首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10196篇
  免费   807篇
  国内免费   953篇
  2024年   28篇
  2023年   151篇
  2022年   331篇
  2021年   586篇
  2020年   397篇
  2019年   502篇
  2018年   451篇
  2017年   348篇
  2016年   421篇
  2015年   644篇
  2014年   726篇
  2013年   825篇
  2012年   993篇
  2011年   808篇
  2010年   510篇
  2009年   459篇
  2008年   465篇
  2007年   435篇
  2006年   386篇
  2005年   364篇
  2004年   264篇
  2003年   240篇
  2002年   220篇
  2001年   207篇
  2000年   159篇
  1999年   174篇
  1998年   84篇
  1997年   96篇
  1996年   83篇
  1995年   55篇
  1994年   59篇
  1993年   51篇
  1992年   65篇
  1991年   52篇
  1990年   46篇
  1989年   37篇
  1988年   30篇
  1987年   20篇
  1986年   20篇
  1985年   18篇
  1984年   12篇
  1983年   19篇
  1982年   11篇
  1981年   15篇
  1980年   8篇
  1973年   7篇
  1972年   13篇
  1971年   8篇
  1970年   7篇
  1968年   7篇
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
141.
Under the microenvironment, tumour progression is substantially affected by cell‐cell communication. In spite of the mediating effect of extracellular nanovesicles (EVs) on cell‐cell communication by packaging into circRNAs, the effect of EVs circRNA hsa_circ_0000190 (circ‐0000190) in osteosarcoma is still not clear. Circ‐0000190 expressions in tissues and EVs from plasma were compared between osteosarcoma patients and controls. Thereafter, receiver operating characteristic (ROC) curve was drawn and area under the curve was calculated to examine whether the diagnostic results were accurate, and the effect of EVs circ‐0000190 was dug out via the determination of cell phenotypes and animal assays. Results showed circ‐0000190 exhibited an obvious reduction in EVs and tissues of osteosarcoma patients (P < .05). It was also discovered that EVs encapsulated the majority of circ‐0000190, and EVs‐encapsulated circ‐0000190 could be applied to make a distinction between osteosarcoma patients and controls. Besides, EVs circ‐0000190 in osteosarcoma cells transported from normal cells weakened the capacities of osteosarcoma cells to migrate, proliferate and invade, so as to block their biological malignant behaviours (P < .05). In addition, under the action of EVs circ‐0000190, tumour growth was impeded and the expression of TET1 was inhibited via the competitive binding to miR‐767‐5p. In all, EVs circ‐0000190 has a good prospect as it can be regarded as a new biomarker for detecting osteosarcoma. EVs circ‐0000190 transported from normal cells to osteosarcoma cells impeded the in vitro and in vivo development of osteosarcoma, implying that EVs circ‐0000190 exerts an effect on communication between normal cells and osteosarcoma cells in the carcinogenesis process of osteosarcoma.  相似文献   
142.
LIVIN, a member of the inhibitor of apoptosis proteins (IAPs), is reported playing important roles in the development and progression of multiple human cancers. However, its underlined mechanisms in human renal cell carcinoma (RCC) are still needed to be clarified. In the present study, we reported that inhibition of miR-214 promoted the expression of LIVIN, then facilitated RCC cells growth and reduced the sensitivity of RCC cells to chemotherapeutic drugs. In constant, overexpression of miR-214 had contradictory effects. Further investigation showed that miR-214 was down-regulated in RCC because of abnormal methylation. In addition, DNA methyltransferase DNMT1, miR-214 and LIVIN are directly correlated in RCC patients. In conclusion, these results suggest that abnormal miR-214 methylation negatively regulates LIVIN, which may promote RCC cells growth and reduced the sensitivity of RCC cells to chemotherapeutic drugs.  相似文献   
143.
Fibroblast growth factor 21 (FGF21), a metabolic hormone with pleiotropic effects on glucose and lipid metabolism and insulin sensitivity, alleviates the process of acute pancreatitis (AP). However, its mechanism remains elusive. The pathological and physiological characteristics of FGF21 are observed in both patients with AP and cerulein‐induced AP models, and the mechanisms of FGF21 in response to AP are investigated by evaluating the impact of autophagy in FGF21‐treated mice and cultured pancreatic cells. Circulating levels of FGF21 significantly increase in both AP patients and cerulein‐induced AP mice, which is accompanied by the change of pathology in pancreatic injury. Replenishment of FGF21 distinctly reverses cerulein‐induced pancreatic injury and improves cerulein‐induced autophagy damage in vivo and in vitro. Mechanically, FGF21 acts on pancreatic acinar cells to up‐regulate Sirtuin‐1 (Sirt1) expression, which in turn repairs impaired autophagy and removes damaged organs. In addition, blockage of Sirt1 accelerates cerulein‐induced pancreatic injury and weakens the regulative effect in FGF21‐activated autophagy in mice. These results showed that FGF21 protects against cerulein‐induced AP by activation of Sirtuin‐1‐autophagy axis.  相似文献   
144.
The traditional Zn/MnO2 battery has attracted great interest due to its low cost, high safety, high output voltage, and environmental friendliness. However, it remains a big challenge to achieve long‐term stability, mainly owing to the poor reversibility of the cathode reaction. Different from previous studies where the cathode redox reaction of MnO2/MnOOH is in solid state with limited reversibility, here a new aqueous rechargeable Zn/MnO2 flow battery is constructed with dissolution–precipitation reactions in both cathodes (Mn2+/MnO2) and anodes (Zn2+/Zn), which allow mixing of anolyte and catholyte into only one electrolyte and remove the requirement for an ion selective membrane for cost reduction. Impressively, this new battery exhibits a high discharge voltage of ≈1.78 V, good rate capability (10C discharge), and excellent cycling stability (1000 cycles without decay) at the areal capacity ranging from 0.5 to 2 mAh cm‐2. More importantly, this battery can be readily enlarged to a bench scale flow cell of 1.2 Ah with good capacity retention of 89.7% at the 500th cycle, displaying great potential for large‐scale energy storage.  相似文献   
145.
Heteroatom doping is widely recognized as an appealing strategy to break the capacitance limitation of carbonaceous materials toward sodium storage. However, the concrete effects, especially for heteroatomic phase transformation, during the sodium storage reaction remain a confusing topic. Here, a novel hypercrosslinked polymerization approach is demonstrated to fabricate pyrrole/thiophene hypercrosslinked microporous copolymer and further give porous carbonaceous materials with accurately regulated N/S dual doping corresponding to starting feeding ratios. Significantly, the N doping contributes to the conductivity and surface wettability, while the S doping is bridged to build stable active sites, which can be electrochemically converted into mercaptan anions via faraday reaction and further enhancing reversible capacities. Meanwhile, the abundant S doping can also conduce to the expanded interlayer spacing to shorten the ions diffusion distance, thus optimizing the reaction kinetic. As a result, the N0.2S0.8‐micro‐dominant porous carbon delivers the highest reversible capacity of 521 mAh g?1 at 100 mA g?1 and excellent cyclic stability over 2000 cycles at 2000 mA g?1 with a capacity decay of 0.0145 mAh g?1 per cycle. This work is anticipated to provide an in‐depth understanding of capacitance contribution and illuminate the heteroatomic phase transformation during sodium storage reactions for doping carbonaceous anodes.  相似文献   
146.
147.
148.
Li metal, which has a high theoretical specific capacity and low redox potential, is considered to the most promising anode material for next‐generation Li ion‐based batteries. However, it also exhibits a disadvantageous solid electrolyte interphase (SEI) layer problem that needs to be resolved. Herein, an advanced separator composed of reduced graphene oxide fiber attached to aramid paper (rGOF‐A) is introduced. When rGOF‐A is applied, F? anions, generated from the decomposition of the LiPF6 electrolyte during the SEI layer formation process form semi‐ionic C? F bonds along the surface of rGOF. As Li+ ions are plated, the “F‐doped” rGO surface induces the formation of LiF, which is known as a component of a chemically stable SEI, therefore it helps the Li metal anode to operate stably at a high current of 20 mA cm?2 with a high capacity of 20 mAh cm?2. The proposed rGOF‐A separator successfully achieves a stable SEI layer that could resolve the interfacial issues of the Li metal anode.  相似文献   
149.
Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy‐based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li3Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF‐dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb‐coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g?1 after 200 cycles at 500 mA g?1, compared to only 72% and 170 mAh g?1 for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long‐term cycling stability for alloy‐based anode materials.  相似文献   
150.
Sequential deposition has great potential to achieve high performance in organic solar cells due to the resulting well‐controlled vertical phase separation. In this work, double bulk heterojunction organic solar cells are fabricated by sequential‐blade cast in ambient conditions. Probed by the in situ grazing incidence X‐ray diffraction and in situ UV–vis absorption measurements, the seq‐blade system exhibits a different tendency from each of the binary films during the film formation process. Due to the extensive aggregation of FOIC, the binary PBDB‐T:FOIC film displays a strong and large phase separation, resulting in low current density (Jsc) and unsatisfactory power conversion efficiency. In the seq‐blade cast system, the bottom layer PBDB‐T:IT‐M produces many crystal nuclei for the top layer PBDB‐T:FOIC, so the PBDB‐T molecules are able to crystallize easily and quickly. Balanced crystallization kinetics between polymer and small molecule and an ideal percolation network in the film are observed. In addition, the balanced crystallization kinetics are favorable toward realizing lower recombination loss through charge transport processes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号