全文获取类型
收费全文 | 13199篇 |
免费 | 1129篇 |
国内免费 | 1篇 |
专业分类
14329篇 |
出版年
2023年 | 75篇 |
2022年 | 158篇 |
2021年 | 277篇 |
2020年 | 210篇 |
2019年 | 280篇 |
2018年 | 331篇 |
2017年 | 306篇 |
2016年 | 473篇 |
2015年 | 675篇 |
2014年 | 693篇 |
2013年 | 866篇 |
2012年 | 941篇 |
2011年 | 894篇 |
2010年 | 651篇 |
2009年 | 599篇 |
2008年 | 700篇 |
2007年 | 694篇 |
2006年 | 686篇 |
2005年 | 610篇 |
2004年 | 596篇 |
2003年 | 499篇 |
2002年 | 484篇 |
2001年 | 225篇 |
2000年 | 230篇 |
1999年 | 202篇 |
1998年 | 156篇 |
1997年 | 132篇 |
1996年 | 101篇 |
1995年 | 94篇 |
1994年 | 79篇 |
1993年 | 94篇 |
1992年 | 118篇 |
1991年 | 116篇 |
1990年 | 113篇 |
1989年 | 88篇 |
1988年 | 81篇 |
1987年 | 82篇 |
1986年 | 63篇 |
1985年 | 75篇 |
1984年 | 70篇 |
1983年 | 49篇 |
1982年 | 51篇 |
1981年 | 41篇 |
1980年 | 32篇 |
1979年 | 35篇 |
1978年 | 27篇 |
1977年 | 39篇 |
1975年 | 33篇 |
1974年 | 26篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Cristian A. Acevedo Elizabeth Y. Sanchez Juan G. Reyes Manuel E. Young 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(3-4):449-455
It is known that skin releases volatile organic compounds to the environment, and also that its emission pattern changes with aging of the skin. It could be considered, that these compounds are intermediaries in cell metabolism, since many intermediaries of metabolic pathways have a volatile potential. In this work, a simple and non-destructive method consisting of SPME sampling and GC/MS analysis was developed to identify volatile organic emanations from cell cultures. This technique, applied to skin cells culture, indicates that the cells or cell metabolism produce several skin emissions. Chemometric analysis was performed in order to explore the relationship between a volatile profile and the senescence of cell cultures. Volatile profiles were different for cell cultures in different degrees of senescence, indicating that volatile compound patterns could be used to provide information about the age of skin cells. 相似文献
2.
Sacramento Doralice Rodrigues Coelho Rosalie Reed Rodrigues Wigg Márcia Dutra Toledo Luna Linhares Luiz Fernando de Matos dos Santos Marta Gonçalves Azevedo Soares Semêdo Luzia Teixeira de Ribeiro da Silva Antonio Jorge 《World journal of microbiology & biotechnology》2004,20(3):225-229
A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial
activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions,
obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic
fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type
1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
4.
5.
Amiloride fluxes across erythrocyte membranes 总被引:3,自引:0,他引:3
Amiloride is known to inhibit both the influx of Na+ and the activation of mitogenesis in many cultured cell lines. This paper describes experiments in which the permeability coefficient of amiloride was determined from measurements of tracer fluxes across human erythrocytes and resealed ghosts. From an analysis of these fluxes, a permeability coefficient of 10(-7) cm/s for the uncharged form of amiloride was deduced. Based upon this measured permeability value, we present calculations of intracellular accumulation times of amiloride in cells of differing surface-to-volume ratio. 相似文献
6.
M del Mar Medina-Puerta A Garrido-Pertierra 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,83(1):215-220
The enzyme 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.44) from bass liver has been purified to over 95% of homogeneity by gel filtration, affinity and ion exchange chromatographies. The apparent molecular weight was estimated by gel filtration chromatography to about 100,000. Analysis of the enzyme on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed to be a dimeric protein. The effect of pH and kinetic properties were studied. 相似文献
7.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
8.
9.
Kinga Michno David Knight Jorge M. Campussano Diana van de Hoef Gabrielle L. Boulianne 《PloS one》2009,4(9)
Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation. 相似文献
10.
Presented a choice between conspecific males and 2 congeneric males, virgin females ofMelittobia australica andM. digitata chose conspecific males disproportionately more often, whereasM. femorata females distributed themselves evenly among the choices. Empty tubes, provided as the fourth choice in the test apparatus,
were entered much less often than tubes containing live males. Females of all species chose “wrong” males about equally frequently.
These observations suggest that even non-conspecific males possess some degree of attractiveness to virgin females. Chemicals
in the sex pheromone of the males are presumed to be the source of the males' attractancy. The incomplete species specificity
is interpreted in light of the life history of this genus, and it is suggested that specific recognition cues operate primarily
after the sexes come together.
Supported by a grant from Kagoshima Prefecture in Japan under the exchange program of faculty members between Kagoshima University
and the University of Georgia. 相似文献