全文获取类型
收费全文 | 2930篇 |
免费 | 311篇 |
国内免费 | 2篇 |
专业分类
3243篇 |
出版年
2023年 | 19篇 |
2022年 | 27篇 |
2021年 | 42篇 |
2020年 | 41篇 |
2019年 | 49篇 |
2018年 | 51篇 |
2017年 | 55篇 |
2016年 | 70篇 |
2015年 | 144篇 |
2014年 | 150篇 |
2013年 | 171篇 |
2012年 | 263篇 |
2011年 | 242篇 |
2010年 | 150篇 |
2009年 | 135篇 |
2008年 | 206篇 |
2007年 | 181篇 |
2006年 | 173篇 |
2005年 | 173篇 |
2004年 | 169篇 |
2003年 | 154篇 |
2002年 | 152篇 |
2001年 | 37篇 |
2000年 | 24篇 |
1999年 | 30篇 |
1998年 | 37篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 31篇 |
1994年 | 15篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1969年 | 5篇 |
1962年 | 3篇 |
1952年 | 2篇 |
排序方式: 共有3243条查询结果,搜索用时 15 毫秒
21.
22.
Poetsch A Berzborn RJ Heberle J Link TA Dencher NA Seelert H 《Journal of biochemistry》2007,141(3):411-420
ATP synthases convert an electrochemical proton gradient into rotational movement to produce the ubiquitous energy currency adenosine triphosphate. Tension generated by the rotational torque is compensated by the stator. For this task, a peripheral stalk flexibly fixes the hydrophilic catalytic part F1 to the membrane integral proton conducting part F(O) of the ATP synthase. While in eubacteria a homodimer of b subunits forms the peripheral stalk, plant chloroplasts and cyanobacteria possess a heterodimer of subunits I and II. To better understand the functional and structural consequences of this unique feature of photosynthetic ATP synthases, a procedure was developed to purify subunit I from spinach chloroplasts. The secondary structure of subunit I, which is not homologous to bacterial b subunits, was compared to heterologously expressed subunit II using CD and FTIR spectroscopy. The content of alpha-helix was determined by CD spectroscopy to 67% for subunit I and 41% for subunit II. In addition, bioinformatics was applied to predict the secondary structure of the two subunits and the location of the putative coiled-coil dimerization regions. Three helical domains were predicted for subunit I and only two uninterrupted domains for the shorter subunit II. The predicted length of coiled-coil regions varied between different species and between subunits I and II. 相似文献
23.
24.
Schöneberg T Hermsdorf T Engemaier E Engel K Liebscher I Thor D Zierau K Römpler H Schulz A 《Purinergic signalling》2007,3(4):255-268
Metabotropic pyrimidine and purine nucleotide receptors (P2Y receptors) belong to the superfamily of G protein-coupled receptors
(GPCR). They are distinguishable from adenosine receptors (P1) as they bind adenine and/or uracil nucleotide triphosphates
or diphosphates depending on the subtype. Over the past decade, P2Y receptors have been cloned from a variety of tissues and
species, and as many as eight functional subtypes have been characterized. Most recently, several members of the P2Y12-like receptor group, which includes the clopidogrel-sensitive ADP receptor P2Y12, have been deorphanized. The P2Y12-like receptor group comprises several structurally related GPCR which, however, display heterogeneous agonist specificity
including nucleotides, their derivatives, and lipids. Besides the established function of P2Y12 in platelet activation, expression in macrophages, neuronal and glial cells as well as recent results from functional studies
implicate that several members of this group may have specific functions in neurotransmission, inflammation, chemotaxis, and
response to tissue injury. This review focuses specifically on the structure-function relation and shortly summarizes some
aspects of the physiological relevance of P2Y12-like receptor members. 相似文献
25.
26.
Intraspecific Variation of Unusual Phospholipids from Corynebacterium spp. Containing a Novel Fatty Acid 下载免费PDF全文
Tanja Niepel Holger Meyer Victor Wray Wolf-Rainer Abraham 《Journal of bacteriology》1998,180(17):4650-4657
The novel fatty acid trans-9-methyl-10-octadecenoic acid was isolated from the coryneform bacterial strain LMG 3820 (previously misidentified as Arthrobacter globiformis) and identified by spectroscopic methods and chemical derivatization. This fatty acid is attached to the unusual lipid acyl phosphatidylglycerol. Five different species of this lipid type were identified; their structures were elucidated by tandem mass spectrometry and are reported here for the first time. Additionally, we identified three different cardiolipins, two bearing the novel fatty acid. The characteristic 10-methyl-octadecanoic acid was present only in phosphatidylinositol. Because of the unusual fatty acid pattern of strain LMG 3820, the 16S rDNA sequence was determined and showed regions of identity to sequences of Corynebacterium variabilis DSM 20132T and DSM 20536. All three strains possessed the novel fatty acid, identifying trans-9-methyl-10-octadecenoic acid as a potential biomarker characteristic for this taxon. Surprisingly, the fatty acid and relative abundances of phospholipids of Corynebacterium sp. strain LMG 3820 were similar to those of the type strain but different from those of Corynebacterium variabilis DSM 20536, although all three strains possessed identical 16S rDNA sequences and strains DSM 20132T and DSM 20536 have 90.5% DNA-DNA homology. This is one of the rare cases wherein different organisms with identical 16S rDNA sequences have been observed to present recognizably different fatty acid and lipid compositions. Since methylation of a fatty acid considerably lowers the transition temperature of the corresponding lipid resulting in a more flexible cell membrane, the intraspecific variation in the lipid composition, coinciding with the morphological and Gram stain reaction variability of this species, probably offers an advantage for this species to inhabit different environmental niches. 相似文献
27.
As Drosophila melanogaster does not contain glutathione reductase, the thioredoxin system has a key function for glutathione disulfide reduction in insects (Kanzok, S. M., Fechner, A., Bauer, H., Ulschmid, J. K., Müller, H. M., Botella-Munoz, J., Schneuwly, S., Schirmer, R. H., and Becker, K. (2001) Science 291, 643-646). In view of these unique conditions, the protein systems participating in peroxide metabolism and in redox signaling are of special interest. The genes for a second thioredoxin (DmTrx-2) and a thioredoxin peroxidase (DmTPx-1) were cloned and expressed, and the proteins were characterized. In its disulfide form, the 13-kDa protein thioredoxin-2 is a substrate of thioredoxin reductase-1 (K(m) = 5.2 microm, k(cat) = 14.5 s(-1)) and in its dithiol form, an electron donor for TPx-1 (K(m) = 9 microm, k(cat) = 5.4 s(-1)). DmTrx-2 is capable of reducing glutathione disulfide with a second order rate constant of 170 m(-1) s(-1) at pH 7.4 and 25 degrees C. Western blot analysis indicated that this thioredoxin represents up to 1% of the extractable protein of D. melanogaster Schneider cells or whole fruit flies. Recombinant thioredoxin peroxidase-1 (subunit molecular mass = 23 kDa) was found to be a decameric protein that can efficiently use Trx-2 but not Trx-1 as a reducing substrate. The new electron pathway found in D. melanogaster is also representative for insects that serve as vectors of disease. As a first step we have cloned and functionally expressed the gene that is the orthologue of DmTrx-2 in the malaria mosquito Anopheles gambiae. 相似文献
28.
29.
30.
Therapeutic targeting of innate immunity with Toll-like receptor agonists and antagonists 总被引:10,自引:0,他引:10
The identification of the antigen recognition receptors for innate immunity, most notably the Toll-like receptors, has sparked great interest in therapeutic manipulation of the innate immune system. Toll-like receptor agonists are being developed for the treatment of cancer, allergies and viral infections, and as adjuvants for potent new vaccines to prevent or treat cancer and infectious diseases. As recognition grows of the role of inappropriate Toll-like receptor stimulation in inflammation and autoimmunity, significant efforts have begun to develop antagonists to Toll-like receptors as well. 相似文献