全文获取类型
收费全文 | 204篇 |
免费 | 16篇 |
专业分类
220篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 23篇 |
2013年 | 19篇 |
2012年 | 15篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1984年 | 1篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 15 毫秒
141.
Identification of arginine 331 as an important active site residue in the class II fructose-1,6-bisphosphate aldolase of Escherichia coli. 下载免费PDF全文
S. Qamar K. Marsh A. Berry 《Protein science : a publication of the Protein Society》1996,5(1):154-161
Treatment of the Class II fructose-1,6-bisphosphate aldolase of Escherichia coli with the arginine-specific alpha-dicarbonyl reagents, butanedione or phenylglyoxal, results in inactivation of the enzyme. The enzyme is protected from inactivation by the substrate, fructose 1,6-bisphosphate, or by inorganic phosphate. Modification with [7-14C] phenylglyoxal in the absence of substrate demonstrates that enzyme activity is abolished by the incorporation of approximately 2 moles of reagent per mole of enzyme. Sequence alignment of the eight known Class II FBP-aldolases shows that only one arginine residue is conserved in all the known sequences. This residue, Arg-331, was mutated to either alanine or glutamic acid. The mutant enzymes were much less susceptible to inactivation by phenylglyoxal. Measurement of the steady-state kinetic parameters revealed that mutation of Arg-331 dramatically increased the K(m) for fructose 1,6-bisphosphate. Comparatively small differences in the inhibitor constant Ki for dihydroxyacetone phosphate or its analogue, 2-phosphoglycolate, were found between the wild-type and mutant enzymes. In contrast, the mutation caused large changes in the kinetic parameters when glyceraldehyde 3-phosphate was used as an inhibitor. Kinetic analysis of the oxidation of the carbanionic aldolase-substrate intermediate of the reaction by hexacyanoferrate (III) revealed that the K(m) for dihydroxyacetone phosphate was again unaffected, whereas that for fructose 1,6-bisphosphate was dramatically increased. Taken together, these results show that Arg-331 is critically involved in the binding of fructose bisphosphate by the enzyme and demonstrate that it interacts with the C-6 phosphate group of the substrate. 相似文献
142.
Tharmalingam Ramesh Riddhika Kalle Kalyanasundaram Sankar Qamar Qureshi 《European Journal of Wildlife Research》2013,59(2):271-280
Ecology of Asia's smallest ungulate, the Indian chevrotain or mouse deer (Moschiola indica), has been poorly assessed. We used camera-trapping data to investigate habitat use of mouse deer in Mudumalai Tiger Reserve. Presence/absence data, collected under a systematic sampling framework, were used to test a priori hypotheses incorporating covariates believed to influence mouse deer occurrence and detection. The average occupancy rate of mouse deer in the study area was 0.56 (SE?=?0.22) with a low detection probability (0.29, SE?=?0.14). Model selection indicated that presence of moist bamboo brakes positively influenced while percent leaf litter negatively influenced mouse deer occupancy. Placement of camera-traps along narrow trails positively influenced detection probability of mouse deer. Future conservation efforts in India should focus on preservation of bamboo vegetation and dense forest cover which provide refuge for the mouse deer. Our results illustrate that occupancy can be suitable for monitoring elusive, forest dwelling, small ungulates; however, caution is needed when applying these models on small ranging species, as our study identifies the limitations in our survey design and its improvement for future monitoring which are applicable for similar-sized species across a range of habitats. 相似文献
143.
Muhammad Tahir ul Qamar Arooj Mumtaz Rabbia Naseem Amna Ali Tabeer Fatima Tehreem Jabbar Zubair Ahmad Usman Ali Ashfaq 《Bioinformation》2014,10(7):460-465
Dengue infection has turned into a serious health concern globally due to its high morbidity rate and a high possibility of increase
in its mortality rate on the account of unavailability of any proper treatment for severe dengue infection. The situation demands an
urgent development of efficient and practicable treatment to deal with Dengue virus (DENV). Flavonoids, a class of
phytochemicals present in medicinal plants, possess anti-viral activity and can be strong drug candidates against viruses. NS1
glycoprotein of Dengue virus is involved in its RNA replication and can be a strong target for screening of drugs against this virus.
Current study focuses on the identification of flavonoids which can block Asn-130 glycosylation site of Dengue virus NS1 to inhibit
viral replication as glycosylation of NS1 is required for its biological functioning. Molecular docking approach was used in this
study and the results revealed that flavonoids have strong potential interactions with active site of NS1. Six flavonoids
(Deoxycalyxin A; 3,5,7,3'',4''-pentahydroxyflavonol-3-O-beta-D-galactopyranoside; (3R)-3'',8-Dihydroxyvestitol; Sanggenon O;
Epigallocatechin gallate; Chamaejasmin) blocked the Asn-130 glycosylation site of NS1 and could be able to inhibit the viral
replication. It can be concluded from this study that these flavonoids could serve as antiviral drugs for dengue infections. Further
in-vitro analyses are required to confirm their efficacy and to evaluate their drug potency. 相似文献
144.
Tahir ul Qamar Arooj Mumtaz Usman Ali Ashfaq Samia Azhar Tabeer Fatima Muhammad Hassan Syed Sajid Hussain Waheed Akram Sobia Idrees 《Bioinformation》2014,10(3):115-118
Dengue virus NS2/NS3 protease because of its ability to cleave viral proteins is considered as an attractive target to screen antiviral
agents. Medicinal plants contain a variety of phytochemicals that can be used as drug against different diseases and infections.
Therefore, this study was designed to uncover possible phytochemical of different classes (Aromatic, Carbohydrates, Lignin,
Saponins, Steroids, Tannins, Terpenoids, Xanthones) that could be used as inhibitors against the NS2B/NS3 protease of DENV.
With the help of molecular docking, Garcinia phytochemicals found to be bound deeply inside the active site of DENV NS2B/NS3
protease among all tested phytochemicals and had interactions with catalytic triad (His51, Asp75, Ser135). Thus, it can be
concluded from the study that these Gracinia phytochemicals could serve as important inhibitors to inhibit the viral replication
inside the host cell. Further in-vitro investigations require confirming their efficacy. 相似文献
145.
Humaira Ayub Shazia Micheal Farah Akhtar Muhammad Imran Khan Shaheena Bashir Nadia K. Waheed Mahmood Ali Frederieke E. Schoenmaker-Koller Sobia Shafique Raheel Qamar Anneke I. den Hollander 《PloS one》2014,9(8)
Recently an association was observed between alleles in genes of the unfolded protein response pathway and primary open angle glaucoma (POAG). The goal of the current study is to investigate the role of these two genes, protein disulphide isomerase A member 5 (PDIA5) and baculoviral IAP repeat containing 6 (BIRC6), in different forms of glaucoma. 278 patients with POAG, 132 patients with primary angle closure glaucoma (PACG) and 135 patients with pseudoexfoliative glaucoma (PEXG) were genotyped for single nucleotide polymorphisms (SNPs) rs11720822 in PDIA5 and 471 POAG, 184 PACG and 218 PEXG patients were genotyped for rs2754511 in BIRC6. Genotyping was done by allelic discrimination PCR, and genotype and allele frequencies were calculated. Logistic regression analyses were performed using R software to determine the association of these SNPs with glaucoma. The allele and genotype frequencies of rs11720822 in PDIA5 were not associated with POAG, PACG or PEXG. The TT genotype of rs2754511 in BIRC6 was found to be protective for PEXG (p = 0.05, OR 0.42 [0.22–0.81]) in the Pakistani population, but not for POAG or PACG. This study did not confirm a previously reported association of risk alleles in PDIA5 and BIRC6 with POAG, but did demonstrate a protective role of the T allele of rs2754511 in the BIRC6 gene in PEXG. This supports a role for the unfolded protein response pathway and regulation of apoptotic cell death in the pathogenesis of PEXG. 相似文献
146.
Summary With limited evidence linking Australia's Murray‐Darling Basin fish species and flooding, this study assessed annual variation in abundance and recruitment levels of a small‐bodied, threatened floodplain species, the Southern Pygmy Perch (Nannoperca australis), in floodplain habitats (creeks, lakes and wetlands) in the Barmah‐Millewa Forest, Murray River, Australia. Spring and summer sampling over a 5‐year period encompassed large hydrological variation, including 1 year of extended floodplain inundation which was largely driven by an environmental water release, and 2 years of severe regional drought. Recruitment and dispersal of Southern Pygmy Perch significantly increased during the floodplain inundation event compared with the other examined years. This study provides valuable support for an environmental water allocation benefiting a native species, and explores the link between flooding and its advantages to native fish. This suggests that the reduced flooding frequency and magnitude as a result of river regulation may well be a major contributing factor in the species’ decline in the Murray‐Darling Basin. 相似文献
147.
Organisms, in nature, are often subjected to multiple stressors, both biotic and abiotic. Temperature and starvation are among the main stressors experienced by organisms in their developmental cycle and the responses to these stressors may share signaling pathways, which affects the way these responses are manifested. Temperature is a major factor governing the performance of ectothermic organisms in ecosystems worldwide and, therefore, the thermal tolerance is a central issue in the thermobiology of these organisms. Here, we investigated the effects of starvation as well as mild heat and cold shocks on the thermal tolerance of the larvae of silkworm, Bombyx mori (Linnaeus). Starvation acted as a meaningful or positive stressor as it improved cold tolerance, measured as chill coma recovery time (CCRT), but, at the same time, it acted as a negative stressor and impaired the heat tolerance, measured as heat knockdown time (HKT). In the case of heat tolerance, starvation negated the positive effects of both mild cold as well as mild heat shocks and thus indicated the existence of trade-off between these stressors. Both mild heat and cold shocks improved the thermal tolerance, but the effects were more prominent when the indices were measured in response to a stressor of same type, i.e., a mild cold shock improved the cold tolerance more than the heat tolerance and vice versa. This improvement in thermal tolerance by both mild heat as well as cold shocks indicated the possibility of cross-tolerance between these stressors. 相似文献
148.
An Tingting Gao Yamin Kuang Qiqiang Wu Yujie Zaman Qamar uz Zhang Yi Xu Bingcheng Chen Yinglong 《Plant and Soil》2022,476(1-2):117-131
Plant and Soil - Cadmium (Cd) contamination is a serious threat to plants and humans. Silicon (Si) was reported to have some alleviative effects on Cd stress in plants. However, whether Si... 相似文献
149.
Pseudomonas fluorescens CHA0 produces enantio-pyochelin, the optical antipode of the Pseudomonas aeruginosa siderophore pyochelin 总被引:1,自引:0,他引:1
Youard ZA Mislin GL Majcherczyk PA Schalk IJ Reimmann C 《The Journal of biological chemistry》2007,282(49):35546-35553
The siderophore pyochelin is made by a thiotemplate mechanism from salicylate and two molecules of cysteine. In Pseudomonas aeruginosa, the first cysteine residue is converted to its D-isoform during thiazoline ring formation whereas the second cysteine remains in its L-configuration, thus determining the stereochemistry of the two interconvertible pyochelin diastereoisomers as 4'R, 2'R, 4'R (pyochelin I) and 4'R, 2'S, 4'R (pyochelin II). Pseudomonas fluorescens CHA0 was found to make a different stereoisomeric mixture, which promoted growth under iron limitation in strain CHA0 and induced the expression of its biosynthetic genes, but was not recognized as a siderophore and signaling molecule by P. aeruginosa. Reciprocally, pyochelin promoted growth and induced pyochelin gene expression in P. aeruginosa, but was not functional in P. fluorescens. The structure of the CHA0 siderophore was determined by mass spectrometry, thin-layer chromatography, NMR, polarimetry, and chiral HPLC as enantio-pyochelin, the optical antipode of the P. aeruginosa siderophore pyochelin. Enantio-pyochelin was chemically synthesized and confirmed to be active in CHA0. Its potential biosynthetic pathway in CHA0 is discussed. 相似文献