全文获取类型
收费全文 | 6000篇 |
免费 | 556篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 62篇 |
2021年 | 98篇 |
2020年 | 83篇 |
2019年 | 111篇 |
2018年 | 171篇 |
2017年 | 143篇 |
2016年 | 224篇 |
2015年 | 305篇 |
2014年 | 385篇 |
2013年 | 395篇 |
2012年 | 578篇 |
2011年 | 470篇 |
2010年 | 336篇 |
2009年 | 288篇 |
2008年 | 407篇 |
2007年 | 401篇 |
2006年 | 375篇 |
2005年 | 286篇 |
2004年 | 283篇 |
2003年 | 262篇 |
2002年 | 176篇 |
2001年 | 104篇 |
2000年 | 87篇 |
1999年 | 63篇 |
1998年 | 44篇 |
1997年 | 35篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 23篇 |
1993年 | 8篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 25篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1965年 | 4篇 |
排序方式: 共有6558条查询结果,搜索用时 15 毫秒
991.
T. Suteevun-Phermthai C.L. Curchoe A.C. Evans E. Boland D. Rizos T. Fair P. Duffy L.Y. Sung F. Du S. Chaubal J. Xu T. Wechayant X. Yang P. Lonergan R. Parnpai X.C. Tian 《Animal reproduction science》2009,116(1-2):19-27
Cloned animals often suffer from loss of development to term and abnormalities, typically classified under the umbrella term of Large Offspring Syndrome (LOS). Cattle are an interesting species to study because of the relatively greater success rate of nuclear transfer in this species compared with all species cloned to date. The imprinted insulin-like growth factor receptor (IGF2R; mannose-6-phosphate) gene was chosen to investigate aspects of fetal growth and development in cloned cattle in the present study. IGF2R gene expression patterns in identical genetic clones of several age groups were assessed in day 25, day 45, and day 75 fetuses as well as spontaneously aborted fetuses, calves that died shortly after birth and healthy cloned calves using single stranded conformational polymorphism gel electrophoresis. A variable pattern of IGF2R allelic expression in major organs such as the brain, cotyledon, heart, liver, lung, spleen, kidney and intercotyledon was observed using a G/A transition in the 3’UTR of IGF2R. IGF2R gene expression was also assessed by real time RT-PCR and found to be highly variable among the clone groups. Proper IGF2R gene expression is necessary for survival to term, but is most likely not a cause of early fetal lethality or an indicator of postnatal fitness. Contrary to previous reports of the transmission of imprinting patterns from somatic donor cells to cloned animals within organs in the same cloned animal the paternal allele of IGF2R can be imprinted in one tissue while the maternal allele is imprinted in another tissue. This observation has never been reported in any species in which imprinting has been studied. 相似文献
992.
Ramesh P. Thylur Young‐Dae Kim Min‐Sung Kwon Hyun‐Mee Oh Ho‐Keun Kwon Sang‐Hyun Kim Sin‐Hyeog Im Jang‐Soo Chun Zee‐Yong Park Chang‐Duk Jun 《Journal of cellular biochemistry》2009,108(3):705-715
Swiprosin‐1 exhibits the highest expression in CD8+ T cells and immature B cells and has been thought to play a role in lymphocyte physiology. Here we report that swiprosin‐1 is also expressed in mast cells and up‐regulated in both in vitro cultured mast cells by phorbol ester and in vivo model tissues of passive cutaneous anaphylaxis and atopic dermatitis. Targeted inhibition of the specific protein kinase C (PKC) isotypes by siRNA revealed that PKC‐βI/η are involved in the expression of swiprosin‐1 in the human mast cell line HMC‐1. In contrast, down‐regulation of swiprosin‐1 by A23187 or ionomycin suggests that calcium‐signaling plays a negative role. The ectopic expression of swiprosin‐1 augmented PMA/A23187‐induced NF‐κB promoter activity, and resulted in increased expression of cytokines. Moreover, knock‐down of swiprosin‐1 attenuated PMA/A23187‐induced cytokine expression. Collectively, these results suggest that swiprosin‐1 is a PKC‐βI/η‐inducible gene and it modulates mast cell activation through NF‐κB‐dependent pathway. J. Cell. Biochem. 108: 705–715, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
993.
Makoto Fujii Kye Sook Yi Myung Jong Kim Sang Hoon Ha Sung Ho Ryu Pann‐Ghill Suh Hitoshi Yagisawa 《Journal of cellular biochemistry》2009,108(3):638-650
Phosphorylation of phospholipase C‐δ1 (PLC‐δ1) in vitro and in vivo was investigated. Of the serine/threonine kinases tested, protein kinase C (PKC) phosphorylated the serine residue(s) of bacterially expressed PLC‐δ1 most potently. It was also demonstrated that PLC‐δ1 directly bound PKC‐α via its pleckstrin homology (PH) domain. Using deletion mutants of PLC‐δ1 and synthetic peptides, Ser35 in the PH domain was defined as the PKC mediated in vitro phosphorylation site of PLC‐δ1. In vitro phosphorylation of PLC‐δ1 by PKC stimulated [3H]PtdIns(4,5)P2 hydrolyzing activity and [3H]Ins(1,4,5)P3‐binding of the PLC‐δ1. On the other hand, endogenous PLC‐δ1 was constitutively phosphorylated and phosphoamino acid analysis revealed that major phosphorylation sites were threonine residues in quiescent cells. The phosphorylation level and the species of phosphoamino acid were not changed by various stimuli such as PMA, EGF, NGF, and forskolin. Using matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, we determined that Thr209 of PLC‐δ1 is one of the constitutively phosphorylated sites in quiescent cells. The PLC activity was potentiated when constitutively phosphorylated PLC‐δ1 was dephosphorylated by endogenous phosphatase(s) in vitro. Additionally, coexpression with PKC‐α reduced serine phosphorylation of PLC‐δ1 detected by an anti‐phosphoserine antibody and PLC‐δ1‐dependent basal production of inositol phosphates in NIH‐3T3 cells, suggesting PKC‐α activates phosphatase or inactivates another kinase involved in PLC‐δ1 serine phosphorylation to modulate the PLC‐δ1 activity in vivo. Taken together, these results suggest that PLC‐δ1 has multiple phosphorylation sites and phosphorylation status of PLC‐δ1 regulates its activity positively or negatively depends on the phosphorylation sites. J. Cell. Biochem. 108: 638–650, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
994.
995.
In vitro pharmacogenomic database and chemosensitivity predictive genes in gastric cancer 总被引:1,自引:0,他引:1
Gastric cancer is one of the most common cancers worldwide, and there are clinical caveats in predicting tumor response to chemotherapy. This study describes the construction of an in vitro pharmacogenomic database, and the selection of genes associated with chemosensitivity in gastric cancer cell lines. Gene expression and chemosensitivity databases were integrated using the Pearson correlation coefficient to give the GC-matrix. The 85 genes were selected that were commonly associated with chemosensitivity of the major anticancer drugs. We then focused on the genes that were highly correlated with each specific drug. Classification of cell lines based on the set of genes associated with each drug was consistent with the division into resistant or sensitive groups according to the chemosensitivity results. The GC-matrix of the gastric cancer cell line database was used to identify different sets of chemosensitivity-related genes for specific drugs or multiple drugs. 相似文献
996.
Polyploidy, which is thought to have played an important role in plant evolution and speciation, is prevalent in Chrysanthemum (x = 9). In fact, polyploid series are known in C. zawadskii (2x, 4x, 6x, 8x, and 10x) and C. indicum (2x, 4x, and 6x), but the mechanism by which polyploidization occurs is unknown. Here we show that in diploid individuals of both C. zawadskii and C. indicum, the fusion between two adjacent pollen mother cells (PMCs) occurs at a frequency of 1.1–1.3% early in the first meiotic
division. While possessing the chromosomes of both PMCs, the fused cell or syncyte undertakes subsequent meiotic division
processes as a single large PMC, producing four 2n pollen grains that are able to germinate. Despite their low frequency, syncyte formation may have played a major role in
the production of infraspecific polyploids in Chrysanthemum. 相似文献
997.
Juan Mao Sung Wook Won Yeoung-Sang Yun 《World journal of microbiology & biotechnology》2009,25(7):1259-1266
A low cost biosorbent, Corynebacterium glutamicum, was studied for the sorption of Reactive Red 4 (RR 4) and Methylene Blue (MB). The equilibrium isotherm data were well described
by the Langmuir model. pH edge experiments showed that pH of the solution was an important controlling parameter in the sorption
process. In the case of RR 4, with increases in the pH from 2 to 10, the uptake decreased from 52 to 1 mg/g; conversely, the
uptake of MB increased and the maximum MB uptake was obtained at pH ≥ 9. An increase in the salt concentration strongly influenced
the uptake of MB, but had no effect on that of RR 4. In order to identify the binding sites for the dye molecules, the biosorbent
was potentiometrically titrated, the results of which showed the presents of four major functional group types on the biomass
surface, which were confirmed by FTIR analysis. It was found that positively charged amine groups (Biomass-NH3
+) were the likely binding sites for anionic RR 4, and negatively charged carboxyl (Biomass-COO−) and phosphate groups (Biomass-HPO4
−) played a role in the electrostatic attraction of cationic MB. 相似文献
998.
999.
Young Mo Kim Donghee Park Dae Sung Lee Kyung A Jung Jong Moon Park 《Bioresource technology》2009,100(19):4340-4347
A full-scale pre-denitrification process treating cokes wastewater containing toxic compounds such as phenols, cyanides and thiocyanate has shown good performance in carbon and nitrogen removal. However, field operators have been having trouble with its instability without being able to identify the causes. To clarify the main cause of these sudden failures of the process, comprehensive studies were conducted on the pre-denitrification process using a lab-scale reactor system with real cokes wastewater. First, the shock loading effects of three major pollutants were investigated individually. As the loading amount of phenol increased to 600 mg/L, more COD, TOC and phenol itself were flowed into the aerobic reactor, but phenol itself did not inhibit nitrification and denitrification, owing to the effect of dilution and its rapid biodegradation. Higher loading of ammonia or thiocyanate slightly enhanced the removal efficiency of organic matter, but caused the final discharge concentration of total nitrogen to be above its legal limit of 60 mg-N/L. Meanwhile, continuous inflow of abnormal wastewater collected during unstable operation of the full-scale pre-denitrification process, caused a sudden failure of nitrogen removal in the lab-scale process, like the removal pattern of the full-scale one. This was discovered to be due to the lack of inorganic carbon in the aerobic reactor where autotrophic nitrification occurs. 相似文献
1000.
Sunkyung Lee Kyu Yang Yi Sung Jun Youn Byung Ho Lee Sung-eun Yoo 《Bioorganic & medicinal chemistry letters》2009,19(5):1329-1331
A series of (2-aryl-5-methylimidazol-4-ylcarbonyl)guanidines and (2-aryl-5-methyloxazol-4-ylcarbonyl)guanidines were synthesized and evaluated as NHE-1 inhibitors. The structure–activity relationships well matched those of furan derivatives, which were previously investigated. The (2,5-disubstituted)phenyl compounds showed better activities than the other analogues in both imidazole and oxazole compounds. Especially, 2-(2,5-dichlorophenyl)imidazole 52, and 2-(2-methoxy-5-chlorophenyl)imidazole 54 compounds exhibited potent cardioprotective efficacy both in vitro and in vivo as well as high NHE-1 inhibitory activities. 相似文献