全文获取类型
收费全文 | 6762篇 |
免费 | 476篇 |
出版年
2023年 | 40篇 |
2022年 | 77篇 |
2021年 | 159篇 |
2020年 | 113篇 |
2019年 | 153篇 |
2018年 | 180篇 |
2017年 | 149篇 |
2016年 | 223篇 |
2015年 | 319篇 |
2014年 | 343篇 |
2013年 | 496篇 |
2012年 | 593篇 |
2011年 | 526篇 |
2010年 | 313篇 |
2009年 | 283篇 |
2008年 | 426篇 |
2007年 | 392篇 |
2006年 | 392篇 |
2005年 | 336篇 |
2004年 | 319篇 |
2003年 | 286篇 |
2002年 | 238篇 |
2001年 | 91篇 |
2000年 | 56篇 |
1999年 | 61篇 |
1998年 | 68篇 |
1997年 | 47篇 |
1996年 | 64篇 |
1995年 | 40篇 |
1994年 | 31篇 |
1993年 | 32篇 |
1992年 | 36篇 |
1991年 | 36篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有7238条查询结果,搜索用时 15 毫秒
121.
Montiel-Armendáriz Sharai Verdugo Claudio Juache-Villagrana Alan Esteban Jiménez-Vega Florinda Quezada-Casasola Andrés Vital-García Cuauhcihualt Escárcega-Ávila Angélica 《Experimental & applied acarology》2021,84(2):473-484
Experimental and Applied Acarology - In total, 57 ticks were collected from six white-tailed deer (Odocoileus virginianus) and three mule deer (O. hemionus) in northern Mexico during the 2017, 2018... 相似文献
122.
Ke Tao Rocha Joao B. T. Tinkov Alexey A. Santamaria Abel Bowman Aaron B. Aschner Michael 《Neurochemical research》2021,46(11):2991-3002
Neurochemical Research - Methylmercury (MeHg) exposure and its harmful effects on the developing brain continue to be a global environmental health concern. Decline in mitochondrial function is... 相似文献
123.
Laudien Jürgen Heran Thomas Häussermann Vreni Försterra Günter Schmidt-Grieb Gertraud M. Richter Claudio 《Coral reefs (Online)》2021,40(5):1657-1665
Coral Reefs - Scleractinian corals feature both sessile and mobile stages and diverse modes of development. In some cases, development can be reversed. Examples include polyp detachment in response... 相似文献
124.
125.
Saskia von Stillfried Sophia Villwock Roman D. Bülow Sonja Djudjaj Eva M. Buhl Angela Maurer Nadina Ortiz-Brüchle Peter Celec Barbara M. Klinkhammer Dickson W.L. Wong Claudio Cacchi Till Braunschweig Ruth Knüchel-Clarke Edgar Dahl Peter Boor 《Microbial biotechnology》2021,14(4):1627-1641
Virus detection methods are important to cope with the SARS-CoV-2 pandemics. Apart from the lung, SARS-CoV-2 was detected in multiple organs in severe cases. Less is known on organ tropism in patients developing mild or no symptoms, and some of such patients might be missed in symptom-indicated swab testing. Here, we tested and validated several approaches and selected the most reliable RT-PCR protocol for the detection of SARS-CoV-2 RNA in patients’ routine diagnostic formalin-fixed and paraffin-embedded (FFPE) specimens available in pathology, to assess (i) organ tropism in samples from COVID-19-positive patients, (ii) unrecognized cases in selected tissues from negative or not-tested patients during a pandemic peak, and (iii) retrospectively, pre-pandemic lung samples. We identified SARS-CoV-2 RNA in seven samples from confirmed COVID-19 patients, in two gastric biopsies, one small bowel and one colon resection, one lung biopsy, one pleural resection and one pleural effusion specimen, while all other specimens were negative. In the pandemic peak cohort, we identified one previously unrecognized COVID-19 case in tonsillectomy samples. All pre-pandemic lung samples were negative. In conclusion, SARS-CoV-2 RNA detection in FFPE pathology specimens can potentially improve surveillance of COVID-19, allow retrospective studies, and advance our understanding of SARS-CoV-2 organ tropism and effects. 相似文献
126.
Amanda Santos Gusmão Lucas Silva Abreu Josean Fechine Tavares Humberto Fonseca de Freitas Samuel Silva da Rocha Pita Elda Gonçalves dos Santos Ivo Santana Caldas André Alexandre Vieira Eliane Oliveira Silva 《化学与生物多样性》2021,18(10):e2100493
Hundreds of millions of people worldwide are affected by Chagas’ disease caused by Trypanosoma cruzi. Since the current treatment lack efficacy, specificity, and suffers from several side-effects, novel therapeutics are mandatory. Natural products from endophytic fungi have been useful sources of lead compounds. In this study, three lactones isolated from an endophytic strain culture were in silico evaluated for rational guidance of their bioassay screening. All lactones displayed in vitro activity against T. cruzi epimastigote and trypomastigote forms. Notably, the IC50 values of (+)-phomolactone were lower than benznidazole (0.86 vs. 30.78 μM against epimastigotes and 0.41 vs. 4.88 μM against trypomastigotes). Target-based studies suggested that lactones displayed their trypanocidal activities due to T. cruzi glyceraldehyde-3-phosphate dehydrogenase (TcGAPDH) inhibition, and the binding free energy for all three TcGAPDH-lactone complexes suggested that (+)-phomolactone has a lower score value (−3.38), corroborating with IC50 assays. These results highlight the potential of these lactones for further anti-T. cruzi drug development. 相似文献
127.
Majid Mohammadhosseini Claudio Frezza Alessandro Venditti Satyajit D. Sarker 《化学与生物多样性》2021,18(11):e2100317
The aim of this review article is to present, for the first time, an appraisal of the phytochemical, ethnobotanical and pharmacological data on Bunium species. The literature search was conducted using the Scopus, Google Scholar and PubMed databases. The genus Bunium has been found to produce both essential oil (EO), mainly comprising monoterpenes and sesquiterpenes, and non-volatile components mainly coumarins and flavonoids. There are several pharmacological activities associated with the Bunium species, especially antioxidant, antibacterial and antifungal properties. The chemotaxonomic appraisal of the phytochemical pattern of the genus is in sink with the current classification of the family. Moreover, this review confirms the significant ethnobotanical and pharmacological potential of different Bunium species. 相似文献
128.
Claudio Marcos Bedran Magalhães Renan Alves Resende Renata Noce Kirkwood 《Journal of electromyography and kinesiology》2013,23(5):1243-1249
The purpose of this study was to identify the gait strategies in women with mild and moderate knee osteoarthritis (OA). Forty women diagnosed with OA of the knee and 40 healthy women participated in the study. Toe-out progression angle, trunk lateral lean, hip internal abduction moment and gait speed were measured using Qualisys ProReflex System and two force plates. Principal component analysis was applied to extract features from the gait waveforms data that characterized the waveforms main modes of temporal variation. Discriminant analysis with a stepwise model was conducted to determine which strategies could best discriminate groups. According to the discriminant model, the PC2 of the internal abduction moment of the hip and the gait speed were the most discriminatory variables between the groups. The OA group showed decreased gait speed, decreased hip internal abduction moment during the loading response phase, and increased hip internal abduction moment during the mid and terminal stance phases. Interventions that may increase hip internal abduction moment, such as the strengthening of the hip abductors muscles, may benefit women with knee OA. Training slower than normal gait speeds must be considered in light of potential adverse implications on overall physical function, daily tasks, and safety. 相似文献
129.
Maria Claudia Cardoso Pereira Valdinar de Araújo Rocha Júnior Martim Bottaro Marcelino Monteiro de Andrade Fabiano Peruzzo Schwartz André Martorelli Rodrigo Celes Jake Carvalho Carmo 《Journal of electromyography and kinesiology》2013,23(2):448-454
The relationship between surface electromyography (SEMG) amplitude and the ventilatory threshold has been extensively studied. However, previous studies of muscle fiber conduction velocity (MFCV) are scarce and present insufficient evidence concerning the relationship between MFCV and metabolic responses during cycling. Based on that fact, the purpose of this study is twofold: (1) to investigate the existence of a MFCV threshold (MFCVT) during cycling and (2) to verify if this possible breakpoint is correlated with the ventilatory threshold (VT) and the SEMG threshold (SEMGT). Eight trained male cyclists (age 36.0 ± 9.7 years) performed an incremental cycling test with initial workload of 150 W gradually incremented by 20 W min?1 until the exhaustion. Gas analyses were conducted using a breath-by-breath open-circuit spirometry and SEMG were registered from vastus lateralis in each pedaling cycle with a linear array of electrodes. A bi-segmental linear regression computer algorithm was used to estimate VT, MFCVT and SEMGT respectively in the carbon dioxide production (VCO2), MFCV and electromyography root mean square (EMG RMS) curves. The one way ANOVA for repeated measures did not reveal any significant difference among VT (77.1 ± 7.5% of VO2max), MFCVT (80.3 ± 10.4% of VO2max) and SEMGT (81.9 ± 11.7% of VO2max). The Bland and Altman procedure confirmed a good concordance between SEMGT and VT (Bias = 5.5 of %VO2max) as well as MFCVT and VT (Bias = 5.2 of %VO2max). The present findings suggest that muscle fiber conduction velocity threshold is a valid and reliable non-invasive tool to obtain information about ventilatory threshold in trained cyclists. 相似文献
130.
Daniel L. M. Vieira André G. Coutinho Gustavo P. E. da Rocha 《Restoration Ecology》2013,21(3):305-311
Tropical dry forest tree species are recognized for their high resprouting ability after disturbance. We tested whether species that commonly produce root and stem suckers can be propagated by large stem and root cuttings, a useful method for landscape restoration programs. We performed four experiments: (1) In a greenhouse, we tested the propagation of six species using large stem cuttings collected from early successional sites. We used the following treatments: (i) dry season collection and planting; (ii) dry season collection, storage in humid soil, and wet season planting; (iii) wet season collection and planting; and (iv) wet season collection and planting after treatment with commercial NAA auxin. (2) Stem cuttings of Myracrodruon urundeuva were planted in a pasture during the rainy season after either NAA, IBA, or no auxin treatment. (3) As a control experiment, we also planted cuttings of Spondias mombin, a species known for successfully regenerating from cuttings. (4) Root cuttings of six species were collected in recently plowed pastures and planted in the greenhouse with and without treatment with NAA auxin. No root cuttings rooted. Only M. urundeuva and Astronium fraxinifolium stem cuttings rooted. Maximum success was obtained for stem cuttings collected and planted in the dry season (23%). Only 13% of M. urundeuva had sprouted by the 15th month of the field experiment. As a result, large cuttings are not recommended for propagation of the studied species. Future studies should include development of suitable methods of root harvesting and prospection of traditional knowledge for species selection. 相似文献