全文获取类型
收费全文 | 5327篇 |
免费 | 398篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 57篇 |
儿科学 | 117篇 |
妇产科学 | 195篇 |
基础医学 | 663篇 |
口腔科学 | 156篇 |
临床医学 | 576篇 |
内科学 | 1291篇 |
皮肤病学 | 83篇 |
神经病学 | 327篇 |
特种医学 | 343篇 |
外科学 | 690篇 |
综合类 | 130篇 |
预防医学 | 189篇 |
眼科学 | 155篇 |
药学 | 365篇 |
中国医学 | 37篇 |
肿瘤学 | 398篇 |
出版年
2023年 | 21篇 |
2022年 | 63篇 |
2021年 | 110篇 |
2020年 | 72篇 |
2019年 | 89篇 |
2018年 | 142篇 |
2017年 | 103篇 |
2016年 | 123篇 |
2015年 | 235篇 |
2014年 | 204篇 |
2013年 | 229篇 |
2012年 | 379篇 |
2011年 | 364篇 |
2010年 | 227篇 |
2009年 | 159篇 |
2008年 | 279篇 |
2007年 | 283篇 |
2006年 | 265篇 |
2005年 | 245篇 |
2004年 | 235篇 |
2003年 | 292篇 |
2002年 | 256篇 |
2001年 | 192篇 |
2000年 | 167篇 |
1999年 | 126篇 |
1998年 | 56篇 |
1997年 | 38篇 |
1996年 | 39篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 34篇 |
1992年 | 93篇 |
1991年 | 70篇 |
1990年 | 63篇 |
1989年 | 57篇 |
1988年 | 55篇 |
1987年 | 58篇 |
1986年 | 49篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有5772条查询结果,搜索用时 5 毫秒
101.
Angela L DRozario Camilla M Hoyos Keith K H Wong Gunnar Unger Jong Won Kim Andrew Vakulin Chien-Hui Kao Sharon L Naismith Delwyn J Bartlett Ronald R Grunstein 《Sleep》2022,45(6)
Study ObjectivesUntreated obstructive sleep apnea (OSA) is associated with cognitive deficits and altered brain electrophysiology. We evaluated the effect of continuous positive airway pressure (CPAP) treatment on quantitative sleep electroencephalogram (EEG) measures and cognitive function.MethodsWe studied 167 patients with OSA (age 50 ± 13, AHI 35.0 ± 26.8) before and after 6 months of CPAP. Cognitive tests assessed working memory, sustained attention, visuospatial scanning, and executive function. All participants underwent overnight polysomnography at baseline and after CPAP. Power spectral analysis was performed on EEG data (C3-M2) in a sub-set of 90 participants. Relative delta EEG power and sigma power in NREM and EEG slowing in REM were calculated. Spindle densities (events/min) in N2 were also derived using automated spindle event detection. All outcomes were analysed as change from baseline.ResultsCognitive function across all cognitive domains improved after six months of CPAP. In our sub-set, increased relative delta power (p < .0001) and reduced sigma power (p = .001) during NREM were observed after the 6-month treatment period. Overall, fast and slow sleep spindle densities during N2 were increased after treatment.ConclusionsCognitive performance was improved and sleep EEG features were enhanced when assessing the effects of CPAP. These findings suggest the reversibility of cognitive deficits and altered brain electrophysiology observed in untreated OSA following six months of treatment. 相似文献
102.
Animal studies have demonstrated that ozone exposure can induce lung tumors. Recent epidemiological studies have also shown that increased ozone exposure is associated with a greater risk of lung cancer. This study used single-cell gel electrophoresis (the Comet assay) and flow cytometry to investigate DNA damage in A549 cells exposed to ozone levels below the current ambient standard. Cells were exposed to ozone at levels of 0, 60, 80, and 120 ppb, and then DNA single-strand breaks and 8-oxoguanine levels were measured. Additionally, the formamidopyrimidine glycosylase (Fpg) repair enzyme was added to the Comet assay to enhance detection of oxidative damage. Vitamins C and E were also added to determine their inhibitory effects on ozone-induced 8-oxoguanine. Measurements of tail length, tail intensity, and tail moment of the Comet assay were shown to correlate with each other. However, tail moment appeared to be more sensitive than the other two indicators in detecting DNA single-strand breaks. Tail moments of cells exposed to 80 and 120 ppb of ozone were significantly higher than those exposed to 0 ppb (P<0.05). These three indicators of DNA single-strand breaks with Fpg were shown to be increased and more sensitive than those without Fpg. After Fpg was introduced, the tail moments at ozone levels of 60, 80, and 120 ppb were significantly higher than those at 0 ppb (P<0.05). Furthermore, 8-oxoguanine levels, determined by fluorescence intensity, at 80 and 120 ppb of ozone exposure were significantly higher than the level at 0 ppb. Pretreatment with vitamins C and E reduced the 8-oxoguanine levels caused by ozone. We conclude that ozone levels below current ambient standards may induce DNA breaks and oxidative DNA damage. Moreover, the Fpg repair enzyme in the Comet assay can increase the sensitivity of oxidative damage detection in vitro. 相似文献
103.
Mei-Kang Yuan Ju-Wen Kao Wen-Tung Wu Chiy-Rong Chen Chi-I Chang Yu-Jen Wu 《Pharmaceutical biology》2022,60(1):1214
ContextMomordica charantia L. (Cucurbitaceae), known as bitter melon, is an edible fruit cultivated in the tropics. In this study, an active compound, 5β,19-epoxycucurbita-6,23(E)-diene-3β,19(R),25-triol (ECDT), isolated from M. charantia was investigated in regard to its cytotoxic effect on human hepatocellular carcinoma (HCC) cells.ObjectiveTo examine the mechanisms of ECDT-induced apoptosis in HCC cells.Materials and methodsThe inhibitive activity of ECDT on HA22T HCC cells was examined by MTT assay, colony formation assay, wound healing assay, TUNEL/DAPI staining, annexin V-fluorescein isothiocyanate/propidium iodide (PI) staining and JC-1 dye. HA22T cells were treated with ECDT (5, 10, 15, 20 and 25 μM) for 24 h, and the molecular mechanism of cells apoptosis was examined by Western blot. Cells treated with vehicle DMSO were used as the negative control.ResultsECDT inhibited the cell proliferation of HA22T cells in a dose-dependent manner. Flow cytometry showed that ECDT treatment at 10–20 μM increased early apoptosis by 10–14% and late apoptosis by 2–5%. Western blot revealed that ECDT treatment activated the mitochondrial-dependent apoptotic pathway, and ECDT-induced apoptosis was mediated by the caspase signalling pathway and activation of JNK and p38MAPK. Pre-treatment of cells with MAPK inhibitors (SB203580 or SP600125) reversed the ECDT-induced cell death, which further supported the involvement of the p38MAPK and JNK pathways.Discussion and conclusionsOur results indicated that ECDT can induce apoptosis through the p38MAPK and JNK pathways in HA22T cells. The findings suggested that ECDT has a valuable anticancer property with the potential to be developed as a new chemotherapeutic agent for the treatment of HCC. 相似文献
104.
o-Benzyl-p-chlorophenol (BCP) is widely used as a broad spectrum disinfectant. Treatment of male Fischer 344 rats with BCP resulted in an increase in cytochrome P-450 content and an accompanying decrease in aryl hydrocarbon hydroxylase (AHH) activity in both liver and kidney microsomes. Several other drug-metabolizing enzymes were not affected by BCP treatment. However, in kidney, BCP induced NADPH-cytochrome c reductase and uridine diphosphate glucuronyl transferase activities and caused a small increase in total cytochrome P-450 content and glutathione concentration. The cytochrome P-450 isozymes induced by BCP were fractionated by high pressure liquid chromatography (HPLC). The HPLC profile following BCP treatment most closely resembled that seen after phenobarbital. Using an immunoblotting procedure and a radioimmunoassay, it was shown that the increase in cytochrome P-450 content in the liver after BCP treatment was, in part, due to an increase in the phenobarbital-inducible isozymes, P-450b + e. In the kidney, the increase in total cytochrome P-450 content after BCP exposure was not due to an increase in P-450b + e. The decrease in AHH activity appeared to be caused by noncompetitive inhibition of constitutive AHH activity by BCP. BCP also inhibited benzphetamine demethylation, although to a lesser extent. The failure to observe an increase in benzphetamine demethylase activity in vivo, despite the induction of P-450b, was probably due to the concomitant induction and inhibition of drug-metabolizing enzymes by BCP. 相似文献
105.
Andrew S Kao Kayla St Claire Lisa M Bedford Darius R Mehregan Aleodor A Andea David Kouba 《International journal of clinical and experimental pathology》2022,15(4):201
Nevoid and myxoid melanoma are rare variants of melanoma; association of the two is a unique finding. Nevoid melanoma is characterized by morphologic resemblance to a nevus, whereas myxoid melanoma demonstrates a basophilic mucinous matrix. We present an atypical case of a melanoma progressing from a nevoid melanocytoma with myxoid changes. A 78-year-old female presented with a pigmented growth on her right thigh. Biopsy demonstrated a biphenotypic melanocytic proliferation composed of a nodule showing epithelioid melanocytes with enlarged nuclei, prominent nucleoli, lack of maturation, and abundant amphophilic cytoplasm with a rare mitotic figure. These findings were suggestive of melanoma along with a nevoid dermal component and myxoid stroma. FISH testing revealed a homozygous loss of 9p21 in the atypical component. SNP-microarray from the nevoid component demonstrated three abnormalities including a gain of whole chromosome 8, as well as loss of a copy of nearly an entire chromosome 9 and 16q most consistent with a melanocytoma. 相似文献
106.
Hao-Wei Chen Yu-Chen Chen Jung-Ting Lee Frances M. Yang Chung-Yao Kao Yii-Her Chou Ting-Yin Chu Yung-Shun Juan Wen-Jeng Wu 《Nutrients》2022,14(9)
There is a great need for a diagnostic tool using simple clinical information collected from patients to diagnose uric acid (UA) stones in nephrolithiasis. We built a predictive model making use of machine learning (ML) methodologies entering simple parameters easily obtained at the initial clinical visit. Socio-demographic, health, and clinical data from two cohorts (A and B), both diagnosed with nephrolithiasis, one between 2012 and 2016 and the other between June and December 2020, were collected before nephrolithiasis treatment. A ML-based model for predicting UA stones in nephrolithiasis was developed using eight simple parameters—sex, age, gout, diabetes mellitus, body mass index, estimated glomerular filtration rate, bacteriuria, and urine pH. Data from Cohort A were used for model training and validation (ratio 3:2), while data from Cohort B were used only for validation. One hundred and forty-six (13.3%) out of 1098 patients in Cohort A and 3 (4.23%) out of 71 patients in Cohort B had pure UA stones. For Cohort A, our model achieved a validation AUC (area under ROC curve) of 0.842, with 0.8475 sensitivity and 0.748 specificity. For Cohort B, our model achieved 0.936 AUC, with 1.0 sensitivity, and 0.912 specificity. This ML-based model provides a convenient and reliable method for diagnosing urolithiasis. Using only eight readily available clinical parameters, including information about metabolic disorder and obesity, it distinguished pure uric acid stones from other stones before treatment. 相似文献
107.
①目的观察恶性肿瘤病人红细胞免疫功能、T淋巴细胞亚群和血清可溶性白细胞介素-2受体(sIL-2R)水平的变化。②方法采用红细胞受体花环试验、碱性磷酸酶抗碱性磷酸酶(APAAP)法及ELISA双抗体夹心法检测了66例中晚期恶性肿瘤病人及36例健康人红细胞免疫功能、T淋巴细胞亚群CD4,CD8和sIL-2R水平的变化,③结果中晚期恶性肿瘤病人红细胞C3b受体花环率(E-C3bRR)、CD4及CD4/CD8明显降低,免疫复合物花环率、CD8及sIL-2R均明显升高,与对照组比较差异有显著性(t=5.36-131.52,P均<0.001);E-C3bRR与CD4,CD4/CD8呈正相关(r=0.409-0.527,P均<0.001),与CD8,sIL-2R呈负相关(r=-0.395--0.420,P均<0.001);sIL-2P<0.001),④结论中晚期恶性肿瘤病人红细胞免疫功能与T淋巴细胞亚群和sIL-2R明显异常。 相似文献
108.
Hankyu Cho Solaiman Tarafder Michael Fogge Kristy Kao 《Connective tissue research》2016,57(6):488-495
ABSTRACTPurpose/Aim: Cementogenesis is a critical step in periodontal tissue regeneration given the essential role of cementum in anchoring teeth to the alveolar bone. This study is designed to achieve integrated cementum formation on the root surfaces of human teeth using growth factor–releasing scaffolds with periodontal ligament stem/progenitor cells (PDLSCs). Materials and methods: Human PDLSCs were sorted by CD146 expression, and characterized using CFU-F assay and induced multi-lineage differentiation. Polycaprolactone scaffolds were fabricated using 3D printing, embedded with poly(lactic-co-glycolic acids) (PLGA) microspheres encapsulating connective tissue growth factor (CTGF), bone morphogenetic protein-2 (BMP-2), or bone morphogenetic protein-7 (BMP-7). After removing cementum on human tooth roots, PDLSC-seeded scaffolds were placed on the exposed dentin surface. After 6-week culture with cementogenic/osteogenic medium, cementum formation and integration were evaluated by histomorphometric analysis, immunofluorescence, and qRT-PCR. Results: Periodontal ligament (PDL) cells sorted by CD146 and single-cell clones show a superior clonogenecity and multipotency as compared with heterogeneous populations. After 6 weeks, all the growth factor–delivered groups showed resurfacing of dentin with a newly formed cementum-like layer as compared with control. BMP-2 and BMP-7 showed de novo formation of tissue layers significantly thicker than all the other groups, whereas CTGF and BMP-7 resulted in significantly improved integration on the dentin surface. The de novo mineralized tissue layer seen in BMP-7-treated samples expressed cementum matrix protein 1 (CEMP1). Consistently, BMP-7 showed a significant increase in CEMP1 mRNA expression. Conclusion: Our findings represent important progress in stem cell–based cementum regeneration as an essential part of periodontium regeneration. 相似文献
109.
Jeon‐Hor Chen Wei‐Fan Pan Julian Kao Jocelyn Lu Li‐Kuang Chen Chih‐Chen Kuo Chih‐Kai Chang Wen‐Pin Chen Christine E. McLaren Shadfar Bahri Rita S. Mehta Min‐Ying Su 《NMR in biomedicine》2013,26(12):1705-1713
The aim of this study was to evaluate the change of breast density in the normal breast of patients receiving neoadjuvant chemotherapy (NAC). Forty‐four breast cancer patients were studied. MRI acquisition was performed before treatment (baseline), and 4 and 12 weeks after treatment. A computer‐algorithm‐based program was used to segment breast tissue and calculate breast volume (BV), fibroglandular tissue volume (FV), and percent density (PD) (the ratio of FV over BV × 100%). The reduction of FV and PD after treatment was compared with baseline using paired t‐tests with a Bonferroni–Holm correction. The association of density reduction with age was analyzed. FV and PD after NAC showed significant decreases compared with the baseline. FV was 110.0 ml (67.2, 189.8) (geometric mean (interquartile range)) at baseline, 104.3 ml (66.6, 164.4) after 4 weeks (p < 0.0001), and 94.7 ml (60.2, 144.4) after 12 weeks (comparison with baseline, p < 0.0001; comparison with 4 weeks, p = 0.016). PD was 11.2% (6.4, 22.4) at baseline, 10.6% (6.6, 20.3) after 4 weeks (p < 0.0001), and 9.7% (6.2, 17.9) after 12 weeks (comparison with baseline, p = 0.0001; comparison with 4 weeks, p = 0.018). Younger patients tended to show a higher density reduction, but overall correlation with age was only moderate (r = 0.28 for FV, p = 0.07, and r = 0.52 for PD, p = 0.0003). Our study showed that breast density measured from MR images acquired at 3T MR can be accurately quantified using a robust computer‐aided algorithm based on non‐parametric non‐uniformity normalization (N3) and an adaptive fuzzy C‐means algorithm. Similar to doxorubicin and cyclophosphamide regimens, the taxane‐based NAC regimen also caused density atrophy in the normal breast and showed reduction in FV and PD. The effect of breast density reduction was age related and duration related. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
110.