全文获取类型
收费全文 | 793篇 |
免费 | 56篇 |
国内免费 | 1篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 40篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 54篇 |
2017年 | 33篇 |
2016年 | 41篇 |
2015年 | 50篇 |
2014年 | 47篇 |
2013年 | 43篇 |
2012年 | 51篇 |
2011年 | 86篇 |
2010年 | 31篇 |
2009年 | 32篇 |
2008年 | 38篇 |
2007年 | 21篇 |
2006年 | 25篇 |
2005年 | 24篇 |
2004年 | 29篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有850条查询结果,搜索用时 31 毫秒
791.
Singhal Rajesh Kumar Jatav Hanuman Singh Aftab Tariq Pandey Saurabh Mishra Udit Nandan Chauhan Jyoti Chand Subhash Indu Saha Debanjana Dadarwal Basant Kumar Chandra Kailash Khan Mudasser Ahmed Rajput Vishnu D. Minkina Tatiana Narayana Eetela Sathya Sharma Manoj Kumar Ahmed Shahid 《Journal of Plant Growth Regulation》2021,40(6):2303-2328
Journal of Plant Growth Regulation - Nitric oxide (NO) is a free-radical gasotransmitter signaling molecule associated with a varied spectrum of signal transduction pathways linked to inducing... 相似文献
792.
Muhammad Umar Khayam Sahibzada Muhammad Zahoor Abdul Sadiq Fazl ur Rehman Amal M. Al-Mohaimeed Muhammad Shahid Sumaira Naz Riaz Ullah 《Saudi Journal of Biological Sciences》2021,28(1):327-332
The study was devised to prepare berberine nanoparticles by anti-solvent precipitation method and were assessed for their hepatoprotective effect in Male Sprague-Dawley rats against carbon tetrachloride. The pharmacokinetic parameters of the prepared nanoparticles and berberine were evaluated in rabbits. Histopathological studies and blood biochemical analyses were carried out to evaluate the role of both forms of berberine in the experimental animals. Substantial improvement in the liver function test enzymes levels and liver histopathology were achieved in the animals treated with berberine nanoparticles in comparison to the unprocessed berberine whereas, pharmacokinetic parameters for nanoform of berberine were about 3.97 and 3.88 folds higher than that of the unprocessed berberine. The study revealed that the reduction of berberine particle size to nano range improved pharmacokinetic parameters in rabbits. The nano berberine provided better liver protection in experimental rats and high berberine blood concentration. Thus, better hepatoprotective and pharmacokinetics effects were observed for the nano form in comparison to unprocessed form. 相似文献
793.
Jeganathan Pandiyan Shahid Mahboob Marimuthu Govindarajan Khalid A. Al-Ghanim Zubair Ahmed Norah Al-Mulhm Rajendran Jagadheesan Kaliyamoorthy Krishnappa 《Saudi Journal of Biological Sciences》2021,28(2):1218-1225
Pollution is severely threatening the wetland habitats. Heavy metals are one among of the major pollutants in wetland habitats. The cadmium (Cd), copper (Cu), chromium (Cr), cobalt (Co), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn), were assessed in the water, sediment, benthic species (polychaetes, mollusc and crustaceans), prawn and fishes. The assessment of heavy metals was done by using double-beam Atomic Absorption Spectrophotometer (AAS). The Hg, Cr and Co were greater in sediment, Ni and Cd were higher in polychaetes and molluscs respectively. However, the Cu and Pb greater in crabs and the Zinc was greater in fishes. The concentration of metals showed significant differences among the various sources examined (P < 0.05) except Cr (P > 0.05). The inter-correlational analysis among the metals assessed from the various sources showed that the Cr and Pb not correlated among the eight metals examined. However, the Cu and Co were correlated with Hg (r = 0.307) and (r = 0.788) respectively. The nickel was correlated with Hg (r = 0.367), Cu (r = 0.362) and Co (r = 0.432). The Zinc was correlated with the Cd (r = 0.331) and Hg (r = 0.737). However, correlation of metals among the different sources shown that the metals of polychaetes correlated with sediment r = 0.637, the metals of crabs correlated with the sediment and polychaetes r = 0.630 and r = 842 respectively, the metals of molluscs was also correlated with sediment (r = 0.636), polychaetes (r = 0.889) and crabs (r = 0.894). In addition to that the metals of prawns was correlated with the polychaetes (r = 839), crabs (r = 0.628) and molluscs (r = 0.634). The metals of fishes correlated with polychaetes (r = 0.529), crabs (r = 0.710), molluscs (r = 0.493) and prawns (r = 0.593). Indeed the multiple regression model explained that the metals of sediments influence the accumulation of metals in biotic species such as polychaetes, molluscs, crustaceans, prawns and fishes with 84% (F = 21.079; p < 0.001).The order of the heavy metals in the water, sediment and biotic species was Hg > Pb > Ni > Cr > Zn > Co > Cu > Cd. The study found that the level of heavy metals at various sources in the sanctuary is showing considerable warning and the sanctuary is required intensive assessment on various aspects of pollution since the Point Calimere Wildlife Sanctuary is supporting several species of migratory and endangered shorebirds seasonally. 相似文献
794.
Tayyaba Huma Arooma Maryam Shahid ur Rehman Muhammad Tahir ul qamar Tayyaba Shaheen Asma Haque Bushra Shaheen 《Bioinformation》2014,10(7):443-448
Alpha amylase family is generally defined as a group of enzymes that can hydrolyse and transglycosylase α-(1, 4) or α-(1, 6)
glycosidic bonds along with the preservation of anomeric configuration. For the comparative analysis of alpha amylase family,
nucleotide sequences of seven thermo stable organisms of Kingdom Archea i.e. Pyrococcus furiosus (100-105°C), Kingdom
Prokaryotes i.e. Bacillus licheniformis (90-95°C), Geobacillus stearothermophilus (75°C), Bacillus amyloliquefaciens (72°C), Bacillus subtilis
(70°C) and Bacillus KSM K38 (55°C) and Eukaryotes i.e. Aspergillus oryzae (60°C) were selected from NCBI. Primary structure
composition analysis and Conserved sequence analysis were conducted through Bio Edit tools. Results from BioEdit shown only
three conserved regions of base pairs and least similarity in MSA of the above mentioned alpha amylases. In Mega 5.1 Phylogeny
of thermo stable alpha amylases of Kingdom Archea, Prokaryotes and Eukaryote was handled by Neighbor-Joining (NJ) algorithm.
Mega 5.1 phylogenetic results suggested that alpha amylases of thermo stable organisms i.e. Pyrococcus furiosus (100-105°C), Bacillus
licheniformis (90-95°C), Geobacillus stearothermophilus (75°C) and Bacillus amyloliquefaciens (72°C) are more distantly related as
compared to less thermo stable organisms. By keeping in mind the characteristics of most thermo stable alpha amylases novel and
improved features can be introduced in less thermo stable alpha amylases so that they become more thermo tolerant and
productive for industry. 相似文献
795.
Syed Shahid Abbas Manish Kakkar Elizabeth Tacket Rogawski 《PLoS neglected tropical diseases》2014,8(2)
The study aimed to determine costs to the state government of implementing different interventions for controlling rabies among the entire human and animal populations of Tamil Nadu. This built upon an earlier assessment of Tamil Nadu''s efforts to control rabies. Anti-rabies vaccines were made available at all health facilities. Costs were estimated for five different combinations of animal and human interventions using an activity-based costing approach from the provider perspective. Disease and population data were sourced from the state surveillance data, human census and livestock census. Program costs were extrapolated from official documents. All capital costs were depreciated to estimate annualized costs. All costs were inflated to 2012 Rupees. Sensitivity analysis was conducted across all major cost centres to assess their relative impact on program costs. It was found that the annual costs of providing Anti-rabies vaccine alone and in combination with Immunoglobulins was $0.7 million (Rs 36 million) and $2.2 million (Rs 119 million), respectively. For animal sector interventions, the annualised costs of rolling out surgical sterilisation-immunization, injectable immunization and oral immunizations were estimated to be $ 44 million (Rs 2,350 million), $23 million (Rs 1,230 million) and $ 11 million (Rs 590 million), respectively. Dog bite incidence, health systems coverage and cost of rabies biologicals were found to be important drivers of costs for human interventions. For the animal sector interventions, the size of dog catching team, dog population and vaccine costs were found to be driving the costs. Rabies control in Tamil Nadu seems a costly proposition the way it is currently structured. Policy makers in Tamil Nadu and other similar settings should consider the long-term financial sustainability before embarking upon a state or nation-wide rabies control programme. 相似文献
796.
Vikrant Rachakonda Charles Gabbert Amit Raina Lauren N. Bell Sara Cooper Shahid Malik Jaideep Behari 《PloS one》2014,9(12)
Background and Objectives
While animal studies have implicated derangements of global energy homeostasis in the pathogenesis of acute alcoholic hepatitis (AAH), the relevance of these findings to the development of human AAH remains unclear. Using global, unbiased serum metabolomics analysis, we sought to characterize alterations in metabolic pathways associated with severe AAH and identify potential biomarkers for disease prognosis.Methods
This prospective, case-control study design included 25 patients with severe AAH and 25 ambulatory patients with alcoholic cirrhosis. Serum samples were collected within 24 hours of the index clinical encounter. Global, unbiased metabolomics profiling was performed. Patients were followed for 180 days after enrollment to determine survival.Results
Levels of 234 biochemicals were altered in subjects with severe AAH. Random-forest analysis, principal component analysis, and integrated hierarchical clustering methods demonstrated that metabolomics profiles separated the two cohorts with 100% accuracy. Severe AAH was associated with enhanced triglyceride lipolysis, impaired mitochondrial fatty acid beta oxidation, and upregulated omega oxidation. Low levels of multiple lysolipids and related metabolites suggested decreased plasma membrane remodeling in severe AAH. While most measured bile acids were increased in severe AAH, low deoxycholate and glycodeoxycholate levels indicated intestinal dysbiosis. Several changes in substrate utilization for energy homeostasis were identified in severe AAH, including increased glucose consumption by the pentose phosphate pathway, altered tricarboxylic acid (TCA) cycle activity, and enhanced peptide catabolism. Finally, altered levels of small molecules related to glutathione metabolism and antioxidant vitamin depletion were observed in patients with severe AAH. Univariable logistic regression revealed 15 metabolites associated with 180-day survival in severe AAH.Conclusion
Severe AAH is characterized by a distinct metabolic phenotype spanning multiple pathways. Metabolomics profiling revealed a panel of biomarkers for disease prognosis, and future studies are planned to validate these findings in larger cohorts of patients with severe AAH. 相似文献797.
798.
Muhammad Rauf Khurram Shahzad Rashid Ali Moddassir Ahmad Imran Habib Shahid Mansoor Gerald A. Berkowitz Nasir A. Saeed 《Molecular biology reports》2014,41(3):1669-1682
Abiotic stresses such as salinity and drought have adverse effects on plants. In the present study, a Na+/H+ antiporter gene homologue (LfNHX1) has been cloned from a local halophyte grass (Leptochloa fusca). The LfNHX1 cDNA contains an open reading frame of 1,623 bp that encodes a polypeptide chain of 540 amino acid residues. LfNHX1 protein sequence showed high similarity with NHX1 homologs reported from other halophyte plants. Amino acid and nucleotide sequence similarity, protein topology modeling and the presence of conserved functional domains in the LfNHX1 protein sequence classified it as a vacuolar NHX1 homolog. The overexpression of LfNHX1 gene under CaMV35S promoter conferred salt and drought tolerance in tobacco plants. Under drought stress, transgenic plants showed higher relative water contents, photosynthetic rate, stomatal conductance and membrane stability index as compared to wild type plants. More negative value of leaf osmotic potential was also observed in transgenic plants when compared with wild type control plants. Transgenic plants showed better germination and root growth at 2 mg L?1 Basta herbicide and three levels (100, 200 and 250 mM) of sodium chloride. These results showed that LfNHX1 is a potential candidate gene for enhancing drought and salt tolerance in crops. 相似文献
799.
Shahid Akbar Khalil Roshan Zamir Nisar Ahmad 《Saudi Journal of Biological Sciences》2014,21(6):566-573
Stevia rebaudiana (Bert.) is an emerging sugar alternative and anti-diabetic plant in Pakistan. That is why people did not know the exact time of propagation. The main objective of the present study was to establish feasible propagation methods for healthy biomass production. In the present study, seed germination, stem cuttings and micropropagation were investigated for higher productivity. Fresh seeds showed better germination (25.51–40%) but lost viability after a few days of storage. In order to improve the germination percentage, seeds were irradiated with 2.5, 5.0, 7.5 and 10 Gy gamma doses. But gamma irradiation did not show any significant change in seed germination. A great variation in survival of stem cutting was observed in each month of 2012. October and November were found the most suitable months for stem cutting survival (60%). In order to enhance survival, stem cuttings were also dipped in different plant growth regulators (PGRs) solution. Only indole butyric acid (IBA; 1000 ppm) treated cutting showed a higher survival (33%) than control (11.1%). Furthermore, simple and feasible indirect regeneration system was established from leaf explants. Best callus induction (84.6%) was observed on MS-medium augmented with 6-benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D; 2.0 mg l−1). For the first time, we obtained the highest number of shoots (106) on a medium containing BA (1.5 mg l−1) and gibberellic acid (GA3; 0.5 mg l−1). Plantlets were successfully acclimatized in plastic pots. The current results preferred micropropagation (85%) over seed germination (25.51–40%) and stem cutting (60%). 相似文献
800.
Doroteya Raykova Joakim Klar Aysha Azhar Tahir Naeem Khan Naveed Altaf Malik Muhammad Iqbal Muhammad Tariq Shahid Mahmood Baig Niklas Dahl 《PloS one》2014,9(4)
Pure hair and nail ectodermal dysplasia (PHNED) comprises a heterogeneous group of rare heritable disorders characterized by brittle hair, hypotrichosis, onychodystrophy and micronychia. Autosomal recessive (AR) PHNED has previously been associated with mutations in either KRT85 or HOXC13 on chromosome 12p11.1-q14.3. We investigated a consanguineous Pakistani family with AR PHNED linked to the keratin gene cluster on 12p11.1 but without detectable mutations in KRT85 and HOXC13. Whole exome sequencing of affected individuals revealed homozygosity for a rare c.821T>C variant (p.Phe274Ser) in the KRT74 gene that segregates AR PHNED in the family. The transition alters the highly conserved Phe274 residue in the coil 1B domain required for long-range dimerization of keratins, suggesting that the mutation compromises the stability of intermediate filaments. Immunohistochemical (IHC) analyses confirmed a strong keratin-74 expression in the nail matrix, the nail bed and the hyponychium of mouse distal digits, as well as in normal human hair follicles. Furthermore, hair follicles and epidermis of an affected family member stained negative for Keratin-74 suggesting a loss of function mechanism mediated by the Phe274Ser substitution. Our observations show for the first time that homozygosity for a KRT74 missense variant may be associated with AR PHNED. Heterozygous KRT74 mutations have previously been associated with autosomal dominant woolly hair/hypotrichosis simplex (ADWH). Thus, our findings expand the phenotypic spectrum associated with KRT74 mutations and imply that a subtype of AR PHNED is allelic with ADWH. 相似文献