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   27558篇
  免费   2560篇
  国内免费   2855篇
  32973篇
  2024年   80篇
  2023年   370篇
  2022年   787篇
  2021年   1224篇
  2020年   996篇
  2019年   1187篇
  2018年   1136篇
  2017年   856篇
  2016年   1137篇
  2015年   1724篇
  2014年   2021篇
  2013年   2147篇
  2012年   2555篇
  2011年   2339篇
  2010年   1571篇
  2009年   1384篇
  2008年   1495篇
  2007年   1359篇
  2006年   1253篇
  2005年   1070篇
  2004年   933篇
  2003年   945篇
  2002年   815篇
  2001年   484篇
  2000年   432篇
  1999年   365篇
  1998年   296篇
  1997年   200篇
  1996年   198篇
  1995年   202篇
  1994年   170篇
  1993年   118篇
  1992年   147篇
  1991年   117篇
  1990年   114篇
  1989年   96篇
  1988年   84篇
  1987年   67篇
  1986年   70篇
  1985年   64篇
  1984年   45篇
  1983年   34篇
  1982年   35篇
  1981年   24篇
  1980年   17篇
  1979年   21篇
  1977年   18篇
  1974年   17篇
  1972年   18篇
  1971年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Microvesicles (MVs, also known as exosomes, ectosomes, microparticles) are released by various cancer cells, including lung, colorectal, and prostate carcinoma cells. MVs released from tumor cells and other sources accumulate in the circulation and in pleural effusion. Although recent studies have shown that MVs play multiple roles in tumor progression, the potential pathological roles of MV in pleural effusion, and their protein composition, are still unknown. In this study, we report the first global proteomic analysis of highly purified MVs derived from human nonsmall cell lung cancer (NSCLC) pleural effusion. Using nano‐LC–MS/MS following 1D SDS‐PAGE separation, we identified a total of 912 MV proteins with high confidence. Three independent experiments on three patients showed that MV proteins from PE were distinct from MV obtained from other malignancies. Bioinformatics analyses of the MS data identified pathologically relevant proteins and potential diagnostic makers for NSCLC, including lung‐enriched surface antigens and proteins related to epidermal growth factor receptor signaling. These findings provide new insight into the diverse functions of MVs in cancer progression and will aid in the development of novel diagnostic tools for NSCLC.  相似文献   
992.
In the present study, we screened proteomic and cytokine biomarkers between patients with adenomatous polyps and colorectal cancer (CRC) in order to improve our understanding of the molecular mechanisms behind turmorigenesis and tumor progression in CRC. To this end, we performed comparative proteomic analysis of plasma proteins using a combination of 2DE and MS as well as profiled differentially regulated cytokines and chemokines by multiplex bead analysis. Proteomic analysis identified 11 upregulated and 13 downregulated plasma proteins showing significantly different regulation patterns with diagnostic potential for predicting progression from adenoma to carcinoma. Some of these proteins have not previously been implicated in CRC, including upregulated leucine‐rich α‐2‐glycoprotein, hemoglobin subunit β, Ig α‐2 chain C region, and complement factor B as well as downregulated afamin, zinc‐α‐2‐glycoprotein, vitronectin, and α‐1‐antichymotrypsin. In addition, plasma levels of three cytokines/chemokines, including interleukin‐8, interferon gamma‐induced protein 10, and tumor necrosis factor α, were remarkably elevated in patients with CRC compared to those with adenomatous polyps. Although further clinical validation is required, these proteins and cytokines can be established as novel biomarkers for CRC and/or its progression from colon adenoma.  相似文献   
993.
张东  吴宝强  陈昌泽  朱峰  孙东林 《生物磁学》2013,(30):5956-5958,5994
目的:探讨胆管结石合并胆管癌的临床特征及诊治方法。方法:回顾性分析2000年1月-2009年12月我院收治的胆管结石合并胆管癌16例患者的临床病理资料。结果:胆管癌的发生率占同期胆管结石患者的3.1%,其临床表现以右上腹疼痛及反复的胆管炎发作为主,但缺乏特异性。术前胆管癌组患者AKP、γ-GT均有不同程度升高,ALT升高12例,总胆红素升高9例,与非胆管癌组相比,AKP、γ-GT、ALT、TBIL均显著升高(P〈0.01),且胆管癌组术前血清CA19-9及CEA显著高于非胆管癌组(P〈0.01),而两组间CA125及AFP水平比较无显著差异(P〉0.05)。16例患者中可进行手术治疗10例;其中根治性手术8例,姑息性手术2例。8例根治性手术患者的1、3年生存率分别为78.6%和36.4%;2例姑息性手术患者1、3年生存率分别为50.0%和0%,两组比较具有显著性差异(P〈0.05)。结论:胆管结石合并胆管癌的临床表现缺乏特异性,患者的疗效较差,对血清CA19-9和CEA显著升高者应行病理活检确诊,治疗手段应该力争实行根治性切除,有助于提高患者的生存期。  相似文献   
994.
方玲  刘歧莎  李倩  闫淑珍  李玉  陈双林 《菌物学报》2013,32(6):1004-1011
真黏菌是一类独特的菌物。目前对其进行的系统发育研究主要是基于形态特征,分子水平的系统发育研究上小亚基核糖体RNA基因和蛋白质合成延长因子基因研究相对较多。为了扩充能有效地进行真黏菌系统发育研究的基因资源,探讨了肌动蛋白基因和β-微管蛋白基因用于真黏菌系统发育的可行性。共获得14个基因序列,肌动蛋白基因和β-微管蛋白基因各7个。在GenBank中除多头绒泡菌Physarum polycephalum外并无其他真黏菌的肌动蛋白基因和β-微管蛋白基因序列,研究获得的14个基因序列为真黏菌基因的新序列。系统发育分析表明,肌动蛋白基因能够有效地将无丝菌目、团毛菌目、绒泡菌目和发网菌目区分为4个分支,其中发网菌目为一个独立的进化支,支持了根据子实体发育所认识的真黏菌纲内部具有两条进化路线的观点,因此显示出肌动蛋白基因对于真黏菌系统发育研究的重要价值。  相似文献   
995.
Herein, a flexible surface-enhanced Raman spectroscopy (SERS) substrate composed of nanodot-arrayed Ag film and Ag nanocubes was fabricated through a simple method. The large-area nanodot-arrayed Ag film was produced at low cost and high reproducibility. The experimental results show that the coupled structure produces a much stronger SERS signal than the Ag nanocube alone and the isolated nanodot-arrayed Ag film. Furthermore, the coupling effect is sensitive to geometrical parameter of the period of the dot-array. Numerical simulations are performed to verify the electric field enhancement of the composite SERS substrate and support the experimental results.  相似文献   
996.
Gold–silver core–shell triangular nanoprisms (Au/AgTNPs) were grown onto transparent indium tin oxide (ITO) thin film-coated glass substrate through a seed-mediated growth method without using peculiar binder molecules. The resulting Au/AgTNPs were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, UV–vis spectroscopy, and cyclic voltammograms. The peak of dipolar plasmonic resonance was located at near infrared region of ~700 nm, which showed the refractive index (RI) sensitivity of 248 nm/RIU. Moreover, thin gold shells were electrodeposited onto the surface of Au/AgTNPs in order to stabilize nanoparticles. Compared with the Au/AgTNPs, this peak of localized surface plasmon resonance (LSPR) was a little red-shift and decreased slightly in intensity. The refractive index sensitivity was estimated to be 287 nm/RIU, which showed high sensitivity as a LSPR sensing platform. Those triangular nanoprisms deposited on the ITO substrate could be further functionalized to fabricate LSPR biosensors. Results of this research show a possibility of improving LSPR sensor by using core–shell nanostructures.  相似文献   
997.
Decreased levels of serum insulin-like growth factor-1 (IGF-1) have been proven to cause osteoporosis. Gene transfer of IGF-1 offers an attractive technology to treat skeletal metabolic disorders including osteoporosis, but the viral vectors are limited by their high antigenicity and immune response. Our purpose was to investigate the expression of a non-invasive vector, recombinant plasmid enhanced green fluorescent protein-N1 (pEGFP-N1) that transferred IGF-1 gene into ovariectomized (OVX) rats in vivo and evaluate the effect of this therapy on osteoporosis. OVX or sham operations were performed in 60 female, 7-month-old unmated SD rats. 12 weeks after OVX operation, the vectors were transfected to the 10-month-old rats and experimental data were detected from 48 h to 7 week after transfection. Our results showed that remarkable expression of fluorescence and serum IGF-1 was observed in the rats transfected by recombinant plasmids, indicating that IGF-1 gene was successfully transferred to OVX rats by injecting the vector through hydrodynamic method via the tail vein. The bone metabolism index including serum alkaline phosphatase, the histomorphometric parameters of lumbar vertebra including trabecular area percentage, trabecular thickness, trabecular number and trabecular separation, and the bone mineral density (BMD) and biomechanical parameters of lumbar vertebra including BMD, maximum condensing force, crushing strength in OVX rats transfected by pEGFP-N1-IGF-1 were improved remarkably compared with OVX+pEGFP-N1 rats, indicating that the transfection of recombinant plasmid pEGFP-N1-IGF-1 played a significant role in alleviating osteoporosis in rats induced by OVX. This encouraged a potential approach of IGF-1 gene therapy to the treatment of osteoporosis.  相似文献   
998.
Mitochondria have emerged as an intriguing target for anti-cancer drugs, inherent to vast majority if not all types of tumours. Drugs that target mitochondria and exert anti-cancer activity have become a focus of recent research due to their great clinical potential (which has not been harnessed thus far). The exceptional potential of mitochondria as a target for anti-cancer agents has been reinforced by the discouraging finding that even tumours of the same type from individual patients differ in a number of mutations. This is consistent with the idea of personalised therapy, an elusive goal at this stage, in line with the notion that tumours are unlikely to be treated by agents that target only a single gene or a single pathway. This endows mitochondria, an invariant target present in all tumours, with an exceptional momentum. This train of thoughts inspired us to define a class of anti-cancer drugs acting by way of mitochondrial ‘destabilisation’, termed ‘mitocans’. In this communication, we define mitocans (many of which have been known for a long time) and classify them into several classes based on their molecular mode of action. We chose the targets that are of major importance from the point of view of their role in mitochondrial destabilisation by small compounds, some of which are now trialled as anti-cancer agents. The classification starts with targets at the surface of mitochondria and ending up with those in the mitochondrial matrix. The purpose of this review is to present in a concise manner the classification of compounds that hold a considerable promise as potential anti-cancer drugs.  相似文献   
999.
Highlights? Loss of AMPKα1 cooperates with the Myc oncogene to accelerate lymphomagenesis ? AMPKα dysfunction enhances aerobic glycolysis (Warburg effect) ? Inhibiting HIF-1α reverses the metabolic effects of AMPKα loss ? HIF-1α mediates the growth advantage of tumors with reduced AMPK signaling  相似文献   
1000.
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