全文获取类型
收费全文 | 6070篇 |
免费 | 707篇 |
国内免费 | 2篇 |
出版年
2023年 | 40篇 |
2022年 | 82篇 |
2021年 | 193篇 |
2020年 | 127篇 |
2019年 | 126篇 |
2018年 | 130篇 |
2017年 | 117篇 |
2016年 | 193篇 |
2015年 | 361篇 |
2014年 | 382篇 |
2013年 | 344篇 |
2012年 | 466篇 |
2011年 | 473篇 |
2010年 | 279篇 |
2009年 | 166篇 |
2008年 | 281篇 |
2007年 | 234篇 |
2006年 | 233篇 |
2005年 | 211篇 |
2004年 | 157篇 |
2003年 | 148篇 |
2002年 | 138篇 |
2001年 | 107篇 |
2000年 | 89篇 |
1999年 | 104篇 |
1998年 | 62篇 |
1997年 | 50篇 |
1996年 | 37篇 |
1995年 | 36篇 |
1993年 | 37篇 |
1992年 | 65篇 |
1991年 | 80篇 |
1990年 | 71篇 |
1989年 | 71篇 |
1988年 | 58篇 |
1987年 | 73篇 |
1986年 | 65篇 |
1985年 | 71篇 |
1984年 | 39篇 |
1983年 | 55篇 |
1981年 | 48篇 |
1980年 | 35篇 |
1979年 | 40篇 |
1978年 | 40篇 |
1976年 | 51篇 |
1975年 | 38篇 |
1974年 | 35篇 |
1973年 | 37篇 |
1972年 | 46篇 |
1971年 | 40篇 |
排序方式: 共有6779条查询结果,搜索用时 390 毫秒
1.
The sequential cytological events of the regeneration process, after partial excision of the gastrocnemius muscle in the rat, were followed by light and electron microscopy. During the first 2 days after injury leukocytes and macrophages infiltrate into the traumatized area. Myogenic regeneration is then characterized by mainly two repair mechanisms. Mononucleated cells, that populate the excised area, most probably fuse together to give rise to newly formed multinucleated myotubes that further develop to striated myofibers. Another mechanism involves the repair of injured muscle fibers by the possible fusion of mononucleated cells with their necrotic cut ends. Consequently, by addition of nuclei and new muscular material, sarcoplasmic outgrowths from the injured fibers are formed. It is concluded that mainly two repair mechanisms are involved in the regeneration process following partial excision of a muscle: addition of new muscle fibers in a process similar to that of embryonic myogenesis and also meristic growth from the injured fibers. 相似文献
2.
3.
4.
5.
Chromosomal RNA: an artifact of preparation? 总被引:2,自引:0,他引:2
6.
7.
Development and Phase 3 testing of the most advanced malaria vaccine, RTS,S/AS01, indicates that malaria vaccine R&D is moving into a new phase. Field trials of several research malaria vaccines have also confirmed that it is possible to impact the host-parasite relationship through vaccine-induced immune responses to multiple antigenic targets using different platforms. Other approaches have been appropriately tested but turned out to be disappointing after clinical evaluation. As the malaria community considers the potential role of a first-generation malaria vaccine in malaria control efforts, it is an apposite time to carefully document terminated and ongoing malaria vaccine research projects so that lessons learned can be applied to increase the chances of success for second-generation malaria vaccines over the next 10 years. The most comprehensive resource of malaria vaccine projects is a spreadsheet compiled by WHO thanks to the input from funding agencies, sponsors and investigators worldwide. This spreadsheet, available from WHO's website, is known as "the rainbow table". By summarizing the published and some unpublished information available for each project on the rainbow table, the most comprehensive review of malaria vaccine projects to be published in the last several years is provided below. 相似文献
8.
Lauren Petrullo Matthew J. Jorgensen Noah Snyder‐Mackler Amy Lu 《American journal of primatology》2019,81(10-11)
The human milk microbiome is vertically transmitted to offspring during the postnatal period and has emerged as a critical driver of infant immune and metabolic development. Despite this importance in humans, the milk microbiome of nonhuman primates remains largely unexplored. This dearth of comparative work precludes our ability to understand how species‐specific differences in the milk microbiome may differentially drive maternal effects and limits how translational models can be used to understand the role of vertically transmitted milk microbes in human development. Here, we present the first culture‐independent data on the milk microbiome of a nonhuman primate. We collected milk and matched fecal microbiome samples at early and late lactation from a cohort of captive lactating vervet monkeys (N = 15). We found that, similar to humans, the vervet monkey milk microbiome comprises a shared community of taxa that are universally present across individuals. However, unlike in humans, this shared community is dominated by the genera Lactobacillus, Bacteroides, and Prevotella. We also found that, in contrast to previous culture‐dependent studies in humans, the vervet milk microbiome exhibits greater alpha‐diversity than the gut microbiome across lactation. Finally, we did not find support for the translocation of microbes from the gut to the mammary gland within females (i.e., “entero‐mammary pathway”). Taken together, our results show that the vervet monkey milk microbiome is taxonomically diverse, distinct from the gut microbiome, and largely stable. These findings demonstrate that the milk microbiome is a unique substrate that may selectively favor the establishment and persistence of particular microbes across lactation and highlights the need for future experimental studies on the origin of microbes in milk. 相似文献
9.
ACTH stimulation of adenyl cyclase in adrenal homogenates 总被引:6,自引:0,他引:6
10.
Ranjan Muthukrishnan Lauren L. Sullivan Allison K. Shaw James D. Forester 《Ecology letters》2020,23(5):791-799
Most of the classical theory on species coexistence has been based on species‐level competitive trade‐offs. However, it is becoming apparent that plant species display high levels of trait plasticity. The implications of this plasticity are almost completely unknown for most coexistence theory. Here, we model a competition–colonisation trade‐off and incorporate trait plasticity to evaluate its effects on coexistence. Our simulations show that the classic competition–colonisation trade‐off is highly sensitive to environmental circumstances, and coexistence only occurs in narrow ranges of conditions. The inclusion of plasticity, which allows shifts in competitive hierarchies across the landscape, leads to coexistence across a much broader range of competitive and environmental conditions including disturbance levels, the magnitude of competitive differences between species, and landscape spatial patterning. Plasticity also increases the number of species that persist in simulations of multispecies assemblages. Plasticity may generally increase the robustness of coexistence mechanisms and be an important component of scaling coexistence theory to higher diversity communities. 相似文献