全文获取类型
收费全文 | 1623篇 |
免费 | 132篇 |
国内免费 | 33篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 16篇 |
2021年 | 29篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 45篇 |
2017年 | 42篇 |
2016年 | 45篇 |
2015年 | 57篇 |
2014年 | 76篇 |
2013年 | 138篇 |
2012年 | 45篇 |
2011年 | 59篇 |
2010年 | 40篇 |
2009年 | 70篇 |
2008年 | 80篇 |
2007年 | 69篇 |
2006年 | 62篇 |
2005年 | 57篇 |
2004年 | 52篇 |
2003年 | 48篇 |
2002年 | 48篇 |
2001年 | 39篇 |
2000年 | 24篇 |
1999年 | 33篇 |
1998年 | 34篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 29篇 |
1994年 | 41篇 |
1993年 | 33篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 26篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有1788条查询结果,搜索用时 23 毫秒
961.
Water-protein interactions in the molten-globule state of carbonic anhydrase b: an NMR spin-diffusion study
下载免费PDF全文
![点击此处可从《Protein science : a publication of the Protein Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have used the homonuclear Overhauser effect (NOE) to characterize a model protein: carbonic anhydrase B. We have obtained NOE difference spectra for this protein, centering the on-resonance signals either at the methyl-proton or at the water-proton signals. The spin-diffusion spectra obtained as a function of protein concentration and temperature provide direct evidence of much greater protein-water interaction in the molten-globule state than in the native and denatured states. Furthermore, although the protein loses its gross tertiary structure in both the molten-globule and denatured states, it remains almost as compact in its molten-globule state as it is in the native state. The spin-diffusion spectra, obtained as a function of a variable delay time after the saturation pulse, allowed us to measure the relaxation times of several types of proton in the solution. These spectra contain enough information to distinguish between those water molecules solvating the protein and the free ones present as bulk water. 相似文献
962.
Hashimoto Y Smith SP Pickford AR Bocquier AA Campbell ID Werner JM 《Journal of biomolecular NMR》2000,17(3):203-214
The structure of a pair of modules (6F11F2), that forms part of the collagen-binding region of fibronectin, is refined using heteronuclear relaxation data. A structure of the pair was previously derived from 1H-1H NOE and 3
J
HHN data [Bocquier et al. (1999) Structure, 7, 1451–1460] and a weak module–module interface, comprising Leu19 and Leu28, in 6F1, and Tyr68 in 2F1, was identified. In this study, the definition of the average relative orientation of the two modules is improved using the dependence of 15N relaxation on rotational diffusion anisotropy. This structure refinement is based on the selection of a subset of structures from sets calculated with NOE and 3
J
HHN data alone, using the quality of the fits to the relaxation data as the selection criterion. This simple approach is compared to a refinement strategy where 15N relaxation data are included in the force field as additional restraints [Tjandra et al. (1997) Nat. Struct. Biol., 4, 443–449]. 相似文献
963.
In the RNA world hypothesis, RNA(-like) self-replicators are suggested as the central player of prebiotic evolution. However, there is a serious problem in the evolution of complexity in such replicators, i.e., the problem of parasites. Parasites, which are replicated by catalytic replicators (catalysts), but do not replicate the others, can destroy a whole replicator system by exploitation. Recently, a theoretical study underlined complex formation between replicators--an often neglected but realistic process--as a stabilizing factor in a replicator system by demonstrating that complex formation can shift the viable range of diffusion intensity to higher values. In the current study, we extend the previous study of complex formation. Firstly, by investigating a well-mixed replicator system, we establish that complex formation gives parasites an implicit advantage over catalysts, which makes the system significantly more vulnerable to parasites. Secondly, by investigating a spatially extended replicator system, we show that the formation of traveling wave patterns plays a crucial role in the stability of the system against parasites, and that because of this the effect of complex formation is not straightforward; i.e., whether complex formation stabilizes or destabilizes the spatial system is a complex function of other parameters. We give a detailed analysis of the spatial system by considering the pattern dynamics of waves. Furthermore, we investigate the effect of deleterious mutations. Surprisingly, high mutation rates can weaken the exploitation of the catalyst by the parasite. 相似文献
964.
965.
Chongfu Huang 《人类与生态风险评估》2015,21(5):1395-1409
ABSTRACTIn this article, we clarify the concept of the Internet of Intelligences (IOI) to be a platform for risk analysis. An IOI is a triple consisting of a set of agents, a network, and a model. A process of processing homological information is a layer. An IOI with more than one layer is a Multiple Internet of Intelligences (M-IOI). If agents in an M-IOI not only provide information in response to a question asked by a customer but also review information from other agents and summarize it, we refer to this as a summarizing M-IOI. In this article, a simplest M-IOI is used to answer a question issued by an insurance company considering selling policies in Wenzhou, China, where the level of typhoon risk is high. We employ the normal diffusion model to process the summaries and give an adequate answer. 相似文献
966.
Joscha Breibeck Annette Rompel 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(2):437-455
Background
Membrane proteins constitute a major group of proteins and are of great significance as pharmaceutical targets, but underrepresented in the Protein Data Bank. Particular reasons are their low expression yields and the constant need for cautious and diligent handling in a sufficiently stable hydrophobic environment substituting for the native membrane. When it comes to protein crystallization, such an environment is often established by detergents.Scope of review
In this review, 475 unique membrane protein X-ray structures from the online data bank “Membrane proteins of known 3D structure” are presented with a focus on the detergents essential for protein crystallization. By systematic analysis of the most successful compounds, including current trends in amphiphile development, we provide general insights for selection and design of detergents for membrane protein crystallization.Major conclusions
The most successful detergents share common features, giving rise to favorable protein interactions. The hydrophile-lipophile balance concept of well-balanced hydrophilic and hydrophobic detergent portions is still the key to successful protein crystallization. Although a single detergent compound is sufficient in most cases, sometimes a suitable mixture of detergents has to be found to alter the resulting protein-detergent complex. Protein crystals with a high diffraction limit involve a tight crystal packing generally favored by detergents with shorter alkyl chains.General significance
The formation of well-diffracting membrane protein crystals strongly depends on suitable surfactants, usually screened in numerous crystallization trials. The here-presented findings provide basic criteria for the assessment of surfactants within the vast space of potential crystallization conditions for membrane proteins. 相似文献967.
968.
The degree of macromolecular crowding in the cytoplasm and nucleoplasm of mammalian cells is conserved 总被引:1,自引:0,他引:1
Macromolecular crowding provides the cytoplasm and the nucleoplasm with strongly viscoelastic properties and renders the diffusion of soluble proteins in both fluids anomalous. Here, we have determined the nanoscale viscoelasticity of the cytoplasm and the nucleoplasm in different mammalian cell lines. In contrast to the cell-specific response on the macroscale the nanoscale viscoelasticity (i.e. the behavior on length scales about 100-fold smaller than the cell size) only showed minor variations between different cell types. Similarly, the associated anomalous diffusion properties varied only slightly. Our results indicate a conserved state of macromolecular crowding in both compartments for a variety of mammalian cells with the cytoplasm being somewhat more crowded than the nucleus. 相似文献
969.
The antimicrobial activities of chloroform, acetone and two different concentrations of methanol extracts of Artemisia dracunculus L. were studied. These extracts were tested against nine bacteria and four yeasts strains by the disc diffusion method. The results indicated that the methanol extract of A. dracunculus is more effective against tested microorganisms than chloroform or acetone extracts. The chloroform and acetone extracts were inhibitory only towards Pseudomonas aeruginosa (ATCC 27853). While the methanol extract that was diluted with 10 ml distilled water showed inhibition zones against Shigella (RSHI), Listeria monocytogenes ATCC 7644, P. aeruginosa (ATCC 27853), the methanol extract that was diluted with 5 ml distilled water showed inhibition zones against two different strains of Escherichia coli (RSHI, ATCC 25922), Shigella (RSHI), L. monocytogenes (ATCC 7644), and P. aeruginosa ATCC 27853. The cells of microorganisms treated with plant extracts and normal microorganism cells were observed by scanning electron microscope. It was apparent that cells are damaged after treatment with A. dracunculus. 相似文献
970.
The delivery of oxygen to tissue by cell-free carriers eliminates intraluminal barriers associated with red blood cells. This is important in arterioles, since arteriolar tone controls capillary perfusion. We describe a mathematical model for O(2) transport by hemoglobin solutions and red blood cells flowing through arteriolar-sized tubes to optimize values of p50, Hill number, hemoglobin molecular diffusivity and concentration. Oxygen release is evaluated by including an extra-luminal resistance term to reflect tissue oxygen consumption. For low consumption (i.e., high resistance to O(2) release) a hemoglobin solution with p50=15 mmHg, n=1, D(HBO2)=3 x 10(-7) cm(2)/s delivers O(2) at a rate similar to that of red blood cells. For high consumption, the p50 must be decreased to 5 mmHg. The model predicts that regardless of size, hemoglobin solutions with higher p50 will present excess O(2) to arteriolar walls. Oversupply of O(2) to arteriolar walls may cause constriction and paradoxically reduced capillary perfusion. 相似文献