全文获取类型
收费全文 | 5747篇 |
免费 | 512篇 |
国内免费 | 205篇 |
专业分类
6464篇 |
出版年
2024年 | 25篇 |
2023年 | 202篇 |
2022年 | 255篇 |
2021年 | 358篇 |
2020年 | 346篇 |
2019年 | 511篇 |
2018年 | 348篇 |
2017年 | 227篇 |
2016年 | 218篇 |
2015年 | 279篇 |
2014年 | 384篇 |
2013年 | 502篇 |
2012年 | 285篇 |
2011年 | 292篇 |
2010年 | 201篇 |
2009年 | 189篇 |
2008年 | 198篇 |
2007年 | 226篇 |
2006年 | 188篇 |
2005年 | 188篇 |
2004年 | 113篇 |
2003年 | 116篇 |
2002年 | 144篇 |
2001年 | 97篇 |
2000年 | 89篇 |
1999年 | 63篇 |
1998年 | 55篇 |
1997年 | 51篇 |
1996年 | 34篇 |
1995年 | 31篇 |
1994年 | 30篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有6464条查询结果,搜索用时 0 毫秒
51.
Rika Kamei Mana Miyakoda Takahiko Tamura Daisuke Kimura Kiri Honma Kazumi Kimura Katsuyuki Yui 《Microbiology and immunology》2013,57(3):213-223
52.
Ryohei Yamaoka Hiroshi Fukami Shoziro Ishii 《Bioscience, biotechnology, and biochemistry》2013,77(10):1971-1977
The sex pheromone produced by adult females of the potato tuberworm moth was isolated from unmated female moths reared in the laboratory. The gas Chromatographic and mass spectrometric data suggested the pheromone to be a tridecatrienyl acetate. The isolated pheromone was subjected to partial hydrogenation with hydrazine and hydrogen peroxide and subsequent ozonolysis to produce a mixture of ω-acetoxy-alkanals. They were identified by mass Chromatographic technique as 4-acetoxy-butanal, 7-acetoxy-heptanal, and 10-acetoxy-decanal respectively. Consequently, the pheromone was identified as 4,7,10-tridecatrienyl acetate except the geometric configuration. 相似文献
53.
Nikola Hadzi‐Petrushev Marija Angelovski Katerina Rebok Vadim Mitrokhin Andre Kamkin Mitko Mladenov 《Journal of biochemical and molecular toxicology》2019,33(8)
For 22 days after monocrotaline injection two groups of rats received either of the monocarbonyl curcumin analogs (2E,6E)‐2,6‐bis(2‐bromobenzylidene)cycloxehanone (B2BrBC) and (2E,6E)‐2,6‐bis([2‐tri?uoromethyl]benzylidene)cyclohexanone (C66), and their right ventricle parameters were compared to those from the control and the monocrotaline injected animals. B2BrBC and C66 treatments did not prevent the monocrotaline‐induced right ventricular hypertrophy but attenuated the changes in antioxidant enzyme activities and reduced inflammation. The level of thiol‐based nonenzymatic antioxidants did not change in the function of monocrotaline or curcumin analogs treatment. However, due to its stronger antioxidant properties, only B2BrBC treatment was effective in the reduction of monocrotaline‐associated lipid peroxidation. The obtained results suggest that increasing the levels of antioxidant enzymes may not be sufficient to reduce oxidative stress and chronic inflammation optimally and our current study supports the potential of compounds with more than one beneficial biological activity as a promising treatment against the progression of cardiac hypertrophy. 相似文献
54.
55.
This study examines age‐dependent metabolic‐inflammatory axis in primary astrocytes isolated from brain cortices of 7‐, 13‐, and 18‐month‐old Sprague–Dawley male rats. Astrocytes showed an age‐dependent increase in mitochondrial oxidative metabolism respiring on glucose and/or pyruvate substrates; this increase in mitochondrial oxidative metabolism was accompanied by increases in COX3/18SrDNA values, thus suggesting an enhanced mitochondrial biogenesis. Enhanced mitochondrial respiration in astrocytes limits the substrate supply from astrocytes to neurons; this may be viewed as an adaptive mechanism to altered cellular inflammatory–redox environment with age. These metabolic changes were associated with an age‐dependent increase in hydrogen peroxide generation (largely ascribed to an enhanced expression of NOX2) and NFκB signaling in the cytosol as well as its translocation to the nucleus. Astrocytes also displayed augmented responses with age to inflammatory cytokines, IL‐1β, and TNFα. Activation of NFκB signaling resulted in increased expression of nitric oxide synthase 2 (inducible nitric oxide synthase), leading to elevated nitric oxide production. IL‐1β and TNFα treatment stimulated mitochondrial oxidative metabolism and mitochondrial biogenesis in astrocytes. It may be surmised that increased mitochondrial aerobic metabolism and inflammatory responses are interconnected and support the functionality switch of astrocytes, from neurotrophic to neurotoxic with age. 相似文献
56.
Bone morphogenetic protein-4 enhances vascular endothelial growth factor secretion by human retinal pigment epithelial cells 总被引:1,自引:0,他引:1
Vogt RR Unda R Yeh LC Vidro EK Lee JC Tsin AT 《Journal of cellular biochemistry》2006,98(5):1196-1202
Retinal pigment epithelial (RPE) cells secrete vascular endothelial growth factor (VEGF), a cytokine known to promote angiogenesis. Results from RNase protection assays (RPAs) show that RPE from non-diabetic human donors and from adult retinal pigment epithelium-19 (ARPE-19) cells expressed significant bone morphogenetic protein-4 (BMP-4) message. In addition, ARPE-19 cells cultured in high glucose (25 mM), compared to those in physiological glucose (5.5 mM) released significantly more BMP-4 into the conditioned media (CM). However, the effect of BMP-4 on the release of VEGF by ARPE-19 cells has not been studied. Accordingly, ARPE-19 cells were treated with BMP-4 to determine VEGF secretion. BMP-4 and VEGF levels in the CM and cell lysates were measured by enzyme-linked immunosorbent assay (ELISA). Cells treated with exogenous BMP-4 had higher VEGF in the CM and this treatment effect was dose- and time-dependent, while cell lysates had low levels of VEGF. Addition of cycloheximide (CHX) or actinomycin-D (ACT) significantly reduced VEGF secretion from cells treated with BMP-4, suggesting that the BMP-4-induced secretion of VEGF requires new RNA and protein synthesis. Our results suggest that BMP-4 may play a role in the regulation of ocular angiogenesis associated with diabetic retinopathy (DR) by stimulating VEGF release from RPE cells. 相似文献
57.
58.
Kenji Miyazawa Fang He Kazutoyo Yoda Masaru Hiramatsu 《Microbiology and immunology》2012,56(12):847-854
The murine macrophage‐like cell line J774.1 was treated with heat‐killed cells of Lactobacillus GG (LGG) and L. gasseri TMC0356 (TMC 0356). Interleukin (IL)‐6, IL‐12, and tumor necrosis factor‐α were profiled from the J774.1 cells using enzyme‐linked immunosorbent assay methods. The conditioned medium from cultured J774.1 cells was transferred to the preadipocyte cell line 3T3‐L1 (which is a mouse embryonic fibroblast‐adipose‐like cell line). Growth and differentiation of 3T3‐L1 cells were monitored by analyzing lipid accumulation and expression of peroxisome proliferator‐activated receptor (PPAR)‐γ mRNA. The medium conditioned by 3T3‐L1 cells was added to J774.1 cells and the cytokines in the supernatant analyzed. Compared with that of cells exposed to a PBS‐conditioned medium, lipid accumulation in 3T3‐L1 cells was significantly suppressed in a dose‐dependent manner by each medium that had been conditioned with LGG and TMC0356. PPAR‐γ mRNA expression in 3T3‐L1 cells was also significantly downregulated (P < 0.01, P < 0.05, respectively). The conditioned medium of 3T3‐L1 adipose phenotype significantly stimulated production of IL‐6 and IL‐12 in J774.1 cells treated with LGG and TMC0356. These results suggest that lactobacilli may suppress differentiation of preadipocytes through macrophage activation and alter the immune responses of macrophages to adipose cells. 相似文献
59.
60.
Yahya Elsayed Constantina Lekakou Paul Tomlins 《Biotechnology and bioengineering》2019,116(6):1509-1522
The paper presents a transient, continuum, two-phase model of the tissue engineering in fibrous scaffolds, including transport equations for the flowing culture medium, nutrient and cell concentration with transverse and in-plane diffusion and cell migration, a novel feature of local in-plane transport across a phenomenological pore and innovative layer-by-layer cell filling approach. The model is successfully validated for the smooth muscle cell tissue engineering of a vascular graft using crosslinked, electrospun gelatin fiber scaffolds for both static and dynamic cell culture, the latter in a dynamic bioreactor with a rotating shaft on which the tubular scaffold is attached. Parametric studies evaluate the impact of the scaffold microstructure, cell dynamics, oxygen transport, and static or dynamic conditions on the rate and extent of cell proliferation and depth of oxygen accessibility. An optimized scaffold of 75% dry porosity is proposed that can be tissue engineered into a viable and still fully oxygenated graft of the tunica media of the coronary artery within 2 days in the dynamic bioreactor. Such scaffold also matches the mechanical properties of the tunica media of the human coronary artery and the suture retention strength of a saphenous vein, often used as a coronary artery graft. 相似文献