全文获取类型
收费全文 | 130226篇 |
免费 | 3754篇 |
国内免费 | 830篇 |
出版年
2023年 | 212篇 |
2022年 | 370篇 |
2021年 | 1061篇 |
2020年 | 610篇 |
2019年 | 773篇 |
2018年 | 12550篇 |
2017年 | 11264篇 |
2016年 | 8517篇 |
2015年 | 2558篇 |
2014年 | 2479篇 |
2013年 | 2619篇 |
2012年 | 7444篇 |
2011年 | 15625篇 |
2010年 | 13730篇 |
2009年 | 9777篇 |
2008年 | 12021篇 |
2007年 | 13496篇 |
2006年 | 2368篇 |
2005年 | 2499篇 |
2004年 | 2788篇 |
2003年 | 2731篇 |
2002年 | 2375篇 |
2001年 | 591篇 |
2000年 | 395篇 |
1999年 | 364篇 |
1998年 | 420篇 |
1997年 | 293篇 |
1996年 | 254篇 |
1995年 | 209篇 |
1994年 | 220篇 |
1993年 | 248篇 |
1992年 | 236篇 |
1991年 | 240篇 |
1990年 | 196篇 |
1989年 | 172篇 |
1988年 | 190篇 |
1987年 | 175篇 |
1986年 | 128篇 |
1985年 | 129篇 |
1984年 | 172篇 |
1983年 | 141篇 |
1982年 | 155篇 |
1981年 | 145篇 |
1980年 | 134篇 |
1979年 | 103篇 |
1978年 | 107篇 |
1977年 | 99篇 |
1973年 | 83篇 |
1972年 | 310篇 |
1971年 | 331篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Kathryn L. Butler Vijayakrishnan Ambravaneswaran Nitin Agrawal Maryelizabeth Bilodeau Mehmet Toner Ronald G. Tompkins Shawn Fagan Daniel Irimia 《PloS one》2010,5(7)
Thermal injury triggers a fulminant inflammatory cascade that heralds shock, end-organ failure, and ultimately sepsis and death. Emerging evidence points to a critical role for the innate immune system, and several studies had documented concurrent impairment in neutrophil chemotaxis with these post-burn inflammatory changes. While a few studies suggest that a link between neutrophil motility and patient mortality might exist, so far, cumbersome assays have prohibited exploration of the prognostic and diagnostic significance of chemotaxis after burn injury. To address this need, we developed a microfluidic device that is simple to operate and allows for precise and robust measurements of chemotaxis speed and persistence characteristics at single-cell resolution. Using this assay, we established a reference set of migration speed values for neutrophils from healthy subjects. Comparisons with samples from burn patients revealed impaired directional migration speed starting as early as 24 hours after burn injury, reaching a minimum at 72–120 hours, correlated to the size of the burn injury and potentially serving as an early indicator for concurrent infections. Further characterization of neutrophil chemotaxis using this new assay may have important diagnostic implications not only for burn patients but also for patients afflicted by other diseases that compromise neutrophil functions. 相似文献
113.
114.
Kevin J. Beiler Suzanne W. Simard Valerie LeMay Daniel M. Durall 《Molecular ecology》2012,21(24):6163-6174
Understanding ectomycorrhizal fungal (EMF) community structure is limited by a lack of taxonomic resolution and autecological information. Rhizopogon vesiculosus and Rhizopogon vinicolor (Basidiomycota) are morphologically and genetically related species. They are dominant members of interior Douglas‐fir (Pseudotsuga menziesii var. glauca) EMF communities, but mechanisms leading to their coexistence are unknown. We investigated the microsite associations and foraging strategy of individual R. vesiculosus and R. vinicolor genets. Mycelia spatial patterns, pervasiveness and root colonization patterns of fungal genets were compared between Rhizopogon species and between xeric and mesic soil moisture regimes. Rhizopogon spp. mycelia were systematically excavated from the soil and identified using microsatellite DNA markers. Rhizopogon vesiculosus mycelia occurred at greater depth, were more spatially pervasive, and colonized more tree roots than R. vinicolor mycelia. Both species were frequently encountered in organic layers and between the interface of organic and mineral horizons. They were particularly abundant within microsites associated with soil moisture retention. The occurrence of R. vesiculosus shifted in the presence of R. vinicolor towards mineral soil horizons, where R. vinicolor was mostly absent. This suggests that competition and foraging strategy may contribute towards the vertical partitioning observed between these species. Rhizopogon vesiculosus and R. vinicolor mycelia systems occurred at greater mean depths and were more pervasive in mesic plots compared with xeric plots. The spatial continuity and number of trees colonized by genets of each species did not significantly differ between soil moisture regimes. 相似文献
115.
116.
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117.
Dana M. Bergstrom George R. Stewart Patricia M. Selkirk Susanne Schmidt 《Oecologia》2002,130(2):309-314
'15N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '15N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '15N signatures of peat layers. At two sites 15N-enriched peat '15N signatures of up to +17 were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '15N. Less 15N enriched '15N signatures (e.g. -1.9 to +3.9) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that 15N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology. 相似文献
118.
119.
120.