全文获取类型
收费全文 | 982篇 |
免费 | 52篇 |
国内免费 | 1篇 |
专业分类
1035篇 |
出版年
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 26篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 13篇 |
2016年 | 20篇 |
2015年 | 42篇 |
2014年 | 58篇 |
2013年 | 77篇 |
2012年 | 83篇 |
2011年 | 72篇 |
2010年 | 47篇 |
2009年 | 51篇 |
2008年 | 57篇 |
2007年 | 58篇 |
2006年 | 48篇 |
2005年 | 47篇 |
2004年 | 21篇 |
2003年 | 31篇 |
2002年 | 36篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 17篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 16篇 |
1988年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1967年 | 2篇 |
1964年 | 4篇 |
排序方式: 共有1035条查询结果,搜索用时 15 毫秒
41.
S Govatati NR Tipirisetti S Perugu VL Kodati M Deenadayal V Satti M Bhanoori S Shivaji 《PloS one》2012,7(7):e40668
Background
Endometriosis is a chronic gynecological benign disease that shares several features similar to malignancy. Mitochondrial DNA (mtDNA) mutations have been reported in all most all types of tumors. However, it is not known as to whether mtDNA mutations are associated with endometriosis.Methodology
We sequenced the entire mitochondrial genome of analogous ectopic and eutopic endometrial tissues along with blood samples from 32 advanced stage endometriosis patients to analyze the role of somatic and germ-line mtDNA variations in pathogenesis of endometriosis. All ectopic tissues were screened for tumor-specific mtDNA deletions and microsatellite instability (MSI). We also performed mtDNA haplogrouping in 128 patients and 90 controls to identify its possible association with endometriosis risk.Principal Findings
We identified 51 somatic (novel: 31; reported: 20) and 583 germ-line mtDNA variations (novel: 53; reported: 530) in endometriosis patients. The A13603G, a novel missense mutation which leads to a substitution from serine to glycine at the codon 423 of ND5 gene showed 100% incidence in ectopic tissues. Interestingly, eutopic endometrium and peripheral leukocytes of all the patients showed heteroplasmy (A/G; 40–80%) at this locus, while their ectopic endometrium showed homoplasmic mutant allele (G/G). Superimposition of native and mutant structures of ND5 generated by homology modeling revealed no structural differences. Tumor-specific deletions and MSI were not observed in any of the ectopic tissues. Haplogrouping analysis showed a significant association between haplogroup M5 and endometriosis risk (P: 0.00069) after bonferroni correction.Conclusions
Our findings substantiate the rationale for exploring the mitochondrial genome as a biomarker for the diagnosis of endometriosis. 相似文献42.
Lakshmi D Gopinath K Jayanthy G Anjum S Prakash D Sudhandiran G 《Neurochemical research》2012,37(9):1859-1867
Acrylamide (ACR) is a known industrial toxic chemical that produce neurotoxicity characterized by progressive neuronal degeneration. This study was designed to investigate the protective effect of fish oil on ACR-induced neuronal damage in Wistar rats. ACR enhances the production of reactive oxygen species and potentially affects brain. ACR administered rats showed increased levels of lipid peroxidative product, protein carbonyl content, hydroxyl radical and hydroperoxide which were significantly modulated by the supplementation of fish oil. The activities of enzymic antioxidants and levels of reduced glutathione were markedly lowered in ACR-induced rats; fish oil treatment augmented these antioxidant levels in cortex. Free radicals generated during ACR administration reduced the activities of membrane adenosine triphosphatases and acetylcholine esterase. Fish oil enhanced the activities of these enzymes near normal level. Histological observation represented the protective role of fish oil in ACR-induced neuronal damage. Fish oil reduced the ACR-induced apoptosis through the modulation in expressions of B-cell lymphoma 2 (Bcl2)-associated X protein and Bcl2-associated death promoter. Further, fish oil increases the expression of heat shock protein 27 (Hsp27) in ACR-induced rats. This study provides evidence for the neuroprotective effect of fish oil on ACR-induced neurotoxicity by reducing oxidative stress and apoptosis with modulation in the expression of Hsp27. 相似文献
43.
Paramonorcheides selaris n. sp. is described from the intestine of the carangid fish Selar crumenophthalmus (Bloch) off the Visakhapatnam coast, Bay of Bengal. It is closest to the Australian species P. pseudocaranxi Dove & Cribb, 1998, but differs in its shorter cirrus-sac extending only to the level of the ovary rather than to the level
of the testes, in lacking eye-spot pigment and in details of the armature of the terminal genitalia. P. pseudocaranxi of Machida (2005) is regarded as identical to the new species. The validity of Allobacciger Hafeezullah & Siddiqi, 1970, as distinct from Monorcheides Odhner, 1905, is discussed. A key to the six species of Paramonorcheides Yamaguti, 1938 is presented. 相似文献
44.
Anuj K. Chandel M. Lakshmi Narasu G. Chandrasekhar A. Manikyam L. Venkateswar Rao 《Bioresource technology》2009,100(8):2404-2410
Saccharum spontaneum is a wasteland weed consists of 45.10 ± 0.35% cellulose and 22.75 ± 0.28% of hemicellulose on dry solid (DS) basis. Aqueous ammonia delignified S. spontaneum yielded total reducing sugars, 53.91 ± 0.44 g/L (539.10 ± 0.55 mg/g of substrate) with a hydrolytic efficiency of 77.85 ± 0.45%. The enzymes required for hydrolysis were prepared from culture supernatants of Aspergillus oryzae MTCC 1846. A maximum of 0.85 ± 0.07 IU/mL of filter paperase (FPase), 1.25 ± 0.04 IU/mL of carboxy methyl cellulase (CMCase) and 55.56 ± 0.52 IU/mL of xylanase activity was obtained after 7 days of incubation at 28 ± 0.5 °C using delignified S. spontaneum as carbon source under submerged fermentation conditions. Enzymatic hydrolysate of S. spontaneum was then tested for ethanol production under batch and repeated batch production system using “in-situ” entrapped Saccharomyces cerevisiae VS3 cells in S. spontaneum stalks (1 cm × 1 cm) size. Immobilization was confirmed by the scanning electron microscopy (SEM). Batch fermentation of VS3 free cells and immobilized cells showed ethanol production, 19.45 ± 0.55 g/L (yield, 0.410 ± 0.010 g/g) and 21.66 ± 0.62 g/L (yield, 0.434 ± 0.021 g/g), respectively. Immobilized VS3 cells showed maximum ethanol production (22.85 ± 0.44 g/L, yield, 0.45 ± 0.04 g/g) up to 8th cycle during repeated batch fermentation followed by a gradual reduction in subsequent cycles of fermentation. 相似文献
45.
A method has been developed for immobilisation of antisera on fresh plastic tubes through an immunochemical bridge. This type
of immobilisation has been shown to be more consistent than direct adsorption on plastic. Such immunochemically coated antisera
on plastic tube has been used in the development of a noncentrifugation radioimmunoassay. This assay system has been found
to be technically as sound as the conventional method. 相似文献
46.
In the present investigation, a microorganism hydrolyzing carboxymethylcellulose (CMC) was isolated and identified as Bacillus subtilis strain LFS3 by 16S rDNA sequence analysis. The carboxymethylcellulase (CMCase) enzyme produced by the B. subtilis strain LFS3 was purified by (NH?)?SO? precipitation, ion exchange and gel filtration chromatography, with an overall recovery of 15 %. Native-PAGE analysis of purified CMCase revealed the molecular weight of enzyme to be about 185 kDa. The activity profile of CMCase enzyme showed the optimum activity at temperature 60 °C and pH 4.0, respectively. The enzyme activity was induced by Na?, Mg2?, NH??, and EDTA, whereas strongly inhibited by Hg2? and Fe3?. The purified enzyme hydrolyzed CMC, filter paper, and xylan, but not p-nitrophenyl β-D-glucopyranoside and cellulose. Kinetic analysis of purified enzyme showed the K(m) value of 2.2 mg/ml. Thus, acidophilic as well as thermophilic nature makes this cellulase a suitable candidate for current mainstream biomass conversion into fuel and other industrial processes. 相似文献
47.
Apeksha Sahu Satwant Kumar Sreelakshmi K Sreenivasamurthy Lakshmi Dhevi N Selvan Anil K Madugundu Soujanya D Yelamanchi Vinuth N Puttamallesh Gourav Dey Abhijith K Anil Anand Srinivasan Kanchan K Mukherjee Harsha Gowda Parthasarathy Satishchandra Anita Mahadevan Akhilesh Pandey Thottethodi Subrahmanya Keshava Prasad Susarla Krishna Shankar 《Clinical proteomics》2014,11(1)
Background
Toxoplasma encephalitis is caused by the opportunistic protozoan parasite Toxoplasma gondii. Primary infection with T. gondii in immunocompetent individuals remains largely asymptomatic. In contrast, in immunocompromised individuals, reactivation of the parasite results in severe complications and mortality. Molecular changes at the protein level in the host central nervous system and proteins associated with pathogenesis of toxoplasma encephalitis are largely unexplored. We used a global quantitative proteomic strategy to identify differentially regulated proteins and affected molecular networks in the human host during T. gondii infection with HIV co-infection.Results
We identified 3,496 proteins out of which 607 proteins were differentially expressed (≥1.5-fold) when frontal lobe of the brain from patients diagnosed with toxoplasma encephalitis was compared to control brain tissues. We validated differential expression of 3 proteins through immunohistochemistry, which was confirmed to be consistent with mass spectrometry analysis. Pathway analysis of differentially expressed proteins indicated deregulation of several pathways involved in antigen processing, immune response, neuronal growth, neurotransmitter transport and energy metabolism.Conclusions
Global quantitative proteomic approach adopted in this study generated a comparative proteome profile of brain tissues from toxoplasma encephalitis patients co-infected with HIV. Differentially expressed proteins include previously reported and several new proteins in the context of T. gondii and HIV infection, which can be further investigated. Molecular pathways identified to be associated with the disease should enhance our understanding of pathogenesis in toxoplasma encephalitis.Electronic supplementary material
The online version of this article (doi:10.1186/1559-0275-11-39) contains supplementary material, which is available to authorized users. 相似文献48.
49.
50.
Studies in children and mice have shown that respiratory infection alters riboflavin metabolism, resulting in increased urinary loss of this vitamin. This could be due to mobilization of riboflavin from the liver to blood because liver Flavin adenine dinucleotide (FAD) levels were lowered in the mice during infection. To understand the functional implications of lowered hepatic FAD levels during respiratory infection, flavoprotein functions such as oxidative phosphorylation and β-oxidation of the liver mitochondria were examined during infection in mice. Weanling mice were fed either riboflavin-restricted or control diet for 18 days and then injected with a sublethal dose of Klebsiella pneumoniae. During infection, the state 3 respiratory rate with palmitoyl-L-carnitine and glutamate were significantly lowered (27–29%) in the riboflavin-restricted group, whereas in the control group 10% reduction was observed with palmitoyl-L-carnitine as substrate. A 22% reduction in the respiratory control ratio with palmitoyl-L-carnitine as substrate was observed during infection in the riboflavin-restricted group. The β-oxidation of palmitoyl-L-carnitine was significantly lowered (29%) in the riboflavin-restricted infected group. The results of the study suggest that the effects of infection on vital physiologic functions were more pronounced in the riboflavin-restricted mice than in the control mice. © Elsevier Science Inc. 1999 相似文献