全文获取类型
收费全文 | 2154篇 |
免费 | 252篇 |
出版年
2022年 | 26篇 |
2021年 | 45篇 |
2020年 | 22篇 |
2019年 | 42篇 |
2018年 | 44篇 |
2017年 | 44篇 |
2016年 | 57篇 |
2015年 | 106篇 |
2014年 | 107篇 |
2013年 | 119篇 |
2012年 | 142篇 |
2011年 | 153篇 |
2010年 | 86篇 |
2009年 | 95篇 |
2008年 | 114篇 |
2007年 | 98篇 |
2006年 | 81篇 |
2005年 | 78篇 |
2004年 | 82篇 |
2003年 | 73篇 |
2002年 | 68篇 |
2001年 | 70篇 |
2000年 | 55篇 |
1999年 | 59篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 34篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 38篇 |
1991年 | 18篇 |
1990年 | 35篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有2406条查询结果,搜索用时 42 毫秒
91.
92.
93.
The purpose of this study was to elucidate the role of NO and O-2 on enzymatic components of cyclooxygenase (COX) pathway in peritoneal macrophages. Activation of murine peritoneal macrophages by lipopolysaccharides (LPS) resulted in time-dependent production of nitric oxide (NO) and prostaglandin E2 (PGE2). This stimulation was also accompanied by the production of other reactive oxygen species such as superoxide (O-2), and by increased expression of COX-2. Our results provide evidence that O-2 may be involved in the pathways that result in arachidonate release and PGE2 formation by COX-2 in murine peritoneal macrophages stimulated by LPS. However, we were not able to demonstrate that NO participates in the regulation of PG production under our experimental conditions. 相似文献
94.
95.
96.
Multiple myeloma (MM) comprises 1% of all malignancies and 10% of all hematological malignancies. MM is a malignancy of plasma cells in the bone marrow where complex and dynamic interactions with the bone marrow microenvironment lead to tumor progression, skeletal destruction and angiogenesis. Despite the discovery of several novel treatments against MM, including the proteasome inhibitor bortezomib, it is considered to be an incurable disease with an average 4–5 years overall survival. 相似文献
97.
Cristina Besada Gerardo Sanchez Alejandra Salvador Antonio Granell 《Metabolomics : Official journal of the Metabolomic Society》2013,9(1):157-172
High resolution volatile profiling (67 compounds identified) of fruits from 12 persimmon cultivars was established and used to characterize the different astringency types of persimmon fruit before and after deastringency treatment. Analysis of the volatile profile of fruit enables us to differentiate between cultivars that at the moment of harvest produced non-astringent fruit (Pollination Constant Non Astringent—PCNA-type) from astringent ones (non-PCNA-type). Fruit failing to accumulate astringent compounds naturally (PCNA fruit) showed high levels of 3(2H)-benzofuranone, while this compound was not detected in any astringent type fruit (non-PCNA). In addition to this, PCNA cultivars also showed at harvest higher accumulation of benzeneacetaldehyde and lipid-derived aldehydes (hexanal, heptanal, octanal and decanal) than non-PCNA fruit. The application of postharvest deastringency treatment to all non-PCNA cultivars resulted on an important insolubilization of tannins. In general the CO2-treatment enhanced the levels of acetaldehyde, however those cultivars showing high levels of dihydrobenzofuran at harvest did not present an increment of acetaldehyde. In contrast, all non-PCNA cultivars exhibited an important accumulation of lipid-derived aldehydes due to CO2-treatment. Therefore, we propose that lipid-derived aldehydes (mainly decanal, octanal and heptanal) may be playing a role in the astringency loss. Our results suggest that 3(2H)-benzofuranone, benzeneacetaldehyde and lipid-derived aldehydes could be used as markers for both natural and artificial loss of astringency. 相似文献
98.
99.
Vera Jankowski Markus T?lle Thi Nguyet Anh Tran Markus van der Giet Mirjam Schuchardt Kerstin Lehmann Doreen Janke Burkhard Flick Alberto Arduan Ortiz Ni?o Maria Dolores Sanchez Martin Tepel Walter Zidek Joachim Jankowski 《PloS one》2013,8(7)
The secretion of angiogenic factors by vascular endothelial cells is one of the key mechanisms of angiogenesis. Here we report on the isolation of a new potent angiogenic factor, diuridine tetraphosphate (Up4U) from the secretome of human endothelial cells. The angiogenic effect of the endothelial secretome was partially reduced after incubation with alkaline phosphatase and abolished in the presence of suramin. In one fraction, purified to homogeneity by reversed phase and affinity chromatography, Up4U was identified by MALDI-LIFT-fragment-mass-spectrometry, enzymatic cleavage analysis and retention-time comparison. Beside a strong angiogenic effect on the yolk sac membrane and the developing rat embryo itself, Up4U increased the proliferation rate of endothelial cells and, in the presence of PDGF, of vascular smooth muscle cells. Up4U stimulated the migration rate of endothelial cells via P2Y2-receptors, increased the ability of endothelial cells to form capillary-like tubes and acts as a potent inducer of sprouting angiogenesis originating from gel-embedded EC spheroids. Endothelial cells released Up4U after stimulation with shear stress. Mean total plasma Up4U concentrations of healthy subjects (N = 6) were sufficient to induce angiogenic and proliferative effects (1.34±0.26 nmol L-1). In conclusion, Up4U is a novel strong human endothelium-derived angiogenic factor. 相似文献
100.
Sanchez Paulina Espinosa Magali Maldonado Vilma Barquera Rodrigo Belem-Gabiño Nayeli Torres Javier Cravioto Adrian Melendez-Zajgla Jorge 《Molecular biology reports》2020,47(7):5175-5184
Molecular Biology Reports - Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in humans, with less than 5% 5-year survival rate. PDAC is characterized by a small number of... 相似文献