全文获取类型
收费全文 | 2695篇 |
免费 | 260篇 |
国内免费 | 10篇 |
专业分类
2965篇 |
出版年
2024年 | 6篇 |
2023年 | 11篇 |
2022年 | 33篇 |
2021年 | 53篇 |
2020年 | 38篇 |
2019年 | 52篇 |
2018年 | 57篇 |
2017年 | 41篇 |
2016年 | 71篇 |
2015年 | 143篇 |
2014年 | 172篇 |
2013年 | 203篇 |
2012年 | 228篇 |
2011年 | 223篇 |
2010年 | 138篇 |
2009年 | 138篇 |
2008年 | 150篇 |
2007年 | 141篇 |
2006年 | 142篇 |
2005年 | 121篇 |
2004年 | 119篇 |
2003年 | 77篇 |
2002年 | 93篇 |
2001年 | 63篇 |
2000年 | 58篇 |
1999年 | 52篇 |
1998年 | 33篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1972年 | 5篇 |
排序方式: 共有2965条查询结果,搜索用时 15 毫秒
991.
Lin Li Chengyan Li Ping Pan Xiaoli Chen Xiaoke Wu Ernest Hung Yu Ng Dongzi Yang 《PloS one》2015,10(12)
Objective
To evaluate the effects of berberine on the menstrual pattern, ovulation rate, hormonal and metabolic profiles in anovulatory Chinese women with polycystic ovary syndrome.Methods
Berberine 0.4 g three times per day was given for four months to 102 anovulatory Chinese women with polycystic ovary syndrome. The menstrual pattern, ovulation rate, hormonal and metabolic profiles were compared before and after the berberine treatment. Ovulation was confirmed by serum progesterone level ≥10ng/ml.Results
A total of 98 of 102 subjects (96.1%) completed the four month treatment, including 69 (70.4%, 69/98) normal weight and 29 (29.6%, 29/98) overweight/obese. Fourteen women (14.3%, 14/98) had regained regular menses after berberine treatment and there was no significant difference between normal weight and overweight/obese groups. The ovulation rate was 25.0% over four months in the whole group, 22.5% in the normal weight group and 31.0% in the overweight/obese group. Sex hormone binding globulin, insulin resistance, total cholesterol, total triglyceride and low-density lipoprotein cholesterol decreased after berberine treatment in the normal weight group only.Conclusions
Our study found that administration of berberine alone may improve the menstrual pattern and ovulation rate in anovulatory Chinese women with polycystic ovary syndrome. Berberine can also decrease sex hormone binding globulin, insulin resistance, total cholesterol, triglycerides and low-density lipoprotein cholesterol in normal weight polycystic ovary syndrome women.Trial Registration
Chictr.org ChiCTR-OO-13003943 相似文献992.
Yun-Ping Lim Cheng-Li Lin Yen-Ning Lin Wei-Chih Ma Wei-Cheng Chen Dong-Zong Hung Chia-Hung Kao 《PloS one》2015,10(1)
BackgroundThe objective of this study was to determine the association between the use of antiarrhythmic agents and the risk of malignant neoplasm of liver and intrahepatic bile ducts (MNLIHD).MethodsWe used the research database of the Taiwan National Health Insurance Program to conduct a population-based, case-control study. We identified 9944 patients with antiarrhythmic history who were first diagnosed as having MNLIHD between 2005 and 2010. We identified an additional 19,497 patients with antiarrhythmic history in the same period who did not develop MNLIHD and were frequency-matched using age, sex, and index year to form a control group. Five commercially available antiarrhythmic agents, amiodarone, mexiletine, propafenone, quinidine, and procainamide, were analyzed.ResultsThe adjusted odds ratio (OR) of MNLIHD was 1.60 (95% confidence interval [CI], 1.45–1.77) for amiodarone users versus nonamiodarone users. In subgroup analysis, amiodarone use was significantly associated with an increased risk of MNLIHD with an adjusted OR of 18.0 (95% CI, 15.7–20.5) for patients with comorbidities compared to an OR of 2.43 (95% CI, 1.92–3.06) for those without comorbidities. After adjustment for age, sex, statins, anti-diabetes medications, non-steroidal antiinflammatory drugs, propafenone use, quinidine use, and comorbidities, the ORs were 1.49, 1.66, and 1.79 for MNLIHD associated with annual mean defined daily doses of ≤30, 31–145, and >145, respectively.ConclusionsThe results of the present study indicated that amiodarone might be associated with the development of MNLIHD in a dose-dependent manner, particularly among patients with comorbidities. 相似文献
993.
Jing-Lan Liu Fen-Fen Chen Shun-Fu Chang Cheng-Nan Chen Jrhau Lung Cheng-Hsing Lo Fang-Hui Lee Ying-Chou Lu Chien-Hui Hung 《PloS one》2015,10(10)
Background
Beclin 1 and Beclin 2 are autophagy-related proteins that show similar amino acid sequences and domain structures. Beclin 1 established the first connection between autophagy and cancer. However, the role of Beclin 2 in cancer is unclear. The aims of this study were to analyze Beclin 1 and Beclin 2 expressions in oral cancer tissues and in cell lines, and to evaluate their possible roles in cancer progression.Methods
We investigated Beclin 1 and Beclin 2 expressions by immunohistochemistry in 195 cases of oral cancer. The prognostic roles of Beclin 1 and Beclin 2 were analyzed statistically. In vitro, overexpression and knockdown of Beclin proteins were performed on an oral cancer cell line, SAS. The immunofluorescence and autophagy flux assays confirmed that Beclin proteins were involved in autophagy. The impacts of Beclin 1 and Beclin 2 on autophagy and tumor growth were evaluated by conversion of LC3-I to LC3-II and by clonogenic assays, respectively.Results
Oral cancer tissues exhibited aberrant expressions of Beclin 1 and Beclin 2. The cytoplasmic Beclin 1 and Beclin 2 expressions were unrelated in oral cancer tissues. In survival analyses, high cytoplasmic Beclin 1 expression was associated with low disease specific survival, and negative nuclear Beclin 1 expression was associated with high recurrent free survival. Patients with either high or low cytoplasmic Beclin 2 expression had significantly lower overall survival and disease specific survival rates than those with moderate expression. In oral cancer cells, overexpression of either Beclin 1 or Beclin 2 led to autophagy activation and increased clonogenic survival; knockdown of Beclin 2 impaired autophagy and increased clonogenic survival.Conclusions
Our results indicated that distinct patterns of Beclin 1 and Beclin 2 were associated with aggressive clinical outcomes. Beclin 1 overexpression, as well as Beclin 2 overexpression and depletion, contributed to tumor growth. These findings suggest Beclin proteins are associated with tumorigenesis. 相似文献994.
Fuyong Wu Shengchun Wu Dan Deng Ming Hung Wong 《International journal of phytoremediation》2015,17(9):841-846
An arsenic hyperaccumulator, Pteris vittata L., is common in nature and could occur either on As-contaminated soils or on uncontaminated soils. However, it is not clear whether phosphate transporter play similar roles in As uptake and translocation in nonmetallicolous and metallicolous populations of P. vittata. Five populations were used to investigate effects of phosphate on arsenate uptake and translocation in the plants growing in 1.2 L 20% modified Hoagland's nutrient solution containing either 100 μM phosphate or no phosphate and 10 μM arsenate for 1, 2, 6, 12, 24 h, respectively. The results showed that the nonmetallicolous populations accumulated apparently more As in their fronds and roots than the metallicolous populations at both P supply levels. Phosphate significantly (P < 0.01) decreased frond and root concentrations of As during short time solution culture. In addition, the effects of phosphate on As translocation in P. vittata varied among different time-points during time-course hydroponics (1–24 h). The present results indicated that the inhibitory effect of phosphate on arsenate uptake was larger in the three nonmetallicolous populations than those in the two metallicolous populations of P. vittata. 相似文献
995.
996.
Tze-Fan Chao Yau-Huei Lai Chun-Ho Yun Chih-Hsuan Yen Kang-Ling Wang Yenn-Jiang Lin Shih-Lin Chang Li-Wei Lo Yu-Feng Hu Chung-Lieh Hung Jen-Yuan Kuo Hung-I Yeh Shih-Ann Chen 《PloS one》2014,9(5)
Objectives
Pericardial fat (PCF) may induce local inflammation and subsequent structural remodeling of the left atrium (LA). However, the adverse effects of PCF on LA are difficult to be evaluated and quantified. The atrial electromechanical interval determined by transthoracic echocardiogram was shown to be a convenient parameter which can reflect the process of LA remodeling. The goal of the present study was to investigate the association between the electromechanical interval and PCF.Methods and Results
A total of 337 patients with mean age of 51.9±9.0 years were enrolled. The electromechanical interval (PA-PDI) defined as the time interval from the initiation of the P wave deflection to the peak of the mitral inflow A wave on the pulse wave Doppler imaging was measured for every patient. The amount of PCF was determined by multi-detector computed tomography. The PA-PDI interval was significantly correlated with the amount of PCF (r = 0.641, p value <0.001). Graded prolongation of PA-PDI interval was observed across 3 groups of patients divided according to the tertile values of PCF. The AUC for the PA-PDI interval in predicting an increased amount of PCF (third tertile) was 0.796. At a cutoff value of 130 ms identified by the ROC curve, the sensitivity and specificity of PA-PDI interval in identifying patients with a highest tertile of PCF were 63.4% and 85.3%, respectively.Conclusions
The PA-PDI intervals were longer in patients with an increased amount of PCF. It may be a useful parameter to represent the degree of PCF-related atrial remodeling. 相似文献997.
Chih-Ming Hung Sergei V. Drovetski Robert M. Zink 《Molecular phylogenetics and evolution》2013,66(1):103-111
A previously published phylogeographic analysis of mtDNA sequences from the widespread Palearctic common rosefinch (Carpodacus erythrinus) suggested the existence of three recently diverged groups, corresponding to the Caucasus, central-western Eurasia, and northeastern Eurasia. We re-evaluated the mtDNA data using coalescence methods and added sequence data from a sex-linked gene. The mtDNA gene tree and SAMOVA supported the distinctiveness of the Caucasian group but not the other two groups. However, UPGMA clustering of mtDNA ΦST-values among populations recovered the three groups. The sex-linked gene tree recovered no phylogeographic signal, which was attributed to recent divergence and insufficient time for sorting of alleles. Overall, coalescence methods indicated a lack of gene flow among the three groups, and population expansion in the central-western and northeastern Eurasia groups. These three groups corresponded to named subspecies, further supporting their validity. A species distribution model revealed potential refugia at the Last Glacial Maximum. These three groups, which we hypothesized are in the early stages of speciation, provided an opportunity for testing tenets of ecological speciation. We showed that the early stages of speciation were not accompanied by ecological niche divergence, consistent with other avian studies. 相似文献
998.
Hung Manh Nguyen Peter J. Ralph Lázaro Marín-Guirao Mathieu Pernice Gabriele Procaccini 《Biological reviews of the Cambridge Philosophical Society》2021,96(5):2009-2030
Seagrasses are valuable sources of food and habitat for marine life and are one of Earth's most efficient carbon sinks. However, they are facing a global decline due to ocean warming and eutrophication. In the last decade, with the advent of new technology and molecular advances, there has been a dramatic increase in the number of studies focusing on the effects of ocean warming on seagrasses. Here, we provide a comprehensive review of the future of seagrasses in an era of ocean warming. We have gathered information from published studies to identify potential commonalities in the effects of warming and the responses of seagrasses across four distinct levels: molecular, biochemical/physiological, morphological/population, and ecosystem/planetary. To date, we know that although warming strongly affects seagrasses at all four levels, seagrass responses diverge amongst species, populations, and over depths. Furthermore, warming alters seagrass distribution causing massive die-offs in some seagrass populations, whilst also causing tropicalization and migration of temperate species. In this review, we evaluate the combined effects of ocean warming with other environmental stressors and emphasize the need for multiple-stressor studies to provide a deeper understanding of seagrass resilience. We conclude by discussing the most significant knowledge gaps and future directions for seagrass research. 相似文献
999.
Tuyen V. Ha Wonkook Kim Thang Nguyen-Tien Johanna Lindahl Hung Nguyen-Viet Nguyen Quang Thi Huy Van Nguyen Fred Unger Hu Suk Lee 《PLoS neglected tropical diseases》2021,15(6)
Japanese encephalitis (JE) is the major cause of viral encephalitis (VE) in most Asian-Pacific countries. In Vietnam, there is no nationwide surveillance system for JE due to lack of medical facilities and diagnoses. Culex tritaeniorhynchus, Culex vishnui, and Culex quinquefasciatus have been identified as the major JE vectors in Vietnam. The main objective of this study was to forecast a risk map of Culex mosquitoes in Hanoi, which is one of the most densely populated cities in Vietnam. A total of 10,775 female adult Culex mosquitoes were collected from 513 trapping locations. We collected temperature and precipitation information during the study period and its preceding month. In addition, the other predictor variables (e.g., normalized difference vegetation index [NDVI], land use/land cover and human population density), were collected for our analysis. The final model selected for estimating the Culex mosquito abundance included centered rainfall, quadratic term rainfall, rice cover ratio, forest cover ratio, and human population density variables. The estimated spatial distribution of Culex mosquito abundance ranged from 0 to more than 150 mosquitoes per 900m2. Our model estimated that 87% of the Hanoi area had an abundance of mosquitoes from 0 to 50, whereas approximately 1.2% of the area showed more than 100 mosquitoes, which was mostly in the rural/peri-urban districts. Our findings provide better insight into understanding the spatial distribution of Culex mosquitoes and its associated environmental risk factors. Such information can assist local clinicians and public health policymakers to identify potential areas of risk for JE virus. Risk maps can be an efficient way of raising public awareness about the virus and further preventive measures need to be considered in order to prevent outbreaks and onwards transmission of JE virus. 相似文献
1000.