全文获取类型
收费全文 | 2904篇 |
免费 | 234篇 |
国内免费 | 1篇 |
出版年
2023年 | 20篇 |
2022年 | 35篇 |
2021年 | 103篇 |
2020年 | 48篇 |
2019年 | 76篇 |
2018年 | 80篇 |
2017年 | 72篇 |
2016年 | 117篇 |
2015年 | 186篇 |
2014年 | 193篇 |
2013年 | 226篇 |
2012年 | 277篇 |
2011年 | 221篇 |
2010年 | 149篇 |
2009年 | 128篇 |
2008年 | 156篇 |
2007年 | 157篇 |
2006年 | 153篇 |
2005年 | 134篇 |
2004年 | 99篇 |
2003年 | 92篇 |
2002年 | 88篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 19篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1973年 | 6篇 |
1967年 | 4篇 |
1962年 | 4篇 |
排序方式: 共有3139条查询结果,搜索用时 15 毫秒
991.
Daniela Moreno Federico J. Berli Patricia N. Piccoli Rub��n Bottini 《Journal of Plant Growth Regulation》2011,30(2):220-228
Carbon allocation within grapevines may affect berry growth and development. The plant hormones gibberellins (GAs) and abscisic
acid (ABA) control various processes across the plant life and both have been involved in assimilate production and transport
in different species. Hence, this work examined the distribution of sugars (sucrose, fructose, and glucose) and starch in
grapevines at veraison after foliar applications of GA3, ABA, and an inhibitor of GA biosynthesis, paclobutrazol (PBZ). The results demonstrated that GA3 increased total grapevine mass, with carbon allocated to the whole grapevine (as structural and soluble carbohydrates). Both
GA3 and ABA increased monosaccharide (glucose and fructose) levels in berries (up to tenfold) and roots (up to threefold). However,
GA3 increased the net carbon fixation whereas ABA did not. PBZ diminished most growth parameters except grapevine mass, and allocated
more carbohydrates to roots (up to threefold more sucrose and starch). Such results indicate that GAs promote net carbon fixation
and transport, whereas ABA as a stress signal only enhances sugar transport; notwithstanding the two hormones promoted carbon
allocation toward roots and berries. 相似文献
992.
Velasco P Francisco M Moreno DA Ferreres F García-Viguera C Cartea ME 《Phytochemical analysis : PCA》2011,22(2):144-152
Introduction – Brassica vegetables have been related to the prevention of cancer and degenerative diseases, owing to their glucosinolate and phenolic content. Objective – Identification of glucosinolates, flavonoids and hydroxycinnamic acids in representative varieties of kale, cabbage and leaf rape. Methodology – One local variety of each crop was evaluated in this study using a multi‐purpose chromatographic method that simultaneously separates glucosinolates and phenolics. Chromatograms were recorded at 330 nm for flavonoid glycosides and acylated derivatives and 227 nm for glucosinolates. Results – Eight glucosinolates were identified in kale and cabbage, which exhibited the same glucosinolate profile, and 11 glucosinolates were identified in leaf rape. Furthermore, 20 flavonoids and 10 hydroxycinnamic acids were detected in kale and cabbage, while 17 flavonoids and eight hydroxycinnamic acids were found in leaf rape. Conclusions – This study has provided a deeper and comprehensive identification of health‐promoting compounds in kale, cabbage and leaf rape, thus showing that they are a good source of glucosinolates and phenolic antioxidants. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
993.
MtCRE1-dependent cytokinin signaling integrates bacterial and plant cues to coordinate symbiotic nodule organogenesis in Medicago truncatula 总被引:1,自引:0,他引:1
994.
995.
996.
Abraham S Hadd MJ Tran L Vickers T Sindac J Milanov ZV Holladay MW Bhagwat SS Hua H Ford Pulido JM Cramer MD Gitnick D James J Dao A Belli B Armstrong RC Treiber DK Liu G 《Bioorganic & medicinal chemistry letters》2011,21(18):5296-5300
The synthesis and SAR for a novel series of pyrrolotriazines as pan-Aurora kinase inhibitors are described. Optimization of the cyclopropane carboxamide terminus of lead compound 1 resulted in analogs with high cellular activity and improved rat PK profiles. Notably, compound 17l demonstrated tumor growth inhibition in a mouse xenograft model. 相似文献
997.
998.
Di Cairano ES Davalli AM Perego L Sala S Sacchi VF La Rosa S Finzi G Placidi C Capella C Conti P Centonze VE Casiraghi F Bertuzzi F Folli F Perego C 《The Journal of biological chemistry》2011,286(16):14007-14018
Glutamate is the major excitatory neurotransmitter of the central nervous system (CNS) and may induce cytotoxicity through persistent activation of glutamate receptors and oxidative stress. Its extracellular concentration is maintained at physiological concentrations by high affinity glutamate transporters of the solute carrier 1 family (SLC1). Glutamate is also present in islet of Langerhans where it is secreted by the α-cells and acts as a signaling molecule to modulate hormone secretion. Whether glutamate plays a role in islet cell viability is presently unknown. We demonstrate that chronic exposure to glutamate exerts a cytotoxic effect in clonal β-cell lines and human islet β-cells but not in α-cells. In human islets, glutamate-induced β-cell cytotoxicity was associated with increased oxidative stress and led to apoptosis and autophagy. We also provide evidence that the key regulator of extracellular islet glutamate concentration is the glial glutamate transporter 1 (GLT1). GLT1 localizes to the plasma membrane of β-cells, modulates hormone secretion, and prevents glutamate-induced cytotoxicity as shown by the fact that its down-regulation induced β-cell death, whereas GLT1 up-regulation promoted β-cell survival. In conclusion, the present study identifies GLT1 as a new player in glutamate homeostasis and signaling in the islet of Langerhans and demonstrates that β-cells critically depend on its activity to control extracellular glutamate levels and cellular integrity. 相似文献
999.
Differential responses of five cherry tomato varieties to water stress: changes on phenolic metabolites and related enzymes 总被引:1,自引:0,他引:1
Sánchez-Rodríguez E Moreno DA Ferreres F Rubio-Wilhelmi Mdel M Ruiz JM 《Phytochemistry》2011,72(8):723-729
Different tomato cultivars (Solanum lycopersicum L.) with differences in tolerance to drought were subjected to moderate water stress to test the effects on flavonoids and caffeoyl derivatives and related enzymes. Our results indicate that water stress resulted in decreased shikimate pathway (DAHP synthase, shikimate dehydrogenase, phenylalanine ammonium lyase, cinnamate 4-hydroxylase, 4-coumarate CoA ligase) and phenolic compounds (caffeoylquinic acid derivatives, quercetin and kaempferol) in the cultivars more sensitive to water stress. However, cv. Zarina is more tolerant, and registered a rise in querc-3-rut-pent, kaempferol-3-api-rut, and kaempferol-3-rut under the treatment of water stress. Moreover, this cultivar show increased activities of flavonoid and phenylpropanoid synthesis and decreased in degradation-related enzymes. These results show that moderate water stress can induce shikimate pathway in tolerant cultivar. 相似文献
1000.
? Underwater photosynthesis by aquatic plants is often limited by low availability of CO(2), and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock pools. ? Leaves high or low in malate were evaluated for underwater net photosynthesis and apparent photorespiration at a range of CO(2) and O(2) concentrations. ? CAM activity was indicated by 9.7-fold higher leaf malate at dawn, compared with at dusk, and also by changes in the titratable acidity (μmol H(+) equivalents) of leaves. Leaves high in malate showed not only higher underwater net photosynthesis at low external CO(2) concentrations but also lower apparent photorespiration. Suppression by CAM of apparent photorespiration was evident at a range of O(2) concentrations, including values below air equilibrium. At a high O(2) concentration of 2.2-fold the atmospheric equilibrium concentration, net photosynthesis was reduced substantially and, although it remained positive in leaves containing high malate concentrations, it became negative in those low in malate. ? CAM in aquatic plants enables higher rates of underwater net photosynthesis over large O(2) and CO(2) concentration ranges in floodwaters, via increased CO(2) fixation and suppression of photorespiration. 相似文献