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961.
xCT, the core subunit of the system x(c)(-) high affinity cystine transporter, belongs to a superfamily of glycoprotein-associated amino acid transporters. Although xCT was shown to promote cystine transport in Xenopus oocytes, little work has been done with mammalian cells (Sato, H., Tamba, M., Ishii, T., and Bannai, S. J. Biol. Chem. 274, 11455-11458, 1999). Therefore, we have constructed mammalian expression vectors for murine xCT and its accessory subunit 4F2hc and transfected them into HEK293 cells. We report that this transporter binds cystine with high affinity (81 microM) and displays a pharmacological profile expected for system x(c)(-). Surprisingly, xCT transport activity in HEK293 cells is not dependent on the co-expression of the exogenous 4F2hc. Expression of GFP-tagged xCT indicated a highly clustered plasma membrane and intracellular distribution suggesting the presence of subcellular domains associated with combating oxidative stress. Our results indicate that HEK293 cells transfected with the xCT subunit would be a useful vehicle for future structure-function and pharmacology experiments involving system x(c)(-). 相似文献
962.
Al-awar RS Ray JE Hecker KA Joseph S Huang J Shih C Brooks HB Spencer CD Watkins SA Schultz RM Considine EL Faul MM Sullivan KA Kolis SP Carr MA Zhang F 《Bioorganic & medicinal chemistry letters》2004,14(15):3925-3928
The synthesis of novel aza-1,7-annulated indoles was achieved and these were converted to indolocarbazoles that proved to be potent kinase inhibitors. These compounds were also evaluated in a human colon carcinoma cell line and proved to be good antiproliferative agents. 相似文献
963.
Zhu G Conner SE Zhou X Chan HK Shih C Engler TA Al-Awar RS Brooks HB Watkins SA Spencer CD Schultz RM Dempsey JA Considine EL Patel BR Ogg CA Vasudevan V Lytle ML 《Bioorganic & medicinal chemistry letters》2004,14(12):3057-3061
The synthesis of a novel series of 1,7-annulated indolocarbazoles 2 and 16 is described. These compounds were found to be potent cyclin dependent kinase inhibitors with good antiproliferative activity against two human carcinoma cell lines. These inhibitors also arrested tumor cells at the G1 phase and inhibited pRb phosphorylation. 相似文献
964.
We designed a complementary metal oxide semiconductor (CMOS) chip with accompanied accessories as a system for the detections and quantifications of biochemical luminescence. This is the first of such instruments that has been reported. The semiconductor chip was manufactured through a 0.25 microm CMOS standard process. A current mirror was designed in integrated circuit (IC) to amplify the signal current that was induced by chemiluminescence. Horseradish peroxidase (HRP)-luminol-H2O2 system was used as an example to constitute a useful platform for coupling to chemiluminescence reactions which produce H2O2. Glucose-glucose oxidase (GOD) reaction was coupled with HRP-luminol-H2O2 reaction to demonstrate the ability of the novel CMOS base instrument for quantifying the biological luminescence of a variety of valuable clinical assays. Our results illustrated that the combination of the specifically designed CMOS IC and commercially available electronic devices established a simple and useful bioanalytical tool. 相似文献
965.
Huang SH Shih YC Wu CY Yuan CJ Yang YS Li YK Wu TK 《Biosensors & bioelectronics》2004,19(12):305-1633
An optical polymeric biochip system based on the complementary metal oxide semiconductor (CMOS) photo array sensor and polymeric enzyme biochip for rapidly quantitating uric acid in a one-step procedure was developed. The CMOS sensor was designed with N+/P-well structure and manufactured using a standard 0.5 μm CMOS process. The polymeric enzyme biochip was immobilized with uricase–peroxidase and used to fill the reacting medium with the sample. This study encompasses the cloning of the Bacillus subtilis uricase gene and expression in Escherichia coli, as well as the purification of uricase and measurement of its activity. The cloned uricase gene included an open reading frame of 1491 nucleotides that encodes a protein of approximately 55 kDa. The expression of the putative MBP-fusion protein involved approximately 98 kDa of the protein. The CMOS sensor response was stronger at a higher temperature range of 20–40 °C, with optimal pH at 8.5. The calibration curve of purified uric acid was linear in the concentration range from 2.5 to 12.5 mg/dL. The results obtained for serum uric acid correlated quite closely with those obtained using the Beckman Synchron method. 相似文献
966.
Differential hepatocyte toxicity of recombinant Apo2L/TRAIL versions 总被引:43,自引:0,他引:43
967.
Energetic contribution of non-essential 5' sequence to catalysis in a hepatitis delta virus ribozyme
Hepatitis delta virus (HDV) ribozymes employ multiple catalytic strategies to achieve overall rate enhancement of RNA cleavage. These strategies include general acid-base catalysis by a cytosine side chain and involvement of divalent metal ions. Here we used a trans-acting form of the antigenomic ribozyme to examine the contribution of the 5' sequence in the substrate to HDV ribozyme catalysis. The cleavage rate constants increased for substrates with 5' sequence alterations that reduced ground-state binding to the ribozyme. Quantitatively, a plot of activation free energy of chemical conversion versus Gibb's free energy of substrate binding revealed a linear relationship with a slope of -1. This relationship is consistent with a model in which components of the substrate immediately 5' to the cleavage site in the HDV ribozyme-substrate complex destabilize ground-state binding. The intrinsic binding energy derived from the ground-state destabilization could contribute up to 2 kcal/mol toward the total 8.5 kcal/mol reduction in activation free energy for RNA cleavage catalyzed by the HDV ribozyme. 相似文献
968.
Dey Chyi Sheu Po Jang Lio Shih Tse Chen Chi Tsai Lin Kow Jen Duan 《Biotechnology letters》2001,23(18):1499-1503
A mixed enzyme system, with -fructofuranosidase (obtained from Aspergillus japonicus) and commercial glucose oxidase (Gluzyme, Novo Nordisk), produced fructooligosaccharides (FOS) in high yield from sucrose. The reaction was performed in an aerated stirred tank reactor controlled at pH 5.5 by a slurry of CaCO3. Glucose, an inhibitor of -fructofuranosidase, produced in the reaction was converted by glucose oxidase to gluconic acid, which was then precipitated to calcium gluconate in solution. The system produced more than 90% (w/w) FOS on a dry weight basis, the remainder was glucose, sucrose and a small amount of calcium gluconate. Most of the FOS and sucrose was hydrolyzed to fructose in the mixed enzyme system with glucose oxidase and -fructofuranosidase from Asp. niger. 相似文献
969.
Niyogi KK Shih C Soon Chow W Pogson BJ Dellapenna D Björkman O 《Photosynthesis research》2001,67(1-2):139-145
When light absorption by a plant exceeds its capacity for light utilization, photosynthetic light harvesting is rapidly downregulated by photoprotective thermal dissipation, which is measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). To address the involvement of specific xanthophyll pigments in NPQ, we have analyzed mutants affecting xanthophyll metabolism in Arabidopsis thaliana. An npq1 lut2 double mutant was constructed, which lacks both zeaxanthin and lutein due to defects in the violaxanthin de-epoxidase and lycopene -cyclase genes. The npq1 lut2 strain had normal Photosystem II efficiency and nearly wild-type concentrations of functional Photosystem II reaction centers, but the rapidly reversible component of NPQ was completely inhibited. Despite the defects in xanthophyll composition and NPQ, the npq1 lut2 mutant exhibited a remarkable ability to tolerate high light.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
970.