全文获取类型
收费全文 | 8449篇 |
免费 | 1147篇 |
国内免费 | 467篇 |
专业分类
电工技术 | 1535篇 |
综合类 | 601篇 |
化学工业 | 1271篇 |
金属工艺 | 175篇 |
机械仪表 | 628篇 |
建筑科学 | 191篇 |
矿业工程 | 105篇 |
能源动力 | 191篇 |
轻工业 | 746篇 |
水利工程 | 67篇 |
石油天然气 | 387篇 |
武器工业 | 47篇 |
无线电 | 1228篇 |
一般工业技术 | 1661篇 |
冶金工业 | 142篇 |
原子能技术 | 294篇 |
自动化技术 | 794篇 |
出版年
2024年 | 48篇 |
2023年 | 189篇 |
2022年 | 281篇 |
2021年 | 313篇 |
2020年 | 342篇 |
2019年 | 303篇 |
2018年 | 314篇 |
2017年 | 373篇 |
2016年 | 436篇 |
2015年 | 397篇 |
2014年 | 554篇 |
2013年 | 635篇 |
2012年 | 580篇 |
2011年 | 666篇 |
2010年 | 415篇 |
2009年 | 455篇 |
2008年 | 446篇 |
2007年 | 468篇 |
2006年 | 414篇 |
2005年 | 320篇 |
2004年 | 323篇 |
2003年 | 279篇 |
2002年 | 189篇 |
2001年 | 164篇 |
2000年 | 188篇 |
1999年 | 135篇 |
1998年 | 112篇 |
1997年 | 125篇 |
1996年 | 105篇 |
1995年 | 74篇 |
1994年 | 67篇 |
1993年 | 52篇 |
1992年 | 43篇 |
1991年 | 58篇 |
1990年 | 33篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 27篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Zhenhua Li Jinjia Liu Jiaqi Zhao Run Shi Geoffrey I. N. Waterhouse Xiao-Dong Wen Tierui Zhang 《Advanced functional materials》2023,33(11):2213672
Methanol steam reforming (MSR) is viewed as an important technology in the growth of a future hydrogen economy, with methanol serving as an easily transportable and storable liquid hydrogen carrier. However, the thermocatalytic MSR reaction is energy intensive as it requires high temperatures. Herein, a novel L-Cu catalyst is successfully fabricated for photo-driven MSR through reduction of CuAl layered double hydroxide (CuAl-LDH) nanosheets. L-Cu offers outstanding activity for the photothermal conversion of methanol and water to hydrogen (160.5 µmol gcat−1 s−1) under ultraviolet-visible irradiation, with this rate being much higher than that achieved for L-Cu at the same temperature in the dark. Characterization studies using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and high-resolution transmission electron microscopy determine that L-Cu catalyst comprise Cu nanoparticles on an amorphous alumina support. Computational calculations reveale that Cu localized surface plasmon resonance effects promote the activation of H2O, thereby underpinning the remarkable hydrogen production rates achieved during photo-driven MSR. This study introduces a novel photothermal strategy for hydrogen generation from methanol, demonstrating the enormous potential of photothermal catalysis in the chemical and energy sectors. 相似文献
92.
93.
柔性直流输电系统接入交流电网后存在高频谐振的风险,研究表明交流电网运行方式变化与高频谐振的产生存在内在关联。针对交直流系统中的高频谐振问题,首先构建了柔性直流输电系统直流侧和交流侧计及串补站的等效阻抗模型,分析了柔性直流输电系统接入交流电网的高频谐振机理。对柔性直流输电系统交流侧运行方式变化(特别是线路发生N-1、N-2故障)下等效阻抗的变化规律进行了理论分析和总结。此外,提出了一种柔性直流输电系统接入交流电网的高频谐振风险运行方式辨识方法,并以某地区电网局部交直流系统实际数据为例进行仿真,验证了所提辨识方法的有效性。 相似文献
94.
针对电力机车和牵引网阻抗参数耦合所引起的牵引供电系统的谐波谐振现象,首先基于阻抗分析法建立了有源滤波器、电力机车和牵引网的小信号阻抗模型,使用广义奈奎斯特判据分析了牵引供电系统谐波谐振的机理以及有源滤波器对牵引供电系统谐波谐振的影响。其次,提出一种基于阻抗重塑的牵引供电系统谐波谐振抑制方法,通过并网点电压前馈的方式在有源滤波器中引入虚拟阻抗,并利用自适应参数设计提升了虚拟阻抗对动态系统的适应性。最后,在Matlab/Simulink中搭建了“牵引网-电力机车-有源滤波器”统一仿真模型,验证有源滤波器的自适应阻抗重塑对谐波谐振抑制的有效性。 相似文献
95.
针对串并联电能质量补偿装置联合运行时潜在的谐波交互影响问题,以串联电压型补偿装置DVR、并联电流型补偿装置APF为例,分析延迟效应的非线性因素对电网残余谐波电流的影响。构建基于DVR与APF联合运行的简化等效阻抗模型,分析潜在并联谐振问题,并给出解决方案。针对常态化重要负荷的谐波补偿问题,对比分析单台式、阵列式APF等两类运行模式的特点及适用场合。针对模块化APF阵列运行损耗问题,提出了基于等损耗微增率补偿策略的集中控制模式,并开展了APF阵列的工程应用案例分析。 相似文献
96.
《Current Opinion in Solid State & Materials Science》2017,21(1):35-42
Ever since the discovery of fullerenes in 1985, nanocarbon has demonstrated a wide range of applications in various areas of science and engineering. Compared with metal, oxide, and semiconductor nanoparticles, the carbon-based nanomaterials have distinct advantages in both biotechnological and biomedical applications due to their inherent biocompatibility. Fluorescent nanodiamond (FND) joined the nanocarbon family in 2005. It was initially developed as a contrast agent for bioimaging because it can emit bright red photoluminescence from negatively charged nitrogen-vacancy centers built in the diamond matrix. A notable application of this technology is to study the cytoplasmic dynamics of living cells by tracking single bioconjugated FNDs in intracellular medium. This article provides a critical review on recent advances and developments of such single particle tracking (SPT) research. It summarizes SPT and related studies of FNDs in cells (such as cancer cell lines) and organisms (including zebrafish embryos, fruit fly embryos, whole nematodes, and mice) using assorted imaging techniques. 相似文献
97.
Photoacoustic‐Guided Surgery with Indocyanine Green‐Coated Superparamagnetic Iron Oxide Nanoparticle Clusters 下载免费PDF全文
Jayesh P. Thawani Ahmad Amirshaghaghi Lesan Yan Joel M. Stein Jessica Liu Andrew Tsourkas 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(37)
A common cause of local tumor recurrence in brain tumor surgery results from incomplete surgical resection. Adjunctive technologies meant to facilitate gross total resection have had limited efficacy to date. Contrast agents used to delineate tumors preoperatively cannot be easily or accurately used in the real‐time operative setting. Although multimodal imaging contrast agents are developed to help the surgeon discern tumor from normal tissue in the operating room, these contrast agents are not readily translatable. This study has developed a novel contrast agent comprised solely of two Food and Drug Administration approved components, indocyanine green (ICG) and superparamagnetic iron oxide (SPIO) nanoparticles—with no additional amphiphiles or carrier materials, to enable preoperative detection by magnetic resonance (MR) imaging and intraoperative photoacoustic (PA) imaging. The encapsulation efficiency of both ICG and SPIO within the formulated clusters is ≈100%, and the total ICG payload is 20–30% of the total weight (ICG + SPIO). The ICG–SPIO clusters are stable in physiologic conditions; can be taken up within tumors by enhanced permeability and retention; and are detectable by MR. In a preclinical surgical resection model in mice, following injection of ICG–SPIO clusters, animals undergoing PA‐guided surgery demonstrate increased progression‐free survival compared to animals undergoing microscopic surgery. 相似文献
98.
Recent advances in the research on the molecular mechanism of cell death and methods for preparation of nanomaterials make the integration of various therapeutic approaches,targeting,and imaging modes into a single nanoscale complex a new trend for the development of future nanotherapeutics.Hence,a novel ellipsoidal composite nanoplatform composed of a magnetic Fe3O4/Fe nanorod core (~120 nm) enwrapped by a catalase (CAT)-imprinted fibrous SiO2/ polydopamine (F-SiO2/PDA) shell with thickness 70 nm was prepared in this work.In vitro experiments showed that the Fe3O4/Fe@F-SiO2/PDA nanoparticles can selectively inhibit the bioactivity of CAT in tumor cells by the molecular imprinting technique.As a result,the H2O2 level in tumor cells was elevated dramatically.At the same time,the Fe3O4/Fe core released Fe ions to catalyze the conversion of H2O2 to ·OH in tumor cells.Eventually,the concentration of ·OH in tumor cells rapidly rose to a lethal level thus triggering apoptosis.Combined with the remarkable near-infrared light (NIR) photothermal effect of the CATimprinted PDA layer,the Fe3O4/Fe@F-SiO2/PDA nanoparticles can effectively kill MCF-7,HeLa,and 293T tumor cells but are not toxic to nontumor cells.Furthermore,these nanoparticles show good capacity for magnetic targeting and suitability for magnetic resonance imaging (MRI).Therefore,the integrated multifunctional nanoplatform opens up new possibilities for high-efficiency visual targeted nonchemo therapy for cancer. 相似文献
99.
Under water-rich conditions, small amphiphilic and hydrophobic drug molecules self-assemble into supramolecular nanostructures. Thus, substantial modifications in their interaction with cellular structures and the ability to reach intracellular targets could happen. Additionally, drug aggregates could be more toxic than the non-aggregated counterparts, or vice versa. Moreover, since self-aggregation reduces the number of effective “monomeric” molecules that interact with the target, the drug potency could be underestimated. In other cases, the activity could be ascribed to the non-aggregated molecule while it stems from its aggregates. Thus, drug self-assembly could mislead from drug throughput screening assays to advanced preclinical and clinical trials. Finally, aggregates could serve as crystallization nuclei. The impact that this phenomenon has on the biological performance of active compounds, the inconsistent and often controversial nature of the published data and the need for recommendations/guidelines as preamble of more harmonized research protocols to characterize drug self-aggregation were main motivations for this review. First, the key molecular and environmental parameters governing drug self-aggregation, the main drug families for which this phenomenon and the methods used for its characterization are described. Then, promising nanotechnology platforms investigated to prevent/control it towards a more efficient drug development process are briefly discussed. 相似文献
100.