全文获取类型
收费全文 | 94263篇 |
免费 | 9213篇 |
国内免费 | 4772篇 |
出版年
2023年 | 821篇 |
2022年 | 932篇 |
2021年 | 3410篇 |
2020年 | 2470篇 |
2019年 | 3018篇 |
2018年 | 3125篇 |
2017年 | 2260篇 |
2016年 | 3231篇 |
2015年 | 5005篇 |
2014年 | 5808篇 |
2013年 | 6574篇 |
2012年 | 7570篇 |
2011年 | 7162篇 |
2010年 | 4288篇 |
2009年 | 3842篇 |
2008年 | 4686篇 |
2007年 | 4216篇 |
2006年 | 3721篇 |
2005年 | 3186篇 |
2004年 | 2746篇 |
2003年 | 2432篇 |
2002年 | 2164篇 |
2001年 | 3618篇 |
2000年 | 3487篇 |
1999年 | 2785篇 |
1998年 | 1200篇 |
1997年 | 1192篇 |
1996年 | 1129篇 |
1995年 | 1065篇 |
1994年 | 936篇 |
1993年 | 737篇 |
1992年 | 1490篇 |
1991年 | 1215篇 |
1990年 | 1069篇 |
1989年 | 894篇 |
1988年 | 708篇 |
1987年 | 586篇 |
1986年 | 494篇 |
1985年 | 427篇 |
1984年 | 304篇 |
1983年 | 263篇 |
1982年 | 152篇 |
1981年 | 158篇 |
1980年 | 113篇 |
1979年 | 177篇 |
1978年 | 111篇 |
1977年 | 118篇 |
1976年 | 109篇 |
1975年 | 126篇 |
1974年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
91.
92.
D T Fei M C Gross J L Lofgren M Mora-Worms A B Chen 《Biochemical and biophysical research communications》1990,170(1):214-222
A specific and high throughput 96-well format bioassay for recombinant human relaxin (rhRLX) has been developed using human endometrial cells (NHE cells). rhRLX caused a time- and dose-dependent stimulation of cyclic AMP (cAMP) with 1/2 maximal activity of 3.56 +/- 0.65 ng/ml (n = 30). The range of the standard curve was 0.39 to 25 ng/ml with interplate precision of 17 and 22% CV for high and low controls respectively. The cAMP response requires forskolin and 3-isobutyl-1-methylxanthine, and is enhanced by prostaglandin E2 and F2 alpha. The NHE cells do not respond to A or B chains of rhRLX, or a whole array of hormones. Preincubation of rhRLX with specific monoclonal antibody completely abolished the cAMP response. This bioassay has been used to determine the biological activity of several manufactured lots of recombinant human relaxin. 相似文献
93.
Strong evidence suggests that cryoprotectant accumulation during pre-cold acclimation protects cells against freezing injuries caused by cellular dehydration. In this study, the concentrations of trehalose and glycerol were measured in Meloidogyne incognita and it was found that both cryoprotectants were significantly accumulated in second-stage juveniles (J2) of M. incognita after acclimation at 4°C. However, compared with non-acclimated samples, only a higher level of trehalose was induced in the egg masses of M. incognita in response to cold treatment. Further characterizations indicated that pre-cold acclimation efficiently accelerated the speed of larvae hatching from egg masses that were subjected to freezing at −1°C. In addition, the survival rate and pathogenicity of M. incognita J2 that had been acclimated prior to freezing were significantly enhanced when compared with non-acclimated J2 individuals. As far as we know, this is the first time that this phenomenon has been reported in M. incognita. 相似文献
94.
Timidity in dogs is a trait with high heritability. However, the relevant genetic factors and markers associated with this condition are largely unknown. The function of the catechol‐O‐methyl transferase (COMT) gene has been found to be associated with human fearful or anxious emotions, and the COMT:p.Val158Met polymorphism locus is significantly related to anxious behavior. In the present study, the correlation between timidity and four single nucleotide polymorphism (SNP) variations (C.‐1666C>G c.39A>G, c.216G>A, c.482G>A) of the COMT gene was investigated in dogs. The evaluation was based on the dog courage assessment assay and a genotype and haplotype analysis in Labrador Retrievers (LR) and Golden Retrievers (GR). The principal components analysis factor structure of the courage phenotype was invariant between LR and GR. Sex, breed and age had no statistically significant effect on the timidity of the dogs. All SNP loci detected were in Hardy–Weinberg equilibrium. The c.39A>G locus was removed in the subsequent association analysis due to the significant difference between LR and GR in genotype distributions. Intriguingly, the genotypes and haplotypes of the COMT gene were significantly and highly correlated with the timidity of LR and GR. The A alleles of the COMT:c.216G>A and c.482G>A loci appeared to play a dominant role in the timid behavior of the dogs. This result supports and broadens the warrior/worrier hypothesis and will have important implications for the understanding of the evolution of temperament in dogs. Additionally, the results provide predictive genetic markers for temperament in dogs. 相似文献
95.
Food Biophysics - Caffeic acid phenethyl ester (CAPE) has high cytotoxicity against various cancer cells but has low water solubility and poor bioavailability. The objective of this work was to... 相似文献
96.
Wu Changwei W. Tsai Pei-Jung Chen Sharon Chia-Ju Li Chia-Wei Hsu Ai-Ling Wu Hong-Yi Ko Yu-Ting Hung Pai-Chuan Chang Chun-Yen Lin Ching-Po Lane Timothy J. Chen Chia-Yuen 《Sleep and biological rhythms》2019,17(4):423-431
Sleep and Biological Rhythms - Neurovascular coupling (NVC), the transient regional hyperemia following the evoked neuronal responses, is the basis of blood oxygenation level-dependent techniques... 相似文献
97.
Journal of Molecular Modeling - The role of resultant gradient-information concept, reflecting the kinetic energy of electrons, in shaping the molecular electronic structure and reactivity... 相似文献
98.
99.
100.
The effect of glutathione (GSH) depletion by L-buthionine-[S,R]-sulphoximine (BSO) on tumor necrosis factor-alpha (TNF-alpha)-induced adhesion molecule expression and mononuclear leukocyte adhesion to human umbilical vein endothelial cells (HUVECs) was investigated. Cells with marked depletion of cytoplasmic GSH, but with an intact pool of mitochondrial GSH, only slightly enhanced TNF-alpha-induced E-selectin and vascular cell adhesion molecule-1 (VCAM-1) expression, compared with the control. However, TNF-a-induced expression of both molecules was markedly enhanced when the mitochondrial GSH pool was diminished to <15% of the control. In contrast, TNF-alpha-induced intercellular adhesion molecule-1 (ICAM-1) expression was not affected by the depletion of either cytoplasmic or mitochondrial GSH. Marked enhancement of TNF-alpha-induced adhesion molecule expression by the depletion of mitochondrial GSH resulted in increased in mononuclear leukocyte adhesion to treated HUVECs, compared with the control. These effects parallel reactive oxygen species (ROS) formation by the depletion of mitochondrial but not cytoplasmic GSH. Our findings demonstrate that depletion of mitochondrial GSH renders more ROS generation in HUVECs, and mitochondrial GSH modulates TNF-alpha-induced adhesion molecule expression and mononuclear leukocyte adhesion in HUVECs. 相似文献