全文获取类型
收费全文 | 902篇 |
免费 | 69篇 |
国内免费 | 37篇 |
出版年
2023年 | 22篇 |
2022年 | 38篇 |
2021年 | 42篇 |
2020年 | 14篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 38篇 |
2013年 | 70篇 |
2012年 | 29篇 |
2011年 | 30篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 33篇 |
2007年 | 36篇 |
2006年 | 43篇 |
2005年 | 37篇 |
2004年 | 33篇 |
2003年 | 42篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 24篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有1008条查询结果,搜索用时 15 毫秒
101.
Mutant hemoglobin stability depends upon location and nature of single point mutation 总被引:1,自引:0,他引:1
The temperature dependence of the rates of heme release from the beta subunits of methemoglobin A and 5 beta mutant methemoglobins has been determined. The rates were largest for two hemoglobins with mutations distal to heme, previously known to be unstable. The other 3 mutants also released heme faster than A. These hemoglobins, with single point mutations at the alpha 1/beta 2 interface, were previously thought to be stable. The low reported yields of the 5 mutant proteins covaries with the relative rates of heme release from the met species. 相似文献
102.
E. Lendaro R. Ippoliti A. Brancaccio A. Bellelli B. Vallone G. Ivaldi G.V. Sciarratta C. Castello S. Tomova M. Brunori G. Amiconi 《生物化学与生物物理学报:疾病的分子基础》1992,1180(1):15-20
Hemoglobin Dallas, an α-chain variant with a substitution of lysine for asparagine at position 97(G4), was found to have increased oxygen affinity () and reduced Bohr effect (about 50%). Addition of allosteric effectors (such as 2,3-diphosphoglycerate, inositol hexakisphosphate and bezafibrate) led to a decrease in oxygen affinity and increase in cooperative energy. Kinetic studies at pH 7.0 and 20°C revealed that (i), the overall rate of oxygen dissociation is 1.4-fold slower than that for HbA and (ii), the carbon monoxide dissociation rate is unaffected. The abnormal properties of this hemoglobin variant can be atttributed to a more ‘relaxed’ T-state. 相似文献
103.
Primary structure of -chain of pigeon is presented. It was determined by amino acid sequence analysis of intact -chain and its peptides obtained by the enzymatic and chemical cleavage. Comparison of amino acid sequence of the chain with other available data shows 14 Ile, 61 Lys, and 113 Ile as residues specific to pigeon. One important replacement at 11 contact is 55 MetSer. 相似文献
104.
Properties of a recombinant human hemoglobin double mutant: sickle hemoglobin with Leu-88(beta) at the primary aggregation site substituted by Ala. 总被引:3,自引:3,他引:0 下载免费PDF全文
J. J. Martin de Llano J. M. Manning 《Protein science : a publication of the Protein Society》1994,3(8):1206-1212
A recombinant double mutant of hemoglobin (Hb), E6V/L88A(beta), was constructed to study the strength of the primary hydrophobic interaction in the gelation of sickle Hb, i.e., that between the mutant Val-6(beta) of one tetramer and the hydrophobic region between Phe-85(beta) and Leu-88(beta) on an adjacent tetramer. Thus, a construct encoding the donor Val-6(beta) of the expressed recombinant HbS and a second mutation encoding an Ala in place of Leu-88(beta) was assembled. The doubly mutated beta-globin gene was expressed in yeast together with the normal human alpha-chain, which is on the same plasmid, to produce a soluble Hb tetramer. Characterizations of the Hb double mutant by mass spectrometry, by HPLC, and by peptide mapping of tryptic digests of the mutant beta-chain were consistent with the desired mutations. The absorption spectra in the visible and the ultraviolet regions were practically superimposable for the recombinant Hb and the natural Hb purified from human red cells. Circular dichroism studies on the overall structure of the recombinant Hb double mutant and the recombinant single mutant, HbS, showed that both were correctly folded. Functional studies on the recombinant double mutant indicated that it was fully cooperative. However, its gelation concentration was significantly higher than that of either recombinant or natural sickle Hb, indicating that the strength of the interaction in this important donor-acceptor region in sickle Hb was considerably reduced even with such a conservative hydrophobic mutation. 相似文献
105.
Numerous studies have demonstrated that several diseases and stress conditions are associated with changes in the levels of zinc in the blood plasma and cellular elements. In this research the association between serum zinc concentrations and other hematic parameters of diagnostic interest has been evaluated. Quantitative determinations of zinc, total plasmatic proteins, albumin, hemoglobin and calculation of mean corpuscular volume were performed on blood samples from 58 males aged 20–61 years. Concentrations measured in our sample are comparable with reference values. Statistically significant correlation coefficients were found between age and albumin (r = - 0.562, P < 0.001), serum zinc and albumin (r = 0.328, P < 0.05), serum zinc and hemoglobin (r = 0.291, P < 0.05), and total plasmatic proteins and albumin (r = 0.463, P < 0.001). These correlation coefficients were significant even after adjustment for age effect. The determination of serum zinc concentration may be useful in the assessment of clinical scenarios. Particularly, it may provide additional information for the diagnosis of specific pathologies, such as hepatic malfunctions. It could also be useful in the identification of different stages of anemia. 相似文献
106.
Th. Wurm C. Albers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(3):255-261
Summary The interaction of allosteric effectors (CO2, ATP, H+) with respect to the oxygen affinity of carp hemoglobin was analyzed by determining oxygen binding curves spectrophotometrically in dilute solutions of stripped hemoglobin at 20°C. The pH range studied was 6.8–8.2.P
CO2 was 0, 10 and 70 mmHg (0, 1.33 and 9.3 kPa). ATP/Hb4 was 0, 8 and 24. In the presence of either CO2 or ATP, the effects of the cofactors onP
50 were as expected over the whole pH range. In contrast to other published data, each cofactor also had a significant effect onP
50 in the presence of the other cofactor. Evidence was obtained that oxylabile carbamate is formed by carp hemoglobin and that the formation of carbamate persists at a lower level in the presence of ATP. The results support the view that the binding of ATP to carp hemoglobin requires only one terminal amino group, leaving the other N-terminal of the -chain free to react with CO2. 相似文献
107.
Summary A cloned cDNA partial copy of a soybean leghemoglobin mRNA was used to probe genomic DNA of four species of actinorhizal plants. Southern blot hybridization revealed the presence of sequences with homology to the leghemoglobin probe in DNA from Alnus glutinosa, Casuarina glauca, Ceanothus americanus and Elaeagnus pungens. The hybridization patterns of the restriction fragments revealed some fragment size conservation between the DNA of soybean and the DNA of four actinorhizal plants which are taxonomically unrelated to soybean or to each other. The results presented here indicate that globin gene sequences are much more widely distributed in the plant kingdom than has previously been thought. Furthermore, if sequence conservation is actually as high as the restriction fragment patterns suggest, the evolution of the DNA surrounding the globin sequences has been highly constrained. 相似文献
108.
The complete amino acid sequence of the major component of hemoglobin from amur-leopard (Panthera pardus orientalis) is presented. The major component accounts for more than 90% of the total hemoglobin. Separation of the globin subunits was achieved by ion-exchange chromatography on CM-cellulose in urea. The sequence was studied by automatic Edman degradation of tryptic and hydrolytic peptides. Alignment was carried out with human hemoglobin sequence. The NH2 terminus is blocked with Ac-serine. The data are compared with other mammalian hemoglobins and results are discussed with respect to sequence and physiology.85th communication on hemoglobin. 相似文献
109.
Osmotic properties of human red cells 总被引:2,自引:0,他引:2
Summary When an osmotic pressure gradient is applied to human red cells, the volume changes anomalously, as if there were a significant fraction of nonosmotic water which could not serve as solvent for the cell solutes, a finding which has been discussed widely in the literature. In 1968, Gary-Bobo and Solomon (J. Gen. Physiol.
52:825) concluded that the anomalies could not be entirely explained by the colligative properties of hemoglobin (Hb) and proposed that there was an additional concentration dependence of the Hb charge (zHb). A number of investigators, particularly Freedman and Hoffman (1979,J. Gen. Physiol.
74:157) have been unable to confirm Gary-Bobo and Solomon's experimental evidence for this concentration dependence of zHb and we now report that we are also unable to repeat the earlier experiments. Nonetheless, there still remains a significant anomaly which amounts to 12.5±0.8% of the total isosmotic cell water (P0.0005,t test), even after taking account of the concentration dependence of the Hb osmotic coefficient and all the other known physical chemical constraints, ideal and nonideal. It is suggested that the anomalies at high Hb concentration in shrunken cells may arise from the ionic strength dependence of the Hb osmotic coefficient. In swollen red cells at low ionic strength, solute binding to membrane and intracellular proteins is increased and it is suggested that this factor may account, in part, for the anomalous behavior of these cells. 相似文献
110.
M.D. Fiechtner G. McLendon M.W. Bailey 《Biochemical and biophysical research communications》1980,92(1):277-284
Chromium(III) substituted hemoglobin has been prepared. Circular dichroism spectra in the UV region have been recorded in the presence and absence of the allosteric affector inositol hexaphosphate. The reactivity with bromthymol blue and p-mercuribenzoate has been measured. All data indicate a T state (or T state-like) structure, whereas an R structure would be expected from the chromium stereochemistry. Similarities to cobalt(III) hemoglobin suggest that the chromium derivative also exists as an internal hemichrome. Thus, despite major tertiary structure differences, “denatured” hemichromes may have a quaternary structure quite similar to deoxyhemoglobin. 相似文献