全文获取类型
收费全文 | 498464篇 |
免费 | 48766篇 |
国内免费 | 22311篇 |
专业分类
电工技术 | 33811篇 |
技术理论 | 96篇 |
综合类 | 58493篇 |
化学工业 | 57855篇 |
金属工艺 | 20297篇 |
机械仪表 | 27786篇 |
建筑科学 | 72571篇 |
矿业工程 | 26385篇 |
能源动力 | 16633篇 |
轻工业 | 31827篇 |
水利工程 | 23052篇 |
石油天然气 | 22118篇 |
武器工业 | 5548篇 |
无线电 | 34347篇 |
一般工业技术 | 37599篇 |
冶金工业 | 26328篇 |
原子能技术 | 4748篇 |
自动化技术 | 70047篇 |
出版年
2024年 | 6791篇 |
2023年 | 7571篇 |
2022年 | 11684篇 |
2021年 | 14492篇 |
2020年 | 14477篇 |
2019年 | 11062篇 |
2018年 | 10393篇 |
2017年 | 12987篇 |
2016年 | 15463篇 |
2015年 | 16807篇 |
2014年 | 30627篇 |
2013年 | 27983篇 |
2012年 | 34102篇 |
2011年 | 36460篇 |
2010年 | 28252篇 |
2009年 | 29450篇 |
2008年 | 27215篇 |
2007年 | 34023篇 |
2006年 | 31505篇 |
2005年 | 27210篇 |
2004年 | 23694篇 |
2003年 | 20589篇 |
2002年 | 16988篇 |
2001年 | 14222篇 |
2000年 | 11938篇 |
1999年 | 9575篇 |
1998年 | 7131篇 |
1997年 | 6245篇 |
1996年 | 5564篇 |
1995年 | 4709篇 |
1994年 | 4033篇 |
1993年 | 3006篇 |
1992年 | 2565篇 |
1991年 | 1904篇 |
1990年 | 1639篇 |
1989年 | 1447篇 |
1988年 | 1060篇 |
1987年 | 755篇 |
1986年 | 585篇 |
1985年 | 575篇 |
1984年 | 478篇 |
1983年 | 372篇 |
1982年 | 295篇 |
1981年 | 241篇 |
1980年 | 211篇 |
1979年 | 154篇 |
1978年 | 87篇 |
1977年 | 90篇 |
1976年 | 68篇 |
1975年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
南水北调中线总干渠无在线调蓄水库,对藻类生态调度过程中出现的问题开展生态调度实现策略和实施方式研究。主要实现策略包括:划定自身的调蓄区,隔离生态调度对下游的影响;采用高效的渠池运行方式,减少生态调度时蓄量的反复调整;综合考虑安全、快速、平稳等需求,设定生态调度实施进程和方式。具体实施方式包括:将总干渠划分为流速调控区、调蓄区和正常运行区,分别实施等体积、控制蓄量和闸前常水位方式运行;将生态调度过程划分为充水阶段和泄水阶段,基于流速调控目标值、持续时长和水位降幅约束条件,确定各阶段时长和各分区的闸门群调控方案等。基于2018年3月输水工况,采用明渠一维非恒定流模型,仿真总干渠上游15个渠池的藻类生态调度过程。结果表明,生态调度可在3.5 d内完成,各渠池的平均流速由0.48 m/s增至0.93 m/s,持续时间超过2 h。在整个生态调度过程中,水位变化平稳,水位变幅符合安全阈值要求,下游渠道的正常运行未受生态调度明显影响。 相似文献
2.
LUO Jin-ling LIU Luo-ren 《广东电脑与电讯》2020,1(4):11-13
In view of the problems in the construction of characteristic professional groups in higher vocational colleges, the professional group of "intelligent manufacturing" is taken as the research object, and the "platform + module" suitable for the development
of the industry will be constructed according to the content of the vocational ability planning courses of the post group. The curriculum system establishes the framework of professional groups, and explores and forms a strategic study to optimize and integrate professional group resources. 相似文献
3.
ABSTRACTTo ensure the reasonable application and perfect the theory of decision making with interval multiplicative preference relations (IMPRs), this paper continues to discuss decision making with IMPRs. After reviewing previous consistency concepts for IMPRs, we find that Krej?í’s consistency concept is more flexible and natural than others. However, it is insufficient to address IMPRs only using this concept. Considering this fact, this paper researches inconsistent and incomplete IMPRs that are usually encountered. First, programming models for addressing inconsistent and incomplete IMPRs are constructed. Then, this paper studies the consensus of individual IMPRs and defines a consensus index using the defined correlation coefficient. When the consensus requirement does not satisfy requirement, a programming model for improving consensus level is built, which can ensure the consistency. Subsequently, a procedure for group decision making with IMPRs is offered, and associated examples are provided to specifically show the application of main theoretical results. 相似文献
4.
Zviadi Mestvirishvili Vakhtang Kvatchadze Irakli Bairamashvili Nikoloz Jalabadze Tornike Mestvirishvili 《Materials Science & Technology》2020,36(3):327-333
ABSTRACTA method of ultrafine macro-homogeneous composite powder – B4C–ZrO2 production using a planetary mill was developed. From the macro-homogeneous composite high-density ceramics, B4C–ZrB2 was produced by the method of reactive sintering (in situ) at 2000°C under the pressure of 41–42?MPa. The effect of ZrO2 grain size and of its distribution in the matrix on the consolidation parameters, and the microstructure of the obtained ceramics was studied. 相似文献
5.
《Advanced Powder Technology》2020,31(1):287-299
The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed. 相似文献
6.
In this paper, a nonconforming finite element method (NFEM) is proposed for the constrained optimal control problems (OCPs) governed by a bilinear state equation. The state and adjoint state are approximated by the nonconforming element, and the control is approximated by the orthogonal projection through the state and adjoint state. Some superclose and superconvergence properties are obtained by full use of the distinguish characters of this element, such as the interpolation operator equals the Ritz projection, and the consistency error is one order higher than its interpolation error in the broken energy norm. Finally, some numerical results are provided to verify the theoretical analysis. 相似文献
7.
Focusing on a process where a designer embeds herself in craftspeople’s workshops with the intention of ‘learning from inside’ and ‘making together’; this paper proposes pathways for considering collaboration between designers and craftspeople via digital fabrication and weaving. The tension of forces that make weaving possible, act as an analogy for this collaboration as well as providing the title of the project as ‘One Over, One Under’. The project proposes a mode of working and a spectrum of outcomes where the designer has a first-hand experience of production techniques, engages in a serious and continuous dialogue through making, and develops an intervention that also brings forth her own skill set (introducing digital fabrication and structural variations), thus transforming the conventions and boundaries between established roles and manufacturing techniques. An experiment that resulted in a series of objects considering both the technologies of production and the input of the designer, this process not only increases the potentials that crafts hold for the field of design, but it also offers possibilities of collaboration and a further articulation of the design act. 相似文献
8.
9.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
10.
For an effective optimization of pulp thermoforming and of the moulded pulp products manufactured by this process, a full understanding of the process physics combined with full knowledge of the pressing equipment is necessary. For this reason, in this Addendum, we clarify how the process parameters “Holding time,” “Vacuum time,” “Cycle time,” and “Temperature” were interpreted and subsequently defined for the analysis of the process and product‐related outputs of the thermoforming experiments. 相似文献