全文获取类型
收费全文 | 17732篇 |
免费 | 1853篇 |
国内免费 | 2360篇 |
专业分类
电工技术 | 288篇 |
技术理论 | 2篇 |
综合类 | 827篇 |
化学工业 | 1612篇 |
金属工艺 | 3113篇 |
机械仪表 | 1217篇 |
建筑科学 | 498篇 |
矿业工程 | 1599篇 |
能源动力 | 507篇 |
轻工业 | 65篇 |
水利工程 | 47篇 |
石油天然气 | 87篇 |
武器工业 | 67篇 |
无线电 | 758篇 |
一般工业技术 | 2618篇 |
冶金工业 | 3719篇 |
原子能技术 | 45篇 |
自动化技术 | 4876篇 |
出版年
2024年 | 91篇 |
2023年 | 545篇 |
2022年 | 773篇 |
2021年 | 789篇 |
2020年 | 828篇 |
2019年 | 829篇 |
2018年 | 766篇 |
2017年 | 788篇 |
2016年 | 895篇 |
2015年 | 791篇 |
2014年 | 1103篇 |
2013年 | 1341篇 |
2012年 | 1563篇 |
2011年 | 1474篇 |
2010年 | 1141篇 |
2009年 | 1433篇 |
2008年 | 871篇 |
2007年 | 1158篇 |
2006年 | 1036篇 |
2005年 | 454篇 |
2004年 | 277篇 |
2003年 | 240篇 |
2002年 | 248篇 |
2001年 | 213篇 |
2000年 | 277篇 |
1999年 | 320篇 |
1998年 | 295篇 |
1997年 | 233篇 |
1996年 | 224篇 |
1995年 | 184篇 |
1994年 | 135篇 |
1993年 | 67篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 41篇 |
1989年 | 23篇 |
1988年 | 70篇 |
1987年 | 105篇 |
1986年 | 87篇 |
1985年 | 31篇 |
1984年 | 34篇 |
1983年 | 15篇 |
1982年 | 6篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
渣金两相氧化锰还原的不可逆过程热力学研究 总被引:3,自引:0,他引:3
将仅能描述近平衡体系发生物理化学变化时物理量间的线性关系式——线性不可逆过程热力学扩展到远离平衡体系,建立了有界面存在的远离平衡的化学反应体系的不可逆过程热力学方程,并将其应用于渣-金间的氧化锰还原反应,得到的氧化锰还原的不可逆过程热力学的动力学方程与实验数据能很好地吻合,这表明不可逆过程热力学可以应用于远离平衡的体系。 相似文献
142.
简要介绍了自主设计制造、具有完全自主知识产权的1 250 mm五机架六辊冷连轧产线工艺及设备特点。重点阐述了冷连轧工艺控制系统的硬件配置、软件架构及核心技术。采用基于简易有限元的轧制力模型及基于成本函数的多目标负荷分配模型,实现了高精度的轧制规程计算。开发了原料板快速启车技术与板形多变量综合最优控制技术,实现了冷轧产品的尺寸精准控制。现场实际应用效果表明,机组稳定运行率达到99.8%以上,不同规格的产品厚度控制精度均达到±0.8%以内,板形控制精度均达到5I以内。 相似文献
143.
STUDY ON THE STABILITY OF T’PHASE IN THE Al-Zn-Cu TERNARY SYSTEM 总被引:1,自引:0,他引:1
The phase constitutes and phase compositions in the eight alloys designed with dif-ferent compositions of Al--Zn--Cu system have been determined after the homogenoustreatment and then equilibrium cooling to 20℃ by use of optical microscope, electronprobe microanalysis and X--ray diffraction. It has been found that there existed the T'phase in the seven alloys. Consequently, it was testified that the T' phase was stableat room temperature. At the same time, the phase relationship was not locally rightfor the isothermal section of 20℃ of Al--Zn--Cu system of the ASM published in 1997. 相似文献
144.
采用溶胶-凝胶法制备了TiO2、Mn4+/TiO2、Ce4+/TiO2和Mn4+-Ce4+/TiO2光催化剂。通过考察掺杂离子的种类和用量对所得催化剂用于紫外光催化降解甲基橙性能的影响,表明Ce4+/TiO2中Ce4+的适宜掺杂量为1.0%,Ce4+-Mn4+/TiO2中,当Mn4+的掺杂量为25.0%时,Ce4+的适宜掺杂量为0.50%,相应的脱色效率为92.39%和99.41%。当掺杂量适当时,四种催化剂用于紫外光催化降解甲基橙的活性次序为:Mn4+-Ce4+/TiO2 > TiO2>Ce4+/TiO2> Mn4+/TiO2。XRD分析结果表明,所得光催化剂均为锐钛矿型纳米粒子。 相似文献
145.
In situ synchrotron X-ray studies on copper-nickel 5 V Mn oxide spinel cathodes for Li-ion batteries
Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both metals in the spinel lattice structure reduces the 3.9-4.2 V potential plateaus associated with the conversion of Mn3+ to Mn4+. Higher potential plateau associated with oxidation of the substituted transition elements is also observed. These substituents also significantly alter the onset of Jahn-Teller distortions in the 3 V potential plateau. Synchrotron based in situ X-ray absorption (XAS) was used to determine the exact nature of the oxidation state changes in order to explain the overall observed capacities at different potential plateaus. The studies on LiCu0.5Mn1.5O4 show single phase behavior in the 4-5 V potential region with a good cycle life. Lower cycle life characteristic observed in cycling LiNi0.5Mn1.5O4 and LiNi0.25Cu0.25Mn1.5O4 versus Li metal are ascribed to coexistence of several phases in this potential region. However, LiCu0.5Mn1.5O4 shows onset of Jahn-Teller distortions in the 3 V potential plateau, in contrast to LiNi0.5Mn1.5O4 and LiNi0.25Cu0.25Mn1.5O4 cathode materials. 相似文献
146.
《Automatica》2014,50(12):3197-3203
In this paper we propose an approach to the implementation of controllers with decentralized strategies triggering controller updates. We consider set-ups with a central node in charge of the computation of the control commands, and a set of not co-located sensors providing measurements to the controller node. The solution we propose does not require measurements from the sensors to be synchronized in time. The sensors in our proposal provide measurements in an aperiodic way triggered by local conditions. Furthermore, in the proposed implementation (most of) the communication between nodes requires only the exchange of one bit of information (per controller update), which could aid in reducing transmission delays and as a secondary effect result in fewer transmissions being triggered. 相似文献
147.
针对目前冷轧薄板厂生产流程复杂、大量的多品种小批量合同并线生产,导致难以制定生产计划的问题,本文提出了混合模型子空间聚类(Subspace clustering mixed model,SCMM)方法,以合同中待加工钢卷的宽度、冷轧机组的入口厚度、 出口厚度以及合同的交货期为约束,对待生产合同进行组批. 依据冷轧厂实际生产过程,将冷轧机组视为核心节点,考虑准时交货、 在制品库存和生产流向产能分配的要求,对组批后的生产合同建立全流程合同计划模型,并且利用提出的时间段蚁群算法(Time-section ant colony optimization,TSA),制定合同计划.利用生产过程的实际数据测试,本文的方法优于人工排产,可以满足制定冷轧薄板全流程生产计划的要求. 相似文献
148.
The behavioral and physiological effects of plant allelochemicals have been difficult to demonstrate; it is not often clear whether the compounds are deterrent, toxic, or both. In this study, we compared the qualitative and quantitative effects of several iridoid glycosides on a generalist lepidopteran herbivore,Spodoptera eridania (Noctuidae). Larval growth and survivorship and larval preference or avoidance were measured on artificial diets containing different iridoid glycosides at different concentrations. We also tested the toxicity/deterrence of these compounds. We found that iridoid glycosides retarded larval growth significantly at relatively low concentrations and that they were usually avoided in preference tests. The toxicity/ deterrence test did not always reflect the results of these other tests. The merits of using a variety of methods for determining deterrence and/or toxicity of plant allelochemicals are discussed. 相似文献
149.
采用一种含有氢氟酸的酸性溶液作为活化溶液,对钛合金表面进行化学镀镍。讨论了活化液、络合剂、Ni2 及H2PO2-浓度、缓冲剂及温度的确定。分别介绍了除膜、活化、预镀镍及化学镀镍工艺规范。对该镀镍层的耐蚀性及含磷量进行了测定,并对该镀层热处理前后的硬度、厚度、结合力、氢含量、耐磨损性及表面微观形貌进行了测试与比较。结果表明,采用本工艺可在钛合金表面沉积出70μm左右的镍磷合金镀层,磷含量在8%~11%(质量分数);氢含量可控制在50mg/kg;经200℃热处理1h后镀层硬度达到600HV,镀层与基体结合力好;经350℃热处理1h后镀层硬度达850HV,耐磨损性良好。该镀层可满足航空钛合金部件的要求。 相似文献
150.
Changxin Liu Jinliang Ding Anthony J. Toprac Tianyou Chai 《Knowledge and Information Systems》2014,41(2):401-421
A data-based adaptive online prediction model is proposed for plant-wide production indices based on support vector regression, a general method which we customized specifically to model very large data sets that are generated dynamically and periodically. The proposed model can update its parameters online according to the statistical properties of the training samples. Further, in order to improve the prediction precision, each sample is weighted with a dynamic penalty factor that considers the effect of each sample on the prediction model accuracy. Moreover, a customized procedure is introduced to handle large training sets. After having been convincingly evaluated on benchmark data, effectiveness and performance of our approach for plant-wide production indices is demonstrated using industrial data from an operating ore dressing plant over a range of scale in training data set size. The higher accuracy and shorter computation times than existing methods suggest that it may prove advantageous in actual application to dynamic production processes. 相似文献