全文获取类型
收费全文 | 6157篇 |
免费 | 419篇 |
国内免费 | 229篇 |
出版年
2024年 | 20篇 |
2023年 | 111篇 |
2022年 | 164篇 |
2021年 | 176篇 |
2020年 | 157篇 |
2019年 | 213篇 |
2018年 | 260篇 |
2017年 | 180篇 |
2016年 | 191篇 |
2015年 | 230篇 |
2014年 | 269篇 |
2013年 | 681篇 |
2012年 | 179篇 |
2011年 | 218篇 |
2010年 | 218篇 |
2009年 | 237篇 |
2008年 | 229篇 |
2007年 | 296篇 |
2006年 | 293篇 |
2005年 | 279篇 |
2004年 | 198篇 |
2003年 | 193篇 |
2002年 | 181篇 |
2001年 | 155篇 |
2000年 | 120篇 |
1999年 | 98篇 |
1998年 | 104篇 |
1997年 | 110篇 |
1996年 | 94篇 |
1995年 | 100篇 |
1994年 | 69篇 |
1993年 | 64篇 |
1992年 | 87篇 |
1991年 | 49篇 |
1990年 | 54篇 |
1989年 | 61篇 |
1988年 | 59篇 |
1987年 | 55篇 |
1986年 | 47篇 |
1985年 | 51篇 |
1984年 | 68篇 |
1983年 | 36篇 |
1982年 | 45篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 9篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有6805条查询结果,搜索用时 15 毫秒
141.
G. Solaini A. Baracca G. Parenti Castelli G. Lenaz 《Journal of bioenergetics and biomembranes》1984,16(5-6):391-406
The temperature dependence of the oligomycin-sensitive ATPase (complex V) kinetic parameters has been investigated in enzyme preparations of different phospholipid composition. In submitochondrial particles, isolated complex V, and complex V reconstituted in dimirystoyl lecithin vesicles, the Arrhenius plots show discontinuities in the range 18–28°C, while no discontinuity is detected with dioleoyl lecithin recombinant. Van't Hoff plots ofK
m
also show breaks in the same temperature interval, with the exception of the dioleoylenzyme vesicles, whereK
m
is unchanged. Thermodynamic analysis of the ATPase reaction shows that DMPC-complex V has rather larger values of activation enthalpy and activation entropy below the transition temperature (24°C) than those of the other preparations, while all enzyme preparations show similar free energies of activation (14.3–18.5 kcal/mol). The results indicate that temperature and lipid composition influence to a different extent both kinetic and thermodynamic parameters of ATP hydrolysis catalyzed by the mitochondrial ATPase. 相似文献
142.
A. Alfsen C. de Paillerets K. Prasad P. K. Nandi R. E. Lippoldt H. Edelhoch 《European biophysics journal : EBJ》1984,11(2):129-136
Three characteristics have been demonstrated by the chemical analysis of bovine brain coated vesicles following removal of the coat proteins: a high protein content, a high cholesterol/lipid ratio and a high percentage of phosphatidylethanolamine amongst the phospholipids.The study of lipid bilayer organization and dynamics has been performed using the fluorescent probes pyrene and parinaric acid (cis and trans). This has allowed the study of both lateral mobility and rotational motion in the lipid bilayer of the coated and uncoated vesicles.Lateral mobility in the fluid phase of the lipid is slightly reduced by the presence of the clathrin coat, as indicated by the lower diffusion coefficient of pyrene in coated compared with uncoated vesicles.At all temperatures from 6° to 30°C, solid-phase domains, probed by trans parinaric acid, coexist with fluid-phase domains in the lipid bilayer. The temperature dependence of the parinaric acid lifetimes and of their amplitudes strongly suggests that the solid phase domains decrease in size with temperature, both in coated and uncoated vesicles.However, the difference in the value of the anisotropy at long times (r
), between coated and uncoated vesicles (a difference which is more pronounced for cis than for trans parinaric acid), indicates that the presence of the clathrin coat introduces disorder in the surrounding lipids, thus suggesting a possible role of the clathrin in the formation of the pits on the plasma membrane.Abbreviations CVs
coated vesicles
- UVs
uncoated vesicles
- TLC
thin layer chromatography
- DMSO
dimethylsulfoxide
- DPPC
dipalmitoylphosphatidylcholine
-
cis Pna
cis parinaric acid
- (9,11,13,15-cis-trans-trans-cis)
octadecatetraenoic acid
-
Trans Pna
Trans parinaric acid
- (9,11,13,15-all-trans)
octadecatetraenoic acid 相似文献
143.
A.G. MacDonald 《生物化学与生物物理学报:生物膜》1984,775(2):141-149
Tetrahymena was grown at up to 260 atm to see if the bilayer-ordering effect of pressure increased the proportion of unsaturated fatty acids in the membrane lipids. Both whole cells and microsomes showed no such change in their fatty acid composition. The most striking effect was seen in the former which showed a pressure-dependent increase in the proportion of C16:0 in relation to C16:Δ9. Homeoviscous adaptation to pressure does not appear to occur in this cell. 相似文献
144.
The reconstitution of chloroplast coupling factor ATP synthetase (CF1 · CF0) with thylakoid lipids by cholate dialysis produced vesicles that displayed higher steady-state anisotropy (rs) values for both 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium-diphenyl hexatriene fluorescence than the pure lipid alone. This is interpreted as meaning that the insertion of protein into the lipid bilayer brings about an increase in the ordering of acyl chains. This ordering effect became more obvious as the protein-to-lipid ratio was increased. Time-resolved decay analyses of DPH fluorescence anisotropy confirmed the conclusion drawn from the steady-state measurements, but further indicated that the dynamic motion of the probe was also slightly restricted after CF1 · CF0 incorporation. The restriction of DPH motion and the change in the half-angle for its cone of rotation was observed at relatively low protein-to-lipid ratios as compared with other reconstituted or biological membranes, suggesting that perhaps lipid-protein interactions occur with the inserted CF1 · CF0 complex. 相似文献
145.
Transport of mercury compounds across bimolecular lipid membranes: effect of lipid composition, pH and chloride concentration 总被引:2,自引:0,他引:2
E Bienvenue A Boudou J P Desmazes C Gavach D Georgescauld J Sandeaux P Seta 《Chemico-biological interactions》1984,48(1):91-101
The use of bimolecular lipid membranes (BLM) as model membrane allows the analysis of the transport of mercury compounds across the lipidic barriers of biological membranes. The results of flux measurements show that two mercury compounds--HgCl2 and CH3HgCl--cross the BLM but the overall permeabilities are dependent on the pH of the aqueous media, and are not apparently influenced by the different phospholipid constituents of the bilayers. On the other hand, electrical measurements show that, function of the chemical speciation, the transport of this metal is done essentially in the neutral form. 相似文献
146.
The depression of the phase-transition temperature of dimyristoyl- and dipalmitoylphosphatidylcholine vesicles induced by phenol has been investigated by fluorescence polarization. This effect is strongly pH and concentration dependent. Only the uncharged phenol molecule influences the fluidity of the bilayer so that the interaction of phenol with the bilayer can be situated in the hydrophobic acyl chain region. Direct measurements of the partitioning of phenol in the phospholipid vesicles confirm these results and show a limited and concentration-dependent solubility. Phase-transition temperature depressions, obtained from thermodynamic analysis of partition coefficient measurement, are in good agreement with the experimental values. 相似文献
147.
Biological activities of chemically synthesized analogues of the nonreducing sugar moiety of lipid A 总被引:12,自引:0,他引:12
M Matsuura Y Kojima J Y Homma Y Kubota A Yamamoto M Kiso A Hasegawa 《FEBS letters》1984,167(2):226-230
Adriamycin-Fe3+ complex catalyzes the formation of hydroxyl radical from hydrogen peroxide but the DNA-adriamycin-iron ternary complex is much more effective. 11-Deoxyadriamycin, which shows no spectral evidence of complex formation with iron, was ineffective. The generation of hydroxyl radical by adriamycin-Fe3+ complex in the presence of DNA correlates with its ability to cleave DNA. Hydroxyl radicals are thus implicated as the reactive oxygen species involved in the DNA damage caused by the adriamycin-Fe3+ complex. 相似文献
148.
Craig A. Halverson Alfred F. Esser Kenneth A. Souza 《Journal of cellular biochemistry》1978,8(2):129-138
Bacillus stearothermophilus cells vary the lipid fatty acid composition of cytoplasmic membranes with growth temperature. Spin label studies of such membranes have been interpreted to indicate lateral lipid phase separations at the growth temperature. We have now used freeze-fracture electron microscopy to confirm the spin label studies. Freeze-fracture faces of protoplasts indicate slight but distinct protein aggregation at the growth temperature. Aggregation increases rapidly with decreasing quench temperature in wild-type cells. In contrast we were unable to demonstrate extended protein segregation in membranes of a temperature-sensitive mutant that contains more than 58% branched fatty acids. Storage of protoplasts for prolonged times below the lipid phase transition results in the appearance of corrugated fracture faces with 300- to 500-Å repeat patterns, although this organism does not synthesize lecithins. 相似文献
149.
The fatty acid compositions of the ether lipid 1(3),2-diacylglyceryl-(3)-O-4′-(N,N,N-trimethyl)homoserine (DGTS) from Ochromonas danica a 相似文献
150.
Wide-angle X-ray diffraction studies have indicated that rough and smooth microsomal membranes from bean cotyledons acquire increasing proportions of gel phase lipid at physiological temperature as the tissue senesces. In addition, for both types of membrane the lipid phase transition temperature, defined as the highest temperature at which gel phase lipid can be detected, progressively rises with advancing senescence. Liposomes prepared from total lipid extracts of the membranes show a similar increase in transition temperature with age, indicating that separation of the polar lipids into distinct gel and liquid-crystalline domains is not attributable to peculiar protein-lipid interactions. Liposomes prepared from purified phospholipid fractions of the membranes show little change in transition temperature with age, indicating that the altered phase properties of the lipid do not reflect an increase in fatty acid saturation. However, the formation of gel phase lipid that occurs naturally during senescence can be stimulated by preparing liposomes from a mixture of the phospholipid fraction from young membrane and the neutral lipid fraction from old membrane. By adding the separated components of the neutral lipid fraction to purified phospholipid it was found that sterol esters and several unidentified lipids are able to raise the transition temperature of the polar lipids. Sterols have no effect on the phospholipid transition temperature. The data have been interpreted as indicating that several neutral lipids, which presumably increase in abundance with advancing senescence, induce a lateral phase separation of the polar lipids resulting in distinct gel and liquid-crystalline domains of lipid in the senescent membranes. 相似文献