全文获取类型
收费全文 | 18469篇 |
免费 | 920篇 |
国内免费 | 27篇 |
专业分类
19416篇 |
出版年
2024年 | 31篇 |
2023年 | 164篇 |
2022年 | 375篇 |
2021年 | 703篇 |
2020年 | 414篇 |
2019年 | 441篇 |
2018年 | 643篇 |
2017年 | 602篇 |
2016年 | 784篇 |
2015年 | 886篇 |
2014年 | 1128篇 |
2013年 | 1547篇 |
2012年 | 1630篇 |
2011年 | 1434篇 |
2010年 | 830篇 |
2009年 | 728篇 |
2008年 | 840篇 |
2007年 | 813篇 |
2006年 | 681篇 |
2005年 | 617篇 |
2004年 | 499篇 |
2003年 | 414篇 |
2002年 | 372篇 |
2001年 | 307篇 |
2000年 | 279篇 |
1999年 | 254篇 |
1998年 | 100篇 |
1997年 | 76篇 |
1996年 | 82篇 |
1995年 | 77篇 |
1994年 | 57篇 |
1993年 | 56篇 |
1992年 | 152篇 |
1991年 | 143篇 |
1990年 | 113篇 |
1989年 | 85篇 |
1988年 | 126篇 |
1987年 | 97篇 |
1986年 | 80篇 |
1985年 | 81篇 |
1984年 | 81篇 |
1983年 | 46篇 |
1982年 | 40篇 |
1981年 | 47篇 |
1980年 | 43篇 |
1979年 | 56篇 |
1978年 | 35篇 |
1977年 | 43篇 |
1976年 | 31篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Sunil Kumar 《Archives Of Phytopathology And Plant Protection》2016,49(1-4):59-63
Pepper seed samples were tested for the infection of tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV) by enzyme linked immunosorbent assay (ELISA). Out of 26 pepper seed samples tested, 17 were infected with TMV and ToMV in ELISA. About 34.7% of pepper seed samples were found to be healthy. Infections of TMV or ToMV were recorded to be 61.53% and 11.5%, respectively of the total tested seed samples. 相似文献
962.
Soumen Chandra Dipranjan Laha Arindam Pramanik Angshuman Ray Chowdhuri Parimal Karmakar Sumanta Kumar Sahu 《Luminescence》2016,31(1):81-87
Highly fluorescent nitrogen and phosphorus‐doped carbon dots with a quantum yield 59% have been successfully synthesized from citric acid and di‐ammonium hydrogen phosphate by single step hydrothermal method. The synthesized carbon dots have high solubility as well as stability in aqueous medium. The as‐obtained carbon dots are well monodispersed with particle sizes 1.5–4 nm. Owing to a good tunable fluorescence property and biocompatibility, the carbon dots were applied for intercellular sensing of Fe3+ ions as well as cancer cell imaging. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
963.
The beneficial effect of seed priming in improving critical growth stages like seed germination and early growth phases has been accepted by Plant Physiologists for many important field crops. In the present investigation, studies were made to see the effect of heavy metal stress imposed during germination using solution of HgCl2 in four different concentrations (0.0, 0.50, 0.75 and 1.00 mM) in Petri dishes on primed and non-primed seeds of wheat. Priming has been done with distilled water (hydro), Mg(NO3)2 and Ca(NO3)2 (halo) salts. Different germination parameters, such as germination percentage, radicle and plumule lengths, seedling emergence, soluble and insoluble sugar contents and activity of α-amylase in endosperm were studied at different study periods. Primed seeds increased all the germination parameters except insoluble sugar content in respect to non-primed control in the absence of HgCl2. However, the use of primed seeds has shown to overcome the inhibitory effects of heavy metal stress imposed in the form of HgCl2 solution during the period of germination. Hence, the work concludes the mitigating effects of priming under heavy metal stress. 相似文献
964.
Differential expression of carotenoid biosynthetic pathway genes in two contrasting tomato genotypes for lycopene content 总被引:1,自引:0,他引:1
965.
Mahima Bansal M. Sudhakara Reddy Anil Kumar 《Physiology and Molecular Biology of Plants》2016,22(3):407-413
Bacoside A, a major active principle of Bacopa monnieri known for its cognitive effects is a mixture of saponins like bacoside A3, bacopaside II, isomer of bacopasaponin C and bacopasaponin C. Seasonal changes in biomass and bacoside A levels in fourteen accessions of B. monnieri were evaluated after maintaining these at a common site at Thapar University campus, Patiala (30°19′36.12″N and 76°24′1.08″E) for 1 year. Harvestable biomass and total bacoside A contents varied significantly between the accessions and also in a particular accession during different seasons of the year. The maximum dry weight of plant (biomass 1.64 g) and bacoside A levels (6.82 mg/plant) were recorded in accession BM1. Harvestable biomass was highest during summer in accessions BM1 and BM7 (FW 4.2 g/plant), whereas bacoside A levels were also highest during summer and in accession BM1 (6.82 mg/plant). The lowest bacoside A level (0.06 mg/plant) was recorded in accession BM14 during winter. Principal component analysis showed that samples of summer were positively correlated with both the components suggesting an appropriate time for the harvest. 相似文献
966.
Pradip B. Ranaware Anamika Mishra Periyasamy Vijayakumar Pradeep N. Gandhale Himanshu Kumar Diwakar D. Kulkarni Ashwin Ashok Raut 《PloS one》2016,11(4)
The molecular pathogenesis of avian influenza infection varies greatly with individual bird species and virus strain. The molecular pathogenesis of the highly pathogenic avian influenza virus (HPAIV) or the low pathogenic avian influenza virus (LPAIV) infection in avian species remains poorly understood. Thus, global immune response of chickens infected with HPAI H5N1 (A/duck/India/02CA10/2011) and LPAI H9N2 (A/duck/India/249800/2010) viruses was studied using microarray to identify crucial host genetic components responsive to these infection. HPAI H5N1 virus induced excessive expression of type I IFNs (IFNA and IFNG), cytokines (IL1B, IL18, IL22, IL13, and IL12B), chemokines (CCL4, CCL19, CCL10, and CX3CL1) and IFN stimulated genes (OASL, MX1, RSAD2, IFITM5, IFIT5, GBP 1, and EIF2AK) in lung tissues. This dysregulation of host innate immune genes may be the critical determinant of the severity and the outcome of the influenza infection in chickens. In contrast, the expression levels of most of these genes was not induced in the lungs of LPAI H9N2 virus infected chickens. This study indicated the relationship between host immune genes and their roles in pathogenesis of HPAIV infection in chickens. 相似文献
967.
Cell growth and metabolite production greatly depend on the feeding of the nutrients in fed-batch fermentations. A strategy
for controlling the glucose feed rate in fed-batch baker’s yeast fermentation and a novel controller was studied. The difference
between the specific carbon dioxide evolution rate and oxygen uptake rate (Q
c − Q
o) was used as controller variable. The controller evaluated was neural network based model predictive controller and optimizer.
The performance of the controller was evaluated by the set point tracking. Results showed good performance of the controller. 相似文献
968.
Ishani Deb Priyankar Paira Abhijit Hazra Sukdeb Banerjee Pradip Kumar Dutta Nirup Bikash Mondal Sumantra Das 《Bioorganic & medicinal chemistry》2009,17(16):5782-5790
Based on an established 3D pharmacophore, a series of quinoline derivatives were synthesized. The opioidergic properties of these compounds were determined by a competitive binding assay using 125I-Dynorphine, 3H-DAMGO and 125I-DADLE for κ, μ, and δ receptors, respectively. Results showed varying degree of activities of the compounds to κ and μ opioid receptors with negligible interactions at the δ receptor. The compound, S4 was the most successful in inhibiting the two most prominent quantitative features of naloxone precipitated withdrawal symptoms - stereotyped jumping and body weight loss. Determination of IC50 of S4 revealed a greater affinity towards μ compared to κ receptor. In conclusion, quinoline derivatives of S4 like structure offer potential tool for treatment of narcotic addictions. 相似文献
969.
The population structure of An. stephensi in North-west India was studied to assess the impact of the Aravalli Hills, as a barrier to gene flow using microsatellite markers. Large and significant genetic differentiation was found along the sides of, as well as across, the Aravalli Hills as the mean FST and RST on west vs. east of the Aravalli Hills were 0.213, 0.112 and 0.179, 0.056, respectively. Similarly, across the hills, mean values of FST and RST were 0.100 and 0.094, respectively. Genetic diversity on both sides did not vary significantly. The FST values were more sensitive than RST values, indicating that genetic drift might have caused genetic differentiation between populations. A positive correlation (r = 0.0149 and 0.157, respective to FST and RST) was found between genetic differentiations and geographic distances irrespective of the hills. Low level of gene flow was found along both sides (Nm = 0.92 and 0.14; west vs. east of Aravalli Hills, respectively) as compared to across the Aravalli Hills (Nm = 2.25). It was found that the Aravalli Hills are not working as an effective barrier to gene flow for An. Stephensi, maybe because of the low average height and discontinuous hills, however, the distance is playing a major role for differentiation between populations due to active mode of dispersal of An. stephensi mosquitoes which have a short flight range. All this information should help draw the strategies for genetic control of mosquitoes using transgenic mosquitoes. 相似文献
970.
Extreme heterogeneity of Ty1-copia group retrotransposons in plants 总被引:18,自引:0,他引:18
Andrew J. Flavell Donald B. Smith Amar Kumar 《Molecular & general genetics : MGG》1992,231(2):233-242