全文获取类型
收费全文 | 35992篇 |
免费 | 2141篇 |
国内免费 | 1822篇 |
出版年
2024年 | 48篇 |
2023年 | 279篇 |
2022年 | 743篇 |
2021年 | 1589篇 |
2020年 | 1014篇 |
2019年 | 1311篇 |
2018年 | 1481篇 |
2017年 | 1166篇 |
2016年 | 1774篇 |
2015年 | 2398篇 |
2014年 | 2575篇 |
2013年 | 3184篇 |
2012年 | 3016篇 |
2011年 | 2694篇 |
2010年 | 2050篇 |
2009年 | 1827篇 |
2008年 | 1894篇 |
2007年 | 1704篇 |
2006年 | 1508篇 |
2005年 | 1243篇 |
2004年 | 872篇 |
2003年 | 765篇 |
2002年 | 656篇 |
2001年 | 498篇 |
2000年 | 575篇 |
1999年 | 481篇 |
1998年 | 312篇 |
1997年 | 274篇 |
1996年 | 256篇 |
1995年 | 227篇 |
1994年 | 195篇 |
1993年 | 148篇 |
1992年 | 209篇 |
1991年 | 161篇 |
1990年 | 144篇 |
1989年 | 115篇 |
1988年 | 74篇 |
1987年 | 75篇 |
1986年 | 66篇 |
1985年 | 65篇 |
1984年 | 29篇 |
1983年 | 29篇 |
1982年 | 34篇 |
1981年 | 25篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 12篇 |
1971年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Steven I. Higgins Robert B. O’Hara Olga Bykova Michael D. Cramer Isabelle Chuine Eva‐Maria Gerstner Thomas Hickler Xavier Morin Michael R. Kearney Guy F. Midgley Simon Scheiter 《Journal of Biogeography》2012,39(12):2132-2145
Aim To develop a physiologically based model of the plant niche for use in species distribution modelling. Location Europe. Methods We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants. 相似文献
53.
54.
Sixin Jiang Brigitte Heller Vincent S. Tagliabracci Lanmin Zhai Jose M. Irimia Anna A. DePaoli-Roach Clark D. Wells Alexander V. Skurat Peter J. Roach 《The Journal of biological chemistry》2010,285(45):34960-34971
Stbd1 is a protein of previously unknown function that is most prevalent in liver and muscle, the major sites for storage of the energy reserve glycogen. The protein is predicted to contain a hydrophobic N terminus and a C-terminal CBM20 glycan binding domain. Here, we show that Stbd1 binds to glycogen in vitro and that endogenous Stbd1 locates to perinuclear compartments in cultured mouse FL83B or Rat1 cells. When overexpressed in COSM9 cells, Stbd1 concentrated at enlarged perinuclear structures, co-localized with glycogen, the late endosomal/lysosomal marker LAMP1 and the autophagy protein GABARAPL1. Mutant Stbd1 lacking the N-terminal hydrophobic segment had a diffuse distribution throughout the cell. Point mutations in the CBM20 domain did not change the perinuclear localization of Stbd1, but glycogen was no longer concentrated in this compartment. Stable overexpression of glycogen synthase in Rat1WT4 cells resulted in accumulation of glycogen as massive perinuclear deposits, where a large fraction of the detectable Stbd1 co-localized. Starvation of Rat1WT4 cells for glucose resulted in dissipation of the massive glycogen stores into numerous and much smaller glycogen deposits that retained Stbd1. In vitro, in cells, and in animal models, Stbd1 consistently tracked with glycogen. We conclude that Stbd1 is involved in glycogen metabolism by binding to glycogen and anchoring it to membranes, thereby affecting its cellular localization and its intracellular trafficking to lysosomes. 相似文献
55.
Jian‐Yong Guo Yong‐Sheng Wang Tian Chen Xiao‐Xu Jiang Ping Wu Tao Geng Zhong‐Hua Pan Meng‐Ke Shang Cheng‐Xiang Hou Kun Gao Xi‐Jie Guo 《Insect Science》2020,27(3):449-462
Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a major pathogen of the economic insect silkworm, Bombyx mori. Virus‐encoded microRNAs (miRNAs) have been proven to play important roles in host–pathogen interactions. In this study we identified a BmCPV‐derived miRNA‐like 21 nt small RNA, BmCPV‐miR‐1, from the small RNA deep sequencing of BmCPV‐infected silkworm larvae by stem‐loop quantitative real‐time PCR (qPCR) and investigated its functions with qPCR and lentiviral expression systems. Bombyx mori inhibitor of apoptosis protein (BmIAP) gene was predicted by both target prediction software miRanda and Targetscan to be one of its target genes with a binding site for BmCPV‐miR‐1 at the 5′ untranslated region. It was found that the expression of BmCPV‐miR‐1 and its target gene BmIAP were both up‐regulated in BmCPV‐infected larvae. At the same time, it was confirmed that BmCPV‐miR‐1 could up‐regulate the expression of BmIAP gene in HEK293T cells with lentiviral expression systems and in BmN cells by transfecting mimics. Furthermore, BmCPV‐miR‐1 mimics could up‐regulate the expression level of BmIAP gene in midgut and fat body in the silkworm. In the midgut of BmCPV‐infected larvae, BmCPV‐miR‐1 mimics could be further up‐regulated and inhibitors could lower the virus‐mediated expression of BmIAP gene. With the viral genomic RNA segments S1 and S10 as indicators, BmCPV‐miR‐1 mimics could up‐regulate and inhibitors down‐regulate their replication in the infected silkworm. These results implied that BmCPV‐miR‐1 could inhibit cell apoptosis in the infected silkworm through up‐regulating BmIAP expression, providing the virus with a better cell circumstance for its replication. 相似文献
56.
The effect of transcranial magnetic stimulation (TMS) of the right and the left frontotemporal areas on the short- and long-term verbal memory was studied in healthy subjects and patients with Parkinson’s disease. TMS with a magnetic induction of more than 1.2 T at 10 Hz was found to affect the short-term memory when applied to the left frontotemporal area and to have no significant effect on this type of memory when applied to the right frontotemporal area. In healthy subjects, TMS applied to the left or the right hemisphere did not affect the long-term memory. However, in patients with Parkinson’s disease, significant changes in the long-term memory were observed upon TMS of either the left or the right hemisphere. The effect was more evident on TMS of the right hemisphere.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 33–36.Original Russian Text Copyright © 2005 by Gimranov, Mal’tseva. 相似文献
57.
58.
59.
Q Yuan W M Jiang D Hollander E Leung J D Watson G W Krissansen 《Biochemical and biophysical research communications》1991,176(3):1443-1449
A cDNA clone encoding the N-terminal sequence of the murine integrin beta 7 subunit, a novel member of the leukocyte cell adhesion molecule subset (Leu-CAM), has been isolated. An N-terminal region of 13 contiguous amino acids deduced from the cDNA shows complete identity with the N-terminus of the 120 kDa subunit of the M290 antigen, a surface molecule found highly expressed on mouse intestinal intraepithelial lymphocytes (IEL). This unexpected result focuses two previously unconnected areas of research and suggests that integrins may have a special role to play in the defence of the gut mucosa. 相似文献
60.
G. V. Smirnova G. I. Vysochina N. G. Muzyka Z. Yu. Samoilova T. A. Kukushkina O. N. Oktyabr’ski 《Applied Biochemistry and Microbiology》2009,45(6):638-641
An antioxidant activity of the water-alcohol extracts of leaves of ten herbs from Western Siberia was studied. In vivo the
capability of extracts to protect cells of Escherichia coli against the bacteriostatic action of H 2O2 and the influence of the extracts on the expression of the antioxidant gene katG coding catalase-hydroperoxidase I were investigated. In vitro the radical-binding activity with DPhPG· (1,1-diphenyl-2-picrylhydrazyl radical), the chelating capability with ferrozine, and total composition of flavonoids and
tannins were determined. The extracts of Filipendula stepposa and Limonium gmelinii were characterized by the highest antioxidant activity. According to data, the test extracts could have an antioxidant effect
on bacteria in different ways at once including the direct inhibition of ROS (reactive oxygen species), iron ion chelation
and antioxidant gene induction. 相似文献