全文获取类型
收费全文 | 1109篇 |
免费 | 108篇 |
国内免费 | 3篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 17篇 |
2016年 | 39篇 |
2015年 | 58篇 |
2014年 | 60篇 |
2013年 | 82篇 |
2012年 | 86篇 |
2011年 | 96篇 |
2010年 | 52篇 |
2009年 | 39篇 |
2008年 | 56篇 |
2007年 | 43篇 |
2006年 | 42篇 |
2005年 | 45篇 |
2004年 | 49篇 |
2003年 | 39篇 |
2002年 | 40篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 24篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1973年 | 9篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有1220条查询结果,搜索用时 15 毫秒
91.
92.
93.
Sweet pepper ferredoxin-like protein ( pflp) gene as a novel selection marker for orchid transformation 总被引:6,自引:0,他引:6
A novel method for selection of transgenic plants utilizing the sweet pepper ( Capsicum annuum L.) ferredoxin-like protein ( pflp) gene as selection marker and Erwinia carotovora as the selection agent has been developed. An expression vector containing a pflp cDNA driven by a cauliflower mosaic virus 35S promoter was successfully transformed into protocorm-like bodies of Oncidium orchid by Agrobacterium tumefaciens and particle bombardment, respectively. Erwinia carotovora was used as a selection agent to screen transformants, thereby obtaining transgenic plants without the use of an antibiotic selection agent. A total of 32 independent transgenic orchid lines were obtained, out of which 9 transgenic lines (beta-glucuronidase positive) were randomly selected and confirmed by Southern and northern blot analyses. The transgenic orchid plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest the novel use of the pflp gene as a resistance selection marker in plant genetic engineering strategies. In the future, the use of the pflp gene as a selection marker may facilitate the use of smaller gene constructs due to removal of bulky antibiotic selection and reporter genes. These constructs can then be used to incorporate additional genes of choice. 相似文献
94.
95.
96.
We investigated bursting behavior in rodent trigeminal neurons. The essential mechanisms operating in the biological systems were determined based on testable predictions of mathematical models. Bursting activity in trigeminal motoneurons is consistent with a traditional mechanism employing a region of negative slope resistance in the steady-state current-voltage relationship (Smith, T. G. 1975. Nature. 253:450-452). However, the bursting dynamics of trigeminal interneurons is inconsistent with the traditional mechanisms, and is far more effectively explained by a new model of bursting that exploits the unique stability properties associated with spike threshold (Baer, S. M., T. Erneux, and J. Rinzel. 1989. SIAM J. Appl. Math. 49:55-71). 相似文献
97.
附睾内液体微环境对精子的成熟和贮藏是相当重要的。附睾液体的形成取决于附睾上皮的吸收与分泌功能,而先前的实验已经证明:这些吸收与分泌的活动是受到除神经激素以外旁分泌与自分泌的调控。虽然肾素血管紧张素系统(RAS)在很多组织上旁分泌与自分泌的作用已多有报导,但其在附睾的存在及作用仍鲜为人知。本综述总结了本实验室在这方面的研究结果,通过使用不同的实验方法,例如,免疫组织化学,放射免疫分析,分子生物学及短路电流电生理学方法,我们得到的结果显示了RAS主要成员在附睾的分布(Fig.1)和表达,并阐明了血管紧张素II对附睾阴离子分泌的调控作用(Figs.2&3)。本综述还就血管紧张素II对附睾旁分泌与自分泌的作用及其机制(Fig.4),以及对精子功能的作用进行了讨论。 相似文献
98.
99.
Fei-Yuan Hsiao Li-Ning Peng Yu-Wen Wen Chih-Kuang Liang Pei-Ning Wang Liang-Kung Chen 《PloS one》2015,10(5)
Objective
To explore the healthcare resource utilization, psychotropic drug use and mortality of older people with dementia.Design
A nationwide propensity score-matched cohort study.Setting
National Health Insurance Research database.Participants
A total of 32,649 elderly people with dementia and their propensity-score matched controls (n=32,649).Measurements
Outpatient visits, inpatient care, psychotropic drug use, in-hospital mortality and all-cause mortality at 90 and 365 days.Results
Compared to the non-dementia group, a higher proportion of patients with dementia used inpatient services (1 year after index date: 20.91% vs. 9.55%), and the dementia group had more outpatient visits (median [standard deviation]: 7.00 [8.87] vs. 3.00 [8.30]). Furthermore, dementia cases with acute admission had the highest psychotropic drug utilization both at baseline and at the post-index dates (difference-in-differences: all <0.001). Dementia was associated with an increased risk of all-cause mortality (90 days, Odds ratio (OR)=1.85 [95%CI 1.67-2.05], p<0.001; 365 days, OR=1.59 [1.50-1.69], p<0.001) and in-hospital mortality (90 days, OR=1.97 [1.71-2.27], p<0.001; 365 days, OR=1.82 [1.61-2.05], p<0.001) compared to matched controls.Conclusions
When older people with dementia are admitted for acute illnesses, they may increase their use of psychotropic agents and their risk of death, particularly in-hospital mortality. 相似文献100.