全文获取类型
收费全文 | 150930篇 |
免费 | 6641篇 |
国内免费 | 3383篇 |
专业分类
电工技术 | 4679篇 |
技术理论 | 10篇 |
综合类 | 6761篇 |
化学工业 | 22744篇 |
金属工艺 | 8279篇 |
机械仪表 | 6849篇 |
建筑科学 | 7509篇 |
矿业工程 | 2385篇 |
能源动力 | 2987篇 |
轻工业 | 8856篇 |
水利工程 | 2542篇 |
石油天然气 | 4000篇 |
武器工业 | 528篇 |
无线电 | 17333篇 |
一般工业技术 | 24475篇 |
冶金工业 | 6001篇 |
原子能技术 | 973篇 |
自动化技术 | 34043篇 |
出版年
2024年 | 312篇 |
2023年 | 1190篇 |
2022年 | 2099篇 |
2021年 | 2895篇 |
2020年 | 2266篇 |
2019年 | 1802篇 |
2018年 | 16182篇 |
2017年 | 15266篇 |
2016年 | 11849篇 |
2015年 | 3275篇 |
2014年 | 3574篇 |
2013年 | 4084篇 |
2012年 | 7387篇 |
2011年 | 13950篇 |
2010年 | 12032篇 |
2009年 | 9142篇 |
2008年 | 10336篇 |
2007年 | 11112篇 |
2006年 | 3395篇 |
2005年 | 4061篇 |
2004年 | 3249篇 |
2003年 | 3039篇 |
2002年 | 2266篇 |
2001年 | 1643篇 |
2000年 | 1869篇 |
1999年 | 2063篇 |
1998年 | 1758篇 |
1997年 | 1427篇 |
1996年 | 1426篇 |
1995年 | 1159篇 |
1994年 | 1022篇 |
1993年 | 704篇 |
1992年 | 555篇 |
1991年 | 416篇 |
1990年 | 340篇 |
1989年 | 310篇 |
1988年 | 229篇 |
1987年 | 155篇 |
1986年 | 110篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 53篇 |
1968年 | 45篇 |
1966年 | 44篇 |
1965年 | 48篇 |
1958年 | 38篇 |
1957年 | 36篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
总体最小二乘估计能够同时顾及线性模型中系数矩阵[WTHX]A和观测向量L的
误差,平差理论相对更为严密。如果系数矩阵[WTHX]A[WTBZ]的部分元素没有误差,这种总体最小二乘模
型为混合总体最小二乘模型。针对混合总体最小二乘(Least squares total least squares, LS TLS)解算问题,应用测量平差中
的
原理和方法,推导了混合总体最小二乘的迭代逼近解算公式,通过与奇异值分解法分析比较
,分析了两种解算方法具有等价性,最后通过实验数据分析得出迭代算法的有效性
和合理性。 相似文献
992.
993.
在各个城市市政工程给水管道的施工中,相关部门在质量监测和管理等方面的工作中仍然存在不足之处。因此,如何解决市政工程给水管道施工中出现的各种故障,是相关施工人员值得思考的问题。 相似文献
994.
基于信息技术的课程整合作为小学信息技术教学的发展方向之一,越来越受到信息技术科任老师的关注。本文对基于网络环境的信息技术课程整合优势、网络环境在课程整合中的利用策略、网络环境下的信息技术课程整合的核心活动等方面进行了分析,探讨了如何利用网络技术促进信息技术课与其它学科的整合。 相似文献
995.
Alberto Schaeffer-Filho Emil Lupu Morris Sloman 《Journal of Network and Systems Management》2015,23(3):753-793
Ubiquitous systems and applications involve interactions between multiple autonomous entities—for example, robots in a mobile ad-hoc network collaborating to achieve a goal, communications between teams of emergency workers involved in disaster relief operations or interactions between patients’ and healthcare workers’ mobile devices. We have previously proposed the Self-Managed Cell (SMC) as an architectural pattern for managing autonomous ubiquitous systems that comprise both hardware and software components and that implement policy-based adaptation strategies. We have also shown how basic management interactions between autonomous SMCs can be realised through exchanges of notifications and policies, to effectively program management and context-aware adaptations. We present here how autonomous SMCs can be composed and federated into complex structures through the systematic composition of interaction patterns. By composing simpler abstractions as building blocks of more complex interactions it is possible to leverage commonalities across the structural, control and communication views to manage a broad variety of composite autonomous systems including peer-to-peer collaborations, federations and aggregations with varying degrees of devolution of control. Although the approach is more broadly applicable, we focus on systems where declarative policies are used to specify adaptation and on context-aware ubiquitous systems that present some degree of autonomy in the physical world, such as body sensor networks and autonomous vehicles. Finally, we present a formalisation of our model that allows a rigorous verification of the properties satisfied by the SMC interactions before policies are deployed in physical devices. 相似文献
996.
This work presents the design of a novel static-triggered power-rail electrostatic discharge (ESD) clamp circuit. The superior transient-noise immunity of the static ESD detection mechanism over the transient one is firstly discussed. Based on the discussion, a novel power-rail ESD clamp circuit utilizing the static ESD detection mechanism is proposed. By skillfully incorporating a thyristor delay stage into the trigger circuit (TC), the proposed circuit achieves the best ESD-conduction behavior while consuming the lowest leakage current (Ileak) at the normal bias voltage among all investigated circuits in this work. In addition, the proposed circuit achieves an excellent false-triggering immunity against fast power-up pulses. All investigated circuits are fabricated in a 65-nm CMOS process. Performance superiorities of the proposed circuit are fully verified by both simulation and test results. Moreover, the proposed circuit offers an efficient on-chip ESD protection scheme considering the worst discharge case in the utilized process. 相似文献
997.
Yanzhang Wang Shujun Wu Hao Lu Defu Cheng Chen Chen Na Pang Yunxia Wan Zhijian Zhou Siyu Chen 《中国科学:信息科学(英文版)》2016,59(11):112213
The output performance of residence times difference (RTD) fluxgate may vary under different driving conditions (driving currents and frequencies) and core materials. To optimize the RTD fluxgate and simplify its design process, an analytical model is employed to select the parameters and identify the effective factors that dominate the performance. The dynamic permeability parameters (Pi), which reflect the changes in the magnetization curve, are mathematically analyzed in detail. The linear variation functions of Pi in different driving conditions are fitted by using the dynamic arctangent hysteresis model. Consequently, the selection of driving conditions and core materials, which are assessed by comparing the experiment and simulation results, has an important role in achieving the optimal output performance of the RTD fluxgate. 相似文献
998.
H. SiraRamˇrez A. Hernandez MEndez J. Linares Flores A. Luviano Juarez 《控制理论与应用(英文版)》2016,14(3):224-236
The article deals with the design and implementation of a flat filter tracking digital controller for a boost dc-dc power converter. A highly perturbed switched boost converter circuit is shown to be efficiently controlled, in a trajectory tracking task for its non-minimum phase output, by means of a suitable linear filter, here addressed as a flat filter. Flat filtering is a natural robust
version of generalized proportional integral control (GPIC) by which the effects of arbitrary time varying exogenous disturbances, unknown endogenous nonlinearities and un-modeled dynamics can be jointly attenuated in a conceptually similar fashion to observer-based active disturbance rejection control (ADRC) and algebraic identification based model free control (MFC) but: a)
without using extended state observers and b) respecting the original system order in a time-varying simplified model while avoiding algebraic estimation techniques. The proposed control technique based on the TMS320F28335 digital signal processor chip is tested by means of realistic simulations and experimental setup. 相似文献
999.
B-spline curve extension is an important operation in computer aided design systems. In this paper, we present a new extension algorithm for B-spline curves. The algorithm uses curve unclamping to generate a uniform B-spline curve segment from the original curve and gradually extends the segment to pass through every target point. Algorithms of uniform B-spline curves are used such that our algorithm has a low time cost and can easily handle arbitrary-order derivative constraints at the target points. Generalization for non-uniform rational B-spline curve extension is also discussed, and examples show the efficiency of our method. 相似文献
1000.
This paper considers a unicast multiuser multiple-input single-output (MISO) downlink system overheard by multiple single-antenna eavesdroppers. The objective is to jointly design the beamforming vectors and the artificial noise (AN) covariance matrix with imperfect channel state information (CSI) at the transmitter, such that the total transmit power is minimized while satisfying probabilistic quality of service (QoS) constraints at legitimate users and the eavesdroppers. Using Bernstein-type inequalities and the S-procedure, we recast the non-convex power minimization problem as two different convex semidefinite programs (SDPs) which can be solved using interior-point methods. Simulation results show that the proposed methods outperform a nonrobust method and the ones using the isotropic AN. 相似文献