全文获取类型
收费全文 | 21787篇 |
免费 | 2300篇 |
国内免费 | 737篇 |
专业分类
电工技术 | 1407篇 |
综合类 | 593篇 |
化学工业 | 5239篇 |
金属工艺 | 583篇 |
机械仪表 | 1133篇 |
建筑科学 | 260篇 |
矿业工程 | 171篇 |
能源动力 | 3712篇 |
轻工业 | 1345篇 |
水利工程 | 70篇 |
石油天然气 | 82篇 |
武器工业 | 33篇 |
无线电 | 3993篇 |
一般工业技术 | 3628篇 |
冶金工业 | 268篇 |
原子能技术 | 230篇 |
自动化技术 | 2077篇 |
出版年
2024年 | 70篇 |
2023年 | 670篇 |
2022年 | 1427篇 |
2021年 | 1706篇 |
2020年 | 979篇 |
2019年 | 813篇 |
2018年 | 793篇 |
2017年 | 1008篇 |
2016年 | 965篇 |
2015年 | 963篇 |
2014年 | 1336篇 |
2013年 | 1409篇 |
2012年 | 1376篇 |
2011年 | 1848篇 |
2010年 | 1241篇 |
2009年 | 1206篇 |
2008年 | 1070篇 |
2007年 | 1029篇 |
2006年 | 865篇 |
2005年 | 642篇 |
2004年 | 508篇 |
2003年 | 466篇 |
2002年 | 393篇 |
2001年 | 334篇 |
2000年 | 267篇 |
1999年 | 195篇 |
1998年 | 282篇 |
1997年 | 188篇 |
1996年 | 144篇 |
1995年 | 106篇 |
1994年 | 90篇 |
1993年 | 57篇 |
1992年 | 57篇 |
1991年 | 57篇 |
1990年 | 50篇 |
1989年 | 46篇 |
1988年 | 30篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Providing performance guarantees for arriving traffic flows has become an important measure for today’s routing and switching systems. However, none of current scheduling algorithms built on CICQ (combined input and cross-point buffered) switches can provide flow level performance guarantees. Aiming at meeting this requirement, the feasibility of implementing flow level scheduling is discussed thoroughly. Then, based on the discussion, it comes up with a hybrid and stratified fair scheduling (HSFS) scheme, which is hierarchical and hybrid, for CICQ switches. With HSFS, each input port and output port can schedule variable length packets independently with a complexity of O(1). Theoretical analysis show that HSFS can provide delay bound, service rate and fair performance guarantees without speedup. Finally, we implement HSFS in SPES (switch performance evaluation system) to verify the analytical results. 相似文献
42.
43.
Sofia Cotton Dylan Ferreira Janine Soares Andreia Peixoto Marta Relvas-Santos Rita Azevedo Paulina Piairo Lorena Diguez Carlos Palmeira Luís Lima Andr M. N. Silva Lúcio Lara Santos Jos Alexandre Ferreira 《International journal of molecular sciences》2021,22(4)
Esophageal cancer (EC) is a life-threatening disease, demanding the discovery of new biomarkers and molecular targets for precision oncology. Aberrantly glycosylated proteins hold tremendous potential towards this objective. In the current study, a series of esophageal squamous cell carcinomas (ESCC) and EC-derived circulating tumor cells (CTCs) were screened by immunoassays for the sialyl-Tn (STn) antigen, a glycan rarely expressed in healthy tissues and widely observed in aggressive gastrointestinal cancers. An ESCC cell model was glycoengineered to express STn and characterized in relation to cell proliferation and invasion in vitro. STn was found to be widely present in ESCC (70% of tumors) and in CTCs in 20% of patients, being associated with general recurrence and reduced survival. Furthermore, STn expression in ESCC cells increased invasion in vitro, while reducing cancer cells proliferation. In parallel, an ESCC mass spectrometry-based proteomics dataset, obtained from the PRIDE database, was comprehensively interrogated for abnormally glycosylated proteins. Data integration with the Target Score, an algorithm developed in-house, pinpointed the glucose transporter type 1 (GLUT1) as a biomarker of poor prognosis. GLUT1-STn glycoproteoforms were latter identified in tumor tissues in patients facing worst prognosis. Furthermore, healthy human tissues analysis suggested that STn glycosylation provided cancer specificity to GLUT1. In conclusion, STn is a biomarker of worst prognosis in EC and GLUT1-STn glycoforms may be used to increase its specificity on the stratification and targeting of aggressive ESCC forms. 相似文献
44.
运用转子平衡理论,对工具系统实施平衡技术时,分析了校正面数量的选择、校正面位置的确定、平衡方法的选择等平衡工艺的主要方面,为工具系统的合理设计、制造和使用提供指导. 相似文献
45.
Florian A. Schmid J. Koudy Williams Thomas M. Kessler Arnulf Stenzl Wilhelm K. Aicher Karl-Erik Andersson Daniel Eberli 《International journal of molecular sciences》2021,22(8)
Urinary incontinence (UI) is a major problem in health care and more than 400 million people worldwide suffer from involuntary loss of urine. With an increase in the aging population, UI is likely to become even more prominent over the next decades and the economic burden is substantial. Among the different subtypes of UI, stress urinary incontinence (SUI) is the most prevalent and focus of this review. The main underlying causes for SUI are pregnancy and childbirth, accidents with direct trauma to the pelvis or medical treatments that affect the pelvic floor, such as surgery or irradiation. Conservative approaches for the treatment of SUI are pelvic physiotherapy, behavioral and lifestyle changes, and the use of pessaries. Current surgical treatment options include slings, colposuspensions, bulking agents and artificial urinary sphincters. These treatments have limitations with effectiveness and bear the risk of long-term side effects. Furthermore, surgical options do not treat the underlying pathophysiological causes of SUI. Thus, there is an urgent need for alternative treatments, which are effective, minimally invasive and have only a limited risk for adverse effects. Regenerative medicine is an emerging field, focusing on the repair, replacement or regeneration of human tissues and organs using precursor cells and their components. This article critically reviews recent advances in the therapeutic strategies for the management of SUI and outlines future possibilities and challenges. 相似文献
46.
Jihao Wang Yufen Han Zhiyang Xu Xiaozhen Yang Seeram Ramakrishna Yong Liu 《大分子材料与工程》2021,306(4):2000724
Polymer systems have typical multiscale characteristics, both in space and time. The mesoscopic properties of polymers are difficult to describe through traditional experimental approaches. Dissipative particle dynamics (DPD) is a simulation method used for solving mesoscale problems of complex fluids and soft matter. The mesoscopic properties of polymer systems, such as conformation, dynamics, and transport properties, have been studied extensively using DPD. This paper briefly summarizes the application of DPD to research involving microchannel flow, electrospinning, free-radical polymerization, polymer self-assembly processes, polymer electrolyte fuel cells, and biomedical materials. The main features and possible development avenues of DPD are described as well. 相似文献
47.
M.L. Zhang Y.D. Yan Z.Y. Hou L.A. Fan Z. Chen D.X. Tang 《Journal of Alloys and Compounds》2007,440(1-2):362-366
Mg–Li alloys have been prepared by electrolysis in a molten salt electrolyte of 50% LiCl–50% KCl (mass%) at low temperature of 420–510 °C. The effects of electrolytic temperature and cathodic current density on alloy formation rate and current efficiency were studied. For the deposition of metallic lithium on the cathode consisting of solid Mg and liquid Mg–Li, both electrolytic temperature and cathodic current density have no obvious influence on current efficiency; while for the deposition of metallic lithium on the solid magnesium cathode, both electrolytic temperature and cathodic current density greatly affect alloy formation rate and current efficiency. The optimum electrolysis condition is—molten salt mixture, LiCl:KCl = 1:1 (mass%), electrolytic temperature: 480 °C, cathode current density: 1.13 A cm−2. Mg–Li alloys with low lithium content (about 25 wt% Li) were prepared via electrolysis at low temperature following by thermal treatment at higher temperature. 相似文献
48.
对Accu Roll轧管机的产生背景进行了回顾,对目前国内Accu Roll轧管机的使用现状进行了分析,在肯定其优点的同时,指出了该类轧管机存在的共同问题,提出了完善轧管机性能的可能途径及选择轧管机应注意的问题。 相似文献
49.
液压气动缸筒用高精度冷拔钢管生产的回顾与展望 总被引:2,自引:2,他引:2
介绍了近年来我国液压气动缸筒用高精度冷拔钢管生产的进展及其现状,分析了影响产品尺寸精度的因素,提出了改进措施,指出了发展方向。 相似文献
50.
The objective of this work is to study the transfer of oxygen from gas to liquid phase in an electroflotation cell. The measurements
were performed in a laboratory scale cell using insoluble electrodes, titanium coated with ruthenium oxide as anode and stainless
steel as cathode. The volumetric mass transfer coefficient K
L
a, was characterized for clean tap water as liquid phase for different values of current density (J). The global coefficient
of mass transfer based on the liquid film, K
L
, and the specific interfacial area, a, were characterized. A model which relates K
L
a to current density was established. Different evaluation criteria of oxygen transfer in electroflotation process were determined
and compared with other aeration process. 相似文献