全文获取类型
收费全文 | 3968篇 |
免费 | 302篇 |
专业分类
4270篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 82篇 |
2021年 | 142篇 |
2020年 | 71篇 |
2019年 | 105篇 |
2018年 | 148篇 |
2017年 | 135篇 |
2016年 | 192篇 |
2015年 | 240篇 |
2014年 | 262篇 |
2013年 | 285篇 |
2012年 | 340篇 |
2011年 | 337篇 |
2010年 | 196篇 |
2009年 | 146篇 |
2008年 | 244篇 |
2007年 | 234篇 |
2006年 | 194篇 |
2005年 | 170篇 |
2004年 | 153篇 |
2003年 | 123篇 |
2002年 | 117篇 |
2001年 | 34篇 |
2000年 | 29篇 |
1999年 | 32篇 |
1998年 | 33篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1961年 | 3篇 |
排序方式: 共有4270条查询结果,搜索用时 0 毫秒
101.
Lucas Gomes Sapienza Michael Jenwei Chen Maria José Leite Gomes David B. Mansur 《Reports of Practical Oncology and Radiotherapy》2016,21(1):25-30
Aim
To evaluate the unintentional coverage of the internal mammary chain (IMC) with tangential fields irradiation to the breast, and its relation with the type of surgery employed.Background
The dose distribution in regions adjacent to the treatment targets (mammary gland or chest wall), with incidental irradiation of the IMC, could translate into clinical benefit, due to the proximity of these regions.Materials and methods
One hundred and twelve consecutive conformal radiotherapy plans were correlating the average dose to the IMC with the type of surgery employed, the extent of disease and the irradiation techniques.Results
The mean doses to IMC after modified radical mastectomy (MRM), modified radical mastectomy with immediate reconstruction (MRM + R), and breast conservative surgery (BCS) were 30.34 Gy, 30.26 Gy, and 18.67 Gy, respectively. Significant differences were identified between patients who underwent MRM or MRM + R over BCS (p = 0.01 and 0.003, respectively), but not between MRM and MRM + R (p = 0.88). Mean doses to IMC were greater in patients with T3–T4 tumors when compared with more initial stages (≤T2) (p = 0.0096). The lymph node involvement also correlated with higher average doses to IMC (node positive: 26.1 Gy × node negative: 17.8 Gy, p = 0.0017).Conclusions
The moderate dose level to the IMC in the unintentional irradiation scenario seems to be insufficient to treat the subclinical disease, although it could have an impact in patients undergoing mastectomy. 相似文献102.
Gustavo A. Santa Cruz 《Reports of Practical Oncology and Radiotherapy》2016,21(2):135-139
Aim
to present the most important aspects of Microdosimetry, a research field in radiation biophysics.Background
microdosimetry is the branch of radiation biophysics that systematically studies the spatial, temporal and spectral aspects of the stochastic nature of the energy deposition processes in microscopic structures.Materials and Methods
we briefly review its history, the people, the formalism and the theories and devices that allowed researchers to begin to understand the true nature of radiation action on living matter.Results and Conclusions
we outline some of its applications, especially to Boron Neutron Capture Therapy, attempting to explain the biological effectiveness of the boron thermal neutron capture reaction. 相似文献103.
104.
105.
Alejandro Prado Ángel Gaitán Mario Leonor Marta Manzano Eduardo Cabello Raúl Díaz Alejandro Ferrando Ana Milanés Gustavo Pozo 《Reports of Practical Oncology and Radiotherapy》2019,24(2):227-232
AimTo assess the performance of the monitor unit (MU) Objective tool in Eclipse treatment planning system (TPS) utilizing volumetric modulated arc therapy (VMAT) for rectal cancer.BackgroundEclipse VMAT planning module includes a tool to control the number of MUs delivered: the MU Objective tool. This tool could be utilized to reduce the total number of MUs in rectal cancer treatments.Materials and methods20 rectal cancer patients were retrospectively studied using VMAT and the MU Objective tool. The baseline plan for each patient was selected as the one with no usage of the MU Objective tool. The number of MUs of this plan was set to be the reference number of MUs (MUref). Five plans were re-optimized for each patient only varying the Max MU parameter. The selected values were 30%, 60%, 90%, 120% and 150% of MUref for each patient. Differences with respect to the baseline plan were evaluated regarding MU number and parameters for PTVs coverage evaluation, PTVs homogeneity and OARs doses assessment. A two-tailed, paired-samples t-test was used to quantify these differences.ResultsAverage relative differences in MU number obtained was 10% for Max MU values of 30% and 60% of MUref, respectively (p < 0.03). PTVs coverage and homogeneity were not compromised and discrepancies obtained with respect to baseline plans were not significant. Furthermore, maximum OARs doses deviations were also not significant.ConclusionsA 10% reduction in the MU number could be obtained without an alteration of PTV coverage and OARs doses for rectal cancer. 相似文献
106.
107.
Amin Soltangheisi Paul J. A. Withers Paulo Sergio Pavinato Maurício Roberto Cherubin Raffaella Rossetto Janaina Braga Do Carmo Gustavo Casoni da Rocha Luiz Antonio Martinelli 《Global Change Biology Bioenergy》2019,11(12):1444-1455
Phosphorus (P) use in global food and bioenergy production needs to become more efficient and sustainable to reduce environmental impacts and conserve a finite and critical resource (Carpenter & Bennett, Environmental Research Letters, 2011, 6, 014009; Springmann et al., Nature, 2018, 562, 519). Sugarcane is one crop with a large P footprint because production is centered on P‐fixing soils with low P availability (Roy et al., Nature Plants, 2016, 2, 16043; Withers et al., Scientific Reports, 2018, 8, 2537). As global demand for processed sugar and bioethanol continues to increase, we advocate that improving P efficiency could become a key sustainability goal for the sugarcane industry. Here, we applied the 5R global P stewardship framework (Withers et al., Ambio, 2015, 44, 193) to identify more sustainable options to manage P in Brazilian sugarcane production. We show that current inputs of P fertilizer to the current crop area could be reduced by over 305 Gg, or 63%, over the next three decades by reducing unnecessary P fertilizer use, better utilization of recyclable bioresources and redesigning recommendation systems. Adoption of these 5R options would save the sugarcane industry in Brazil 528 US$ million and help safeguard global food and energy security. 相似文献
108.
Llis A. Carlos‐Júnior Matthew Spencer Danilo Mesquita Neves Timothy Peter Moulton Dbora de Oliveira Pires Clovis Barreira e Castro Carlos Renato Rezende Ventura Carlos Eduardo Leite Ferreira Cristiana Silveira Serejo Simone Oigman‐Pszczol Fernanda Araújo Casares Marcelo Checoli Mantelatto Joel Christopher Creed 《Diversity & distributions》2019,25(5):743-757
109.
Jilmar A. Murillo Juan F. Gil Yulieth A. Upegui Adriana M. Restrepo Sara M. Robledo Winston Quiñones Fernando Echeverri Aurelio San Martin Horacio F. Olivo Gustavo Escobar 《Bioorganic & medicinal chemistry》2019,27(1):153-160
We describe the in vitro activity of two natural isomeric ent-beyerene diterpenes, several derivatives and synthetic intermediates. Beyerenols 1 and 2 showed EC50 of 4.6?±?9.4 and 5.3?±?9.4?μg/mL against amastigotes of L. (V) brazilensis, with SI of 5.1 and 7.7, respectively. Beyerenol 1 was synthesized from stevioside. In vivo experiments with bereyenols showed cure in 50% of hamsters infected with L. (V) brazilensis topically applied as Cream I (beyerenol 1, 0.81%, w/w) and Cream III (beyerenol 2, 1.96%, w/w). These results suggest that beyerenols are potential candidates for cutaneous leishmaniasis chemotherapy by topical application. In vitro assays of amastigotes of L. (V) brazilensis showed EC50 of 1.1?±?0.1 and 1.3?±?0.04?μg/mL, with SI of 3.1 and 3.5 for hydrazone intermediates 10 and 11, respectively. 相似文献
110.
Genaro C. Miranda-de la Lama Laura X. Estévez-Moreno Morris Villarroel Adolfo A. Rayas-Amor Gustavo A. María Wilmer S. Sepúlveda 《Journal of applied animal welfare science : JAAWS》2019,22(1):13-25
The study aim was to identify consumer segmentation based on nonhuman animal welfare (AW) attitudes and their relationship with demographic features and willingness to pay (WTP) for welfare-friendly products (WFP) in Mexico. Personal interviews were conducted with 843 Mexican consumers who stated they purchased most of the animal products in their home. Respondents were selected using a quota sampling method with age, gender, education, and origin as quota control variables. The multivariate analysis suggested there were three clusters or consumer profiles labeled “skeptical,” “concerned,” and “ethical,” which helped explain the association between AW attitudes, some demographic variables, and WTP for WFP. This study is one of the first to address consumer profiling in Latin America, and the findings could have implications for the commercialization of WFP. Hence, customers should receive information to consider welfare innovations when deciding to purchase animal products. The growth of the WFP food market establishes an element of a far more multifaceted phenomenon of sustainable consumption and support of a new paradigm called responsible marketing in emerging markets such as Mexico. 相似文献