首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   373篇
  免费   19篇
  2024年   1篇
  2023年   6篇
  2022年   8篇
  2021年   11篇
  2020年   8篇
  2019年   9篇
  2018年   5篇
  2017年   6篇
  2016年   19篇
  2015年   11篇
  2014年   12篇
  2013年   26篇
  2012年   23篇
  2011年   26篇
  2010年   14篇
  2009年   14篇
  2008年   21篇
  2007年   21篇
  2006年   29篇
  2005年   17篇
  2004年   18篇
  2003年   16篇
  2002年   7篇
  2001年   10篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   4篇
  1996年   1篇
  1993年   1篇
  1992年   2篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1984年   2篇
  1983年   3篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1972年   3篇
  1970年   2篇
  1968年   5篇
  1967年   1篇
排序方式: 共有392条查询结果,搜索用时 15 毫秒
31.
The aim of this study is to investigate whether PI3K (phosphatidylinositol-3-kinase) is involved in IL-1β (interleukin-1β)-induced IL-6 production in A549 (human lung adenocarcinoma epithelial cell) and human RASF (rheumatoid arthritis synovial fibroblast). PI3K inhibitor, LY294002 significantly reduced IL-1β-induced IL-6 production in A549 cells but not in RASF, indicating that IL-1β-induced IL-6 production was partially mediated by PI3Kin A549 cells but not in RASF. siRNA (small interfering RNA) of IRAK4 (IL-1 receptor-associated kinase 4) treatment decreased IRAK4 mRNA level by up to 90% in A549 cells. In this condition, IL-1β-induced increase of IL-6 mRNA and protein level was decreased by up to 93% and 70%, respectively. Furthermore, the combination of IRAK4 siRNA and LY294002 treatment decreased protein induction level of IL-6 in A549 cells compared with that of IRAK4 siRNA or LY294002 alone. These results indicate that IL-1β-induced IL-6 production in A549 cells is mediated by both PI3K and IRAK4 and suggest that involvement of PI3K in the IL-1-induced IL-6 production is cell type specific.  相似文献   
32.
Insult     
INSULT, a novel method for the creation of insertions, deletions, and point mutations without subcloning, requires only one new primer per mutant, and produces circular plasmids, obviating the need for special “ultracompetent” cells. The method includes cycles of linear amplification with a thermophilic polymerase, and nick repair after each cycle with a thermophilic ligase. After production of multiple single-stranded copies of circular mutation-bearing plasmid DNA, addition of a “generic” primer followed by one or more polymerase reaction cycles generates double-stranded circular DNA bearing the desired mutation.  相似文献   
33.
34.
The efficacy of low‐toxicity chemicals as possible alternatives to synthetic fungicides for the control of Uromyces appendiculatus and Puccinia triticina was evaluated. A preliminary selection of food additives was performed through in vitro and in vivo preliminary screenings. The ED50 and minimum inhibition concentration (MIC) values showed that most of the food additives used in this study were more toxic to U. appendiculatus than to P. triticina. Acetic acid, potassium carbonate, sodium carbonate and sodium molybdate were the food additives that were more toxic to the urediniospores of P. triticina. Selected compounds and concentrations were tested on bean and wheat plants grown in pots under controlled conditions. Acetic acid, ammonium bicarbonate, potassium acetate, potassium benzoate, potassium bicarbonate, potassium carbonate, sodium acetate and sodium citrate at 0.03, 0.09, 0.03, 0.006, 0.012, 0.012, 0.03 and 0.03 m , respectively, significantly reduced the disease severity of U. appendiculatus without causing any injury to bean leaves. Ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate and sodium citrate at 0.12, 0.03, 0.12 and 0.03 m , respectively, were the most effective in reducing the disease severity caused by P. triticina without causing any injury to wheat leaves.  相似文献   
35.
Oxidative stress in the reproductive system is thought to have an effect on the fertilizing ability of sperm. The purpose of this study was to assess the interaction of iron (Fe) and copper (Cu) ions in suspected subfertile and fertile male groups and to find out the relationships of the semen parameters (sperm count, motility, and abnormal morphology), glutathione, malondialdehyde, and reactive oxygen species with these variables. Semen and blood obtained from 60 subfertile men and from 40 fertile volunteers were examined. The sperm count and motility in the subfertile male group were found lower than those in fertile male group (p<0.001). Cu levels in serum and seminal plasma in the subfertile male group were significantly higher than those in the fertile male group (p<0.001 and p<0.05, respectively). There was also a significant increase in the Fe level of seminal plasma in the subfertile male group (p<0.001). However, there was no significant difference in the Fe level of serum in the subfertile male group. In conclusion, these findings suggest that Cu and Fe might be mediators of the effects of oxidative damage and play an essential role in spermatogenesis and male infertility; the determination of Fe and Cu levels in serum and seminal plasma during infertility investigation is recommended.  相似文献   
36.
After pelvic surgeries such as radical prostatectomy, two major complications--urinary incontinence and erectile dysfunction (ED) may occur. Etiologies for ED are multiple pathologic mediators/systems. Oxidative stress, which is known to be induced after surgical trauma, could be a cause of ED. The purposes of in this study are to investigate the effect of unilateral manipulation/ dissection and resection of the cavernous nerve (neurotomy) to NOS (nitric oxide synthase)-containing nerve fibers and pressure after electro stimulation in rat corpus cavernosum, and to determine whether these procedures would produce oxidative stress within rat cavernous tissue 3 weeks and 6 months after the operation. Male rats were divided into 5 groups. Rats in groups 1 and 2 underwent unilateral cavernous nerve manipulation and sacrificed 3 weeks and 6 months after the operation, respectively. Rats in groups 3 and 4 underwent unilateral neurotomy of a 5-mm. segment of the cavernous nerve, and they were sacrificed 3 weeks and 6 months after nerve ablation, respectively. Group 5 rats were control animals for biochemical analysis. Intracavernous pressure following electro stimulation reduced is significantly 3 weeks after unilateral resection, as compared to that of the manipulated nerve (P < 0.05), and it recovered 6 months after neurotomy. The recovery was also confirmed by NADPH (nicotinamide adenine dinucleotide phosphate) diaphorase staining in neurotomy groups. Lipid peroxidation, which is an indicater of oxidative stress, was determined by measuring thiobarbituric acid reacting substance (TBARS) levels and superoxide dismutase (SOD) activity. These markers indicated that unilateral cavernous nerve manipulation or resection produced oxidative stress within rat corpus cavernosum. Oxidative stress was more prominent 3 weeks after unilateral neurotomy (P < 0.05). Also, compared to the control animal group, oxidative stress was observed three weeks after manipulation of unilateral cavernous nerve (P < 0.05). Resection of the cavernous nerve caused more prominent oxidative stress than in the manipulation group. This study suggested, that unilateral cavernous neurotomy caused a decrease of intra cavernous pressure and NOS fibers in rat corpus cavernosum, and they recovered 6 months after neurotomy. Our data also provided evidence that neurotomy and manipulation of the cavernous nerve caused oxidative stress in rat corpus cavernosum and that oxidative stress was more prominent in the nerve resection group.  相似文献   
37.
The roles of nitric oxide production and oxidative process were studied in mice infected with Toxocara canis and treated with aminoguanidine which is a specific inhibitor of inducible nitric oxide synthase (iNOS). Relations of nitric oxide synthase inhibition and tissue pathology were assessed by biochemical, histological and immunohistochemical methods. In experiments, Balb/c albino mice were inoculated with T. canis eggs either with or without aminoguanidine treatment or alone, at 24th, 48th hours and on 7th days. LPx and SOD values in liver tissue and plasma were measured. Liver and lung tissues were evaluated for the pathological lesions. The expression of eNOS and iNOS in both tissues were studied with immunohistochemistry in the same intervals. We observed significant differences between T. canis infected and aminoguanidine treated animals. Larval toxocarosis led to oxidative stress elevation in plasma. Microscopic examination of the liver histological sections revealed pathological lesions in the hepatic parenchyma in infected mice. In the mice received T. canis eggs plus aminoguanidine, the sinusoidal areas were enlarged. Histological lesions were more severe at 48 hours after infection. Numbers of eNOS and iNOS expressing epithelial cells were increased in the T. canis infected mice. The activities of eNOS and iNOS were also observed in the body of the larvae which have migrated to lung and liver. As a result, we have demonstrated that in vivo production of eNO and iNO during T. canis infection cause direct host damages and it is strongly related to the oxidative stress. We propose that larval NO can also be effective in larval migration, but it needs further investigation on distribution of NO in larvae.  相似文献   
38.
39.
Catalase is sorted to peroxisomes via a C-terminal peroxisomal targeting signal 1 (PTS1), which binds to the receptor protein Pex5. Analysis of the C-terminal sequences of peroxisomal catalases from various species indicated that catalase never contains the typical C-terminal PTS1 tripeptide-SKL, but invariably is sorted to peroxisomes via a non-canonical sorting sequence. We analyzed the relevance of the non-canonical PTS1 of catalase of the yeast Hansenula polymorpha (-SKI). Using isothermal titration microcalorimetry, we show that the affinity of H. polymorpha Pex5 for a peptide containing -SKI at the C-terminus is 8-fold lower relative to a peptide that has a C-terminal -SKL. Fluorescence microscopy indicated that green fluorescent protein containing the -SKI tripeptide (GFP-SKI) has a prolonged residence time in the cytosol compared to GFP containing -SKL. Replacing the -SKI sequence of catalase into -SKL resulted in reduced levels of enzymatically active catalase in whole cell lysates together with the occurrence of catalase protein aggregates in the peroxisomal matrix. Moreover, the cultures showed a reduced growth yield in methanol-limited chemostats. Finally, we show that a mutant catalase variant that is unable to properly fold mislocalizes in protein aggregates in the cytosol. However, by replacing the PTS1 into -SKL the mutant variant accumulates in protein aggregates inside peroxisomes. Based on our findings we propose that the relatively weak PTS1 of catalase is important to allow proper folding of the enzyme prior to import into peroxisomes, thereby preventing the accumulation of catalase protein aggregates in the organelle matrix.  相似文献   
40.
Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号