全文获取类型
收费全文 | 4800篇 |
免费 | 318篇 |
专业分类
5118篇 |
出版年
2023年 | 23篇 |
2022年 | 55篇 |
2021年 | 99篇 |
2020年 | 52篇 |
2019年 | 86篇 |
2018年 | 97篇 |
2017年 | 90篇 |
2016年 | 128篇 |
2015年 | 196篇 |
2014年 | 225篇 |
2013年 | 323篇 |
2012年 | 434篇 |
2011年 | 375篇 |
2010年 | 228篇 |
2009年 | 200篇 |
2008年 | 318篇 |
2007年 | 296篇 |
2006年 | 296篇 |
2005年 | 247篇 |
2004年 | 259篇 |
2003年 | 237篇 |
2002年 | 172篇 |
2001年 | 51篇 |
2000年 | 40篇 |
1999年 | 37篇 |
1998年 | 60篇 |
1997年 | 38篇 |
1996年 | 53篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1969年 | 7篇 |
1968年 | 10篇 |
1967年 | 9篇 |
排序方式: 共有5118条查询结果,搜索用时 0 毫秒
101.
102.
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
103.
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
104.
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
105.
106.
Piero Masullo Paola Venditti Claudio Agnisola Sergio Di Meo 《Free radical research》2013,47(5):411-421
We recently reported that hyperthyroidism affects the heart response to ischemia/reperfusion. A significant tachycardia during reperfusion was associated with an increase in the oxidative stress of hearts from T3-treated animals. In the present study we checked the possible role of nitric oxide (NO) in this major stress induced by the hyperthyroid state. We compared the functional recovery from ischemia/reperfusion of Langendorff preparations from euthyroid (E) and hyperthyroid (H, ten daily intraperitoneal injections of T3, 10 μg/100 g body weight) rats, in the presence and in the absence of 0.2 mM Nω-nitro-L-arginine (L-NNA). At the end of the ischemia/reperfusion protocol (10 min preischemic perfusion, 20 min global ischemia, 30 min reperfusion) lipid peroxidation, antioxidant capacity (CA) and susceptibility to in vitro oxidative stress were determined on heart homogenates. The main effect of hyperthyroidism on the reperfusion functional response was confirmed to be a strong tachycardic response (154% recovery at 25 min reperfusion) accompanied by a low recovery in both left ventricular diastolic pressure (LVDP) and left ventricular dP/dtmax. This functional response was associated with a reduction in CA and an increase in both lipid peroxidation and susceptibility to oxidative stress. Perfusion of hearts with L-NNA per se had small but significant negative chronotropic and positive inotropic effects on preischemic performance of euthyroid rat hearts only. More importantly, L-NNA perfusion completely blocked the reperfusion tachycardic response in the hyperthyroid rats. Concomitantly, myocardium oxidative state (lipid peroxidation, CA and in vitro susceptibility to oxidative stress) of L-NNA perfused hearts was similar to that of E animals. These results suggest that the higher reperfusion-induced injury occurring in hyperthyroid animals is associated with overproduction of nitric oxide. 相似文献
107.
Carlo Andreoli Claudio Tolomio Laura Scarabel Isabella Moro Sabrina Bellato Marta Moretto 《Plant biosystems》2013,147(6):1007-1027
Abstract During research directed towards the employment of the biological resources of the North Adriatic lagoons, from January 1991 to December 1992, in both tidal phases, a survey was carried out on the phytoplankton and the chemico-physical parameters of the Scardovari lagoon. Data analyses allowed two different areas to be distinguished: one inner, which was generally characterized by high phytoplanktonic densities (St. 3–4), the other outer, which was more influced by marine load (St. 1–2). Photosynthetic picoplankton was dominant in terms of cell number in most samples. Phytoplanktonic fraction >2 μm was represented mainly by diatoms, which showed the higher species number. During the sample observation, some dinoflagellates, considered toxic or potentially toxic, were found. Their presence was important because of their effect on the bivalve mollusc cultures. 相似文献
108.
Abstract In August 2003, dense turfs formed by the filamentous red alga Womersleyella setacea (Hollenberg) R. E. Norris were found in the open part of the Bay of Boka Kotorska, on the shore of Montenegro (southern Adriatic Sea). The habitat and morphology of the alga are described and the impact of the massive development of this species on the structure of the algal communities is discussed. 相似文献
109.
Pooneh Saidi Mahdi Sadeghi Claudio Tenreiro 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2013,29(3):286-294
Monte Carlo simulations and TLD dosimetry have been performed to determine the dose distributions along the central axis of the 12 mm COMS eye plaques loaded with IRA1-103Pd seeds. Several simulations and measurements have been employed to investigate the effect of Silastic insert and air in front of the eye on dosimetry results along the central axis of the plaque and at some critical ocular structures. Measurements were performed using TLD-GR200A circular chip dosimeters in a PMMA eye phantom. The central axis TLD chips locations were arranged in one central column of eye phantom, in 3 mm intervals. The off-axis TLD chips locations were arranged in three off-axis columns around the central axis column. Version 5 of the MCNP code was also used to evaluate the dose distribution around the plaque. The presence of the Silastic insert results in dose reduction of 14% at 5 mm; also about 7% dose reduction appears at the interface point, due to the air presence and lack of the scattering condition. The overall dosimetric parameters for the COMS eye plaque loaded with new palladium seeds are similar to a commercial widely used seed such as Theragenics200. As the dose calculations under TG-43 assumptions do not consider the effect of the plaque backing and Silastic insert for accurate dosimetry, it's suggested to apply the effect of the eye plaque materials and air on dosimetry results along the central axis of the plaque and at some critical ocular structures. 相似文献
110.
Maria Pia Rigobello Roberto Stevanato Federico Momo Sabrina Fabris Guido Scutari Rita Boscolo 《Free radical research》2013,47(3):315-321
Propofol (2,6-diisopropylphenol), some substituted phenols (2,6-dimethylphenol and 2,6-ditertbutylphenol) and their 4-nitrosoderivatives have been compared for their scavenging ability towards 1,1-diphenyl-2-picrylhydrazyl and for their inhibitory action on lipid peroxidation. These products were also compared to the classical antioxidants butylated hydroxytoluene and butylated hydroxyanisole. When measuring the reactivity of the various phenolic derivatives with 1,1-diphenyl-2-picrylhydrazyl the following order of effectiveness was observed: butylated hydroxyanisole>propofol>2,6-dimethylphenol>2,6-di-tertbutylphenol?>?butylated hydroxytoluene. In cumene hydroperoxide-dependent microsomal lipid peroxidation, propofol acts as the most effective antioxidant, while butylated hydroxyanisole, 2,6-di-tertbutylphenol and butylated hydroxytoluene exhibit a rather similar effect, although lower than propofol. In the iron/ascorbate-dependent lipid peroxidation propofol, at concentrations higher than 10?μM, exhibits antioxidant properties comparable to those of butylated hydroxytoluene and butylated hydroxyanisole. 2,6-Dimethylphenol is scarcely effective in both lipoperoxidative systems. The antioxidant properties of the various molecules depend on their hydrophobic characteristics and on the steric and electronic effects of their substituents. However, the introduction of the nitroso group in the 4-position almost completely removes the antioxidant properties of the examined compounds. The nitrosation of the aromatic ring of antioxidant molecules and the consequent loss of antioxidant capacity can be considered a condition potentially occurring in vivo since nitric oxide and its derivatives are continuously formed in biological systems. 相似文献