全文获取类型
收费全文 | 18826篇 |
免费 | 1635篇 |
国内免费 | 1832篇 |
出版年
2024年 | 36篇 |
2023年 | 258篇 |
2022年 | 328篇 |
2021年 | 1105篇 |
2020年 | 801篇 |
2019年 | 913篇 |
2018年 | 839篇 |
2017年 | 619篇 |
2016年 | 866篇 |
2015年 | 1266篇 |
2014年 | 1412篇 |
2013年 | 1576篇 |
2012年 | 1805篇 |
2011年 | 1655篇 |
2010年 | 969篇 |
2009年 | 923篇 |
2008年 | 988篇 |
2007年 | 830篇 |
2006年 | 807篇 |
2005年 | 541篇 |
2004年 | 518篇 |
2003年 | 476篇 |
2002年 | 429篇 |
2001年 | 325篇 |
2000年 | 270篇 |
1999年 | 264篇 |
1998年 | 204篇 |
1997年 | 155篇 |
1996年 | 138篇 |
1995年 | 137篇 |
1994年 | 112篇 |
1993年 | 87篇 |
1992年 | 114篇 |
1991年 | 89篇 |
1990年 | 69篇 |
1989年 | 65篇 |
1988年 | 53篇 |
1987年 | 37篇 |
1986年 | 29篇 |
1985年 | 38篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1975年 | 11篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
1.
2.
3.
4.
D. R. Gustafsson L. Lei K. Luo X. Chu X. Zhao Q. Zhang F. Zou 《Medical and veterinary entomology》2019,33(3):407-419
In total, 366 birds representing 55 species in 24 families and eight orders, were examined for chewing lice (Phthiraptera: Amblycera, Ischnocera) in two high‐altitude localities in Yunnan Province, China. In Ailaoshan, almost all of the birds examined were resident passeriforms, of which 36% were parasitized by chewing lice. In Jinshanyakou, most birds were on migration, and included both passerine and non‐passerine birds. Of the passerine birds caught in Jinshanyakou, only one bird (0.7%) was parasitized by chewing lice. The prevalence of Myrsidea and Brueelia‐complex lice on birds caught in Ailaoshan was higher than in previous reports. Of the chewing lice identifiable to species level, three represent new records for China: Actornithophilus hoplopteri (Mjöberg, 1910), Maculinirmus ljosalfar Gustafsson & Bush, 2017 and Quadraceps sinensis Timmermann, 1954. In total, 17 new host records are included, of which we describe two as new species in the Brueelia‐complex: Guimaraesiella (Cicchinella) ailaoshanensis sp. nov. ex Schoeniparus dubius dubius (Hume, 1874) and G. (C.) montisodalis sp. nov. ex Fulvetta manipurensis tonkinensis Delacour & Jabouille, 1930. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:9FC3D8EE‐2CED‐4DBE‐A1DB‐471B71260D27 . 相似文献
5.
6.
7.
Summary . We study quantile regression (QR) for longitudinal measurements with nonignorable intermittent missing data and dropout. Compared to conventional mean regression, quantile regression can characterize the entire conditional distribution of the outcome variable, and is more robust to outliers and misspecification of the error distribution. We account for the within-subject correlation by introducing a ℓ2 penalty in the usual QR check function to shrink the subject-specific intercepts and slopes toward the common population values. The informative missing data are assumed to be related to the longitudinal outcome process through the shared latent random effects. We assess the performance of the proposed method using simulation studies, and illustrate it with data from a pediatric AIDS clinical trial. 相似文献
8.
9.
Q Yuan W M Jiang D Hollander E Leung J D Watson G W Krissansen 《Biochemical and biophysical research communications》1991,176(3):1443-1449
A cDNA clone encoding the N-terminal sequence of the murine integrin beta 7 subunit, a novel member of the leukocyte cell adhesion molecule subset (Leu-CAM), has been isolated. An N-terminal region of 13 contiguous amino acids deduced from the cDNA shows complete identity with the N-terminus of the 120 kDa subunit of the M290 antigen, a surface molecule found highly expressed on mouse intestinal intraepithelial lymphocytes (IEL). This unexpected result focuses two previously unconnected areas of research and suggests that integrins may have a special role to play in the defence of the gut mucosa. 相似文献
10.
Zou Ya-Jie Wang He-Xiang Zhang Jin-Xia 《International journal of peptide research and therapeutics》2019,25(4):1389-1396
International Journal of Peptide Research and Therapeutics - A novel peroxidase has been isolated from fresh fruiting bodies of the mushroom Pleurotus pulmonarius, with a purification protocol of... 相似文献