全文获取类型
收费全文 | 314569篇 |
免费 | 28218篇 |
国内免费 | 19033篇 |
专业分类
电工技术 | 41656篇 |
技术理论 | 12篇 |
综合类 | 30484篇 |
化学工业 | 24009篇 |
金属工艺 | 15411篇 |
机械仪表 | 29546篇 |
建筑科学 | 36278篇 |
矿业工程 | 12030篇 |
能源动力 | 8815篇 |
轻工业 | 10221篇 |
水利工程 | 8916篇 |
石油天然气 | 10796篇 |
武器工业 | 4252篇 |
无线电 | 26049篇 |
一般工业技术 | 25155篇 |
冶金工业 | 12126篇 |
原子能技术 | 2088篇 |
自动化技术 | 63976篇 |
出版年
2024年 | 1052篇 |
2023年 | 3708篇 |
2022年 | 6636篇 |
2021年 | 7910篇 |
2020年 | 8786篇 |
2019年 | 6904篇 |
2018年 | 6470篇 |
2017年 | 9062篇 |
2016年 | 10047篇 |
2015年 | 11048篇 |
2014年 | 20161篇 |
2013年 | 17212篇 |
2012年 | 22542篇 |
2011年 | 24622篇 |
2010年 | 18614篇 |
2009年 | 19361篇 |
2008年 | 18621篇 |
2007年 | 22971篇 |
2006年 | 20689篇 |
2005年 | 17951篇 |
2004年 | 14777篇 |
2003年 | 13184篇 |
2002年 | 10718篇 |
2001年 | 8968篇 |
2000年 | 7805篇 |
1999年 | 6324篇 |
1998年 | 4818篇 |
1997年 | 4172篇 |
1996年 | 3335篇 |
1995年 | 2737篇 |
1994年 | 2394篇 |
1993年 | 1668篇 |
1992年 | 1414篇 |
1991年 | 1080篇 |
1990年 | 845篇 |
1989年 | 712篇 |
1988年 | 508篇 |
1987年 | 288篇 |
1986年 | 205篇 |
1985年 | 204篇 |
1984年 | 228篇 |
1983年 | 186篇 |
1982年 | 192篇 |
1981年 | 111篇 |
1980年 | 126篇 |
1979年 | 88篇 |
1978年 | 66篇 |
1977年 | 58篇 |
1975年 | 21篇 |
1959年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Various methods have been developed to monitor the health and strain state of carbon fiber reinforced polymers, each with a unique set of pros and cons. This research assesses the use of piezoresistive sensors for in situ strain measurement of carbon fiber and other composite structures in multidirectional laminates. The piezoresistive sensor material and the embedded circuitry are both evaluated. For the piezoresistive sensor, a conductive nickel nanocomposite sensor is compared with the piezoresistivity of the carbon fiber itself. For the circuit, the use of carbon fibers already present in the structure is compared with the use of nickel coated carbon fiber. Successful localized strain sensing is demonstrated for several sensor and circuitry configurations. Numerous engineering applications are possible in the ever-growing field of carbon-composites. 相似文献
52.
This short communication presents a generic mathematical programming formulation for computer-aided molecular design (CAMD). A given CAMD problem, based on target properties, is formulated as a mixed integer linear/non-linear program (MILP/MINLP). The mathematical programming model presented here, which is formulated as an MILP/MINLP problem, considers first-order and second-order molecular groups for molecular structure representation and property estimation. It is shown that various CAMD problems can be formulated and solved through this model. 相似文献
53.
Energy bands, effective mass of carriers, absolute band edge positions and optical properties of tetragonal AgInS2 were calculated using a first-principles approach with the exchange correlation described by B3LYP hybrid functional. The results indicate that tetragonal AgInS2 has a direct band gap of 1.93 eV, which reproduce well experimental value. Calculated effective masses of electrons and holes are both small which are beneficial to separation and migration of electron and hole pairs. This implies that AgInS2 has good photocatalytic performance. The calculated optical characteristics indicate that AgInS2 has a slight anisotropy for both the real and imaginary parts of the dielectric function and exhibits large optical absorption in the visible light region. Furthermore, the calculated band edge positions in (100), (010) and (001) surfaces indicate that tetragonal AgInS2 is beneficial to the reduction and oxidation of water to hydrogen and oxygen under visible light irradiation. 相似文献
54.
55.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献
56.
This paper analyzes the problems existing in the teaching of data structure course, and puts forward the reform from the as-
pects of strengthening basic programming, visualized explanation of abstract theory, combination of C++, Java programming, ratio-
nal use of online platform, and stratification of exercises, aiming at improving students' practical ability, learning interest and self-
confidence. 相似文献
57.
ABSTRACTThis paper deals with asymptotic stabilisation of a class of nonlinear input-delayed systems via dynamic output feedback in the presence of disturbances. The proposed strategy has the structure of an observer-based control law, in which the observer estimates and predicts both the plant state and the external disturbance. A nominal delay value is assumed to be known and stability conditions in terms of linear matrix inequalities are derived for fast-varying delay uncertainties. Asymptotic stability is achieved if the disturbance or the time delay is constant. The controller design problem is also addressed and a numerical example with an unstable system is provided to illustrate the usefulness of the proposed strategy. 相似文献
58.
某出口型号交流电力机车牵引控制系统要求变流器控制逻辑具备接触器控制、牵引系统数据交互、变流器故障保护、变流器启动自检等功能。针对以上功能,基于MATLAB中的Simulink/Stateflow可视化编程工具进行牵引控制模型的搭建,遵循模块化编程理念,采用较少的程序代码编写实现复杂的逻辑控制模型,生成逻辑清晰的控制功能流程图,进行半实物仿真测试,增强控制模型的可靠性。通过该变流器产品型式试验检验,验证变流器控制逻辑的功能可以满足控制系统的需求。 相似文献
59.
结合结构支撑理论,探究节点网络结构支持力的一些性质,提出了社交网络结构中的全网支持力和被支持力的总量一致性,并进一步提出计算节点支持力的方法。谣言作为特殊信息,在支持力不同节点之间的传播特性有所不同,借鉴随机游走模型中的PageRank计算方法,对不同节点支持力的谣言传播以及传播后的辟谣状况进行了仿真模拟,结果表明支持力不同的节点对于谣言传播和辟谣影响明显。 相似文献
60.
Thermoresponsive behavior and rheology of SiO2–hyaluronic acid/poly(N‐isopropylacrylamide) (NaHA/PNIPAm) core–shell structured microparticles
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)