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   92506篇
  免费   6724篇
  国内免费   6404篇
  105634篇
  2024年   201篇
  2023年   1254篇
  2022年   2940篇
  2021年   4868篇
  2020年   3194篇
  2019年   4016篇
  2018年   3957篇
  2017年   2866篇
  2016年   4052篇
  2015年   5842篇
  2014年   6886篇
  2013年   7248篇
  2012年   8494篇
  2011年   7737篇
  2010年   4482篇
  2009年   4186篇
  2008年   4775篇
  2007年   4146篇
  2006年   3532篇
  2005年   2822篇
  2004年   2312篇
  2003年   2105篇
  2002年   1698篇
  2001年   1471篇
  2000年   1342篇
  1999年   1407篇
  1998年   820篇
  1997年   892篇
  1996年   814篇
  1995年   776篇
  1994年   673篇
  1993年   570篇
  1992年   682篇
  1991年   535篇
  1990年   455篇
  1989年   331篇
  1988年   278篇
  1987年   220篇
  1986年   185篇
  1985年   211篇
  1984年   124篇
  1983年   118篇
  1982年   55篇
  1981年   23篇
  1980年   20篇
  1979年   18篇
  1976年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Although cisplatin is one of the chemotherapeutics most frequently used in oral squamous cell carcinoma (OSCC) treatment,it exerts multiple side effects and poo...  相似文献   
102.
There are multiple reports of autoimmune response in patients with lung cancer. To investigate whether a novel autoantibody is present in patients with lung cancer and evaluate its clinical diagnostic and prognostic value, sera from 10 patients with lung cancer and 10 normal individuals were analyzed using immunofluorescence and Western blotting. It was found that one serum sample from the patients with squamous carcinoma gave a fine speckled pattern staining in nucleus and had a high titer antinuclear autoantibody which could recognize 31 kD of nuclear protein isolated from both cancer cells and normal cells. The same patient’s serum was further used to immunoprecipitate the target antigen. The protein bands were excised from the SDS-PAGE gels and were analyzed with a Qstar Pulser I Quadrupole time-flight mass spectrometer, and the 31 kD target antigen was identified as U1-AsnRNP. To test the prevalence of anti-U1-AsnRNP antibody, sera from 93 patients including 36 squmaous carcinomas (SCC), 26 adenocarcinomas (Ad), and 31 small cell carcinomas (SCLC) were screened by Western blotting. The results demonstrated that anti-U1-A snRNP antibody was present in 50% of SCC sera, 26.9% of Ad sera and 54.8% of SCLC sera. In this paper, we report for the first time that anti-U1-AsnRNP antibody could be detected in the patients with lung cancer.  相似文献   
103.
The mortality of patients with malignant gliomas remains high despite the advancement in multi-modal therapy including surgery, radio- and chemotherapy. Glioma stem cells (GSCs), sharing some characteristics with normal neural stem cells (NSCs), contribute to the cellular origin for primary gliomas and the recurrence of malignant gliomas after current conventional therapy. Accordingly, targeting GSCs proves to be a promising avenue of therapeutic intervention. The specific tropism of NSCs to GSCs provides a novel platform for targeted delivery of therapeutic agents. Tropism and mobilization of NSCs are enhanced by hypoxia through upregulating chemotactic cytokines and activating several signaling pathways. Moreover, hypoxia-inducible factors (HIFs) produced under hypoxic microenvironment of the stem cell niche play critical roles in the growth and stemness phenotypes regulation of both NSCs and GSCs. However, the definite cellular and molecular mechanisms of HIFs involvement in the process remain obscure. In this review, we focus on the pivotal roles of HIFs in migration of NSCs to GSCs and potential roles of HIFs in dictating the fates of migrated NSCs and targeted GSCs.  相似文献   
104.
It has been verified that prochymosin is characterized by a two-stage refolding: dilution of unfolded protein into pH 11 buffer followed by neutralization at pH 8; the high-pH step is indispensable. Here we demonstrate that one-stage refolding around pH 8 can be achieved when GroE or 10-fold molar excess (rather than catalytic concentration) of protein disulfide isomerase (PDI) over prochymosin is present. The helping effect varies with the oxidation states of prochymosin. GroE and PDI increase the reactivation of the unfolded, partially reduced and the unfolded, oxidized prochymosin from 5% to 40% and from 50% to 100%, respectively. For the unfolded and fully reduced prochymosin, GroE does not have a positive effect, whereas PDI promotes renaturation from 2% to 28%. Based on our previous and present observations, we propose that at pH 8 there may be two kinds of incorrect interactions within and between prochymosin polypeptides leading to unproductive pathways: one prevents disulfide rearrangement, which can be avoided by high pH; the other interferes with acquisition of native conformation, which can be relieved by GroE and PDI.  相似文献   
105.
In this contribution, a simple, rapid, colorimeteric and selective assay for lysine was achieved by a controllable end-to-end assembly of gold nanorods (AuNRs) in the presence of Eu(3+) and lysine. This one-pot end-to-end assembly of 11-mercaptoundecanoic acid (MUA) modified AuNRs was occurred in Britton-Robinson buffer of pH 6.0, which involves the coordination binding between Eu(3+) and COO(-) groups as well as the electrostatic interaction of the COO(-) groups of MUA with the -NH(3)(+) group of lysine. As monitored by absorption spectra, scanning electron microscopic (SEM) images and dynamic light scattering (DLS) measurement, the end-to-end chain assembly results in large red-shift in the longitudinal plasmon resonance absorption (LPRA), giving red-to-blue color change of AuNRs. Importantly, it was found that the red-shift of LPRA is linearly proportional to the concentrations of lysine in the range of 5.0×10(-6)-1.0×10(-3)M with the limit of detection (LOD) being 1.6×10(-6)M (3σ/k). This red-shift of LPRA is highly selective, making it possible to develop a rapid, selective and visual assay for lysine in food samples.  相似文献   
106.
Aseptic loosening is the most common long-term complication of total joint replacement, which is associated with the generation of wear debris. The purpose of this study was to investigate the inhibitory effect of small interfering RNA (siRNA) targeting tumor necrosis factor-α (TNF-α) on wear debris-induced inflammation. A local delivery of lentivirus-mediated TNF-α siRNA into the modified murine air pouch, which was stimulated by polymethylmethacrylate (PMMA) particles, resulted in significant blockage of TNF-α both in mRNA and protein levels for up to 4 weeks. In addition, significant down-regulation of interleukin-1 (IL-1) and interleukin-6 (IL-6) was observed in TNF-α siRNA-treated pouches. The safety profile of gene therapy was proven by Bioluminescent assay and quantitative fluorescent flux. Histological analysis revealed less inflammatory responses (thinner pouch membrane and decreased cellular infiltration) in TNF-α siRNA-treated pouches. These findings suggest that local delivery of TNF-α siRNA might be an excellent therapeutic candidate to inhibit particle-induced inflammation.  相似文献   
107.
Although superhydrophobic materials have attracted much research interest in anti-icing,some controversy still exists.In this research,we report a cost-effective method used to verify the contribution of area fraction to ice adhesion strength.We tried to partially-embed siliea nanopnarticles into microscale fabrics of a commercial polyamide mesh.Then,the area fraction could be determined by altering the mesh size.Generally,the ice adhesion strength decreases as the area fraction decreases.An ice adhesion strength of~1.9 kPa and a delayed freezing time of~1048 s can be obtained.We attribute the low ice adhesion strength to the combination of superhydro-phobicity and stress concentration.The superhydrophobicity prohibits the water from penetrating into the voids of the meshes,and the small actual contact area leads to stress concentration which promotes interfacial crack propagation.Moreover,our superhydrophobic mesh simultaneously exhibis a micro-nano hierarchical structure and a partally-cmbedded structure.Therefore,the as-prepared superhydrophobic mesh retained the ieephobicity after 20 icingldeicing cycles,and maintained its superhydrophobicity even afier 60 sandpaper-abrasion cycles and a 220"C thermal treatment.  相似文献   
108.
109.
SUMOylation of proteins is an important regulatory element in modulating protein function and has been implicated in the pathogenesis of numerous human diseases such as cancers, neurodegenerative diseases, brain injuries, diabetes, and familial dilated cardiomyopathy. Growing evidence has pointed to a significant role of SUMO in kidney diseases such as DN, RCC, nephritis, AKI, hypertonic stress and nephrolithiasis. Recently, emerging studies in podocytes demonstrated that SUMO might have a protective role against podocyte apoptosis. However, the SUMO code responsible for beneficial outcome in the kidney remains to be decrypted. Our recent experiments have revealed that the expression of both SUMO and SUMOylated proteins is appreciably elevated in hypoxia‐induced tubular epithelial cells (TECs) as well as in the unilateral ureteric obstruction (UUO) mouse model, suggesting a role of SUMO in TECs injury and renal fibrosis. In this review, we attempt to decipher the SUMO code in the development of kidney diseases by summarizing the defined function of SUMO and looking forward to the potential role of SUMO in kidney diseases, especially in the pathology of renal fibrosis and CKD, with the goal of developing strategies that maximize correct interpretation in clinical therapy and prognosis.  相似文献   
110.
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