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   1969篇
  免费   93篇
  2023年   24篇
  2022年   17篇
  2021年   46篇
  2020年   24篇
  2019年   36篇
  2018年   59篇
  2017年   44篇
  2016年   51篇
  2015年   92篇
  2014年   120篇
  2013年   142篇
  2012年   172篇
  2011年   151篇
  2010年   88篇
  2009年   85篇
  2008年   120篇
  2007年   91篇
  2006年   91篇
  2005年   79篇
  2004年   65篇
  2003年   61篇
  2002年   55篇
  2001年   29篇
  2000年   33篇
  1999年   24篇
  1998年   11篇
  1997年   6篇
  1996年   6篇
  1995年   12篇
  1994年   5篇
  1993年   11篇
  1992年   12篇
  1991年   17篇
  1990年   18篇
  1989年   24篇
  1988年   11篇
  1987年   14篇
  1986年   22篇
  1985年   11篇
  1984年   8篇
  1983年   10篇
  1982年   7篇
  1981年   12篇
  1980年   5篇
  1978年   3篇
  1977年   6篇
  1975年   5篇
  1974年   4篇
  1972年   3篇
  1969年   4篇
排序方式: 共有2062条查询结果,搜索用时 678 毫秒
981.

Background

Researchers working in the area of Public Health are being confronted with large volumes of data on various aspects of entomology and epidemiology. To obtain the relevant information out of these data requires particular database management system. In this paper, we have described about the usages of our developed database on lymphatic filariasis.

Methods

This database application is developed using Model View Controller (MVC) architecture, with MySQL as database and a web based interface. We have collected and incorporated the data on filariasis in the database from Karimnagar, Chittoor, East and West Godavari districts of Andhra Pradesh, India.

Conclusion

The importance of this database is to store the collected data, retrieve the information and produce various combinational reports on filarial aspects which in turn will help the public health officials to understand the burden of disease in a particular locality. This information is likely to have an imperative role on decision making for effective control of filarial disease and integrated vector management operations.  相似文献   
982.
Quantitative RT-PCR can be a very sensitive and powerful technique for measuring differential gene expression. Changes in gene expression induced by abiotic stresses are complex and multifaceted, which make determining stably expressed genes for data normalization difficult. To identify the most suitable reference genes for abiotic stress studies in soybean, 13 candidate genes collected from literature were evaluated for stability of expression under dehydration, high salinity, cold and ABA (abscisic acid) treatments using delta CT and geNorm approaches. Validation of reference genes indicated that the best reference genes are tissue- and stress-dependent. With respect to dehydration treatment, the Fbox/ABC, Fbox/60s gene pairs were found to have the highest expression stability in the root and shoot tissues of soybean seedlings, respectively. Fbox and 60s genes are the most suitable reference genes across dehydrated root and shoot tissues. Under salt stress the ELF1b/IDE and Fbox/ELF1b are the most stably expressed gene pairs in roots and shoots, respectively, while 60s/Fbox is the best gene pair in both tissues. For studying cold stress in roots or shoots, IDE/60s and Fbox/Act27 are good reference gene pairs, respectively. With regard to gene expression analysis under ABA treatment in either roots, shoots or across these tissues, 60s/ELF1b, ELF1b/Fbox and 60s/ELF1b are the most suitable reference genes, respectively. The expression of ELF1b/60s, 60s/Fbox and 60s/Fbox genes was most stable in roots, shoots and both tissues, respectively, under various stresses studied. Among the genes tested, 60s was found to be the best reference gene in different tissues and under various stress conditions. The highly ranked reference genes identified from this study were proved to be capable of detecting subtle differences in expression rates that otherwise would be missed if a less stable reference gene was used.  相似文献   
983.
984.
Premature infants are frequently exposed to aminoglycoside antibiotics. Novel urinary biomarkers may provide a non-invasive means for the early identification of aminoglycoside-related proximal tubule renal toxicity, to enable adjustment of treatment and identification of infants at risk of long-term renal impairment. In this proof-of-concept study, urine samples were collected from 41 premature neonates (≤32 weeks gestation) at least once per week, and daily during courses of gentamicin, and for 3 days afterwards. Significant increases were observed in the three urinary biomarkers measured (Kidney Injury Molecule-1 (KIM-1), Neutrophil Gelatinase-associated Lipocalin (NGAL), and N-acetyl-β-D-glucosaminidase (NAG)) during treatment with multiple courses of gentamicin. When adjusted for potential confounders, the treatment effect of gentamicin remained significant only for KIM-1 (mean difference from not treated, 1.35 ng/mg urinary creatinine; 95% CI 0.05-2.65). Our study shows that (a) it is possible to collect serial urine samples from premature neonates, and that (b) proximal tubule specific urinary biomarkers can act as indicators of aminoglycoside-associated nephrotoxicity in this age group. Further studies to investigate the clinical utility of novel urinary biomarkers in comparison to serum creatinine need to be undertaken.  相似文献   
985.
We describe a novel, minimally invasive laser technology for skin rejuvenation by creating isolated microscopic lesions within tissue below the epidermis using laser induced optical breakdown. Using an in‐house built prototype device, tightly focused near‐infrared laser pulses are used to create optical breakdown in the dermis while leaving the epidermis intact, resulting in lesions due to cavitation and plasma explosion. This stimulates a healing response and consequently skin remodelling, resulting in skin rejuvenation effects. Analysis of ex‐vivo and in‐vivo treated human skin samples successfully demonstrated the safety and effectiveness of the microscopic lesion creation inside the dermis. Treatments led to mild side effects that can be controlled by small optimizations of the optical skin contact and treatment depth within the skin. The histological results from a limited panel test performed on five test volunteers show evidence of microscopic lesion creation and new collagen formation at the sites of the optical breakdown. This potentially introduces a safe, breakthrough treatment procedure for skin rejuvenation without damaging the epidermis with no or little social down‐time and with efficacy comparable to conventional fractional ablative techniques. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
986.
Background: Leukaemia is a heterogeneous disease in which haematopoietic progenitor cells acquire genetic lesions that lead to a block in differentiation, increased self-renewal, and unregulated proliferation. The enzyme 5,10-methylenetetrahydrofolate reductase (MTHFR), involved in folate metabolism, plays a crucial role in cells because folate availability is important for DNA integrity. The aim of this case–control study was to evaluate the association of the C677T MTHFR gene polymorphism with acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML) and chronic lymphocytic leukaemia (CLL). Materials and methods: A total of 275 leukaemia cases – including AML (n = 112), ALL (n = 81), CML (n = 43), CLL (n = 39) – and 251 age/sex-matched healthy control individuals participated in this study. MTHFR C677T polymorphisms in the cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Results: The average MTHFR 677CC, 677CT, 677TT genotype frequencies of total leukaemia cases were 68.73%, 19.64%, and 11.64% in cases, and 71.71%, 24.30%, and 3.98% in healthy controls, respectively. The average frequency of the MTHFR 677T allele was 21.45% among the cases compared to 16.13% among the controls. Conclusions: In the present case–control study we have observed a higher frequency of the MTHFR 677TT genotype in cases of leukaemia (AML, ALL, CML and CLL) as compared with controls; this might be due to ethnic and geographic variation. As per our findings, although the frequency of the MTHFR 677T allele is moderately high in AML, ALL and CLL, no statistically significant association was found; on the other hand statistically significant association was found in the context of CML cases.  相似文献   
987.
Twenty genotypes of Jatropha collected from diverse eco-geographic regions from the states of Chhattisgarh (3), Andhra Pradesh (12), Rajasthan (4) and Uttarakhand (1) of India were subjected to elevated CO2 conditions. All the genotypes showed significant difference (p < 0.05 and 0.01) in the phenotypic traits in both the environments (elevated and ambient) and genotype x environment interaction. Among the physiological traits recorded, maximum photosynthetic rate was observed in IC565048 (48.8 μmol m−2 s−1) under ambient controlled conditions while under elevated conditions maximum photosynthetic rate was observed in IC544678 (41.3 μmol m−2 s−1), and there was no significant difference in the genotype x environment interaction. Stomatal conductance (Gs) emerged as the key factor as it recorded significant difference among the genotypes, between the environments and also genotype x environment interaction. The Gs and transpiration (E) recorded a significant decline in the genotypes under the elevated CO2 condition over the ambient control. Under elevated CO2 conditions, the minimum values recorded for Gs and E were 0.03 mmol m−2 s−1 and 0.59 mmol m−2 s−1 respectively in accession IC565039, while the maximum values for Gs and E were 1.8 mmol m−2 s−1 and 11.5 mmol m−2 s−1 as recorded in accession IC544678. The study resulted in the identification of potential climate ready genotypes viz. IC471314, IC544654, IC541634, IC544313, and IC471333 for future use.  相似文献   
988.
Although olfaction could play a crucial role in underwater habitats by allowing fish to sense a variety of nonvolatile chemical signals, the importance of olfaction in species-rich cichlids is still controversial. In particular, examining whether cichlids rely on olfaction for reproduction is of primary interest to understand the mechanisms of speciation. In the present study, we explored the V1R (also known as ora) genes, which are believed to encode reproductive pheromone receptors in fish, in the genomes of Lake Victoria cichlids. By screening a bacterial artificial chromosome library, we identified all six intact V1R genes (V1R1 to V1R6) that have been reported in other teleost fish. Furthermore, RT-PCR and in situ hybridization analyses showed that all of the V1R genes were expressed in the olfactory epithelium, indicating that these receptors are functional in cichlids. These observations indicate that cichlids use V1R-mediated olfaction in some ways for their social behaviors.  相似文献   
989.
Shetty SR  Mishra C  Shetty P  Kaur A  Babu S 《Gerodontology》2012,29(2):e1133-e1135
Schwannoma also known as neurilemmoma is a benign tumour derived from schwann cells and is relatively rare in occurrence. Only 1% of the schwannomas in the head and neck region occur at intra-oral sites. Schwannomas usually occur during the third or fourth decades of life and the tongue is the most common intra-oral site. A case of intra-oral schwannoma in a 70-year-old female in the region of hard palate is described which is extremely rare.  相似文献   
990.
S4 is a paradigm of ribosomal proteins involved in multifarious activities both within and outside the ribosome. For a detailed biochemical and structural investigations of eukaryotic S4, the wheat S4 gene has been cloned and expressed in Escherichia coli, and the protein purified to a high degree of homogeneity. The 285-residue recombinant protein containing an N-terminal His(6) tag along with fourteen additional residues derived from the cloning vector is characterized by a molecular mass of 31981.24 Da. The actual sequence of 265 amino acids having a molecular mass of 29931 Da completely defines the primary structure of wheat S4. Homology modeling shows a bi-lobed protein topology arising from folding of the polypeptide into two domains, consistent with the fold topology of prokaryotic S4. The purified protein is stable and folded since it can be reversibly unfolded in guanidinium hydrochloride, and is capable of hydrolyzing cysteine protease-specific peptide-based fluorescence substrates, including Ac-DEVD-AFC (N-acetyl-Asp-Glu-Val-Asp-7-amino-4-trifluoromethylcoumarin) and Z-FR-AMC (N-CBZ-Phe-Arg-aminomethylcoumarin).  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