全文获取类型
收费全文 | 10799篇 |
免费 | 1094篇 |
国内免费 | 480篇 |
专业分类
电工技术 | 664篇 |
技术理论 | 3篇 |
综合类 | 715篇 |
化学工业 | 1880篇 |
金属工艺 | 686篇 |
机械仪表 | 680篇 |
建筑科学 | 866篇 |
矿业工程 | 330篇 |
能源动力 | 371篇 |
轻工业 | 973篇 |
水利工程 | 261篇 |
石油天然气 | 577篇 |
武器工业 | 117篇 |
无线电 | 1146篇 |
一般工业技术 | 1241篇 |
冶金工业 | 395篇 |
原子能技术 | 96篇 |
自动化技术 | 1372篇 |
出版年
2024年 | 64篇 |
2023年 | 250篇 |
2022年 | 428篇 |
2021年 | 597篇 |
2020年 | 423篇 |
2019年 | 362篇 |
2018年 | 407篇 |
2017年 | 439篇 |
2016年 | 384篇 |
2015年 | 527篇 |
2014年 | 695篇 |
2013年 | 721篇 |
2012年 | 704篇 |
2011年 | 885篇 |
2010年 | 682篇 |
2009年 | 611篇 |
2008年 | 577篇 |
2007年 | 517篇 |
2006年 | 506篇 |
2005年 | 369篇 |
2004年 | 294篇 |
2003年 | 230篇 |
2002年 | 242篇 |
2001年 | 192篇 |
2000年 | 221篇 |
1999年 | 216篇 |
1998年 | 142篇 |
1997年 | 118篇 |
1996年 | 115篇 |
1995年 | 103篇 |
1994年 | 89篇 |
1993年 | 67篇 |
1992年 | 63篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 11篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Duo Wang Xiaoqi Zhu Xiaobo Wang Qin Wang Kangning Yan Guichun Zeng Guanhua Qiu Rong Jiao Xia Lin Jie Chen Qiaoling Yang Wen Qin Junjie Liu Kun Zhang Yan Liu 《Advanced functional materials》2023,33(48):2303869
Tumor adaptation-originated tumor tolerance that compensatory mechanisms (e.g., isocitrate dehydrogenase (IDH) mutation) jointly shape is the dominant obstacle of ROS therapy. Currently, targeting a single pathway fails to fundamentally reverse the complex milieu and diminish tumor adaptation. Herein, a multichannel sonocatalysis amplifier is engineered via one-pot gas diffusion method to attenuate IDH1-mutated cholangiocarcinoma plasticity and tolerance to ROS therapy, wherein triptolide and IR780 are co-loaded in DSPE-mPEG-modified CaCO3 nanoparticles. Triptolide can blockade Nrf2 to cut off glutathione biosynthesis via blockading proteomic communication, and disrupt redox homeostasis to potentiate IR780-mediated sonocatalytic ROS production. ROS-induced mitochondria damages disrupt Ca2+ homeostasis and in turn aggravate ROS accumulation, which cooperates with sonocatalysis and Nrf2 blockade to reprogram mitochondrial energy and substance metabolism (e.g., adenosine triphosphatase and glutathione), hinder DNA self-repair, and impair IDH1-mutation-asired tolerance. Systematic experiments support that these actions in such multichannel sonocatalysis amplifiers indeed disrupt Ca2+/redox homeostasis to disarm robust tumor plasticity and IDH1-mutation-induced tolerance to sonocatalysis therapy against IDH1-mutated cholangiocarcinoma progression. Briefly, the sonocatalysis amplifiers pave a comprehensive avenue to reprogram tumor metabolism, target tumor vulnerability, and attenuate tumor plasticity against genomic instability-raised treatment adaptation. 相似文献
72.
Tunable Optical Mode Ferromagnetic Resonance in FeCoB/Ru/FeCoB Synthetic Antiferromagnetic Trilayers under Uniaxial Magnetic Anisotropy 下载免费PDF全文
Shandong Li Qiang Li Jie Xu Shishen Yan Guo‐Xing Miao Shishou Kang Youyong Dai Jiqing Jiao Yueguang Lü 《Advanced functional materials》2016,26(21):3738-3744
Ferromagnetic resonance (FMR) is one of the most important characteristics of soft magnetic materials, which practically sets the maximum operation speed of these materials. There are two FMR modes in exchange coupled ferromagnet/nonmagnet/ferromagnet sandwich films. The acoustic mode has relatively lower frequency and is widely used in radio‐frequency/microwave devices, while the optical mode is largely neglected due to its tiny permeability even though it supports much higher frequency. Here, a realistic method is reported to enhance the permeability in the optical mode to an applicable level. FeCoB/Ru/FeCoB trilayers are carefully engineered with both uniaxial magnetic anisotropy and antiferromagnetic interlayer exchange coupling. This special magnetic structure exhibits a high optical mode frequency up to 11.28 GHz and a maximum permeability of 200 at resonance. An abnormally low inverse switch field (<200 Oe, less than 1/5 of the single layer) is observed which can effectively switch the system from optical mode with higher frequency into acoustic mode with lower frequency. The optical mode frequency and inverse switch field can be controlled by tailoring the interlayer coupling strengths and the uniaxial anisotropy fields, respectively. The tunable optical mode resonance thus can increase operation frequency while reduce operation field overhead in FMR based devices. 相似文献
73.
A method for synthetic aperture radar (SAR) image despeckling based on a probabilistic generative model in nonsubsampled contourlet transform (NSCT) domain was proposed. The shrinkage estimator in NSCT domain consists of a new type of likelihood ratio and prior ratio, both of which are dependent on the estimated masks for the NSCT coefficients. While the previous probabilistic approaches are restricted to parametric models, the limitation is eliminated and the hybrid density model is applied in this paper. The suggested approach does not make heavy assumptions on the NSCT coefficient distribution, so that it can handle complex NSCT coefficient structures. The likelihood ratio is composed of the hybrid density, and the prior ratio is equipped with the selective neighborhood systems to enhance the detail information. The method can effectively adapt the shrinkage estimator to the redundancy property of the NSCT. The proposed approach was applied to real SAR images despeckling and compared through the SAR image vision effect, the equivalent number of looks, and the edge sustain index. Experimental results show that the proposed approach outperforms previous works involved in the paper with the better despeckling result and edge preservation. 相似文献
74.
采用Graph cut的图像分割分为交互式分割与自动分割,为了弥补交互式分割需要用户的参与、分割结果依赖种子点的选取与模型的建立、需要用户的进一步修正才能得到满意结果等不足,介绍基于相似性的自动图像分割。该方法采用Mean-shift平滑图像、转换成YCbCr空间后将图像分割成若干区域块等方法,建立合适的能量函数后利用最大流/最小割定理求最小割。并通过实验证明,该方法在自动性、准确性、时间效率方面都获得较好结果。 相似文献
75.
为了简化农药检测的预测模型,提高模型预测精度,采用红外光谱技术结合基于变异的紧凑遗传算法对波长变量进行筛选,一定程度上减少了无信息变量和干扰变量。通过不同算法选择的波长变量建立预测模型,mCGA得到的预测均方根偏差平均值是0.198,而与mCGA比较的紧凑遗传算法、简单遗传算法得到的预测均方根偏差平均值分别为0.241、0.289,mCGA具有最小误差。结果表明,采用mCGA进行变量选择,能有效提高模型收敛速度及模型准确度,实现农药含量快速高效的检测。 相似文献
76.
考虑到温度和工艺参数浮动的影响,对休眠双阈值footed多米诺电路的漏电流特性进行了系统的量化研究和比较,得到了不同温度下的最佳休眠状态.基于65和45nm BSIM4模型的HSPICE仿真表明:与业已提出的CHIL(时钟为高,输入均为低电平)状态和CHIH(时钟和输入均为高电平)状态相比,本文提出的CLIL(时钟和输入均为低电平)状态更有利于减小低温下电路的漏电流和高温下的多扇入电路的漏电流.而且,分析了工艺参数的浮动对双阈值footed多米诺电路的漏电流特性的影响,并给出了温度和工艺参数浮动下,双阈值footed多米诺电路漏电流最小的休眠状态. 相似文献
77.
A general approach for the stability analysis of the time-domain finite-element method for electromagnetic simulations 总被引:4,自引:0,他引:4
This paper presents a general approach for the stability analysis of the time-domain finite-element method (TDFEM) for electromagnetic simulations. Derived from the discrete system analysis, the approach determines the stability by analyzing the root-locus map of a characteristic equation and evaluating the spectral radius of the finite element system matrix. The approach is applicable to the TDFEM simulation involving dispersive media and to various temporal discretization schemes such as the central difference, forward difference, backward difference, and Newmark methods. It is shown that the stability of the TDFEM is determined by the material property and by the temporal and spatial discretization schemes. The proposed approach is applied to a variety of TDFEM schemes, which include: (1) time-domain finite-element modeling of dispersive media; (2) time-domain finite element-boundary integral method; (3) higher order TDFEM; and (4) orthogonal TDFEM. Numerical results demonstrate the validity of the proposed approach for stability analysis. 相似文献
78.
对液封直拉(LEC)非掺磷化铟(InP)进行930℃ 80h的退火可重复制备直径为50和75mm的半绝缘 (SI)衬底.退火是在密封的石英管内纯磷(PP)或磷化铁(IP)两种气氛下进行的.测试结果表明IP-SI InP衬底具有很好的电学性质和均匀性,而PP-SI的均匀性和电学参数都很差.在IP-SI样品的PL谱中出现与深缺陷有关的荧光峰.光激电流谱的测量结果表明:在IP气氛下退火获得的半绝缘磷化铟中的缺陷明显比PP-SI磷化铟的要少.并对退火后磷化铟中形成缺陷的机理进行了探讨. 相似文献
79.
Qing Zhang Sinan Deng Jinlin Liu Xiaoxia Zhong Jie He Xianfeng Chen Bowen Feng Yanfei Chen Kostya Ostrikov 《Advanced functional materials》2019,29(5)
Folic acid, due to its high affinity toward folate receptors (FR), is recognized as one of the most promising cancer targeting vectors. However, the inherent defects of low water solubility (1.6 µg mL?1), high sensitivity toward photo‐bleaching, low fluorescent quantum yields (QYs, <0.5%) seriously limit its practical application. Herein, ultrastable, highly luminescent graphene quantum dots (GQDs) that selectively target diverse cancer cells are prepared and tested. The new GQDs present step changes compared to common folic acid through an ≈6250 times increase in water solubility (to ≈10 mg mL?1), more than 150 times in QYs (up to ≈77%), while maintaining luminescence stability up to 98% when subjected to UV, visible light, and heating over 360 min. It is shown that the suppression of nonradiative transitions by amino groups pyrolyzed from pterin plays a key role in the mechanism of high QYs and excellent stability. The functional groups that are likely responsible for the selective targeting of cancer cells with different levels of folate receptor expression on the surface are identified. Collectively with these promising properties, the new functional graphene quantum dots may open a new avenue for cancer diagnosis, drug delivery, and therapies. 相似文献
80.
为了实现四级海况下海上小型浮标与岸基站数据中心之间的实时通信,设计和研制了一种高速率、低延时和高可靠的S频段卫星中继通信终端。该卫星中继通信终端由S频段中继通信机、抛物面天线、伺服跟踪机构、电源变换模块、温度控制器以及耐10 m水压的天线罩体等组成。终端为直径1 m的半球体,质量小于30 kg,最大峰值功耗小于等于130 W。卫星中继通信终端利用快速捕获跟踪卫星信号技术,能在7 s内迅速捕获和跟踪卫星前向链路信号;采用自适应海况可变码率技术提高了数据传输的可靠性。四级海况下,卫星中继通信终端实现了浮标与岸站之间最大2Mb/s高速率实时数据传输,大回路数据通信误码率小于等于10-5。 相似文献