全文获取类型
收费全文 | 85158篇 |
免费 | 10301篇 |
国内免费 | 5927篇 |
专业分类
电工技术 | 7350篇 |
技术理论 | 5篇 |
综合类 | 7355篇 |
化学工业 | 11549篇 |
金属工艺 | 5248篇 |
机械仪表 | 5735篇 |
建筑科学 | 7139篇 |
矿业工程 | 3306篇 |
能源动力 | 2511篇 |
轻工业 | 6864篇 |
水利工程 | 2315篇 |
石油天然气 | 3938篇 |
武器工业 | 1103篇 |
无线电 | 10850篇 |
一般工业技术 | 8321篇 |
冶金工业 | 3171篇 |
原子能技术 | 1193篇 |
自动化技术 | 13433篇 |
出版年
2024年 | 575篇 |
2023年 | 1683篇 |
2022年 | 3502篇 |
2021年 | 4789篇 |
2020年 | 3586篇 |
2019年 | 2617篇 |
2018年 | 2874篇 |
2017年 | 3308篇 |
2016年 | 2874篇 |
2015年 | 4439篇 |
2014年 | 5442篇 |
2013年 | 6204篇 |
2012年 | 7529篇 |
2011年 | 7685篇 |
2010年 | 6892篇 |
2009年 | 6400篇 |
2008年 | 6168篇 |
2007年 | 5577篇 |
2006年 | 4729篇 |
2005年 | 3707篇 |
2004年 | 2460篇 |
2003年 | 1644篇 |
2002年 | 1430篇 |
2001年 | 1189篇 |
2000年 | 965篇 |
1999年 | 744篇 |
1998年 | 444篇 |
1997年 | 382篇 |
1996年 | 341篇 |
1995年 | 276篇 |
1994年 | 221篇 |
1993年 | 155篇 |
1992年 | 106篇 |
1991年 | 103篇 |
1990年 | 66篇 |
1989年 | 50篇 |
1988年 | 50篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1979年 | 18篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 17篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
移动服务机器人在提高老人/残疾人活动空间方面具有重要作用.针对机器人自主避障失败时存在安全问题,提出了基于共享控制的服务机器人系统.构建基于机器视觉与人眼视觉共享控制的机器人系统.研究服务机器人的共享策略问题和眼电信号角度与参考轨迹关系.引入人工场解决自适应轨迹跟踪算法的平滑性.仿真结果说明基于人工场导向方法能平滑逼近期望轨迹.实验结果表明本系统能够满足使用者的安全需求. 相似文献
992.
To study the dynamic mechanical behavior of C60 concrete at high temperatures, impact tests under different steady-state temperature fields (100, 200, 300, 400 and 500.℃) were conducted under a variety of durations at the corresponding constant high temperature, namely 0, 30, 60, 90 and 120.min, employing split Hopkinson pressure bar (SHPB) system. In addition, the impact tests were also conducted on the specimens cooled from the high temperature to the room temperature and the specimen under room temperature. From the analysis, it is found that C60 concrete has a time-dependent behavior under high-temperature environment. Under 100, 200, 300, 400 and 500.℃ steady-state temperature fields respectively, as the duration at the corresponding constant high temperature increases, the dynamic compressive strength and the elastic modulus decrease but the peak strain generally ascends. After cooling to the room temperature, the dynamic compressive strength and the elastic modulus descend as well, but the peak strain increases first and then decreases slightly, when the duration increases. For specimens under and cooled from the high-temperature, as the temperature increases, the dynamic compressive strength and the peak strain raise first and then reduce gradually,and the dynamic compressive strength of specimen under high temperature is higher than that of the specimen cooled from the same high temperature. 相似文献
993.
To analyze main factors affecting the separation reliability between a missile and adapters for the launching process, a six DOF underwater dynamic model for the missile and adapters is utilized to simulate the separation process, considering elastic forces of separating springs, hydrodynamic forces, gravity and buoyancy. Moreover, a criterion based on the maximum separating distance is put forward to determine whether adapters separate with the missile reliably. The results show that the magnitude and position of elastic force, the wedge angle and mass of the adapter significantly affect the separating process. The local sensitivity analysis for the reference status of design parameters demonstrates that the wedge angle of adapters has the maximum influence about 70.4% on the separating distance. 相似文献
994.
To make full use of the gas resource, stabilize the pipe network pressure, and obtain higher economic benefits in the iron and steel industry, the surplus gas prediction and scheduling models were proposed. Before applying the forecasting techniques, a support vector classifier was first used to classify the data, and then the filtering was used to create separate trend and volatility sequences. After forecasting, the Markov chain transition probability matrix was introduced to adjust the residual. Simulation results using surplus gas data from an iron and steel enterprise demonstrate that the constructed SVC-HP-ENN-LSSVM-MC prediction model prediction is accurate, and that the classification accuracy is high under different conditions. Based on this, the scheduling model was constructed for surplus gas operating, and it has been used to investigate the comprehensive measures for managing the operational probabilistic risk and optimize the economic benefit at various working conditions and implementations. It has extended the concepts of traditional surplus gas dispatching systems, and provides a method for enterprises to determine optimal schedules. 相似文献
995.
AISI 304 stainless steel plates were welded with activated flux tungsten inert gas(A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG(conventional TIG) welding. 相似文献
996.
The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in-vestigated by optical microscopy (OM) and scanning electron microscopy (SE... 相似文献
997.
通过原子力显微镜(AFM)以及自制的PVDF胶体探针测量膜与不同有机物,即牛血清蛋白(BSA)、腐殖酸(HA)以及海藻酸钠(SA)之间的粘附力,从而研究不同PVA含量对PVDF/PVA改性膜抗污染性的影响.研究发现,随着PVA含量的增加,BSA以及HA污染膜的初期通量衰减幅度都呈先减小后增大趋势,而相应的通量恢复幅度都呈先增大后减小趋势.由于PVA的水合作用,改性膜-污染物之间的粘附力随着PVA含量的增加都呈减小趋势,因而其粘附力变化与相应污染膜的初期通量衰减幅度以及通量恢复率之间并不呈正相关性;而随着PVA含量的增加,SA污染膜的通量衰减幅度与通量恢复率都呈增大趋势,而改性膜-SA之间的粘附力呈减小趋势,与SA污染膜的通量衰减幅度以及通量恢复率之间呈良好的相关性. 相似文献
998.
针对智能电网环境下电网调度决策过程中的信息风险元不确定性,采用风险元传递理论,挖掘影响调度决策的核心信息风险元,借用梯形模糊数度量其不确定性,构建层次型智能电网调度决策信息风险元传递路径,进而利用TFN-AHP模型分析其风险元传递机理及对电网调度决策行为的影响程度。研究结果表明:电网调度员生理状态信息风险元、电网调度员心理状态信息风险元、调度日天气状态信息风险元以及主动负荷信息风险元对智能电网调度决策具有影响程度较大,其他信息风险元不确定性风险元对智能电网调度影响相对较弱。 相似文献
999.
采用2011年1月-2014年6月在云南省第一人民医院确诊并行手术治疗的58例胰腺癌患者,切除部分肿瘤组织作为实验标本,癌旁组织作为对照,利用免疫组化及Western blot检测晚期胰腺癌组织内神经生长因子(nerve growth factor,NGF)及神经生长因子前体(precursor of nerve growth factor,pro NGF)的表达,Gel-Pro analyzer 4图像分析系统分析Western条带密度.试验重复3次,取3次IOD值行统计学分析.免疫组化及Western blot结果显示肿瘤组织NGF的表达较癌旁组织明显增高,而pro NGF的表达较癌旁组织明显降低.半定量Western blot显示癌旁组织和肿瘤组织NGF表达的IOD值分别为113.33±8.54和285.00±15.13,pro NGF表达的IOD值分别为245.00±7.55和86.33±7.37,差异有统计学意义(P0.05).因此,晚期胰腺癌患者肿瘤组织内NGF/pro NGF的比例发生改变,组织内NGF蓄积,而pro NGF减少,这可能是导致胰腺癌肿瘤细胞凋亡减少,生长、浸润和迁徙功能增强的重要机制之一. 相似文献
1000.
某高层建筑基础防水施工中采用了混凝土结构自防水、SBS防水卷材、水泥基渗透结晶型防水涂料、腻子型膨胀橡胶条、止水钢板等多种防水材料,同时对施工过程进行严格的质量控制,取得较好的防水效果。 相似文献