全文获取类型
收费全文 | 498篇 |
免费 | 37篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 22篇 |
2012年 | 34篇 |
2011年 | 40篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 34篇 |
2007年 | 25篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 17篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1961年 | 3篇 |
1960年 | 3篇 |
1957年 | 2篇 |
1955年 | 2篇 |
1953年 | 2篇 |
1951年 | 3篇 |
1947年 | 2篇 |
1943年 | 2篇 |
1942年 | 2篇 |
1936年 | 2篇 |
1931年 | 2篇 |
1929年 | 3篇 |
1928年 | 2篇 |
1927年 | 2篇 |
排序方式: 共有535条查询结果,搜索用时 31 毫秒
11.
12.
By means of gel electrophoresis of tissue extracts we have studied protein polymorphism inEligmodontia typus. The analysis was performed on specimens from five population samples collected at different sites in Patagonia (Argentina). Mean heterozygosity (\-h) and proportion of polymorphic loci (P) were determined on the basis of 19 loci. Considering all individuals as one sample, \-h gave a value of 0.16 and P was 70%. Although these values are much higher than those reported for most rodent species, they are very similar to those obtained by us for four species of the genusCalomys and forGraomys griseoflavus. There is a striking genetic identity (IN=0.99) among populations from regions with different environmental conditions, indicating that the species possesses a common genic pool. Genetic distance with other species of the Phyllotini was estimated. DN was lower betweenE. typus andCalomys (mean DN=0.88) than betweenE. typus andGraomys griseoflavus (DN=1.01). The high morphological similarity between these last two species, especially regarding those characters related to desert life adaptation, could be assigned, at least in part, to convergent evolution. 相似文献
13.
Maritza Martínez Gladys Len De Pinto Sofía Alvrez Nola Gonzlez De Troconis Edgar Ocando Carlos Rivas 《Biochemical Systematics and Ecology》1995,23(7-8):843-848
An analytical study has been made of six gum specimens from Albizia lebbeck, Leguminosae. Galactose, mannose, arabinose, glucuronic acid and its 4-O--metyl analogue are present in all the specimens studied. Rhamnose was not detected according to sugar analysis and spectral data. The absence of this sugar, the high acidity and the relatively low limit viscosity number contrast with the values reported previously for one African sample of A. lebbeck. The lead content is much higher than that recorded for other Albizia gums. 13C-NMR spectrum of this gum, in deuterium oxide, shows good resolution. 相似文献
14.
R. E. Martenson Gladys E. Deibler A. J. Kramer S. Levine 《Journal of neurochemistry》1975,24(1):173-182
Guinea pig and bovine myelin basic proteins were chemically cleaved at the carboxyl peptide bonds of methionyl and tryptophanyl residues to yield several fragments. Comparison of the bovine fragment consisting of the first 20 residues of the protein with the corresponding guinea pig fragment showed that the latter differs in containing histidine and glycine (one residue of each), an additional threonyl residue, and one fewer alanyl residues. Comparison of the bovine fragment consisting of the C-terminal 54 residues of the protein (residues 117-170) with the corresponding guinea pig fragment showed that the latter differs in containing one fewer histidyl and leucyl residues and an additional phenylalanyl residue. Tests of encephalitogenic activity in Lewis rats showed that these two fragments from both species were much less active, on a molar basis, than the uncleaved protein. On the other hand, examination of the bovine fragments consisting of residues 1-116 and 21-116 and the corresponding fragments obtained from the guinea pig protein revealed activity at least as high as that of the respective uncleaved proteins. 相似文献
15.
16.
Gladys I. Galende Adriana Troncoso Sergio A. Lambertucci 《Studies on Neotropical Fauna and Environment》2013,48(1):32-39
We assessed diet selection, impact on vegetation, and explored habitat relationships with marsh birds of coypus (Myocastor coypus) in a steppe lagoon in Argentinean Patagonia. In two consecutive springs, abundance and spatial use of the coypus and nesting marsh birds were estimated by direct counts. The coypu was a selective consumer with seasonal variations in food items, and Myriophyllum sp. and Schoenoplectus californicus dominated its diet. Coypus and marsh birds showed a differential spatial use when rushes cover was high. However, when rushes cover decreased by coypu browsing, there was a similar use of space, and marsh birds were displaced to nest on the open water and other poorly protected areas of the rushes. Our results suggest that high abundances of coypu can have a detrimental effect on wetland ecosystems. Systematic monitoring and evaluation of their effects on wetlands in recently colonized areas is recommended. 相似文献
17.
Gladys N. Honein-AbouHaidar Nancy N. Baxter Rahim Moineddin David R. Urbach Linda Rabeneck Arlene S. Bierman 《Cancer epidemiology》2013,37(6):946-956
Background: Participation in screening tests for colorectal cancer (CRC) is generally low in Ontario, Canada. In addition, inequities in participation exist including lower participation among low-income individuals, males and individuals living in rural areas. In April 2008, Colon Cancer Check (CCC) program, the province-wide CRC screening program, was launched in Ontario. This study describes the trends and inequities in CRC screening participation three years before and three years after the CCC, and assesses the effect of the program on CRC screening participation, overall and among certain population groups. Methods: We used administrative data to identify cohorts of individuals eligible for CRC screening in fiscal years 2005–2011. We calculated the age-standardized percent of Fecal Occult Blood Test (FOBT) participation, large bowel endoscopy participation, and being ‘up-to-date’ with CRC screening tests. Results: From 2005 to 2011, FOBT participation increased from 7.6% to 14.8%, large bowel endoscopy participation from 3.4% to 5.7%, and ‘up-to-date’ with CRC screening from 27.2% to 41.3%. Before the launch of the CCC program, the quarterly increase in FOBT participation was 0.07% (p = 0.19), increased immediately after the launch (1.8%, p < 0.01), followed by a decline (?0.08%, p = 0.08), returning to its pre-program increase rate. We noted a significant decrease in FOBT participation every summer (?0.44%, p < 0.01). The CCC program had minimal effect on large bowel endoscopy participation. Before the launch of the CCC program, the quarterly increase in ‘up-to-date’ with CRC screening was 0.9% (p < 0.01), increased immediately after the launch (2.5%, p = 0.05), followed by a modest decline thereafter (?0.59%, p < 0.02). From 2005 to 2011, recent residents living in low-income neighborhoods were consistently and significantly less likely to have a FOBT and be ‘up-to-date’ with CRC screening than long-term residents living in high-income neighborhoods (2.9–4.5%; 14.7–17.3% respectively). Pre-CCC inequities in CRC participation persisted after the launch of the program. Conclusion: CRC testing was increasing in Ontario from 2005. An immediate increase in CRC testing, FOBT in particular, occurred after the launch of the CCC program, followed by a return to its pre-CCC increase rate thereafter. Future efforts are needed to improve screening participation and address inequities. 相似文献
18.
Bulle Cécile Margni Manuele Patouillard Laure Boulay Anne-Marie Bourgault Guillaume De Bruille Vincent Cao Viêt Hauschild Michael Henderson Andrew Humbert Sebastien Kashef-Haghighi Sormeh Kounina Anna Laurent Alexis Levasseur Annie Liard Gladys Rosenbaum Ralph K. Roy Pierre-Olivier Shaked Shanna Fantke Peter Jolliet Olivier 《The International Journal of Life Cycle Assessment》2019,24(9):1653-1674
The International Journal of Life Cycle Assessment - This paper addresses the need for a globally regionalized method for life cycle impact assessment (LCIA), integrating multiple state-of-the-art... 相似文献
19.
20.
Ileana Vera‐Reyes Itandehui Juanita Erendira Esparza‐Arredondo Ricardo Hugo Lira‐Saldivar Carlos Alejandro Granados‐Echegoyen Rocío Alvarez‐Roman Alfonso Vsquez‐Lpez Gladys De los Santos‐Villarreal Enrique Díaz‐Barriga Castro 《Journal of Phytopathology》2019,167(7-8):461-469
In this research, the in vitro antimicrobial effect of zinc oxide (ZnO), copper oxide (CuO) and iron oxide (Fe2O3) nanoparticles (NPs)—with average sizes of 20, 46 and 30 nm, respectively—on the root rot disease caused by the fungus Fusarium oxysporum and on blight disease caused by the fungus Alternaria solani were studied. Also, bacterial diseases caused by Clavibacter michiganensis and Pseudomonas syringae that infects a wide range of plant species were assessed. Different concentrations of NPs (0, 100, 250, 500, 700 and 1,000 mg/L) were prepared on PDA agar or King's B medium in a complete randomized design with four replicates. According to the results, ZnO NPs exhibited an outstanding inhibitory effect against fungi and bacteria strains. The above results were associated with the smaller particle size. Fungi strains showed a differential sensitivity depending on the kind of NPs used. A. solani showed the highest sensitivity to ZnO NPs at 1,000 mg/L (99%), followed by CuO NPs at the same dose (95%). Fe2O3 NPs at all evaluated doses had no inhibitory effects on the mycelia growth of this strain, although F. oxysporum revealed greater effectiveness of the CuO NPs (96%) compared with ZnO NPs since it only inhibited 91% of the mycelial growth. The antibacterial activity was studied through optical density. C. michiganensis was found to be more sensitive to ZnO NPs because a lesser dose (700 mg/L) was required to reduce the bacterial growth (90%); in comparison, P. syringae required a dose of 1,000 mg/L to inhibit its growth (67%). CuO NPs displayed the smallest growth inhibition against the bacteria strains analysed. The antimicrobial effect of the metallic NPs that were assayed increased with higher doses. 相似文献