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   101342篇
  免费   10279篇
  国内免费   6254篇
电工技术   6889篇
技术理论   8篇
综合类   9375篇
化学工业   15539篇
金属工艺   5233篇
机械仪表   6004篇
建筑科学   7768篇
矿业工程   2626篇
能源动力   2491篇
轻工业   11804篇
水利工程   2608篇
石油天然气   4232篇
武器工业   982篇
无线电   11520篇
一般工业技术   10140篇
冶金工业   3520篇
原子能技术   1190篇
自动化技术   15946篇
  2024年   500篇
  2023年   1663篇
  2022年   3398篇
  2021年   4480篇
  2020年   3550篇
  2019年   2626篇
  2018年   2945篇
  2017年   3295篇
  2016年   2948篇
  2015年   4499篇
  2014年   5876篇
  2013年   6924篇
  2012年   8043篇
  2011年   8599篇
  2010年   7840篇
  2009年   7193篇
  2008年   7259篇
  2007年   6789篇
  2006年   5976篇
  2005年   4851篇
  2004年   3460篇
  2003年   2798篇
  2002年   2867篇
  2001年   2400篇
  2000年   1720篇
  1999年   1339篇
  1998年   829篇
  1997年   640篇
  1996年   568篇
  1995年   432篇
  1994年   338篇
  1993年   272篇
  1992年   228篇
  1991年   172篇
  1990年   130篇
  1989年   108篇
  1988年   60篇
  1987年   47篇
  1986年   36篇
  1985年   19篇
  1984年   11篇
  1983年   10篇
  1982年   17篇
  1981年   15篇
  1980年   26篇
  1979年   14篇
  1976年   7篇
  1973年   6篇
  1959年   9篇
  1951年   18篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
31.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
32.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
33.
34.
35.
Photocatalysts often show excellent performances on the basis of their surface state of exposed faces with high reactivity, but unfortunately surfaces of this type are usually concealed into the interior of crystals for their high surface energy. We report here a possibility that for fluorine-terminated surfaces of monoclinic ZrO2, these higher-energy surfaces could be retained and exposed. Urchin-like ZrO2 hollow microspheres (UZHS) composed of nanoribbons with exposed (010) facets are obtained through a fluoride mediately solvothermal method. We prove the stabilization effect of fluorine adsorption on (010) facets by density functional theory calculations. More interestingly, UZHS exhibit tunable photocatalytic selectivity in dye degradation. The fluorinated UZHS exhibit good performances both on decomposing Congo red (CR) and methylene blue, while the surface-modified UZHS by calcination only favor decomposition of CR.  相似文献   
36.
陈万志  徐东升  张静  唐雨 《计算机应用》2019,39(4):1089-1094
针对工业控制系统传统单一检测算法模型对不同攻击类型检测率和检测速度不佳的问题,提出一种优化支持向量机和K-means++算法结合的入侵检测模型。首先利用主成分分析法(PCA)对原始数据集进行预处理,消除其相关性;其次在粒子群优化(PSO)算法的基础上加入自适应变异过程避免在训练的过程中陷入局部最优解;然后利用自适应变异粒子群优化(AMPSO)算法优化支持向量机的核函数和惩罚参数;最后利用密度中心法改进K-means算法与优化后的支持向量机组合成入侵检测模型,从而实现工业控制系统的异常检测。实验结果表明,所提方法在检测速度和对各类攻击的检测率上得到明显提升。  相似文献   
37.
38.
39.
40.
Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation.  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