全文获取类型
收费全文 | 20643篇 |
免费 | 3203篇 |
国内免费 | 9283篇 |
出版年
2024年 | 87篇 |
2023年 | 647篇 |
2022年 | 1003篇 |
2021年 | 1338篇 |
2020年 | 1182篇 |
2019年 | 1358篇 |
2018年 | 971篇 |
2017年 | 938篇 |
2016年 | 1048篇 |
2015年 | 1545篇 |
2014年 | 1920篇 |
2013年 | 1699篇 |
2012年 | 2201篇 |
2011年 | 2097篇 |
2010年 | 1611篇 |
2009年 | 1694篇 |
2008年 | 1767篇 |
2007年 | 1597篇 |
2006年 | 1489篇 |
2005年 | 1220篇 |
2004年 | 933篇 |
2003年 | 825篇 |
2002年 | 769篇 |
2001年 | 642篇 |
2000年 | 562篇 |
1999年 | 417篇 |
1998年 | 160篇 |
1997年 | 153篇 |
1996年 | 115篇 |
1995年 | 101篇 |
1994年 | 98篇 |
1993年 | 103篇 |
1992年 | 107篇 |
1991年 | 92篇 |
1990年 | 78篇 |
1989年 | 66篇 |
1988年 | 50篇 |
1987年 | 50篇 |
1986年 | 49篇 |
1985年 | 55篇 |
1984年 | 37篇 |
1983年 | 24篇 |
1982年 | 40篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1978年 | 11篇 |
1972年 | 12篇 |
1971年 | 12篇 |
1970年 | 10篇 |
1969年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
Haiye Luan Baojian Guo Yuhan Pan Chao Lv Huiquan Shen Rugen Xu 《Plant Growth Regulation》2018,85(3):399-409
Waterlogging is one of the major stresses limiting crop production worldwide. The understanding of the mechanisms of plant adaptations to waterlogging stress helps improve plant tolerance to stress. In this study, physiological responses and morpho-anatomical adaptations of seven different barley genotypes were investigated under waterlogging stress. The results showed that the waterlogging-tolerant varieties (TX9425, Yerong, TF58) showed less reduction in plant height, SPAD (soil–plant analyses development analyses) value, tillers, shoot and root biomasses than did the waterlogging-sensitive varieties (Franklin, Naso Nijo, TF57). Under waterlogging stress condition, the tolerant genotypes also showed a much larger number of adventitious roots than did the sensitive genotypes. More intercellular spaces and better integrated chloroplast membrane structures were observed in the leaves of the waterlogging-tolerant cultivars, which is likely due to increased ethylene content, decreased ABA content and less accumulation of O2.?. The ability to form new adventitious roots and intercellular spaces in shoots can also be used as selection criteria in breeding barley for waterlogging tolerance. 相似文献
2.
Hai-Lun Chao 《PloS one》2015,10(5)
To report the results of a systematic review and meta-analysis examining whether weight loss interventions improve body image in obese/overweight individuals. Medline, Current Contents, and the Cochrane database were searched to identify studies involving obese/overweight adults who were enrolled in weight loss interventions in which body image was quantitatively assessed. Outcomes assessed were changes in body shape concern, body size dissatisfaction, and body satisfaction (intervention vs comparator/control group). Seven studies were included in the systematic review (4 in the meta-analysis). All but 1 study involved female participants only. The type of weight loss intervention varied between studies as did the type of control/comparator group. In 3 studies, there was no significant difference in body image outcomes, whereas in 4 studies, improvement in body image was significantly more pronounced in the intervention vs the control/comparator group. Meta-analysis revealed that improvements in body shape concern (standardized difference: -0.52; 95% confidence interval [CI]: -1.04 to 0.00), body size dissatisfaction (standardized difference: -0.66; 95% CI: -0.88 to -0.45), and body satisfaction (standardized difference: 0.74; 95% CI: 0.09 to 1.38) significantly favored the intervention over the comparator/control group (P<0.05). The results of this systematic review/meta-analysis lend support to the notion that weight loss interventions may improve body image. This is a noteworthy finding that has clear clinical applicability because body image affects psychological well-being and the ability of an individual to maintain weight loss. Future research should determine which weigh loss interventions are associated with optimal improvements in body image and maintenance of weight loss. 相似文献
3.
相邻的反向重复DNA片段有形成单链内二级结构的倾向,属于一种测序困难的DNA模板。解决RNAi载体插入的反向重复片段的测序问题,为该类载体正确性的测序验证奠定基础。采用常规分子克隆方法构建表达小麦TaATG2串联反向重复片段的RNAi载体,设计2种策略对经菌落PCR初步鉴定的载体进行测序验证:一种是以完整的载体质粒为模板进行测序;另一种是先对载体进行酶切处理,切除反向重复片段中的一个后对保留另一个片段的线性载体进行测序。结果表明,第一种测序策略受到串联反向重复片段形成的单链内部二级结构的影响,测序信号在反向重复片段处出现衰减或乱峰,无法读取序列。第二种测序策略排除了2个反向重复片段之间的干扰,保留在载体上的片段测序信号清晰,序列准确。采用酶切切除一个片段后进行测序的方法,经过2次酶切和2次测序可以有效地对载体上的2个反向重复片段分别进行序列测定,进而确认构建载体的正确性。 相似文献
4.
5.
6.
7.
8.
9.
10.
T Y Chao T M Chu 《Proceedings of the National Science Council, Republic of China. Part B, Life sciences》1990,14(4):223-227
The in vivo distribution of intravenously injected lymphokine activated killer (LAK) cells, generated in vitro with rIL-2 from normal murine splenocytes, was studied in BALB/c mice and compared with that of normal splenocytes. Both normal splenocytes and LAK cells were labeled with 51Cr, and the results were analyzed at 6, 24, and 48 hours after injection by localization index as the parameter. After injection through tail veins of mice, LAK cells were found to migrate to the spleen, lungs, liver, lymph nodes, bones and the kidneys. The apparent increased distribution pattern of LAK cells to the lung at 6 and 24 hours after injection was not detected when normal splenocytes were injected. Since almost one third of the injected LAK cells were found to localize in the spleen, it was postulated that splenectomy would affect the in vivo organ distribution of LAK cells. Accordingly, the in vivo distribution of LAK cells in splenectomized mice was further investigated. Results indicated that splenectomy enhanced the convergence of LAK cells to the lungs, liver, lymph nodes and bones. Therefore, splenectomy may augment the therapeutic effect of the adoptive transfer of LAK cells in pulmonary, hepatic, lymph node and bony metastases. 相似文献