全文获取类型
收费全文 | 3318篇 |
免费 | 323篇 |
国内免费 | 358篇 |
出版年
2024年 | 9篇 |
2023年 | 41篇 |
2022年 | 86篇 |
2021年 | 205篇 |
2020年 | 131篇 |
2019年 | 157篇 |
2018年 | 151篇 |
2017年 | 105篇 |
2016年 | 140篇 |
2015年 | 185篇 |
2014年 | 253篇 |
2013年 | 242篇 |
2012年 | 304篇 |
2011年 | 279篇 |
2010年 | 187篇 |
2009年 | 164篇 |
2008年 | 169篇 |
2007年 | 149篇 |
2006年 | 136篇 |
2005年 | 128篇 |
2004年 | 127篇 |
2003年 | 108篇 |
2002年 | 98篇 |
2001年 | 91篇 |
2000年 | 70篇 |
1999年 | 72篇 |
1998年 | 40篇 |
1997年 | 25篇 |
1996年 | 24篇 |
1995年 | 27篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
1955年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有3999条查询结果,搜索用时 31 毫秒
121.
Background
Right internal jugular vein (IJV) is a preferred access route for tunneled (cuffed) dialysis catheters (TDCs), and both right external jugular vein (EJV) and left IJV are alternative routes for patients in case the right IJV isn’t available for TDC placement. This retrospective study aimed to determine if a disparity exists between the two alternative routes in hemodialysis patients in terms of outcomes of TDCs.Methods
49 hemodialysis patients who required TDCs through right EJV (n = 21) or left IJV (n = 28) as long-term vascular access were included in this study. The primary end point was cumulative catheter patency. Secondary end points include primary catheter patency, proportion of patients that never required urokinase and incidence of catheter-related bloodstream infections (CRBSI).Results
A total of 20,870 catheter-days were evaluated and the median was 384 (interquartile range, 262–605) catheter-days. Fewer catheters were removed in the right EJV group than in the left IJV group (P = 0.007). Mean cumulative catheter patency was higher in the right EJV group compared with the left IJV group (P = 0.031). There was no significant difference between the two groups in the incidence of CRBSI, primary catheter patency or proportion of patients that never required urokinase use. Total indwell time of antecedent catheters was identified as an independent risk factor for cumulative catheter patency by Cox regression hazards test with an HR of 2.212 (95% CI, 1.363–3.588; p = 0.001).Conclusions
Right EJV might be superior to left IJV as an alternative insertion route for TDC placement in hemodialysis patients whose right IJVs are unavailable. 相似文献122.
Integrated Intercalation‐Based and Interfacial Sodium Storage in Graphene‐Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel
下载免费PDF全文
![点击此处可从《Liver Transplantation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chaoji Chen Henghui Xu Tengfei Zhou Zaiping Guo Lineng Chen Mengyu Yan Liqiang Mai Pei Hu Shijie Cheng Yunhui Huang Jia Xie 《Liver Transplantation》2016,6(13)
Sodium storage in both solid–liquid and solid–solid interfaces is expected to extend the horizon of sodium‐ion batteries, leading to a new strategy for developing high‐performance energy‐storage materials. Here, a novel composite aerogel with porous Li4Ti5O12 (PLTO) nanofibers confined in a highly conductive 3D‐interconnected graphene framework (G‐PLTO) is designed and fabricated for Na storage. A high capacity of 195 mA h g?1 at 0.2 C and super‐long cycle life up to 12 000 cycles are attained. Electrochemical analysis shows that the intercalation‐based and interfacial Na storage behaviors take effect simultaneously in the G‐PLTO composite aerogel. An integrated Na storage mechanism is proposed. This study ascribes the excellent performance to the unique structure, which not only offers short pathways for Na+ diffusion and conductive networks for electron transport, but also guarantees plenty of PLTO–electrolyte and PLTO–graphene interfacial sites for Na+ adsorption. 相似文献
123.
Skin aging caused by intrinsic or extrinsic processes characterized with functional proteomics
下载免费PDF全文
![点击此处可从《Proteomics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jia‐You Fang Pei‐Wen Wang Chun‐Hsun Huang Mu‐Hong Chen Yun‐Ru Wu Tai‐Long Pan 《Proteomics》2016,16(20):2718-2731
The skin provides protection against environmental stress. However, intrinsic and extrinsic aging causes significant alteration to skin structure and components, which subsequently impairs molecular characteristics and biochemical processes. Here, we have conducted an immunohistological investigation and established the proteome profiles on nude mice skin to verify the specific responses during aging caused by different factors. Our results showed that UVB‐elicited aging results in upregulation of proliferating cell nuclear antigen and strong oxidative damage in DNA, whereas chronological aging abolished epidermal cell growth and increased the expression of caspase‐14, as well as protein carbonylation. Network analysis indicated that the programmed skin aging activated the ubiquitin system and triggered obvious downregulation of 14‐3‐3 sigma, which might accelerate the loss of cell growth capacity. On the other hand, UVB stimulation enhanced inflammation and the risk of skin carcinogenesis. Collectively, functional proteomics could provide large‐scale investigation of the potent proteins and molecules that play important roles in skin subjected to both intrinsic and extrinsic aging. 相似文献
124.
Wu Man Liyuan Zhang Xihua Li Xiaobing Xie Wenfeng Pei Jiwen Yu Shuxun Yu Jinfa Zhang 《Molecular genetics and genomics : MGG》2016,291(4):1749-1767
125.
C Luo X Yao J Li B He Q Liu H Ren F Liang M Li H Lin J Peng T F Yuan Z Pei H Su 《Cell death & disease》2016,7(3):e2160
Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality. The mechanisms underlying its pathological complications have not been fully identified. Here, we investigate the potential involvement of the glymphatic system in the neuropathology of SAH. We demonstrate that blood components rapidly enter the paravascular space following SAH and penetrate into the perivascular parenchyma throughout the brain, causing disastrous events such as cerebral vasospasm, delayed cerebral ischemia, microcirculation dysfunction and widespread perivascular neuroinflammation. Clearance of the paravascular pathway with tissue-type plasminogen activator ameliorates the behavioral deficits and alleviates histological injury of SAH. Interestingly, AQP4−/− mice showed no improvements in neurological deficits and neuroinflammation at day 7 after SAH compared with WT control mice. In conclusion, our study proves that the paravascular pathway dynamically mediates the pathological complications following acute SAH independently of glymphatic control.Cerebral aneurysm rupture causes subarachnoid hemorrhage (SAH), which is associated with a high mortality due to its secondary complications, including hemorrhage, hydrocephalus and delayed cerebral ischemia (DCI).1, 2, 3 Therapeutic interventions against the secondary complications, especially DCI, are yet limited, as the pathological mechanism underlying that is not fully understood.2, 3, 4, 5, 6, 7 Current hypotheses of the development of the secondary complications mainly include cerebral vasospasm (CVS) and the microcirculation disturbance, as well as parenchymal arterial lesions, microthrombosis and neuroinflammation.1, 2, 4, 7, 8, 9Previous studies have shown that the blockade of cerebral lymphatic drainage deteriorated the secondary cerebral ischemia after SAH, suggesting that the cerebral lymphatic drainage pathway could be involved in the pathological mechanism of SAH.10, 11 However, the central nervous system (CNS) was considered lack of a conventional lymphatic drainage system in the past. Recently, several studies have shown that the brain has in fact the proper lymphatic system, including sinus-associated lymphatic vessels and the glymphatic system (GS).12, 13, 14, 15 Sinus-associated lymphatic vessels express all of the molecular hallmarks of lymphatic endothelial cells, contain cerebrospinal fluid (CSF) and immune cells, and drain into the deep cervical lymph nodes.12, 13There is a histologically defined space in the brain, the Virchow–Robin space, where the subarachnoid space meets the paravascular space (or perivascular space in somewhere, PVS).16 The GS is a specialized brain-wide anatomic structure locating at the PVS surrounding the brain vasculature, which is ensheathed with the astroglial endfeet and astroglial water channel aquaporin-4 (AQP4).14, 15 The GS facilitates the efficient lymphatic clearance of extracellular solutes and fluid in the brain through astroglial-mediated interstitial fluid bulk flow.14Impairment of GS involves neurological conditions including traumatic brain injuries,17 ischemic stroke18 and aged brain.19 Interestingly, brain imaging study with magnetic resonance imaging reported weakened GS perfusion following acute stroke or SAH.18, 20 However, little is known about whether the GS is involved in the secondary complications of SAH. Here, we examined the potential involvement of GS in SAH-associated pathology progression with in vivo two-photon microscopy and CLARITY technique.21, 22 Our data showed that subarachnoid blood flowed into the brain parenchyma rapidly through the PVS, causing CVS, vasculitis, widespread microinfraction and neuroinflammation in the animal model of SAH and SAH patients. Prevention of CVS with Fasudil23 did not improve the neurological impairment nor alleviated the pathology, while the PVS clearance with tissue-type plasminogen activator (tPA) infusion improved the behavioral recovery and reduced neuroinflammation in the brain. Interestingly, AQP4−/− mice showed no improvements in neurological deficits and neuroinflammation at day 7 after SAH compared with WT control mice. Our study therefore suggested that the paravacular pathway dynamically mediates the pathological complications following acute SAH independently of glymphatic control. 相似文献
126.
127.
128.
BackgroundSingle nucleotide polymorphisms (SNPs) in the estrogen receptor gene (ESR1) play critical roles in breast cancer (BC) susceptibility. Genome-wide association studies have reported that SNPs in ESR1 are associated with BC susceptibility; however, the results of recent studies have been inconsistent. Therefore, we performed this meta-analysis to obtain more accurate and credible results.MethodsWe pooled published literature from PubMed, EMBASE, and Web of Science and calculated odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of associations using fixed effects models and random effects models. Twenty relevant case-control and cohort studies of the 3 related SNPs were identified.ResultsThree SNPs of the ESR1 gene, rs2077647:T>C, rs2228480:G>A and rs3798577:T>C, were not associated with increased BC risk in our overall meta-analysis. Stratified analysis by ethnicity showed that in Caucasians, the rs2228480 AA genotype was associated with a 26% decreased risk of BC compared with the GG genotype (OR = 0.740, 95% CI: 0.555–0.987). The C allele of the rs3798577:T>C variant was associated with decreased BC risk in Asians (OR = 0.828, 95% CI: 0.730–0.939), while Caucasians with this allele were found to experience significantly increased BC risk (OR = 1.551, 95% CI: 1.037–2.321). A non-significant association between rs2077647 and BC risk was identified in all of the evaluated ethnic populations.ConclusionRs3798577 was associated with an increased risk of BC in Caucasian populations but a decreased risk in Asians. Rs2228480 had a large protective effect in Caucasians, while rs2077647 was not associated with BC risk. 相似文献
129.
Hui Wang Feng Qin Liu Ruan Rui Wang Qi Liu Zhanhong Ma Xiaolong Li Pei Cheng Haiguang Wang 《PloS one》2016,11(4)
It is important to implement detection and assessment of plant diseases based on remotely sensed data for disease monitoring and control. Hyperspectral data of healthy leaves, leaves in incubation period and leaves in diseased period of wheat stripe rust and wheat leaf rust were collected under in-field conditions using a black-paper-based measuring method developed in this study. After data preprocessing, the models to identify the diseases were built using distinguished partial least squares (DPLS) and support vector machine (SVM), and the disease severity inversion models of stripe rust and the disease severity inversion models of leaf rust were built using quantitative partial least squares (QPLS) and support vector regression (SVR). All the models were validated by using leave-one-out cross validation and external validation. The diseases could be discriminated using both distinguished partial least squares and support vector machine with the accuracies of more than 99%. For each wheat rust, disease severity levels were accurately retrieved using both the optimal QPLS models and the optimal SVR models with the coefficients of determination (R2) of more than 0.90 and the root mean square errors (RMSE) of less than 0.15. The results demonstrated that identification and severity evaluation of stripe rust and leaf rust at the leaf level could be implemented based on the hyperspectral data acquired using the developed method. A scientific basis was provided for implementing disease monitoring by using aerial and space remote sensing technologies. 相似文献
130.
Xiangqian Zhang Xu Zheng Shanwen Ke Haitao Zhu Fang Liu Zemin Zhang Xinxiang Peng Lin Guo Ruizhen Zeng Pei Hou Ziqiang Liu Suowei Wu Meifang Song Jianping Yang Guiquan Zhang 《Plant molecular biology》2016,92(6):701-715
Most environmental perturbations have a direct or indirect deleterious impact on photosynthesis, and, in consequence, the overall energy status of the cell. Despite our increased understanding of convergent energy and stress signals, the connections between photosynthesis, energy and stress signals through putative common nodes are still unclear. Here we identified an endoplasmic reticulum (ER)-localized adenine nucleotide transporter1 (ER-ANT1), whose deficiency causes seedling lethality in air but viable under high CO2, exhibiting the typical photorespiratory phenotype. Metabolic analysis suggested that depletion of ER-ANT1 resulted in circadian rhythm disorders in sucrose synthesis and induced sucrose signaling pathways, indicating that the ER is involved in the regulation of vital energy metabolism in plants. In addition, the defect of ER-ANT1 triggers ER stress and activates the unfolded protein response in plant cells, suggesting ER stress and photorespiration are closely linked. These findings provide an important evidence for a key role of ER-localized ER-ANT1 in convergent energy and stress signals in rice. Our findings support the idea that ATP is a central signal involved in the plant response to a variety of stresses. 相似文献