全文获取类型
收费全文 | 10763篇 |
免费 | 993篇 |
国内免费 | 12篇 |
出版年
2023年 | 34篇 |
2022年 | 112篇 |
2021年 | 225篇 |
2020年 | 115篇 |
2019年 | 155篇 |
2018年 | 200篇 |
2017年 | 192篇 |
2016年 | 284篇 |
2015年 | 522篇 |
2014年 | 551篇 |
2013年 | 728篇 |
2012年 | 874篇 |
2011年 | 854篇 |
2010年 | 542篇 |
2009年 | 466篇 |
2008年 | 729篇 |
2007年 | 666篇 |
2006年 | 635篇 |
2005年 | 599篇 |
2004年 | 536篇 |
2003年 | 508篇 |
2002年 | 488篇 |
2001年 | 148篇 |
2000年 | 114篇 |
1999年 | 131篇 |
1998年 | 129篇 |
1997年 | 86篇 |
1996年 | 74篇 |
1995年 | 54篇 |
1994年 | 75篇 |
1993年 | 61篇 |
1992年 | 57篇 |
1991年 | 53篇 |
1990年 | 69篇 |
1989年 | 52篇 |
1988年 | 55篇 |
1987年 | 46篇 |
1986年 | 42篇 |
1985年 | 36篇 |
1984年 | 44篇 |
1983年 | 29篇 |
1982年 | 39篇 |
1981年 | 38篇 |
1980年 | 28篇 |
1979年 | 46篇 |
1978年 | 32篇 |
1977年 | 29篇 |
1974年 | 29篇 |
1973年 | 21篇 |
1972年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
921.
922.
923.
924.
925.
926.
Sandra Lavorel Matthew J. Colloff Sue Mcintyre Michael D. Doherty Helen T. Murphy Daniel J. Metcalfe Michael Dunlop Richard J. Williams Russell M. Wise Kristen J. Williams 《Global Change Biology》2015,21(1):12-31
Ecosystem services are typically valued for their immediate material or cultural benefits to human wellbeing, supported by regulating and supporting services. Under climate change, with more frequent stresses and novel shocks, 'climate adaptation services', are defined as the benefits to people from increased social ability to respond to change, provided by the capability of ecosystems to moderate and adapt to climate change and variability. They broaden the ecosystem services framework to assist decision makers in planning for an uncertain future with new choices and options. We present a generic framework for operationalising the adaptation services concept. Four steps guide the identification of intrinsic ecological mechanisms that facilitate the maintenance and emergence of ecosystem services during periods of change, and so materialise as adaptation services. We applied this framework for four contrasted Australian ecosystems. Comparative analyses enabled by the operational framework suggest that adaptation services that emerge during trajectories of ecological change are supported by common mechanisms: vegetation structural diversity, the role of keystone species or functional groups, response diversity and landscape connectivity, which underpin the persistence of function and the reassembly of ecological communities under severe climate change and variability. Such understanding should guide ecosystem management towards adaptation planning. 相似文献
927.
928.
Greg Hodge Hubertus Jersmann Hai B Tran Mark Holmes Paul N Reynolds Sandra Hodge 《Respiratory research》2015,16(1)
Background
Glucocorticoid (GC) resistance is a major barrier in COPD treatment. We have shown increased expression of the drug efflux pump, Pgp1 in cytotoxic/pro-inflammatory lymphocytes in COPD. Loss of lymphocyte co-stimulatory molecule CD28 (lymphocyte senescence) was associated with a further increase in their pro-inflammatory/cytotoxic potential and resistance to GC. We hypothesized that lymphocyte senescence and increased Pgp1 are also associated with down-regulation of the GC receptor (GCR).Methods
Blood was collected from 10 COPD and 10 healthy aged-matched controls. Flow cytometry was applied to assess intracellular pro-inflammatory cytokines, CD28, Pgp1, GCR, steroid binding and relative cytoplasm/nuclear GCR by CD28+ and CD28null T, NKT-like cells. GCR localization was confirmed by fluorescent microscopy.Results
COPD was associated with increased numbers of CD28nullCD8+ T and NKT-like cells. Loss of CD28 was associated with an increased percentage of T and NKT-like cells producing IFNγ or TNFα and associated with a loss of GCR and Dex-Fluor staining but unchanged Pgp1. There was a significant loss of GCR in CD8 + CD28null compared with CD8 + CD28+ T and NKT-like cells from both COPD and controls (eg, mean ± SEM 8 ± 3% GCR + CD8 + CD28null T-cells vs 49 ± 5% GCR + CD8 + CD28+ T-cells in COPD). There was a significant negative correlation between GCR expression and IFNγ and TNFα production by T and NKT-like cells(eg, COPD: T-cell IFNγ R = −.615; ) and with FEV1 in COPD (R = −.777).Conclusions
COPD is associated with loss of GCR in senescent CD28null and NKT-like cells suggesting alternative treatment options to GC are required to inhibit these pro-inflammatory/cytotoxic cells. 相似文献929.
930.
Hubert Pausch Hermann Schwarzenbacher Johann Burgstaller Krzysztof Flisikowski Christine Wurmser Sandra Jansen Simone Jung Angelika Schnieke Thomas Wittek Ruedi Fries 《BMC genomics》2015,16(1)