全文获取类型
收费全文 | 2933篇 |
免费 | 171篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 68篇 |
儿科学 | 64篇 |
妇产科学 | 43篇 |
基础医学 | 488篇 |
口腔科学 | 76篇 |
临床医学 | 261篇 |
内科学 | 534篇 |
皮肤病学 | 30篇 |
神经病学 | 253篇 |
特种医学 | 250篇 |
外科学 | 475篇 |
综合类 | 31篇 |
预防医学 | 136篇 |
眼科学 | 36篇 |
药学 | 216篇 |
中国医学 | 10篇 |
肿瘤学 | 148篇 |
出版年
2023年 | 24篇 |
2022年 | 38篇 |
2021年 | 70篇 |
2020年 | 40篇 |
2019年 | 53篇 |
2018年 | 87篇 |
2017年 | 72篇 |
2016年 | 58篇 |
2015年 | 86篇 |
2014年 | 125篇 |
2013年 | 145篇 |
2012年 | 235篇 |
2011年 | 262篇 |
2010年 | 176篇 |
2009年 | 120篇 |
2008年 | 191篇 |
2007年 | 189篇 |
2006年 | 180篇 |
2005年 | 199篇 |
2004年 | 150篇 |
2003年 | 132篇 |
2002年 | 107篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 23篇 |
1997年 | 35篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1973年 | 6篇 |
1970年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有3119条查询结果,搜索用时 15 毫秒
31.
Andrzej Lorek Katarzyna Steinhof-Radwaska Wojciech Zarbski Joanna Lorek Zoran Stoj
ev Jacek Zych Aleksandra Syrkiewicz Pawe Niemiec Karol Szyluk 《Current oncology (Toronto, Ont.)》2022,29(5):2887
(1) Background: The purpose of the study was a retrospective, comparative assessment of complications of the surgical sentinel node biopsy (SNB) procedure in breast cancer using the radiotracer method and the SentiMag® method on groups of patients after 3.5 years of use. (2) Methods: The material was a group of 345 patients with primary surgical breast cancer who underwent the SNB procedure with the use of a radiotracer in combination with wide local excision (WLE), simple amputation (SA) with SNB and an independent SNB procedure in the period from May 2018 to January 2021 in the Department of Oncological Surgery. Of the patients who were monitored in the Hospital Outpatient Clinic, 300 were enrolled. The analyzed group was compared in terms of the occurrence of the same complications with the group of 303 patients also operated on in our center in the period from January 2014 to September 2017, in which SN identification was performed using the SentiMag® method. (3) Results: The most common complications found were sensation disorders in the arm, which occurred in 16 (14.1%) patients using the radiotracer method, SentiMag®-11 (9.9%). By comparing the complication rate between the methods with the radiotracer (n = 300) and SentiMag® (n = 303), no significant differences were found. (4) Conclusions: Sentinel node (SN) identification using the radiotracer method and the SentiMag® method are comparable diagnostic methods in breast cancer, with a low risk of complications. 相似文献
32.
An improved human tumor stem cell assay in ovarian cancer 总被引:1,自引:0,他引:1
P G Rose A Koolemans-Beynen J G Boutselis J P Minton G E Milo 《American journal of obstetrics and gynecology》1987,156(3):730-734
To evaluate the effect of improved growth rates of ovarian cancers in the human tumor stem cell assay and its value in predicting clinical chemotherapy response, we studied 59 assays in 54 patients. A total of 81.6% of solid specimens and 85.7% of ascites specimens were successfully cultured and yielded an overall growth rate of 82.9%. Simultaneous primary and metastatic cultures were concordant for chemosensitivity in 80% (n = 16). The patients were evaluated for previous chemotherapy, residual volume of tumor, histologic type, and grade, and these were not statistically different between clinical responders and nonresponders. In vivo-in vitro correlations were made in 27 patients and yielded a predictive response of 13% and predictive resistance of 86% at 70% colony inhibition and 31% and 71% at 50% colony inhibition. Improved growth rates therefore did not result in better predictive correlations. The reported experience in ovarian cancer is summarized and the current status of the human tumor stem cell assay is reviewed. 相似文献
33.
Linda Lui Kalcina Ivana Pavlinac Dodig Renata Pecoti Sijana Demirovi Maja Vali Zoran oga 《Croatian medical journal》2022,63(3):299
AimTo construct a single-format questionnaire on sleep habits and mood before and during the COVID-19 pandemic in the general population.MethodsWe constructed the Split Sleep Questionnaire (SSQ) after a literature search of sleep, mood, and lifestyle questionnaires, and after a group of sleep medicine experts proposed and assessed questionnaire items as relevant/irrelevant. The study was performed during 2021 in 326 respondents distributed equally in all age categories. Respondents filled out the SSQ, the Pittsburgh Sleep Quality Index (PSQI), and State Trait Anxiety Inventory (STAI), and kept a seven-day sleep diary.ResultsWorkday and work-free day bedtime during the COVID-19 pandemic assessed with SSQ were comparable to the sleep diary assessment (P = 0.632 and P = 0.203, respectively), as was the workday waketime (P = 0.139). Work-free day waketime was significantly later than assessed in sleep diary (8:19 ± 1:52 vs 7:45 ± 1:20; P < 0.001). No difference in sleep latency was found between the SSQ and PSQI (P = 0.066). Cronbach alpha for Sleep Habits section was 0.819, and 0.89 for Mood section. Test-retest reliability ranged from 0.45 (P = 0.036) for work-free day bedtime during the pandemic to 0.779 (P < 0.001) for sleep latency before the pandemic.ConclusionThe SSQ provides a valid, reliable, and efficient screening tool for the assessment of sleep habits and associated factors in the general population during the COVID-19 pandemic.The COVID-19 pandemic, along with its multiple adverse effects on various aspects of mental health, has significantly affected sleep. Sleep habits alterations and newly developed sleep disturbances during the COVID-19 pandemic may influence the overall well-being and health (1). Since the beginning of the pandemic, several studies reported a delay in bedtimes and waketimes, and an associated shift in chronotype toward eveningness (2-5).Even though actigraphy and sleep diaries provide a valid and reliable assessment of sleep habits (6,7), to achieve the highest reliability and validity, these methods require an assessment during seven consecutive days including weekends (8). Daily reporting may be perceived by the respondents as an additional burden (6,9), a limitation that may be overcome by the use of single-administration questionnaires (9,10). Since sleep disturbances recognized in the first pandemic outbreak remained stable during new waves of the COVID-19 pandemic (5), single-administration questionnaires may enable screening of large population groups and an extended assessment of sleep disturbances during the pandemic.So far, validated sleep questionnaires have most often aimed at sleep disorders or symptoms associated with sleep disorders (9). Studies commonly report the Pittsburgh sleep Quality Index (PSQI) (11), which provides data on sleep duration, sleep disturbances, and sleep latency during the previous month. However, PSQI reflects mainly sleep quality on workdays (12), while not collecting information on sleep habits on weekends. The Sleep Timing Questionnaire (STQ) has been developed as an alternative to the sleep diary for the healthy adult population, showing good reliability and validity (10). Still, although sleep habits are associated with mood (13), social media use (14-16), learning time in students (17-19), sports or exercise (20), and symptoms of insomnia (21), the STQ does not assess variables such as mood and lifestyle habits.Large studies objectively assessing sleep with wearable devices have recognized sleep timing and sleep duration to be modifiable risk factors for adverse mental health during the current pandemic (22). Young adults are especially at risk for increased mood disorder symptoms, higher levels of perceived stress, and more common alcohol use during the pandemic (23). Even though mood disorders are often reported in pandemic studies on sleep habits, mood itself has been less commonly measured and associated with sleep parameters (24). A review of the literature showed a transactional relationship between mood and emotion (25), indicating that mood is characterized by longer duration than emotion (26). Mood is often assessed with the Brief Mood Introspection Scale (27), the Profile of Mood States (28), or the Visual Analogue Mood Scale (29). A relevant aspect of mood measurement is a hierarchical structure with two broad dimensions in positive and negative affect, and multiple specific states (30). Commonly used mood assessment scales evaluate the basic negative mood of fear/anxiety, sadness/depression, and anger/hostility, as well as at least one positive mood. Therefore, it has been strongly recommended that mood researchers assess a broad range of both positive and negative emotions (30).Linking mood changes and lifestyle habits during the pandemic has been relevant in order to recognize possible predictors of mood changes, especially due to a reported increase in depression (31). Since sleep is often intertwined with mood and lifestyle changes (31), we assumed that a single-format questionnaire comprehensively assessing these variables and sleep may be applicable and timely.The aim of this study was to construct a single-format Split Sleep Questionnaire (SSQ) comprehensively assessing sleep habits, lifestyle habits, and mood changes, as well as to evaluate its reliability and validity in the general population. Sleep habits were validated by using standard instruments such as sleep diary, PSQI, and STAI questionnaires as the measures of construct validity. Additionally, we aimed to assess the psychometric properties of the Mood section and to explore the effects of the COVID-19 pandemic on sleep habits and mood alterations in the general population of Croatia. 相似文献
34.
35.
36.
Nataša Mitrović Marina Zarić Dunja Drakulić Jelena Martinović Jean Sévigny Miloš Stanojlović Nadežda Nedeljković Ivana Grković 《Journal of molecular neuroscience : MN》2017,61(3):412-422
17β-Estradiol (E2) rapidly, by binding to membrane estrogen receptors, activates cell signaling cascades which induce formation of new dendritic spines in the hippocampus of males as in females, but the interaction with other metabolic processes, such as extracellular adenine nucleotides metabolism, are currently unknown. Extracellular adenine nucleotides play significant roles, controlling excitatory glutamatergic synapses and development of neural circuits and synaptic plasticity. Their precise regulation in the synaptic cleft is tightly controlled by ecto-nucleoside triphosphate diphosphohydrolase (NTPDase)/ecto-5′-nucleotidase (eN) enzyme chain. Therefore, we sought to clarify whether a single systemic injection of E2 in male rats is accompanied by changes in the expression of the pre- and postsynaptic proteins and downstream kinases linked to E2-induced synaptic rearrangement as well as alterations in NTPDase/eN pathway in the hippocampal synaptosomes. Obtained data showed activation of mammalian target of rapamycin and upregulation of key synaptic proteins necessary for spine formation, 24 h after systemic E2 administration. In E2-mediated conditions, we found downregulation of NTPDase1 and NTPDase2 and attenuation of adenine nucleotide hydrolysis by NTPDase/eN enzyme chain, without changes in NTPDase3 properties and augmentation of synaptic tissue-nonspecific alkaline phosphatase (TNAP) activity. Despite reduced NTPDase activities, increased TNAP activity probably prevents toxic accumulation of ATP in the extracellular milieu and also hydrolyzes accumulated ADP due to unchanged NTPDase3 activity. Thus, our initial evaluation supports idea of specific roles of different ectonucleotidases and their coordinated actions in E2-mediated spine remodeling and maintenance. 相似文献
37.
Seth Iwan Chia-Min Lin Christopher Perreault Kallol Chakrabarty Cheng-Chien Chen Yogesh Vohra Rostislav Hrubiak Guoyin Shen Nenad Velisavljevic 《Materials》2022,15(9)
The high-entropy transition metal borides containing a random distribution of five or more constituent metallic elements offer novel opportunities in designing materials that show crystalline phase stability, high strength, and thermal oxidation resistance under extreme conditions. We present a comprehensive theoretical and experimental investigation of prototypical high-entropy boride (HEB) materials such as (Hf, Mo, Nb, Ta, Ti)B2 and (Hf, Mo, Nb, Ta, Zr)B2 under extreme environments of pressures and temperatures. The theoretical tools include modeling elastic properties by special quasi-random structures that predict a bulk modulus of 288 GPa and a shear modulus of 215 GPa at ambient conditions. HEB samples were synthesized under high pressures and high temperatures and studied to 9.5 GPa and 2273 K in a large-volume pressure cell. The thermal equation of state measurement yielded a bulk modulus of 276 GPa, in excellent agreement with theory. The measured compressive yield strength by radial X-ray diffraction technique in a diamond anvil cell was 28 GPa at a pressure of 65 GPa, which is a significant fraction of the shear modulus at high pressures. The high compressive strength and phase stability of this material under high pressures and high temperatures make it an ideal candidate for application as a structural material in nuclear and aerospace fields. 相似文献
38.
Vitamin D,folate, and potential early lifecycle environmental origin of significant adult phenotypes
Mark Lucock Zo? Yates Charlotte Martin Jeong-Hwa Choi Lyndell Boyd Sa Tang Nenad Naumovski John Furst Paul Roach Nina Jablonski George Chaplin Martin Veysey 《Evolution, Medicine, and Public Health》2014,2014(1):69-91
Background and objectives: Vitamin D and folate are highly UV sensitive, and critical for maintaining health throughout the lifecycle. This study examines whether solar irradiance during the first trimester of pregnancy influences vitamin D receptor (VDR) and nuclear folate gene variant occurrence, and whether affected genes influence late-life biochemical/clinical phenotypes.Methodology: 228 subjects were examined for periconceptional exposure to solar irradiance, variation in vitamin D/folate genes (polymerase chain reaction (PCR)), dietary intake (food frequency questionnaire (FFQ)) and important adult biochemical/clinical phenotypes.Results: Periconceptional solar irradiance was associated with VDR-BsmI (P = 0.0008wk7), TaqI (P = 0.0014wk7) and EcoRV (P = 0.0030wk6) variant occurrence between post-conceptional weeks 6–8, a period when ossification begins. Similar effects were detected for other VDR gene polymorphisms. Periconceptional solar irradiance was also associated with 19 bp del-DHFR (P = 0.0025wk6), and to a lesser extent C1420T-SHMT (P = 0.0249wk6), a folate-critical time during embryogenesis. These same genes were associated with several late-life phenotypes: VDR-BsmI, TaqI and ApaI determined the relationship between dietary vitamin D and both insulin (P < 0.0001/BB, 0.0007/tt and 0.0173/AA, respectively) and systolic blood pressure (P = 0.0290/Bb, 0.0299/Tt and 0.0412/AA, respectively), making them important early and late in the lifecycle. While these and other phenotype associations were found for the VDR variants, folate polymorphism associations in later-life were limited to C1420T-SHMT (P = 0.0037 and 0.0297 for fasting blood glucose and HbA1c levels, respectively). We additionally report nutrient–gene relationships with body mass index, thiol/folate metabolome, cognition, depression and hypertension. Furthermore, photoperiod at conception influenced occurrence of VDR-Tru9I and 2R3R-TS genotypes (P = 0.0120 and 0.0360, respectively).Conclusions and implications: Findings identify environmental and nutritional agents that may interact to modify gene–phenotype relationships across the lifecycle, offering new insight into human ecology. This includes factors related to both disease aetiology and the evolution of skin pigmentation. 相似文献
39.