全文获取类型
收费全文 | 418篇 |
免费 | 27篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 17篇 |
2012年 | 39篇 |
2011年 | 39篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 30篇 |
2007年 | 23篇 |
2006年 | 38篇 |
2005年 | 24篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 8篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有445条查询结果,搜索用时 218 毫秒
41.
Flinn B Rothwell C Griffiths R Lägue M DeKoeyer D Sardana R Audy P Goyer C Li XQ Wang-Pruski G Regan S 《Plant molecular biology》2005,59(3):407-433
To help develop an understanding of the genes that govern the developmental characteristics of the potato (Solanum tuberosum), as well as the genes associated with responses to specified pathogens and storage conditions, The Canadian Potato Genome
Project (CPGP) carried out 5′ end sequencing of regular, normalized and full-length cDNA libraries of the Shepody potato cultivar,
generating over 66,600 expressed sequence tags (ESTs). Libraries sequenced represented tuber developmental stages, pathogen-challenged
tubers, as well as leaf, floral developmental stages, suspension cultured cells and roots. All libraries analysed to date
have contributed unique sequences, with the normalized libraries high on the list. In addition, a low molecular weight library
has enhanced the 3′ ends of our sequence assemblies. Using the combined assembly dataset, unique tuber developmental, cold
storage and pathogen-challenged sequences have been identified. A comparison of the ESTs specific to the pathogen-challenged
tuber and foliar libraries revealed minimal overlap between these libraries. Mixed assemblies using over 189,000 potato EST
sequences from CPGP and The Institute for Genomics Research (TIGR) has revealed common sequences, as well as CPGP- and TIGR-unique
sequences.
Electronic Supplementary Material Electronic Supplementary material is available for this article at
and accessible for authorised users. 相似文献
42.
Here we describe, determine the prevalence, and examine the host-specificity of some parasitic nematode microfilariae in selected bird species from West and Central Africa. We used microscopy to determine the prevalence of microfilariae in 969 host individuals representing 121 rainforest bird species from Cameroon, Côte d’Ivoire and Equatorial Guinea. Thirteen (11%) of these potential host species harboured microfilariae, and 35 individuals (3.6%) were infected. From the 35 infected individuals, we identified eight distinct morphological microfilarial forms. Sixteen of the 35 infected individuals were of one host species, the Fire-crested Alethe (Alethe diademata), at a prevalence rate of 62%. To examine host and geographical specificity, we sequenced a portion of the LSU rDNA gene from representative microfilariae drawn from different hosts and collecting locations. Identical sequences of the nematode LSU rDNA gene were found in A. diademata collected from locations in Côte d’Ivoire and Equatorial Guinea, locations separated by the Dahomey Gap and associated with different hypothesized refugial areas. In contrast, several other bird species collected at the same sites harboured different microfilaria lineages. We sequenced the mitochondrial ATP synthase genes of the host species A. diademata, and found a 5.4% sequence divergence between the birds sampled in Côte d’Ivoire, and those from Cameroon. Thus, despite this split between the two populations, they harbour microfilariae with identical lineages. These data provide evidence that the microfilariae found in A. diademata may be highly host specific. This apparent specificity may have important implications for the evolutionary and ecological interactions between parasitic nematodes and their avian hosts. 相似文献
43.
Das B Ramu R Venkateswarlu K Rao YK Reddy MR Ramakrishna KV Harakishore K Murty US 《化学与生物多样性》2006,3(2):175-179
Two new ent-clerodane-type diterpenoids, compounds 1 and 2, were isolated from the aerial parts of Pulicaria wightiana, together with three known constituents. Their structures were established based on spectroscopic data, and their antibacterial activities were evaluated (Table 2). 相似文献
44.
Hua-Poo Su Youwei Yan G. Sridhar Prasad Robert F. Smith Christopher L. Daniels Pravien D. Abeywickrema John C. Reid H. Marie Loughran Maria Kornienko Sujata Sharma Jay A. Grobler Bei Xu Vinod Sardana Timothy J. Allison Peter D. Williams Paul L. Darke Daria J. Hazuda Sanjeev Munshi 《Journal of virology》2010,84(15):7625-7633
45.
Batish DR Singh HP Setia N Kaur S Kohli RK 《Zeitschrift für Naturforschung. C, Journal of biosciences》2006,61(9-10):709-714
BOA (2-benzoxazolinone) is a potent phytotoxin present in several graminaceous crops such as rye, maize and wheat. Due to its wide range of phytotoxicity, it is considered as a potential pesticide. A study was conducted to explore the impact of BOA on the radicle and plumule elongation of mung bean (Phaseolus aureus) and associated changes in the macromolecular content - proteins and carbohydrates - and activities of enzymes like amylases, proteases, polyphenol oxidases and peroxidases. BOA significantly reduced the radicle and plumule length of P. aureus, and the contents of proteins and carbohydrates in both root and leaf tissue. On the other hand, activities of hydrolytic enzymes - proteases, amylases, polyphenol oxidases and peroxidases - increased substantially in both root and leaf tissue of P. aureus upon BOA exposure. This indicated that BOA treatment induced stress in P. aureus and enhanced enzyme activities to counter the induced stress and continue the growth. In other words, BOA-induced stress altered the plant biochemical status and related enzyme activities resulting in increased metabolism that serves to provide protection against cellular injury. Such studies providing information about the biomolecular content and enzymatic activities in response to natural products serve as clues for furtherance of knowledge about the modes of action of natural compounds of commercial interest. 相似文献
46.
Vijayakumar S Merkx-Jacques A Ratnayake DB Gryski I Obhi RK Houle S Dozois CM Creuzenet C 《The Journal of biological chemistry》2006,281(38):27733-27743
Campylobacter jejuni produces glycoproteins that are essential for virulence. These glycoproteins carry diacetamidobacillosamine (DAB), a sugar that is not found in humans. Hence, the enzymes responsible for DAB synthesis represent potential therapeutic targets. We describe the biochemical characterization of Cj1121c, a putative aminotransferase encoded by the general protein glycosylation locus, to assess its role in DAB biosynthesis. By using overexpressed and affinity-purified enzyme, we demonstrate that Cj1121c has pyridoxal phosphate- and glutamate-dependent UDP-4-keto-6-deoxy-GlcNAc C-4 transaminase activity and produces UDP-4-amino-4,6-dideoxy-GlcNAc. This is consistent with a role in DAB biosynthesis and distinguishes Cj1121c from Cj1294, a homologous UDP-2-acetamido-2,6-dideoxy-beta-l-arabino-4-hexulose C-4 aminotransferase that we characterized previously. We show that Cj1121c can also use this 4-keto-arabino sugar indirectly as a substrate, that Cj1121c and Cj1294 are active simultaneously in C. jejuni, and that the activity of Cj1121c is preponderant under standard growth conditions. Kinetic data indicate that Cj1121c has a slightly higher catalytic efficiency than Cj1294 with regard to the 4-keto-arabino substrate. By site-directed mutagenesis, we show that residues Glu-158 and Leu-131 are not essential for catalysis or for substrate specificity contrary to expectations. We further demonstrate that a cj1121c knock-out mutant is impaired for flagella-mediated motility, for invasion of intestinal epithelial cells, and for persistence in the chicken intestine, clearly demonstrating that Cj1121c is essential for host colonization and virulence. Finally, we show that cj1121c is necessary for protein glycosylation by lectin Western blotting. Collectively, these results validate Cj1121c as a promising drug target and provide the means to assay for inhibitors. 相似文献
47.
Ravinder K. Kohli Daizy R. Batish H. P. Singh Kuldip S. Dogra 《Biological invasions》2006,8(7):1501-1510
Invasive weeds have threatened the integrity of ecosystems throughout the world. They affect not only the species diversity
of native areas but also their biological integrity. In India, a number of invasive exotic weeds have been reported but some
viz. Parthenium hysterophorus, Lantana camara and Ageratum conyzoides, especially those from tropical America are troublesome and have caused adverse ecological, economic and social impact. These
weeds can be seen growing in different landscapes but are luxuriantly localized in unattended forests and cultivated areas.
Parthenium hysterophorus (Asteraceae, commonly known as congress grass) is perhaps the most troublesome and noxious weed of urban and rural India.
Besides rapidly colonizing areas replacing the native vegetation, it is also known to cause a number of human health problems
such as skin allergy, rhinitis and irritation to eyes of the residents in the vicinity. Likewise, it causes fodder scarcity
in addition to being unpalatable and toxic to livestock. Lantana camara (Verbenaceae), another serious tropical American pest, has encroached upon large areas of land, especially the forests where
it has virtually replaced the forest floor vegetation and reduced tree growth. Also because of its bushy and spreading type
of growth it obstructs forest operations. The third weed, Ageratum conyzoides (Asteraceae, Billy goat weed) has invaded agricultural fields. It interferes with crops and causes yield reductions of major
staple crops of India. When it invades rangeland areas, it out competes native grasses causing scarcity of fodder. These weeds
have similar growth strategies such as fast growth rates, short life-cycles, greater reproductive potential, high competitive
abilities and allelopathy that make them successful invaders of native habitats. Mechanical, chemical, biological and cultural
control tactics have failed individually, though integrated approaches combining all these approaches along with community
participation and proper land management have been relatively successful. This paper presents various aspects of biology,
ecology, hazards and control measures of these weeds. 相似文献
48.
Singh S Ahmad R Mathur D Sagar RK Krishana B 《Indian journal of experimental biology》2006,44(9):699-704
Brain derived neurotrophic factor (BDNF) has been shown to exert trophic effects on dopaminergic neurons against 6-hydroxydopamine (6-OHDA) in young rat. Since the degeneration of substantia nigra dopaminergic neurons that occurs in Parkinson's disease is more often than not confined to elderly individuals, it is of interest to determine whether the effects of BDNF against 6 hydroxydopamine (6-OHDA) in young rats can be extended to aged animals. 6-hydroxydopamine was stereotaxically injected into the striatum of young (3-months) and aged (24-months) rats, which were treated two hours earlier with BDNF. 6-OHDA results in almost complete destruction of substantia nigra pars compacta dopaminergic neurons. BDNF injection significantly changed apomorphine induced rotations from 132 +/- 15 to 181 +/- 10, staircase test from 73 +/- 2% to 61 +/- 3%, initiation time from 7 +/- 2 to 12 +/- 1 sec, and disengage time from 80 +/- 7 to 90 +/- 5 sec in young and aged animals, respectively. It is concluded that BDNF causes the limited behavior recovery of striatal DA systems from 6-OHDA toxicity in aged animals. 相似文献
49.
The therapeutic success of biological agents, especially the tumour necrosis factor (TNF) inhibitors, has opened a new chapter in the book of therapies for rheumatoid arthritis. Nevertheless, more than 50% of patients may not respond by > 50% improvement. New compounds have recently entered the treatment arena. One of these is rituximab, which depletes B cells, and another, abatacept, interferes with T-cell co-stimulation. However, although these agents may be effective in a number of patients who fail to respond to TNF blockade, they only rarely induce remission and overall 50% response rates do not exceed those with the TNF inhibitors. Among the major proinflammatory cytokines, IL-6 plays a pleiotropic role both in terms of activating the inflammatory response and osteoclastogenesis. Here, we review recent phase II trials of tocilizumab, a humanized anti-IL-6 receptor antibody that achieves a significant therapeutic response rate. 相似文献
50.
The development of new therapeutic leads against leishmaniasis relies primarily on screening of a large number of compounds on multiplication of clinically irrelevant transgenic promastigotes. The advent of the successful in vitro culture of axenic amastigotes allows the development of transgenic axenic amastigotes as a primary screen which can test compounds in a high throughput mode like promastigotes, still representative of the clinically relevant mammalian amastigotes stage. The present study reports the development of luciferase-tagged axenic amastigotes of Leishmania donovani, the causative agent of Indian Kala-azar, for in vitro drug screening. Luciferase expressing promastigotes were transformed to axenic amastigotes at a low pH and high temperature without the loss of luciferase expression. As compared to transgenic promastigotes, the luciferase expressing axenic amastigotes exhibited more sensitivity to antileishmanial drugs, particularly to pentavalent antimony (~2.8-fold) and also to the test compounds. Hence, the developed luciferase expressing axenic amastigotes make an ideal choice for high throughput drug screening for antileishmanial compounds. 相似文献