全文获取类型
收费全文 | 4621篇 |
免费 | 304篇 |
国内免费 | 13篇 |
出版年
2023年 | 31篇 |
2022年 | 48篇 |
2021年 | 106篇 |
2020年 | 54篇 |
2019年 | 64篇 |
2018年 | 117篇 |
2017年 | 77篇 |
2016年 | 114篇 |
2015年 | 186篇 |
2014年 | 182篇 |
2013年 | 217篇 |
2012年 | 250篇 |
2011年 | 238篇 |
2010年 | 172篇 |
2009年 | 203篇 |
2008年 | 184篇 |
2007年 | 161篇 |
2006年 | 130篇 |
2005年 | 108篇 |
2004年 | 126篇 |
2003年 | 97篇 |
2002年 | 65篇 |
2001年 | 32篇 |
2000年 | 29篇 |
1999年 | 39篇 |
1998年 | 45篇 |
1997年 | 49篇 |
1996年 | 43篇 |
1995年 | 33篇 |
1994年 | 31篇 |
1992年 | 39篇 |
1990年 | 33篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 28篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1981年 | 23篇 |
1979年 | 26篇 |
1959年 | 51篇 |
1958年 | 123篇 |
1957年 | 137篇 |
1956年 | 134篇 |
1955年 | 149篇 |
1954年 | 150篇 |
1953年 | 120篇 |
1952年 | 104篇 |
1951年 | 98篇 |
1950年 | 60篇 |
1948年 | 24篇 |
排序方式: 共有4938条查询结果,搜索用时 781 毫秒
1.
The revision of the antarctic–subantarctic species Orchomenopsis reducta Schellenberg, 1931, has led to its attribution to a new, highly apomorphic genus: Falklandia gen.n. A new definition of the uristid group is given and Falklandia with 36 other lysianassoid genera are attributed to this supposedly monophyletic group. 相似文献
2.
3.
4.
Guochun Yan Kyle Reeves Dominique Foix Zhujie Li Claudio Cometto Sathiya Mariyappan Mathieu Salanne Jean‐Marie Tarascon 《Liver Transplantation》2019,9(41)
The Na‐ion battery is recognized as a possible alternative to the Li‐ion battery for applications where power and cost override energy density performance. However, the increasing instability of their electrolyte with temperature is still problematic. Thus, a central question remains how to design Na‐based electrolytes. Here, the discovery of a Na‐based electrolyte formulation is reported which enlists four additives (vinylene carbonate, succinonitrile, 1,3‐propane sultone, and sodium difluoro(oxalate)borate) in proper quantities that synergistically combine their positive attributes to enable a stable solid electrolyte interphase at both negative and positive electrodes surface at 55 °C. Moreover, the role of each additive that consists in producing specific NaF coatings, thin elastomers, sulfate‐based deposits, and so on via combined impedance and X‐ray photoelectron spectroscopy is rationalized. It is demonstrated that empirical electrolyte design rules previously established for Li‐ion technology together with theoretical guidance is vital in the quest for better Na‐based electrolytes that can be extended to other chemistries. Overall, this finding, which is implemented to 18 650 cells, widens the route to the rapid development of the Na‐ion technology based on Na3V2(PO4)2F3/C chemistry. 相似文献
5.
Cyanide-Resistant Root Respiration and Tap Root Formation in Two Subspecies of Hypochaeris radicata 总被引:1,自引:0,他引:1
Root respiration of the tap root forming species Hypochaeris radicata L. was measured during tap root formation. A comparison was made of two subspecies: H. radicata L. ssp. radicata L., a subspecies from relatively rich soils, and H. radicata L. ssp. ericetorum Van Soest, a subspecies from poor acidic soils. Root respiration was high and to a large extent inhibited by hydroxamic acid (SHAM) before the start of the tap root formation, indicating a high activity of an alternative non-phosphorylative electron transport chain. The rate of root respiration was much lower and less sensitive to SHAM when a considerable tap root was present. However, root respiration was also cyanide-resistant when a tap root was present, indicating that the alternative pathway was still present. A decreased rate of root respiration coincided with an increase of the content of storage carbohydrates, mainly in the tap root. The level of reducing sugars was constant throughout the experimental period, and it was concluded that the activity of the alternative oxidative pathway was significant in oxidation of sugars that could not be utilized for purposes like energy production, the formation of intermediates for growth or for storage. Root respiration decreased after the formation of a tap root. This decrease could neither be attributed to a gradual disappearance of the alternative chain, nor to a decreased level of reducing sugars. No differences in respiratory metabolism between the two subspecies have been observed, suggesting that a high activity of the alternative oxidative pathway is not significant in adaptation of the present two subspecies to relatively nutrient-rich or poor soils. 相似文献
6.
7.
8.
9.
10.