全文获取类型
收费全文 | 4224篇 |
免费 | 206篇 |
国内免费 | 1篇 |
专业分类
4431篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 68篇 |
2021年 | 118篇 |
2020年 | 108篇 |
2019年 | 135篇 |
2018年 | 145篇 |
2017年 | 131篇 |
2016年 | 194篇 |
2015年 | 286篇 |
2014年 | 280篇 |
2013年 | 328篇 |
2012年 | 370篇 |
2011年 | 338篇 |
2010年 | 198篇 |
2009年 | 162篇 |
2008年 | 246篇 |
2007年 | 201篇 |
2006年 | 201篇 |
2005年 | 168篇 |
2004年 | 187篇 |
2003年 | 144篇 |
2002年 | 119篇 |
2001年 | 27篇 |
2000年 | 24篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1975年 | 3篇 |
1965年 | 2篇 |
1952年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有4431条查询结果,搜索用时 15 毫秒
11.
Coelho JH Ximenes NL Felippe MR Montesino LH Garbim LF Sanches AL Dalla Pria W Yamamoto PT 《Neotropical Entomology》2008,37(4):449-456
The purpose of this study was to analyze sharpshooter fauna in a five-year-old 'Westin' sweet orange orchard. Yellow sticky traps were placed on the edge of a forest, and on the periphery and inside the citrus stand. The traps were evaluated fortnightly, for three years. The most frequent species were Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg), and Oncometopia facialis (Signoret). B. xanthophis occurred more in the forest edge, especially on spring and winter. A. citrina occurred most frequently in the forest edge, especially on spring. The highest incidence of O. facialis was inside the citrus stand, on spring and summer. Other cicadellids occurred more often in the forest edge, especially on summer. A. citrina, B. xanthophis, Dilobopterus costalimai Young, and O. facialis were predominant in all places studied. A. citrina, B. xanthophis and O. facialis were super dominant, super abundant, super frequent, and constant, except inside the stand, where B. xanthophis was dominant, very abundant, very frequent, and constant. D. costalimai and Homalodisca ignorata Melichar were dominant, very abundant, and very frequent in the forest edge and in the periphery of the stand, and D. costalimai was also predominant inside the stand. Scopogonalia subolivacea (St?l) was predominant in the forest edge and inside the stand, while Plesiommata corniculata Young was predominant in the periphery (both were dominant, very abundant, very frequent, and accessory). 相似文献
12.
Mario Cesar Salinas-Carmona Adrian Geovanni Rosas-Taraco Oliverio Welsh 《Antonie van Leeuwenhoek》2012,102(3):473-480
Human diseases produced by pathogenic actinomycetes are increasing because they may be present as opportunistic infections. Some of these microbes cause systemic infections associated with immunosuppressive conditions, such as chemotherapy for cancer, immunosuppressive therapy for transplant, autoimmune conditions, and AIDS; while others usually cause localized infection in immunocompetent individuals. Other factors related to this increase in incidence are: antibiotic resistance, not well defined taxonomy, and a delay in isolation and identification of the offending microbe. Examples of these infections are systemic disease and brain abscesses produced by Nocardia asteroides or the located disease by Nocardia brasiliensis, named actinomycetoma. During the Pathogenic Actinomycetes Symposium of the 16th International Symposium on Biology of Actinomycetes (ISBA), held in Puerto Vallarta, Mexico, several authors presented recent research on the mechanisms by which N. brasiliensis modulates the immune system to survive in the host and advances in medical treatment of human actinomycetoma. Antibiotics and antimicrobials that are effective against severe actinomycetoma infections with an excellent therapeutic outcome and experimental studies of drugs that show promising bacterial inhibition in vivo and in vitro were presented. Here we demonstrate a systemic strong acquired immune response in humans and experimental mice at the same time of a local dominance of anti inflammatory cytokines environment. The pathogenic mechanisms of some actinomycetes include generation of an immunosuppressive micro environment to evade the protective immune response. This information will be helpful in understanding pathogenesis and to design new drugs for treatment of actinomycetoma. 相似文献
13.
14.
15.
dos Santos AP Bertho AL Martins Rde M Marcovistz R 《Memórias do Instituto Oswaldo Cruz》2007,102(1):117-120
The objective of this paper is to propose a protocol to analyze blood samples in yellow fever 17DD vaccinated which developed serious adverse events. We investigated whether or not the time between sample collection and sample processing could interfere in lymphocyte subset percentage, for it is often impossible to analyze blood samples immediately after collection due to transport delay from collection places to the flow cytometry facility. CD4+CD38+ T, CD8+CD38+ T, CD3+ T, CD19+ B lymphocyte subsets were analyzed by flow cytometry in nine healthy volunteers immediately after blood collection and after intervals of 24 and 48 h. The whole blood lysis method and gradient sedimentation by Histopaque were applied to isolate peripheral blood mononuclear cells for flow cytometry analyses. With the lysis method, there was no significant change in lymphocyte subset percentage between the two time intervals (24 and 48 h). In contrast, when blood samples were processed by Histopaque gradient sedimentation, time intervals for sample processing influenced the percentage in T lymphocyte subsets but not in B cells. From the results obtained, we could conclude that the whole blood lysis method is more appropriate than gradient sedimentation by Histopaque for immunophenotyping of blood samples collected after serious adverse events, due to less variation in the lymphocyte subset levels with respect to the time factor. 相似文献
16.
Effect of hyperosmotic shock on phosphoenolpyruvate carboxykinase gene expression and gluconeogenic activity in the crab muscle 总被引:1,自引:0,他引:1
Schein V Waché Y Etges R Kucharski LC van Wormhoudt A Da Silva RS 《FEBS letters》2004,561(1-3):202-206
Chasmagnathus granulata phosphoenolpyruvate carboxykinase (PEPCK) cDNA from jaw muscle was cloned and sequenced, showing a specific domain to bind phosphoenolpyruvate in addition to the kinase-1 and kinase-2 motifs to bind guanosine triphosphate (GTP) and Mg(2+), respectively, specific for all PEPCKs. In the kinase-1 motifs the GK was changed to RK. The first 19 amino acids of the putative enzyme contain hydrophobic amino acids and hydroxylated residues specific to a mitochondrial type signal. The PEPCK is expressed in hepatopancreas, muscles, nervous system, heart, and gills. Hyperosmotic stress for 24 h increased the PEPCK mRNA level, gluconeogenic and PEPCK activities in muscle. 相似文献
17.
Luiz Rodrigo Saldanha Gazzaneo Reinaldo Farias Paiva de Lucena Paulino Ulysses de Albuquerque 《Journal of ethnobiology and ethnomedicine》2005,1(1):1-8
This paper investigates the wealth of medicinal plants used by the Apatani tribe of Arunachal Pradesh. Apatani have traditionally settled in seven villages in the Ziro valley of Lower Subansiri district of Arunachal Pradesh in the Eastern Himalayan region of India. The present study has resulted in the documentation of 158 medicinal plant species used by the Apatani group of villages. These medicinal plant species were distributed across 73 families and 124 genera. Asteraceae was the most dominant family (19 species, 11 genera) of medicinal plants, followed by Zingiberaceae, Solanaceae, Lamiaceae and Araceae. For curing ailments, the use of aboveground plant parts was higher (80%) than the belowground plant parts in the Apatani group of villages. Of the aboveground plant parts, leaf was used in the majority of cases (56 species), followed by fruit. Different belowground plant forms such as root, tuber, rhizome, bulb and pseudo-bulb were used by Apatani as a medicine. About 52 types of ailments were cured by using these 158 medicinal plant species. The results of this study are further discussed in the changing socio-economic contexts. 相似文献
18.
Fraga CG 《Molecular aspects of medicine》2005,26(4-5):235-244
The metals Mn, Fe, Cu, and Zn, and the non-metal Se are considered "trace elements" (TE) because of their essentiality and very limited quantity in humans. The biological activities of Cu, Fe, Mn, and Se are strongly associated with the presence of unpaired electrons that allow their participation in redox reactions. In biological systems these metals are mostly bound to proteins, forming metalloproteins. Many of the metals in metalloproteins are part of enzymatic systems, have structural and storage functions, or use the protein to be transported to their target site in the organism. In humans Mn, Fe, Cu, Zn, and Se accomplish decisive functions to maintain human health. Deficiency in any of these TE leads to undesirable pathological conditions that can be prevented or reversed by adequate supplementation. In sufficiently nourished persons, supplementation should be carefully controlled, given the toxic effects ascribed to TE when present in quantities exceeding those required for accomplishing their biological functions. The dietary reference intakes provided by national regulatory agencies are guides to define intake, supplementation and toxicity of Mn, Fe, Cu, Zn, and Se, as well other elements considered micronutrients for humans. 相似文献
19.
Luiz Henrique Soares de Andrade Wilson Max Almeida Monteiro de Moraes Eduardo Hiroshi Matsuo Junior Elizabeth de Orleans Carvalho de Moura Hanna Karen Moreira Antunes Jairo Montemor Ednei Luiz Antonio Danilo Sales Bocalini Andrey Jorge Serra Paulo José Ferreira Tucci Patricia Chakur Brum Alessandra Medeiros 《Molecular and cellular biochemistry》2015,402(1-2):193-202
20.
Environmental and spatial processes influencing phytoplankton biomass along a reservoirs‐river‐floodplain lakes gradient: A metacommunity approach 下载免费PDF全文
Jascieli Carla Bortolini Alfonso Pineda Luzia Cleide Rodrigues Susicley Jati Luiz Felipe Machado Velho 《Freshwater Biology》2017,62(10):1756-1767