全文获取类型
收费全文 | 1176篇 |
免费 | 63篇 |
国内免费 | 26篇 |
出版年
2023年 | 23篇 |
2022年 | 35篇 |
2021年 | 35篇 |
2020年 | 24篇 |
2019年 | 33篇 |
2018年 | 47篇 |
2017年 | 24篇 |
2016年 | 26篇 |
2015年 | 55篇 |
2014年 | 84篇 |
2013年 | 71篇 |
2012年 | 70篇 |
2011年 | 69篇 |
2010年 | 50篇 |
2009年 | 48篇 |
2008年 | 54篇 |
2007年 | 47篇 |
2006年 | 52篇 |
2005年 | 44篇 |
2004年 | 36篇 |
2003年 | 26篇 |
2002年 | 31篇 |
2001年 | 13篇 |
2000年 | 26篇 |
1999年 | 23篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 18篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 19篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1974年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有1265条查询结果,搜索用时 15 毫秒
31.
Dennis D. Kunkel 《Archives of microbiology》1982,133(2):97-99
An ultrastructural study of four cyanobacteria (Anabaena cylindrica, Dermocarpa violaceae, Gleocapsa alpicola, Pleurocapsa minor) indicates the presence of previously undescribed thylakoid centers from which photosynthetic membranes (thylakoids) radiate. These peripherally located thylakoid centers are cylinders 30 nm wide by 320 nm long, consisting of globular subunits oriented in nonparallel stacked arrays. Thylakoids are attached to the outer surface of the cylinder along its longitudinal axis. Thylakoid centers appear to be functionally significant due to their structure, location and thylakoid association. 相似文献
32.
Segmental flexibility of ribosomal protein S1 bound to ribosomes and Q beta-replicase 总被引:1,自引:0,他引:1
The protonization pattern of the endogenous donor component D1 which feeds electrons directly into chl-a+II has been analyzed in Tris-washed inside-out thylakoids with the aid of appropriate pH-indicators. It was found that under repetitive flash excitation the amount of protons released is proportional to the extent of D1-oxidation, depending on the time between the flashes. The kinetics of D1-oxidation (being practically the same as in normal Tris-washed chloroplasts) are faster than the proton release by two orders of magnitude. The results lead to the conclusion that D1 is protonized in the reduced state with pK(Dox1) < 5 and becomes deprotonized in the oxidized state with pK(Dred1) ? 8. The proton release is kinetically limited by a transport barrier. Implications on the interpretation of the proton release pattern in preparation with intact water oxidation are discussed. 相似文献
33.
Louis Piovetti Christian Francisco Ginette Pauly Otmane Benchabane Colette Bernard-Dagan Anne Diara 《Phytochemistry》1981,20(6):1299-1302
Analysis of wood essential oil of Cupressus dupreziana revealed 26 components: 13 monoterpenes and 13 sesquiterpenes. The main components were carv 相似文献
34.
Giuseppe Caporale Gabbriella Innocenti Adriano Guiotto Paolo Rodighiero Franceso DallAcqua 《Phytochemistry》1981,20(6):1283-1287
adioactivity from [3H] 5-hydroxymarmesin was incorporated into 5-methoxypsoralen by administration to leaves of Ficus carica and cut ends of Ruta graveolens. No other furanocoumarins were labelled. Trapping experiments, in which [3H]marmesin together with 5-hydroxymarmesin was administered to fig leaves and to cut ends of rue, provided good evidence that 5-hydroxymarmesin is formed by hydroxylation of marmesin. These results, together with those obtained previously with 8-hydroxymarmesin demonstrate that, in addition to the pathway which involves the hydroxylation of psoralen, the O-alkylfuranocoumarins are also formed by a pathway which involves the hydroxylation of marmesin. 相似文献
35.
A vital goal of renewable technology is the capture and re-energizing of exhausted CO2 into usable carbon products. Cyanobacteria fix CO2 more efficiently than plants, and can be engineered to produce carbon feedstocks useful for making plastics, solvents, and medicines. However, fitness of this technology in the economy is threatened by low yields in engineered strains. Robust engineering of photosynthetic microorganisms is lagging behind model microorganisms that rely on energetic carbon, such as Escherichia coli, due in part to slower growth rates and increased metabolic complexity. In this work we show that protein expression from characterized parts is unpredictable in Synechococcus elongatus sp. strain PCC 7942, and may contribute to slow development. To overcome this, we apply a combinatorial approach and show that modulation of the 5'-untranslated region (UTR) can produce a range of protein expression sufficient to optimize chemical feedstock production from CO2. 相似文献
36.
Christian P Craddock Nicolette Adams Fiona M Bryant Smita Kurup Peter J Eastmond 《Plant signaling & behavior》2015,10(10)
Coordination of membrane lipid biosynthesis is important for cell function during plant growth and development. Here we summarize our recent work on PHOSPHATIDIC ACID PHOSPHOHYDROLASE (PAH) which suggests that this enzyme is a key regulator of phosphaticylcholine (PC) biosynthesis in Arabidopsis thaliana. Disruption of PAH activity elevates phosphatidic acid (PA) levels and stimulates PC biosynthesis and biogenesis of the endoplasmic reticulum (ER). Furthermore, the activity of PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE (CCT), which is the key enzyme controlling the rate of PC biosynthesis, is directly stimulated by PA and expression of a constitutively active version of CCT replicates the effects of PAH disruption. Hence PAH activity can control the abundance of PA, which in turn can modulate CCT activity to govern the rate of PC biosynthesis. Crucially it is not yet clear how PAH activity is regulated in Arabidopsis but there is evidence that PAH1 and PAH2 are both phosphorylated and further work will be required to investigate whether this is functionally significant. 相似文献
37.
Federico Machinandiarena Leandro Nakamatsu Gustavo E. Schujman Diego de Mendoza Daniela Albanesi 《Molecular microbiology》2020,114(4):653-663
A key aspect in membrane biogenesis is the coordination of fatty acid to phospholipid synthesis rates. In most bacteria, PlsX is the first enzyme of the phosphatidic acid synthesis pathway, the common precursor of all phospholipids. Previously, we proposed that PlsX is a key regulatory point that synchronizes the fatty acid synthase II with phospholipid synthesis in Bacillus subtilis. However, understanding the basis of such coordination mechanism remained a challenge in Gram-positive bacteria. Here, we show that the inhibition of fatty acid and phospholipid synthesis caused by PlsX depletion leads to the accumulation of long-chain acyl-ACPs, the end products of the fatty acid synthase II. Hydrolysis of the acyl-ACP pool by heterologous expression of a cytosolic thioesterase relieves the inhibition of fatty acid synthesis, indicating that acyl-ACPs are feedback inhibitors of this metabolic route. Unexpectedly, inactivation of PlsX triggers a large increase of malonyl-CoA leading to induction of the fap regulon. This finding discards the hypothesis, proposed for B. subtilis and extended to other Gram-positive bacteria, that acyl-ACPs are feedback inhibitors of the acetyl-CoA carboxylase. Finally, we propose that the continuous production of malonyl-CoA during phospholipid synthesis inhibition provides an additional mechanism for fine-tuning the coupling between phospholipid and fatty acid production in bacteria with FapR regulation. 相似文献
38.
39.
Bacterial endoribonuclease toxins belong to a protein family that inhibits bacterial growth by degrading mRNA or rRNA sequences. The toxin genes are organized in pairs with its cognate antitoxins in the chromosome and thus the activities of the toxins are antagonized by antitoxin proteins or RNAs during active translation. In response to a variety of cellular stresses, the endoribonuclease toxins appear to be released from antitoxin molecules via proteolytic cleavage of antitoxin proteins or preferential degradation of antitoxin RNAs and cleave a diverse range of mRNA or rRNA sequences in a sequence-specific or codon-specific manner, resulting in various biological phenomena such as antibiotic tolerance and persister cell formation. Given that substrate specificity of each endoribonuclease toxin is determined by its structure and the composition of active site residues, we summarize the biology, structure, and substrate specificity of the updated bacterial endoribonuclease toxins. 相似文献
40.
Mohammad Badrul Anam Arif Istiaq Ryusho Kariya Mikiko Kudo Shah Adil Ishtiyaq Ahmad Naofumi Ito Seiji Okada Kunimasa Ohta 《Biochemistry and Biophysics Reports》2021
Previously we reported that, lactic acid bacteria (LAB) can induce human dermal fibroblast (HDF) cells to form multipotent cell clusters which are able to transdifferentiate into three germ layer derived cell lineages. Later on, we confirmed that ribosome is responsible for the LAB-induced transdifferentiation and ribosomes from diverse organisms can mimic the LAB effect on HDF cells. In our present study we have shown that, upon incorporation of ribosomes, non-small cell lung cancer cell line A549 and gastric tubular adenocarcinoma cell line H-111-TC are transformed into spheroid like morphology those can be transdifferentiated into adipocytes and osteoblast. Our qPCR analysis has revealed that, during the formation of ribosome induced cancer cell spheroids, the expression of the cancer cell associated markers and cell cycle/proliferation markers were altered at different time point. Through our investigation, here we report a novel and a non-invasive approach for cancer cell reprogramming by incorporating ribosomes. 相似文献