全文获取类型
收费全文 | 20557篇 |
免费 | 2738篇 |
国内免费 | 2232篇 |
专业分类
电工技术 | 2187篇 |
综合类 | 2760篇 |
化学工业 | 343篇 |
金属工艺 | 230篇 |
机械仪表 | 1176篇 |
建筑科学 | 752篇 |
矿业工程 | 354篇 |
能源动力 | 383篇 |
轻工业 | 219篇 |
水利工程 | 446篇 |
石油天然气 | 235篇 |
武器工业 | 289篇 |
无线电 | 3324篇 |
一般工业技术 | 1198篇 |
冶金工业 | 979篇 |
原子能技术 | 186篇 |
自动化技术 | 10466篇 |
出版年
2024年 | 32篇 |
2023年 | 253篇 |
2022年 | 377篇 |
2021年 | 507篇 |
2020年 | 620篇 |
2019年 | 627篇 |
2018年 | 574篇 |
2017年 | 754篇 |
2016年 | 838篇 |
2015年 | 886篇 |
2014年 | 1231篇 |
2013年 | 1667篇 |
2012年 | 1404篇 |
2011年 | 1558篇 |
2010年 | 1273篇 |
2009年 | 1332篇 |
2008年 | 1433篇 |
2007年 | 1601篇 |
2006年 | 1290篇 |
2005年 | 1180篇 |
2004年 | 983篇 |
2003年 | 869篇 |
2002年 | 729篇 |
2001年 | 602篇 |
2000年 | 460篇 |
1999年 | 391篇 |
1998年 | 315篇 |
1997年 | 278篇 |
1996年 | 217篇 |
1995年 | 204篇 |
1994年 | 208篇 |
1993年 | 163篇 |
1992年 | 115篇 |
1991年 | 98篇 |
1990年 | 94篇 |
1989年 | 57篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 28篇 |
1983年 | 36篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1966年 | 7篇 |
1958年 | 8篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Andrea Angius Antonio Mario Scanu Caterina Arru Maria Rosaria Muroni Vincenzo Rallo Giulia Deiana Maria Chiara Ninniri Ciriaco Carru Alberto Porcu Giovanna Pira Paolo Uva Paolo Cossu-Rocca Maria Rosaria De Miglio 《International journal of molecular sciences》2021,22(4)
Colorectal cancer (CRC) is a leading cause of cancer death worldwide, and about 20% is metastatic at diagnosis and untreatable. Increasing evidence suggests that the heterogeneous nature of CRC is related to colorectal cancer stem cells (CCSCs), a small cells population with stemness behaviors and responsible for tumor progression, recurrence, and therapy resistance. Growing knowledge of stem cells (SCs) biology has rapidly improved uncovering the molecular mechanisms and possible crosstalk/feedback loops between signaling pathways that directly influence intestinal homeostasis and tumorigenesis. The generation of CCSCs is probably connected to genetic changes in members of signaling pathways, which control self-renewal and pluripotency in SCs and then establish function and phenotype of CCSCs. Particularly, various deregulated CCSC-related miRNAs have been reported to modulate stemness features, controlling CCSCs functions such as regulation of cell cycle genes expression, epithelial-mesenchymal transition, metastasization, and drug-resistance mechanisms. Primarily, CCSC-related miRNAs work by regulating mainly signal pathways known to be involved in CCSCs biology. This review intends to summarize the epigenetic findings linked to miRNAome in the maintenance and regulation of CCSCs, including their relationships with different signaling pathways, which should help to identify specific diagnostic, prognostic, and predictive biomarkers for CRC, but also develop innovative CCSCs-targeted therapies. 相似文献
2.
3.
《International Journal of Hydrogen Energy》2022,47(58):24569-24583
Hydrogen generation from renewable energy resources is considered as a suitable solution to solve the problems related to the energy sector and the reduction of greenhouse gases. The aim of this study is to provide an integrated framework for identifying suitable areas for the construction of wind farms to produce hydrogen. For this purpose, a combined method of Geographic Information System (GIS) and multi-criteria decision making (MCDM) has been used to locate the power plant in Yazd province. The GIS method in the present study consisted of two parts: constraints and criteria. The constraint section included areas that were unsuitable for the construction of wind farms to produce power and hydrogen. In the present study, various aspects such as physical, economic and environmental had been considered as constraints. In the criteria section, eight different criteria from technical aspects (including average wind speed, hydrogen production potential, land slope) and economic aspects (including distance to electricity grid, distance to urban areas, distance to road, distance to railway and distance to centers of High hydrogen consumption) had been investigated. The MCDM tool had been used to weigh the criteria and identify suitable areas. Analytic Hierarchy Process (AHP) technique was used for weighting the criteria. The results of AHP weighting method showed that economic criteria had the highest importance with a value of 0.681. The most significant sub-criterion was the distance to urban areas and the least significant sub-criterion was the distance to power transmission lines. The results of GIS-MCDM analysis had shown that the most proper areas were in the southern and central sectors of Yazd province. In addition, the feasibility of hydrogen production from wind energy had shown that this province had the capacity to generate hydrogen at the rate of 53.6–128.6 tons per year. 相似文献
4.
北极地区战略地位的提高促进了极区各种应用的快速发展,冰下水声通信成为其中一个热点问题。为了研究冰下单载波水声通信性能,在黄海冰区开展冰下试验。重点分析了内嵌锁相环的多通道判决反馈均衡(Multi-channelDecision Feedback Equalization, M-DFE)技术在冰下水声通信中抗多途时延的能力,研究比较了改进比例归一化最小均方(Improved Proportional normalized Least Mean Square, IPNLMS)算法和递归最小二乘(Recursive Least Squares,RLS)算法的均衡性能。试验结果表明IPNLMS和RLS都能克服信道多途效应带来的影响。在牺牲计算复杂度的前提下,RLS具有更好的均衡效果,M-DFE在冰下环境中能够有效消除码间干扰。 相似文献
5.
Diabetes mellitus is a major cause of chronic kidney disease and end-stage renal disease. However, the management of chronic kidney disease, particularly diabetes, requires vast improvements. Recently, sodium-glucose cotransporter-2 (SGLT2) inhibitors, originally developed for the treatment of diabetes, have been shown to protect against kidney injury via glycemic control, as well as various other mechanisms, including blood pressure and hemodynamic regulation, protection from lipotoxicity, and uric acid control. As such, regulation of these mechanisms is recommended as an effective multidisciplinary approach for the treatment of diabetic patients with kidney disease. Thus, SGLT2 inhibitors are expected to become key drugs for treating diabetic kidney disease. This review summarizes the recent clinical evidence pertaining to SGLT2 inhibitors as well as the mechanisms underlying their renoprotective effects. Hence, the information contained herein will advance the current understanding regarding the pleiotropic effects of SGLT2 inhibitors, while promoting future research in the field. 相似文献
6.
7.
《International Journal of Hydrogen Energy》2022,47(29):13990-14007
Hydrogen can be produced via many different technologies; however, from a safety standpoint there exists no framework for selecting the right technology. Here, we provide a structured framework for assessment of the most desirable hydrogen production technology based on efficiency, safety, and infrastructure, by using a Multi-Criteria Decision-Making (MCDM) integrated Analytic Hierarchy Process (AHP) and life-cycle index (LInX) approach. We apply this modified MCDM approach to steam methane reforming (SMR), autothermal reforming, partial oxidation, alkaline electrolysis, polymer electrode membrane electrolysis, and solid oxide electrolyzer cell processes. Our results show that SMR is the most desirable technology based on the efficiency, safety, and infrastructure criteria. We employ fuzzy set theory to address subjectivity and uncertainty challenges in the data and found that although the technologies based on electrolysis have an environmental advantage, they exhibit higher uncertainties than non-renewable technologies such as SMR. Overall, this new framework addresses the challenge to find the most desirable and safer technology for hydrogen production. 相似文献
8.
Hua Yang Shi-Xiao Wei Han Chen Lang Chen Chak-Tong Au Ting-Liang Xie Shuang-Feng Yin 《American Institute of Chemical Engineers》2022,68(10):e17810
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min. 相似文献
9.
为了解决当前模糊测试技术中变异存在一定的盲目性以及变异生成的样本大多经过相同的高频路径的问题,提出并实现了一种基于轻量级程序分析技术的二进制程序模糊测试方法。首先对目标二进制程序进行静态分析来筛选在模糊测试过程中阻碍样本文件深入程序内部的比较指令;随后对目标文件进行插桩来获取比较指令中操作数的具体值,并根据该具体值为比较指令建立实时的比较进度信息,通过比较进度衡量样本的重要程度;然后基于模糊测试过程中实时的路径覆盖信息为经过稀有路径的样本增加其被挑选进行变异的概率;最后根据比较进度信息并结合启发式策略有针对性地对样本文件进行变异,通过变异引导提高模糊测试中生成能够绕过程序规约检查的有效样本的效率。实验结果表明,所提方法发现crash及发现新路径的能力均优于模糊测试工具AFL-Dyninst。 相似文献
10.