全文获取类型
收费全文 | 974篇 |
免费 | 56篇 |
国内免费 | 3篇 |
出版年
2023年 | 6篇 |
2022年 | 31篇 |
2021年 | 44篇 |
2020年 | 31篇 |
2019年 | 31篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 39篇 |
2015年 | 64篇 |
2014年 | 60篇 |
2013年 | 60篇 |
2012年 | 93篇 |
2011年 | 76篇 |
2010年 | 43篇 |
2009年 | 29篇 |
2008年 | 46篇 |
2007年 | 29篇 |
2006年 | 42篇 |
2005年 | 21篇 |
2004年 | 31篇 |
2003年 | 23篇 |
2002年 | 28篇 |
2001年 | 24篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1967年 | 1篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有1033条查询结果,搜索用时 328 毫秒
101.
Hossain MB 《Journal of biosocial science》2005,37(5):529-554
With a population of over 131 million and a fertility rate of 29.9 per 1000, population growth constitutes a primary threat to continued economic growth and development in Bangladesh. One strategy that has been used to cease further increases in fertility in Bangladesh involves using family planning outreach workers who travel throughout rural and urban areas educating women regarding contraceptive alternatives. This study uses a longitudinal database to assess the impact of family planning outreach workers' contact upon contraceptive switching and upon the risk of an unintended pregnancy. Using longitudinal data on contraceptive use from the Operations Research Project (ORP) of the International Centre for Diarrhoeal Disease Research (ICDDR,B) in Bangladesh, multiple decrement life table analysis and multilevel, discrete-time competing risk hazards models were used to estimate the cumulative probabilities of switching to an alternative form of contraceptive use after a woman engaged in a discussion with an outreach worker. After controlling for the effects of socio-demographic and economic characteristics, the analysis revealed that family planning outreach workers' contact with women significantly decreases the risk of transitioning to the non-use of contraceptives. This contact also reduces the risk of an unintended pregnancy. Family planning workers' contact with women is associated with the increased risk of a woman switching from one modern method to another modern method. The study results indicate that side-effects and other method-related reasons are the two primary reasons for contraceptive discontinuation in rural Bangladesh. 相似文献
102.
Khan FH Sen T Maiti AK Jana S Chatterjee U Chakrabarti S 《Biochimica et biophysica acta》2005,1741(1-2):65-74
Several studies on mitochondrial functions following brief exposure (5-15 min) to dopamine (DA) in vitro have produced extremely variable results. In contrast, this study demonstrates that a prolonged exposure (up to 2 h) of disrupted or lysed mitochondria to DA (0.1-0.4 mM) causes a remarkable and dose-dependent inhibition of complex I and complex IV activities. The inhibition of complex I and complex IV activities is not prevented by the antioxidant enzyme catalase (0.05 mg/ml) or the metal-chelator diethylenetriaminepentaacetic acid (0.1 mM) or the hydroxyl radical scavengers like mannitol (20 mM) and dimethyl sulphoxide (20 mM) indicating the non-involvement of *OH radicals and Fenton's chemistry in this process. However, reduced glutathione (5 mM), a quinone scavenger, almost completely abolishes the DA effect on mitochondrial complex I and complex IV activities, while tyrosinase (250 units/ml) which catalyses the conversion of DA to quinone products dramatically enhances the former effect. The results suggest the predominant involvement of quinone products instead of reactive oxygen radicals in long-term DA-mediated inactivation of complex I and complex IV. This is further indicated from the fact that significant amount of quinones and quinoprotein adducts (covalent adducts of reactive quinones with protein thiols) are formed during incubation of mitochondria with DA. Monoamine oxidase A (MAO-A) inhibitor clorgyline also provides variable but significant protection against DA induced inactivation of complex I and complex IV activities, presumably again through inhibition of quinoprotein formation. Mitochondrial ability to reduce tetrazolium dye 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) in presence of a respiratory substrate like succinate (10 mM) is also reduced by nearly 85% following 2 h incubation with 0.4 mM DA. This effect of DA on mitochondrial function is also dose-dependent and presumably mediated by quinone products of DA oxidation. The mitochondrial dysfunction induced by dopamine during extended periods of incubation as reported here have important implications in the context of dopaminergic neuronal death in Parkinson's disease (PD). 相似文献
103.
A 2500-locus bin map of wheat homoeologous group 5 provides insights on gene distribution and colinearity with rice 总被引:3,自引:0,他引:3
Linkiewicz AM Qi LL Gill BS Ratnasiri A Echalier B Chao S Lazo GR Hummel DD Anderson OD Akhunov ED Dvorák J Pathan MS Nguyen HT Peng JH Lapitan NL Miftahudin Gustafson JP La Rota CM Sorrells ME Hossain KG Kalavacharla V Kianian SF Sandhu D Bondareva SN Gill KS Conley EJ Anderson JA Fenton RD Close TJ McGuire PE Qualset CO Dubcovsky J 《Genetics》2004,168(2):665-676
We constructed high-density deletion bin maps of wheat chromosomes 5A, 5B, and 5D, including 2338 loci mapped with 1052 EST probes and 217 previously mapped loci (total 2555 loci). This information was combined to construct a consensus chromosome bin map of group 5 including 24 bins. A relatively higher number of loci were mapped on chromosome 5B (38%) compared to 5A (34%) and 5D (28%). Differences in the levels of polymorphism among the three chromosomes were partially responsible for these differences. A higher number of duplicated loci was found on chromosome 5B (42%). Three times more loci were mapped on the long arms than on the short arms, and a significantly higher number of probes, loci, and duplicated loci were mapped on the distal halves than on the proximal halves of the chromosome arms. Good overall colinearity was observed among the three homoeologous group 5 chromosomes, except for the previously known 5AL/4AL translocation and a putative small pericentric inversion in chromosome 5A. Statistically significant colinearity was observed between low-copy-number ESTs from wheat homoeologous group 5 and rice chromosomes 12 (88 ESTs), 9 (72 ESTs), and 3 (84 ESTs). 相似文献
104.
A 2600-locus chromosome bin map of wheat homoeologous group 2 reveals interstitial gene-rich islands and colinearity with rice 总被引:8,自引:0,他引:8
Conley EJ Nduati V Gonzalez-Hernandez JL Mesfin A Trudeau-Spanjers M Chao S Lazo GR Hummel DD Anderson OD Qi LL Gill BS Echalier B Linkiewicz AM Dubcovsky J Akhunov ED Dvorák J Peng JH Lapitan NL Pathan MS Nguyen HT Ma XF Miftahudin Gustafson JP Greene RA Sorrells ME Hossain KG Kalavacharla V Kianian SF Sidhu D Dilbirligi M Gill KS Choi DW Fenton RD Close TJ McGuire PE Qualset CO Anderson JA 《Genetics》2004,168(2):625-637
The complex hexaploid wheat genome offers many challenges for genomics research. Expressed sequence tags facilitate the analysis of gene-coding regions and provide a rich source of molecular markers for mapping and comparison with model organisms. The objectives of this study were to construct a high-density EST chromosome bin map of wheat homoeologous group 2 chromosomes to determine the distribution of ESTs, construct a consensus map of group 2 ESTs, investigate synteny, examine patterns of duplication, and assess the colinearity with rice of ESTs assigned to the group 2 consensus bin map. A total of 2600 loci generated from 1110 ESTs were mapped to group 2 chromosomes by Southern hybridization onto wheat aneuploid chromosome and deletion stocks. A consensus map was constructed of 552 ESTs mapping to more than one group 2 chromosome. Regions of high gene density in distal bins and low gene density in proximal bins were found. Two interstitial gene-rich islands flanked by relatively gene-poor regions on both the short and long arms and having good synteny with rice were discovered. The map locations of two ESTs indicated the possible presence of a small pericentric inversion on chromosome 2B. Wheat chromosome group 2 was shown to share syntenous blocks with rice chromosomes 4 and 7. 相似文献
105.
Randhawa HS Dilbirligi M Sidhu D Erayman M Sandhu D Bondareva S Chao S Lazo GR Anderson OD Miftahudin Gustafson JP Echalier B Qi LL Gill BS Akhunov ED Dvorák J Linkiewicz AM Ratnasiri A Dubcovsky J Bermudez-Kandianis CE Greene RA Sorrells ME Conley EJ Anderson JA Peng JH Lapitan NL Hossain KG Kalavacharla V Kianian SF Pathan MS Nguyen HT Endo TR Close TJ McGuire PE Qualset CO Gill KS 《Genetics》2004,168(2):677-686
To localize wheat (Triticum aestivum L.) ESTs on chromosomes, 882 homoeologous group 6-specific ESTs were identified by physically mapping 7965 singletons from 37 cDNA libraries on 146 chromosome, arm, and sub-arm aneuploid and deletion stocks. The 882 ESTs were physically mapped to 25 regions (bins) flanked by 23 deletion breakpoints. Of the 5154 restriction fragments detected by 882 ESTs, 2043 (loci) were localized to group 6 chromosomes and 806 were mapped on other chromosome groups. The number of loci mapped was greatest on chromosome 6B and least on 6D. The 264 ESTs that detected orthologous loci on all three homoeologs using one restriction enzyme were used to construct a consensus physical map. The physical distribution of ESTs was uneven on chromosomes with a tendency toward higher densities in the distal halves of chromosome arms. About 43% of the wheat group 6 ESTs identified rice homologs upon comparisons of genome sequences. Fifty-eight percent of these ESTs were present on rice chromosome 2 and the remaining were on other rice chromosomes. Even within the group 6 bins, rice chromosomal blocks identified by 1-6 wheat ESTs were homologous to up to 11 rice chromosomes. These rice-block contigs were used to resolve the order of wheat ESTs within each bin. 相似文献
106.
Lazo GR Chao S Hummel DD Edwards H Crossman CC Lui N Matthews DE Carollo VL Hane DL You FM Butler GE Miller RE Close TJ Peng JH Lapitan NL Gustafson JP Qi LL Echalier B Gill BS Dilbirligi M Randhawa HS Gill KS Greene RA Sorrells ME Akhunov ED Dvorák J Linkiewicz AM Dubcovsky J Hossain KG Kalavacharla V Kianian SF Mahmoud AA Miftahudin Ma XF Conley EJ Anderson JA Pathan MS Nguyen HT McGuire PE Qualset CO Anderson OD 《Genetics》2004,168(2):585-593
This report describes the rationale, approaches, organization, and resource development leading to a large-scale deletion bin map of the hexaploid (2n = 6x = 42) wheat genome (Triticum aestivum L.). Accompanying reports in this issue detail results from chromosome bin-mapping of expressed sequence tags (ESTs) representing genes onto the seven homoeologous chromosome groups and a global analysis of the entire mapped wheat EST data set. Among the resources developed were the first extensive public wheat EST collection (113,220 ESTs). Described are protocols for sequencing, sequence processing, EST nomenclature, and the assembly of ESTs into contigs. These contigs plus singletons (unassembled ESTs) were used for selection of distinct sequence motif unigenes. Selected ESTs were rearrayed, validated by 5′ and 3′ sequencing, and amplified for probing a series of wheat aneuploid and deletion stocks. Images and data for all Southern hybridizations were deposited in databases and were used by the coordinators for each of the seven homoeologous chromosome groups to validate the mapping results. Results from this project have established the foundation for future developments in wheat genomics. 相似文献
107.
We investigated the effect of administration of docosahexaenoic acid (C22:6, n-3; 300 mg/kg.day, for 12 weeks) on the degree of membrane order and membrane-bound acetylcholinesterase activity of the cerebral cortex synaptic plasma membrane in male Wistar rats. Docosahexaenoic acid levels in the synaptic plasma membrane increased significantly by 16% over levels in control rats concomitant with an increase in the molar ratio of docosahexaenoic acid to arachidonic acid. Synaptic plasma membrane order, assessed by 1,6-diphenyl-1,3,5-hexatriene, which measures order of the bulk internal hydrophobic lipid core, decreased significantly in the docosahexaenoic acid-fed rats. Lateral mobility of both global and annular lipids measured by pyrene also increased. Acetylcholinesterase activity of the synaptic plasma membrane was unaffected, and synaptic plasma membrane phospholipid contents increased in the docosahexaenoic acid-fed rats, with a concomitant decrease in the cholesterol/phospholipid molar ratio. Lipid peroxide and reactive oxygen species, indicators of tissue oxidative stress, decreased in both the cerebral cortex synaptosome and homogenate of the docosahexaenoic acid-fed rats. Arrhenius plot showed a break point in acetylcholinesterase activity at 22 degrees C and 24 degrees C in plasma membranes from docosahexaenoic acid-fed and control rats, respectively. The present experiment indicates that chronic administration of docosahexaenoic acid does not affect synaptic acetylcholinesterase activity and evoke oxidative stress, although it increases the disorder of the global and annular lipids of rat synaptic plasma membranes. 相似文献
108.
Subhadipa Sengupta Dipankar Chakraborti Hossain A. Mondal Sampa Das 《Plant cell reports》2010,29(3):261-271
Rice, the major food crop of world is severely affected by homopteran sucking pests. We introduced coding sequence of Allium sativum leaf agglutinin, ASAL, in rice cultivar IR64 to develop sustainable resistance against sap-sucking planthoppers as well as eliminated the selectable
antibiotic-resistant marker gene hygromycin phosphotransferase (hpt) exploiting cre/lox site-specific recombination system. An expression vector was constructed containing the coding sequence
of ASAL, a potent controlling agent against green leafhoppers (GLH, Nephotettix virescens) and brown planthopper (BPH, Nilaparvata lugens). The selectable marker (hpt) gene cassette was cloned within two lox sites of the same vector. Alongside, another vector was developed with chimeric cre recombinase gene cassette. Reciprocal crosses were performed between three single-copy T0 plants with ASAL- lox-hpt-lox T-DNA and three single-copy T0 plants with cre-bar T-DNA. Marker gene excisions were detected in T1 hybrids through hygromycin sensitivity assay. Molecular analysis of T1 plants exhibited 27.4% recombination efficiency. T2 progenies of L03C04(1) hybrid parent showed 25% cre negative ASAL-expressing plants. Northern blot, western blot and ELISA showed significant level of ASAL expression in five marker-free T2 progeny plants. In planta bioassay of GLH and BPH performed on these T2 progenies exhibited radical reduction in survivability and fecundity compared with the untransformed control plants. 相似文献
109.
110.
Phospholipids are fascinating in terms of important bio-functional compounds. The present work investigated the effect of polyunsaturated phosphatidylcholine (PC) and phosphatidylserine (PS) on butyrate-induced growth inhibition, differentiation and apoptosis using Caco-2 cells. Growth inhibition of Caco-2 cells became apparent 24 h after addition of PC while it took 48 h with PS. Alkaline phosphatase activity of Caco-2 cells increased with combined PC or PS and sodium butyrate (NaBT) at 72 h, indicating that PC and PS enhanced cell differentiation in the presence of NaBT. An increased enrichment factor was also found when cells were treated with combinations of PC or PS and NaBT. These results suggest that marine PC and PS can be considered to be potentially useful colon cancer chemotherapy agents with high bio-availability. 相似文献