全文获取类型
收费全文 | 318篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
347篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 14篇 |
2021年 | 17篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 28篇 |
2013年 | 28篇 |
2012年 | 22篇 |
2011年 | 31篇 |
2010年 | 12篇 |
2009年 | 14篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有347条查询结果,搜索用时 0 毫秒
281.
Ullah Najeeb Ling Xu Zammurad I. Ahmed Muhammad Rasheed Ghulam Jilani Muhammad S. Naeem Weiqi Shen Weijun Zhou 《Acta Physiologiae Plantarum》2011,33(2):481-488
Increased ultraviolet radiations intruding on the earth pose a serious threat to the unadapted plants. Due to the ecological
and economic significance of mat rush (Juncus effusus L.), an in vitro experiment was conducted to unveil the toxic effects of ultraviolet radiation (UV-C) on its physiology and
ultrastructure. The basal culm segments of plant were used for in vitro treatments of UV-C with different exposure times (15,
30 and 45 min). The treated segments were first transferred to 1/2 strength MS media and then shifted to soil-perlite mixture
for further growth. With increasing exposure time to UV-C, there was significant reduction in plant growth and biomass, and
increased activities of antioxidant enzymes. Physiological and ultrastructural alterations were observed in the shoots of
UV-treated plants. These plants exhibited significant reduction in chlorophyll contents and noticeable modifications at the
ultra-cellular levels. Cell and chloroplast size reduced greatly, and there was appearance of higher amounts of plastoglobuli
in chloroplasts resulting in disruption of thylakoid integrity. The functional and ultrastructural alterations in the stressed
plants suggest a potential hazard of UV-C radiation on this aquatic flora and thus the ecosystem. The study further explores
that UV-C radiations trigger these modifications mainly by damaging the chloroplast. 相似文献
282.
283.
Qazi Rida-e-Maria Naeem Nadia Khan Irfan Qadeer Quratulain Shaheen Farzana Salim Asmat 《Molecular and cellular biochemistry》2020,465(1-2):27-36
Molecular and Cellular Biochemistry - Polo-like kinase 1 (Plk1) is a mitotic serine/threonine kinase implicated in spindle formation and cytokinesis in mammalian cells. Here, purified Plk1 was... 相似文献
284.
Sanna Koskiniemi Henry S. Gibbons Linus Sandegren Naeem Anwar Gary Ouellette Stacey Broomall Mark Karavis Paul McGregor Alvin Liem Ed Fochler Lauren McNew Carolyn Nicole Rosenzweig Mikael Rhen Evan W. Skowronski Dan I. Andersson 《PloS one》2013,8(7)
How pathogenic bacteria adapt and evolve in the complex and variable environment of the host remains a largely unresolved question. Here we have used whole genome sequencing of Salmonella enterica serovar Typhimurium LT2 populations serially passaged in mice to identify mutations that adapt bacteria to systemic growth in mice. We found unique pathoadaptive mutations in two global regulators, phoQ and stpA, which increase the competitive indexes of the bacteria 3- to 5-fold. Also, all mouse-adapted lineages had changed the orientation of the hin invertable element, resulting in production of a FliC type of flagellum. Competition experiments in mice with locked flagellum mutants showed that strains expressing the FliC type of flagellum had a 5-fold increase in competitive index as compared to those expressing FljB type flagellum. Combination of the flagellum cassette inversion with the stpA mutation increased competitive indexes up to 20-fold. These experiments show that Salmonella can rapidly adapt to a mouse environment by acquiring a few mutations of moderate individual effect that when combined confer substantial increases in growth. 相似文献
285.
Yogesh S. Sanghvi Naeem B. Hanna Steven B. Larson Roland K. Robins Ganapathi R. Revankar 《Nucleosides, nucleotides & nucleic acids》2013,32(4):761-774
Abstract A synthesis of 1-(2,3-dideoxy-β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (2′,3′-dideoxyribavirin, ddR) is described. Glycosylation of the sodium salt of 1,2,4-triazole-3-carbonitrile (5) with 1-chloro-2-deoxy-3,5-di-0-p-toluoyl-α-D-erythro-pentofuranose (1) gave exclusively the corresponding N-1 glycosyl derivative with β-anomeric configuration (6), which on ammonolysis provided a convenient synthesis of 2′-deoxyribavirin (7). Similar glycosylation of the sodium salt of methyl 1,2,4-triazole-3-carboxylate (2) with 1 gave a mixture of corresponding N-1 and N-2 glycosyl derivatives (3) and (4), respectively. Ammonolysis of 3 furnished yet another route to 7. A four-step deoxygenation procedure using imidazolylthiocarbonylation of the 3′-hydroxy group of 5′-0-toluoyl derivative (9a) gave ddR (11). The structure of 11 was proven by single crystal X-ray studies. In a preliminary in vitro study ddR was found to be inactive against HIV retrovirus. 相似文献
286.
Abstract
The ability of a polypeptide to fold into a unique, functional, and three-dimensional structure depends on the intrinsic properties of the amino acid sequence, function of the molecular chaperones, proteins, and enzymes. Every polypeptide has a finite tendency to misfold and this forms the darker side of the protein world. Partially folded and misfolded proteins that escape the cellular quality control mechanism have the high tendency to form inter-molecular hydrogen bonding between the same protein molecules resulting in aggregation. This review summarizes the underlying and universal mechanism of protein folding. It also deals with the factors responsible for protein misfolding and aggregation. This article describes some of the consequences of such behavior particularly in the context of neurodegenerative conformational diseases such as Alzheimer’s, Parkinson’s, Huntington’s, amyotrophic lateral sclerosis and other non-neurodegenerative conformational diseases such as cancer and cystic fibrosis etc. This will encourage a more proactive approach to the early diagnosis of conformational diseases and nutritional counseling for patients. 相似文献287.
Iqbal F Fatima M Shahnawaz S Naeem M Shaikh R Ali M Shaikh A Aktas M Ali M 《Parasite (Paris, France)》2011,18(3):229-234
Babesiosis is a parasitic infection due to the multiplication of tick borne parasite, Babesia sp., in erythrocytes of host, which includes a wide variety of vertebrates including small ruminants causing decreased livestock output and hence economic losses. The objective of the present study was to establish a PCR based method for the detection of Babesia sp. in small ruminant population in Southern Punjab and to determine the risk factors involve in the spread of babesiosis. A total of 107 blood samples were collected from 40 sheep and 67 goats in seven districts of Southern Punjab from randomly selected herds. Data on the characteristics of the animals and the herd were collected through questionnaires. 36 blood samples (34% of total) produced the DNA fragment specific for 18S rRNA gene of Babesia sp., by PCR amplification, of which 20 were sheep and 16 were goats. Samples from all seven district contained Babesia positive samples and prevalence varied between 18 to 68%. It was observed that male animals (P = 0.009) and young animals under one year of age (P = 0.01) were more prone to the parasite. It was observed that herds consist of more than 15 animals (P = 0.007), composed of mixed species of small ruminants (P = 0.022), associated with dogs (P = 0.003) and dogs having ticks on their bodies (P = 0.011) were among the major risk factors for the spread of babesiosis in small ruminants. 相似文献
288.
Faheem Shah Tasneem Gul Kazi Naeem Ullah Hassan Imran Afridi 《Biological trace element research》2013,153(1-3):134-140
In present study, lead (Pb) level in biological samples of children with physiological disorders (liver, bone, and gastrointestinal; age ranged 1–10 years) have been assessed. For comparison purpose, age-matched healthy children were also selected. Cloud point extraction (CPE) was employed for preconcentration of Pb in acid-digested biological samples prior to its determination by flame atomic absorption spectrometry (FAAS). Dithizone (diphenylthiocarbazone) and nonionic surfactant Triton X-114 (TX-114) were used as complexing reagent and extractant, respectively. The effects of several experimental variables on proposed CPE were evaluated. Under the optimum experimental conditions, the observed detection limit (LOD) and the enhancement factor (EF) were 0.08 μg L?1 and 53, respectively. Relative standard deviation (RSD) of 10 μg L?1 Pb was 3.4 %. It was observed that children with liver-, bone-, and gastrointestinal-related disorders had three- to fourfold higher Pb level in blood and scalp hair samples. 相似文献
289.
Marissa A. LeBlanc Lynette S. Penney Daniel Gaston Yuhao Shi Erika Aberg Mathew Nightingale Haiyan Jiang Roxanne M. Gillett Somayyeh Fahiminiya Christine Macgillivray Ellen P. Wood Philip D. Acott M. Naeem Khan Mark E. Samuels Jacek Majewski Andrew Orr Christopher R. McMaster Karen Bedard 《Human genetics》2013,132(11):1223-1234
Pediatric intracranial calcification may be caused by inherited or acquired factors. We describe the identification of a novel rearrangement in which a downstream pseudogene translocates into exon 9 of OCLN, resulting in band-like brain calcification and advanced chronic kidney disease in early childhood. SNP genotyping and read-depth variation from whole exome sequencing initially pointed to a mutation in the OCLN gene. The high degree of identity between OCLN and two pseudogenes required a combination of multiplex ligation-dependent probe amplification, PCR, and Sanger sequencing to identify the genomic rearrangement that was the underlying genetic cause of the disease. Mutations in exon 3, or at the 5–6 intron splice site, of OCLN have been reported to cause brain calcification and polymicrogyria with no evidence of extra-cranial phenotypes. Of the OCLN splice variants described, all make use of exon 9, while OCLN variants that use exons 3, 5, and 6 are tissue specific. The genetic rearrangement we identified in exon 9 provides a plausible explanation for the expanded clinical phenotype observed in our individuals. Furthermore, the lack of polymicrogyria associated with the rearrangement of OCLN in our patients extends the range of cranial defects that can be observed due to OCLN mutations. 相似文献
290.