首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   302篇
  免费   50篇
  2018年   3篇
  2016年   6篇
  2015年   5篇
  2014年   6篇
  2013年   17篇
  2012年   7篇
  2011年   29篇
  2010年   6篇
  2009年   21篇
  2008年   10篇
  2007年   5篇
  2006年   11篇
  2005年   26篇
  2004年   11篇
  2003年   14篇
  2002年   7篇
  2001年   6篇
  2000年   4篇
  1999年   6篇
  1998年   3篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   4篇
  1993年   5篇
  1990年   4篇
  1989年   4篇
  1988年   3篇
  1986年   6篇
  1985年   3篇
  1982年   6篇
  1981年   5篇
  1980年   4篇
  1979年   7篇
  1978年   5篇
  1977年   4篇
  1976年   3篇
  1974年   5篇
  1972年   2篇
  1971年   5篇
  1970年   6篇
  1969年   3篇
  1968年   7篇
  1967年   4篇
  1966年   8篇
  1965年   7篇
  1964年   2篇
  1958年   3篇
  1957年   2篇
  1947年   2篇
排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
2.
Generalized binding phenomena in an allosteric macromolecule   总被引:2,自引:0,他引:2  
A general macromolecular partition function is developed in terms of chemical ligand activity, temperature and pressure for systems described by an array of species which are characterized by their state of allosteric conformation and ligand stoichiometry. The effects of chemical ligand binding, enthalpy change, and volume change are treated in a parallel manner. From a broad viewpoint all of these effects can be regarded as specific cases of generalized binding phenomena. This approach provides a general method for analyzing calorimetric and ligand binding experiments. Several applications are given: (1) Thermal scanning data for tRNAphe (P.L. Privalov and V.V. Filimonov, J. Mol. Biol. 122 (1978) 447) are shown to fit a general model with six conformational states. By application of linkage theory it is shown that sodium chloride is expelled as the molecule denatures. (2) The results of calorimetric titrations on the arabinose binding protein (H. Fukada, J.M. Sturtevant and F.A. Quiocho, J. Mol. Biol. 258 (1983) 13193) are shown to fit a simple two-state allosteric model. (3) A thermal binding curve is simulated for an unusual respiratory protein, trout I hemoglobin (B.G. Barisas and S.J. Gill, Biophys. Chem. 9 (1979) 235), in order to illustrate both the similarities and differences between enthalpy and chemical ligand binding processes.  相似文献   
3.
K F Wertman  A R Wyman  D Botstein 《Gene》1986,49(2):253-262
A class of recombinant phage lambda clones are recovered from human genomic libraries on Escherichia coli recB21 recC22 sbcB15 cells, which fail to form plaques on wild-type cells. We report experiments which address the mechanism of this inhibition. The introduction of the recombination-stimulating sequence chi into one such clone allows growth of this phage on Rec+ cells. In addition, the insertion of lambda gam+ gene into a rec+-inhibited clone results in the ability of the phage to form plaques on wild-type cells. Since lambda Gam protein is an inhibitor of host RecBC enzyme, we tested a collection of such phage for growth on a variety of hosts altered in RecBC function. Host permissiveness correlated with the inactivation of the RecBC nucleolytic activities and not with the recombinational activities. These observations suggest that the inserted DNA sequences of these phage limit the production of packageable chromosomes. This conclusion is easily reconciled with our current knowledge of the interaction of the host recombination systems with lambda replication and encapsidation. Based on these experiments we have constructed strains, both recombination-proficient and recombination-deficient, which serve as improved hosts for the recovery of genomic sequences which are otherwise inhibitory to the growth of phage lambda.  相似文献   
4.
Concerted changes in an allosteric macromolecule   总被引:3,自引:0,他引:3  
This paper reports an analysis of the behaviour of allosteric macromolecules in the framework of the simple Monod-Wyman-Changeux model. The emphasis is on the analysis of the reciprocal influence of the various parameters which enter into the model, with particular reference to the relationship among a number of sites in the macromolecule and the Hill parameter n. This appears of interest for the behaviour of some of the extremely large respiratory proteins containing up to 100, or more, oxygen binding sites, where a very large value of n is often coupled with a relatively small value of the total interaction free energy.  相似文献   
5.
6.
7.
In the marine unicellular chlorophyte, Dunaliella tertiolecta Butcher, the spectrally averaged m vivo absorption cross section, normalized to chlorophyll a (so-called a* values), vary two-fold in response to changes in growth irradiance. We used a kinetic approach to examine the specific factors which account for these changes in optical properties as cells photoadapt. Using Triton X-100 to solubilize membranes, we were able to differentiate between “package” effects and pigmentation effects. Our analyses suggest that 43–49% of the variability in a* is due to changes in pigmentation, whereas 51–57% is due to the “package” effect. Further analyses revealed that changes in cell sue did not significantly affect packaging, while thylakoid stacking and the transparency of thylakoid membranes were important factors. Our results suggest that thylakoid membrane protein/lipid ratios change during photoadaptation, and these changes influence the effective rate of light harvesting per unit chlorophyll a.  相似文献   
8.
The effects of iron limitation on photosystem II (PSII) composition and photochemical energy conversion efficiency were studied in the unicellular chlorophyte alga Dunaliella tertiolecta. The quantum yield of photochemistry in PSII, inferred from changes in variable fluorescence normalized to the maximum fluorescence yield, was markedly lower in iron-limited cells and increased 3-fold within 20 h following the addition of iron. The decrease in the quantum yield of photochemistry was correlated with increased fluorescence emission from the antenna. In iron-limited cells, flash intensity saturation profiles of variable fluorescence closely followed a cumulative one-hit Poisson model, suggesting that PSII reaction centers are energetically isolated, whereas in iron-replete cells, the slope of the profile was steeper and the calculated probability of energy transfer between reaction centers increased to >0.6. Immunoassays revealed that in iron-limited cells the reaction center proteins, D1, CP43, and CP47, were markedly reduced relative to the peripheral light-harvesting Chl-protein complex of PSII, whereas the [alpha] subunit of cytochrome b559 was about 10-fold higher. Spectroscopic analysis established that the cytochrome b559 peptide did not contain an associated functional heme. We conclude that the photochemical conversion of absorbed excitation energy in iron-limited cells is limited by the number of photochemical traps per unit antenna.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号