全文获取类型
收费全文 | 1281篇 |
免费 | 64篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 67篇 |
儿科学 | 16篇 |
妇产科学 | 68篇 |
基础医学 | 173篇 |
口腔科学 | 14篇 |
临床医学 | 95篇 |
内科学 | 305篇 |
皮肤病学 | 13篇 |
神经病学 | 83篇 |
特种医学 | 14篇 |
外科学 | 219篇 |
综合类 | 13篇 |
预防医学 | 68篇 |
眼科学 | 7篇 |
药学 | 85篇 |
中国医学 | 3篇 |
肿瘤学 | 108篇 |
出版年
2023年 | 9篇 |
2022年 | 32篇 |
2021年 | 48篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 19篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 44篇 |
2013年 | 52篇 |
2012年 | 77篇 |
2011年 | 70篇 |
2010年 | 50篇 |
2009年 | 43篇 |
2008年 | 46篇 |
2007年 | 70篇 |
2006年 | 93篇 |
2005年 | 79篇 |
2004年 | 82篇 |
2003年 | 122篇 |
2002年 | 83篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 7篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1965年 | 3篇 |
排序方式: 共有1351条查询结果,搜索用时 15 毫秒
1.
Konrad Matyja Anna Małachowska-Jutsz Anna K. Mazur Kazimierz Grabas 《Ecotoxicology (London, England)》2016,25(5):924-939
Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times. 相似文献
2.
3.
4.
5.
The present state of knowledge on the importance of calcium ions and inositol phospholipids in the metabolic changes associated with early stages of platelet activation is outlined, with stress laid in the biochemical mechanisms of intracellular rise of calcium ion concentration. The metabolism of inositol phospholipids is briefly discussed stressing the importance of the metabolites of these phospholipids--1,2-diacylglycerol and 1,4,5-inositol triphosphate which are of key importance in the transfer of information between platelet membrane and intracellular structures. 相似文献
6.
Korniszewski L Arbuckle S Kozlowski K 《American journal of medical genetics. Part A》2003,(4):343-349
A number of more or less distinct entities with low birth weight and abnormal radiographic appearances have been identified. We studied two sisters who were unusual because of severe intrauterine growth restriction, absence of growth after birth, decrease of pre- and postnatal spontaneous mobility, and early fatal outcome. The chondro-osseous morphology documented a distinctive osteochondrodysplasia. The radiographic examination was superficially similar to gracile bone dysplasias but was inconsistent with any known types of this group. These two patients appear to have a unique gracile bone dysplasia. 相似文献
7.
Ziora D Sielska-Spytek E Dworniczak S Oklek K Kozielski J 《Pneumonologia i alergologia polska》2002,70(9-10):458-467
The purpose of this study was comparison of VEGF (vascular endothelial growth factor) levels in serum and pleural fluid and estimation of this test usefulness in diagnosis of pleural effusions. VEGF levels were measured by ELISA method in 68 patients (45 males and 23 females) aged 19-81 years. By Light's criteria in 16 cases transudate and in 52 cases exudate was recognized. By means of fluid cytology, pleural biopsy, microbiology or thoracoscopy in 10 cases pleural metastases from distant organs, in 15 cases coexisting pulmonary neoplasm, in 11 cases mesothelioma and in 16 cases tuberculosis were determined as a cause of fluid accumulation in pleural space. The mean VEGF levels were significantly higher (p < 0.001) in patients with exudates than in patients with transudates (3833 pg/ml and 325 pg/ml respectively). Based on likelihood ratios analysis, as a cut off value in differentiation of exudates and transudates a value 700 pg/ml was accepted. The sensitivity of this test was 75% and the specificity 93% and likelihood ratio (LR) 12.5. The mean VEGF level in exudates was seven times higher than mean VEGF level in serum (3833 pg/ml and 573 pg/ml respectively). Mean VEGF levels in malignant exudates (4615 pg/ml) were significantly higher than in tuberculous exudates (2073 pg/ml). As a cut off value in differentiation between malignant and tuberculous exudates a value of 4500 pg/ml was accepted. We conclude that our results suggests the local VEGF production in pleural cavity and the significant role of this cytokine in pleural exudates accumulations and also suggests the usefulness of VEGF estimation in pleural fluid in differentiation transudates from exudates and malignant from tuberculous pleural fluids. 相似文献
8.
Zieliński J Czajkowska-Malinowska M Sankowski Z Kisło A Krawczyk K Skucha W Zalewska A Remiszewski W Kachel T Cynowska B Jedrzejczak M Lichota I Czechowska U Trawińska E Bednarek M 《Pneumonologia i alergologia polska》2000,68(5-6):217-225
COPD is the most frequent chronic lung disease in Poland. The disease is however under-diagnosed, especially at the early stages. The aim of the study was to assess the efficacy of spirometric screening for COPD in middle aged smokers. Informations on causes and symptoms of COPD were disseminated in mass media in 14 large cities. Subject aged over 39 and with smoking history of > 10 packyears were invited for a free spirometry in local chest clinic. However, everyone attending had the spirometry performed. Spirometry was performed according to ATS recommendations. Airway obstruction (AO) was diagnosed when FEV1/FVC < 85% of N and categorised as mild (FEV1 > 70% of N), moderate (FEV1 50-69% of N) or severe (FEV1 < 50% of N). Spirometry was accompanied by an antismoking advice. RESULTS: 12.781 subjects were screened (mean age 52 +/- 12 years, 57% males). In 8.269 subjects who complied with inclusion criteria AO was diagnosed in 29.8% (mild in 10.9%, moderate in 12% and severe in 6.9%). In smokers < 40 years of age and a history of < 10 packyears AO was found in 8.8% (mild in 6.0%, moderate in 1.8% and severe in 1.0%). CONCLUSION: Mass spirometry is an effective and easy method for early detection of COPD. 相似文献
9.
In vivo, RFX5 binds differently to the human leucocyte antigen-E, -F, and -G gene promoters and participates in HLA class I protein expression in a cell type-dependent manner 总被引:4,自引:0,他引:4 下载免费PDF全文
Rousseau P Masternak K Krawczyk M Reith W Dausset J Carosella ED Moreau P 《Immunology》2004,111(1):53-65
10.
Sina Schwarzkopf Adalbert Krawczyk Dietmar Knop Hannes Klump Andreas Heinold Falko M. Heinemann Laura Thümmler Christian Temme Marianne Breyer Oliver Witzke Ulf Dittmer Veronika Lenz Peter A. Horn Monika Lindemann 《Emerging infectious diseases》2021,27(1):122
We investigated immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among a group of convalescent, potential blood donors in Germany who had PCR-confirmed SARS-CoV-2 infection. Sixty days after onset of symptoms, 13/78 (17%) study participants had borderline or negative results to an ELISA detecting IgG against the S1 protein of SARS-CoV-2. We analyzed participants with PCR-confirmed infection who had strong antibody responses (ratio >3) as positive controls and participants without symptoms of SARS-CoV-2 infection and without household contact with infected patients as negative controls. Using interferon-γ ELISpot, we observed that 78% of PCR-positive volunteers with undetectable antibodies showed T cell immunity against SARS-CoV-2. We observed a similar frequency (80%) of T-cell immunity in convalescent donors with strong antibody responses but did not detect immunity in negative controls. We concluded that, in convalescent patients with undetectable SARS-CoV-2 IgG, immunity may be mediated through T cells. 相似文献