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   736篇
  免费   48篇
  2024年   2篇
  2023年   9篇
  2022年   23篇
  2021年   37篇
  2020年   24篇
  2019年   31篇
  2018年   29篇
  2017年   25篇
  2016年   32篇
  2015年   39篇
  2014年   52篇
  2013年   46篇
  2012年   78篇
  2011年   55篇
  2010年   35篇
  2009年   32篇
  2008年   52篇
  2007年   38篇
  2006年   22篇
  2005年   19篇
  2004年   22篇
  2003年   23篇
  2002年   11篇
  2001年   13篇
  2000年   4篇
  1999年   7篇
  1998年   4篇
  1997年   3篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1983年   1篇
  1981年   1篇
  1979年   1篇
  1978年   3篇
  1975年   1篇
  1974年   3篇
排序方式: 共有784条查询结果,搜索用时 390 毫秒
81.
ImmuPlus, a polyherbal commercial formulation was used to modulate the immune system of commercially important giant freshwater prawn M. rosenbergii. The prawns were fed with basal diet supplemented with ImmuPlus at 1g/kg feed for 4 weeks. Results showed that the phenoloxidase activity (PO), haemagglutination and lysozyme activities were significantly elevated in ImmuPlus-fed prawn up to 3 weeks of feeding and declined after 4 weeks of feeding. The total protein level in ImmuPlus-fed prawn raised up to 2nd week of feeding. Incorporation of ImmuPlus at the rate of 1g/kg feed in the diet of prawn for 3 weeks may be beneficial in raising the immune status of prawn.  相似文献   
82.
83.
Sahoo S  DeMay RM 《Acta cytologica》2004,48(2):161-164
OBJECTIVE: To evaluate several conventional cervical smears obtained from women undergoing routine screening for cervical dysplasia or carcinoma and whose smears contained structures resembling collagen balls. STUDY DESIGN: Between 1995 and 1998, cervical smears containing collagen balls were analyzed. The clinical histories of the patients whose smears contained collagen balls, including the gestational history, were reviewed. Histopathologic material from any related surgical specimens was reviewed, with special attention to mesothelial surfaces. RESULTS: Collagen balls were found in 5 of 77,891 Pap smears examined (0.006%). None of the patients had evidence of neoplasms of the genital tract. One of the patients was in the first trimester of pregnancy. CONCLUSION: We suggest that collagen balls in cervical smear originate in mesothelium-covered organs, from where they are transported via the fallopian tubes into the uterine cavity. Their significance lies in their being mistaken for mucin-distended cells exfoliated from a neoplasm or from detached fragments of a papillary ovarian neoplasm.  相似文献   
84.
85.
Polymorphisms in mitochondrial (mt) DNA and Y-chromosomes of seven socially and linguistically diverse castes and tribes of Eastern India were examined to determine their genetic relationships, their origin, and the influence of demographic factors on population structure. Samples from the Orissa Brahmin, Karan, Khandayat, Gope, Juang, Saora, and Paroja were analyzed for mtDNA hypervariable sequence (HVS) I and II, eight Y-chromosome short tandem repeats (Y-STRs), and lineage-defining mutations diagnostic for Indian- and Eurasian-specific haplogroups. Our results reveal that haplotype diversity and mean pairwise differences (MPD) was higher in caste groups of the region (>0.998, for both systems) compared to tribes (0.917-0.996 for Y-STRs, and 0.958-0.988 for mtDNA haplotypes). The majority of paternal lineages belong to the R1a1, O2a, and H haplogroups (62.7%), while 73.2% of maternal lineages comprise the Indian-specific M*, M5, M30, and R* mtDNA haplogroups, with a sporadic occurrence of West Eurasian lineages. Our study reveals that Orissa Brahmins (a higher caste population) have a genetic affinity with Indo-European speakers of Eastern Europe, although the Y-chromosome data show that the genetic distances of populations are not correlated to their position in the caste hierarchy. The high frequency of the O2a haplogroup and absence of East Asian-specific mtDNA lineages in the Juang and Saora suggest that a migration of Austro-Asiatic tribes to mainland India was exclusively male-mediated which occurred during the demographic expansion of Neolithic farmers in southern China. The phylogeographic analysis of mtDNA and Y-chromosomes revealed varied ancestral sources for the diverse genetic components of the populations of Eastern India.  相似文献   
86.
Stochastic mRNA synthesis in mammalian cells   总被引:1,自引:0,他引:1       下载免费PDF全文
  相似文献   
87.
Granulocyte-macrophage colony stimulating factor (GMCSF), a multifunctional cytokine can enhance immune responses when administered along with DNA vaccine. Aim of the present study was to clone and express the chicken GMCSF cytokine for use as 'genetic adjuvant'. Chicken GMCSF gene 435bp was amplified using specific primers in which restriction sites of BamHI and HindIII were at forward and reverse primers respectively. The PCR product was cloned into eukaryotic expression vector pcDNA 3.1(+) and clones were confirmed by restriction digestion and nucleotide sequencing. Functional activity of recombinant GMCSF was checked by expression of GMCSF specific mRNA in transfected Vero cells by RT-PCR of total RNA isolated from transfected Vero cells. The recombinant plasmid can be used as genetic adjuvant in chicken.  相似文献   
88.
Four different mononuclear octahedral Ni(II) complexes with protonated and deprotonated form of the same ligand have been synthesized by controlling reaction conditions and structurally characterized. The complexes are [Ni(HLl-his)(benzoate)(MeOH)] (1), [Ni(HLl-his)(SCN)(MeOH)] (2), [Ni(HLl-his)2] (3) and [Ni(Ll-his)(imidazole)2] (4) where H2Ll-his is (S)-2-(2-hydroxybenzylamino)-3-(1H-imidazol-4-yl)-propionic acid. The ligand behaves as a monobasic tetradentate ligand in 1 and 2, monobasic tridentate ligand in 3 and dibasic tetradentate ligand in 4. Ni(II) coordinated phenolic proton of the ligand in the complexes 1-2 shows strong intra-molecular H-bonding with benzoate in 1 and lattice water in 2, whereas 3 shows intermolecular H-bonding between uncoordinated phenols with neighbouring carboxylate. The pH titration of the complexes revealed that metal coordination and H-bond in complexes 1 and 2 considerably lowers the acidity of ligand phenol (pKa 6.8 and 7.0 respectively) compared to phenol (pKa 10). The complex 4 does not show any proton loss due to the absence of phenolic proton. All the complexes show extensive H-bonded network in the crystals including narrow (7.8 × 5.2 Å) water filled one dimensional channel in 2.  相似文献   
89.
The surface activity and self-assembly behavior of zwitterionic amphiphile N-(2-hydroxydodecyl)-l-histidine (C12HHis) were studied in phosphate buffers of pH 2 and 13 using surface tension and fluorescence probe techniques, respectively. Transmission electron microscopic images of the aggregates have revealed existence of nano-size vesicles in dilute solutions of both acidic and basic pH. In basic medium, the vesicles are converted to tubular aggregates upon increase of surfactant concentration. The nanotubes undergo phase transition to form elongated or small rod-like micelles at a much higher concentration of the amphiphile. The vesicles and nanotubes were found to become more stable upon addition of 10 mol% of cholesterol.  相似文献   
90.
The present study was aimed to investigate the chemopreventive potential of carnosic acid in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. The chemopreventive potential was assessed by analyzing the tumor incidence, tumor volume and burden as well as by measuring the status of lipid peroxidation, non-enzymatic and enzymatic antioxidants and phase I and phase II detoxification enzymes. Oral squamous cell carcinoma was developed in the buccal pouch of golden Syrian hamsters by painting with 0.5% DMBA in liquid paraffin three times a week for 14 weeks. In the present study, 100% tumor formation was observed in hamsters treated with DMBA alone. Also, the status of lipid peroxidation, antioxidants and phase I and phase II detoxification enzymes were significantly altered during DMBA-induced oral carcinogenesis. Oral administration of carnosic acid at a dose of 10 mg/kg body weight/day to DMBA-treated animals completely prevented the tumor formation in the hamsters’ buccal pouches. Also, carnosic acid exerted potent anti-lipid peroxidative function and stimulated the detoxification cascade during DMBA-induced hamster buccal pouch carcinogenesis. The results of the present study suggest that the chemopreventive potential of carnosic acid is probably due to its anti-lipid peroxidative potential and modulating effect on carcinogen detoxification enzymes during DMBA-induced oral carcinogenesis.  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