全文获取类型
收费全文 | 5878篇 |
免费 | 250篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 133篇 |
儿科学 | 231篇 |
妇产科学 | 264篇 |
基础医学 | 791篇 |
口腔科学 | 72篇 |
临床医学 | 434篇 |
内科学 | 1465篇 |
皮肤病学 | 75篇 |
神经病学 | 484篇 |
特种医学 | 77篇 |
外科学 | 392篇 |
综合类 | 38篇 |
一般理论 | 1篇 |
预防医学 | 470篇 |
眼科学 | 184篇 |
药学 | 633篇 |
中国医学 | 11篇 |
肿瘤学 | 400篇 |
出版年
2024年 | 7篇 |
2023年 | 46篇 |
2022年 | 155篇 |
2021年 | 240篇 |
2020年 | 94篇 |
2019年 | 120篇 |
2018年 | 144篇 |
2017年 | 136篇 |
2016年 | 157篇 |
2015年 | 156篇 |
2014年 | 219篇 |
2013年 | 268篇 |
2012年 | 435篇 |
2011年 | 479篇 |
2010年 | 258篇 |
2009年 | 204篇 |
2008年 | 342篇 |
2007年 | 425篇 |
2006年 | 399篇 |
2005年 | 393篇 |
2004年 | 400篇 |
2003年 | 370篇 |
2002年 | 330篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 22篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 20篇 |
1995年 | 25篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有6155条查询结果,搜索用时 15 毫秒
71.
The aim of the paper is to determine the influence of the surface treatment on the adhesive properties of steel sheet surfaces and the strength of the adhesive joints of steel sheets. The paper also aims to assess the degree of steel sheets’ surface treatment in the bonding process. Due to the many methods of surface treatment and types of materials, the assessment of the surface treatment method is extremely important in adhesive processes. Two variants of the surface treatment were used: without a paint coating and with a paint coating, divided into two groups (without degreasing and with degreasing). Additionally, in the case of the analysis of the steel samples without the paint coating, mechanical treatment was applied. Two-component epoxy adhesive, prepared on the basis of bisphenol A and a polyamide curing agent, was used to prepare the single-lap adhesive joints of the steel sheets. The tests determined: (i) the adhesive properties of the steel sheets’ surface based on the measurement of the contact angle of polar and apolar liquids (including wettability, work of adhesion, and surface free energy), (ii) surface roughness parameters (PN EN ISO 4287), and (iii) mechanical properties (load capacity and shear strength) of the steel sheets’ adhesive joints (EN DIN 1465). Contact angle measurements of the steel sheet surfaces showed that the polar liquid better reflects the obtained strength results of the analyzed adhesive joints than the apolar liquid. Furthermore, better wettability of the surface of steel sheets with both polar and apolar liquids was obtained for samples whose surface was subjected to degreasing. It can also be concluded that the wettability of the surface can be used as one of the indicators of the degree of the surface treatment for the bonding process. 相似文献
72.
Mateusz Grajek Karolina Krupa-Kotara Krzysztof Sas-Nowosielski Ewa Misterska Joanna Kobza 《Nutrients》2022,14(14)
(1) Background: The literature emphasizes the role of many factors influencing the onset of eating disorders (EDs) and their mutual influence on each other. Therefore, this study aimed to evaluate and compare the prevalence of orthorexic behaviors in groups of health-related and non-health-related students in terms of their differential health behaviors—diet and physical activity levels. (2) The study included 300 individuals representing two equal groups of fields of study, which for the study were called the health-related field (HRF) and the non-health-related field (NRF). (3) Results: Based on the results of the dietary assessment, it was found that the best dietary model was characterized by the HRF group; in this group, 97.2% of students were characterized by a very good and good dietary mode. The NRF group, on the other hand, was dominated by a sufficient dietary mode for 64.4% of all cases in this group (94 people), while the dietary model marked as “good” was less popular, at 24.6% of this group (36 people). (4) Conclusions: Based on the cited self-research and information from the literature, it can be concluded that the problem of orthorexia is still a new issue at the level of social sciences, medical sciences, and health sciences. The psychometric tools used in this study allowed us to demonstrate the prevalence of the aforementioned eating disorders in the sample groups of students. 相似文献
73.
Kevin Martell Hans Chung Gerard Morton Danny Vesprini Chia-Lin Tseng Ewa Szumacher Patrick Cheung Will Chu Stanley Liu Andrew Loblaw 《Canadian Urological Association journal》2022,16(8):E437
IntroductionWe aimed to determine the minimum cross-sectional ellipsoid area on magnetic resonance (MR) of intraprostatic nodules that best predicts for subsequent targeted biopsies revealing ≥ grade group (GG) 2 disease.MethodsForty-six patients previously diagnosed with GG 1 prostate adenocarcinoma who received cognitively fused, MR-guided, transperineal targeted biopsies in addition to six random biopsies were included in this analysis. A Youden cutpoint analysis was used to determine the ellipsoid area in the axial plane best predicting for ≥GG 2 disease within the targeted biopsy cores and logistic regression used to assess the result.ResultsMedian time from MR imaging to targeted biopsy was 2.4 (1.4–5.5) months. Forty of 46 (87%) patients had one nodule and 6/46 (13%) had two separate nodules on MR that received targeted biopsy. Of the 52 nodules, five (10%), 33 (63%), and 14 (27%) were Prostate Imaging-Reporting and Data System (PI-RADS) 3, 4, and 5, respectively. Thirteen (25%), six (12%), and 33 (64%) were in the anterior, medial, and posterior regions of the prostate, respectively. Median area was 0.72 (0.49–1.29) cm2 (average diameter 9.5 mm). Fifteen of 46 (33%) patients had ≥1 random biopsy and 20/52 (38%) nodules had ≥1 targeted biopsy revealing ≥GG 2 disease. The optimal area cutpoint was ≥0.7 cm2, with an area under the curve of 0.671 (0.510–0.832). On logistic regression, area ≥0.7 cm2 was solely predictive of targeted biopsy revealing ≥GG 2 disease (odds ratio 6.5, 1.3–32.4, p=0.022).ConclusionsNodule area ≥0.7 cm2 may predict for transperineal-based targeted biopsies being positive for ≥GG 2 disease when 1–2 cores are taken. 相似文献
74.
The article presents research on ergonomics, biophysical comfort and safety of protective clothing. The resistance of the structural, thermal and mechanical properties of five fabrics (CBXS400, GG200T, Twaron CT736, Dyneema HB26 and T1790C), differing in geometry and raw material composition used in space suits, to dangerous ionizing radiation (β and γ) occurring in space was tested. For both types of radiation, four identical one-time doses in the range of 25–100 kGy were used. The effect of the applied absorbed doses of β and γ radiation on the parameters of textiles influencing ergonomics and safety of the cosmonaut’s work was verified by structural tests (micro-computed tomography and optical microcopy), thermal resistance tests (sweating guarded-hotplate) and strength tests (tensile testing machine). Experimental studies of thermal properties are supplemented with heat transport simulations using the finite volume method performed with 3D models of real textiles. The greatest reduction of thermal resistance for Twaron CT736 (−0.0667 m2·°C·W−1 for 100 kGy of β-radiation) and Dyneema HB26 (−0.0347 m2·°C·W−1 for 50 kGy of β-radiation) is observed. Strength tests have shown that all tested textiles are resistant to both types of radiation. Three textiles were selected to create a three-layer assembly with potential application in a cosmonaut’s glove (Extravehicular Activity—EVA). 相似文献
75.
Kinga Andrysiak-Karmiska Alicja Hoffmann-Przybylska Piotr Przybylski Zuzanna Witkowska Ewa Walicka Maria Borysewicz-Lewicka Iwona Gregorczyk-Maga Mansur Rahnama Karolina Gerreth Justyna Opydo-Szymaczek 《Nutrients》2022,14(9)
(1) Background: Dental caries is a chronic disease that affects a child’s dentition from the first stages of life. Several factors contribute to the development of the disease, including an improper diet. This cross-sectional study aimed to identify risk factors of dental caries in 12-year-old adolescents from Greater Poland and Lubusz Provinces (Poland). (2) Material and methods: The research was conducted in adolescents from five primary schools. A questionnaire consisted of close-ended questions on socioeconomic characteristics on family, diet, and oral hygiene habits. An assessment of the dentition was carried out in accordance with World Health Organization (WHO) recommendations. In addition to cavitated carious lesions, incipient caries lesions were noted according to the International Caries Detection and Assessment System, adapted for epidemiological studies (ICDASepiDMFt). (3) Results: The mean number of teeth with untreated caries; removed due to caries; and restored because of caries (DMFt) was 1.52 ± 1.90, while the ICDASepiDMFt index amounted to 2.64 ± 2.55, respectively. Children who did not brush every day had significantly higher odds of having ICDASepiDMFt > 0 than children brushing at least once daily (OR = 10.32, 95% CI = 1.36–78.32, p = 0.0240). Adolescents who drank sweet carbonated drinks every day had significantly higher ICDASepiDMTt than children who drank sweet carbonated drinks less frequently (p = 0.0477). (4) Conclusions: The research revealed that dental caries indices of 12-year-old adolescents from Greater Poland and Lubusz Provinces depend mainly on oral hygiene behaviors. The only significant nutritional factor that differentiated the caries intensity was the daily consumption of sweet carbonated drinks. 相似文献
76.
77.
Brett A. Colson Inna N. Rybakova Ewa Prochniewicz Richard L. Moss David D. Thomas 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(50):20437-20442
We have determined the effects of myosin binding protein-C (MyBP-C) and its domains on the microsecond rotational dynamics of actin, detected by time-resolved phosphorescence anisotropy (TPA). MyBP-C is a multidomain modulator of striated muscle contraction, interacting with myosin, titin, and possibly actin. Cardiac and slow skeletal MyBP-C are known substrates for protein kinase-A (PKA), and phosphorylation of the cardiac isoform alters contractile properties and myofilament structure. To determine the effects of MyBP-C on actin structural dynamics, we labeled actin at C374 with a phosphorescent dye and performed TPA experiments. The interaction of all three MyBP-C isoforms with actin increased the final anisotropy of the TPA decay, indicating restriction of the amplitude of actin torsional flexibility by 15–20° at saturation of the TPA effect. PKA phosphorylation of slow skeletal and cardiac MyBP-C relieved the restriction of torsional amplitude but also decreased the rate of torsional motion. In the case of fast skeletal MyBP-C, its effect on actin dynamics was unchanged by phosphorylation. The isolated C-terminal half of cardiac MyBP-C (C5–C10) had effects similar to those of the full-length protein, and it bound actin more tightly than the N-terminal half (C0–C4), which had smaller effects on actin dynamics that were independent of PKA phosphorylation. We propose that these MyBP-C-induced changes in actin dynamics play a role in the functional effects of MyBP-C on the actin–myosin interaction. 相似文献
78.
Tadeusz Włostowski Paweł Kozłowski Barbara Łaszkiewicz-Tiszczenko Ewa Oleńska Olgierd Aleksandrowicz 《Bulletin of environmental contamination and toxicology》2014,93(5):526-531
The objectives of this study were (1) to determine cadmium (Cd) accumulation in the midgut gland of a land snail Helix pomatia L. inhabiting residential areas of the 14 largest cities in Poland, and (2) to examine whether the accumulated Cd exerted any toxic effects. The average accumulation of Cd in the midgut gland of snails, weighing 16–18 g, ranged from 7.00 to 87.3 µg/g dry weight (0.06–0.77 µmol/g) and differed significantly among animals from the various urban areas. This difference in Cd accumulation was not related to city population, but was associated with the topsoil Cd (R2 = 0.868, p < 0.0001). The tissue Cd was not found to produce toxicity (histopathology, programmed cell death, lipofuscin formation or lipid peroxidation), probably due to the induction of sufficiently high quantities of metallothionein and glutathione, well-known protective molecules. 相似文献
79.
Respiration phase‐locks to fast stimulus presentations: Implications for the interpretation of posterior midline “deactivations”
下载免费PDF全文
![点击此处可从《Human brain mapping》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Willem Huijbers Cyriel M.A. Pennartz Ewa Beldzik Aleksandra Domagalik M. Vinck Winnie F. Hofman Roberto Cabeza Sander M. Daselaar 《Human brain mapping》2014,35(9):4932-4943
The posterior midline region (PMR)—considered a core of the default mode network—is deactivated during successful performance in different cognitive tasks. The extent of PMR‐deactivations is correlated with task‐demands and associated with successful performance in various cognitive domains. In the domain of episodic memory, functional MRI (fMRI) studies found that PMR‐deactivations reliably predict learning (successful encoding). Yet it is unclear what explains this relation. One intriguing possibility is that PMR‐deactivations are partially mediated by respiratory artifacts. There is evidence that the fMRI signal in PMR is particularly prone to respiratory artifacts, because of its large surrounding blood vessels. As respiratory fluctuations have been shown to track changes in attention, it is critical for the general interpretation of fMRI results to clarify the relation between respiratory fluctuations, cognitive performance, and fMRI signal. Here, we investigated this issue by measuring respiration during word encoding, together with a breath‐holding condition during fMRI‐scanning. Stimulus‐locked respiratory analyses showed that respiratory fluctuations predicted successful encoding via a respiratory phase‐locking mechanism. At the same time, the fMRI analyses showed that PMR‐deactivations associated with learning were reduced during breath‐holding and correlated with individual differences in the respiratory phase‐locking effect during normal breathing. A left frontal region—used as a control region—did not show these effects. These findings indicate that respiration is a critical factor in explaining the link between PMR‐deactivation and successful cognitive performance. Further research is necessary to demonstrate whether our findings are restricted to episodic memory encoding, or also extend to other cognitive domains. Hum Brain Mapp 35:4932–4943, 2014. © 2014 相似文献
80.