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   110533篇
  免费   8457篇
  国内免费   6966篇
  125956篇
  2024年   215篇
  2023年   1451篇
  2022年   3239篇
  2021年   5476篇
  2020年   3576篇
  2019年   4374篇
  2018年   4353篇
  2017年   3229篇
  2016年   4599篇
  2015年   6677篇
  2014年   7863篇
  2013年   8315篇
  2012年   9960篇
  2011年   8869篇
  2010年   5444篇
  2009年   4746篇
  2008年   5585篇
  2007年   4923篇
  2006年   4370篇
  2005年   3333篇
  2004年   2933篇
  2003年   2531篇
  2002年   2205篇
  2001年   2002篇
  2000年   1861篇
  1999年   1841篇
  1998年   1017篇
  1997年   1137篇
  1996年   1017篇
  1995年   919篇
  1994年   942篇
  1993年   666篇
  1992年   993篇
  1991年   838篇
  1990年   613篇
  1989年   559篇
  1988年   485篇
  1987年   411篇
  1986年   388篇
  1985年   390篇
  1984年   211篇
  1983年   197篇
  1982年   137篇
  1981年   114篇
  1980年   107篇
  1979年   115篇
  1978年   78篇
  1977年   60篇
  1974年   74篇
  1972年   62篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
Mechanical loading can induce or antagonize the extracellular matrix (ECM) synthesis, proliferation, migration, and inflammatory responses of annulus fibrosus cells (AFCs), depending on the loading mode and level. Caveolin-1 (Cav1), the core protein of caveolae, plays an important role in cellular mechanotransduction and inflammatory responses. In the present study, we presented that AFCs demonstrated different behaviors when subjected to cyclic tensile strain (CTS) for 24 h at a magnitude of 0%, 2%, 5% and 12%, respectively. It was found that 5% CTS had positive effects on cell proliferation, migration and anabolism, while 12% CTS had the opposite effects. Besides, cells exposed to interleukin-1β stimulus exhibited an increase expression in inflammatory genes, and the expression of these genes decreased after exposure to moderate mechanical loading with 5% CTS. In addition, 5% CTS decreased the level of Cav1 and integrin β1 and exhibited anti-inflammatory effects. Moreover, the expression of integrin β1 and p-p65 increased in AFCs transfected with Cav1 plasmids. In vivo results revealed that moderate mechanical stimulation could recover the water content and morphology of the discs. In conclusion, moderate mechanical stimulation restrained Cav1-mediated signaling pathway and exhibited anti-inflammatory effects on AFCs. Together with in vivo results, this study expounds the underlying molecular mechanisms on the effect of moderate mechanical stimulation on intervertebral discs (IVDs) and may provide a new therapeutic strategy for the treatment of IVD degeneration.  相似文献   
992.
993.
Zhao  X.  Chen  L.  Ren  Q.  Wu  Z.  Fang  S.  Jiang  Y.  Chen  Y.  Zhong  Y.  Wang  D.  Wu  J.  Zhang  G. 《Applied Biochemistry and Microbiology》2021,57(3):344-350
Applied Biochemistry and Microbiology - A pyridine-transforming strain P2 was isolated from sewage collected from Guangzhou oil stain field(China).According to the system analysis, it was...  相似文献   
994.
降脂红曲的菌学性质及化学成分的分析   总被引:4,自引:0,他引:4  
本文对No.4降脂红曲的生理特性进行了分析,测定了其一般的化学成分,将No.4红曲米的色调和色价与其它红曲米进行了对比,确定了该红曲的最适培养条件,制定了No.4红曲米的质量标准,并验证了它可作为糖化酶的生产菌。  相似文献   
995.
目的研究miR-106a-5p对鼻咽癌细胞SUNE2增殖和迁移的影响。 方法将体外培养的鼻咽癌细胞SUNE2分成对照组(细胞未做任何处理)、Anti-NC组(转染阴性对照抑制剂)、Anti-miR-106a-5p组(转染miR-106a-5p抑制剂)、后期实验另设Anti-miR-106a-5p-inhibitor+si-NC组(转染miR-106a-5p抑制剂、siRNA阴性对照)、Anti-miR-106a-5p-inhibitor+si-PTEN组(转染miR-106a-5p抑制剂、PTEN siRNA),采用Realtime PCR测定miR-106a-5p表达,MTT法检测增殖,Transwell小室检测细胞侵袭和迁移能力变化,用Western blot方法测定vimentin、E-cadherin蛋白表达。在线靶基因预测软件预测miR-106a-5p的靶基因可能为PTEN,双荧光素酶报告系统鉴定miR-106a-5p和PTEN的靶向关系。两组间比较用独立样本t检验,多组间比较采用单因素方差分析,组间两两比较采用LSD-t检验。 结果与正常鼻咽上皮细胞NP69比较,鼻咽癌细胞CNE-2、HK1、SUNE2中miR-106a-5p水平(1.00±0.11比1.84±0.13、2.19±0.14、2.87±0.25)升高,差异具有统计学意义(P < 0.05)。与对照组、Anti-NC组比较,Anti-miR-106a-5p组鼻咽癌细胞miR-106a-5p水平(1.00±0.10、0.99±0.12比0.76±0.08)降低,OD值(0.56±0.05、0.57±0.04比0.32±0.02),细胞侵袭数[(128.47±11.65)个、(129.84±10.93)个比(85.12±6.75)个],迁移数[(182.51±14.81)个、(180.68±17.64)个比(122.01±11.62)个],vimentin蛋白表达水平(0.84±0.09、0.82±0.07比0.30±0.05)降低,E-cadherin蛋白表达水平(0.29±0.04、0.28±0.05比0.76±0.08)升高,差异具有统计学意义(P均< 0.05)。与Anti-miR-106a-inhibitor+si-NC组比较,Anti-miR-106a-inhibitor+si-PTEN组细胞OD值(0.33±0.03比0.52±0.05)、侵袭数[(84.16±5.91)个比(105.79±8.63)个]、迁移数[(118.42±10.25)个比(164.28±12.05)个]、vimentin蛋白表达水平(0.34±0.06比0.68±0.05)均升高,E-cadherin蛋白表达水平(0.72±0.06比0.29±0.05)降低,差异具有统计学意义(P均< 0.05)。 结论miR-106a-5p可通过靶向调控PTEN抑制鼻咽癌细胞SUNE2增殖和迁移潜能。  相似文献   
996.
Biomechanics and Modeling in Mechanobiology - Finite element human body models (HBMs) are used to assess injury risk in a variety of impact scenarios. The ribs are a key structural component within...  相似文献   
997.
Chronic periodontitis (CP) is one of the most common oral diseases, which is characterized by the loss of connective tissue and alveolar bone in adults. AZD8835, a novel dual phosphoinositide-3-kinase (PI3K) inhibitor, is currently in phase 1 clinical evaluation to treat breast cancer. However, whether AZD8835 has any effect on teeth and alveolar bone health remains unclear. In the current study, we aimed to investigate the potential effect of AZD8835 in treating CP in vitro and in vivo. We found that AZD8835 could inhibit osteoclast differentiation, bone resorption, and downregulate the expression of osteoclast marker genes, such as tartrate-resistant acid phosphatase (Trap), cathepsin K (Ctsk), V-ATPase d2 (Atp6v0d2), and calcitonin receptor (Ctr). In addition, AZD8835 suppressed osteoclastogenesis by inhibiting receptor activator of nuclear factor kappa B ligand (RANKL)-induced PI3K/protein kinase B (AKT), extracellular signal-regulated kinase, and nuclear factor-κB signaling in BMMs. In vivo, AZD8835 greatly ameliorated alveolar bone (ABL) loss in rats with CP. Meanwhile, histological examination showed fewer osteoclasts in the treatment group. In conclusion, these results indicated that AZD8835 is a promising agent to reduce ABL in CP.  相似文献   
998.
目的观察去泛素化酶RPN11和增殖相关核标记物Ki67在结直肠癌组织中的表达,研究其与结直肠癌肿瘤细胞增殖的相关性及与结直肠癌临床病理特征的关系。方法采用免疫组织化学SABC法检测56例结直癌组织及20例癌旁正常组织中的RPN11和Ki67表达,结合临床病理学资料进行统计分析。结果免疫组织化学染色显示:RPN11及Ki67在结直肠癌组织的阳性表达率明显高于正常结直肠组织;RPN11和Ki67的表达均与肿瘤分化程度、TNM分期、转移有关,而与性别、年龄无明显相关;RPN11与Ki67的表达呈正相关。结论RPN11和Ki67可能共同参与结直肠癌肿瘤细胞的增殖调控,并促进结直肠癌的发生发展以及浸润转移。  相似文献   
999.
A structurally simple molecular 1,10‐phenanthroline‐Cu complex on a mesostructured graphene matrix that can be active and selective toward CO2 reduction over H2 evolution in an aqueous solution is reported. The active sites consist of Cu(I) center in a distorted trigonal bipyramidal geometry, which enables the adsorption of CO2 with η1‐COO‐like configuration to commence the catalysis, with a turnover frequency of ≈45 s?1 at ?1 V versus reversible hydrogen electrode. Using in situ infrared spectroelectrochemical investigation, it is demonstrated that the Cu complex can be reversibly heterogenized near the graphene surface via potential control. An increase of electron density in the complex is observed as a result of the interaction from the electric field, which further tunes the electron distribution in the neighboring CO2. It is also found that the mesostructure of graphene matrix favored CO2 reduction on the Cu center over hydrogen evolution by limiting mass transport from the bulk solution to the electrode surface.  相似文献   
1000.
The reliability and durability of lithium‐ion capacitors (LICs) are severely hindered by the kinetic imbalance between capacitive and Faradaic electrodes. Efficient charge storage in LICs is still a huge challenge, particularly for thick electrodes with high mass loading, fast charge delivery, and harsh working conditions. Here, a unique thermally durable, stable LIC with high energy density from all‐inorganic hydroxyapatite nanowire (HAP NW)‐enabled electrodes and separators is reported. Namely, the LIC device is designed and constructed with the electron/ion dual highly conductive and fire‐resistant composite Li4Ti5O12‐based anode and activated carbon‐based cathode, together with a thermal‐tolerant HAP NW separator. Despite the thick‐electrode configuration, the as‐fabricated all HAP NW‐enabled LIC exhibits much enhanced electrochemical kinetics and performance, especially at high current rates and temperatures. Long cycling lifetime and state‐of‐the‐art areal energy density (1.58 mWh cm?2) at a high mass loading of 30 mg cm?2 are achieved. Benefiting from the excellent fire resistance of HAP NWs, such an unusual LIC exhibits high thermal durability and can work over a wide range of temperatures from room temperature to 150 °C. Taking full advantage of synergistic configuration design, this work sets the stage for designing advanced LICs beyond the research of active materials.  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