全文获取类型
收费全文 | 635篇 |
免费 | 22篇 |
出版年
2022年 | 12篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 36篇 |
2014年 | 25篇 |
2013年 | 43篇 |
2012年 | 49篇 |
2011年 | 56篇 |
2010年 | 46篇 |
2009年 | 21篇 |
2008年 | 23篇 |
2007年 | 33篇 |
2006年 | 34篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 19篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有657条查询结果,搜索用时 390 毫秒
21.
22.
23.
Priyanka Jha Swati Chahal Devendra Kumar Pandey Joginder Singh Ram Prasad Vijay Kumar 《Phyton》2020,89(4):779-794
The use of medicinal plants for different therapeutic values is well
documented in African continent. African diverse biodiversity hotspots provide
a wide range of endemic species, which ensures a potential medicinal value.
The feasible conservation approach and sustainable harvesting for the medicinal
species remains a huge challenge. However, conservation approach through different biotechnological tools such as micropropagation, somatic embryogenesis,
synthetic seed production, hairy root culture, molecular markers based study
and cryopreservation of endemic African medicinal species is much crucial. In
this review, an attempt has been made to provide different in vitro biotechnological approaches for the conservation of African medicinal species. The present
review will be helpful in further technology development and deciding the priorities at decision-making levels for in vitro conservation and sustainable use of
African medicinal species. 相似文献
24.
Satish Mohan Gunasekar Palanikumar Asensio Juan A. Agrawal Devendra K. 《Molecular and cellular biochemistry》2020,474(1-2):219-228
Molecular and Cellular Biochemistry - Intracoronary stenting is a common procedure in patients with coronary artery disease (CAD). Stent deployment stretches and denudes the endothelial layer,... 相似文献
25.
Anukool Vaishnav Shekhar Jain Amrita Kasotia Sarita Kumari Rajarshi Kumar Gaur Devendra Kumar Choudhary 《Archives of microbiology》2013,195(8):571-577
To understand protective roles of nitric oxide against salt stress, the effects of exogenous sodium nitroprusside on activities of lipoxygenase, peroxidase, phenylalanine ammonialyase, catalase, superoxide dismutase enzymes, proline accumulation, and distribution of sodium in soybean plants under salt were determined. Application of sodium nitroprusside + bacterium enhanced plant growth-promotion characteristics, activities of different enzymes, and proline accumulation in the presence of sodium nitroprusside under salt stress. Treatment with NaCl at 200 mM and sodium nitroprusside (0.1 mM) reduced Na+ levels but increased K+ levels in leaves in comparison with the NaCl-treated plants. Correspondingly, the plants treated with exogenous sodium nitroprusside and NaCl maintained a lower ratio of [Na+]/[K+] in NaCl-stressed plants. 相似文献
26.
Nilesh Kumar Khatediya Dipak Vrajlal Parmar Mahesh Kumar Mahatma Manish Pareek 《Archives Of Phytopathology And Plant Protection》2013,46(9-10):530-549
AbstractFungal infections cause several metabolic changes to the plants, which can affect its physiology and survival in various ways. In the present study, we have analysed various phenolic compounds and activity of oxidative enzymes in healthy and Sclerotium rolfsii-infected groundnut genotypes. Increased phenolics content and higher activity of oxidative enzymes was observed in the tolerant genotype (CS 19, GG 16) followed by susceptible genotype (GG 20, TG 37A). Among the phenolic compounds tested, chlorogenic acid content has increased greatly in leaf, stem and root of infected tolerant genotypes compared to the respective controls. In vitro growth of S. rolfsii showed significant inhibition at concentrations 500 and 1000 µg/mL of phenolic compounds in the radial growth inhibition assay. These results have strongly suggested that, higher accumulation of chlorogenic acid could be an important factor in imparting resistance and protecting groundnut against S. rolfsii infection in tolerant genotypes. 相似文献
27.
Lesley A. Warren Patricia A. Maurice Nagina Parmar F. Grant Ferris 《Geomicrobiology journal》2013,30(1):93-115
Microbial degradation of urea was investigated as a potential geochemical catalyst for Ca carbonate precipitation and associated solid phase capture of common groundwater contaminants (Sr, UO2, Cu) in laboratory batch experiments. Bacterial degradation of urea increased pH and promoted Ca carbonate precipitation in both bacterial control and contaminant treatments. Associated solid phase capture of Sr was highly effective, capturing 95% of the 1 mM Sr added within 24 h. The results for Sr are consistent with solid solution formation rather than discrete Sr carbonate phase precipitation. In contrast, UO2 capture was not as effective, reaching only 30% of the initial 1 mM UO2 added, and also reversible, dropping to 7% by 24 h. These results likely reflect differing sites of incorporation of these two elements-Ca lattice sites for Sr versus crystal defect sites for UO2. Cu sequestration was poor, resulting from toxicity of the metal to the bacteria, which arrested urea degradation and concomitant Ca carbonate precipitation. Scanning electron microscopy (SEM) indicated a variety of morphologies reminiscent of those observed in the marine stromatolite literature. In bacterial control treatments, X-ray diffraction (XRD) analyses indicated only calcite; while in the presence of either Sr or UO2, both calcite and vaterite, a metastable polymorph of Ca carbonate, were identified. Tapping mode atomic force microscopy (AFM) indicated differences in surface microtopography among abiotic, bacterial control, and bacterial contaminant systems. These results indicate that Ca carbonate precipitation induced by passive biomineralization processes is highly effective and may provide a useful bioremediation strategy for Ca carbonate-rich aquifers where Sr contamination issues exist. 相似文献
28.
Lotta Kilpinen Feven Tigistu-Sahle Sofia Oja Dario Greco Amarjit Parmar P?ivi Saavalainen Janne Nikkil? Matti Korhonen Petri Lehenkari Reijo K?kel? Saara Laitinen 《Journal of lipid research》2013,54(3):622-635
Human mesenchymal stem/stromal cells (hMSC) are increasingly used in advanced cellular therapies. The clinical use of hMSCs demands sequential cell expansions. As it is well established that membrane glycerophospholipids (GPL) provide precursors for signaling lipids that modulate cellular functions, we studied the effect of the donor''s age and cell doublings on the GPL profile of human bone marrow MSC (hBMSC). The hBMSCs, which were harvested from five young and five old adults, showed clear compositional changes during expansion seen at the level of lipid classes, lipid species, and acyl chains. The ratio of phosphatidylinositol to phosphatidylserine increased toward the late-passage samples. Furthermore, 20:4n-6-containing species of phosphatidylcholine and phosphatidylethanolamine accumulated while the species containing monounsaturated fatty acids (FA) decreased during passaging. Additionally, in the total FA pool of the cells, 20:4n-6 increased, which happened at the expense of n-3 polyunsaturated FAs, especially 22:6n-3. The GPL and FA correlated with the decreased immunosuppressive capacity of hBMSCs during expansion. Our observations were further supported by alterations in the gene expression levels of several enzymes involved in lipid metabolism and immunomodulation. The results show that extensive expansion of hBMSCs harmfully modulates membrane GPLs, affecting lipid signaling and eventually impairing functionality. 相似文献
29.
Kim Lam Chiok Tarek Addwebi Jean Guard Devendra H. Shah 《Applied and environmental microbiology》2013,79(24):7857-7866
Dimethyl adenosine transferase (KsgA) performs diverse roles in bacteria, including ribosomal maturation and DNA mismatch repair, and synthesis of KsgA is responsive to antibiotics and cold temperature. We previously showed that a ksgA mutation in Salmonella enterica serovar Enteritidis results in impaired invasiveness in human and avian epithelial cells. In this study, we tested the virulence of a ksgA mutant (the ksgA::Tn5 mutant) of S. Enteritidis in orally challenged 1-day-old chickens. The ksgA::Tn5 mutant showed significantly reduced intestinal colonization and organ invasiveness in chickens compared to those of the wild-type (WT) parent. Phenotype microarray (PM) was employed to compare the ksgA::Tn5 mutant and its isogenic wild-type strain for 920 phenotypes at 28°C, 37°C, and 42°C. At chicken body temperature (42°C), the ksgA::Tn5 mutant showed significantly reduced respiratory activity with respect to a number of carbon, nitrogen, phosphate, sulfur, and peptide nitrogen nutrients. The greatest differences were observed in the osmolyte panel at concentrations of ≥6% NaCl at 37°C and 42°C. In contrast, no major differences were observed at 28°C. In independent growth assays, the ksgA::Tn5 mutant displayed a severe growth defect in high-osmolarity (6.5% NaCl) conditions in nutrient-rich (LB) and nutrient-limiting (M9 minimum salts) media at 42°C. Moreover, the ksgA::Tn5 mutant showed significantly reduced tolerance to oxidative stress, but its survival within macrophages was not impaired. Unlike Escherichia coli, the ksgA::Tn5 mutant did not display a cold-sensitivity phenotype; however, it showed resistance to kasugamycin and increased susceptibility to chloramphenicol. To the best of our knowledge, this is the first report showing the role of ksgA in S. Enteritidis virulence in chickens, tolerance to high osmolarity, and altered susceptibility to kasugamycin and chloramphenicol. 相似文献
30.
Proteolytic enzymes of the caspase family, which reside as latent precursors in most nucleated metazoan cells, are core effectors of
apoptosis. Of them, the executioner caspases- 3 and -7 exist within the cytosol as inactive dimers and are activated by a process
called dimerization. Caspase inhibition is looked upon as a promising approach for treating multiple diseases. Though caspases
have been extensively studied in the human system, their role in eukaryotic pathogens and parasites of human hosts has not drawn
enough attention. In protein sequence analysis, caspases of blood flukes (Schistosoma spp) were revealed to have a low sequence
identity with their counterparts in human and other mammalian hosts, which encouraged us to analyse interacting domains that
participate in dimerization of caspases in the parasite and to reveal differences, if any, between the host-parasite systems.
Significant differences in the molecular surface arrangement of the dimer interfaces reveal that in schistosomal caspases only eight
out of forty dimer conformations are similar to human caspase structures. Thus, the parasite-specific dimer conformations (that are
different from caspases of the host) may emerge as potential drug targets of therapeutic value against schistosomal infections.
Three important factors namely, the size of amino acids, secondary structures and geometrical arrangement of interacting domains
influence the pattern of caspase dimer formation, which, in turn, is manifested in varied structural conformations of caspases in the
parasite and its human hosts. 相似文献