全文获取类型
收费全文 | 1318篇 |
免费 | 85篇 |
国内免费 | 1篇 |
出版年
2023年 | 5篇 |
2022年 | 20篇 |
2021年 | 41篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 26篇 |
2017年 | 31篇 |
2016年 | 44篇 |
2015年 | 82篇 |
2014年 | 83篇 |
2013年 | 81篇 |
2012年 | 114篇 |
2011年 | 96篇 |
2010年 | 64篇 |
2009年 | 64篇 |
2008年 | 68篇 |
2007年 | 86篇 |
2006年 | 76篇 |
2005年 | 66篇 |
2004年 | 47篇 |
2003年 | 62篇 |
2002年 | 39篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有1404条查询结果,搜索用时 31 毫秒
41.
Ismail Eş Maycon Carvalho Ribeiro Samuel Rodrigues dos Santos Júnior Amin Mousavi Khaneghah Armando Garcia Rodriguez André Corrêa Amaral 《Bioprocess and biosystems engineering》2016,39(10):1487-1500
The whole-cell immobilization on chitosan matrix was evaluated. Bacillus sp., as producer of CGTase, was grown in solid-state and batch cultivation using three types of starches (cassava, potato and cornstarch). Biomass growth and substrate consumption were assessed by flow cytometry and modified phenol–sulfuric acid assays, respectively. Qualitative analysis of CGTase production was determined by colorless area formation on solid culture containing phenolphthalein. Scanning electron microscopy (SEM) analysis demonstrated that bacterial cells were immobilized on chitosan matrix efficiently. Free cells reached very high numbers during batch culture while immobilized cells maintained initial inoculum concentration. The maximum enzyme activity achieved by free cells was 58.15 U ml?1 (36 h), 47.50 U ml?1 (36 h) and 68.36 U ml?1 (36 h) on cassava, potato and cornstarch, respectively. CGTase activities for immobilized cells were 82.15 U ml?1 (18 h) on cassava, 79.17 U ml?1 (12 h) on potato and 55.37 U ml?1 (in 6 h and max 77.75 U ml?1 in 36 h) on cornstarch. Application of immobilization technique increased CGTase activity significantly. The immobilized cells produced CGTase with higher activity in a shorter fermentation time comparing to free cells. 相似文献
42.
Avi Z. Rosenberg Michael D. Armani Patricia A. Fetsch Liqiang Xi Tina Thu Pham Mark Raffeld Yun Chen Neil O’Flaherty Rebecca Stussman Adele R. Blackler Qiang Du Jeffrey C. Hanson Mark J. Roth Armando C. Filie Michael H. Roh Michael R. Emmert-Buck Jason D. Hipp Michael A. Tangrea 《PloS one》2016,11(3)
43.
44.
Ian W. Pray Dallas J. Swanson Viterbo Ayvar Claudio Muro Luz M. Moyano Armando E. Gonzalez Hector H. Garcia Seth E. O’Neal Cysticercosis Working Group in Peru 《PLoS neglected tropical diseases》2016,10(4)
Background
Taenia solium, a parasitic cestode that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. T. solium eggs are released into the environment through the stool of humans infected with an adult intestinal tapeworm (a condition called taeniasis), and cause cysticercosis when ingested by pigs or other humans. A control strategy to intervene within high-risk foci in endemic communities has been proposed as an alternative to mass antihelminthic treatment. In this ring strategy, antihelminthic treatment is targeted to humans and pigs residing within a 100 meter radius of a pig heavily-infected with cysticercosis. Our aim was to describe the roaming ranges of pigs in this region, and to evaluate whether the 100 meter radius rings encompass areas where risk factors for T. solium transmission, such as open human defecation and dense pig activity, are concentrated.Methodology/Principal Findings
In this study, we used Global Positioning System (GPS) devices to track pig roaming ranges in two rural villages of northern Peru. We selected 41 pigs from two villages to participate in a 48-hour tracking period. Additionally, we surveyed all households to record the locations of open human defecation areas. We found that pigs spent a median of 82.8% (IQR: 73.5, 94.4) of their time roaming within 100 meters of their homes. The size of home ranges varied significantly by pig age, and 93% of the total time spent interacting with open human defecation areas occurred within 100 meters of pig residences.Conclusions/Significance
These results indicate that 100 meter radius rings around heavily-infected pigs adequately capture the average pig’s roaming area (i.e., home range) and represent an area where the great majority of exposure to human feces occurs. 相似文献45.
Maude Schneider Marco Armando Maria Pontillo Stefano Vicari Martin Debbané Frauke Schultze‐Lutter Stephan Eliez 《World psychiatry》2016,15(3):259-265
The 22q11.2 deletion syndrome (22q11DS) is characterized by high rates of psychotic symptoms and schizophrenia, making this condition a promising human model for studying risk factors for psychosis. We explored the predictive value of ultra high risk (UHR) criteria in a sample of patients with 22q11DS. We also examined the additional contribution of socio‐demographic, clinical and cognitive variables to predict transition to psychosis within a mean interval of 32.5 ± 17.6 months after initial assessment. Eighty‐nine participants with 22q11DS (age range: 8‐30 years; mean 16.1 ± 4.7) were assessed using the Structured Interview for Psychosis‐Risk Syndromes. Information on Axis I diagnoses, internalizing and externalizing symptoms, level of functioning and IQ was also collected. At baseline, 22 (24.7%) participants met UHR criteria. Compared to those without a UHR condition, they had a significantly lower functioning, more frequent anxiety disorders, and more severe psychopathology. Transition rate to psychosis was 27.3% in UHR and 4.5% in non‐UHR participants. Cox regression analyses revealed that UHR status significantly predicted conversion to psychosis. Baseline level of functioning was the only other additional predictor. This is the first study investigating the predictive value of UHR criteria in 22q11DS. It indicates that the clinical path leading to psychosis is broadly comparable to that observed in other clinical high‐risk samples. Nevertheless, the relatively high transition rate in non‐UHR individuals suggests that other risk markers should be explored in this population. The role of low functioning as a predictor of transition to psychosis should also be investigated more in depth. 相似文献
46.
Ramos Patrícia A. B. Ferro Ana M. Oliveira M. Margarida Gonçalves Sónia Freire Carmen S. R. Silvestre Armando J. D. Duarte Maria F. 《Phytochemistry Reviews》2019,18(2):495-526
Phytochemistry Reviews - Cynara cardunculus health benefits have aroused much interest, leading to the discovery of valuable bioactive compounds with a crucial role in plant defence. Guaianolides... 相似文献
47.
48.
49.
Eugenio Llorens Or Sharon Gemma Camañes Pilar García-Agustín Amir Sharon 《Environmental microbiology》2019,21(9):3299-3312
Endophytes contribute to plant performance, especially under harsh conditions. We therefore hypothesized that wild plants have retained beneficial endophytes that are less abundant or not present in related crop plants. To test this hypothesis, we selected two endophytes that were found in Sharon goatgrass, an ancestor of wheat, and tested their effect on bread wheat. Both endophytes infected wheat and improved sustainability and performance under water-limited conditions. To determine how the endophytes modify plant development, we measured parameters of plant growth and physiological status and performed a comparative metabolomics analysis. Endophyte-treated wheat plants had reduced levels of stress damage markers and reduced accumulation of stress-adaptation metabolites. Metabolomics profiling revealed significant differences in the response to water stress of endophyte-treated plants compared with untreated plants. Our results demonstrate the potential of endophytes from wild plants for improvement of related crops and show that the beneficial effects of two endophytes are associated with alteration of physiological responses to water-limited conditions. 相似文献
50.
Armando Aguirre Mario Vallejo-Marín Lizandra Salazar-Goroztieta Dulce M. Arias Rodolfo Dirzo 《Biotropica》2007,39(1):79-86
Dioecy, the segregation of male and female structures among individuals, is widespread in tropical plants, encompassing 10–30 percent of species in some sites. In many cases, interindividual sex separation is not complete, as individual plants, although nominally dioecious, may produce both types of reproductive structures. A common form of this sexual variation is the production of female structures in otherwise male individuals, commonly referred to as fruiting males. Here we report the existence of fruiting males in the dioecious tropical tree Jacaratia mexicana (Caricaceae). We show that fruiting males can constitute up to 45 percent of all males in some populations of a tropical forest in Southern Mexico. In order to determine the functional significance of fruiting males for the breeding system of J. mexicana , we compared the relative performance of male- and female-borne seeds. Our results show that seeds from fruiting males are three times less likely to germinate and survive than seeds from female trees. Based on relative seed fitness data, and sex ratios in natural populations, we estimate that 6–15 percent of the genes contributed by fruiting males to the next generation are transmitted via ovules, meaning that morphological variation in gender is at least partially accompanied by functional gender variation. Finally, our seed fitness estimates for fruiting males suggest that fruiting males will not replace female plants in natural populations.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp . 相似文献
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp . 相似文献