全文获取类型
收费全文 | 8832篇 |
免费 | 458篇 |
国内免费 | 18篇 |
专业分类
9308篇 |
出版年
2023年 | 46篇 |
2022年 | 41篇 |
2021年 | 123篇 |
2020年 | 120篇 |
2019年 | 150篇 |
2018年 | 333篇 |
2017年 | 300篇 |
2016年 | 393篇 |
2015年 | 323篇 |
2014年 | 408篇 |
2013年 | 622篇 |
2012年 | 527篇 |
2011年 | 661篇 |
2010年 | 397篇 |
2009年 | 269篇 |
2008年 | 445篇 |
2007年 | 499篇 |
2006年 | 524篇 |
2005年 | 464篇 |
2004年 | 388篇 |
2003年 | 448篇 |
2002年 | 331篇 |
2001年 | 227篇 |
2000年 | 203篇 |
1999年 | 138篇 |
1998年 | 77篇 |
1997年 | 37篇 |
1996年 | 22篇 |
1995年 | 29篇 |
1994年 | 28篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 42篇 |
1990年 | 33篇 |
1989年 | 24篇 |
1988年 | 24篇 |
1987年 | 35篇 |
1986年 | 23篇 |
1985年 | 36篇 |
1984年 | 24篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1979年 | 28篇 |
1978年 | 26篇 |
1977年 | 19篇 |
1974年 | 15篇 |
1972年 | 20篇 |
1953年 | 18篇 |
1952年 | 40篇 |
1887年 | 14篇 |
排序方式: 共有9308条查询结果,搜索用时 15 毫秒
131.
Plant Ecology - The impact of exotic annual Impatiens glandulifera on invaded European vegetation is ambiguous; there are studies reporting considerable negative as well as weak or even no impact... 相似文献
132.
133.
Grzegorz Garbacz Bartosz Kołodziej Mirko Koziolek Werner Weitschies Sandra Klein 《AAPS PharmSciTech》2013,14(2):517-522
The bicarbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions. However, its use in dissolution testing of solid oral dosage forms is very limited. The reason for this is the thermodynamic instability of the solution containing hydrogen carbonate ions and carbonic acid. The spontaneous loss of carbon dioxide (CO2) from the solution results in an uncontrolled increase of the pH. In order to maintain the pH on the desired level, either a CO2 loss must be completely avoided or the escaped CO2 has to be replaced by quantitative substitution, i.e. feeding the solution with the respective amount of gas, which re-acidifies the buffer after dissociation. The present work aimed at the development of a device enabling an automatic pH monitoring and regulation of hydrogen carbonate buffers during dissolution tests. 相似文献
134.
135.
Tanit Guitart Daria Picchioni David Pi?eyro Lluís Ribas de Pouplana 《Nucleic acids research》2013,41(13):6595-6608
The translation of genes encoded in the mitochondrial genome requires specific machinery that functions in the organelle. Among the many mutations linked to human disease that affect mitochondrial translation, several are localized to nuclear genes coding for mitochondrial aminoacyl-transfer RNA synthetases. The molecular significance of these mutations is poorly understood, but it is expected to be similar to that of the mutations affecting mitochondrial transfer RNAs. To better understand the molecular features of diseases caused by these mutations, and to improve their diagnosis and therapeutics, we have constructed a Drosophila melanogaster model disrupting the mitochondrial seryl-tRNA synthetase by RNA interference. At the molecular level, the knockdown generates a reduction in transfer RNA serylation, which correlates with the severity of the phenotype observed. The silencing compromises viability, longevity, motility and tissue development. At the cellular level, the knockdown alters mitochondrial morphology, biogenesis and function, and induces lactic acidosis and reactive oxygen species accumulation. We report that administration of antioxidant compounds has a palliative effect of some of these phenotypes. In conclusion, the fly model generated in this work reproduces typical characteristics of pathologies caused by mutations in the mitochondrial aminoacylation system, and can be useful to assess therapeutic approaches. 相似文献
136.
Jan Piťha 《Cell and tissue research》1968,90(4):563-569
Summary Paneth cells of rabbit small intestine almost constantly contain inclusions of variable size which consist of two components. The first consists of cylindrical bodies formed by concentric or spiral dense lamellae. The second is formed by tubules with triple-layered walls which may be arranged in a hexagonal pattern. The density of arrangement of both components is variable. The structure of inclusions is discussed in relation to their composition and derivation and lipid or lipoprotein composition is assumed. 相似文献
137.
138.
Meizhi Xu Xu Gu Nengsong Liang Xinxin Bian Hong Wang Yaxin Qin Limin Pi Shuang Wu 《植物学报(英文版)》2020,62(7):897-911
Root stem cell niche (SCN) consists of a quiescent center (QC) and surrounding stem cells. Disrupted symplastic communication leads to loss of stemness in the whole SCN. Several SCN regulators were reported to move between cells for SCN maintenance. However, single mutant of these regulators is insufficient to abolish QC stemness despite the high differentiation rate in surrounding stem cells. To dissect the mechanism behind such distinct stemness in SCN, we combined the mis‐expression strategy with pWOX5:icals3m system in which QC is symplastically isolated. We found the starch accumulation in QC could be synergistically repressed by WUSCHEL‐RELATED HOMEOBOX 5 (WOX5), SHORT‐ROOT (SHR), SCARCROW (SCR), and PLETHORA (PLT). Like PLTs, other core regulators also exhibited dimorphic functions by inhibiting differentiation at a higher dose while promoting cell division at a low protein level. Being located in the center of the intersected expression zones, QC cells receive the highest level of core regulators, forming the most robust stemness within SCN. WUSCHEL‐RELATED HOMEOBOX 5 was sufficient to activate PLT1/2 expression, contributing to the QC‐enriched PLTs. Our results provide experimental evidence supporting the long‐standing hypothesis that the combination of spatial expression, synergistic function and dosage effect of core regulators result in spatially distinct stemness in SCN. 相似文献
139.
Bączyk Justyna Gogiel Tomasz Wolańska Małgorzata Bruczko Marta Guszczyn Tomasz Popko Janusz Romanowicz Lech 《International journal of peptide research and therapeutics》2020,26(1):271-280
International Journal of Peptide Research and Therapeutics - The progressive damage of human articular cartilage is associated with loss of integrity of its extracellular matrix components. Their... 相似文献