全文获取类型
收费全文 | 111991篇 |
免费 | 1318篇 |
国内免费 | 838篇 |
出版年
2023年 | 174篇 |
2022年 | 224篇 |
2021年 | 775篇 |
2020年 | 444篇 |
2019年 | 485篇 |
2018年 | 12296篇 |
2017年 | 11053篇 |
2016年 | 8112篇 |
2015年 | 1543篇 |
2014年 | 1528篇 |
2013年 | 1992篇 |
2012年 | 5917篇 |
2011年 | 14233篇 |
2010年 | 12788篇 |
2009年 | 8962篇 |
2008年 | 10652篇 |
2007年 | 12179篇 |
2006年 | 1038篇 |
2005年 | 1195篇 |
2004年 | 1535篇 |
2003年 | 1479篇 |
2002年 | 1199篇 |
2001年 | 583篇 |
2000年 | 455篇 |
1999年 | 295篇 |
1998年 | 119篇 |
1997年 | 103篇 |
1996年 | 88篇 |
1995年 | 85篇 |
1994年 | 67篇 |
1993年 | 94篇 |
1992年 | 183篇 |
1991年 | 191篇 |
1990年 | 134篇 |
1989年 | 106篇 |
1988年 | 160篇 |
1987年 | 121篇 |
1986年 | 85篇 |
1985年 | 93篇 |
1984年 | 95篇 |
1983年 | 71篇 |
1982年 | 51篇 |
1981年 | 52篇 |
1980年 | 47篇 |
1979年 | 62篇 |
1978年 | 40篇 |
1977年 | 44篇 |
1975年 | 42篇 |
1972年 | 277篇 |
1971年 | 290篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
991.
Nilesh Kumar Khatediya Dipak Vrajlal Parmar Mahesh Kumar Mahatma Manish Pareek 《Archives Of Phytopathology And Plant Protection》2013,46(9-10):530-549
AbstractFungal infections cause several metabolic changes to the plants, which can affect its physiology and survival in various ways. In the present study, we have analysed various phenolic compounds and activity of oxidative enzymes in healthy and Sclerotium rolfsii-infected groundnut genotypes. Increased phenolics content and higher activity of oxidative enzymes was observed in the tolerant genotype (CS 19, GG 16) followed by susceptible genotype (GG 20, TG 37A). Among the phenolic compounds tested, chlorogenic acid content has increased greatly in leaf, stem and root of infected tolerant genotypes compared to the respective controls. In vitro growth of S. rolfsii showed significant inhibition at concentrations 500 and 1000 µg/mL of phenolic compounds in the radial growth inhibition assay. These results have strongly suggested that, higher accumulation of chlorogenic acid could be an important factor in imparting resistance and protecting groundnut against S. rolfsii infection in tolerant genotypes. 相似文献
992.
Ajay Kumar D.M. Pandey Thomson Abraham Jacob Mathew Padma Ramachandran 《Archives Of Phytopathology And Plant Protection》2013,46(6):710-720
Tapping panel dryness (TPD) syndrome affecting rubber tree (Hevea brasiliensis) is known to reduce natural latex production. Its aetiology remains ambiguous despite long years of research. A low molecular weight RNA similar to viroid RNA was isolated from TPD-affected samples of rubber trees. In the present study, a modified return-polyacrylamide gel electrophoresis procedure was standardised. The viroid-like low molecular weight (LMW) RNA was found associated with leaf, bark and root tissues and rubber seedlings. The technique was employed to detect LMW RNA in different clones of rubber planted in different locations and in bud-grafted plants. The LMW RNA isolated from TPD-affected trees was found infectious on seedlings of tomato cv Pusa Ruby. The LMW RNA was reisolated from symptomatic tomato leaves but not from control plants. This is for the first time that a biotic agent, a viroid RNA, is found consistently associated with the syndrome. The technology developed can be useful to demonstrate the onset of TPD in untapped trees in the absence of other methods such as nucleic acid hybridisation. 相似文献
993.
Kumar Nishanth Bala Nambisan R. Ramya Chellapan Mohandas 《Archives Of Phytopathology And Plant Protection》2013,46(6):721-731
A specific symbiotic Bacillus sp. isolated from a rhabditid entomopathogenic nematode, Rhabditis (Oscheius) sp. was found to produce large number of bioactive compounds. The present study was conducted to determine the effect of carbon and nitrogen sources for the production of antimicrobial substances by Bacillus sp. The yield of the crude antimicrobial substances and antimicrobial activity against the test micro-organism also differed significantly when carbon and nitrogen sources in the fermentation media were changed. The antifungal activity was significantly high in yeast extract plus fructose (46.5?±?2.12?mm) followed by yeast extract plus maltose, beef extract plus fructose and meat infusion plus glucose. High pressure liquid chromatography analysis of the crude antimicrobial substances revealed different peaks with different retention time indicating that they produced different compounds. When the carbon source was not included in the fermentation media, the antimicrobial production was substantially reduced. The results indicate that carbon source in the fermentation media plays a vital role in the production of antifungal substances. It is concluded that yeast extract and fructose as nitrogen and carbon sources produced maximum activity, which can effectively control the blue mould caused by Penicillium expansum in apples and pears. 相似文献
994.
M. Kavino N. Kumar T. Damodaran S. Harish D. Saravanakumar 《Archives Of Phytopathology And Plant Protection》2013,46(11):1069-1078
Abstract Panama disease of banana (Musa spp) caused by the fungus Fusarium oxysporum f. sp. Cubense (FOC), is a serious constraint both to the commercial production of banana and cultivation for subsistence agriculture. Chemical control is not economically effective and is also hazardous to the environment and human health. Breeding for disease resistance is an alternative strategy, which leads to the development of resistance clones. Field evaluation is the most reliable method of screening for disease resistance, but it is demanding in terms of cost, manpower and space requirements. Another approach of screening hybrids at the sucker's stage (planting material) through biochemical markers has been found to be effective in early identification of resistant hybrids. The resistance mechanisms involving the role of phenol, PAL, oxidative enzymes like peroxidase (PO), polyphenol oxidase (PPO), superoxide dismutase (SOD), catalase and PR-proteins like chitinase, β-1-3 glucanase were studied and they showed relatively higher activity in resistant hybrids than susceptible hybrids. Isozyme analysis of peroxidase (PO) and polyphenol oxidase (PPO) was also carried out in cultivars and hybrids, which revealed the induction of specific isoforms in the resistant hybrids upon challenge inoculation. This could be a useful tool for early identification of F. oxysporum f. sp. cubense resistance banana clones. 相似文献
995.
Sayed Sartaj Sohrab Zeenat Mirza Sajjad Karim Debashis Rana Adel M. Abuzenadah Adeel G. Chaudhary 《Archives Of Phytopathology And Plant Protection》2013,46(9):1047-1053
Leaf curl and yellow vein mosaic viral disease is the major constraint on okra (Abelmoschus esculentus L.) production in India. Amplified fragment sequence of DNA-β showed highest similarity of 91.7% with Bhendi yellow vein mosaic virus-Tamil Nadu (AJ308425, NC_003405) and lowest similarity of 48.5% with OKLCV (NC_004093), whereas coat protein specific amplified sequence showed highest homology with isolate of Madurai, Haryana, Ludhiana and lowest homology of 92% with Mesta yellow vein mosaic Bahraich virus (MYVMBV) (EU360303). The results obtained in the present study confirm that both the viral diseases of okra reported in southern India are caused by a begomovirus associated with DNA-β in which the plants show leaf curl symptoms and never develops yellow vein mosaic and those plants which show yellow vein mosaic, never develops leaf curl symptoms even in the same rows and field. The okra leaf curl is an emerging virus disease in India. 相似文献
996.
David B. Kantor Cameron D. Palmer Taylor R. Young Yan Meng Zofia K. Gajdos Helen Lyon Alkes L. Price Samuela Pollack Stephanie J. London Laura R. Loehr Lewis J. Smith Rajesh Kumar David R. Jacobs Jr. Marcy F. Petrini George T. O’Connor Wendy B. White George Papanicolaou Kristin M. Burkart Susan R. Heckbert R. Graham Barr Joel N. Hirschhorn 《Human genetics》2013,132(9):1039-1047
Asthma originates from genetic and environmental factors with about half the risk of disease attributable to heritable causes. Genome-wide association studies, mostly in populations of European ancestry, have identified numerous asthma-associated single nucleotide polymorphisms (SNPs). Studies in populations with diverse ancestries allow both for identification of robust associations that replicate across ethnic groups and for improved resolution of associated loci due to different patterns of linkage disequilibrium between ethnic groups. Here we report on an analysis of 745 African-American subjects with asthma and 3,238 African-American control subjects from the Candidate Gene Association Resource (CARe) Consortium, including analysis of SNPs imputed using 1,000 Genomes reference panels and adjustment for local ancestry. We show strong evidence that variation near RAD50/IL13, implicated in studies of European ancestry individuals, replicates in individuals largely of African ancestry. Fine mapping in African ancestry populations also refined the variants of interest for this association. We also provide strong or nominal evidence of replication at loci near ORMDL3/GSDMB, IL1RL1/IL18R1, and 10p14, all previously associated with asthma in European or Japanese populations, but not at the PYHIN1 locus previously reported in studies of African-American samples. These results improve the understanding of asthma genetics and further demonstrate the utility of genetic studies in populations other than those of largely European ancestry. 相似文献
997.
Vinay Singh Tanwar Mandeep P. Chand Jitender Kumar Gaurav Garg Sandeep Seth Ganesan Karthikeyan Shantanu Sengupta 《Gene》2013
Vitamin B12 is an essential micronutrient synthesized by microorganisms. Mammals including humans have evolved ways for transport and absorption of this vitamin. Deficiency of vitamin B12 (either due to low intake or polymorphism in genes involved in absorption and intracellular transport of this vitamin) has been associated with various complex diseases. Genome-wide association studies have recently identified several common single nucleotide polymorphisms (SNPs) in fucosyl transferase 2 gene (FUT2) to be associated with levels of vitamin B12—the strongest association was with a non-synonymous SNP rs602662 in this gene. In the present study, we attempted to replicate the association of this SNP (rs602662) in an Indian population since a significant proportion has been reported to have low levels of vitamin B12 in this population. A total of 1146 individuals were genotyped for this SNP using a single base extension method and association with levels of vitamin B12 was assessed in these individuals. Regression analysis was performed to analyze the association considering various confounding factors like for age, sex, diet, hypertension, diabetes mellitus and coronary artery disease status. We found that the SNP rs602662 was significantly associated with the levels of vitamin B12 (p value < 0.0001). We also found that individuals adhering to a vegetarian diet with GG (homozygous major genotype) have significantly lower levels of vitamin B12 in these individuals. Thus, our study reveals that vegetarian diet along with polymorphism in the FUT2 gene may contribute significantly to the high prevalence of vitamin B12 deficiency in India. 相似文献
998.
Anuran diversity study was conducted for one year between June 2008 and August 2009 at Durgapur, an industrial city of West Bengal, India. Nine species under four families of the Order Anura were found to occur in Durgapur. They have a wide range of habitat preference like permanent or temporary aquatic bodies, human residential area, forested areas, termite nest, tree hole, under spaces of logs and so forth. Of the nine sp. 8 were confined to Amarabati pond (site-I), 5 were confined to Durgapur Government College campus (site-II) and 7 were confined at Fuljhore (site-III) of Durgapur. Analysis of the collected data on the anuran community of the study area revealed Shannon–Wiener species diversity index minimum (1.312) at site-II and maximum (1.938) at site-III. In contrast Margalef richness index value was minimum (0.627) at site-II and maximum (1.424) at site-III. 相似文献
999.
Bisu Singh Nirmal Kumar Bera Tapas Kumar Chaudhuri 《Proceedings of the Zoological Society》2013,66(1):8-13
The present study was carried out to ascertain the birth order as a risk factor for schizophrenia on the basis of HLA genetics. India born schizophrenic patients of Siliguri, West Bengal who attended Outpatient Department of Psychiatry, North Bengal Medical College and Hospital were included in the study. After longitudinal follow up of 136 patients and 150 controls matched in age, sex and ethnicity were screened for the study. The typing of HLA was done by PCR-SSP method. The results showed a significantly increased frequency of HLA*A3 among the patients. Further, birth order was studied among HLA*A3 positive 108 patients and 41 controls. Although, results indicated higher incidence of schizophrenia among second children irrespective of sex but it was not found to be statistically significant. However, when the birth order of male and female patients was analyzed separately, a significant decreased incidence of schizophrenia was observed among the third female child. The findings do not corroborate with the earlier findings of association of birth order with schizophrenia. 相似文献
1000.