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   3333篇
  免费   267篇
  国内免费   301篇
  2024年   7篇
  2023年   28篇
  2022年   106篇
  2021年   157篇
  2020年   125篇
  2019年   142篇
  2018年   138篇
  2017年   85篇
  2016年   143篇
  2015年   233篇
  2014年   268篇
  2013年   293篇
  2012年   294篇
  2011年   281篇
  2010年   167篇
  2009年   154篇
  2008年   189篇
  2007年   179篇
  2006年   170篇
  2005年   133篇
  2004年   95篇
  2003年   81篇
  2002年   86篇
  2001年   29篇
  2000年   42篇
  1999年   33篇
  1998年   27篇
  1997年   39篇
  1996年   34篇
  1995年   35篇
  1994年   15篇
  1993年   22篇
  1992年   10篇
  1991年   11篇
  1990年   13篇
  1989年   5篇
  1988年   4篇
  1987年   4篇
  1986年   6篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
排序方式: 共有3901条查询结果,搜索用时 15 毫秒
31.
32.
The heterogeneity in prognoses and chemotherapeutic responses of colon cancer patients with similar clinical features emphasized the necessity for new biomarkers that help to improve the survival prediction and tailor therapies more rationally and precisely. In the present study, we established a s troma-related l ncRNA s ignature (SLS) based on 52 lncRNAs to comprehensively predict clinical outcome. The SLS model could not only distinguish patients with different recurrence and mortality risks through univariate analysis, but also served as an independent factor for relapse-free and overall survival. Compared with the conventionally used TNM stage system, the SLS model clearly possessed higher predictive accuracy. Moreover, the SLS model also effectively screened chemotherapy-responsive patients, as only patients in the low-SLS group could benefit from adjuvant chemotherapy. The following cell infiltration and competing endogenous RNA (ceRNA) network functional analyses further confirmed the association between the SLS model and stromal activation-related biological processes. Additionally, this study also identified three phenotypically distinct colon cancer subtypes that varied in clinical outcome and chemotherapy benefits. In conclusion, our SLS model may be a significant determinant of survival and chemotherapeutic decision-making in colon cancer and may have a strong clinical transformation value.  相似文献   
33.
34.
Water splitting requires development of cost‐effective multifunctional materials that can catalyze both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) efficiently. Currently, the OER relies on the noble‐metal catalysts; since with other catalysts, its operation environment is greatly limited in alkaline conditions. Herein, an advanced water oxidation catalyst based on metallic Co9S8 decorated with single‐atomic Mo (0.99 wt%) is synthesized (Mo‐Co9S8@C). It exhibits pronounced water oxidization activity in acid, alkali, and neutral media by showing positive onset potentials of 200, 90, and 290 mV, respectively, which manifests the best Co9S8‐based single‐atom Mo catalyst till now. Moreover, it also demonstrates excellent HER performance over a wide pH range. Consequently, the catalyst even outperforms noble metal Pt/IrO2‐based catalysts for overall water splitting (only requiring 1.68 V in acid, and 1.56 V in alkaline). Impressively, it works under a current density of 10 mA cm?2 with no obvious decay during a 24 h (0.5 m H2SO4) and 72 h (1.0 m KOH) durability experiment. Density functional theory (DFT) simulations reveal that the synergistic effects of atomically dispersed Mo with Co‐containing substrates can efficiently alter the binding energies of adsorbed intermediate species and decrease the overpotentials of the water splitting.  相似文献   
35.
The introduction of 3D wettable current collectors is one of the practical strategies toward realizing high reversibility of lithium (Li) metal anodes, yet its effect is usually insufficient owing to single electron‐conductive skeleton. Here, homogeneous Li deposition behavior and enhanced Coulombic efficiency is reported for electrochemically lithiated Cu3P nanowires, owing to the formation of a mixed ion/electron‐conducting skeleton (MIECS). In particular, by evaluating the Gibbs free energy change, the possible chemical reaction between Cu3P and molten Li is used to construct a MIECS containing Li3P and Cu–Li alloy phase. The successful conversion of Cu3P nanowires to Li3P and Cu–Li alloy nanocomposite not only greatly reduces the surface energy between molten Li and Cu3P, but also induces uniform Li stripping/plating behavior via balanced ion/electron transport. Thus, the as‐obtained Li@MIECS composite anode displays superior cycling stability in both symmetric cells and full cells. This work provides a promising option for the preparation of high‐performance composite Li anodes containing MIECS by thermally pre‐storing Li.  相似文献   
36.
The relatively low capacity and capacity fade of spinel LiMn2O4 (LMO) limit its application as a cathode material for lithium‐ion batteries. Extending the potential window of LMO below 3 V to access double capacity would be fantastic but hard to be realized, as it will lead to fast capacity loss due to the serious Jahn–Teller distortion. Here using experiments combined with extensive ab initio calculations, it is proved that there is a cooperative effect among individual Jahn–Teller distortions of Mn3+O6 octahedrons in LMO, named as cooperative Jahn–Teller distortion (CJTD) in the text, which is the difficulty to access the capacity beyond one lithium intercalation. It is further proposed that the cationic disordering (excess Li at Mn sites and Li/Mn exchange) can intrinsically suppress the CJTD of Mn3+O6 octahedrons. The cationic disordering can break the symmetry of Mn3+ arrangements to disrupt the correlation of distortions arising from individual JT centers and prevent the Mn3+? O bonds distorting along one direction. Interestingly, with the suppressed CJTD, the original octahedral vacancies in spinel LMO are activated and can serve as extra Li‐ion storage sites to access the double capacity with good reversible cycling stability in microsized LMO.  相似文献   
37.
38.
Li  Fan  Li  Qian  Zuo  Xiaolei  Fan  Chunhai 《中国科学:生命科学英文版》2020,63(8):1130-1141
Self-assembled DNA nanostructures have shown remarkable potential in the engineering of biosensing interfaces, which can improve the performance of various biosensors. In particular, by exploiting the structural rigidity and programmability of the framework nucleic acids with high precision, molecular recognition on the electrochemical biosensing interface has been significantly enhanced, leading to the development of highly sensitive and specific biosensors for nucleic acids, small molecules,proteins, and cells. In this review, we summarize recent advances in DNA framework-engineered biosensing interfaces and the application of corresponding electrochemical biosensors.  相似文献   
39.
40.
Intraneuronal accumulation of wild‐type tau plays a key role in Alzheimer's disease, while the mechanisms underlying tauopathy and memory impairment remain unclear. Here, we report that overexpressing full‐length wild‐type human tau (hTau) in mouse hippocampus induces learning and memory deficits with remarkably reduced levels of multiple synapse‐ and memory‐associated proteins. Overexpressing hTau inhibits the activity of protein kinase A (PKA) and decreases the phosphorylation level of cAMP‐response element binding protein (CREB), GluA1, and TrkB with reduced BDNF mRNA and protein levels both in vitro and in vivo. Simultaneously, overexpressing hTau increased PKAR2α (an inhibitory subunit of PKA) in nuclear fraction and inactivated proteasome activity. With an increased association of PKAR2α with PA28γ (a nuclear proteasome activator), the formation of PA28γ‐20S proteasome complex remarkably decreased in the nuclear fraction, followed by a reduced interaction of PKAR2α with 20S proteasome. Both downregulating PKAR2α by shRNA and upregulating proteasome by expressing PA28γ rescued hTau‐induced PKA inhibition and CREB dephosphorylation, and upregulating PKA improved hTau‐induced cognitive deficits in mice. Together, these data reveal that intracellular tau accumulation induces synapse and memory impairments by inhibiting PKA/CREB/BDNF/TrkB and PKA/GluA1 signaling, and deficit of PA28γ‐20S proteasome complex formation contributes to PKAR2α elevation and PKA inhibition.  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