全文获取类型
收费全文 | 6684篇 |
免费 | 379篇 |
国内免费 | 20篇 |
专业分类
7083篇 |
出版年
2024年 | 11篇 |
2023年 | 94篇 |
2022年 | 247篇 |
2021年 | 354篇 |
2020年 | 330篇 |
2019年 | 477篇 |
2018年 | 367篇 |
2017年 | 258篇 |
2016年 | 345篇 |
2015年 | 370篇 |
2014年 | 455篇 |
2013年 | 580篇 |
2012年 | 538篇 |
2011年 | 538篇 |
2010年 | 284篇 |
2009年 | 245篇 |
2008年 | 267篇 |
2007年 | 273篇 |
2006年 | 238篇 |
2005年 | 196篇 |
2004年 | 146篇 |
2003年 | 106篇 |
2002年 | 97篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 14篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1976年 | 3篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1963年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有7083条查询结果,搜索用时 15 毫秒
991.
A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r2 = 0.9955) with relative standard deviations (n = 4) in the range 1.0-3.5%. The detection limit (3sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(II), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO4(2-), PO4(3-), NO3-, NO2-, F- and SO3(2-)) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005 - 0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed. 相似文献
992.
Christopher J Lelliott Gema Medina-Gomez Natasa Petrovic Adrienn Kis Helena M Feldmann Mikael Bjursell Nadeene Parker Keira Curtis Mark Campbell Ping Hu Dongfang Zhang Sheldon E Litwin Vlad G Zaha Kimberly T Fountain Sihem Boudina Mercedes Jimenez-Linan Margaret Blount Miguel Lopez Aline Meirhaeghe Mohammad Bohlooly-Y Leonard Storlien Maria Strmstedt Michael Snaith Matej Orei
E. Dale Abel Barbara Cannon Antonio Vidal-Puig 《PLoS biology》2006,4(11)
993.
994.
995.
The Major Component of IκBα Proteolysis Occurs Independently of the Proteasome Pathway in Respiratory Syncytial Virus-Infected Pulmonary Epithelial Cells 下载免费PDF全文
996.
The diagnostic and prognostic value of circulating microRNAs in coronary artery disease: A novel approach to disease diagnosis of stable CAD and acute coronary syndrome 下载免费PDF全文
997.
998.
Mohammad Firoze Quamar Sheikh Nawaz Ali Sundeep Kumar Pandita Yudhbir Singh 《Grana》2018,57(5):364-376
Twenty five surface samples/moss cushions were collected for palynological analysis from open areas of Reasi District, Jammu and Kashmir (India). These samples were used to investigate the relationships between extant vegetation and modern pollen spectra, which serve as modern analogue for the reliable ecological interpretation of fossil pollen records. The present vegetation in the region comprises tropical dry deciduous forests and subtropical pine forests with scattered stands of oak. The pollen analysis reveals that Pinus sp. (average 69% in the pollen assemblages), amongst the conifers, dominates the pollen rain, which can be attributed to its high pollen productivity and exceptional pollen dispersal efficiency. Cedrus sp. and Podocarpus sp. pollen contribute with an average of 16 and 5% to the total pollen rain. Other conifers such as Picea sp., Abies sp., Juniperus sp. and Tsuga sp., as well as broad-leaved taxa such as Quercus sp., Alnus sp., Betula sp., Carpinus sp., Corylus sp., Juglans sp., Ulmus sp., Salix sp., Elaeocarpus sp., Mallotus sp. and Aesculus sp., have lower averages of 1 to 4.5% in the total pollen rain which could be either due to their poor pollen dispersal efficiency or to the poor preservation in the samples. Tubuliflorae (average 25%), Poaceae (average 6.26%), Cerealia and other crop plants (average 7.68%) are other prominent taxa in the pollen rain. The nearly complete absence of members of tropical dry deciduous forests in the pollen spectra likely is due to the fact that most species in this vegetation type are not wind pollinated. 相似文献
999.
Mahboobeh Ziaei Mostafa Motallebi Mohammad Reza Zamani Nasim Zarin Panjeh Zahra Moghaddassi Jahromi 《Journal of plant biochemistry and biotechnology.》2016,25(4):358-366
Canola (Brassica napus L.), an agro-economically important crop in the world, is sensitive to many fungal pathogens. One strategy to combat fungal diseases is genetic engineering through transferring genes encoding the pathogenesis-related (PR) proteins such as chitinase which cause the chitin degradation of fungal cell wall. Chitinase Chit42 from Trichoderma atroviride (PTCC5220) plays an important role in biocontrol and has high antifungal activity against a wide range of phytopathogenic fungi. This enzyme lacks a chitin binding domain (ChBD) which is involved in binding activity to insoluble chitin. In the present study, we investigated the effect of chitin binding domain fused to Chit42 when compared with native Chit42. These genes were over-expressed under the CaMV35S promoter in B. napus, R line Hyola 308. Transformation of cotyledonary petioles was achieved by pBISM2 and pBIKE1 constructs containing chimeric and native Chit42 genes respectively, via Agrobacterium method. The insertion of transgenes in T0 generation was verified through polymerase chain reaction (PCR) and Southern blot analysis. Antifungal activity of expressed chitinase in transgenic plants was also investigated by bioassays. The transgenic canola expressing chimeric chitinase showed stronger inhibition against phytopathogenic fungi that indicates the role of chitin binding domain. 相似文献
1000.
Ariyo Shahin-jafari Mansour Bayat Mohammad Hassan Shahhosseiny Parviz Tajik Shahla Roudbar-mohammadi 《Saudi Journal of Biological Sciences》2016,23(3):426-433
Over the last decade, communication industries have witnessed a tremendous expansion, while, the biological effects of electromagnetic waves have not been fully elucidated. Current study aimed at evaluating the mutagenic effect of long-term exposure to 900-MHz radiation on alpha-Int1 gene sequences of Candida albicans. A standard 900 MHz radiation generator was used for radiation. 10 ml volumes from a stock suspension of C. albicans were transferred into 10 polystyrene tubes. Five tubes were exposed at 4 °C to a fixed magnitude of radiation with different time periods of 10, 70, 210, 350 and 490 h. The other 5 tubes were kept far enough from radiation. The samples underwent genomic DNA extraction. PCR amplification of alpha-Int1 gene sequence was done using one set of primers. PCR products were resolved using agarose gel electrophoresis and the nucleotide sequences were determined. All samples showed a clear electrophoretic band around 441 bp and further sequencing revealed the amplified DNA segments are related to alpha-Int1 gene of the yeast. No mutations in the gene were seen in radiation exposed samples. Long-term exposure of the yeast to mobile phone radiation under the above mentioned conditions had no mutagenic effect on alpha-Int1 gene sequence. 相似文献