全文获取类型
收费全文 | 102篇 |
免费 | 13篇 |
专业分类
115篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 14篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 1篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有115条查询结果,搜索用时 15 毫秒
21.
The Kosi coastal lake system, a chain of four interconnected basins, is located in the subtropical north-eastern corner of South Africa. Little information is available on zooplankton of the system and the main aim of this study is to report on zooplankton samples collected during 2002 and 2003. The set of samples consists of seasonal, subsurface mesozooplankton samples that were collected during nighttime in each of the lakes. A well-developed salinity gradient was evident along the interconnected lakes in the subsurface water during all seasons, ranging from freshwater in the upper lake Amanzamnyama to a maximum of 22 recorded in Lake Makhawulani. The zooplankton community structures of the lakes reflected the salinity gradient of the system, with some coastal marine taxa recorded in the lakes closer to the mouth and only freshwater taxa recorded in Lake Amanzamnyama. Mesozooplankton diversity and abundance were relatively low compared to other estuarine systems along the eastern coast of South Africa. The dominant taxa were calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the mysid Mesopodopsis africana in the lower lakes, whereas cyclopoids Mesocyclops sp. and Thermocyclops sp. dominated the freshwater lake Amanzamnyama. 相似文献
22.
Molecular phylogeny of Neotropical bioluminescent beetles (Coleoptera: Elateroidea) in southern and central Brazil 下载免费PDF全文
Bioluminescence in beetles is found mainly in the Elateroidea superfamily (Elateridae, Lampyridae and Phengodidae). The Neotropical region accounts for the richest diversity of bioluminescent species in the world with about 500 described species, most occurring in the Amazon, Atlantic rainforest and Cerrado (savanna) ecosystems in Brazil. The origin and evolution of bioluminescence, as well as the taxonomic status of several Neotropical taxa in these families remains unclear. In order to contribute to a better understanding of the phylogeny and evolution of bioluminescent Elateroidea we sequenced and analyzed sequences of mitochondrial NADH2 and the nuclear 28S genes and of the cloned luciferase sequences of Brazilian species belonging to the following genera: (Lampyridae) Macrolampis, Photuris, Amydetes, Bicellonycha, Aspisoma, Lucidota, Cratomorphus; (Elateridae) Conoderus, Pyrophorus, Hapsodrilus, Pyrearinus, Fulgeochlizus; and (Phengodidae) Pseudophengodes, Phrixothrix, Euryopa and Brasilocerus. Our study supports a closer phylogenetic relationship between Elateridae and Phengodidae as other molecular studies, in contrast with previous morphologic and molecular studies that clustered Lampyridae/Phengodidae. Molecular data also supported division of the Phengodinae subfamily into the tribes Phengodini and Mastinocerini. The position of the genus Amydetes supports the status of the Amydetinae as a subfamily. The genus Euryopa is included in the Mastinocerini tribe within the Phengodinae/Phengodidae. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
23.
In 59 samples of periphyton and phytoplankton collected in 2002 - 2003 from the Nahal Qishon (Qishon River), northern Israel, we found 178 species from seven divisions of algae and cyanoprocaryotes. Diatoms, clorophytes, and cyanoprocaryotes prevail. Nitzschia and Navicula (Bacillariophyta) are the most abundant. Most of the species are cosmopolitan or widespread, except Lagynion janei (Chrysophyta), which is endemic for the Mediterranean Realm. About 17% of species (26) are new for Israel and five of them represent the first recorded genera: Crinalium endophyticum Crow, Actinocyclus normanii (Gregory) Hustedt, Rhizoclonium hieroglyphicum (Agardh) Kütz (Chlorophyta), Lagynion janei Bourelly, and Stylococcus aureus Chodat. Most of them come from a rare riverine assemblage with red alga Audouinella pygmea, as well as from the estuarine assemblage. Alkaliphiles predominate among the indicators of acidity, with few acidophiles confined to the communities under the impact of industrial wastes. Among the indicators of salinity, most numerous are the oligohalobien-indifferents and species adapted to a moderate salinity level. The relative species richness of ecological groups and the indices of saprobity are correlated with changes in conductivity, pH, and N-nitrate concentration. Indicators of organic pollution fall in the range of betameso- to alfamesosaprobic self-purification grades. Our studies show ecological significance of the Nahal Qishon as a model for a strongly disturbed aquatic ecosystem in the coastal zone of eastern Mediterranean. 相似文献
24.
Marisa Zallocchi Katie Binley Yatish Lad Scott Ellis Peter Widdowson Sharifah Iqball Vicky Scripps Michelle Kelleher Julie Loader James Miskin You-Wei Peng Wei-Min Wang Linda Cheung Duane Delimont Kyriacos A. Mitrophanous Dominic Cosgrove 《PloS one》2014,9(4)
Usher syndrome type 1B is a combined deaf-blindness condition caused by mutations in the MYO7A gene. Loss of functional myosin VIIa in the retinal pigment epithelia (RPE) and/or photoreceptors leads to blindness. We evaluated the impact of subretinally delivered UshStat, a recombinant EIAV-based lentiviral vector expressing human MYO7A, on photoreceptor function in the shaker1 mouse model for Usher type 1B that lacks a functional Myo7A gene. Subretinal injections of EIAV-CMV-GFP, EIAV-RK-GFP (photoreceptor specific), EIAV-CMV-MYO7A (UshStat) or EIAV-CMV-Null (control) vectors were performed in shaker1 mice. GFP and myosin VIIa expression was evaluated histologically. Photoreceptor function in EIAV-CMV-MYO7A treated eyes was determined by evaluating α-transducin translocation in photoreceptors in response to low light intensity levels, and protection from light induced photoreceptor degeneration was measured. The safety and tolerability of subretinally delivered UshStat was evaluated in macaques. Expression of GFP and myosin VIIa was confirmed in the RPE and photoreceptors in shaker1 mice following subretinal delivery of the EIAV-CMV-GFP/MYO7A vectors. The EIAV-CMV-MYO7A vector protected the shaker1 mouse photoreceptors from acute and chronic intensity light damage, indicated by a significant reduction in photoreceptor cell loss, and restoration of the α-transducin translocation threshold in the photoreceptors. Safety studies in the macaques demonstrated that subretinal delivery of UshStat is safe and well-tolerated. Subretinal delivery of EIAV-CMV-MYO7A (UshStat) rescues photoreceptor phenotypes in the shaker1 mouse. In addition, subretinally delivered UshStat is safe and well-tolerated in macaque safety studies These data support the clinical development of UshStat to treat Usher type 1B syndrome. 相似文献
25.
Macroautophagy (hereafter autophagy) is a regulated intracellular process during which cytoplasmic cargo engulfed by double-membrane autophagosomes is delivered to the vacuole or lysosome for degradation and recycling. Atg8 that is conjugated to phosphatidylethanolamine (PE) during autophagy plays an important role not only in autophagosome biogenesis but also in cargo recruitment. Conjugation of PE to Atg8 requires processing of the C-terminal conserved glycine residue in Atg8 by the Atg4 cysteine protease. The Arabidopsis plant genome contains 9 Atg8 (AtATG8a to AtATG8i) and 2 Atg4 (AtATG4a and AtATG4b) family members. To understand AtATG4’s specificity toward different AtATG8 substrates, we generated a unique synthetic substrate C-AtATG8-ShR (citrine-AtATG8-Renilla luciferase SuperhRLUC). In vitro analyses indicated that AtATG4a is catalytically more active and has broad AtATG8 substrate specificity compared with AtATG4b. Arabidopsis transgenic plants expressing the synthetic substrate C-AtAtg8a-ShR is efficiently processed by endogenous AtATG4s and targeted to the vacuole during nitrogen starvation. These results indicate that the synthetic substrate mimics endogenous AtATG8, and its processing can be monitored in vivo by a bioluminescence resonance energy transfer (BRET) assay. The synthetic Atg8 substrates provide an easy and versatile method to study plant autophagy during different biological processes. 相似文献
26.
What is the impact of a genetic evaluation for colorectal cancer susceptibility? We previously reported a study of individuals diagnosed with colorectal cancer at 60 years of age or less in a five-county area of New York including Rochester. Subjects reporting at least one first- or second-degree relative with colorectal cancer were invited to receive genetic counseling and DNA testing. Of the 37 persons tested, we previously reported that 6 were found to have deleterious mutations in MSH2 or MLH1. A mutation has since been found in a seventh subject in another laboratory. To evaluate the impact of the testing experience, we followed-up on 36 of these 37 subjects at 3 and 12 months after communicating their DNA test result. We ascertained their knowledge of colon cancer, whether they told relatives their test result, their surveillance behavior, and their mental health. Three months after receiving their result, subjects knew more about colon cancer if they had more cancer of all types in their family (p = 0.02). At 12 months, they knew more if they had been found to have a mutation (p < 0.001), were younger when DNA tested (p < 0.01), or were younger when diagnosed with cancer (p < 0.03). All but 1 of those found to have an abnormality told relatives. Relatives of 3 subjects in whom a mutation had been found came to us to be tested themselves. At 12 months, surveillance for colon and endometrial cancer was more adherent if there were more total cancers in the family (p < 0.05) or if the testee were more worried about cancer (p < 0.05). Self-assessed mental health at 12 months was better for those who were married (p < 0.05). This study suggests that individuals undergoing a genetic evaluation for an inherited susceptibility to colorectal cancer pursue recommended surveillance and inform relatives of their result. 相似文献
27.
S C Kinsky K Hashimoto J E Loader M S Knight D J Fernandes 《Biochimica et biophysica acta》1986,885(2):129-135
This study compares the ability of methotrexate and liposomes, in which the drug is anchored to the lipid bilayers via methotrexate-gamma-dimyristoylphosphatidylethanolamine, to inhibit proliferation of human leukemic cells (CEM/O) and cells derived from this line that are resistant to methotrexate because of either a defective transport system (CEM/MTX cells) or elevated levels of dihydrofolate reductase (CEM/R1 cells). Whereas CEM/O and CEM/MTX cells show a 120-fold difference in their susceptibility to methotrexate (as measured by the incorporation of tritiated deoxyuridine into DNA), both lines are equally sensitive to the liposomes. In contrast, proliferation of CEM/MTX cells is not inhibited significantly by methotrexate-gamma-glycerophosphorylethanolamine (MTX-gamma-glyceroPE), the water-soluble analog of MTX-gamma-DMPE. Both the ability of the liposomes to circumvent the transport defect, and the inability of MTX-gamma-glyceroPE to do so, were anticipated on the basis of previous experiments which show that thiamine pyrophosphate could antagonize inhibition of mouse 3T3 and L1210 cell proliferation by methotrexate and MTX-gamma-glyceroPE, but not inhibition by liposomes. Human cells (CEM/O) behave similarly. The present experiments also suggest that liposomes prepared with MTX-gamma-DMPE can partially reverse the methotrexate resistance of CEM/R1 cells that is due to overproduction of the target enzyme. 相似文献
28.
29.
S. Aydin H Ozercan F. Dagli S. Aydin O. Dogru S. Celebi O. Akin SP Guzel 《Biotechnic & histochemistry》2005,80(3):163-168
Ghrelin (G-HH) synthesized in several tissues including salivary and stomach glands stimulates appetite in humans by modulating neuropeptide Y neurons in the hypothalamic arcuate nucleus. Loss of appetite is one of the most important symptoms of stomach cancer. We conducted a study using immunohistochemistry to determine whether salivary glands and stomach cancer tissues produce ghrelin. We determined that negative ghrelin immunohistochemistry discriminates tumors from normal tissues and may therefore further our understanding of the clinically important problem of reduced food intake and anorexia in cancer patients. Radioimmunoassay analyses confirmed that cancer cells do not produce a G-HH peptide, whereas normal cells yield this peptide. 相似文献
30.
Taube C Wei X Swasey CH Joetham A Zarini S Lively T Takeda K Loader J Miyahara N Kodama T Shultz LD Donaldson DD Hamelmann EH Dakhama A Gelfand EW 《Journal of immunology (Baltimore, Md. : 1950)》2004,172(10):6398-6406
In certain models of allergic airway disease, mast cells facilitate the development of inflammation and airway hyper-responsiveness (AHR). To define the role of the high affinity IgE receptor (FcepsilonRI) in the development of AHR, mice with a disruption of the alpha subunit of the high affinity IgE receptor (FcepsilonRI(-/-)) were exposed on 10 consecutive days to nebulized OVA. Forty-eight hours after the last nebulization, airway responsiveness was monitored by the contractile response of tracheal smooth muscle to electrical field stimulation (EFS). After the 10-day OVA challenge protocol, wild-type mice demonstrated increased responsiveness to EFS, whereas similarly challenged FcepsilonRI(-/-) mice showed a low response to EFS, similar to nonexposed animals. Further, allergen-challenged FcepsilonRI(-/-) mice showed less airway inflammation, goblet cell hyperplasia, and lower levels of IL-13 in lung homogenates compared with the controls. IL-13-deficient mice failed to develop an increased response to EFS or goblet cell hyperplasia after the 10-day OVA challenge. We transferred bone marrow-derived mast cells from wild-type mice to FcepsilonRI(-/-) mice 1 day before initiating the challenge protocol. After the 10-day OVA challenge, recipient FcepsilonRI(-/-) mice demonstrated EFS-induced responses similar to those of challenged wild-type mice. Transferred mast cells could be detected in tracheal preparations. These results show that FcepsilonRI is important for the development of AHR after an aerosolized allergen sensitization protocol and that this effect is mediated through FcepsilonRI on mast cells and production of IL-13 in the lung. 相似文献