全文获取类型
收费全文 | 34023篇 |
免费 | 3723篇 |
国内免费 | 1811篇 |
专业分类
电工技术 | 6137篇 |
综合类 | 3422篇 |
化学工业 | 2638篇 |
金属工艺 | 649篇 |
机械仪表 | 1690篇 |
建筑科学 | 4435篇 |
矿业工程 | 782篇 |
能源动力 | 1994篇 |
轻工业 | 5065篇 |
水利工程 | 1205篇 |
石油天然气 | 1165篇 |
武器工业 | 309篇 |
无线电 | 1894篇 |
一般工业技术 | 3336篇 |
冶金工业 | 1618篇 |
原子能技术 | 490篇 |
自动化技术 | 2728篇 |
出版年
2024年 | 145篇 |
2023年 | 623篇 |
2022年 | 1179篇 |
2021年 | 1568篇 |
2020年 | 1502篇 |
2019年 | 1292篇 |
2018年 | 1135篇 |
2017年 | 1315篇 |
2016年 | 1407篇 |
2015年 | 1451篇 |
2014年 | 2027篇 |
2013年 | 1982篇 |
2012年 | 2651篇 |
2011年 | 2744篇 |
2010年 | 1879篇 |
2009年 | 1973篇 |
2008年 | 1840篇 |
2007年 | 2193篇 |
2006年 | 1886篇 |
2005年 | 1567篇 |
2004年 | 1270篇 |
2003年 | 1137篇 |
2002年 | 824篇 |
2001年 | 714篇 |
2000年 | 577篇 |
1999年 | 456篇 |
1998年 | 349篇 |
1997年 | 270篇 |
1996年 | 228篇 |
1995年 | 222篇 |
1994年 | 176篇 |
1993年 | 142篇 |
1992年 | 129篇 |
1991年 | 90篇 |
1990年 | 90篇 |
1989年 | 63篇 |
1988年 | 51篇 |
1987年 | 44篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 30篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1961年 | 13篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 148 毫秒
81.
The analytical solutions of a spinning Rayleigh beam with rotatory moment inertia and gyroscopic effect are presented in this paper. The critical speeds can be written analytically in a function of the length-to-radius ratio (l) defined by the beam's length over its outer radius and the hollowness ratio (α) defined by the hollow area over the total area of the cross section. The sensitivity analyses show that the critical speed is decreasing with l, but increasing with α. Moreover, α is more sensitive to the critical speeds. The design of a spinning beam should therefore be emphasized more on the hollowness factor. Contrary to common belief, only finite critical speeds exist and the number is independent of the boundary conditions. It increases monotonically with l, but decreases with α. The steady state unbalanced response can therefore be expressed analytically by the finite precessional modes and the corresponding generalized coordinates. 相似文献
82.
A review of robust design methods for multiple responses 总被引:1,自引:0,他引:1
Terrence E. Murphy Kwok-Leung Tsui Janet K. Allen 《Research in Engineering Design》2005,16(3):118-132
Problems in engineering design often involve determining design variable settings to optimize individual product performance
for multiple criteria, which are often in conflict. We review mathematically rigorous techniques from the statistical literature
for finding a vector x of design variable settings, which produces an optimal compromise solution among a group of prioritized response variables.
The best compromise solution is typically gained by optimizing an objective function, which incorporates the prioritized demands
of multiple responses. Since most multi-response objective functions are constructed by combining the functions used to optimize
univariate responses, a review of the prominent univariate approaches is presented first. A multivariate approach from the
engineering literature called the compromise Decision Support Problem is also reviewed. Finally a table comparing the relative
merits of the different multivariate approaches summarizes the article in a concise and user-friendly fashion. 相似文献
83.
84.
对φ30的矿用扁平接链环进行静态拉伸电测实验,分析并得出产生最大强度的位置。同时应用ANSYS有限元分析软件对接链环的力学简化模型进行分析,与实验结果相比较,有助于找出齿部破坏规律,对齿形的改进及今后的疲劳分析具有重要意义。 相似文献
85.
Here, we report on the application of corroles as analytically active compounds in liquid membrane electrodes (ISE) that are sensitive towards salicylic acid and salicylate.The potentiometric signals generated by corrole-incorporated ISEs strongly depend on the pH of the aqueous sample solution and the membrane composition, such as the presence of lipophilic sites. Corrole incorporating ISEs are characterised by a low detection limit (4.0 × 10−5 M) and a wide linear range (4.0 × 10−5 to 5.3 × 10−3 M). Also, they are free from interference versus other organic anions.The mechanism of the generation of the potentiometric signals of corrole incorporating ISEs in the presence of salicylate anion, as well salicylic acid, will be discussed. 相似文献
86.
准噶尔盆地腹部普遍发育深层(大于4000m)超压系统,很多钻井都钻遇超压。通过对超压段钻井、地质、测井、地震特征系统研究发现,超压段泥浆密度大幅增加,具有高声波时差、低电阻率以及地震低速的超压响应特征。利用Dix公式计算地震层速度和利用Fillippone公式计算地层压力,得到超压数据体。准噶尔盆地腹部超压在白垩系及其以下沉积地层中均有分布,超压层的深度范围不同。分1井西凹陷边缘以及昌吉凹陷西南有空层现象。超压顶面分布的层位由北往南、从东到西逐渐变浅,从三叠系顶部到白垩系底部。深部超压对油气分布和富集有着重要的控制作用,准噶尔盆地腹部超压层分布的研究将对本区油气勘探起积极的推动作用。 相似文献
87.
88.
2001年浙江省率先利用市场机制配置水资源,经过近6年的实践,已经积累了一些数据,取得了较好的成效。为此,利用浙江省三个县(市)水资源开发权市场拍卖价格,来研究水资源开发权转让价格与相关要素之间的相关性和进行线性回归分析。通过分析,验证了水权出让价格与各有关因素之间的关系,同时指明了水资源市场化配置的良好态势。 相似文献
89.
对冬季采用天然气热水锅炉供热,夏季采用电动离心式冷水机组供冷和冬夏季都采用天然气直燃型溴化锂吸收式冷热水机组进行供热供冷的两种方案进行了技术经济比较。指出天然气价和电价是影响供热供冷成本的最敏感因素。 相似文献
90.
Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献