全文获取类型
收费全文 | 10682篇 |
免费 | 1481篇 |
国内免费 | 1024篇 |
专业分类
电工技术 | 735篇 |
综合类 | 1319篇 |
化学工业 | 887篇 |
金属工艺 | 284篇 |
机械仪表 | 460篇 |
建筑科学 | 1381篇 |
矿业工程 | 348篇 |
能源动力 | 331篇 |
轻工业 | 1513篇 |
水利工程 | 878篇 |
石油天然气 | 582篇 |
武器工业 | 68篇 |
无线电 | 942篇 |
一般工业技术 | 655篇 |
冶金工业 | 223篇 |
原子能技术 | 106篇 |
自动化技术 | 2475篇 |
出版年
2024年 | 52篇 |
2023年 | 157篇 |
2022年 | 400篇 |
2021年 | 392篇 |
2020年 | 410篇 |
2019年 | 358篇 |
2018年 | 355篇 |
2017年 | 432篇 |
2016年 | 448篇 |
2015年 | 541篇 |
2014年 | 742篇 |
2013年 | 698篇 |
2012年 | 893篇 |
2011年 | 912篇 |
2010年 | 617篇 |
2009年 | 671篇 |
2008年 | 682篇 |
2007年 | 728篇 |
2006年 | 627篇 |
2005年 | 527篇 |
2004年 | 408篇 |
2003年 | 362篇 |
2002年 | 268篇 |
2001年 | 250篇 |
2000年 | 218篇 |
1999年 | 164篇 |
1998年 | 134篇 |
1997年 | 112篇 |
1996年 | 98篇 |
1995年 | 100篇 |
1994年 | 83篇 |
1993年 | 47篇 |
1992年 | 63篇 |
1991年 | 49篇 |
1990年 | 46篇 |
1989年 | 39篇 |
1988年 | 28篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1961年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
走刀方向对数控加工的效率有重要影响,尤其对于多曲面拼接自由曲面不规则轮廓区域的数控加工。针对现有自由曲面数控加工过程走刀方向优化研究存在的问题,提出了基于曲面数控加工区域划分的走刀方向优化策略,建立了简化的刀具轨迹计算模型和加工时间模型,并用实例加以验证,取得了满意的效果。 相似文献
92.
93.
94.
How the environment determines banking efficiency: a comparison of banking firms in Taiwan,Hong Kong,and Mainland China 下载免费PDF全文
Jonchi Shyu Pang‐Tien Lieu Wei Chang 《International Transactions in Operational Research》2015,22(4):757-770
This study uses the three‐stage data envelopment analysis (DEA) model to explore the true managerial efficiency of the banking firms in Taiwan, Hong Kong, and Mainland China. The empirical results indicate that the environmental conditions have a significant impact on banking efficiency. When the country‐specific situations are important factors in explaining efficiency difference, the common frontier estimates obtained by neglecting those factors can generate biased and overestimated inefficiency levels. With findings obtained from the slack variable analyses, the current study can provide inefficient banks with ways to reduce their input waste through the adjustment of input allocations. The findings also confirm the importance of the three‐stage DEA and its applications in determining the true managerial efficiencies of banks. Without the three‐stage DEA, the management could be misguided when making strategic decisions and conducting inappropriate resource allocation. 相似文献
95.
To join a medium or thick plate weldment with a full penetration, a groove is usually prepared in the space between two sections of metal. Because weld metal needs to be deposited within the groove to form the joint, it is expected that different groove type will require different heat input, which may consequently have influence on welding residual stress and deformation. Generally, different groove corresponds to different bead layout, so it can be foreseen that the groove type has a significant effect on temperature history, shape and size of heat affected zone, and region of sensitization in certain alloys such as austenitic stainless steel. The influences of groove type on residual stress, angular distortion and width of sensitization region in a SUS304 butt-welded joint were investigated by means of numerical simulation and experiment. Based on ABAQUS code, a computational approach with considering thermo-mechanical coupling behaviors, moving heat source, strain hardening and annealing effect was developed to simulate temperature profile, stress field and deformation in multi-pass joint. Welding temperature cycles, residual stress distributions and deformations in V, K and X groove joints were calculated through using the proposed computational procedure. Meanwhile, experiments were carried out to obtain residual stress distributions and angular distortions. Through comparing the numerical results and the measured data, the effectiveness and accuracy of the developed computational approach were verified. The simulation results show that groove type has a significant influence on welding residual stress distribution, angular distortion and width of sensitization region. 相似文献
96.
97.
Feng Tyan 《Asian journal of control》2016,18(3):899-919
In this work, the capture region of the general ideal proportional navigation guidance law is analyzed with the following constraints: (i) the target's input acceleration is subject to independent or magnitude saturation, and (ii) the missile's input acceleration is subject to magnitude saturation. In addition to the case of unbounded maneuverability of missile with or without knowing the target acceleration, the necessary and sufficient condition for a bounded maneuvering missile that captures a nonmaneuvering target is also derived. Furthermore, the conditions that result in zero impact velocity are discovered and discussed in some of the cases. The capture regions that cannot be obtained analytically are determined numerically by a powerful classifier, the least square support vector machines. To have the capture region ready for least square support vector machines, all the state variables are transformed into modified polar variables and non‐dimensionalized to reduce the number of independent variables. In order to make the implementation possible in real time, an approximation of the Gaussian radial basis function is adopted to obtain the corresponding nonlinear feature mapping function. Through numerous numerical experiments, the proposed technique is found to be adequate for storing the capture region in an onboard fire control computer. 相似文献
98.
In this paper, we present an energy-efficient method for distributed region formation flying of nanosatellites. The proposed framework consists of two concurrent sub-schemes that include estimation and formation. In the estimation sub-scheme, unlike the existing methods on satellite formation flying, that assume the availability of the reference orbital elements to all followers, here, a distributed estimator is developed so that the follower nanosatellites estimate the position of the leader in its orbital slot. In the formation sub-scheme, we consider a region formation strategy which is an efficient method in dealing with the formation of a large number of nanosatellites. We propose an optimal region following formation method based on the receding horizon control (RHC) using the estimated reference orbital elements. Subsequently, an algorithm is presented to solve the proposed energy-efficient formation flying method. Finally, the simulation result is presented that illustrates the purposed method improves the power consumption for each nanosatellite with respect to the existing non-optimal region formation flying controllers. 相似文献
99.
新疆汉水泉地区地下水环境背景值计算 总被引:2,自引:0,他引:2
以新疆汉水泉地区为研究区,依据其水文地质条件,将其划分为两个相对独立的水文地质单元——库木苏洼地和汉水泉洼地,采集该地区39组地下水水样,研究该地区的地下水环境背景值。采用格鲁布斯检验法剔除采集样本中的异常数据,库木苏洼地剔除异常指标1个,汉水泉洼地剔除异常指标13个。采用夏皮洛—威尔克检验法判断地下水化学组分含量频数分布类型,结果表明:库木苏洼地和汉水泉洼地以正态分布和对数正态分布居多,偏态分布较少。通过对整个汉水泉地区地下水组分含量的分析,得出汉水泉地区地下水环境的背景值,分析结果表明:研究区微量元素的检出率不高,表示其受污染程度较低。 相似文献
100.
宝塔坪滑坡是三峡库区现有成因复杂的巨型老滑坡之一,长期以来,工程界对其形成机制一直有着不同的认识。通过详细的现场调查和对勘察资料的深入分析,基于滑坡形态和结构特征,进一步探讨了宝塔坪滑坡的形成机制和演化过程。研究发现:滑坡发育受控于巴东组三段泥灰岩内部及其与二段泥岩之间的层间错动带、坡体后部卸荷裂隙带和长江下切提供的高陡临空面。根据巴东组四段紫红色泥岩在滑坡区不同高程的分布和滑坡结构分析,滑坡形成及演化具有典型“多期活动,逐级牵引”模式。该滑坡共分3期活动历史,地质力学模式均为“临空面形成-卸荷裂隙带发育-泥化的层间错动带塑流沉陷-蠕滑拉裂-滑面贯通”。每期活动牵引后部坡体变形,进而重复前一期的变形破坏过程。 相似文献