全文获取类型
收费全文 | 583篇 |
免费 | 51篇 |
专业分类
634篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 16篇 |
2017年 | 4篇 |
2016年 | 13篇 |
2015年 | 22篇 |
2014年 | 35篇 |
2013年 | 38篇 |
2012年 | 44篇 |
2011年 | 45篇 |
2010年 | 17篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 42篇 |
2006年 | 23篇 |
2005年 | 44篇 |
2004年 | 33篇 |
2003年 | 33篇 |
2002年 | 31篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1972年 | 2篇 |
1969年 | 7篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1962年 | 1篇 |
1934年 | 1篇 |
1919年 | 2篇 |
排序方式: 共有634条查询结果,搜索用时 0 毫秒
111.
112.
Diet of Neotropical parrots is independent of phylogeny but correlates with body size and geographical range 下载免费PDF全文
Analia Benavidez Facundo Xavier Palacio Luis Osvaldo Rivera Ada Lilian Echevarria Natalia Politi 《Ibis》2018,160(4):742-754
Body mass and geographical range are two main drivers of diet in animals, yet how these factors influence diet in the morphologically and ecologically diverse avian group of Psittaciformes is little known. We reviewed current knowledge of the diet of Neotropical parrots and assessed the relation between diet (breadth and composition), phylogeny, body mass and geographical range. Diet has been documented for 98 of 165 species, but information is available only for 34 of 59 threatened species, and countries with high species diversity (> 20 species) had few studies (one to seven). Neotropical parrot species consumed 1293 plant species of 125 families. When assessing the relative frequency of different food items in the diet (seed, fruits, flowers, leaves, nectar, bark and stems), we found that parrots mostly exploited seeds (41.9%) and fruits (38.3%) of native species. Diet overlap was very low among genera (0.006–0.321). At the species level, geographical range and body size explained the variation in diet composition. In particular, small parrots of restricted distribution had a distinct diet composition relative to either large or widely distributed species. Although body size and geographical range showed phylogenetic inertia, diet was independent of phylogenetic history. Our review not only reveals ecological factors explaining diet in a generalist group but also exposes information gaps across the Neotropical region. 相似文献
113.
Appino S Pregel P Manuali E Vincenti L Rota A Carnieletto P Tiberi C Bollo E 《Animal reproduction science》2007,98(3-4):350-356
Bovine infertility is a major cause of loss in the livestock industry. In the present study bovine oviduct cell cultures were infected with a Chlamydophila abortus strain. A direct evaluation of infection was performed by means of May Grünwald-Giemsa and immunocytochemistry for chlamydial LPS, which revealed inclusion bodies and vacuolisation. SEM and TEM analysis of infected cells showed various degrees of cell damage and conglutination of microvilli. This finding suggests that cattle infertility may result from an alteration of oviduct environment caused by multiplication of C. abortus. This microorganism, among other infectious agents, could be considered a potential causative agent of bovine infertility. 相似文献
114.
Malavasi F Deaglio S Ferrero E Funaro A Sancho J Ausiello CM Ortolan E Vaisitti T Zubiaur M Fedele G Aydin S Tibaldi EV Durelli I Lusso R Cozno F Horenstein AL 《Molecular medicine (Cambridge, Mass.)》2006,12(11-12):334-341
This paper reviews some of the results and the speculations presented at the Torino CD38 Meeting in June, 2006 and focused on CD38 and CD157 seen as a family of molecules acting as surface receptors of immune cells. This partisan view was adopted in the attempt to combine the enzymatic functions with what the immunologists consider key functions in different cell models. At the moment, it is unclear whether the two functions are correlated, indifferent, or independent. Here we present conclusions inferred exclusively on human cell models, namely T and B lymphocytes, dendritic cells, and granulocytes. As an extra analytical tool, we try to follow in the history of life when the enzymatic and receptorial functions were generated, mixing ontogeny, membrane localization, and cell anchorage. 相似文献
115.
116.
Valeria Edefonti Francesca Bravi Katherine Turner Ettore Beghi Maria Paola Canevini Monica Ferraroni Ada Piazzini 《BMC neurology》2011,11(1):33
Background
The potential effect of age-related factors on health-related quality of life (HRQOL) of patients with epilepsy has rarely been analyzed in the literature. 相似文献117.
118.
Katrin B?ttger Haralambos Hatzikirou Anja Voss-B?hme Elisabetta Ada Cavalcanti-Adam Miguel A. Herrero Andreas Deutsch 《PLoS computational biology》2015,11(9)
Tumor cells develop different strategies to cope with changing microenvironmental conditions. A prominent example is the adaptive phenotypic switching between cell migration and proliferation. While it has been shown that the migration-proliferation plasticity influences tumor spread, it remains unclear how this particular phenotypic plasticity affects overall tumor growth, in particular initiation and persistence. To address this problem, we formulate and study a mathematical model of spatio-temporal tumor dynamics which incorporates the microenvironmental influence through a local cell density dependence. Our analysis reveals that two dynamic regimes can be distinguished. If cell motility is allowed to increase with local cell density, any tumor cell population will persist in time, irrespective of its initial size. On the contrary, if cell motility is assumed to decrease with respect to local cell density, any tumor population below a certain size threshold will eventually extinguish, a fact usually termed as Allee effect in ecology. These results suggest that strategies aimed at modulating migration are worth to be explored as alternatives to those mainly focused at keeping tumor proliferation under control. 相似文献
119.
120.
Leyi Gong Yun-Chou Tan Genevieve Boice Sarah Abbot Kristen McCaleb Pravin Iyer Fengrong Zuo Joseph Dal Porto Brian Wong Sue Jin Alice Chang Patricia Tran Gary Hsieh Linghao Niu Ada Shao Deborah Reuter Christine M. Lukacs R. Ursula Kammlott Andreas Kuglstatter David Goldstein 《Bioorganic & medicinal chemistry letters》2012,22(24):7381-7387
A novel series of highly selective JNK inhibitors based on the 4-quinolone scaffold was designed and synthesized. Structure based drug design was utilized to guide the compound design as well as improvements in the physicochemical properties of the series. Compound (13c) has an IC50 of 62/170 nM for JNK1/2, excellent kinase selectivity and impressive efficacy in a rodent asthma model. 相似文献