全文获取类型
收费全文 | 2476篇 |
免费 | 164篇 |
国内免费 | 5篇 |
专业分类
2645篇 |
出版年
2023年 | 21篇 |
2022年 | 57篇 |
2021年 | 98篇 |
2020年 | 48篇 |
2019年 | 58篇 |
2018年 | 69篇 |
2017年 | 74篇 |
2016年 | 89篇 |
2015年 | 110篇 |
2014年 | 141篇 |
2013年 | 208篇 |
2012年 | 247篇 |
2011年 | 187篇 |
2010年 | 129篇 |
2009年 | 113篇 |
2008年 | 123篇 |
2007年 | 115篇 |
2006年 | 105篇 |
2005年 | 105篇 |
2004年 | 88篇 |
2003年 | 74篇 |
2002年 | 63篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1972年 | 7篇 |
排序方式: 共有2645条查询结果,搜索用时 15 毫秒
41.
Transformation of Nicotiana tabacum with a native cry1Ia5 gene confers complete protection against Heliothis armigera 总被引:2,自引:0,他引:2
Selvapandiyan Angamuthu Reddy Vanga S. Kumar P. Anand Tewari Krishna K. Bhatnagar Raj K. 《Molecular breeding : new strategies in plant improvement》1998,4(6):473-478
A cry1Ia5 insecticidal toxin coding gene has been cloned from an Indian isolate of Bacillus thuringiensis. Sequence analyses of the cry1Ia5 gene revealed the absence of potential polyadenylation signal sequences thus making it a suitable candidate for expression in plants without extensive modification. This possibility was examined by subcloning the cry1Ia5 gene into a plant expression vector and then transferring it to Nicotiana tabacum through Agrobacterium-mediated transformation. Our results demonstrate that N. tabacum with a stably integrated native cry1Ia5 gene afforded complete protection against predation by Heliothis armigera. Forty three percent of the transgenic plants displayed a high level of protection against insect predation. The protection obtained in transgenic plants with the cry1Ia5 gene was comparable to that obtained with the synthetically modified cry1A(b) or cry1A(c) genes. The results demonstrate that novel insecticidal genes already exist in nature that do not require extensive modifications for efficient expression in plants. 相似文献
42.
43.
44.
Priya Padmanabhan Mukund R. Shukla J. Alan Sullivan Praveen K. Saxena 《Plant Cell, Tissue and Organ Culture》2017,128(1):145-160
C4 plants can efficiently accumulate CO2 in leaves and thus reduce wasteful oxygen fixation by the RuBisCO enzyme. Three C4 enzymes, namely carbonic anhydrase (CA), phosphoenol pyruvate (PEPC) and pyruvate orthophosphate dikinase (PPDK), were over expressed in Oryza sativa L. ssp. indica var. Khitish under the control of green tissue specific promoters PD54o, PEPC and PPDK, respectively. Integration of these genes was confirmed by Southern hybridization. The relative expression of PEPC, CA and PPDK were, respectively, 6.75, 6.57 and 3.6-fold higher in transgenic plants compared to wild type plants (control). Photosynthetic efficiency of the transgenic plants increased significantly along with a 12?% increase in grain yield compared to wild type plants. Compared to control plants, transgenic plants also showed phenotypic changes such as increased leaf blade size, root biomass, and plant height and anatomical changes such as greater leaf vein number, bundle sheath cells, and bulliform cells. Our findings indicate that the combined over expression of these three enzymes is an efficient strategy for incorporating beneficial physiological and anatomical features that will enable subsequent yield enhancement in C3 rice plants. 相似文献
45.
In this study filarial recombinant protein or DNA vaccine constructs encoding BmALT-2 and BmVAH as single or as cocktail antigens were evaluated. Male jirds were immunized intramuscularly with DNA vaccine constructs or were immunized intraperitoneally with protein vaccine. The single and bicistronic DNA constructs induced substantial interferon-γ responses in spleen cells; antigen-specific responses were higher following immunization with the bicistronic cocktail construct and evoked a significant protective response of 57% in jirds challenged with Brugia malayi that was similar in the antibody-dependent cellular cytotoxicity (ADCC) assay and micropore chamber experiment. The cocktail protein vaccines induced a mixture of IgG2a (Th1) and IgG1 (Th2) responses with 80% protective response when challenged with B. malayi infective larvae. However, the single protein vaccine rALT-2 induced Th2 (IgG1/IgG3) with a 70% protective response and rVAH induced Th1 (IgG2a) with a lower proliferative response with 60% protection following challenge with B. malayi infective larvae. These results suggest that filarial cocktail protein vaccines are able to elicit substantial immune and protective responses when compared with single antigen vaccination in suitably vaccinated jirds. 相似文献
46.
Agrodrench: a novel and effective agroinoculation method for virus-induced gene silencing in roots and diverse Solanaceous species 总被引:15,自引:0,他引:15
Ryu CM Anand A Kang L Mysore KS 《The Plant journal : for cell and molecular biology》2004,40(2):322-331
Summary Virus-induced gene silencing (VIGS) is an extremely powerful tool for plant functional genomics. We used Tobacco rattle virus (TRV)-derived VIGS vectors expressed from binary vectors within Agrobacterium to induce RNA silencing in plants. Leaf infiltration is the most common method of agroinoculation used for VIGS but this method has limitations as it is laborious for large-scale screening and some plants are difficult to infiltrate. Here we have developed a novel and simple method of agroinoculation, called 'agrodrench', where soil adjacent to the plant root is drenched with an Agrobacterium suspension carrying the TRV-derived VIGS vectors. By agrodrench we successfully silenced the expression of phytoene desaturase (PDS), a 20S proteasome subunit (PB7) or Mg-protoporphyrin chelatase (Chl H) encoding genes in Nicotiana benthamiana and in economically important crops such as tomato, pepper, tobacco, potato, and Petunia, all belonging to the Solanaceae family. An important aspect of agrodrench is that it can be used for VIGS in very young seedlings, something not possible by the leaf infiltration method, which usually requires multiple fully expanded leaves for infiltration. We also demonstrated that VIGS functioned to silence target genes in plant roots. The agrodrench method of agroinoculation was more efficient than the leaf infiltration method for VIGS in roots. Agrodrench will facilitate rapid large-scale functional analysis of cDNA libraries and can also be applied to plants that are not currently amenable to VIGS technology by conventional inoculation methods. 相似文献
47.
Ruby Priya Damandeep Kaur Komal Attri Sandeep Kaur Deepinder Sharda Diptiman Choudhury O. P. Pandey 《Luminescence》2024,39(2):e4652
In this article, we have reported the effect of varying concentration of europium (Eu) in (50 − x)% P2O5–25% Na2O–24% CaO–% Eu2O3, where x = 1, 3, 5. The glass samples were synthesised via conventional melt-quench method. The impact of europium ion (Eu3+) on the structural, optical and luminescent properties of phosphate soda lime glasses has been studied using X-ray diffraction (XRD), Fourier-transformed infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy and photoluminescent techniques. The amorphous nature of glass samples was confirmed by XRD patterns. FTIR confirmed the presence of various functional groups. The emission spectra of synthesised samples exhibited intense emission peaks corresponding to Eu3+ under excitation at 393 nm. Among all the peaks, the maximum intensity was observed for 5D0 → 7F2 transition. Judd–Ofelt (J–O) parameters (Ω2, Ω4) and other radiative parameters such as band width, radiative transition probabilities, stimulated emission cross-sections and branching ratio were determined from emission spectra. The other photometric parameters such as CIE coordinates and colour purity were also determined. Furthermore, cytotoxic studies were carried out on normal cell line human embryonic kidney cells (HEK-293) using MTT assay. Results showed that the prepared samples significantly enhanced growth in glass sample-treated cells as compared to control cells. These findings suggest that synthesised glass samples are biocompatible in nature and have potential for applications in display devices and biomedical research area. 相似文献
48.
Lana Sargent Mike Nalls Andrew Singleton Priya Palta Anna Kucharska-Newton Jim Pankow Hunter Young Weihong Tang Pamela Lutsey Amy Olex Jered M. Wendte Danni Li Alvaro Alonso Michael Griswold B. Gwen Windham Stefania Baninelli Luigi Ferrucci 《Aging cell》2024,23(2):e14030
Aging adults experience increased health vulnerability and compromised abilities to cope with stressors, which are the clinical manifestations of frailty. Frailty is complex, and efforts to identify biomarkers to detect frailty and pre-frailty in the clinical setting are rarely reproduced across cohorts. We developed a predictive model incorporating biological and clinical frailty measures to identify robust biomarkers across data sets. Data were from two large cohorts of older adults: “Invecchiare in Chianti (Aging in Chianti, InCHIANTI Study”) (n = 1453) from two small towns in Tuscany, Italy, and replicated in the Atherosclerosis Risk in Communities Study (ARIC) (n = 6508) from four U.S. communities. A complex systems approach to biomarker selection with a tree-boosting machine learning (ML) technique for supervised learning analysis was used to examine biomarker population differences across both datasets. Our approach compared predictors with robust, pre-frail, and frail participants and examined the ability to detect frailty status by race. Unique biomarker features identified in the InCHIANTI study allowed us to predict frailty with a model accuracy of 0.72 (95% confidence interval (CI) 0.66–0.80). Replication models in ARIC maintained a model accuracy of 0.64 (95% CI 0.66–0.72). Frail and pre-frail Black participant models maintained a lower model accuracy. The predictive panel of biomarkers identified in this study may improve the ability to detect frailty as a complex aging syndrome in the clinical setting. We propose several concrete next steps to keep research moving toward detecting frailty with biomarker-based detection methods. 相似文献
49.
50.
Lukas Frank Anne Rademacher Norbert Mücke Stephan M Tirier Emma Koeleman Caroline Knotz Sabrina Schumacher Sabine
A Stainczyk Frank Westermann Stefan Frhling Priya Chudasama Karsten Rippe 《Nucleic acids research》2022,50(11):e61
Alternative lengthening of telomeres (ALT) occurs in ∼10% of cancer entities. However, little is known about the heterogeneity of ALT activity since robust ALT detection assays with high-throughput in situ readouts are lacking. Here, we introduce ALT-FISH, a method to quantitate ALT activity in single cells from the accumulation of single-stranded telomeric DNA and RNA. It involves a one-step fluorescent in situ hybridization approach followed by fluorescence microscopy imaging. Our method reliably identified ALT in cancer cell lines from different tumor entities and was validated in three established models of ALT induction and suppression. Furthermore, we successfully applied ALT-FISH to spatially resolve ALT activity in primary tissue sections from leiomyosarcoma and neuroblastoma tumors. Thus, our assay provides insights into the heterogeneity of ALT tumors and is suited for high-throughput applications, which will facilitate screening for ALT-specific drugs. 相似文献