首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11021篇
  免费   983篇
  国内免费   71篇
  2024年   17篇
  2023年   100篇
  2022年   190篇
  2021年   359篇
  2020年   232篇
  2019年   319篇
  2018年   340篇
  2017年   335篇
  2016年   440篇
  2015年   666篇
  2014年   673篇
  2013年   832篇
  2012年   968篇
  2011年   935篇
  2010年   622篇
  2009年   506篇
  2008年   635篇
  2007年   596篇
  2006年   504篇
  2005年   435篇
  2004年   454篇
  2003年   346篇
  2002年   332篇
  2001年   103篇
  2000年   82篇
  1999年   83篇
  1998年   73篇
  1997年   65篇
  1996年   60篇
  1995年   49篇
  1994年   47篇
  1993年   51篇
  1992年   55篇
  1991年   50篇
  1990年   46篇
  1989年   43篇
  1988年   28篇
  1987年   28篇
  1986年   26篇
  1985年   33篇
  1984年   34篇
  1983年   23篇
  1982年   34篇
  1981年   18篇
  1980年   17篇
  1979年   19篇
  1978年   13篇
  1977年   16篇
  1975年   14篇
  1967年   11篇
排序方式: 共有10000条查询结果,搜索用时 99 毫秒
141.
Alzheimer’s disease (AD) is characterized by the appearance of amyloid‐β plaques, neurofibrillary tangles, and inflammation in brain regions involved in memory. Using mass spectrometry, we have quantified the phosphoproteome of the CK‐p25, 5XFAD, and Tau P301S mouse models of neurodegeneration. We identified a shared response involving Siglec‐F which was upregulated on a subset of reactive microglia. The human paralog Siglec‐8 was also upregulated on microglia in AD. Siglec‐F and Siglec‐8 were upregulated following microglial activation with interferon gamma (IFNγ) in BV‐2 cell line and human stem cell‐derived microglia models. Siglec‐F overexpression activates an endocytic and pyroptotic inflammatory response in BV‐2 cells, dependent on its sialic acid substrates and immunoreceptor tyrosine‐based inhibition motif (ITIM) phosphorylation sites. Related human Siglecs induced a similar response in BV‐2 cells. Collectively, our results point to an important role for mouse Siglec‐F and human Siglec‐8 in regulating microglial activation during neurodegeneration.  相似文献   
142.
143.
Ecosystems - Ecotones can form hot spots of biodiversity by containing species from multiple ecosystems. Because biodiversity is often linked to ecological function, we posit that rates of key...  相似文献   
144.
Ecosystems - Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered...  相似文献   
145.
Many studies have documented the individual effects of variables such as vegetation, long‐term climate and short‐term weather on biodiversity. Few, however, have explicitly explored how interactions among these major drivers can influence species abundance. We used data from a 15‐year study (2002–2017) in the endangered temperate woodlands of south‐eastern Australia to test hypotheses associated with the effects of vegetation type, long‐term climate and short‐term weather on population trajectories of seven species of (largely) nocturnal mammals and birds. Despite prolonged drought conditions, there was a significant increase in the abundance of some species over time (e.g. the Eastern Grey Kangaroo). It is possible that destocking of domestic livestock may have reduced competition with Kangaroos, thereby facilitating increases in abundance. The Common Brushtail Possum and Common Ringtail Possum were significantly less likely to occur in replanted woodlands, possibly because of the paucity of nesting sites. We found no evidence that replanted woodlands are refuges for exotic pest species like the European Rabbit and Red Fox. Short‐ and long‐term rainfall and vegetation type had important independent and combined effects on animal abundance. That is, responses to periods of high short‐term rainfall were dependent on vegetation type and whether sites occurred in long‐term climatically wet versus climatically dry locations. For example, the Red Fox responded positively to high levels of short‐term rainfall, but only at climatically dry sites. Our results highlight the complementary value of different vegetation types across the landscape and the context‐specific responses of animals to short‐term fluctuations in moisture availability. They also underscore the value of long‐term monitoring at a landscape scale for examining how multiple interacting factors influence trends in animal abundance.  相似文献   
146.
The current SARS-CoV-2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID-19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS-CoV-2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS-CoV-2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS-CoV-2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state-of-the-art nucleic acid sequencing technologies, we can follow in detail how SARS-CoV-2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS-CoV-2 variants across the globe should be of key interest in our fight against the pandemic.  相似文献   
147.
148.
149.
150.
We argue that the need for a quality seed supply chain is a major bottleneck for the restoration of Chile's native ecosystems, thus supplementing the list of bottlenecks proposed by Bannister et al. in 2018. Specifically, there is a need for defining seed transfer zones, developing standards and capacities for properly collecting and storing seeds, reducing information gaps on seed physiology and longevity, and implementing an efficient seed supply chain with certification of seed origin and quality. Without such capacities, countries are unlikely to meet their restoration commitments. Although we focus on bottlenecks in Chile, the issues we raise are relevant to other countries and thus the global agenda for ecological restoration.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号