全文获取类型
收费全文 | 1436篇 |
免费 | 66篇 |
出版年
2023年 | 13篇 |
2022年 | 15篇 |
2021年 | 29篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 39篇 |
2017年 | 32篇 |
2016年 | 28篇 |
2015年 | 60篇 |
2014年 | 71篇 |
2013年 | 87篇 |
2012年 | 117篇 |
2011年 | 82篇 |
2010年 | 64篇 |
2009年 | 66篇 |
2008年 | 87篇 |
2007年 | 57篇 |
2006年 | 66篇 |
2005年 | 67篇 |
2004年 | 51篇 |
2003年 | 48篇 |
2002年 | 45篇 |
2001年 | 31篇 |
2000年 | 31篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有1502条查询结果,搜索用时 15 毫秒
51.
Ashish Deep Gupta Vipin Kumar Bansal Vikash Babu Nishi Maithil 《Journal of Genetic Engineering and Biotechnology》2013,11(1):25-31
Antioxidant and antimicrobial activities of nutmeg (Myristica fragrans Houtt) seed extracts were evaluated. Seeds were extracted with acetone, ethanol, methanol, butanol and water. All the extracts have shown significant antioxidant and antimicrobial activities against the tested microorganisms. Among all extracts, acetone extract has shown the highest antioxidant activity. The acetone extract showed 93.12 ± 1.48 mg gallic acid equivalents (GAE)/100 g dry weight total phenolic content, DPPH scavenging activity of 63.04 ± 1.56%, chelating activity of 64.11 ± 2.21% and 74.36 ± 1.94% inhibition of β-carotene bleaching, at 1 mg/mL extract concentration. Out of all extracts, acetone extract was able to exert antimicrobial activity against all tested bacteria and fungi. Acetone extract has shown the strongest antibacterial and antifungal activity with Staphylococcus aureus (13.8 ± 0.42 mm) and Aspergillus niger (14.4 ± 0.37 mm), respectively. GC–MS analysis of acetone extract has revealed the presence of 32 compounds of extract representing 99.49%. Sabinene (28.61%) has shown the highest occurrence in the extract. β-Pinene (10.26), α-pinene (9.72), myristicin (4.30%), isoeugenol (2.72%), p-cymene (1.81%), carvacrol (1.54%), eugenol (0.89%) and β-caryophellene (0.82%) were reported as possible contributor for antioxidant and antimicrobial activity of nutmeg. 相似文献
52.
Hexagonal Boron Nitride‐Based Electrolyte Composite for Li‐Ion Battery Operation from Room Temperature to 150 °C 下载免费PDF全文
Marco‐Tulio F. Rodrigues Kaushik Kalaga Hemtej Gullapalli Ganguli Babu Arava Leela Mohana Reddy Pulickel M. Ajayan 《Liver Transplantation》2016,6(12)
Batteries for high temperature applications capable of withstanding over 60 °C are still dominated by primary cells. Conventional rechargeable energy storage technologies which have exceptional performance at ambient temperatures employ volatile electrolytes and soft separators, resulting in catastrophic failure under heat. A composite electrolyte/separator is reported that holds the key to extend the capability of Li‐ion batteries to high temperatures. A stoichiometric mixture of hexagonal boron nitride, piperidinium‐based ionic liquid, and a lithium salt is formulated, with ionic conductivity reaching 3 mS cm?1, electrochemical stability up to 5 V and extended thermal stability. The composite is used in combination with conventional electrodes and demonstrates to be stable for over 600 cycles at 120 °C, with a total capacity fade of less than 3%. The ease of formulation along with superior thermal and electrochemical stability of this system extends the use of Li‐ion chemistries to applications beyond consumer electronics and electric vehicles. 相似文献
53.
Achyut Aryal Uttam Babu Shrestha Weihong Ji Som B. Ale Sujata Shrestha Tenzing Ingty Tek Maraseni Geoff Cockfield David Raubenheimer 《Ecology and evolution》2016,6(12):4065-4075
Future climate change is likely to affect distributions of species, disrupt biotic interactions, and cause spatial incongruity of predator–prey habitats. Understanding the impacts of future climate change on species distribution will help in the formulation of conservation policies to reduce the risks of future biodiversity losses. Using a species distribution modeling approach by MaxEnt, we modeled current and future distributions of snow leopard (Panthera uncia) and its common prey, blue sheep (Pseudois nayaur), and observed the changes in niche overlap in the Nepal Himalaya. Annual mean temperature is the major climatic factor responsible for the snow leopard and blue sheep distributions in the energy‐deficient environments of high altitudes. Currently, about 15.32% and 15.93% area of the Nepal Himalaya are suitable for snow leopard and blue sheep habitats, respectively. The bioclimatic models show that the current suitable habitats of both snow leopard and blue sheep will be reduced under future climate change. The predicted suitable habitat of the snow leopard is decreased when blue sheep habitats is incorporated in the model. Our climate‐only model shows that only 11.64% (17,190 km2) area of Nepal is suitable for the snow leopard under current climate and the suitable habitat reduces to 5,435 km2 (reduced by 24.02%) after incorporating the predicted distribution of blue sheep. The predicted distribution of snow leopard reduces by 14.57% in 2030 and by 21.57% in 2050 when the predicted distribution of blue sheep is included as compared to 1.98% reduction in 2030 and 3.80% reduction in 2050 based on the climate‐only model. It is predicted that future climate may alter the predator–prey spatial interaction inducing a lower degree of overlap and a higher degree of mismatch between snow leopard and blue sheep niches. This suggests increased energetic costs of finding preferred prey for snow leopards – a species already facing energetic constraints due to the limited dietary resources in its alpine habitat. Our findings provide valuable information for extension of protected areas in future. 相似文献
54.
Rajamanickam Anuradha Saravanan Munisankar Yukthi Bhootra Jeeva Jagannathan Chandrakumar Dolla Paul Kumaran Thomas B. Nutman Subash Babu 《PLoS neglected tropical diseases》2016,10(1)
Background
Th9 cells are a subset of CD4+ T cells that express the protoypical cytokine, IL-9. Th9 cells are known to effect protective immunity in animal models of intestinal helminth infections. However, the role of Th9 cells in human intestinal helminth infections has never been examined.Methodology
To examine the role of Th9 cells in Strongyloidis stercoralis (Ss), a common intestinal helminth infection, we compared the frequency of Th9 expressing IL-9 either singly (mono-functional) or co-expressing IL-4 or IL-10 (dual-functional) in Ss-infected individuals (INF) to frequencies in uninfected (UN) individuals.Principal Findings
INF individuals exhibited a significant increase in the spontaneously expressed and/or antigen specific frequencies of both mono- and dual-functional Th9 cells as well as Th2 cells expressing IL-9 compared to UN. The differences in Th9 induction between INF and UN individuals was predominantly antigen-specific as the differences were no longer seen following control antigen or mitogen stimulation. In addition, the increased frequency of Th9 cells in response to parasite antigens was dependent on IL-10 and TGFx since neutralization of either of these cytokines resulted in diminished Th9 frequencies. Finally, following successful treatment of Ss infection, the frequencies of antigen-specific Th9 cells diminished in INF individuals, suggesting a role for the Th9 response in active Ss infection. Moreover, IL-9 levels in whole blood culture supernatants following Ss antigen stimulation were higher in INF compared to UN individuals.Conclusion
Thus, Ss infection is characterized by an IL-10- and TGFβ dependent expansion of Th9 cells, an expansion found to reversible by anti-helmintic treatment. 相似文献55.
Pandey Shiv S. Singh Sucheta Babu C. S. Vivek Shanker Karuna Srivastava N. K. Kalra Alok 《Planta》2016,243(5):1097-1114
Planta - Endophytes reside in different parts of the poppy plant and perform the tissue-specific functions. Most leaf endophytes modulate photosynthetic efficiency, plant growth, and productivity... 相似文献
56.
Duc Khanh Le Quang Khai Le Thi Thuy Hang Tran Duc Viet Nguyen Thi Hang Dao Thi Thuy Nguyen Xuan Lam Truong Quang Cuong Nguyen Huy Phong Pham Thi Thu Thuy Phan Gajendra Babu Baktavachalam 《Journal of Asia》2019,22(2):493-498
Susceptibility of Asian corn borer (ACB), Ostrinia furnacalis (Guenée) to Bacillus thuringiensis (Bt) Cry1Ab protein was studied between 2015 and 2016 with 11 ACB populations, collected from various geographical regions in Vietnam. A concentration range of Cry1Ab from 0.20 to 26.10 ng/cm2 of diet was evaluated against F1 ACB neonates using diet surface-overlay bioassays. Mortality data was recorded daily until seven days after infestation. Growth inhibition was recorded at the end of seven days. The median lethal concentration (LC50) varied ≈3-fold among the different populations, ranging from 0.58 to 1.83 ng/cm2 of diet with an overall mean of 0.86 ng/cm2 of diet. Even the lowest concentration of 0.20 ng/cm2 caused 73.53% growth inhibition. >90% growth inhibition was achieved at 0.82 ng/cm2 or higher concentrations. The results reflect natural variation in Bt susceptibility among ACB populations rather than variation caused by prior exposure to selection pressures. LC99 value (17.26 ng/cm2) was generated by pooling mortality data across different populations. The upper fiducial limit of LC99 (24.38 ng/cm2) could be a potential diagnostic dose for future resistance monitoring programs. The findings from this study suggest that ACB populations in Vietnam are highly susceptible to Cry1Ab protein. This is the first report of Cry1Ab susceptibility of different ACB populations in Vietnam and will serve as a baseline for future resistance monitoring work. 相似文献
57.
The 26S proteasome is a multi‐catalytic ATP‐dependent protease complex that recognizes and cleaves damaged or misfolded proteins to maintain cellular homeostasis. The 26S subunit consists of 20S core and 19S regulatory particles. 20S core particle consists of a stack of heptameric alpha and beta subunits. To elucidate the structure‐function relationship, we have dissected protein‐protein interfaces of 20S core particle and analyzed structural and physiochemical properties of intra‐alpha, intra‐beta, inter‐beta, and alpha‐beta interfaces. Furthermore, we have studied the evolutionary conservation of 20S core particle. We find the size of intra‐alpha interfaces is significantly larger and is more hydrophobic compared with other interfaces. Inter‐beta interfaces are well packed, more polar, and have higher salt‐bridge density than other interfaces. In proteasome assembly, residues in beta subunits are better conserved than alpha subunits, while multi‐interface residues are the most conserved. Among all the residues at the interfaces of both alpha and beta subunits, Gly is highly conserved. The largest size of intra‐alpha interfaces complies with the hypothesis that large interfaces form first during the 20S assembly. The tight packing of inter‐beta interfaces makes the core particle impenetrable from outer wall of the cylinder. Comparing the three domains, eukaryotes have large and well‐packed interfaces followed by archaea and bacteria. Our findings provide a structural basis of assembly of 20S core particle in all the three domains of life. 相似文献
58.
The discovery of nucleotide diversity captured as single feature polymorphism (SFP) by using the expression array is a high-throughput and effective method in detecting genome-wide polymorphism. The efficacy of such method was tested in rice, and the results presented in the paper indicate high sensitivity in predicting SFP. The sensitivity of polymorphism detection was further demonstrated by the fact that no biasness was observed in detecting SFP with either single or multiple nucleotide polymorphisms. The high density SFP data that can be generated quite effectively by the current method has promise for high resolution genetic mapping studies, as physical location of features are well-defined on rice genome. 相似文献
59.
G. Sriram T. R. Ganesh Babu R. Praveena J. V. Anand 《Molecular & cellular biomechanics : MCB》2022,19(1):29-40
Leukemoid reaction like leukemia indicates noticeable increased count of WBCs (White Blood Cells) but the cause of it is due to severe inflammation or infections in other body regions. In automatic diagnosis in classifying leukemia and leukemoid reactions, ALL IDB2 (Acute Lymphoblastic Leukemia-Image Data Base) dataset has been used which comprises 110 training images of blast cells and healthy cells. This paper aimed at an automatic process to distinguish leukemia and leukemoid reactions from blood smear images using Machine Learning. Initially, automatic detection and counting of WBC is done to identify leukocytosis and then an automatic detection of WBC blasts is performed to support classification of leukemia and leukemoid reactions. Leukocytosis is commonly observed both in leukemia and leukemoid hence physicians may have chance of wrong diagnosis of malignant leukemia for the patients with leukemoid reactions. BCCD (blood cell count detection) Dataset has been used which has 364 blood smear images of which 349 are of single WBC type. The Image segmentation algorithm of Hue Saturation Value color based on watershed has been applied. VGG16 (Visual Geometric Group) CNN (Convolution Neural Network) architecture based deep learning technique is being incorporated for classification and counting WBC type from segmented images. The VGG16 architecture based CNN used for classification and segmented images obtained from first part were tested to identify WBC blasts. 相似文献
60.