全文获取类型
收费全文 | 5493篇 |
免费 | 305篇 |
国内免费 | 84篇 |
专业分类
耳鼻咽喉 | 25篇 |
儿科学 | 41篇 |
妇产科学 | 45篇 |
基础医学 | 720篇 |
口腔科学 | 220篇 |
临床医学 | 415篇 |
内科学 | 1080篇 |
皮肤病学 | 91篇 |
神经病学 | 246篇 |
特种医学 | 464篇 |
外科学 | 491篇 |
综合类 | 568篇 |
预防医学 | 273篇 |
眼科学 | 140篇 |
药学 | 442篇 |
5篇 | |
中国医学 | 246篇 |
肿瘤学 | 370篇 |
出版年
2024年 | 12篇 |
2023年 | 124篇 |
2022年 | 462篇 |
2021年 | 492篇 |
2020年 | 166篇 |
2019年 | 161篇 |
2018年 | 154篇 |
2017年 | 153篇 |
2016年 | 155篇 |
2015年 | 180篇 |
2014年 | 285篇 |
2013年 | 448篇 |
2012年 | 220篇 |
2011年 | 251篇 |
2010年 | 195篇 |
2009年 | 183篇 |
2008年 | 229篇 |
2007年 | 199篇 |
2006年 | 191篇 |
2005年 | 179篇 |
2004年 | 157篇 |
2003年 | 149篇 |
2002年 | 136篇 |
2001年 | 129篇 |
2000年 | 82篇 |
1999年 | 68篇 |
1998年 | 76篇 |
1997年 | 75篇 |
1996年 | 60篇 |
1995年 | 52篇 |
1994年 | 37篇 |
1993年 | 37篇 |
1992年 | 47篇 |
1991年 | 34篇 |
1990年 | 34篇 |
1989年 | 27篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 24篇 |
1985年 | 38篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1976年 | 5篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有5882条查询结果,搜索用时 18 毫秒
81.
The comparison of effects of processed Aconiti tuber, U50488H and MK-801 on the antinociceptive tolerance to morphine 总被引:1,自引:0,他引:1
Shu H Hayashida M Huang W An K Chiba S Hanaoka K Arita H 《Journal of ethnopharmacology》2008,117(1):158-165
In the previous studies, we demonstrated that an oriental herbal medicine, processed Aconiti tuber (PAT), at subanalgesic doses could inhibit or reverse the antinociceptive tolerance to morphine. In the present study, we compared the effect of PAT, trans-(+/-)-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidin)cyclohexyl)-benzeneacetamide methane sulfonate hydrate (U50488H), a selective kappa opioid receptor (KOR) agonist, and (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine-maleate (MK-801), a N-methyl-D-aspartate (NMDA) receptor antagonist, on the antinociceptive tolerance to morphine in the same experimental condition. Mice received subcutaneous morphine (10 mg/kg), and oral PAT at a subanalgesic dose (0.3 g/kg for mechanical or 1.0 g/kg for thermal test), or intraperitoneal U50488H at a subanalgesic dose (3 mg/kg), or MK-801 at a subanalgesic dose (0.1 mg/kg) once daily for 14 days. The mechanical nociceptive threshold was measured before, and at 60 min by tail pressure testing, and thermal nociceptive latency was measured before, and at 30 min by hot plate testing, after daily morphine injections. PAT and U50488H could not only inhibit the development of morphine tolerance but also reverse the already-developed morphine tolerance, while MK-801 could only inhibit the development of morphine tolerance but not reverse the already-developed morphine tolerance, in both mechanical and thermal nociceptive tests. These data suggested that PAT, an indirect-acting KOR agonist, share the common pharmacological property of KOR agonists on morphine tolerance, and that PAT may be superior to some NMDA receptor antagonists which do not reverse already-developed morphine tolerance. 相似文献
82.
Varma R Soneja H Samuel N Sangha E Clark TJ Gupta JK 《European journal of obstetrics, gynecology, and reproductive biology》2008,140(1):76-81
BACKGROUND: Thermal balloon endometrial ablation (TBEA) is increasingly being performed in the outpatient setting under local anaesthesia (LA) rather than in a daycase setting under general anaesthesia (GA). Our aim was to compare the post operative rescue analgesia requirements and duration of hospital stay in women undergoing outpatient (LA) and daycase (GA) TBEA. METHODS: Prospective observational study of consecutively recruited women who underwent outpatient (LA) TBEA (n=51) and daycase (GA) TBEA (n=50) over the same time period. Analgesia that was provided additional to the standard administered analgesic regimen was considered rescue analgesia. The main outcome measures were requirement for rescue analgesia and duration of hospital stay in both cohorts. RESULT(S): LA compared to GA cohorts had shorter hospital stays (11h [95% CI 9-13] vs. 17h [95% CI 14-20]) and lower analgesia requirements. However, multivariate regression, correcting for all known confounders, showed that duration of stay was independent of setting for ablation or amount of rescue analgesia. CONCLUSION(S): Duration of hospital stay is not entirely dependent on whether outpatient or daycase endometrial ablation is considered. This unexpected preliminary finding deserves to be validated in future confirmatory trials that compare outpatient and daycase treatments. We also discuss the confounding factors that should be considered when designing such trials. 相似文献
83.
84.
目的探讨耳部光针治疗小儿支气管炎的临床疗效。方法 124例急慢性支气管炎患儿按就诊时间随机分为治疗组64例和对照组60例,两组患者在性别、年龄、病程、病情程度方面经统计学处理差异无统计学意义(P〉0.05),具有可比性,在接受常规治疗的基础上,治疗组采用半导体激光照射耳部穴位,每日1次;对照组采用红外止咳贴贴敷背部特定穴位,每日1次。观察治疗后两组患儿临床症状及体征改善情况。结果治疗组显效率为78.1%,明显高于对照组,差异有统计学意义(P〈0.05);治疗组治疗后体温下降、咳嗽减轻、咳痰减少,肺部啰音减少,起效时间缩短,与对照组比较,差异有统计学意义(P〈0.05);治疗组治疗后体温、咯痰量化积分与对照组比较,差异有统计学意义(P〈0.05)。结论耳部光针治疗小儿急慢性支气管炎简便有效,值得临床推广应用。 相似文献
85.
通过构建人体三维生物传热模型.对含肿瘤组织的体表热图表现进行评估.发现当前远红外成像设备在诊断早期或深层肿瘤时.由于精度和分辨率所限,不易得到准确的诊断结果。在此基础上.设计不同制冷水平下的概念性红外成像实验予以证实,并对应提出一种超低温双腔体冷却方法,以期改善现有红外设备冷却方式,从而提高其成像精度和准确度。本文研究对于肿瘤早期影像学诊断具有现实意义。 相似文献
86.
光动力疗法(PDT)是治疗肿瘤的主要方法之一。以光与生物组织的相互作用原理及生物效应理论为依据,对不同运转方式的激光在肿瘤治疗过程中所产生的光动力效应、热效应以及生物刺激作用等方面进行分析,并对激光作用时间不同和总能量的差异对疗效的影响进行了分析。从发展的角度讲,为使PDT达到最佳疗效,同时有益于新光源的开发和利用,PDT采用脉冲激光无疑是一种最佳的选择。 相似文献
87.
Rahul Ramesh Nair Moni Mohan Mondal Shanmugham Venkatachalam Srinivasan Dirk Weichgrebe 《Materials》2022,15(12)
Synthesizing biochar from mineral- and ash-rich waste biomass (MWB), a by-product of human activities in urban areas, can result in renewable and versatile multi-functional materials, which can also cater to the need of solid waste management. Hybridizing biochar with minerals, silicates, and metals is widely investigated to improve parent functionalities. MWB intrinsically possesses such foreign materials. The pyrolysis of such MWB is kinetically complex and requires detailed investigation. Using TGA-FTIR, this study investigates and compares the kinetics and decomposition mechanism during pyrolysis of three types of MWB: (i) mineral-rich banana peduncle (BP), (ii) ash-rich sewage sludge (SS), and (iii) mineral and ash-rich anaerobic digestate (AD). The results show that the pyrolysis of BP, SS, and AD is exothermic, catalyzed by its mineral content, with heat of pyrolysis 5480, 4066, and 1286 kJ/kg, respectively. The pyrolysis favors char formation kinetics mainly releasing CO2 and H2O. The secondary tar reactions initiate from ≈318 °C (BP), 481 °C (SS), and 376 °C (AD). Moreover, negative apparent activation energies are intrinsic to their kinetics after 313 °C (BP), 448 °C (SS), and 339 °C (AD). The results can support in tailoring and controlling sustainable biochar synthesis from slow pyrolysis of MWB. 相似文献
88.
Anna Korneva Boris Straumal Alena Gornakova Askar Kilmametov ukasz Gondek Lidia Lityska-Dobrzyska Robert Chulist Magorzata Pomorska Pawe Ziba 《Materials》2022,15(12)
This paper discusses the features of ω-phase formation and its thermal stability depending on the phase composition, alloying element and the grain size of the initial microstructure of Ti–Nb and Ti–Mo alloys subjected to high-pressure torsion (HPT) deformation. In the case of two-phase Ti–3wt.% Nb and Ti–20wt.% Nb alloys with different volume fractions of α- and β-phases, a complete β→ω phase transformation and partial α→ω transformation were found. The dependence of the α→ω transformation on the concentration of the alloying element was determined: the greater content of Nb in the α-phase, the lower the amount of ω-phase that was formed from it. In the case of single-phase Ti–Mo alloys, it was found that the amount of ω-phase formed from the coarse-grained β-phase of the Ti–18wt.% Mo alloy was less than the amount of the ω-phase formed from the fine α′-martensite of the Ti–2wt.% Mo alloy. This was despite the fact that the ω-phase is easier to form from the β-phase than from the α- or α′-phase. It is possible that the grain size of the microstructure also affected the phase transformation, namely, the fine martensitic plates more easily gain deformation and overcome the critical shear stresses necessary for the phase transformation. It was also found that the thermal stability of the ω-phase in the Ti–Nb and Ti–Mo alloys increased with the increasing concentration of Nb or Mo. 相似文献
89.
Yara Barbosa Franco Clever Aparecido Valentin Marcelo Kobelnik Jefferson Lins da Silva Clovis Augusto Ribeiro Marta Pereira da Luz 《Materials》2022,15(12)
Nonwoven geotextiles are geosynthetic products that are highly susceptible to ultraviolet degradation because light can reach a large area of the material due to its fiber arrangement. Even with additives, which delay the degradation process, material decomposition still occurs, and therefore the product’s long-term durability can be affected. In this paper, the mechanical and thermal behavior of a commercial nonwoven polyester geotextile subjected to accelerated ultraviolet aging tests were evaluated. The deterioration was evaluated by comparing the physical properties (mass per unit area, thickness, and tensile strength) and thermal behavior (thermogravimetry—TG, thermomechanical analysis—TMA, and differential scanning calorimetry—DSC) before and after exposure times of 500 h and 1000 h. The results showed that the ultraviolet aging tests induced some damage in the polyester fibers, leading to the deterioration of their tensile strength. For 1000 h of exposure, in which the reduction was larger, scanning electron microscopy (SEM) found some superficial disruption of the fibers, indicative of damage. TG and DSC could not capture the effects of UV radiation on polymer degradation, unlike TMA. This latter technique was effective in showing the differences between specimens before and after UV exposure. 相似文献
90.
Xianze Ao Bowen Li Bin Zhao Mingke Hu Hui Ren Honglun Yang Jie Liu Jingyu Cao Junsheng Feng Yuanjun Yang Zeming Qi Liangbin Li Chongwen Zou Gang Pei 《Proceedings of the National Academy of Sciences of the United States of America》2022,119(17)
The sun (∼6,000 K) and outer space (∼3 K) are two significant renewable thermodynamic resources for human beings on Earth. The solar thermal conversion by photothermal (PT) and harvesting the coldness of outer space by radiative cooling (RC) have already attracted tremendous interest. However, most of the PT and RC approaches are static and monofunctional, which can only provide heating or cooling respectively under sunlight or darkness. Herein, a spectrally self-adaptive absorber/emitter (SSA/E) with strong solar absorption and switchable emissivity within the atmospheric window (i.e., 8 to 13 μm) was developed for the dynamic combination of PT and RC, corresponding to continuously efficient energy harvesting from the sun and rejecting energy to the universe. The as-fabricated SSA/E not only can be heated to ∼170 °C above ambient temperature under sunshine but also be cooled to 20 °C below ambient temperature, and thermal modeling captures the high energy harvesting efficiency of the SSA/E, enabling new technological capabilities.Heating and cooling are two kinds of significant end uses of thermal energy in society, which exist in various conditions (e.g., space/water heating, space cooling, and industrial processes) and account for 51% of the total final energy consumption (1). For example, the heating and cooling of buildings are responsible for nearly 48% of the building energy consumption, increasing to be the largest individual energy expense (2). Therefore, heat and cool harvesting relying on clean techniques from renewable energy resources has drawn remarkable attention from fields of engineering to material science because it has considerable potential for global energy conservation and greenhouse emission reduction. Thermodynamically, any heat transportation and work-generation process requires a temperature gradient. The hot sun (∼6,000 K) and cold outer space (∼3 K) are the ultimate heat source and heat sink for the Earth. Theoretical analysis reveals that maximal output work can be extracted from nonreciprocal systems based on the temperature difference between the sun and Earth (∼300 K) with an ultimate solar energy harvesting efficiency limit of 93.3%, while a maximal work of 153.1 W·m−2 can also be obtained on the basis of temperature difference between the Earth and outer space (3, 4). Thus, the sun and outer space are two significant renewable thermodynamic resources for the Earth, which can be effectively utilized for clean heat and cool collection.Photothermal (PT) is a widely used solar thermal collection method that employs solar absorbers to capture solar photons and convert them to heat. Thermal analysis reveals that a good candidate for a solar absorber should have high solar absorptivity and low thermal emissivity simultaneously for efficient solar thermal collection. Various materials, including multilayer metal/ceramic films (5, 6), photonic crystals (7, 8), and metamaterials (9, 10), have been developed for spectrally selective solar absorbers and have been used for real-world applications. Meanwhile, radiative cooling (RC) has re-elicited considerable interest in recent years because it can passively provide clean cooling without any extra energy input (11–14). The waste heat of terrestrial objects can be continuously pumped into the cold outer space, relying on the transparent atmospheric window (i.e., 8 to 13 μm). So, high emissivity within the atmospheric window of materials is necessary for efficient RC, and excellent solar reflection is also important for RC under sunshine. Thus, different materials with the tailored spectrum, such as photonic structures (15–17), structure materials (18), energy-saving paints (19–21), and even metamaterials (22–24), have been reported for passive cooling. On the potential application level, RC implementations also span a range of fields, including passive cooling of buildings (25–27), thermal management of textiles and color surfaces (28–30), atmospheric water harvesting (31), and thermoelectric generation (32, 33). Although the reported PT and RC can generate heat and cold with high efficiency through different spectrally selective materials, most of the approaches are static and monofunctional, which can only provide heating or cooling under sunlight or darkness. Therefore, the dynamical integration of PT and RC for continuously efficient heat and cool harvesting is a new topic for the energy exploitation of the sun and outer space. The tunable combination of PT and RC hybrid utilization has been recently proposed, but mechanical methods such as switching (e.g., flip action) a PT absorber and an RC emitter manually (34) or changing the optical properties of the materials through extra force stimuli (35) are preferred.Herein, a smart strategy for the dynamic combination of daytime PT and nighttime RC is proposed, corresponding to continuously efficient energy harvesting from the sun and rejecting energy to the universe. A spectrally self-adaptive absorber/emitter (SSA/E) with solar absorption of over 0.8 and emissivity modulation capability of regulating from broadband emissivity of 0.25 within the mid-infrared (MIR) region to the selective high emissivity of 0.75 within the atmospheric window is designed and fabricated for the proof of the concept. Outdoor thermal experimental results demonstrate that the SSA/E can be heated to ∼170 °C above ambient temperature in the daytime PT mode and passively cooled to ∼20 °C below ambient temperature in the nighttime RC mode. Moreover, the heat and cool energy gains of the SSA/E system are respectively predicted to be 78% and 103% larger than those of the reference system that combines static and monofunctional PT absorber and RC emitter. 相似文献