全文获取类型
收费全文 | 14429篇 |
免费 | 885篇 |
国内免费 | 107篇 |
专业分类
耳鼻咽喉 | 82篇 |
儿科学 | 396篇 |
妇产科学 | 215篇 |
基础医学 | 1536篇 |
口腔科学 | 281篇 |
临床医学 | 1444篇 |
内科学 | 3411篇 |
皮肤病学 | 254篇 |
神经病学 | 948篇 |
特种医学 | 407篇 |
外国民族医学 | 6篇 |
外科学 | 2532篇 |
综合类 | 375篇 |
现状与发展 | 1篇 |
一般理论 | 8篇 |
预防医学 | 915篇 |
眼科学 | 343篇 |
药学 | 1263篇 |
中国医学 | 209篇 |
肿瘤学 | 795篇 |
出版年
2024年 | 21篇 |
2023年 | 235篇 |
2022年 | 672篇 |
2021年 | 862篇 |
2020年 | 553篇 |
2019年 | 678篇 |
2018年 | 721篇 |
2017年 | 449篇 |
2016年 | 495篇 |
2015年 | 546篇 |
2014年 | 699篇 |
2013年 | 805篇 |
2012年 | 1226篇 |
2011年 | 1180篇 |
2010年 | 600篇 |
2009年 | 540篇 |
2008年 | 756篇 |
2007年 | 754篇 |
2006年 | 631篇 |
2005年 | 638篇 |
2004年 | 483篇 |
2003年 | 446篇 |
2002年 | 286篇 |
2001年 | 129篇 |
2000年 | 104篇 |
1999年 | 109篇 |
1998年 | 54篇 |
1997年 | 40篇 |
1996年 | 40篇 |
1995年 | 38篇 |
1994年 | 25篇 |
1993年 | 34篇 |
1992年 | 43篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 26篇 |
1980年 | 15篇 |
1979年 | 21篇 |
1978年 | 29篇 |
1974年 | 14篇 |
1972年 | 19篇 |
1969年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Nicole Frumento Alexis Figueroa Tingchang Wang Muhammad N. Zahid Shuyi Wang Guido Massaccesi Georgia Stavrakis James E. Crowe Jr Andrew I. Flyak Hongkai Ji Stuart C. Ray George M. Shaw Andrea L. Cox Justin R. Bailey 《The Journal of clinical investigation》2022,132(15)
A prophylactic hepatitis C virus (HCV) vaccine that elicits neutralizing antibodies could be key to HCV eradication. However, the genetic and antigenic properties of HCV envelope (E1E2) proteins capable of inducing anti-HCV broadly neutralizing antibodies (bNAbs) in humans have not been defined. Here, we investigated the development of bNAbs in longitudinal plasma of HCV-infected persons with persistent infection or spontaneous clearance of multiple reinfections. By measuring plasma antibody neutralization of a heterologous virus panel, we found that the breadth and potency of the antibody response increased upon exposure to multiple genetically distinct infections and with longer duration of viremia. Greater genetic divergence between infecting strains was not associated with enhanced neutralizing breadth. Rather, repeated exposure to antigenically related, antibody-sensitive E1E2s was associated with potent bNAb induction. These data reveal that a prime-boost vaccine strategy with genetically distinct, antibody-sensitive viruses is a promising approach to inducing potent bNAbs in humans. 相似文献
102.
Is Fatimah Sugesti Nur Amaliah Muhammad Fiqri Andrian Tri Pindi Handayani Rico Nurillahi Nurcahyo Iman Prakoso Wiyogo Prio Wicaksono Laemthong Chuenchom 《Sustainable Chemistry and Pharmacy》2019
This research demonstrates the use of biogenic silica derived from bamboo leaf ash as a support for iron oxide nanoparticles. The preparation includes silica extraction from bamboo leaf ash and iron oxide nanoparticle impregnation into the silica gel under hydrothermal conditions, which is followed by calcination at 400 °C for 2 h. The physicochemical characterization includes X-ray diffraction analysis, gas sorption analysis, scanning electron microscopic analysis and transmission electron microscopic analysis. The light absorption capability and the band gap energy of the materials were determined by diffuse-reflectance UV–visible spectrophotometry. The materials obtained by varying the Fe content to 5 and 10% wt. were evaluated in rhodamine B photocatalytic degradation and photooxidation systems. It was found that the materials have a combined hematite and magnetite nanostructure, with the ratio of 9:10, and the particle sizes range from 10 to 40 nm. With a band gap energy of 2.27 eV, the prepared materials produce the successive photocatalytic degradation of rhodamine B. It was clarified that the formation of composite enhances stability and reusability of photocatalyst as shown by the stable initial rate at wide pH range and reuse for 5 cycles. Degradation mechanism is enhanced by the addition of H2O2 as an oxidant, and the investigation of the effect of scavengers shows that the degradation rate not only depends on radical formation but also on other species related to the formation of oxidizing agent. 相似文献
103.
Hammad Ahmed Shah Moncef L. Nehdi Muhammad Imtiaz Khan Usman Akmal Hisham Alabduljabbar Abdullah Mohamed Muhammad Sheraz 《Materials》2022,15(15)
Compressive strength (CS) and splitting tensile strength (STS) are paramount parameters in the design of reinforced concrete structures and are required by pertinent standard provisions. Robust prediction models for these properties can save time and cost by reducing the number of laboratory trial batches and experiments needed to generate suitable design data. Silica fume (SF) is often used in concrete owing to its substantial enhancements of the engineering properties of concrete and its environmental benefits. In the present study, the M5P model tree algorithm was used to develop models for the prediction of the CS and STS of concrete incorporating SF. Accordingly, large databases comprising 796 data points for CS and 156 data records for STS were compiled from peer-reviewed published literature. The predictions of the M5P models were compared with linear regression analysis and gene expression programming. Different statistical metrics, including the coefficient of determination, correlation coefficient, root mean squared error, mean absolute error, relative squared error, and discrepancy ratio, were deployed to appraise the performance of the developed models. Moreover, parametric analysis was carried out to investigate the influence of different input parameters, such as the SF content, water-to-binder ratio, and age of the specimen, on the CS and STS. The trained models offer a rapid and accurate tool that can assist the designer in the effective proportioning of silica fume concrete. 相似文献
104.
Acute toxic effects of hexavalent chromium [Cr(VI)], a widely recognised carcinogenic, mutagenic and redox active metal, were investigated in isolated hepatocytes of goldfish (Carassius auratus). Exposure to 250 microM Cr(VI) induced a significant decrease of cell viability from 94% in controls to 88% and 84% after 30 min and 4 h of exposure, respectively. Cr-toxicity was associated with a concentration-dependent stimulation of the formation of reactive oxygen species (ROS). As one potential source of ROS formation we identified the lysosomal Fe(2+) pool, since the ferric ion chelator deferoxamin inhibited ROS formation by approximately 15%. Lysosomal membranes remained nevertheless intact during Cr-exposure, as determined from neutral red retention in this compartment. Another significant source of ROS appear to be the mitochondria, where a presumably uncoupled increase of respiration by 20-30% was triggered by the metal. Inhibition of mitochondrial respiration by cyanide caused an approximately 40% decrease of Cr-induced ROS-formation, whereas the uncoupling agent carbonyl cyanide m-chlorophenyl hydrazine was without effect. Cellular Ca(2+) homeostasis was not disturbed by Cr(VI) and thus played no role in this scenario. Overall, our data show that Cr(VI) is acutely toxic to goldfish hepatocytes, and its toxicity is associated with the induction of radical stress, presumably involving lysosomes and mitochondria as important sources of ROS formation. 相似文献
105.
Yuzheng Lu M. A. K. Yousaf Shah Naveed Mushtaq Muhammad Yousaf Peter D. Lund Bin Zhu Muhammad Imran Asghar 《RSC advances》2022,12(38):24480
Fast ionic conduction at low operating temperatures is a key factor for the high electrochemical performance of solid oxide fuel cells (SOFCs). Here an A-site deficient semiconductor electrolyte Sr1−xCoxFeO3−δ is proposed for low-temperature solid oxide fuel cells (LT-SOFCs). A fuel cell with a structure of Ni/NCAL-Sr0.7Co0.3FeO3−δ–NCAL/Ni reached a promising performance of 771 mW cm−2 at 550 °C. Moreover, appropriate doping of cobalt at the A-site resulted in enhanced charge carrier transportation yielding an ionic conductivity of >0.1 S cm−1 at 550 °C. A high OCV of 1.05 V confirmed that neither short-circuiting nor power loss occurred during the operation of the prepared SOFC device. A modified composition of Sr0.5Co0.5FeO3−δ and Sr0.3Co0.7FeO3−δ also reached good fuel cell performance of 542 and 345 mW cm−2, respectively. The energy bandgap analysis confirmed optimal cobalt doping into the A-site of the prepared perovskite structure improved the charge transportation effect. Moreover, XPS spectra showed how the Co-doping into the A-site enhanced O-vacancies, which improve the transport of oxide ions. The present work shows that Sr0.7Co0.3FeO3−δ is a promising electrolyte for LT-SOFCs. Its performance can be boosted with Co-doping to tune the energy band structure.Fast ionic conduction at low operating temperatures is a key factor for the high electrochemical performance of solid oxide fuel cells (SOFCs). 相似文献
106.
Aseel Eid Isha Mhatre-Winters Ferass M. Sammoura Melissa K. Edler Richard von Stein Muhammad M. Hossain Yoonhee Han Miriam Lisci Kristina Carney Mary Konsolaki Ronald P. Hart Joan W. Bennett Jason R. Richardson 《Environmental health perspectives》2022,130(8)
Background: The interaction of aging-related, genetic, and environmental factors is thought to contribute to the etiology of late-onset, sporadic Alzheimer’s disease (AD). We previously reported that serum levels of p,p′-dichlorodiphenyldichloroethylene (DDE), a long-lasting metabolite of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT), were significantly elevated in patients with AD and associated with the risk of AD diagnosis. However, the mechanism by which DDT may contribute to AD pathogenesis is unknown.Objectives: This study sought to assess effects of DDT exposure on the amyloid pathway in multiple in vitro and in vivo models.Methods: Cultured cells (SH-SY5Y and primary neurons), transgenic flies overexpressing amyloid beta (), and C57BL/6J and 3xTG-AD mice were treated with DDT to assess impacts on the amyloid pathway. Real time quantitative polymerase chain reaction, multiplex assay, western immunoblotting and immunohistochemical methods were used to assess the effects of DDT on amyloid precursor protein (APP) and other contributors to amyloid processing and deposition.Results: Exposure to DDT revealed significantly higher APP mRNA and protein levels in immortalized and primary neurons, as well as in wild-type and AD-models. This was accompanied by higher levels of secreted in SH-SY5Y cells, an effect abolished by the sodium channel antagonist tetrodotoxin. Transgenic flies and 3xTG-AD mice had more pathology following DDT exposure. Furthermore, loss of the synaptic markers synaptophysin and PSD95 were observed in the cortex of the brains of 3xTG-AD mice.Discussion: Sporadic Alzheimer’s disease risk involves contributions from genetic and environmental factors. Here, we used multiple model systems, including primary neurons, transgenic flies, and mice to demonstrate the effects of DDT on APP and its pathological product . These data, combined with our previous epidemiological findings, provide a mechanistic framework by which DDT exposure may contribute to increased risk of AD by impacting the amyloid pathway. https://doi.org/10.1289/ EHP10576相似文献
107.
El-Sayed M. Sherif Yassir A. Bahri Hamad F. Alharbi Muhammad Farzik Ijaz Ibrahim A. Alnaser 《Materials》2022,15(24)
Ti-15%Zr alloy and Ti-15%Zr-2%Ta alloy were fabricated to be used in biomedical applications. The corrosion of these two alloys after being immersed in simulated body fluid for 1 h and 72 h was investigated. Different electrochemical methods, including polarization, impedance, and chronoamperometric current with time at 400 mV were employed. Also, the surface morphology and the compositions of its formed film were reported by the use of scanning electron microscope and energy dispersive X-ray. Based on the collected results, the presence of 2%Ta in the Ti-Zr alloy passivated its corrosion by minimizing its corrosion rate. The polarization curves revealed that adding Ta within the alloy increases the corrosion resistance as was confirmed by the impedance spectroscopy and current time data. The change of current versus time proved that the addition of Ta reduces the absolute current even at high anodic potential, 400 mV. The results of both electrochemical and spectroscopic methods indicated that pitting corrosion does not occur for both Ti-Zr and Ti-Zr-Ta alloys, even after their immersion in SBF solutions for 72 h. 相似文献
108.
Chandreswar Mahata Juyeong Pyo Beomki Jeon Muhammad Ismail Myounggon Kang Sungjun Kim 《Materials》2022,15(24)
In this work, the sputtered deposited WOx/TaOx switching layer has been studied for resistive random-access memory (RRAM) devices. Gradual SET and RESET behaviors with reliable device-to-device variability were obtained with DC voltage sweep cycling without an electroforming process. The memristor shows uniform switching characteristics, low switching voltages, and a high RON/ROFF ratio (~102). The transition from short-term plasticity (STP) to long-term potentiation (LTP) can be observed by increasing the pulse amplitude and number. Spike-rate-dependent plasticity (SRDP) and paired-pulse facilitation (PPF) learning processes were successfully emulated by sequential pulse trains. By reducing the pulse interval, the synaptic weight change increases due to the residual oxygen vacancy near the conductive filaments (CFs). This work explores mimicking the biological synaptic behavior and further development for next-generation neuromorphic applications. 相似文献
109.
Carmen W. E. Embregts Elmoubashar A. B. A. Farag Devendra Bansal Marjan Boter Anne van der Linden Vincent P. Vaes Ingeborg van Middelkoop-van den Berg Jeroen. IJpelaar Hisham Ziglam Peter V. Coyle Imad Ibrahim Khaled A. Mohran Muneera Mohammed Saleh Alrajhi Md. Mazharul Islam Randa Abdeen Abdul Aziz Al-Zeyara Nidal Mahmoud Younis Hamad Eid Al-Romaihi Mohammad Hamad J. AlThani Reina S. Sikkema Marion P. G. Koopmans Bas B. Oude Munnink Corine H. GeurtsvanKessel 《Viruses》2022,14(12)
Rabies virus (RABV) has a broad host range and infects multiple cell types throughout the infection cycle. Next-generation sequencing (NGS) and minor variant analysis are powerful tools for studying virus populations within specific hosts and tissues, leading to novel insights into the mechanisms of host-switching and key factors for infecting specific cell types. In this study we investigated RABV populations and minor variants in both original (non-passaged) samples and in vitro-passaged isolates of various CNS regions (hippocampus, medulla oblongata and spinal cord) of a fatal human rabies case, and of multiple CNS and non-CNS tissues of experimentally infected mice. No differences in virus populations were detected between the human CNS regions, and only one non-synonymous single nucleotide polymorphism (SNP) was detected in the fifth in vitro passage of virus isolated from the spinal cord. However, the appearance of this SNP shows the importance of sequencing newly passaged virus stocks before further use. Similarly, we did not detect apparent differences in virus populations isolated from different CNS and non-CNS tissues of experimentally infected mice. Sequencing of viruses obtained from pharyngeal swab and salivary gland proved difficult, and we propose methods for improving sampling. 相似文献
110.
Thais Q. Morcatty Paula E. R. Pereyra Ahmad Ardiansyah Muhammad Ali Imron Katherine Hedger Marco Campera K. Anne-Isola Nekaris Vincent Nijman 《Viruses》2022,14(12)
Southeast Asia is considered a global hotspot of emerging zoonotic diseases. There, wildlife is commonly traded under poor sanitary conditions in open markets; these markets have been considered ‘the perfect storm’ for zoonotic disease transmission. We assessed the potential of wildlife trade in spreading viral diseases by quantifying the number of wild animals of four mammalian orders (Rodentia, Chiroptera, Carnivora and Primates) on sale in 14 Indonesian wildlife markets and identifying zoonotic viruses potentially hosted by these animals. We constructed a network analysis to visualize the animals that are traded alongside each other that may carry similar viruses. We recorded 6725 wild animals of at least 15 species on sale. Cities and markets with larger human population and number of stalls, respectively, offered more individuals for sale. Eight out of 15 animal taxa recorded are hosts of 17 zoonotic virus species, nine of which can infect more than one species as a host. The network analysis showed that long-tailed macaque has the greatest potential for spreading viral diseases, since it is simultaneously the most traded species, sold in 13/14 markets, and a potential host for nine viruses. It is traded alongside pig-tailed macaques in three markets, with which it shares six viruses in common (Cowpox, Dengue, Hepatitis E, Herpes B, Simian foamy, and Simian retrovirus type D). Short-nosed fruit bats and large flying foxes are potential hosts of Nipah virus and are also sold in large quantities in 10/14 markets. This study highlights the need for better surveillance and sanitary conditions to avoid the negative health impacts of unregulated wildlife markets. 相似文献