全文获取类型
收费全文 | 12413篇 |
免费 | 941篇 |
国内免费 | 2篇 |
专业分类
13356篇 |
出版年
2023年 | 82篇 |
2022年 | 152篇 |
2021年 | 252篇 |
2020年 | 168篇 |
2019年 | 204篇 |
2018年 | 323篇 |
2017年 | 270篇 |
2016年 | 424篇 |
2015年 | 654篇 |
2014年 | 670篇 |
2013年 | 898篇 |
2012年 | 1022篇 |
2011年 | 933篇 |
2010年 | 582篇 |
2009年 | 494篇 |
2008年 | 718篇 |
2007年 | 669篇 |
2006年 | 633篇 |
2005年 | 536篇 |
2004年 | 489篇 |
2003年 | 468篇 |
2002年 | 461篇 |
2001年 | 159篇 |
2000年 | 132篇 |
1999年 | 142篇 |
1998年 | 115篇 |
1997年 | 109篇 |
1996年 | 88篇 |
1995年 | 83篇 |
1994年 | 76篇 |
1993年 | 65篇 |
1992年 | 90篇 |
1991年 | 70篇 |
1990年 | 92篇 |
1989年 | 69篇 |
1988年 | 50篇 |
1987年 | 61篇 |
1986年 | 43篇 |
1985年 | 73篇 |
1984年 | 71篇 |
1983年 | 63篇 |
1982年 | 42篇 |
1981年 | 48篇 |
1980年 | 30篇 |
1979年 | 38篇 |
1975年 | 43篇 |
1974年 | 39篇 |
1973年 | 36篇 |
1971年 | 30篇 |
1968年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Christopher A. Fraker Camillo Ricordi Luca Inverardi Juan Domínguez‐Bendala 《Biology of the cell / under the auspices of the European Cell Biology Organization》2009,101(8):431-440
Beyond its role as an electron acceptor in aerobic respiration, oxygen is also a key effector of many developmental events. The oxygen‐sensing machinery and the very fabric of cell identity and function have been shown to be deeply intertwined. Here we take a first look at how oxygen might lie at the crossroads of at least two of the major molecular pathways that shape pancreatic development. Based on recent evidence and a thorough review of the literature, we present a theoretical model whereby evolving oxygen tensions might choreograph to a large extent the sequence of molecular events resulting in the development of the organ. In particular, we propose that lower oxygenation prior to the expansion of the vasculature may favour HIF (hypoxia inducible factor)‐mediated activation of Notch and repression of Wnt/β‐catenin signalling, limiting endocrine cell differentiation. With the development of vasculature and improved oxygen delivery to the developing organ, HIF‐mediated support for Notch signalling may decline while the β‐catenin‐directed Wnt signalling is favoured, which would support endocrine cell differentiation and perhaps exocrine cell proliferation/differentiation. 相似文献
4.
Adriana Calderaro Giovanna Piccolo Chiara Gorrini Sara Montecchini Sabina Rossi Maria Cristina Medici Carlo Chezzi Georges Snounou 《PloS one》2012,7(10)
It has been proposed that ovale malaria in humans is caused by two closely related but distinct species of malaria parasites: P. ovale curtisi and P. ovale wallikeri. We have extended and optimized a Real-time PCR assay targeting the parasite’s small subunit ribosomal RNA (ssrRNA) gene to detect both these species. When the assay was applied to 31 archival blood samples from patients diagnosed with P. ovale, it was found that the infection in 20 was due to P. ovale curtisi and in the remaining 11 to P. ovale wallikeri. Thus, this assay provides a useful tool that can be applied to epidemiological investigations of the two newly recognized distinct P. ovale species, that might reveal if these species also differ in their clinical manifestation, drugs susceptibility and relapse periodicity. The results presented confirm that P. ovale wallikeri is not confined to Southeast Asia, since the majority of the patients analyzed in this study had acquired their P. ovale infection in African countries, mostly situated in West Africa. 相似文献
5.
6.
7.
8.
Ronald J.A. Wanders Carlo Van Roermund Cor Lof Alfred J. Meijer 《Analytical biochemistry》1983,129(1):80-87
A simple fluorimetric assay for the determination of carbamoyl phosphate in tissue extracts is described. In the assay, production of ATP from carbamoyl phosphate and ADP by carbamate kinase is coupled to the formation of NADPH, using glucose, hexokinase, NADP+, and glucose-6-phosphate dehydrogenase. Production of NADPH in this system proved to be equal to the amount of carbamoyl phosphate present. 相似文献
9.