全文获取类型
收费全文 | 4752篇 |
免费 | 394篇 |
国内免费 | 5篇 |
出版年
2022年 | 49篇 |
2021年 | 94篇 |
2020年 | 58篇 |
2019年 | 72篇 |
2018年 | 88篇 |
2017年 | 88篇 |
2016年 | 109篇 |
2015年 | 193篇 |
2014年 | 174篇 |
2013年 | 299篇 |
2012年 | 308篇 |
2011年 | 274篇 |
2010年 | 183篇 |
2009年 | 150篇 |
2008年 | 212篇 |
2007年 | 218篇 |
2006年 | 198篇 |
2005年 | 187篇 |
2004年 | 148篇 |
2003年 | 150篇 |
2002年 | 136篇 |
2001年 | 111篇 |
2000年 | 101篇 |
1999年 | 111篇 |
1998年 | 45篇 |
1997年 | 44篇 |
1996年 | 30篇 |
1995年 | 48篇 |
1993年 | 34篇 |
1992年 | 68篇 |
1991年 | 70篇 |
1990年 | 58篇 |
1989年 | 54篇 |
1988年 | 50篇 |
1987年 | 55篇 |
1986年 | 45篇 |
1985年 | 43篇 |
1984年 | 46篇 |
1983年 | 35篇 |
1982年 | 39篇 |
1981年 | 32篇 |
1979年 | 45篇 |
1978年 | 40篇 |
1977年 | 31篇 |
1976年 | 31篇 |
1975年 | 44篇 |
1973年 | 41篇 |
1972年 | 29篇 |
1971年 | 36篇 |
1967年 | 33篇 |
排序方式: 共有5151条查询结果,搜索用时 249 毫秒
1.
2.
Diego Sustaita Patty Finfrock Quickert Laura Patterson Laureen Barthman-Thompson Sarah Estrella 《The Journal of wildlife management》2011,75(6):1498-1507
We undertook a 2-year (2002–2004) mark–recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. © 2011 The Wildlife Society. 相似文献
3.
4.
Mingyue Wang Pranab K Mukherjee Jyotsna Chandra Ali Abdul Lattif Thomas S McCormick Mahmoud A Ghannoum 《BMC microbiology》2008,8(1):31
Background
We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed. 相似文献5.
Barakaeli Abdieli Ndosi Hansol Park Dongmin Lee Seongjun Choe Yeseul Kang Tilak Chandra Nath Mohammed Mebarek Bia Chatanun Eamudomkarn Hyeong-Kyu Jeon Keeseon S. Eom 《The Korean journal of parasitology》2020,58(6):653
Spirometra tapeworms (Cestoda: Diphyllobothriidae) collected from carnivorous mammals in Tanzania were identified by the DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and internal transcribed spacer 1 (ITS1), and by morphological characteristics. A total of 15 adult worms were collected from stool samples and carcasses of Panthera leo, Panthera pardus, and Crocuta crocuta in the Serengeti and Selous ecosystems of Tanzania. Three Spirometra species: S. theileri, S. ranarum and S. erinaceieuropaei were identified based on morphological features. Partial cox1 sequences (400 bp) of 10 specimens were revealed. Eight specimens showed 99.5% similarity with Spirometra theileri (), 1 specimen showed 99.5% similarity with the Korean S. erinaceieuropaei and 1 specimen had 99.5% similarity with Myanmar S. ranarum. Sequence homology estimates for the ITS1 region of S. theileri were 89.8% with S. erinaceieuropaei, 82.5% with S. decipiens, and 78.3% with S. ranarum; and 94.4% homology was observed between S. decipiens and S. ranarum. Phylogenetic analyses were performed with 4 species of Spirometra and 2 species of Dibothriocephalus (=Diphyllobothrium). By both ML and BI methods, cox1 and ITS1 gave well supported, congruent trees topology of S. erinaceieuropaei and S. theileri with S. decipiens and S. ranarum forming a clade. The Dibothriocephalus species were sisters of each other and collectively forming successive outgroups. Our findings confirmed that 3 Spirometra species (S. theileri, S. ranarum, and S. erinaceieuropaei) are distributed in the Serengeti and Selous ecosystems of Tanzania. MK955901相似文献
6.
7.
8.
S K Tandon A K Mathur J R Behari S V Chandra 《Acta biologica et medica Germanica》1975,34(11-12):1835-1842
Daily intraperitoneal administration of thorium nitrate produced progressive morphological and biochemical alterations with the increase in thorium concentration in rat testis. The degenerative changes in the seminiferous tubules increased with the duration of treatment and after 90 days calcification occurred in about 25% of the tubules and in the connective tissue of the tunica albuginea. The activity of adenosine triphosphatase and alkaline phosphatase increased markedly as a result of thorium administration. An attempt has been made to interrelate histopathological and enzymatic changes and the metal concentration in the testicular tissue. 相似文献
9.
10.