首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   399535篇
  免费   40472篇
  国内免费   26244篇
电工技术   36859篇
技术理论   57篇
综合类   53656篇
化学工业   38652篇
金属工艺   14141篇
机械仪表   24877篇
建筑科学   50901篇
矿业工程   19042篇
能源动力   14481篇
轻工业   18096篇
水利工程   21691篇
石油天然气   18158篇
武器工业   4572篇
无线电   28277篇
一般工业技术   29206篇
冶金工业   19261篇
原子能技术   4291篇
自动化技术   70033篇
  2024年   714篇
  2023年   4297篇
  2022年   8304篇
  2021年   10307篇
  2020年   11056篇
  2019年   9319篇
  2018年   8775篇
  2017年   11012篇
  2016年   12948篇
  2015年   14246篇
  2014年   23344篇
  2013年   22216篇
  2012年   27957篇
  2011年   29970篇
  2010年   23628篇
  2009年   24537篇
  2008年   23509篇
  2007年   29303篇
  2006年   26931篇
  2005年   23420篇
  2004年   19577篇
  2003年   17467篇
  2002年   14196篇
  2001年   11930篇
  2000年   10048篇
  1999年   7975篇
  1998年   6174篇
  1997年   5293篇
  1996年   4958篇
  1995年   4309篇
  1994年   3710篇
  1993年   2761篇
  1992年   2382篇
  1991年   1778篇
  1990年   1530篇
  1989年   1327篇
  1988年   998篇
  1987年   686篇
  1986年   513篇
  1985年   453篇
  1984年   442篇
  1983年   289篇
  1982年   285篇
  1981年   201篇
  1980年   179篇
  1979年   157篇
  1978年   77篇
  1977年   78篇
  1975年   59篇
  1959年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
为研究渗流作用下新型装配重力式挡土墙应力变化及墙体排水通道对墙后土体固结的影响,采用ABAQUS进行有限元分析,有限元分析结果与模型试验结果相吻合,证明该模型的合理性。在此基础上研究渗流作用下墙体应力变化趋势及墙体排水通道对墙后土体固结效果的影响。研究结果表明:横向排水通道对墙后土体固结效果的影响优于纵向排水通道对土体固结效果的影响,墙体底部横向排水通道的影响作用最显著;渗流作用下墙体应力由上往下呈先增大后减小的趋势,墙体下部所受最大水平剪应力最大。  相似文献   
82.
83.
This paper describes the creation of an environmentally conscious community group, the Great River Network, and the role that it has played in the remediation and restoration process as part of one of the Great Lakes environmental programs. Community engagement was initiated in the region as part of the Remedial Action Plan for the Area of Concern at Cornwall/Akwesasne/Massena within the Upper St. Lawrence River. The community group formalised as a network representing 50+ organisations in response to perceived inadequacies in the agency of the community to respond to new environmental concerns outside of the scope of the existing programs. As a grass-roots initiative, the Great River Network has successfully completed remediation and restoration actions of significant value to the environment. These include a series of river clean ups (>42 tonnes of garbage removed), fish habitat restoration, and addressing shoreline erosion issues. Success has been achieved through partnering with a range of organisations, including Indigenous, non-profit, governmental, Conservation Authorities, businesses and industry partners. The action-oriented approach showcases how remediation and restoration led by, and embedded in, the community can result in true revitalization. A simplified framework for adaptive management practices for remediation and restoration efforts that lead to revitalization, including knowledge translation, is proposed. This case study highlights the transformational opportunities that remediation and restoration initiatives can bring. In this instance, the process is intensely local and cooperative and lays the foundation for moving towards a collective impact approach for the region.  相似文献   
84.
《Ceramics International》2022,48(16):23072-23080
The present study correlates the effect of R-cation radii on structural, vibrational, optical, and dielectric properties of rhombohedral rare earth aluminates RAlO3 (R = La, Pr, Nd). The polycrystalline samples of RAlO3 have been synthesized using sol-gel synthesis technique. Pure rhombohedral phase of RAlO3 samples has been confirmed with X-ray diffraction. Systematic decrements in the lattice parameter, bond length, and bond angle have been observed, giving rise to structural distortion due to decrease in ionic radii of R-cation. The phononic properties of RAlO3 have been investigated through Raman spectroscopy, where the degree of distortion of AlO6 octahedra can be analyzed with the peak position of Eg and A1g modes. An increase in the energy bandgap with decreasing R-cation radii shows an interconnection with the decrease in Al–O bond length. Interestingly, the decreasing dielectric constant with decreasing ionic radii of R-cation has been correlated with the difference in electronegativity of cation(R3+)-anion(O2?) pair. Also, a positive linear relationship between dielectric constant and energy bandgap has been investigated using Penn model.  相似文献   
85.
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。  相似文献   
86.
In this study, a novel multi-objective optimization method based on the best effect of unique input (independent variable) values on responses (dependent variables) was proposed. The proposed method was compared with optimization using Derringer & Suich function that is still the most used. The comparison was made using the response values measured in real experiments and available in the literature. The advantages of the proposed method such as not needing the polynomial model aiming to predict the response values, no parameter selection problem, being able to offer optimum range instead of single optimum value, being suitable for use with existing experimental designs and being simple and interpretable were demonstrated as a result of comparison. It was also suggested how the proposed method will be effective according to experimental designs, and application for the users' application was presented.  相似文献   
87.
陈佳  杨少鹏  余双波  贾悠 《通信技术》2020,(5):1277-1279
当前,骚扰电话乱象屡禁不止,严重影响了人民群众的正常生活,甚至威胁到个人财产安全,因此简单有效地识别骚扰电话技术成为亟待解决的问题。区别于现有的对电话号码进行黑白名单标记、大数据分析等识别方法,提出基于信任链的骚扰电话预判技术,从可信度量的角度计算来电号码的可靠程度,并针对高危受害群体的典型应用场景进行分析,通过对骚扰电话的预判,降低其受到电话骚扰甚至电话诈骗的可能性。  相似文献   
88.
In this study, the Ga–Te binary system was reassessed by means of the CALPHAD method using a modified lattice stability parameter for Te as well as experimental data for this binary system. The two-sublattice ionic solution model was applied for the liquid phase, and the intermediate phases were described by the sublattice model. A set of self-consistent thermodynamic parameters was optimized for all the phases in the Ga–Te binary system, which reproduced the phase diagram and the thermodynamic properties well. Using the reevaluated Ga–Te system, previously assessed Ga–Se system, and modified Se–Te system, a critical evaluation of the Ga–Se–Te ternary system was performed. The calculated vertical sections, isothermal sections, and liquidus projection agreed reasonably well with the experimental data. Immiscibility in the liquid phase was observed, and the origin of this behavior is discussed from a thermodynamic perspective.  相似文献   
89.
王鹏  李林  徐建军 《中州煤炭》2020,(9):123-127
在对沁水盆地赵庄矿煤层气开发地质、煤层气生产井资料深入研究的基础上,分析、总结了区内煤层气直井低产原因,并据此提出了区内地面抽采后续开发方向。研究认为:3号煤层气含量偏低、含气饱和度低、临储比低,致使排采阶段气含量可降幅度低,是其低产的宏观表征;3号煤储层不匹配孔级,较差连通性,即微、小孔为主,中孔次之,大孔不发育,微裂隙连通性差,致使扩散缓慢、影响储层改造和抽采效果,是其低产的微观表征;3号煤层远高于顶底板塑性及相近的水平应力,进一步造成改造缝长受限,泄流面积不足。因此,建议区内后续地面抽采方式应以增大泄流面积开发方式为主。  相似文献   
90.
赵璇 《中国调味品》2020,(2):112-115
对洋葱蛋白、4种不同水解度的粗洋葱多肽、4种分子量范围的纯化多肽组分的水解度、分子量、氨基酸组成、DPPH·清除能力进行了研究。结果表明,洋葱蛋白酶解后分子量大幅降低,必需氨基酸组分和支链氨基酸组分均有所提高,DPPH·清除能力大幅提高,且与水解度成正比;在4种水解度的粗洋葱多肽的纯化组分中,P-III(分子量为1~5kDa)的DPPH·清除能力均为最强,这归功于其合适的分子量分布。该研究为洋葱的高值化利用提供了理论依据。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号