全文获取类型
收费全文 | 697篇 |
免费 | 44篇 |
专业分类
741篇 |
出版年
2023年 | 5篇 |
2022年 | 16篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 24篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 34篇 |
2014年 | 34篇 |
2013年 | 44篇 |
2012年 | 43篇 |
2011年 | 48篇 |
2010年 | 22篇 |
2009年 | 28篇 |
2008年 | 34篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 23篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 23篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 2篇 |
1960年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有741条查询结果,搜索用时 0 毫秒
61.
Srinivasan T Srivastava GK Pathak A Batra S Raj K Singh K Puri SK Kundu B 《Bioorganic & medicinal chemistry letters》2002,12(20):2803-2806
The use of the triterpenoid lupeol as a scaffold for the synthesis of lupeol-based libraries is described. Lupeol was anchored to a solid support (Rink amide/Sieber Amide) through aliphatic dicarboxylic acid moieties, which also served as a site for introducing diversity. The resulting polymer linked 3beta-O (resin-alkanoyl)-lup-20(29)-ene 3 was used to generate key intermediates 3beta-O (resin-alkanoyl)-30-bromo-lup-20(29)-ene 4 and 3beta-O (resin-alkanoyl)-30-amino-lup-20(29)-ene 6 for the generation of libraries based on disubstituted lupeol derivatives. A 96-member library was screened for its in-vitro antimalarial activity against Plasmodium falciparum. 相似文献
62.
Sayantari Ghosh Kamakshi Sureka Bhaswar Ghosh Indrani Bose Joyoti Basu Manikuntala Kundu 《BMC systems biology》2011,5(1):18
Background
A common survival strategy of microorganisms subjected to stress involves the generation of phenotypic heterogeneity in the isogenic microbial population enabling a subset of the population to survive under stress. In a recent study, a mycobacterial population of M. smegmatis was shown to develop phenotypic heterogeneity under nutrient depletion. The observed heterogeneity is in the form of a bimodal distribution of the expression levels of the Green Fluorescent Protein (GFP) as reporter with the gfp fused to the promoter of the rel gene. The stringent response pathway is initiated in the subpopulation with high rel activity. 相似文献63.
Ramachandran Saraswathi Rakhi Pait Chowdhury Sunanda Margrett Williams Payel Ghatak Dipankar Chatterji 《PloS one》2009,4(11)
The Dps (DNA-binding protein from starved cells) proteins from Mycobacterium smegmatis MsDps1 and MsDps2 are both DNA-binding proteins with some differences. While MsDps1 has two oligomeric states, with one of them responsible for DNA binding, MsDps2 has only one DNA-binding oligomeric state. Both the proteins however, show iron-binding activity. The MsDps1 protein has been shown previously to be induced under conditions of starvation and osmotic stress and is regulated by the extra cellular sigma factors σH and σF. We show here, that the second Dps homologue in M. smegmatis, namely MsDps2, is purified in a DNA-bound form and exhibits nucleoid-like structures under the atomic force microscope. It appears that the N-terminal sequence of Dps2 plays a role in nucleoid formation. MsDps2, unlike MsDps1, does not show elevated expression in nutritionally starved or stationary phase conditions; rather its promoter is recognized by RNA polymerase containing σA or σB, under in vitro conditions. We propose that due to the nucleoid-condensing ability, the expression of MsDps2 is tightly regulated inside the cells. 相似文献
64.
Sangeetha Kumaravel Prabaharan Thiruvengetam Kannimuthu Karthick Selvasundarasekar Sam Sankar Arun Karmakar Subrata Kundu 《Biotechnology progress》2021,37(2):e3111
Depolymerization of lignin biomass to its value-added chemicals and fuels is pivotal for achieving the goals for sustainable society, and therefore has acquired key interest among the researchers worldwide. A number of distinct approaches have evolved in literature for the deconstruction of lignin framework to its mixture of complex constituents in recent decades. Among the existing practices, special attention has been devoted for robust site selective chemical transformation in the complex structural frameworks of lignin. Despite the initial challenges over a period of time, oxidation and oxidative cleavage process of aromatic building blocks of lignin biomass toward the fine chemical synthesis and fuel generation has improved substantially. The development has improved in terms of cost effectiveness, milder reaction conditions, and purity of compound individuals. These aforementioned oxidative protocols mainly involve the breaking of C-C and C-O bonds of complex lignin frameworks. More precisely in the line with environmentally friendly greener approach, the catalytic oxidation/oxidative cleavage reactions have received wide spread interest for their mild and selective nature toward the lignin depolymerization. This mini-review aims to provide an overview of recent developments in the field of oxidative depolymerization of lignin under greener and environmentally benign conditions. Also, these oxidation protocols have been discussed in terms of scalability and recyclability as catalysts for different fields of applications. 相似文献
65.
66.
M. Jain A. S. Nandwal B. S. Kundu B. Kumar I. S. Sheoran N. Kumar A. Mann S. Kukreja 《Biologia Plantarum》2006,50(2):303-306
The plants of pigeonpea (Cajanus cajan L.) cv. H77-216 were subjected to moderate [soil moisture content (SMC) = 7.3 ± 0.5 %] and severe (SMC = 4.3 ± 0.5 %) drought
by withholding the irrigation at vegetative stage (45 d after sowing). The control plants were maintained at SMC of 11.0 ±
0.5 %. Half of the stressed plants were re-irrigated and their recovery was studied after 2 d. Leaf water potential, osmotic
potential, and relative water content of leaf and root decreased significantly while a sharp rise in proline and total soluble
sugars contents were noticed. Drought induced a significant increase in 1-aminocyclopropane 1-carboxylic acid (ACC) content
and ACC oxidase activity which caused a considerable increase in ethylene evolution. Malondialdehyde content and relative
stress injury were increased under drought whereas reverse was true for ascorbic acid content. The membrane integrity of roots
decreased during stress and recovered on rehydration. The specific activity of total superoxide dismutase, ascorbate peroxidase,
glutathione reductase, and glutathione transferase decreased to 37 – 78 %, 17 – 62 %, 29 – 36 % and 57 – 79 % at moderate
and severe drought, respectively. The increase in activity of catalase and peroxidase could not overcome the accumulation
of H2O2 content in the roots. 相似文献
67.
Parag Kundu Teo Wei Ling Agata Korecka Yinghui Li Rossana D'Arienzo Ralph M. Bunte Thorsten Berger Velmurugesan Arulampalam Pierre Chambon Tak Wah Mak Walter Wahli Sven Pettersson 《PLoS pathogens》2014,10(1)
To be able to colonize its host, invading Salmonella enterica serovar Typhimurium must disrupt and severely affect host-microbiome homeostasis. Here we report that S. Typhimurium induces acute infectious colitis by inhibiting peroxisome proliferator-activated receptor gamma (PPARγ) expression in intestinal epithelial cells. Interestingly, this PPARγ down-regulation by S. Typhimurium is independent of TLR-4 signaling but triggers a marked elevation of host innate immune response genes, including that encoding the antimicrobial peptide lipocalin-2 (Lcn2). Accumulation of Lcn2 stabilizes the metalloproteinase MMP-9 via extracellular binding, which further aggravates the colitis. Remarkably, when exposed to S. Typhimurium, Lcn2-null mice exhibited a drastic reduction of the colitis and remained protected even at later stages of infection. Our data suggest a mechanism in which S. Typhimurium hijacks the control of host immune response genes such as those encoding PPARγ and Lcn2 to acquire residence in a host, which by evolution has established a symbiotic relation with its microbiome community to prevent pathogen invasion. 相似文献
68.
Subhankar Paul Madhuchhanda Kundu Kali P. Das Saroj Mishra Tapan K. Chaudhuri 《Journal of biological physics》2008,34(6):539-550
Equilibrium unfolding of a 69-kDa monomeric Escherichia coli maltodextrin glucosidase (MalZ) was studied using intrinsic and extrinsic fluorescence spectroscopy. The unfolding transition
of MalZ followed a three-state process, involving the formation of a stable intermediate state having more exposed hydrophobic
surface. It was found that the protein structure can be easily perturbed by low concentration of guanidium hydrochloride (GdnHCl)
and, at a GdnHCl concentration of 2 M, MalZ was denatured completely. The active site of the protein also has been proved
to be sensitive to a low concentration of GdnHCl since MalZ deactivated at 0.5 M GdnHCl completely. The surface hydrophobicity
and ANS-binding site of the protein have been determined to be 150.7 and 0.24, respectively. Perhaps the formation of the
stable unfolding intermediate, having higher surface hydrophobicity, may be one of the reasons for aggregation of MalZ and
its recognition by chaperonin GroEL during the assisted folding pathway. 相似文献
69.
M. I. Oshtrakh A. L. Berkovsky A. Kumar S. Kundu A. V. Vinogradov T. S. Konstantinova V. A. Semionkin 《Biometals》2011,24(3):501-512
A comparative study of oxyhemoglobins from pig, rabbit, normal human and patients with blood system malignant diseases was performed using Mössbauer spectroscopy with a high velocity resolution at 90 K. Mössbauer spectra were fitted with the help of two models: using one quadrupole doublet (model of equivalent iron electronic structure in α- and β-subunits of hemoglobins) and superposition of two quadrupole doublets (model of non-equivalent iron electronic structure in α- and β-subunits of hemoglobins). The results obtained using both models demonstrated small variations of hyperfine parameters that were related to the heme iron state variation in different hemoglobins. These results were compared with structural and functional differences of the hemoglobins investigated. 相似文献
70.