全文获取类型
收费全文 | 18257篇 |
免费 | 1675篇 |
国内免费 | 1694篇 |
出版年
2024年 | 37篇 |
2023年 | 190篇 |
2022年 | 419篇 |
2021年 | 737篇 |
2020年 | 560篇 |
2019年 | 747篇 |
2018年 | 763篇 |
2017年 | 567篇 |
2016年 | 781篇 |
2015年 | 1162篇 |
2014年 | 1410篇 |
2013年 | 1414篇 |
2012年 | 1793篇 |
2011年 | 1688篇 |
2010年 | 1046篇 |
2009年 | 919篇 |
2008年 | 1161篇 |
2007年 | 1071篇 |
2006年 | 872篇 |
2005年 | 754篇 |
2004年 | 651篇 |
2003年 | 602篇 |
2002年 | 554篇 |
2001年 | 249篇 |
2000年 | 230篇 |
1999年 | 217篇 |
1998年 | 149篇 |
1997年 | 117篇 |
1996年 | 71篇 |
1995年 | 64篇 |
1994年 | 59篇 |
1993年 | 41篇 |
1992年 | 63篇 |
1991年 | 52篇 |
1990年 | 53篇 |
1989年 | 34篇 |
1988年 | 33篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1978年 | 10篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 16篇 |
1973年 | 11篇 |
1970年 | 11篇 |
1969年 | 12篇 |
1968年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Minh Thac Nguyen Ryan Denniston Hien Thi Thu Nguyen Tuan Anh Hoang Hana Ross Anthony D. So 《PloS one》2014,9(1)
Illicit trade carries the potential to magnify existing tobacco-related health care costs through increased availability of untaxed and inexpensive cigarettes. What is known with respect to the magnitude of illicit trade for Vietnam is produced primarily by the industry, and methodologies are typically opaque. Independent assessment of the illicit cigarette trade in Vietnam is vital to tobacco control policy. This paper measures the magnitude of illicit cigarette trade for Vietnam between 1998 and 2010 using two methods, discrepancies between legitimate domestic cigarette sales and domestic tobacco consumption estimated from surveys, and trade discrepancies as recorded by Vietnam and trade partners. The results indicate that Vietnam likely experienced net smuggling in during the period studied. With the inclusion of adjustments for survey respondent under-reporting, inward illicit trade likely occurred in three of the four years for which surveys were available. Discrepancies in trade records indicate that the value of smuggled cigarettes into Vietnam ranges from $100 million to $300 million between 2000 and 2010 and that these cigarettes primarily originate in Singapore, Hong Kong, Macao, Malaysia, and Australia. Notable differences in trends over time exist between the two methods, but by comparison, the industry estimates consistently place the magnitude of illicit trade at the upper bounds of what this study shows. The unavailability of annual, survey-based estimates of consumption may obscure the true, annual trend over time. Second, as surveys changed over time, estimates relying on them may be inconsistent with one another. Finally, these two methods measure different components of illicit trade, specifically consumption of illicit cigarettes regardless of origin and smuggling of cigarettes into a particular market. However, absent a gold standard, comparisons of different approaches to illicit trade measurement serve efforts to refine and improve measurement approaches and estimates. 相似文献
2.
3.
Peng Wang Ronghua Luo Min Zhang Yaqing Wang Tianzhang Song Tingting Tao Zhongyu Li Lin Jin Hongyi Zheng Wenwen Chen Mengqian Zhao Yongtang Zheng Jianhua Qin 《Cell death & disease》2020,11(12)
COVID-19, caused by SARS-CoV-2, is an acute and rapidly developing pandemic, which leads to a global health crisis. SARS-CoV-2 primarily attacks human alveoli and causes severe lung infection and damage. To better understand the molecular basis of this disease, we sought to characterize the responses of alveolar epithelium and its adjacent microvascular endothelium to viral infection under a co-culture system. SARS-CoV-2 infection caused massive virus replication and dramatic organelles remodeling in alveolar epithelial cells, alone. While, viral infection affected endothelial cells in an indirect manner, which was mediated by infected alveolar epithelium. Proteomics analysis and TEM examinations showed viral infection caused global proteomic modulations and marked ultrastructural changes in both epithelial cells and endothelial cells under the co-culture system. In particular, viral infection elicited global protein changes and structural reorganizations across many sub-cellular compartments in epithelial cells. Among the affected organelles, mitochondrion seems to be a primary target organelle. Besides, according to EM and proteomic results, we identified Daurisoline, a potent autophagy inhibitor, could inhibit virus replication effectively in host cells. Collectively, our study revealed an unrecognized cross-talk between epithelium and endothelium, which contributed to alveolar–capillary injury during SARS-CoV-2 infection. These new findings will expand our understanding of COVID-19 and may also be helpful for targeted drug development.Subject terms: Mechanisms of disease, Viral infection 相似文献
4.
5.
High-resolution microscopy methods based on different nonlinear optical (NLO) contrast mechanisms are finding numerous applications in biology and medicine. While the basic implementations of these microscopy methods are relatively mature, an important direction of continuing technological innovation lies in improving the throughput of these systems. Throughput improvement is expected to be important for studying fast kinetic processes, for enabling clinical diagnosis and treatment, and for extending the field of image informatics. This review will provide an overview of the fundamental limitations on NLO microscopy throughput. We will further cover several important classes of high-throughput NLO microscope designs with discussions on their strengths and weaknesses and their key biomedical applications. Finally, this review will close with a perspective of potential future technological improvements in this field. 相似文献
6.
7.
8.
9.
10.