全文获取类型
收费全文 | 7886篇 |
免费 | 655篇 |
国内免费 | 159篇 |
专业分类
耳鼻咽喉 | 26篇 |
儿科学 | 212篇 |
妇产科学 | 37篇 |
基础医学 | 720篇 |
口腔科学 | 162篇 |
临床医学 | 586篇 |
内科学 | 1790篇 |
皮肤病学 | 34篇 |
神经病学 | 437篇 |
特种医学 | 487篇 |
外科学 | 692篇 |
综合类 | 755篇 |
现状与发展 | 1篇 |
预防医学 | 1436篇 |
眼科学 | 71篇 |
药学 | 717篇 |
1篇 | |
中国医学 | 355篇 |
肿瘤学 | 181篇 |
出版年
2024年 | 26篇 |
2023年 | 124篇 |
2022年 | 526篇 |
2021年 | 576篇 |
2020年 | 302篇 |
2019年 | 256篇 |
2018年 | 271篇 |
2017年 | 247篇 |
2016年 | 254篇 |
2015年 | 307篇 |
2014年 | 433篇 |
2013年 | 547篇 |
2012年 | 381篇 |
2011年 | 432篇 |
2010年 | 338篇 |
2009年 | 310篇 |
2008年 | 314篇 |
2007年 | 310篇 |
2006年 | 230篇 |
2005年 | 250篇 |
2004年 | 187篇 |
2003年 | 185篇 |
2002年 | 173篇 |
2001年 | 161篇 |
2000年 | 141篇 |
1999年 | 123篇 |
1998年 | 127篇 |
1997年 | 110篇 |
1996年 | 94篇 |
1995年 | 95篇 |
1994年 | 90篇 |
1993年 | 87篇 |
1992年 | 87篇 |
1991年 | 73篇 |
1990年 | 62篇 |
1989年 | 72篇 |
1988年 | 43篇 |
1987年 | 49篇 |
1986年 | 35篇 |
1985年 | 32篇 |
1984年 | 49篇 |
1983年 | 37篇 |
1982年 | 37篇 |
1981年 | 29篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有8700条查询结果,搜索用时 15 毫秒
31.
Kieran Shay Struebin Abbotts Taylor Russell Ewell Hannah Michelle Butterklee Matthew Charles Bomar Natalie Akagi Gregory P. Dooley Christopher Bell 《Nutrients》2022,14(10)
Cannabidiol (CBD) is widely available and marketed as having therapeutic properties. Over-the-counter CBD is unregulated, many of the therapeutic claims lack scientific support, and controversy exists as to the safety of CBD-liver interaction. The study aims were to compare the pharmacokinetics of commercial CBD and CBD metabolites following the ingestion of five different CBD formulations, determine the influence of CBD on food induced thermogenesis, determine the influence of food on CBD pharmacokinetics, and determine the influence of CBD on markers of liver function. Fourteen males (body mass index ≥ 25 kg/m2) were studied in a placebo-controlled, randomized, crossover design. On five occasions, different CBD formulations were ingested (one per visit). On two additional occasions, CBD or placebo was ingested following a meal. CBD servings were standardized to 30 mg. Considerable pharmacokinetic variability existed between formulations; this pharmacokinetic variability transferred to several of the metabolites. CBD did not influence food induced thermogenesis but did favorably modify early insulin and triglyceride responses. Food appreciably altered the pharmacokinetics of CBD. Finally, CBD did not evoke physiologically relevant changes in markers of liver function. Collectively, these data suggest that consumers should be aware of the appreciable pharmacokinetic differences between commercial CBD formulations, CBD is unlikely to influence the caloric cost of eating but may prove to be of some benefit to initial metabolic responses, consuming CBD with food alters the dynamics of CBD metabolism and increases systemic availability, and low-dose CBD probably does not represent a risk to normal liver function. 相似文献
32.
Tadeusz agoda Sabrina Vantadori Karolina Gowacka Marta Kurek Krzysztof Kluger 《Materials》2022,15(10)
The Smith-Watson-Topper parameter (SWT) in its original form was designed to estimate the fatigue life of metal materials in a uniaxial load state (tension–compression) in the range up to fatigue crack initiation, with non-zero mean values. This parameter is based on the analysis of both stress and strain. Therefore, the stress–strain criterion is the focus, rather than the energy criterion. This paper presents the original SWT model and its numerous modifications. The first part presents different versions of this parameter defined by the normal parameters. Then, it presents versions defined through the tangent parameter and the most promising parameter defined through the tangent and normal parameters. It was noted that the final form of the equivalent value is defined either by stress or by an energy parameter. Therefore, the possible characteristics from which the fatigue life can be determined are also presented. 相似文献
33.
34.
35.
慢性结肠炎在一定情况下可发生癌转化。慢性结肠炎“炎癌转化”是在线粒体能量代谢损伤、有氧糖酵解代谢上调的机制下,肠道上皮细胞代谢失衡,促使炎症微环境向肿瘤微环境转化的过程。认为由正气虚损而致太阴经、阳明经的寒热分离是结肠炎癌转化的触发机制,由邪毒鸱张诱发的气机升降失调是打破促瘤抑瘤平衡,进而邪聚成瘤的关键。临床治疗上应在中医恒动观理论指导下分清慢性结肠炎炎癌转化的不同阶段,灵活把握扶正与解毒的主次,改善肠道炎性环境,调节异常能量代谢,以延缓恶化时间,截断炎癌转化的进程。 相似文献
36.
Zhang YZ Wu HY Ren LW Zhang HS Jia X Zhang YZ 《Journal of traditional Chinese medicine》2010,30(4):272-277
Objective:To examine the effects of modified Shenmai Yin on invigorating vital energy, promoting blood flow, and protection against neural impairment in an endotoxin-induced shock rat model. Methods: Ninety-six SD rats were randomly divided into four groups: sham operation (saline 20 ml/kg), shock model (lipopolysaccharide, LPS, 8 mg/kg), Reformed Shengmai Yin (加味生脉饮 Pulse-activating Decoction) (LPS 8 mg/kg + reformed Shengmai Yin Injection 10 ml/kg), and dexamethasone (LPS 8 mg/kg + dexamethasone 5 mg/kg) groups. Each group was subdivided into 1 h, 2 h, 3 h, and 6 h time points for observation. The carotid artery was separated and connected with a biological functional system to monitor mean arterial pressure (MAP). Brain water levels, malonaldehyde (MDA) content, and superoxide dismutase (SOD) activity were also determined. Results: In the shock model group, MAP was progressively decreased after injection of LPS, brain water and MDA contents were increased, brain SOD activity was decreased, and capillary vessel edema in brain tissue was also observed. All these parameters were improved significantly in both treatment groups, although the effects were more marked with Shengmai Yin than with dexamethasone. Conclusion: Modified Shengmai Yin exhibits strong anti-shock and neuroprotective effects against Endotoxininduced shock. 相似文献
37.
Vronique Braesco Emilio Ros Azmina Govindji Cllia Bianchi Lise Becqueriaux Belinda Quick 《Nutrients》2022,14(13)
The consumption of nuts remains low among European populations despite widespread inclusion as a recommended food group across European dietary guidelines. Front-of-Pack nutrition labelling systems are designed to support consumers make healthier choices and to stimulate product improvement, thus representing a pivotal opportunity to reduce the gap between intakes and recommendations. This study examined how the Nutri-Score algorithm treats nuts and nut-containing products and tested whether slight adjustments could better recognise and motivate nut inclusion in foods and diets. The nutritional score (ScN) and corresponding Nutri-Score letter of 68 nuts and nut-containing products were calculated, using the initial algorithm and slight adjustments, where nut weight was doubled (S1), saturated fats (S2) or energy (S3) from nuts were discounted, or saturated fats were replaced by the saturated fats/lipid ratio (S4). The correlation between the nuts’ content and the ScN was moderate for the initial algorithm (R2 = 0.34) and S1 (R2 = 0.36), but improved for S2, S3 and S4 (R2 = 0.54, 0.55 and 0.52, respectively). Four plain nuts, initially labelled as “B” or “C” obtained a Nutri-Score “A” with S2, S3 and S4. Slight adjustments could better align the Nutri-Score with food-based dietary guidelines, reassure consumers on healthfulness of nuts and nut-containing products, whilst incentivising the inclusion of nuts in diverse foods. 相似文献
38.
Energy harvesting devices made of piezoelectric material are highly anticipated energy sources for power wireless sensors. Tremendous efforts have been made to improve the performance of piezoelectric energy harvesters (PEHs). Noticeably, topology optimization has shown an attractive potential to design PEHs with enhanced energy conversion efficiency. In this work, an alternative yet more practical design objective was considered, where the open-circuit voltage of PEHs is enhanced by topologically optimizing the through-thickness piezoelectric material distribution of plate-type PEHs subjected to harmonic excitations. Compared to the conventional efficiency-enhanced designs, the open-circuit voltage of PEHs can be evidently enhanced by the proposed method while with negligible sacrifice on the energy conversion efficiency. Numerical investigations show that the voltage cancellation effect due to inconsistent voltage phases can be effectively ameliorated by optimally distributed piezoelectric materials. 相似文献
39.
Nirmal Ponnambalam Sarathkumar Thangavel Gunasekaran Murali Nikolai Ivanovich Vatin 《Materials》2022,15(15)
Concrete is the most widely used and most affordable construction material. The structural damage that concrete cracks and fractures may cause can be severe. These concerns have lately been alleviated by new developments in fibre concretes. Recent advancements in fibrous concrete and its evolution have been rapidly drawing researchers’ attentions worldwide, which motivates the development of a new type of composite with superior impact resistance. Preplaced aggregate fibrous concrete (PAFC) is a revolutionary composite comprising a higher dosage of fibres. It has outstanding impact resistance that surpasses those of traditional fibrous concrete. The impact behaviour of PAFC in addition to glass fibre mesh (GFM) has not been investigated thoroughly. To fill this research gap, this study investigates the impact performance of three-layered PAFC comprising steel fibres and GFM insertion. Eight different mixtures were prepared and can be divided into two groups. In the first group, specimens were made with 4% fibres and two single, double and triple layers of GFM insertion between the three-layered concrete. The second group of specimens was reinforced with 5, 2 and 5% steel fibres at the top, middle and bottom layers, respectively. However, the GFM insertion scheme for the second group was the same as the first. Rectangular specimens of size 500 × 100 × 100 mm were cast and tested against drop weight impact. The parameters studied were cracking impact numbers, failure impact number, ductility index and failure patterns. In addition, an analytical model was used to evaluate the impact failure energies. Results indicate that the combined action of steel fibre and GFM exhibited an excellent impact resistance. Increasing the number of GFM insertions between the specimen layer led to increased impact strength. The dose of the fibres utilized in the outer layer of the PAFC was increased, resulting in the material having a higher impact resistance. The cracking impact numbers improved from 28 to 40%, and failure impact numbers ranged from 58.8 to 92.2% when the GFM insertion numbers increased from one to three. 相似文献
40.
Two mesomechanics models were analyzed in an attempt to reveal the relationship between stored energy and back stress. It has been indicated that the portion of elastic stored energy due to residual microstresses (ESR) is closely related to intergranular back stress (Xinter), and the stored energy of dislocations inside grains (ESD) can be estimated with the plastic work of intragranular back stress (Xintra). Then, the evolution of back stress during cyclic loading was studied, and the plastic work of back stress (WpB) was calculated with the low cycle fatigue experimental data of Ti-6Al-4V. The result shows that WpB is partially released at every reverse loading, sufficient to reproduce the evolution of stored energy correctly under cyclic loading. The study also reveals that partially released energy is related to the decrease of Xinter at the initial state of reversal loading resulting from the reduction of the plastic strain incompatibility between grains. 相似文献