全文获取类型
收费全文 | 1461篇 |
免费 | 105篇 |
国内免费 | 64篇 |
出版年
2024年 | 3篇 |
2023年 | 51篇 |
2022年 | 32篇 |
2021年 | 62篇 |
2020年 | 49篇 |
2019年 | 45篇 |
2018年 | 90篇 |
2017年 | 87篇 |
2016年 | 113篇 |
2015年 | 76篇 |
2014年 | 108篇 |
2013年 | 160篇 |
2012年 | 118篇 |
2011年 | 134篇 |
2010年 | 94篇 |
2009年 | 92篇 |
2008年 | 38篇 |
2007年 | 20篇 |
2006年 | 28篇 |
2005年 | 8篇 |
2004年 | 29篇 |
2003年 | 31篇 |
2002年 | 48篇 |
2001年 | 41篇 |
2000年 | 29篇 |
1999年 | 13篇 |
1998年 | 3篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1630条查询结果,搜索用时 540 毫秒
51.
Yavuz Bülent Köse Gökalp İşcan Fatih Göger Gülşen Akalın Betül Demirci Kemal Hüsnü Can Başer 《化学与生物多样性》2016,13(10):1369-1379
The genus Centaurea L. is one of the largest and important genera of Asteraceae family. Centaurea species have been widely used as herbal remedies in folk medicine for their antidandruff, antidiarrheic, antirheumatic, anti‐inflammatory, choleretic, diuretic, digestive, stomachic, astringent, antipyretic, cytotoxic, and antibacterial properties. Centaurea baseri Kose & Alan is a recently described local endemic species in Turkey and this is the first study on the chemical composition and bioactivity of its hydrodistilled essential oil and the crude extract. According to chromatospectral analysis, hexadecanoic acid (42.3%), nonacosane (8.2%), and heptacosane (8.0%) were the main compounds of the essential oil, while 16 compounds were determined in the MeOH extract using LC/MS. Furthermore, antimicrobial, antioxidant, and cytotoxic effects of the essential oil and the extract were evaluated in comparison with the standard agents. The extract showed strong antifungal effect against Candida utilis at the concentration of 60 μg/ml (MIC) where the EO showed growth inhibition at the concentration of 47.00 μg/ml (MIC) against pathogen Bacillus cereus. Both the essential oil and the extract did not show any selective antioxidant properties. The extract showed remarkably selective cytotoxic properties against MCF‐7, PANC‐1, A549, and C6 glioma cells. 相似文献
52.
Effects of oxygen transfer on recombinant protein production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter were investigated. Recombinant glucose isomerase was chosen as the model protein. Two groups of oxygen transfer strategies were applied, one of which was based on constant oxygen transfer rate where aeration rate was Q O/V = 3 and 10 vvm, and agitation rate was N = 900 min?1; while the other one was based on constant dissolved oxygen concentrations, C DO = 5, 10, 15, 20 and 40 % in the fermentation broth, by using predetermined exponential glucose feeding with μ o = 0.15 h?1. The highest cell concentration was obtained as 44 g L?1 at t = 9 h of the glucose fed-batch phase at C DO = 20 % operation while the highest volumetric and specific enzyme activities were obtained as 4440 U L?1 and 126 U g?1 cell, respectively at C DO = 15 % operation. Investigation of specific enzyme activities revealed that keeping C DO at 15 % was more advantageous with an expense of relatively higher by-product formation and lower specific cell growth rate. For this strategy, the highest oxygen transfer coefficient and oxygen uptake rate were K L a = 0.045 s?1 and OUR = 8.91 mmol m?3 s?1, respectively. 相似文献
53.
Bengi Semerci Sarper Taskıran Evren Tufan Işın Şanlı 《Attention deficit and hyperactivity disorders》2016,8(3):139-147
This study aimed to elicit patient- and treatment-related factors that can potentially predict treatment adherence in adult ADHD. Subjects who were over 18 and received a diagnosis of ADHD were included in the study. Chart review data of 102 subjects regarding demographics, medications, comorbidities, concomitant medications and domains of functional impairment were collected, and predictors were assessed using a binominal logistical regression model. One hundred and two patients (78.4 % male) with a mean age of 28.8 (SD = 9.8, range = 18–55) years were enrolled in the study. Childhood diagnosis of ADHD, agents used for treatment (MPH or atomoxetine), individual domains of dysfunction and use of additional psychotropic drugs were not found to be related to treatment adherence. Patients with a university education and those referred for family history of ADHD were more likely to adhere to treatment (p = 0.05 and 0.03, respectively). On the other hand, reasons for referral other than ADHD were significantly more frequently related to non-adherence (p = 0.02). Treatment noncompliance remains a significant problem despite therapeutic effects of medications. Identification of predictors of non-adherence can lead to heightened awareness of special populations at risk. We have found that prior awareness on ADHD (via past history/media/friends) leading to self/clinician referral to rule out ADHD and pervasiveness of symptoms across functional domains led to better compliance in our sample. Future research with prospective design utilizing objective tools for adherence is required. 相似文献
54.
Anna Myná?ová Ivona Foitová Martin Kvá? Dana Květoňová Michael Rost Helen Morrogh-Bernard Wisnu Nurcahyo Cathleen Nguyen Supriyadi Supriyadi Bohumil Sak 《PloS one》2016,11(3)
Background
Orangutans are critically endangered primarily due to loss and fragmentation of their natural habitat. This could bring them into closer contact with humans and increase the risk of zoonotic pathogen transmission.Aims
To describe the prevalence and diversity of Cryptosporidium spp., microsporidia and Giardia intestinalis in orangutans at seven sites on Sumatra and Kalimantan, and to evaluate the impact of orangutans’ habituation and location on the occurrence of these zoonotic protists.Result
The overall prevalence of parasites in 298 examined animals was 11.1%. The most prevalent microsporidia was Encephalitozoon cuniculi genotype II, found in 21 animals (7.0%). Enterocytozoon bieneusi genotype D (n = 5) and novel genotype Pongo 2 were detected only in six individuals (2.0%). To the best of our knowledge, this is the first report of these parasites in orangutans. Eight animals were positive for Cryptosporidium spp. (2.7%), including C. parvum (n = 2) and C. muris (n = 6). Giardia intestinalis assemblage B, subtype MB6, was identified in a single individual. While no significant differences between the different human contact level groups (p = 0.479–0.670) or between the different islands (p = 0.992) were reported in case of E. bieneusi or E. cuniculi, Cryptosporidium spp. was significantly less frequently detected in wild individuals (p < 2×10−16) and was significantly more prevalent in orangutans on Kalimantan than on Sumatra (p < 2×10−16).Conclusion
Our results revealed that wild orangutans are significantly less frequently infected by Cryptosporidium spp. than captive and semi-wild animals. In addition, this parasite was more frequently detected at localities on Kalimantan. In contrast, we did not detect any significant difference in the prevalence of microsporidia between the studied groups of animals. The sources and transmission modes of infections were not determined, as this would require repeated sampling of individuals, examination of water sources, and sampling of humans and animals sharing the habitat with orangutans. 相似文献55.
56.
57.
58.
59.
60.
The effects of different cycles of starvation and re‐feeding on growth and body composition in rainbow trout (Oncorhynchus mykiss,Walbaum, 1792) 下载免费PDF全文
O. Taşbozan Y. Emre M. A. Gökçe C. Erbaş F. Özcan E. Kıvrak 《Zeitschrift fur angewandte Ichthyologie》2016,32(3):583-588
This study was designed to investigate the effects of starvation and re‐feeding cycles on the growth performance and body chemical composition of Oncorhynchus mykiss juveniles. A total of 360 juveniles with initial mean weights (IW) of 8.46 ± 0.07 g (n = 360) were stocked into 400‐L tanks in triplicate for each group, with 30 juveniles per tanks. The control group received regular feed, as is the common practice. The three other groups were periodically starved: 1 day starvation followed by 6 days re‐feeding (S1), 2 days starvation followed by 5 days re‐feeding (S2) and 3 days starvation followed by 4 days re‐feeding (S3). The experiment lasted for 10 weeks, over the course of which the water flow rate was 4 L min?1 and the water quality parameters determined as: temperature 14.4 ± 1.1°C, oxygen 8.2 ± 0.4 mg L?1 and pH 7.5 ± 0.2. At the end of the study, S1 had the best growth performance (final weight, specific growth rate, average daily growth) of all test groups (P < 0.05). The lowest daily feed intake (DFI) and growth performance parameters were observed in S3 (P < 0.05), while protein efficiency ratio (PER), net protein utilization (NPU) and lipid efficiency ratio (LER) were higher in the S3 fish group than in the other groups (P < 0.05). Whole body protein and lipid contents were highest in S1 fish. The hepatosomatic index (HSI) and viscerosomatic index (VSI) were significantly different among groups (P < 0.05). Feed conversion ratio (FCR) was significantly lower in starvation groups S1, S2 and S3 than in the control (P < 0.05). Compensation coefficient (CC) values were higher than 1 in all starvation groups. The concluding indicate that rainbow trout exposed to 1 and 2 days of starvation in week cycles could achieve over compensation compared to the control. Additionally, partial growth compensation and improved feed utilization could be achieved in a starvation group within 3 days in a week, by beginning with the juvenile size over a 10‐week experimental period. 相似文献