全文获取类型
收费全文 | 1469篇 |
免费 | 78篇 |
国内免费 | 12篇 |
专业分类
1559篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 28篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 49篇 |
2017年 | 46篇 |
2016年 | 63篇 |
2015年 | 55篇 |
2014年 | 69篇 |
2013年 | 93篇 |
2012年 | 114篇 |
2011年 | 119篇 |
2010年 | 58篇 |
2009年 | 43篇 |
2008年 | 54篇 |
2007年 | 73篇 |
2006年 | 54篇 |
2005年 | 47篇 |
2004年 | 36篇 |
2003年 | 42篇 |
2002年 | 38篇 |
2001年 | 33篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 16篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1992年 | 19篇 |
1991年 | 23篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1971年 | 11篇 |
1970年 | 8篇 |
1967年 | 6篇 |
排序方式: 共有1559条查询结果,搜索用时 15 毫秒
951.
Diawo Diallo Amadou A. Sall Cheikh T. Diagne Oumar Faye Ousmane Faye Yamar Ba Kathryn A. Hanley Michaela Buenemann Scott C. Weaver Mawlouth Diallo 《PloS one》2014,9(10)
Background
Zika virus (ZIKV; genus Flavivirus, family Flaviviridae) is maintained in a zoonotic cycle between arboreal Aedes spp. mosquitoes and nonhuman primates in African and Asian forests. Spillover into humans has been documented in both regions and the virus is currently responsible for a large outbreak in French Polynesia. ZIKV amplifications are frequent in southeastern Senegal but little is known about their seasonal and spatial dynamics. The aim of this paper is to describe the spatio-temporal patterns of the 2011 ZIKV amplification in southeastern Senegal.Methodology/Findings
Mosquitoes were collected monthly from April to December 2011 except during July. Each evening from 18∶00 to 21∶00 hrs landing collections were performed by teams of 3 persons working simultaneously in forest (canopy and ground), savannah, agriculture, village (indoor and outdoor) and barren land cover sites. Mosquitoes were tested for virus infection by virus isolation and RT-PCR. ZIKV was detected in 31 of the 1,700 mosquito pools (11,247 mosquitoes) tested: Ae. furcifer (5), Ae. luteocephalus (5), Ae. africanus (5), Ae. vittatus (3), Ae. taylori, Ae. dalzieli, Ae. hirsutus and Ae. metallicus (2 each) and Ae. aegypti, Ae. unilinaetus, Ma. uniformis, Cx. perfuscus and An. coustani (1 pool each) collected in June (3), September (10), October (11), November (6) and December (1). ZIKV was detected from mosquitoes collected in all land cover classes except indoor locations within villages. The virus was detected in only one of the ten villages investigated.Conclusions/Significance
This ZIKV amplification was widespread in the Kédougou area, involved several mosquito species as probable vectors, and encompassed all investigated land cover classes except indoor locations within villages. Aedes furcifer males and Aedes vittatus were found infected within a village, thus these species are probably involved in the transmission of Zika virus to humans in this environment. 相似文献952.
953.
954.
955.
956.
Background
Analysis of pollen grains reveals valuable information on biology, ecology, forensics, climate change, insect migration, food sources and aeroallergens. Vibrational (infrared and Raman) spectroscopies offer chemical characterization of pollen via identifiable spectral features without any sample pretreatment. We have compared the level of chemical information that can be obtained by different multiscale vibrational spectroscopic techniques.Methodology
Pollen from 15 different species of Pinales (conifers) were measured by seven infrared and Raman methodologies. In order to obtain infrared spectra, both reflectance and transmission measurements were performed on ground and intact pollen grains (bulk measurements), in addition, infrared spectra were obtained by microspectroscopy of multigrain and single pollen grain measurements. For Raman microspectroscopy measurements, spectra were obtained from the same pollen grains by focusing two different substructures of pollen grain. The spectral data from the seven methodologies were integrated into one data model by the Consensus Principal Component Analysis, in order to obtain the relations between the molecular signatures traced by different techniques.Results
The vibrational spectroscopy enabled biochemical characterization of pollen and detection of phylogenetic variation. The spectral differences were clearly connected to specific chemical constituents, such as lipids, carbohydrates, carotenoids and sporopollenins. The extensive differences between pollen of Cedrus and the rest of Pinaceae family were unambiguously connected with molecular composition of sporopollenins in pollen grain wall, while pollen of Picea has apparently higher concentration of carotenoids than the rest of the family. It is shown that vibrational methodologies have great potential for systematic collection of data on ecosystems and that the obtained phylogenetic variation can be well explained by the biochemical composition of pollen. Out of the seven tested methodologies, the best taxonomical differentiation of pollen was obtained by infrared measurements on bulk samples, as well as by Raman microspectroscopy measurements of the corpus region of the pollen grain. Raman microspectroscopy measurements indicate that measurement area, as well as the depth of focus, can have crucial influence on the obtained data. 相似文献957.
Tung Hoang Thanh Bao Huynh Gia Cuong Do Manh Ngan Ha Thi My Hien Vu Thi Luan Vu Quoc Vinh Bui Van The Phuong Hoang Thi Nhu Nam Nguyen Ba Trieu Le Ngoc Truong Nguyen Khoa Hoang Pham Nguyen Duc Nhut Duong Tan 《In vitro cellular & developmental biology. Plant》2021,57(6):897-906
In Vitro Cellular & Developmental Biology - Plant - Micropropagation has proven to be an effective method for large-scale plant production in a short time and a useful tool for plant breeding.... 相似文献
958.
Karpova E. P. Ablyazov E. R. Kurshakov S. V. Chesnokova I. I. Dinh Cu Nguyen Hai Truong Ba 《Journal of Ichthyology》2021,61(4):554-563
Journal of Ichthyology - Data on species composition and frequency of occurrence of the grenadier anchovies (Coilia) spp. is reported from the Mekong Delta (Vietnam) based on fieldwork materials.... 相似文献
959.
960.
Beatriz Sanchez-Correa Juan M. Bergua Carmen Campos Inmaculada Gayoso Maria Jose Arcos Helena Bañas Sara Morgado Javier G. Casado Rafael Solana Raquel Tarazona 《Cytokine》2013,61(3):885-891
BackgroundSeveral evidences support the existence of cytokine deregulation in acute myeloid leukemia (AML) patients that may be associated with pathogenesis, disease progression and patient survival.MethodsIn the present study, we analyzed plasma levels of pro- and anti-inflammatory cytokines in AML patients and age-matched healthy donors. TNF-α, IL-6, IL-1β, IL-2, IFN-γ, IL-17A, IL-12p70, IL-8, IL-10, IL-4 and IL-5 were analyzed using fluorescent bead-based technology and TGF-β by ELISA technique. Because age-associated differences in cytokine profiles have been described, patients and healthy individuals were divided into two age groups: up to 65 years and over 65 years.ResultsOur results showed that plasma TNF-α, IL-6 and IL-10 levels were higher in AML patients from both groups of age. IL-8 was increased in AML patients less than 65 years while the plasma concentrations of IL-4, IL-5 and IL-12p70 were significantly higher only in elderly AML patients compared with aged-matched healthy controls. Moreover, plasma levels of IL-6 and IL-10 were associated with patient survival and event-free survival.ConclusionsAn aberrant production of the pro-inflammatory cytokines IL-6 and TNF-α and the anti-inflammatory cytokine IL-10 is observed in AML patients. Low levels of IL-6 and high levels of IL-10 represent favorable prognostic factors for survival in AML patients. These results support the idea that cytokine deregulation may be useful as a marker for predicting clinical evolution in AML patients. 相似文献