全文获取类型
收费全文 | 25811篇 |
免费 | 2763篇 |
国内免费 | 1496篇 |
专业分类
电工技术 | 1680篇 |
技术理论 | 2篇 |
综合类 | 2175篇 |
化学工业 | 4325篇 |
金属工艺 | 1560篇 |
机械仪表 | 1526篇 |
建筑科学 | 1897篇 |
矿业工程 | 727篇 |
能源动力 | 600篇 |
轻工业 | 3161篇 |
水利工程 | 517篇 |
石油天然气 | 1109篇 |
武器工业 | 260篇 |
无线电 | 2564篇 |
一般工业技术 | 2911篇 |
冶金工业 | 1090篇 |
原子能技术 | 349篇 |
自动化技术 | 3617篇 |
出版年
2024年 | 163篇 |
2023年 | 516篇 |
2022年 | 1030篇 |
2021年 | 1243篇 |
2020年 | 965篇 |
2019年 | 801篇 |
2018年 | 843篇 |
2017年 | 957篇 |
2016年 | 893篇 |
2015年 | 1210篇 |
2014年 | 1596篇 |
2013年 | 1795篇 |
2012年 | 1839篇 |
2011年 | 1905篇 |
2010年 | 1798篇 |
2009年 | 1684篇 |
2008年 | 1616篇 |
2007年 | 1498篇 |
2006年 | 1349篇 |
2005年 | 1090篇 |
2004年 | 862篇 |
2003年 | 699篇 |
2002年 | 771篇 |
2001年 | 638篇 |
2000年 | 507篇 |
1999年 | 392篇 |
1998年 | 238篇 |
1997年 | 200篇 |
1996年 | 202篇 |
1995年 | 162篇 |
1994年 | 132篇 |
1993年 | 86篇 |
1992年 | 84篇 |
1991年 | 57篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 31篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 21篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
该文研究了T300碳纤维单向增强的环氧复合材料,在应变率从10~(-3)/s到10~3/s范围内的冲击拉伸行为.通过对实验数据进行拟合,得出该范围内材料对应变率具有弱的敏感性,表现在破坏强度及破坏应变随应变率增加不显著变化,平均模量几乎不受应变率的影响.分析了试件的几何尺寸效应,讨论了应力波作用对破坏形态的影响以及实验中观察到的拔出现象.从应变率在10~2~10~3/s附近材料行为某些非确定性,指出在更宽范围内了解其性能的必要性. 相似文献
52.
The host cell interactions of the genome types Ad11p and Ad11a of human adenovirus serotype 11, displaying kidney or respiratory tropism, were compared using FACS analysis. Kinetic experiments indicated that the virus binding stated immediately and reached a plateau after 30 min. The binding of biotinylated virions to seven continuous cell lines. A549, A498, J82, HeLa, CHO, MDCK, and human diploid fibroblasts (HEDF), was quantitated by FACS analysis. The binding capacities of the two viruses to all human cell lines but A549 cells appeared to differ. Ad11p virions manifested high affinities, whereas Ad11a virions presented low affinities. Neither of the two viruses bound to CHO or MDCK cells. Reciprocal competition experiments showed that the Ad11a virions could be weakly blocked by the Ad11p virions, whereas the Ad11p virions could not be competed at all by the Ad11a virions. The binding of the Ad11p virions to cells could be blocked by the rfiber antiserum of Ad11p, but not by the corresponding antiserum against Ad11a or Ad35p. A comparison of the cytopathogenicity of the seven cell lines infected by Ad11p and Ad11a demonstrated that the efficiency of the initial event of an adenovirus infection directly affects the outcome of the viral infection. The Ad11a in the A498, J82, HeLa, or HEDF cells that presented lower affinity and receptor concentration showed 100 times less infectivity than that in A549 cells displaying high affinity and receptor concentration. These results indicate that the cell susceptibility to Ad11p and Ad11a infection strongly depends on both the number of fiber receptors on the host cells and the receptor affinity for ligands on the fiber knob. Our findings also suggest that the receptors for Ad11p and Ad11a on the surface of different cell types may be different or on different sites. 相似文献
53.
新型高性能脉冲峰值保持电路 总被引:10,自引:7,他引:3
本文介绍了两种新型跨导型脉冲峰值保持器,分别用于多丝正比室(MWPC)和复合晶体闪烁探测器(Phoswich)输出脉冲信号的形状和幅度分析。电路的跨导放大级采用跨导型集成运算放大器,使电路结构简单化,且性能优良可靠,能响应输入脉冲最小上升时间分别为50ns(Phoswich)和500ns(MWPC)的信号,在40dB的动态范围内,两电路的积分非线性均好于0.1%,特别适用于空间γ射线观测。 相似文献
54.
Qi Zhao Xuanzhe Liu Xingrun Chen Jiyu Huang Gang Huang Hong Mei 《Service Oriented Computing and Applications》2012,6(2):99-116
Facilitated by the SOA and new Web technologies, Service-Oriented Rich Clients (SORCs) compose various Web-delivered services in Web browser to create new applications. The SORCs support client-side data storage and manipulation and provide more features than traditional thin clients. However, the SORCs might suffer from data access issues, mainly due to both client-side incompatible data sources and server-side improper or even undesirable cache strategies. Addressing the data access issues, this paper proposes a data access framework for SORCs. The main contributions of this paper are as follows. First, the framework makes the SORCs accommodate heterogeneous local storage solutions and diverse Web browsers properly. The framework abstracts the underlying details of different local storages and selects the most proper data sources for current SORC in use. Secondly, the framework provides a cache mechanism, which supports client-side customized cache strategies. An adaptive technique for the strategies is also proposed to adjust cache strategies based on users?? historical actions to achieve better performance. 相似文献
55.
为明晰洪水峰量联合设计的特点,以岗南水库洪水为例,基于Gumbel Copula函数,分析了AND、OR、Kendall、生存Kendall 4种重现期的优缺点,采用极大似然法、同频率法、条件最可能组合法3种方法计算了联合设计值。结果表明: ①AND和OR重现期在危险域和安全域的识别上存在局限性;相对而言,Kendall重现期更合理,但其安全域是无界的,这与实际不符;生存Kendall重现期则界定了有界的安全域,使得重现期的概念在逻辑上更科学合理。② 3种设计值计算方法的差别不大,但从简单实用角度出发,推荐采用同频率法计算设计值。③不同重现期标准的设计值差别比较明显,基于OR重现期计算的设计值总是最大的,生存Kendall、Kendall重现期设计值次之,AND重现期设计值最小。④推荐采用生存Kendall重现期进行两变量洪水设计,因其有比较严谨的理论基础,且设计结果兼顾了安全性与经济性。⑤两变量联合设计值与单变量设计值的差异受变量间相关性的影响较大,且变量相关性越弱,差异越大。研究显示,基于生存Kendall重现期、采用同频率法计算设计值是目前较为科学合理的洪水峰量联合设计途径。 相似文献
56.
液压支架工作状态模糊识别系统研究 总被引:1,自引:1,他引:0
针对目前综采工作面液压支架压力监测系统只能监测综采工作面压力,不能对液压支架工作状态进行识别的问题,设计了一种液压支架工作状态模糊识别系统。该系统可对现有的综采工作面液压支架压力监测系统监测到的压力数据进行模糊识别,根据模糊识别输出值即可判断液压支架的5种工作状态,即降架、移架、升架、增阻、卸压保持;当液压支架处于增阻工作状态且增阻时间过长时,该系统可及时通知液压支架操作工增大液压支架压力,辅助实现顶煤破碎。测试结果验证了该系统的可行性。 相似文献
57.
在测控系统中,经常需要对各种现场信号进行采集;该模块主要实现对开关量状态信号进行实时监控,记录状态信息,为故障诊断提供依据;在设计中,采用了光耦隔离器件对输入信号进行了隔离和抗干扰处理,使用了FPGA实现了数据实时采集和中断处理,最后经PCI总线与主机进行数据交互;在故障诊断系统中,该信号采集板工作稳定、可靠,能够满足系统的实时性要求。 相似文献
58.
多媒体技术是以数字技术为基础的综合技术。本文结合文科学生的特点,探讨了《多媒体技术与应用》课程设置与教学。 相似文献
59.
视频监控的在屏交互过程中,需要快速地对交互控件、感兴趣区域、活动标记等图形和图像进行绘制,为避免画面的停滞感,要求图形设备接口能快速进行绘制.为此,提出了一种笔画模型方法.利用 DirectX的原始绘制能力,该方法将绘制任务转换成笔画对象,使视频系统在实时运行过程中,只需将已转换的笔画对象的绘制数据提交给 DirectX 进行渲染和显示即可,降低重复绘制时间,满足系统的快速绘制要求.基于笔画模型方法,开发了一种可快速绘制的图形设备接口. 相似文献
60.
Marie Burns Lennard Ostendorf Robert Biesen Andreas Grützkau Falk Hiepe Henrik E. Mei Tobias Alexander 《International journal of molecular sciences》2021,22(5)
Given its uniformly high expression on plasma cells, CD38 has been considered as a therapeutic target in patients with systemic lupus erythematosus (SLE). Herein, we investigate the distribution of CD38 expression by peripheral blood leukocyte lineages to evaluate the potential therapeutic effect of CD38-targeting antibodies on these immune cell subsets and to delineate the use of CD38 as a biomarker in SLE. We analyzed the expression of CD38 on peripheral blood leukocyte subsets by flow and mass cytometry in two different cohorts, comprising a total of 56 SLE patients. The CD38 expression levels were subsequently correlated across immune cell lineages and subsets, and with clinical and serologic disease parameters of SLE. Compared to healthy controls (HC), CD38 expression levels in SLE were significantly increased on circulating plasmacytoid dendritic cells, CD14++CD16+ monocytes, CD56+ CD16dim natural killer cells, marginal zone-like IgD+CD27+ B cells, and on CD4+ and CD8+ memory T cells. Correlation analyses revealed coordinated CD38 expression between individual innate and memory T cell subsets in SLE but not HC. However, CD38 expression levels were heterogeneous across patients, and no correlation was found between CD38 expression on immune cell subsets and the disease activity index SLEDAI-2K or established serologic and immunological markers of disease activity. In conclusion, we identified widespread changes in CD38 expression on SLE immune cells that highly correlated over different leukocyte subsets within individual patients, but was heterogenous within the population of SLE patients, regardless of disease severity or clinical manifestations. As anti-CD38 treatment is being investigated in SLE, our results may have important implications for the personalized targeting of pathogenic leukocytes by anti-CD38 monoclonal antibodies. 相似文献