全文获取类型
收费全文 | 1385篇 |
免费 | 93篇 |
国内免费 | 4篇 |
专业分类
1482篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 60篇 |
2021年 | 98篇 |
2020年 | 91篇 |
2019年 | 166篇 |
2018年 | 98篇 |
2017年 | 78篇 |
2016年 | 85篇 |
2015年 | 73篇 |
2014年 | 89篇 |
2013年 | 123篇 |
2012年 | 109篇 |
2011年 | 88篇 |
2010年 | 57篇 |
2009年 | 50篇 |
2008年 | 48篇 |
2007年 | 19篇 |
2006年 | 28篇 |
2005年 | 20篇 |
2004年 | 22篇 |
2003年 | 19篇 |
2002年 | 16篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1482条查询结果,搜索用时 15 毫秒
11.
Improvement of both lipid and biomass productivities of Qatar Chlorocystis isolate for biodiesel production and food security 下载免费PDF全文
Imen Saadaoui Touria Bounnit Maryam Muraikhi Rihab Rasheed Ghamza Alghasal Hareb Al Jabri 《Phycological Research》2018,66(3):182-188
Microalgae are considered a very promising alternative for biofuel production. Several strategies were developed to modulate and improve algae metabolites production to meet the requirements for biodiesel production. Most previous research evidenced that the increase of the lipid content is accompanied by a decrease of the biomass production, which increases the cost of the downstream processing. Hence, the challenge is to find special culture conditions that increase the lipid and the biomass productivities simultaneously. In the present work, we developed a strategy for the improvement of biomass and lipid productivities in a novel local microalga isolate, Chlorocystis sp. QUCCCM14, which was not previously known as a promising strain. Indeed, culturing QUCCCM14 using f/2 medium with 10× NaH2PO4 (0.15 g L?1 NaNO3 and 5.6 mg L?1 NaH2PO4) resulted in an improvement of 3.178 folds the lipid productivity reaching 56.121 mg L?1 day?1 and enhanced the biomass productivity reaching 141.363 mg L?1 day?1, simultaneously. Comparative analyses of the FAME profiles demonstrated that fed‐batch culture with phosphate or nitrate separately leads to a high production of the omega 3 fatty acids (Linolenic acid), whereas fed‐batch culture with phosphate and nitrate simultaneously increased the production of fatty acids suitable for biodiesel production. 相似文献
12.
Negin Parsamanesh Maryam Moossavi Tahmineh Tavakkoli Hossein Javdani Tahereh Fakharian Seyedeh Zahra Moossavi Mohsen Naseri 《Journal of cellular physiology》2019,234(9):15044-15047
Gastric cancer is the second cause of cancer-related mortality and the fourth most common cancers worldwide. Owing to the immune modulatory effect of vitamin D in the body, the role of vitamin D receptor gene in vitamin D regulation receives a great deal of research interest. The aim of the current study was to highlight the association between two variants of TaqI and FokI in the vitamin D receptor gene and gastric cancer predisposition in a sample of South Khorasan population. The present investigation consisted of 69 patients affected with gastric cancer and 100 healthy individuals. The genomic DNA was extracted by salting out the protocol from peripheral venous blood. Genotyping of TaqI and FokI variants were performed by PCR-RFLP method. Our findings manifested that TC genotype of TaqI polymorphism was statistically significant between the case and the control groups (p = 0.002). Moreover, the frequency of TC + CC genotypes was statistically significant between the two groups (p = 0.009). Furthermore, we could not find any meaningful association between FokI variant and the participant groups. The present results declared that, in our population, TC genotype of TaqI polymorphism has an association with gastric cancer susceptibility. In addition, more investigation with greater sample sizes is needed to confirm our results. 相似文献
13.
14.
Ansari-Lari M Saadat M Hadi N 《Biochemical and biophysical research communications》2003,312(2):299-302
Workers in the petroleum distribution trades experience relatively low-level exposures to gasoline vapors whose consequences have not been fully elucidated. The purpose of this study was to investigate changes in the hematological parameters among filling station workers who were occupationally exposed to gasoline. The target group for the study consisted of 41 workers from eight filling stations of Shiraz (south of Iran). The control group consisted of 27 healthy subjects matched for age and sex from general population. The complete blood count analysis was done in one laboratory. Using PCR-based method, the genotypes of glutathione S-transferase T1 (GSTT1) and M1 (GSTM1) were determined. Workers were divided into three exposure groups according to employment history: duration less than 1 year, 1-5 years, and more than 5 years. Comparison was performed using Kruskal-Wallis test. In the individuals with the presence of both GSTT1 and GSTM1 functional alleles, comparison between four exposure groups revealed no significant difference for studied hematological variables. There were statistically significant differences between study groups, with only one functional allele, either GSTT1 or GSTM1, for relative number of lymphocytes (chi(2)=9.147, df=3, P=0.027) and neutrophils (chi(2)=9.951, df=3, and P=0.019), and absolute number of lymphocytes (chi(2)=9.135, df=3, and P=0.028), and RBC (chi(2)=10.586, df=3, and P=0.014). These findings could indicate the possible protective effect of concurrent presence of GSTM1 and GSTT1 enzymes on the hematopoietic system of filling station workers. 相似文献
15.
Mohammad?E?ParsanezhadEmail author Saeed?Alborzi Jaleh?Zolghadril Maryam?Parsa-Nezhad Gholamreza?Keshavarzi Gholamhossein?R?Omrani Ernst?H?Schmidt 《Reproductive biology and endocrinology : RB&E》2005,3(1):31
Background
The effects of ovarian drilling on the serum levels of gonadotropins and androgens have been studied previously. The aim of this study is to evaluate the effects of ovarian drilling on the serum prolactin levels and its relation to ovulation in women with polycystic ovary syndrome. 相似文献16.
Maryam Nasr Esfahani Saad Sulieman Joachim Schulze Kazuko Yamaguchi‐Shinozaki Kazuo Shinozaki Lam‐Son Tran 《Plant biotechnology journal》2014,12(3):387-397
Chickpea (Cicer arietinum) is an important pulse crop in many countries in the world. The symbioses between chickpea and Mesorhizobia, which fix N2 inside the root nodules, are of particular importance for chickpea's productivity. With the aim of enhancing symbiotic efficiency in chickpea, we compared the symbiotic efficiency of C‐15, Ch‐191 and CP‐36 strains of Mesorhizobium ciceri in association with the local elite chickpea cultivar ‘Bivanij’ as well as studied the mechanism underlying the improvement of N2 fixation efficiency. Our data revealed that C‐15 strain manifested the most efficient N2 fixation in comparison with Ch‐191 or CP‐36. This finding was supported by higher plant productivity and expression levels of the nifHDK genes in C‐15 nodules. Nodule specific activity was significantly higher in C‐15 combination, partially as a result of higher electron allocation to N2 versus H+. Interestingly, a striking difference in nodule carbon and nitrogen composition was observed. Sucrose cleavage enzymes displayed comparatively lower activity in nodules established by either Ch‐191 or CP‐36. Organic acid formation, particularly that of malate, was remarkably higher in nodules induced by C‐15 strain. As a result, the best symbiotic efficiency observed with C‐15‐induced nodules was reflected in a higher concentration of the total and several major amino metabolites, namely asparagine, glutamine, glutamate and aspartate. Collectively, our findings demonstrated that the improved efficiency in chickpea symbiotic system, established with C‐15, was associated with the enhanced capacity of organic acid formation and the activities of the key enzymes connected to the nodule carbon and nitrogen metabolism. 相似文献
17.
High-risk types of human papillomaviruses (HPVs) are the etiological agents in nearly all cases (99.7%) of cervical cancer, and the HPV E6 protein is one of the two viral oncoproteins which is expressed in virtually all HPV-positive cancers. Therefore, classifying the risk type of HPVs is very useful and necessary for diagnosis and remedy of cervical cancer. To predict and to classify the risk types of HPV by bioinformatics analysis, 96 E6 protein sequences from available databases were obtained. To investigate the risk type of these sequences, PseAAC server, ROC curves and statistical analysis were applied. Our classification was based on some characters of HPV E6 proteins, such as hydrophobicity, hydrophilicity, side chain mass, PK of the α-COOH group, PK of the α-NH3+ group and PI at 25 °C. Risk type of 4 unknown HPV types and 25 non-reported HPV types were also predicted. These results show that bioinformatics based theoretical approaches can direct and simplify experimental studies. 相似文献
18.
Evidence for evolutionary constraints in <Emphasis Type="Italic">Drosophila</Emphasis> metal biology
Mutations in single Drosophila melanogaster genes can alter total body metal accumulation. We therefore asked whether evolutionary constraints maintain biologically
abundant metal ions (iron, copper, manganese and zinc) to similar concentrations in different species of Drosophilidae, or
whether metal homeostasis is a highly adaptable trait as shown previously for triglyceride and glycogen storage. To avoid
dietary influences, only species able to grow and reproduce on a standard laboratory medium were selected for analysis. Flame
atomic absorption spectrometry was used to determine metal content in 5-days-old adult flies. Overall, the data suggest that
the metallome of the nine species tested is well conserved. Meaningful average values for the Drosophilidae family are presented.
Few statistically significant differences were noted for copper, manganese and zinc between species. In contrast, Drosophila erecta and Drosophila virilis showed a 50% increase above average and a 30% decrease below average in iron concentrations, respectively. The changes in
total body iron content correlated with altered iron storage in intestinal ferritin stores of these species. Hence, the variability
in iron content could be accounted for by a corresponding adaptation in iron storage regulation. We suggest that the relative
expression of the multitude of metalloenzymes and other metal-binding proteins remains overall similar between species and
likely determines relative metal abundances in the organism. The availability of a complete and annotated genome sequence
of different Drosophila species presents opportunities to study the evolution of metal homeostasis in closely related organisms that have evolved
separately for millions or dozens of million years. 相似文献
19.
Martine de Boer Maaike te Lintel Hekkert Jiang Chang Bibi S. van Thiel Leonie Martens Maxime M. Bos Marion G. J. de Kleijnen Yanto Ridwan Yanti Octavia Elza D. van Deel Lau A. Blonden Renata M. C. Brandt Sander Barnhoorn Paula K. Bautista-Niño Ilona Krabbendam-Peters Rianne Wolswinkel Banafsheh Arshi Mohsen Ghanbari Christian Kupatt Leon J. de Windt A. H. Jan Danser Ingrid van der Pluijm Carol Ann Remme Monika Stoll Joris Pothof Anton J. M. Roks Maryam Kavousi Jeroen Essers Jolanda van der Velden Jan H. J. Hoeijmakers Dirk J. Duncker 《Aging cell》2023,22(3):e13768
20.
Aghamohamadi Elham Asri † Nastaran Odak Aylin Rostami-Nejad Mohammad Chaleshi Vahid Hajinabi Yasaman Eslami Maryam Mohammadian Haftcheshmeh Saeed Gholam-Mostafaei Fahimeh Sadat Asadzadeh-Aghdaei Hamid Masotti Andrea Zali Mohammad Reza 《Molecular biology reports》2022,49(7):6085-6091
Molecular Biology Reports - Celiac disease (CeD) and inflammatory bowel disease (IBD) are accompanied by impaired immune responses. To study the immune regulation of these diseases, we evaluated... 相似文献