全文获取类型
收费全文 | 1511篇 |
免费 | 100篇 |
国内免费 | 2篇 |
专业分类
1613篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 41篇 |
2021年 | 49篇 |
2020年 | 22篇 |
2019年 | 32篇 |
2018年 | 35篇 |
2017年 | 35篇 |
2016年 | 46篇 |
2015年 | 89篇 |
2014年 | 83篇 |
2013年 | 114篇 |
2012年 | 111篇 |
2011年 | 142篇 |
2010年 | 59篇 |
2009年 | 62篇 |
2008年 | 70篇 |
2007年 | 68篇 |
2006年 | 62篇 |
2005年 | 43篇 |
2004年 | 58篇 |
2003年 | 32篇 |
2002年 | 37篇 |
2001年 | 28篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有1613条查询结果,搜索用时 23 毫秒
931.
932.
933.
934.
肺是哺乳动物重要的呼吸器官,其发育的大部分过程发生于胚胎阶段,但由于研究手段的限制,对胎肺特别是后期胎肺发生机制的认识还十分有限.本文利用肾包膜下种植的方法建立了胎肺细胞肾包膜下种植模型.模型中上皮发育历经假腺体期、小管期和肺泡前体期等正常胎肺上皮组织发育的所有分化阶段,同时间充质形成广泛的毛细血管网络,与胎肺在子宫中的发育过程一致.更重要的是,消化处理后的单个胎肺细胞可有效地吸收反义寡核苷酸,并在种植组织中产生相应的表型效应.模型的建立为胎肺发生机制研究提供了一条新的途径. 相似文献
935.
Dang My Nhi Nguyen Tien Huy Kaname Ohyama Daisuke Kimura Nguyen Thi Phuong Lan Leo Uchida Nguyen Van Thuong Cao Thi My Nhon Le Hong Phuc Nguyen Thi Mai Shusaku Mizukami Lam Quoc Bao Nguyen Ngoc Doan Nguyen Van Thanh Binh Luong Chan Quang Juntra Karbwang Katsuyuki Yui Kouichi Morita Vu Thi Que Huong Kenji Hirayama 《PLoS neglected tropical diseases》2016,10(2)
Background
Severe dengue with severe plasma leakage (SD-SPL) is the most frequent of dengue severe form. Plasma biomarkers for early predictive diagnosis of SD-SPL are required in the primary clinics for the prevention of dengue death.Methodology
Among 63 confirmed dengue pediatric patients recruited, hospital based longitudinal study detected six SD-SPL and ten dengue with warning sign (DWS). To identify the specific proteins increased or decreased in the SD-SPL plasma obtained 6–48 hours before the shock compared with the DWS, the isobaric tags for relative and absolute quantification (iTRAQ) technology was performed using four patients each group. Validation was undertaken in 6 SD-SPL and 10 DWS patients.Principal findings
Nineteen plasma proteins exhibited significantly different relative concentrations (p<0.05), with five over-expressed and fourteen under-expressed in SD-SPL compared with DWS. The individual protein was classified to either blood coagulation, vascular regulation, cellular transport-related processes or immune response. The immunoblot quantification showed angiotensinogen and antithrombin III significantly increased in SD-SPL whole plasma of early stage compared with DWS subjects. Even using this small number of samples, antithrombin III predicted SD-SPL before shock occurrence with accuracy.Conclusion
Proteins identified here may serve as candidate predictive markers to diagnose SD-SPL for timely clinical management. Since the number of subjects are small, so further studies are needed to confirm all these biomarkers. 相似文献936.
Aphid flight activities in seed potato fields have been studied by the yellow water traps. It is a good method for monitoring aphids as vectors of viruses, but this study also showed it is a suitable method for insect-diversity research. During the four-year studies, over 11.500 specimens were collected and a total of 107 different taxa of aphids were identified. The most abundant species were polyphagous species, such as: Acyrthosiphon pisum (Haris), Aphis fabae Scopoli, Aphis gossypii Gloverand Brachycaudus helichrysi (Kaltenbach). The results of the studies show that diversity of aphids in different regions of Serbia is similar regardless of the altitude and the diversity of terrain. At most sites it ranged from 2 to 3. The highest value was recorded in Begeč, locality in northern part of Serbia, in year 2008, and it was 2.92. The maximum values of the Shannon-Weaver diversity index at all sites were recorded in the first weeks of the monitoring of aphid flight activities. Morisita-Horn similarity index shows no significant differences between sites regardless of altitudes. The sites are grouped by year, not by similarity of relief. In spite of these results, the Chi-square analysis showed highly significant difference in vector frequencies among seasons and sites with more pronounced differences for PVY. As a consequence of differences in vector frequencies, the vector pressure index in some regions was different also. The number of vectors and vector pressure index vary depending on the altitude of localities. At localities at altitudes under 1000 m, they were high. The highest index was at Kotraža, locality in central part of Serbia, in 2007, when PVY index exceeded the value of 180, while for PLRV it was 60. At high altitudes on mountain Golija, above 1100 m, the number of aphids was low, as well as the vector pressure index which indicates that these regions are suitable for producing virus-free seed potato. 相似文献
937.
938.
Vu Kim Chi Anton Van Rompaey Gerard Govers Veerle Vanacker Birgit Schmook Nguyen Hieu 《Human ecology: an interdisciplinary journal》2013,41(1):37-50
This paper discusses transitions in land use evidenced by the case of the Suoi Muoi catchment area in NW mountain of Vietnam. Land use transitions were detected from LANDSAT and SPOT satellite images taken over the last 40 years. The maps showing changes in land use were linked with biophysical properties of the land such as slope gradient, elevation and soil type, and cultural characteristic of various ethnic groups by means of logistic regression model. The combination of research methods and instruments from several disciplines, including statistical spatial analysis such as the multiple logistic regression (MLR) models and the multiple correspondence analysis (MCA) on household interview data, and key informant interviews allowed us to identify and validate a number of factors that drive land cover and land use changes in Northwest Vietnam. 相似文献
939.
940.
Summary. The analysis of plasma membranes from maize roots by native gel electrophoresis revealed the existence of Mn-containing 120
kDa and CuZn-containing 70, 40, and 15 kDa superoxide dismutase (SOD) isoform activities. Isoelectric focusing of the plasma
membranes differentiated anionic SOD isoforms with a pI of about 5 and cationic SOD isoforms at pI 8.6. Solubilization of
the plasma membrane proteins further separated the cationic SOD into pI 8.6, 8.2, 8.4, and 7.2 isoforms. Double staining for
both SOD and peroxidase activities showed an overlap of these activities only in the case of the high-molecular-mass (ca.
120 kDa) isoforms. High-temperature treatments demonstrated that the 120 kDa isoform was active even at 100 °C, indicating
that it was a germin-like protein with superoxide-dismutating activity, different from the peroxidase with a similar molecular
mass and the lower-molecular-mass CuZn-containing superoxide dismutases. These results are compared to those obtained from
whole-tissue extract and apoplastic fluid.
Correspondence and reprints: Maize Research Institute, POB 89-Zemun, 11081 Belgrade, Serbia and Montenegro. 相似文献