全文获取类型
收费全文 | 1160篇 |
免费 | 91篇 |
国内免费 | 1篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 37篇 |
2014年 | 36篇 |
2013年 | 68篇 |
2012年 | 74篇 |
2011年 | 88篇 |
2010年 | 53篇 |
2009年 | 56篇 |
2008年 | 77篇 |
2007年 | 88篇 |
2006年 | 98篇 |
2005年 | 61篇 |
2004年 | 83篇 |
2003年 | 55篇 |
2002年 | 50篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有1252条查询结果,搜索用时 156 毫秒
91.
Borjigin M Martinez B Purohit S de la Rosa G Arenaz P Stec B 《The FEBS journal》2010,277(22):4732-4740
Apurinic/apyrimidinic endonuclease (APE), an essential DNA repair enzyme, initiates the base excision repair pathway by creating a nick 5' to an abasic site in double-stranded DNA. Although the Chinese hamster ovary cells remain an important model for DNA repair studies, the Chinese hamster APE (chAPE1) has not been studied in vitro in respect to its kinetic characteristics. Here we report the results of a kinetic study performed on cloned and overexpressed enzyme in sf9 cells. The kinetic parameters were fully compatible with the broad range of kinetic parameters reported for the human enzyme. However, the activity measures depended on the time point of the culture. We applied inductivity coupled plasma spectrometry to measure the phosphorylation level of chAPE1. Our data showed that a higher phosphorylation of chAPE1 in the expression host was correlated to a lower endonuclease activity. The phosphorylation of a higher activity batch of chAPE1 by casein kinase II decreased the endonuclease activity, and the dephosphorylation of chAPE1 by lambda phosphatase increased the endonuclease activity. The exonuclease activity of chAPE1 was not observed in our kinetic analysis. The results suggest that noticeable divergence in reported activity levels for the human APE1 endonuclease might be caused by unaccounted phosphorylation. Our data also demonstrate that only selected kinases and phosphatases exert regulatory effects on chAPE1 endonuclease activity, suggesting further that this regulatory mechanism may function in vivo to turn on and off the function of this important enzyme in different organisms. 相似文献
92.
Agnieszka Jazwa Paulina Kucharzewska Justyna Leja Anna Zagorska Aleksandra Sierpniowska Jacek Stepniewski Magdalena Kozakowska Hevidar Taha Takahiro Ochiya Rafal Derlacz Elisa Vahakangas Seppo Yla-Herttuala Alicja Jozkowicz Jozef Dulak 《Genetic vaccines and therapy》2010,8(1):1-16
Background
Impaired wound healing in diabetes is related to decreased production of growth factors. Hence, gene therapy is considered as promising treatment modality. So far, efforts concentrated on single gene therapy with particular emphasis on vascular endothelial growth factor-A (VEGF-A). However, as multiple proteins are involved in this process it is rational to test new approaches. Therefore, the aim of this study was to investigate whether single AAV vector-mediated simultaneous transfer of VEGF-A and fibroblast growth factor 4 (FGF4) coding sequences will improve the wound healing over the effect of VEGF-A in diabetic (db/db) mice.Methods
Leptin receptor-deficient db/db mice were randomized to receive intradermal injections of PBS or AAVs carrying β-galactosidase gene (AAV-LacZ), VEGF-A (AAV-VEGF-A), FGF-4 (AAV-FGF4-IRES-GFP) or both therapeutic genes (AAV-FGF4-IRES-VEGF-A). Wound healing kinetics was analyzed until day 21 when all animals were sacrificed for biochemical and histological examination.Results
Complete wound closure in animals treated with AAV-VEGF-A was achieved earlier (day 19) than in control mice or animals injected with AAV harboring FGF4 (both on day 21). However, the fastest healing was observed in mice injected with bicistronic AAV-FGF4-IRES-VEGF-A vector (day 17). This was paralleled by significantly increased granulation tissue formation, vascularity and dermal matrix deposition. Mechanistically, as shown in vitro, FGF4 stimulated matrix metalloproteinase-9 (MMP-9) and VEGF receptor-1 expression in mouse dermal fibroblasts and when delivered in combination with VEGF-A, enhanced their migration.Conclusion
Combined gene transfer of VEGF-A and FGF4 can improve reparative processes in the wounded skin of diabetic mice better than single agent treatment. 相似文献93.
Jochen Schulze Sebastian Seitz Hiroaki Saito Michael Schneebauer Robert P. Marshall Anke Baranowsky Bjoern Busse Arndt F. Schilling Felix W. Friedrich Joachim Albers Alexander S. Spiro Jozef Zustin Thomas Streichert Kristina Ellwanger Christof Niehrs Michael Amling Roland Baron Thorsten Schinke 《PloS one》2010,5(4)
Wnt signalling is a key pathway controlling bone formation in mice and humans. One of the regulators of this pathway is Dkk1, which antagonizes Wnt signalling through the formation of a ternary complex with the transmembrane receptors Krm1/2 and Lrp5/6, thereby blocking the induction of Wnt signalling by the latter ones. Here we show that Kremen-2 (Krm2) is predominantly expressed in bone, and that its osteoblast-specific over-expression in transgenic mice (Col1a1-Krm2) results in severe osteoporosis. Histomorphometric analysis revealed that osteoblast maturation and bone formation are disturbed in Col1a1-Krm2 mice, whereas bone resorption is increased. In line with these findings, primary osteoblasts derived from Col1a1-Krm2 mice display a cell-autonomous differentiation defect, impaired canonical Wnt signalling and decreased production of the osteoclast inhibitory factor Opg. To determine whether the observed effects of Krm2 on bone remodeling are physiologically relevant, we analyzed the skeletal phenotype of 24 weeks old Krm2-deficient mice and observed high bone mass caused by a more than three-fold increase in bone formation. Taken together, these data identify Krm2 as a regulator of bone remodeling and raise the possibility that antagonizing KRM2 might prove beneficial in patients with bone loss disorders. 相似文献
94.
The effects of nitrogen deficiency on selected physiological attributes, phenylalanine ammonia-lyase (PAL, EC. 4.3.1.5) activity,
phenolic contents, peroxidase (EC. 1.11.1.7) and catalase (EC. 1.11.1.6) activities, lipid peroxidation status and H2O2 accumulation were studied in N-deficient Matricaria chamomilla (L.) over 12 days. N deficiency enhanced root growth and inhibited shoot growth. Chlorophyll composition and F
v/F
m were not affected by N stress, but nitrogen and soluble proteins decreased in both the rosettes and the roots. PAL activity,
expressed per mg protein, was enhanced in N-deficient rosettes and tended to decrease by the end of the experiment, while
in the roots PAL activity was maintained. Total phenolic contents increased in both rosettes and roots. Peroxidase and catalase
activities in N-deficient rosettes tended to decrease by the end of the experiment, while in the roots they increased on the
12th day of deficiency. Furthermore, lipid peroxidation status increased in N-deficient roots on the 12th day, indicating
that antioxidative protection was insufficient to scavenge reactive oxygen species being generated. Surprisingly, H2O2 content was even lower in N-deficient roots by the end of the experiment, while in the leaves increased. This observation
in correlation to lipid peroxidation and H2O2 degradation is discussed. The importance of PAL activity and phenolic metabolites in combination with antioxidative enzymes
for plant protection against oxidative stress and the significance of PAL activity for the mobilization of N availability
in N-deficient tissue are also discussed in view of existing information. 相似文献
95.
96.
97.
Ondrusova A Kalavsky E Rudinsky B Freybergh FP Bauer F Miklosko J Huttova M Kisac P Cauda R 《Neuro endocrinology letters》2007,28(Z2):20-21
Risk factors, therapy and outcome of 15 cases of nosocomial meningitis due to Pseudomonas aeruginosa is reviewed. No difference in risk factors was found, however mortality for Ps. aeruginosa was significantly higher (33.3 vs 15.1% p<0.04). 相似文献
98.
Rudinsky B Bauer F Kalavsky M Huttova M Sramka M Kalavsky E Benca J Karvaj M Jarcuska P Liskova A Kralinsky K Ondrusova A Taziarova M Pevalova L Kovac M Miklosko J 《Neuro endocrinology letters》2007,28(Z2):36-37
Meningitis after artificial implants in 60 children, mainly after foreign body infections (FBI) was caused more frequently by coagulase negative staphylococci and Ps. aeruginosa than other organisms and was significantly associated with perinatal trauma, hydrocephalus, haemorrhage or VLBW and had more neurologic sequels despite mortality was similar to other nosocomial meningitis. 相似文献
99.
Wang Y Stieglitz KA Bubunenko M Court DL Stec B Roberts MF 《The Journal of biological chemistry》2007,282(37):26989-26996
The Escherichia coli product of the suhB gene, SuhB, is an inositol monophosphatase (IMPase) that is best known as a suppressor of temperature-sensitive growth phenotypes in E. coli. To gain insights into these biological diverse effects, we determined the structure of the SuhB R184A mutant protein. The structure showed a dimer organization similar to other IMPases, but with an altered interface suggesting that the presence of Arg-184 in the wild-type protein could shift the monomer-dimer equilibrium toward monomer. In parallel, a gel shift assay showed that SuhB forms a tight complex with RNA polymerase (RNA pol) that inhibits the IMPase catalytic activity of SuhB. A variety of SuhB mutant proteins designed to stabilize the dimer interface did not show a clear correlation with the ability of a specific mutant protein to complement the DeltasuhB mutation when introduced extragenically despite being active IMPases. However, the loss of sensitivity to RNA pol binding, i.e. in G173V, R184I, and L96F/R184I, did correlate strongly with loss of complementation of DeltasuhB. Because residue 184 forms the core of the SuhB dimer, it is likely that the interaction with RNA polymerase requires monomeric SuhB. The exposure of specific residues facilitates the interaction of SuhB with RNA pol (or another target with a similar binding surface) and it is this heterodimer formation that is critical to the ability of SuhB to rescue temperature-sensitive phenotypes in E. coli. 相似文献
100.
BACKGROUND AND AIMS: The European Chaerophyllum temulum and two North American Chaerophyllum species have a trans-Atlantic disjunct distribution. This work aimed to resolve requirements for dormancy break and germination of C. temulum seeds and to compare dormancy traits with those of the two North American congeners. METHODS: Phenology of germination and embryo growth was studied by regularly exhuming seeds sown in natural conditions. Temperature requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Additionally the effect of GA(3) on germination was tested to determine the specific dormancy type. KEY RESULTS: In natural conditions, embryo growth starts in early winter. Seedlings emerge in late winter shortly after the embryos reached the critical ratio for embryo length to seed length (E : S) of approx. 0.95. Growth of the embryo only occurs during a prolonged incubation period at 5 degrees C. After stratification at 5 degrees C, which breaks physiological and morphological dormancy, seeds can germinate at a wide range of temperatures. GA(3) did not substitute for cold stratification in seeds placed at 23 degrees C. CONCLUSIONS: Chaerophyllum temulum has deep complex morphophysiological dormancy. This dormancy type differs considerably from that of the two North American congeners. 相似文献