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   1208篇
  免费   99篇
  国内免费   73篇
电工技术   4篇
综合类   55篇
化学工业   460篇
金属工艺   34篇
机械仪表   49篇
建筑科学   36篇
矿业工程   3篇
能源动力   2篇
轻工业   503篇
石油天然气   10篇
无线电   54篇
一般工业技术   113篇
冶金工业   10篇
原子能技术   17篇
自动化技术   30篇
  2024年   6篇
  2023年   24篇
  2022年   51篇
  2021年   82篇
  2020年   30篇
  2019年   47篇
  2018年   44篇
  2017年   46篇
  2016年   57篇
  2015年   58篇
  2014年   88篇
  2013年   99篇
  2012年   94篇
  2011年   109篇
  2010年   94篇
  2009年   62篇
  2008年   39篇
  2007年   47篇
  2006年   67篇
  2005年   34篇
  2004年   35篇
  2003年   13篇
  2002年   11篇
  2001年   20篇
  2000年   21篇
  1999年   14篇
  1998年   13篇
  1997年   9篇
  1996年   3篇
  1995年   7篇
  1994年   5篇
  1993年   9篇
  1992年   7篇
  1991年   8篇
  1990年   5篇
  1989年   3篇
  1988年   2篇
  1987年   3篇
  1986年   7篇
  1985年   2篇
  1984年   3篇
  1981年   1篇
  1980年   1篇
排序方式: 共有1380条查询结果,搜索用时 15 毫秒
41.
利用自组装的方法在金电极上制得巯基丁二胺铜(Ⅱ)/纳米金胶/前列腺特异性抗体(抗PSA)免疫修饰电极。用该修饰电极对PSA进行检测,发现其循环伏安图的氧化还原峰电流都随PSA浓度的增高而降低,峰电位没有变化。其最佳实验条件包括:pH5.2的0.1mol/L磷酸盐缓冲液作为底液,以及用示差脉冲方式进行定量测定。结果显示:该传感器的氧化峰电流减少值与PSA浓度在0.005-0.48μg/mL范围内成线性关系,检测下限为2ng/mL.在40 ng/mLPSA浓度下八次测量相对标准偏差为2.9%,该免疫传感器的稳定性和抗干扰性都较好。对血清中的PSA进行检测,获得满意的结果。  相似文献   
42.
采用电化学和荧光方法研究了Pt(Ⅱ) 水合物与甲胎蛋白(AFP)相互作用的机理,发现它们具有较强的相互结合能力.文中对Pt(Ⅱ)- AFP体系的适宜反应条件、影响因素及信号强度与AFP浓度的关系进行了研究.结果表明,在一定Pt(Ⅱ)浓度范围内,AFP浓度与其荧光峰电流强度成正比.本方法有较高的灵敏度,对AFP的检出限为10.2ng/mL.考察了共存物质的干扰影响,并对实际血清样品中的AFP进行分析,结果满意.  相似文献   
43.
贺锐  曹光群  陈明清  杨成  杨吉 《化工进展》2007,26(7):991-994
研究了运用分散聚合法,在乙醇/水混合介质中,制备2-丙烯酰胺基-2-甲基丙磺酸(AMPS)与苯乙烯(St)的共聚微球。运用红外、核磁共振、激光光散射和扫描电子显微镜对功能微球进行表征。阐述了该微球对牛血清蛋白(BSA)的吸附量与吸附时间和pH值的关系。结果表明:功能微球对BSA的吸附先随时间的增长而增大,一段时间后达到平衡吸附。当pH值接近BSA等电点(pI=4.7)时,BSA的吸附量达到最大值。  相似文献   
44.
Brain metastases are the most severe tumorous spread during breast cancer disease. They are associated with a limited quality of life and a very poor overall survival. A subtype of extracellular vesicles, exosomes, are sequestered by all kinds of cells, including tumor cells, and play a role in cell-cell communication. Exosomes contain, among others, microRNAs (miRs). Exosomes can be taken up by other cells in the body, and their active molecules can affect the cellular process in target cells. Tumor-secreted exosomes can affect the integrity of the blood-brain barrier (BBB) and have an impact on brain metastases forming. Serum samples from healthy donors, breast cancer patients with primary tumors, or with brain, bone, or visceral metastases were used to isolate exosomes and exosomal miRs. Exosomes expressed exosomal markers CD63 and CD9, and their amount did not vary significantly between groups, as shown by Western blot and ELISA. The selected 48 miRs were detected using real-time PCR. Area under the receiver-operating characteristic curve (AUC) was used to evaluate the diagnostic accuracy. We identified two miRs with the potential to serve as prognostic markers for brain metastases. Hsa-miR-576-3p was significantly upregulated, and hsa-miR-130a-3p was significantly downregulated in exosomes from breast cancer patients with cerebral metastases with AUC: 0.705 and 0.699, respectively. Furthermore, correlation of miR levels with tumor markers revealed that hsa-miR-340-5p levels were significantly correlated with the percentage of Ki67-positive tumor cells, while hsa-miR-342-3p levels were inversely correlated with tumor staging. Analysis of the expression levels of miRs in serum exosomes from breast cancer patients has the potential to identify new, non-invasive, blood-borne prognostic molecular markers to predict the potential for brain metastasis in breast cancer. Additional functional analyzes and careful validation of the identified markers are required before their potential future diagnostic use.  相似文献   
45.
甲啶铂(picoplatin)是一种新型的抗癌药物,但其在体内的作用机制尚不明确.利用荧光光谱技术研究模拟人生理条件(Tris-HCl缓冲溶液体系,pH7.4)下甲啶铂与牛血清白蛋白(BSA)的相互作用,甲啶铂对BSA的内源荧光(336 nm)有猝灭作用.在室温296 K和模拟人体温度310 K条件下,甲啶铂对BSA的...  相似文献   
46.
Due to the fact that surfactant molecules are known to alter the structure (and consequently the function) of a protein, protein–surfactant interactions are very important in the biological, pharmaceutical, and cosmetic industries. Although there are numerous studies on the interactions of albumins with surfactants, the investigations are often performed at fixed environmental conditions and limited to separate surface-active agents and consequently do not present an appropriate comparison between their different types and structures. In the present paper, the interactions between selected cationic, anionic, and nonionic surfactants, namely hexadecylpyridinium chloride (CPC), hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol sorbitan monolaurate, monopalmitate, and monooleate (TWEEN 20, TWEEN 40, and TWEEN 80, respectively) with bovine serum albumin (BSA) were studied qualitatively and quantitatively in an aqueous solution (10 mM cacodylate buffer; pH 5.0 and 7.0) by steady-state fluorescence spectroscopy supported by UV spectrophotometry and CD spectroscopy. Since in the case of all studied systems, the fluorescence intensity of BSA decreased regularly and significantly under the action of the surfactants added, the fluorescence quenching mechanism was analyzed thoroughly with the use of the Stern–Volmer equation (and its modification) and attributed to the formation of BSA–surfactant complexes. The binding efficiency and mode of interactions were evaluated among others by the determination, comparison, and discussion of the values of binding (association) constants of the newly formed complexes and the corresponding thermodynamic parameters (ΔG, ΔH, ΔS). Furthermore, the influence of the structure of the chosen surfactants (charge of hydrophilic head and length of hydrophobic chain) as well as different environmental conditions (pH, temperature) on the binding mode and the strength of the interaction has been investigated and elucidated.  相似文献   
47.
采用溶胶-凝胶-超临界流体干燥法制备了粒径在100 nm以下的纳米掺锶羟基磷灰石(SrHAP),以牛血清白蛋白(BSA)为吸附目标,研究了纳米SrHAP的吸附性能.结果发现在偏酸性条件下,纳米SrHAP比纳米HAP对BSA的吸附量大,表明掺锶后吸附性能提高;但在碱性条件下,纳米SrHAP对BSA的吸附量减小.纳米SrHAP对BSA的吸附是个快速吸附过程,增加Sr/[Ca Sr]原子比XSr和BSA的起始浓度有利于吸附,升高温度不利于吸附.  相似文献   
48.
复相乳化法制备海藻酸钙微球及其释放行为   总被引:3,自引:1,他引:2  
采用复相乳化法制备了载牛血清白蛋白(BSA)的海藻酸钙微球,通过正交实验和单因素分析,以BSA包埋率、微球的载药率和平均粒径为考察指标,优化了该方法的制备参数,使最终制备的微球平均粒径小于10 mm,球形度较好,包埋率约70%,载药率达4%. 随着海藻酸钠质量分数的降低和BSA质量的增大,微球的包埋率下降、载药率升高、平均粒径减小. 微囊化BSA的体外释放曲线表明,该系统存在pH响应特性,尤其在磷酸缓冲液中,被包埋BSA的释放速率较快. 电泳结果表明,BSA的分子结构并未受制备过程的影响. 因此,该微囊化方法有望用于蛋白类药物的控释制剂,使其免受胃酸等的破坏,达到肠部释药的目的.  相似文献   
49.
《中国造纸》2019,38(3):82-82
本实验建立在之前对含淀粉乳胶涂料的流变特性和动态保水性的研究成果基础之上。前期研究表明,淀粉胶乳的流变性和动态保水性不同于传统熟化涂布淀粉。本实验采用血清置换法研究了水膨胀淀粉纳米粒子的基本性能及其胶体行为。结果表明,淀粉胶乳是由微粒和少量可溶性聚合物组成的复杂体系。提高交联度会减少可溶性组分,并降低分散黏度。实验室圆柱形涂布机形成的涂层显示,丁苯胶乳具有可塑性,在压光过程中起到润滑剂的作用,有助于提高纸张光泽度。将生物胶乳与羟乙基淀粉(接枝聚合物)交联可以提高涂料的保水性,但是低交联Bio-A的使用则会降低涂布纸的光泽度。  相似文献   
50.
The early detection of diabetic nephropathy (DN) in mice is necessary for the development of drugs and functional foods. The purpose of this study was to identify genes that are significantly upregulated in the early stage of DN progression and develop a novel model to non-invasively monitor disease progression within living animals using in vivo imaging technology. Streptozotocin (STZ) treatment has been widely used as a DN model; however, it also exhibits direct cytotoxicity to the kidneys. As it is important to distinguish between DN-related and STZ-induced nephropathy, in this study, we compared renal responses induced by the diabetic milieu with two types of STZ models: multiple low-dose STZ injections with a high-fat diet and two moderate-dose STZ injections to induce DN. We found 221 genes whose expression was significantly altered during DN development in both models and identified serum amyloid A3 (Saa3) as a candidate gene. Next, we applied the Saa3 promoter-driven luciferase reporter (Saa3-promoter luc mice) to these two STZ models and performed in vivo bioluminescent imaging to monitor the progression of renal pathology. In this study, to further exclude the possibility that the in vivo bioluminescence signal is related to renal cytotoxicity by STZ treatment, we injected insulin into Saa3-promoter luc mice and showed that insulin treatment could downregulate renal inflammatory responses with a decreased signal intensity of in vivo bioluminescence imaging. These results strongly suggest that Saa3 promoter activity is a potent non-invasive indicator that can be used to monitor DN progression and explore therapeutic agents and functional foods.  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