全文获取类型
收费全文 | 899篇 |
免费 | 55篇 |
专业分类
954篇 |
出版年
2022年 | 19篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 41篇 |
2015年 | 54篇 |
2014年 | 54篇 |
2013年 | 64篇 |
2012年 | 83篇 |
2011年 | 68篇 |
2010年 | 69篇 |
2009年 | 52篇 |
2008年 | 62篇 |
2007年 | 41篇 |
2006年 | 51篇 |
2005年 | 43篇 |
2004年 | 38篇 |
2003年 | 27篇 |
2002年 | 32篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1972年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有954条查询结果,搜索用时 15 毫秒
871.
Vlastimil?Hart Petra?Nováková Erich?Pascal?Malkemper Sabine?Begall Vladimír?Hanzal Milo??Je?ek Tomá??Ku?ta Veronika?Němcová Jana?Adámková Kate?ina?Benediktová Jaroslav??erveny Hynek?BurdaEmail author 《Frontiers in zoology》2013,10(1):80
Introduction
Several mammalian species spontaneously align their body axis with respect to the Earth’s magnetic field (MF) lines in diverse behavioral contexts. Magnetic alignment is a suitable paradigm to scan for the occurrence of magnetosensitivity across animal taxa with the heuristic potential to contribute to the understanding of the mechanism of magnetoreception and identify further functions of magnetosensation apart from navigation. With this in mind we searched for signs of magnetic alignment in dogs. We measured the direction of the body axis in 70 dogs of 37 breeds during defecation (1,893 observations) and urination (5,582 observations) over a two-year period. After complete sampling, we sorted the data according to the geomagnetic conditions prevailing during the respective sampling periods. Relative declination and intensity changes of the MF during the respective dog walks were calculated from daily magnetograms. Directional preferences of dogs under different MF conditions were analyzed and tested by means of circular statistics.Results
Dogs preferred to excrete with the body being aligned along the North–South axis under calm MF conditions. This directional behavior was abolished under unstable MF. The best predictor of the behavioral switch was the rate of change in declination, i.e., polar orientation of the MF.Conclusions
It is for the first time that (a) magnetic sensitivity was proved in dogs, (b) a measurable, predictable behavioral reaction upon natural MF fluctuations could be unambiguously proven in a mammal, and (c) high sensitivity to small changes in polarity, rather than in intensity, of MF was identified as biologically meaningful. Our findings open new horizons in magnetoreception research. Since the MF is calm in only about 20% of the daylight period, our findings might provide an explanation why many magnetoreception experiments were hardly replicable and why directional values of records in diverse observations are frequently compromised by scatter.872.
Biological nitrate removal in industrial wastewater treatment: which electron donor we can choose 总被引:3,自引:0,他引:3
Biological denitrification was reviewed regarding its potential application to treating nitrate in industrial wastewater.
Although heterotrophic denitrification is an efficient and well-developed process, some carbon content in wastewater is essential
to maintain bacterial activity. Because of the high operating cost of heterotrophic denitrification caused by the required
addition of a carbon source and potential “carbon breakthrough”, the study of autotrophic denitrification has attracted the
interest of numerous researchers. Many advances in autotrophic processes have been made in the application of novel concepts
and reaction schemes. While the main advantage of autotrophic bacteria rests on the reduction of operating costs by the replacement
of an external carbon source with a cheaper electron donor, further decrease in cost requires additional refinement of these
processes, including further improvement of reactor structure and optimization of reaction conditions. In the long term, new
concepts are required for a compact wastewater treatment process. This review addresses the state of the art of each electron
donor candidate for its potential application to the treatment of industrial wastewater containing nitrate. 相似文献
873.
874.
Song KH Lee WJ Koh JM Kim HS Youn JY Park HS Koh EH Kim MS Youn JH Lee KU Park JY 《Biochemical and biophysical research communications》2005,326(1):197-202
Several lines of evidence have suggested that triglyceride accumulation in skeletal muscle and pancreatic islets is causally related to type 2 diabetes mellitus. We recently showed that alpha-lipoic acid (ALA), a potent antioxidant and cofactor of mitochondrial respiratory enzymes, reduces body weight of rodents by suppressing food intake and increasing energy expenditure. We sought to determine if ALA can prevent the development of diabetes mellitus in obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Most (78%) untreated OLETF rats showed glycosuria at 40 weeks of age, but this was completely prevented by ALA. Compared with untreated OLETF rats, ALA reduced body weight and protected pancreatic beta-cells from destruction. ALA also reduced triglyceride accumulation in skeletal muscle and pancreatic islets. These results indicate that ALA prevents diabetes mellitus in obese diabetes-prone rats by reducing lipid accumulation in non-adipose tissue as well as in adipose tissue. 相似文献
875.
Kim BR Yang EK Kim SH Moon DC Kim HJ Lee JC Kim DY 《Journal of microbiology (Seoul, Korea)》2011,49(1):115-120
Dendritic cell (DC)-based immunotherapy is a potent therapeutic modality for treating renal cell carcinoma (RCC), but development
of antigens specific for tumor-targeting and anti-tumor immunity is of great interest for clinical trials. The present study
investigated the ability of DCs pulsed with a combination of carbonic anhydrase IX (CA9) as an RCC-specific biomarker and
Acinetobacter baumannii outer membrane protein A (AbOmpA) as an immunoadjuvant to induce anti-tumor immunity against murine renal cell carcinoma
(RENCA) in a murine model. Murine bone-marrow-derived DCs pulsed with a combination of RENCA lysates and AbOmpA were tested
for their capacity to induce DC maturation and T cell responses in vitro. A combination of RENCA lysates and AbOmpA up-regulated the surface expression of co-stimulatory molecules, CD80 and CD86,
and the antigen presenting molecules, major histocompatibility (MHC) class I and class II, in DCs. A combination of RENCA
lysates and AbOmpA also induced interleukin-12 (IL-12) production in DCs. Next, the immunostimulatory activity of DCs pulsed
with a combination of CA9 and AbOmpA was determined. A combination of CA9 and AbOmpA up-regulated the surface expression of
co-stimulatory molecules and antigen presenting molecules in DCs. DCs pulsed with a combination of CA9 and AbOmpA effectively
secreted IL-12 but not IL-10. These cells interacted with T cells and formed clusters. DCs pulsed with CA9 and AbOmpA elicited
the secretion of interferon-γ and IL-2 in T cells. In conclusion, a combination of CA9 and AbOmpA enhanced the immunostimulatory
activity of DCs, which may effectively induce anti-tumor immunity against human RCC. 相似文献
876.
Se-Eun Park Kumar Sapkota Jun-Hui Choi Myung-Kon Kim Young Hoi Kim Ki Man Kim Kyung Je Kim Ha-Na Oh Sung-Jun Kim Seung Kim 《Neurochemical research》2014,39(4):707-718
Dendropanax morbifera Leveille (Araliaceae) is well known in Korean traditional medicine for a variety of diseases. Rotenone is a commonly used neurotoxin to produce in vivo and in vitro Parkinson’s disease models. This study was designed to elucidate the processes underlying neuroprotection of rutin, a bioflavonoid isolated from D. morbifera Leveille in cellular models of rotenone-induced toxicity. We found that rutin significantly decreased rotenone-induced generation of reactive oxygen species levels in SH-SY5Y cells. Rutin protected the increased level of intracellular Ca2+ and depleted level of mitochondrial membrane potential (ΔΨm) induced by rotenone. Furthermore, it prevented the decreased ratio of Bax/Bcl-2 caused by rotenone treatment. Additionally, rutin protected SH-SY5Y cells from rotenone-induced caspase-9 and caspase-3 activation and apoptotic cell death. We also observed that rutin repressed rotenone-induced c-Jun N-terminal kinase and p38 mitogen-activated protein kinase phosphorylation. These results suggest that rutin may have therapeutic potential for the treatment of neurodegenerative diseases associated with oxidative stress. 相似文献
877.
878.
Wei YD Lee KS Gui ZZ Yoon HJ Kim I Je YH Lee SM Zhang GZ Guo X Sohn HD Jin BR 《Insect biochemistry and molecular biology》2006,36(6):435-441
We previously reported that the beta-1,4-endoglucanase (EGase) belonging to glycoside hydrolase family (GHF) 45 of the mulberry longicorn beetle, Apriona germari (Ag-EGase II), has three potential N-linked glycosylation sites; these sites are located at amino acid residues 56-59 (NKSG), 99-102 (NSTF), and 237-239 (NYSstop). In the present study, we analyze the functional role of these potential N-linked glycosylation sites. Tunicamycin treatment completely abolished the enzymatic activity of Ag-EGase II. To further elucidate the functional role of the N-linked glycosylation sites in Ag-EGase II, we have assayed the cellulase enzyme activity in Ser58Gln, Thr101Gln, or Ser239Gln mutants. Lack of N-linked glycosylation site at residues 99-102 (NSTF), the site of which is conserved in known beetle GHF 45 cellulases, showed loss of enzyme activity and reduced the molecular mass of the enzyme. In contrast, mutations in Ser58Gln or Ser239Gln affected neither the activity nor the apparent molecular mass of the enzyme, indicating that these sites did not lead to N-linked glycosylation. The present study demonstrates that N-linked glycosylation at residues 99-102 (NSTF), while not essential for secretion, is required for Ag-EGase II enzyme activity. 相似文献
879.
Rapid, large-scale generation of Ds transposant lines and analysis of the Ds insertion sites in rice 总被引:1,自引:0,他引:1
Kim CM Piao HL Park SJ Chon NS Je BI Sun B Park SH Park JY Lee EJ Kim MJ Chung WS Lee KH Lee YS Lee JJ Won YJ Yi G Nam MH Cha YS Yun DW Eun MY Han CD 《The Plant journal : for cell and molecular biology》2004,39(2):252-263
Rapid, large-scale generation of a Ds transposant population was achieved using a regeneration procedure involving tissue culture of seed-derived calli carrying Ac and inactive Ds elements. In the F(2) progeny from genetic crosses between the same Ds and Ac starter lines, most of the crosses produced an independent germinal transposition frequency of 10-20%. Also, many Ds elements underwent immobilization even though Ac was expressed. By comparison, in a callus-derived regenerated population, over 70% of plants carried independent Ds insertions, indicating transposition early in callus formation. In the remaining population, the majority of plants carried only Ac. Most of the new Ds insertions were stably transmitted to a subsequent generation. An exceptionally high proportion of independent transposants in the regenerated population means that selection markers for transposed Ds and continual monitoring of Ac/Ds activities may not necessarily be required. By analyzing 1297 Ds-flanking DNA sequences, a genetic map of 1072 Ds insertion sites was developed. The map showed that Ds elements were transposed onto all of the rice chromosomes, with preference not only near donor sites (36%) but also on certain physically unlinked arms. Populations from both genetic crossing and tissue culture showed the same distribution patterns of Ds insertion sites. The information of these mapped Ds insertion sites was deposited in GenBank. Among them, 55% of Ds elements were on predicted open-reading frame (ORF) regions. Thus, we propose an optimal strategy for the rapid generation of a large population of Ds transposants in rice. 相似文献
880.
We investigated the distribution, toxicity, morphology, and protein profiles of Bacillus thuringiensis isolates from forests in Korea to isolate naturally occurring novel B. thuringiensis. A total of 170 B. thuringiensis isolates were obtained from 832 samples producing spore and parasporal inclusion bodies. In toxicity tests for lepidopteran, dipteran, and coleopteran insects, 57.6% isolates were toxic only to Lepidoptera, 5.3% were toxic only to Diptera, and 24.1% were toxic to both Diptera and Lepidoptera. The remaining collections (13.0%) were not toxic to the tested insects. The shapes of the parasporal crystals produced in B. thuringiensis isolates were bipyramidal, spherical, ovoid, or irregular. As their toxicities varied with parasporal crystal shape, B. thuringiensis isolates possessing bipyramidal or irregular parasporal crystals were largely toxic to lepidopteran species whereas those producing spherical parasporal crystals were mainly toxic to dipteran species. B. thuringiensis toxic to both dipteran and lepidopteran insects contained 130- and 70-kDa parasporal crystals, whereas B. thuringiensis toxic to lepidopteran insects expressed 130-kDa parasporal crystals. The results suggest that forest areas in Korea are a rich source of B. thuringiensis and need to be further explored to discover novel B. thuringiensis isolates. 相似文献