全文获取类型
收费全文 | 2579篇 |
免费 | 234篇 |
出版年
2021年 | 33篇 |
2020年 | 29篇 |
2019年 | 22篇 |
2018年 | 35篇 |
2017年 | 35篇 |
2016年 | 39篇 |
2015年 | 74篇 |
2014年 | 80篇 |
2013年 | 93篇 |
2012年 | 109篇 |
2011年 | 100篇 |
2010年 | 83篇 |
2009年 | 71篇 |
2008年 | 92篇 |
2007年 | 82篇 |
2006年 | 70篇 |
2005年 | 85篇 |
2004年 | 85篇 |
2003年 | 69篇 |
2002年 | 81篇 |
2001年 | 76篇 |
2000年 | 78篇 |
1999年 | 55篇 |
1998年 | 44篇 |
1997年 | 27篇 |
1996年 | 35篇 |
1994年 | 26篇 |
1993年 | 35篇 |
1992年 | 66篇 |
1991年 | 48篇 |
1990年 | 51篇 |
1989年 | 48篇 |
1988年 | 42篇 |
1987年 | 60篇 |
1986年 | 45篇 |
1985年 | 52篇 |
1984年 | 37篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 36篇 |
1978年 | 28篇 |
1977年 | 24篇 |
1975年 | 28篇 |
1973年 | 30篇 |
1972年 | 21篇 |
1971年 | 23篇 |
1969年 | 25篇 |
1967年 | 26篇 |
排序方式: 共有2813条查询结果,搜索用时 15 毫秒
121.
122.
Bijvoet G. P. Teske A. J. Chamuleau S. A. J. Hart E. A. Jansen R. Schaap J. 《Netherlands heart journal》2020,28(2):63-72
Netherlands Heart Journal - The optimal treatment strategy for asymptomatic patients with severe mitral valve regurgitation (MR) and preserved left ventricular (LV) function is challenging. This... 相似文献
123.
Rahman Daiyan Emma Catherine Lovell Bosi Huang Muhammad Zubair Joshua Leverett Qingran Zhang Sean Lim Jonathan Horlyck Jianbo Tang Xunyu Lu Kourosh Kalantar‐Zadeh Judy N. Hart Nicholas M. Bedford Rose Amal 《Liver Transplantation》2020,10(28)
In this study, scalable, flame spray synthesis is utilized to develop defective ZnO nanomaterials for the concurrent generation of H2 and CO during electrochemical CO2 reduction reactions (CO2RR). The designed ZnO achieves an H2/CO ratio of ≈1 with a large current density (j) of 40 mA cm?2 during long‐term continuous reaction at a cell voltage of 2.6 V. Through in situ atomic pair distribution function analysis, the remarkable stability of these ZnO structures is explored, addressing the knowledge gap in understanding the dynamics of oxide catalysts during CO2RR. Through optimization of synthesis conditions, ZnO facets are modulated which are shown to affect reaction selectivity, in agreement with theoretical calculations. These findings and insights on synthetic manipulation of active sites in defective metal‐oxides can be used as guidelines to develop active catalysts for syngas production for renewable power‐to‐X to generate a range of fuels and chemicals. 相似文献
124.
125.
126.
127.
128.
Yang Yang Hart Stephen C. McCorkle Emma P. Stacy Erin M. Barnes Morgan E. Hunsaker Carolyn T. Johnson Dale W. Berhe Asmeret Asefaw 《Ecosystems》2021,24(8):1853-1874
Ecosystems - Understanding the transport of dissolved organic carbon (DOC) and nitrogen (N) as water flows through headwater basins is important for predicting downstream water quality. With... 相似文献
129.
This study investigated how the current economic recession (since December 2007) has affected dog and cat relinquishment, adoption, and euthanasia at the Anti-Cruelty Society animal shelter in Chicago, Illinois. The study compared temporal patterns of the investigated statistics before (2000–2007) the start of the current recession with the patterns after the start of the recession (2008–2010). The results showed that once the guardianship (ownership) of a nonhuman animal had been established, the recession did not greatly affect the owner's decision on relinquishment—except for the relinquishment of senior dogs, which may be associated with increased costs of care. However, an unfavorable economic environment may have reduced adoption of animals. The consequences of a decline in adoptions might be reflected in an increase in the proportion or number of sheltered animals euthanized. This study demonstrated how monitoring changes in temporal patterns in these shelter statistics can help guide animal shelters to better prepare for the current recession. 相似文献
130.