全文获取类型
收费全文 | 8121篇 |
免费 | 485篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 68篇 |
儿科学 | 282篇 |
妇产科学 | 192篇 |
基础医学 | 1245篇 |
口腔科学 | 173篇 |
临床医学 | 719篇 |
内科学 | 1683篇 |
皮肤病学 | 246篇 |
神经病学 | 860篇 |
特种医学 | 167篇 |
外科学 | 623篇 |
综合类 | 67篇 |
一般理论 | 3篇 |
预防医学 | 668篇 |
眼科学 | 185篇 |
药学 | 770篇 |
中国医学 | 11篇 |
肿瘤学 | 679篇 |
出版年
2024年 | 8篇 |
2023年 | 65篇 |
2022年 | 215篇 |
2021年 | 350篇 |
2020年 | 203篇 |
2019年 | 215篇 |
2018年 | 280篇 |
2017年 | 195篇 |
2016年 | 275篇 |
2015年 | 273篇 |
2014年 | 318篇 |
2013年 | 462篇 |
2012年 | 688篇 |
2011年 | 668篇 |
2010年 | 351篇 |
2009年 | 301篇 |
2008年 | 481篇 |
2007年 | 524篇 |
2006年 | 500篇 |
2005年 | 459篇 |
2004年 | 481篇 |
2003年 | 407篇 |
2002年 | 382篇 |
2001年 | 48篇 |
2000年 | 45篇 |
1999年 | 43篇 |
1998年 | 50篇 |
1997年 | 51篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 26篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 6篇 |
排序方式: 共有8641条查询结果,搜索用时 15 毫秒
101.
Kalache KD Mkhitaryan M Bamberg C Roehr CC Wauer R Mau H Bollmann R 《Prenatal diagnosis》2007,27(4):322-326
OBJECTIVES: The purpose of this retrospective study was to determine whether objective assessment of cardiac shifting on two-dimensional ultrasonography can predict postnatal outcome in fetuses with isolated left-sided congenital diaphragmatic hernia (CDH). MATERIALS AND METHODS: Still images at the level of the four-chamber view were obtained in 23 fetuses with left-sided CDH. A group of 12 fetuses (3 non-survivors and 9 survivors) were examined at two periods, between 20 and 30 weeks and between 31 and 40 weeks. A further 11 fetuses (2 non-survivors and 9 survivors) were examined between 31 and 40 weeks. Fetal heart axis and position were determined manually and associated with postnatal outcome. RESULTS: The cardiac axis remained constant in the 9 survivors (15.5 +/- 3.2 versus 17.2 +/- 3.3, p = 0.71) and 3 non-survivors (19.0 +/- 11.5 versus 18.5 +/- 11.8, p = 0.97). There was no statistical difference between the 9 survivors and 3 non-survivors at the two periods. Cardiac displacement remained constant in the 9 survivors (0.2 +/- 0.02 versus 0.2 +/- 0.02, p = 0.32) but increased significantly in the 3 non-survivors (0.2 +/- 0.04 versus 0.4 +/- 0.02, p = 0.015). The difference between survivors and non-survivors was statistically significant between the18 survivors and 5 non-survivors examined between 31 and 40 weeks of gestation (0.2 +/- 0.02 versus 0.4 +/- 0.02, p = 0.037). CONCLUSION: This study does not support the hypothesis that objective assessment of mediastinal shift in fetuses with left-sided CDH has a role in predicting postnatal outcome before fetal viability, which is when it would be more useful for counseling patients regarding whether to continue with the pregnancy or to opt for termination. 相似文献
102.
Agic A Xu H Altgassen C Noack F Wolfler MM Diedrich K Friedrich M Taylor RN Hornung D 《Reproductive sciences (Thousand Oaks, Calif.)》2007,14(5):486-497
The authors demonstrate expression of the vitamin D receptor (VDR) and its hydroxylases in the endometrium and ovaries of women with and without endometriosis and endometrial or ovarian cancer. Immunohistochemistry showed strong staining of the VDR in endometriosis and endometrial cancer, with the most intense staining in epithelial cells. The VDR mRNA was significantly increased in patients with endometrial and ovarian cancer compared to the control group. There was a significantly higher 1 alpha-hydroxylase expression in the endometrium of patients with endometriosis compared to healthy controls. The observed differences in VDR and 1 alpha -hydroxylase mRNA levels were maintained at the protein level. The authors found no differences in 25-OH vitamin D levels between the serum of patients with endometriosis (25.7 +/- 2.1 ng/mL, n = 46) and healthy controls (22.6 +/- 2.0 ng/mL, n = 33, P = .31). They hypothesize that vitamin D might influence the local activity of immune cells and cytokines thought to play important pathogenic roles in the development and maintenance of endometriosis. 相似文献
103.
Agata Oldzka Katarzyna Cichocka Konrad Woliski Matthias F. Melzig Monika E. Czerwiska 《Nutrients》2022,14(11)
Targeting pancreatic lipase and α-amylase by digestion-derived fractions of ethanolic-aqueous (60%, v/v) extract from Cornus mas fruit (CM) in relation to the control and prevention of metabolic disorders, including diabetes, was the first purpose of the present study. Taking into consideration the significance of bio-accessibility of compounds, we attempted to identify metabolites of CM after gastrointestinal digestion in vitro, as well as their kinetic changes upon gut microbiota treatment. The digestion of extract was simulated with digestive enzymes in vitro and human gut microbiota ex vivo (1 h, 3 h, 6 h, 24 h), followed by chromatographic analysis using the UHPLC-DAD-MSn method. The effect of fractions from gastrointestinal digestion in vitro on the activity of pancreatic lipase and α-amylase was studied with fluorescence-based assays. The gastric and intestinal fractions obtained after in vitro digestion of CM inhibited pancreatic lipase and α-amylase. Loganic acid as the main constituent of the extract was digested in the experimental conditions in contrast to cornuside. It was found in most analytes such as salivary, gastric, intestinal, and even colon (fecal slurry, FS) fractions. In all fractions, kaempferol hexoside and reduced forms of kaempferol, such as aromadendrin, and benzoic acid were assigned. The signals of tannins were detected in all fractions. Cornusiin A was tentatively assigned in the gastric fraction. The metabolites originating from kinetic analytes have been classified mainly as phenolic acids, hydrolyzable tannins, and flavonoids. Phenolic acids (protocatechuic acid, gallic acid), tannins (digalloylglucose, tri-O-galloyl-β-D-glucose), and flavonoids (aromadendrin, dihydroquercetin) were detected in the late phases of digestion in fecal slurry suspension. Cornuside was found in FS analyte after 3 h incubation. It was not detected in the samples after 6 and 24 h incubation with FS. In conclusion, cornuside, aromadendrin, and phenolic acids may be potentially bio-accessible compounds of CM. The presence of plants’ secondary metabolites in the intestinal fractions allows us to indicate them as responsible for decreasing glucose and lipid absorption. 相似文献
104.
Early nutrition plays a crucial role not only in providing essential nutrients for proper child development, but may also be an important step in creating desirable eating behaviors, which can be transmitted into adulthood. The aim of this study was to assess possible links between early feeding factors, such as breastfeeding, complementary feeding (timing and method) as well as types of complementary foods and mealtime environment during the first three months of complementary feeding and eating behaviors in children aged 1–3 years old. This cross-sectional, online survey involved 467 mothers of toddlers aged 1–3 years old from the whole of Poland. The questionnaire consisted of questions about early feeding and the Children’s Eating Behavior Questionnaire (CEBQ). The adjusted linear regression model revealed that longer duration of any breastfeeding was negatively related to enjoyment of food (EF), desire to drink (DD) and positively related to satiety responsiveness (SR) and slowness in eating (SE) subscales. Moreover, offering homemade complementary foods more often than commercial may be related to higher SR. Eating meals during distraction seems to be negatively associated with EF, and positively with DD and SE subscales. Our study highlights possible links between early feeding factors and toddlers’ eating behaviors, so further investigation, also including dietary factors, is needed. 相似文献
105.
Daniela Gerges Sebastian Kapps Esperanza Hernndez-Carralero Raimundo Freire Monika Aiad Sophie Schmidt Wolfgang Winnicki Thomas Reiter Sahra Pajenda Alice Schmidt Gere Sunder-Plassmann Ludwig Wagner 《Viruses》2022,14(6)
SARS-CoV-2 variants of concern (VOCs) have caused a significant increase in infections worldwide. Despite high vaccination rates in industrialized countries, the fourth VOC, Omicron, has outpaced the Delta variant and is causing breakthrough infections in individuals with two booster vaccinations. While the magnitude of morbidity and lethality is lower in Omicron, the infection rate and global spread are rapid. Using a specific IgG multipanel-ELISA with the spike protein’s receptor-binding domain (RBD) from recombinant Alpha, Gamma, Delta, and Omicron variants, sera from health-care workers from the Medical University of Vienna were tested pre-pandemic and post-vaccination (BNT162b2; ChAdOx1 nCoV-19). The cohort was continuously monitored by SARS-CoV-2 testing and commercial nucleocapsid IgG ELISA. RBD IgG ELISA showed significantly lower reactivity against the Omicron-RBD compared to the Alpha variant in all individuals (p < 0.001). IgG levels were independent of sex, but were significantly higher in BNT162b2 recipients <45 years of age for Alpha, Gamma, and Delta (p < 0.001; p = 0.040; p = 0.004, respectively). Pre-pandemic cross-reactive anti-Omicron IgG was detected in 31 individuals and was increased 8.78-fold after vaccination, regardless of vaccine type. The low anti-RBD Omicron IgG level could explain the breakthrough infections and their presence could also contribute to a milder COVID-19 course by cross-reactivity and broadening the adaptive immunity. 相似文献
106.
In this article, we present the concept of reading time regularity (RTR) as a measure to capture reading process dynamics. The first study is concerned with examining one of the assumptions of RTR, namely, that process measures of reading, such as eye movement fluctuations and fixation durations, exhibit higher regularity when contingent on sequentially structured information, such as texts. To test this, eye movements of 26 German native speakers were recorded during reading-unrelated and reading-related tasks. To analyze the data, we used recurrence quantification analysis and sample entropy analysis to quantify the degree of temporal structure in time series of gaze steps and fixation durations. The results showed that eye movements become more regular in reading compared to nonreading conditions. These effects were most prominent when calculated on the basis of gaze step data. In a second study, eye movements of 27 native speakers of German were recorded for five conditions with increasing linguistic information. The results replicate the findings of the first study, verifying that these effects are not due to mere differences in task instructions between conditions. Implications for the concept of RTR and for future studies using these metrics in reading research are discussed. 相似文献
107.
An ecologic study of nitrate in municipal drinking water and cancer incidence in Trnava District,Slovakia 总被引:16,自引:0,他引:16
Contamination of drinking water by nitrate is an evolving public health concern since nitrate can undergo endogenous reduction to nitrite, and nitrosation of nitrites can form N-nitroso compounds, which are potent carcinogens. We conducted an ecologic study to determine whether nitrate levels in drinking water were correlated with non-Hodgkin lymphoma and cancers of the digestive and urinary tracts in an agricultural district (Trnava District; population 237,000) of the Slovak Republic. Routinely collected nitrate data (1975-1995) for villages using public water supplies were computerized, and each village was categorized into low (0-10 mg/L), medium (10.1-20 mg/L), or high (20.1-50 mg/L) average levels of total nitrate in drinking water. Observed cases of cancer in each of these villages were ascertained through the district cancer registry for the time period 1986-1995. Standardized incidence ratios (SIRs) and 95% confidence intervals (CI) for all cancer and selected cancer sites were calculated by indirect standardization using age- and sex-specific incidence rates from the entire district. For all cancer in women, SIRs increased from villages with low (SIR=0.87; 95% CI 0.72-0.95) to medium (SIR=1.07; 95% CI 1.00-1.13) to high (SIR=1.14; 1.06-1.22) levels of nitrate (P for trend <0.001); there was a similar trend for all cancer in men from low (SIR=0.90; 95% CI 0.81-0.99) to medium (SIR=1.08, 95% CI 1.02-1.16), but not for high (SIR=0.94; 0.88-1.02), nitrate levels (P for trend <0.001). This pattern in the SIRs (from low to high nitrate level) was also seen for stomach cancer in women (0.81, 0.94, 1.24; P for trend=0.10), colorectal cancer in women (0.64, 1.11, 1.29; P for trend <0.001) and men (0.77, 0.99, 1.07; P for trend=0.051), and non-Hodgkin lymphoma in women (0.45, 0.90, 1.35; P for trend=0.13) and men (0.25, 1.66, and 1.09; P for trend=0.017). There were no associations for kidney or bladder cancer. These ecologic data support the hypothesis that there is a positive association between nitrate in drinking water and non-Hodgkin lymphoma and colorectal cancer. 相似文献
108.
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
109.
IntroductionRetroperitoneal fibrosis (RPF) is a rare disease associated with the formation of hard inflammatory and fibrous tissue in the retroperitoneum. Taking into consideration the fact that RPF is a rare disease with different subtypes, we compared the basal clinical and biochemical characteristics of the vascular and urorenal subtypes.Patients and methodsFrom January 2005 until December 2021, 27 patients were identified as vascular subtype (18 males) and 11 as urorenal subtype (9 males).ResultsPatients with a primary urorenal origin had significantly worse kidney function as reflected by serum creatinine and eGFR (both p < 0.001); they also had higher serum cholesterol (p < 0.01). Hypertension, diabetes, hyperlipidemia and nicotinism were significantly more prevalent in vascular subtype (all p < 0.001).ConclusionVascular subtype is more prevalent in our study with more cardiovascular risk factor present. Due to the diversity of symptoms, diagnosis of RPF becomes a challenge for specialists as well as therapy. 相似文献
110.
Psychometric properties of the apathy evaluation scale in patients with Parkinson's disease
下载免费PDF全文
![点击此处可从《International journal of methods in psychiatric research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ulrike Lueken Ricarda Evens Monika Balzer‐Geldsetzer Simon Baudrexel Richard Dodel Susanne Gräber‐Sultan Rüdiger Hilker‐Roggendorf Elke Kalbe Oliver Kaut Brit Mollenhauer Kathrin Reetz Eva Schäffer Nele Schmidt Jörg B. Schulz Annika Spottke Karsten Witt Katharina Linse Alexander Storch Oliver Riedel 《International journal of methods in psychiatric research》2017,26(4)
Parkinson's disease (PD) frequently entails non‐motor symptoms, worsening the course of the disease. Apathy is one of the core neuropsychiatric symptoms that has been investigated in recent years; research is however hampered by the limited availability of well‐evaluated apathy scales for these patients. We evaluated the psychometric properties of the Apathy Evaluation Scale (AES) in a sample of PD patients. Psychometric properties, convergent and discriminant validity and sensitivity/specificity were evaluated in patients with (n = 582) or without dementia/depression (n = 339). Internal consistency was high in the entire sample as well as in patients without dementia/depression. Correlations were moderate for convergent validity (UPDRS I item 4: motivation). While apathy could be differentiated from cognitive decline, it was related to depression (Geriatric Depression Scale, GDS‐15). The overall classification accuracy based on the UPDRS I item 4 was comparable for AES and GDS scores. The AES exhibits good psychometric properties in PD patients with and without dementia and/or depression. Commonly used screenings on the presence of apathy had low detection rates compared to the AES and reflected both apathetic and depressive symptoms. Psychometric evaluation of available instruments will support further research on the clinical relevance of apathy for disease progression and treatment approaches in PD patients. 相似文献