全文获取类型
收费全文 | 80525篇 |
免费 | 5303篇 |
国内免费 | 12篇 |
出版年
2023年 | 515篇 |
2022年 | 575篇 |
2021年 | 1438篇 |
2020年 | 1140篇 |
2019年 | 1329篇 |
2018年 | 2413篇 |
2017年 | 2201篇 |
2016年 | 2943篇 |
2015年 | 3822篇 |
2014年 | 3980篇 |
2013年 | 5331篇 |
2012年 | 6169篇 |
2011年 | 5673篇 |
2010年 | 3674篇 |
2009年 | 2969篇 |
2008年 | 4345篇 |
2007年 | 4068篇 |
2006年 | 3857篇 |
2005年 | 3352篇 |
2004年 | 3241篇 |
2003年 | 2933篇 |
2002年 | 2671篇 |
2001年 | 1778篇 |
2000年 | 1712篇 |
1999年 | 1376篇 |
1998年 | 699篇 |
1997年 | 524篇 |
1996年 | 524篇 |
1995年 | 479篇 |
1994年 | 372篇 |
1993年 | 353篇 |
1992年 | 714篇 |
1991年 | 621篇 |
1990年 | 570篇 |
1989年 | 546篇 |
1988年 | 521篇 |
1987年 | 468篇 |
1986年 | 439篇 |
1985年 | 437篇 |
1984年 | 440篇 |
1983年 | 316篇 |
1982年 | 303篇 |
1981年 | 243篇 |
1980年 | 236篇 |
1979年 | 287篇 |
1978年 | 261篇 |
1975年 | 243篇 |
1974年 | 272篇 |
1973年 | 260篇 |
1972年 | 229篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
941.
942.
Trine Bottos Olsen Daniel García-Martínez Chiara Villa 《American journal of physical anthropology》2023,180(1):224-234
This study aimed to test the performance of 3D digitizer, CT scanner, and surface scanner in detecting cranial fluctuating asymmetry. Sets of 32 landmarks (6 in the midline and 13 bilateral) were acquired from 14 archeological crania using a 3D digitizer, and from 3D models generated from a CT scanner and surface scanner using Viewbox 4. Levels of shape variation were analyzed in MorphoJ using Procrustes analysis of variance and Principal component analysis. Intra-observer error accounted for 1.7%, 1.8%, and 4.5% of total shape variation for 3D digitizer, CT scanner, and surface scanner respectively. Fluctuating asymmetry accounted for 15%–16% of total shape variation. Variation between techniques accounted for 18% of total shape variation. We found a higher level of missing landmarks in our surface scan data than for both 3D digitizer and CT scanner data, and both 3D model-based techniques sometimes obscured taphonomic damage. All three 3D techniques are appropriate for measuring cranial fluctuating asymmetry. We advise against combining data collected with different techniques. 相似文献
943.
944.
Gustavo A. Londoño Juan Pablo Gomez Manuel A. Sánchez-Martínez Douglas J. Levey Scott K. Robinson 《Ecology letters》2023,26(4):609-620
Tropical montane communities host the world's highest beta diversity of birds, a phenomenon usually attributed to community turnover caused by changes in biotic and abiotic factors along elevation gradients. Yet, empirical data on most biotic factors are lacking. Nest predation is thought to be especially important because it appears to be common and can change selective pressures underlying life history traits, which can alter competitive interactions. We monitored 2538 nests, 338 of which had known nest predators, to evaluate if nest predation changes along a tropical elevational gradient. We found that nest predation decreased with elevation, reflecting the loss of lowland predators that do not tolerate colder climates. We found different “super” nest predators at each elevation that accounted for a high percentage of events, suggesting that selection pressures exerted by nest predator communities may be less diffuse than has been hypothesized, at least for birds nesting in the understory. 相似文献
945.
Neuza Domingues André R. A. Marques Rita Diogo Almeida Calado Inês S. Ferreira Cristiano Ramos José Ramalho Maria I. L. Soares Telmo Pereira Luís Oliveira José R. Vicente Louise H. Wong Inês C. M. Simões Teresa M. V. D. Pinho e Melo Andrew Peden Cláudia Guimas Almeida Clare E. Futter Rosa Puertollano Winchil L. C. Vaz Otília V. Vieira 《Traffic (Copenhagen, Denmark)》2023,24(7):284-307
946.
947.
Chromosome numbers are reported for 19 collections representing 16 AsiaticPotentilla taxa. The first chromosome records are reported forP. desertorum Bunge var.arnavatensis Wolf (2n=28),P. festiva Soják (2n=28),P. griffithii Hook f. subsp.beauvaisii (Cardot) Soják (2n=42),P. micropetala D. Don subsp.byssitecta (Soják) Měsí?ek etSoják (2n=14),P. mollissima Lehm. (2n=28),P. moorcroftii Wall. exLehm. (2n=42),P. multicaulis Bunge (2n=14),P. [x]omissa Soják (2n=35, 56, 70) andP. stanjukoviczii Ovcz. exKoczk. (2n=14). Counts differing from those previously recorded are given forP. algida Soják (2n=56) andP. flagellaris Willd. exSchlecht. (2n=42). Chromosome numbers of the following species were confirmed:P. [x]agrimonioides Bieb. (2n=42),P. chinensis Ser. in DC. (2n=14),P. fragarioides L. (2n=14),P. lineata Trev. (2n=14) andP. sericea L. (2n=28). Taxonomy is briefly discussed. A new combinationP. micropetala D. Don subsp.byssitecta (Soják) Měsí?ek etSoják stat. nov. is proposed. 相似文献
948.
Edgar Antonio Rodríguez-Negrete Enrique Alejandro Guevara-Rivera Ángela Paulina Arce-Leal Norma Elena Leyva-López Jesús Méndez-Lozano 《Molecular Plant Pathology》2023,24(10):1300-1311
The nonstructural protein NSm of tomato spotted wilt virus (TSWV) has been identified as the avirulence determinant of the tomato single dominant Sw-5 resistance gene. Although Sw-5 effectiveness has been shown for most TSWV isolates, the emergence of resistance-breaking (RB) isolates has been observed. It is strongly associated with two point mutations (C118Y or T120N) in the NSm viral protein. TSWV-like symptoms were observed in tomato crop cultivars (+Sw-5) in the Baja California peninsula, Mexico, and molecular methods confirmed the presence of TSWV. Sequence analysis of the NSm 118–120 motif and three-dimensional protein modelling exhibited a noncanonical C118F substitution in seven isolates, suggesting that this substitution could emulate the C118Y-related RB phenotype. Furthermore, phylogenetic and molecular analysis of the full-length genome (TSWV-MX) revealed its reassortment-related evolution and confirmed that putative RB-related features are restricted to the NSm protein. Biological and mutational NSm 118 residue assays in tomato (+Sw-5) confirmed the RB nature of TSWV-MX isolate, and the F118 residue plays a critical role in the RB phenotype. The discovery of a novel TSWV-RB Mexican isolate with the presence of C118F substitution highlights a not previously described viral adaptation in the genus Orthotospovirus, and hence, the necessity of further crop monitoring to alert the establishment of novel RB isolates in cultivated tomatoes. 相似文献
949.
Martina Ferraguti Sergio Magallanes Jéssica Jiménez-Peñuela Josué Martínez-de la Puente Luz Garcia-Longoria Jordi Figuerola Jaime Muriel Tamer Albayrak Staffan Bensch Camille Bonneaud Rohan H. Clarke Gábor Á. Czirják Dimitar Dimitrov Kathya Espinoza John G. Ewen Farah Ishtiaq Wendy Flores-Saavedra László Zsolt Garamszegi Olof Hellgren Dita Horakova Kathryn P. Huyvaert Henrik Jensen Asta Križanauskienė Marcos R. Lima Charlene Lujan-Vega Eyðfinn Magnussen Lynn B. Martin Kevin D. Matson Anders Pape Møller Pavel Munclinger Vaidas Palinauskas Péter L. Pap Javier Pérez-Tris Swen C. Renner Robert Ricklefs Sergio Scebba Ravinder N. M. Sehgal Manuel Soler Eszter Szöllősi Gediminas Valkiūnas Helena Westerdahl Pavel Zehtindjiev Alfonso Marzal 《Global Ecology and Biogeography》2023,32(5):809-823