1.3mm at 140mm Na (P.L. Smith, S.A. Orellana & M. Field, 1981.J. Membrane Biol.
63:199–206). The present study examines the substrate specificities and transport stoichiometry of the Na-dependent SO4 uptake process. The effects of variations in medium anion and cation composition on lumen-to-epithelium influx of SO4 (J
me
SO4
) were determined under short-circuit conditions.J
me
SO4
is inhibited by thiosulfate, but not by phosphate, methylsulfate, vanadate or taurocholate. Cl is weakly inhibitory. Uptake of SO4 is poorly supported by Li, and is unaffected by K, indicating a specific dependence on Na. At low SO4 concentration (0.22mm),J
me
SO4
is a hyperbolic function of medium Na concentration; the corresponding Hill plot is linear with a slope of 1.0, suggesting a transport stoichiometry of 1 Na: 1 SO4. At high SO4 concentration (6.7mm), the Na-dependent SO4 velocity curve is sigmoidal and yields a Hill plot which is again linear but has a slope of 1.56, suggesting transport of more than 1 Na per SO4. SO4 uptake in presence of Na exhibits a dependence on medium pH. At 0.22mm SO4 and 140mm Na,J
me
SO4
was doubled by lowering pH from 7.4 to 6.8. However, at 6.7mm SO4 and 140mm Na, changing pH had no effect onJ
me
SO4
over the range 6.8 to 8.5. The pH dependence ofJ
me
SO4
at 6.7mm SO4 was restored when medium Na was lowered to 3mm, suggesting that pH sensitivity is a function of the concentration of preformed NaSO
4
–
ion pair. The results suggest that SO4 influx across the ileal brush border occurs by electroneutral Na+/NaSO
4
–
or Na+/H+/SO
4
2–
cotransport, the former being favored by high concentrations of Na and SO4. 相似文献
34.
Identification and purification of calcium ion dependent modulators of actin polymerization from bovine thyroid 总被引:2,自引:0,他引:2
We describe the purification of Ca2+-dependent actin modulator proteins from bovine thyroid using DNase I affinity chromatography and diethylaminoethylcellulose chromatography. The 40K actin modulator has been purified to 98% homogeneity. It is a single polypeptide chain with a molecular weight of approximately 40 000 and an isoelectric point of 8.1. Its amino acid composition is different from previously described actin-associated proteins and thyroid actin. On the basis of the centrifugation assay and the DNase I inhibition assay, the actin complexed with the 40K protein is G-actin in its conformation rather than F-actin oligomers. Substoichiometric concentrations of the 40K protein rapidly inhibit actin polymerization in the presence of physiological concentrations of Ca2+ and Mg2+. An 80K actin modulator also has been purified to 98% homogeneity. It is a single polypeptide chain with a molecular weight of approximately 80 000 and an isoelectric point of 6.35-7.0. Its amino acid composition is different from those of villin, gelsolin, and leukocyte actin polymerization inhibitor. On the basis of the DNase inhibition assay and the centrifugation assay, the nonprecipitable actin associated with the 80K protein was F-actin in its conformation. The 80K protein acts very efficiently as a Ca2+-dependent nucleator for actin assembly and reduces its viscosity. In addition to the 40K and 80K actin modulators, 91K and 95K actin-associated proteins were partially purified. The 91K-95K fraction has similar activity to the 80K protein regarding precipitation of F-actin. The 125I-G-actin polyacrylamide gel overlay technique [Snabes, M. C., Boyd, A.E., & Bryan, J. (1981) J. Cell Biol. 90, 809-812] revealed that both the 91K and 95K proteins bind 125I-actin after sodium dodecyl sulfate (NaDodSO4) electrophoresis while the 80K and 40K proteins do not. Thyroid 91K protein comigrated with a human platelet 91K actin binding protein on NaDodSO4 gels and may be similar to macrophage gelsolin. The 95K protein may be similar to villin, the intestinal cytoskeletal protein. 相似文献
35.
A method is described for isolating plasma membrane vesicles from bovine tracheal epithelium. The procedure yields highly purified apical membranes which are enriched 19-fold in the marker enzyme, alkaline phosphatase. Contamination of this fraction by other organelles is minimal. Basolateral membranes isolated from the same preparation have a 4-fold enrichment of (Na+ + K+)-ATPase and a 2-fold reduction in alkaline phosphatase specific activity compared to the starting material. Assays of Na+ uptake by the apical membrane vesicles demonstrate their suitability for transport studies. Transport of Na+ into an intravesicular space was demonstrated by (1) a linear inverse correlation between Na+ uptake and medium osmolarity; (2) complete release of accumulated Na+ by treatment with detergent; and (3) a marked temperature-dependence of Na+ uptake rate. Other features of Na+ transport were (1) inhibition by amiloride; (2) insensitivity to furosemide; and (3) anion-dependence of uptake rate with the following selectivity:SCN- greater than Cl- greater than gluconate-. 相似文献
36.
37.
Field Laurence H. 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1974,92(4):415-441
Journal of Comparative Physiology A - 相似文献
38.
39.
Using open-magnitude scaling, we compared the relationships between breathlessness, inspiratory esophageal pressure swing (delta Pes), and ventilation in pregnancy and postpartum. Thirteen healthy women performed progressive cycle exercise tests at 33 +/- 2 wk gestation and 12 +/- 3 wk postpartum. Pulmonary function and maximal transdiaphragmatic pressure did not change. Minute ventilation (VE) was greater in the third trimester. This increase was entirely due to the increase in tidal volume (VT; 0.74 +/- 0.18 vs. 0.54 +/- 0.18 liters at rest, P less than 0.01; 1.56 +/- 0.3 vs. 1.24 +/- 0.24 liters at 48 W, P less than 0.001). delta Pes (15.3 +/- 3.0 vs. 11.9 +/- 3.5 cmH2O at 48 W, P less than 0.01) and breathlessness (1.8 +/- 1.4 vs. 1.0 +/- 0.9 at 48 W, P less than 0.05) were greater in the third trimester. However, the relationships between VT and delta Pes and between delta Pes and breathlessness were identical in the two conditions. The VT-tidal abdominal volume (Vab) and Vab-tidal gastric pressure swing (delta Pga) relationships were similar in the two conditions. In conclusion, the relationship between delta Pes and breathlessness is the same in the third trimester and postpartum. The increased VE is responsible for the breathlessness in the third trimester. Despite progressive abdominal distension by the gravid uterus, the VT-Vab and Vab-delta Pga relationships were the same in the two conditions. 相似文献
40.
Allele-specific expression of the murine Ren-1 genes 总被引:5,自引:0,他引:5
J R Fabian L J Field R A McGowan J J Mullins C D Sigmund K W Gross 《The Journal of biological chemistry》1989,264(29):17589-17594