全文获取类型
收费全文 | 6769篇 |
免费 | 624篇 |
国内免费 | 457篇 |
专业分类
电工技术 | 318篇 |
综合类 | 1148篇 |
化学工业 | 276篇 |
金属工艺 | 82篇 |
机械仪表 | 292篇 |
建筑科学 | 268篇 |
矿业工程 | 56篇 |
能源动力 | 115篇 |
轻工业 | 282篇 |
水利工程 | 99篇 |
石油天然气 | 49篇 |
武器工业 | 24篇 |
无线电 | 733篇 |
一般工业技术 | 905篇 |
冶金工业 | 182篇 |
原子能技术 | 53篇 |
自动化技术 | 2968篇 |
出版年
2024年 | 19篇 |
2023年 | 72篇 |
2022年 | 86篇 |
2021年 | 121篇 |
2020年 | 181篇 |
2019年 | 180篇 |
2018年 | 156篇 |
2017年 | 184篇 |
2016年 | 221篇 |
2015年 | 225篇 |
2014年 | 328篇 |
2013年 | 512篇 |
2012年 | 422篇 |
2011年 | 482篇 |
2010年 | 355篇 |
2009年 | 413篇 |
2008年 | 401篇 |
2007年 | 408篇 |
2006年 | 373篇 |
2005年 | 306篇 |
2004年 | 278篇 |
2003年 | 253篇 |
2002年 | 254篇 |
2001年 | 192篇 |
2000年 | 177篇 |
1999年 | 156篇 |
1998年 | 144篇 |
1997年 | 142篇 |
1996年 | 125篇 |
1995年 | 109篇 |
1994年 | 87篇 |
1993年 | 77篇 |
1992年 | 66篇 |
1991年 | 47篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 24篇 |
1983年 | 22篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1976年 | 9篇 |
1965年 | 5篇 |
1963年 | 4篇 |
排序方式: 共有7850条查询结果,搜索用时 15 毫秒
1.
A method is proposed to generate categorical colour observer functions (individual colour matching functions) for any field size based on the CIE 2006 system of physiological observer functions. The method combines proposed categorical observer techniques of Sarkar et al with a physiologically-based individual observer model of Asano et al and a clustering technique to produce the optimal set of categorical observers. The number of required categorical observers varies depending on an application with as many as 50 required to predict individual observers' matches when a laser projector is viewed. However, 10 categorical observers are sufficient to represent colour-normal populations for personalized colour imaging. The proposed and recommended categorical observers represent a robust and inclusive technique to examine and quantify observer metamerism in any application of colorimetry. 相似文献
2.
Output feedback controller for polytopic systems exploiting the direct searching of the design space
This paper deals with the problem of designing a robust static output feedback controller for polytopic systems. The current research that tackled this problem is mainly based on LMI method, which is conservative by nature. In this paper, a novel approach is proposed, which considers the design space of the controller parameters and iteratively partitions the space to small simplexes. Then, by assessing the stability in each simplex, the solution space for design parameters is directly determined. It has been theoretically proved that, if there exists a feasible solution in the design space, the algorithm can find it. To validate the result of the proposed approach, comparative simulation examples are given to illustrate the performance of the design methodology as compared to those of previous approaches. 相似文献
3.
The aim of the research is evaluating the classification performances of eight different machine-learning methods on the antepartum cardiotocography (CTG) data. The classification is necessary to predict newborn health, especially for the critical cases. Cardiotocography is used for assisting the obstetricians’ to obtain detailed information during the pregnancy as a technique of measuring fetal well-being, essentially in pregnant women having potential complications. The obstetricians describe CTG shortly as a continuous electronic record of the baby's heart rate took from the mother's abdomen. The acquired information is necessary to visualize unhealthiness of the embryo and gives an opportunity for early intervention prior to happening a permanent impairment to the embryo. The aim of the machine learning methods is by using attributes of data obtained from the uterine contraction (UC) and fetal heart rate (FHR) signals to classify as pathological or normal. The dataset contains 1831 instances with 21 attributes, examined by applying the methods. In the paper, the highest accuracy displayed as 99.2%. 相似文献
4.
In this paper, novel computing approach using three different models of feed-forward artificial neural networks (ANNs) are presented for the solution of initial value problem (IVP) based on first Painlevé equation. These mathematical models of ANNs are developed in an unsupervised manner with capability to satisfy the initial conditions exactly using log-sigmoid, radial basis and tan-sigmoid transfer functions in hidden layers to approximate the solution of the problem. The training of design parameters in each model is performed with sequential quadratic programming technique. The accuracy, convergence and effectiveness of the proposed schemes are evaluated on the basis of the results of statistical analyses through sufficient large number of independent runs with different number of neurons in each model as well. The comparisons of these results of proposed schemes with standard numerical and analytical solutions validate the correctness of the design models. 相似文献
5.
6.
The object of study is nonlinear stationary controlled system of ordinary differential equations with constant disturbance in the right part. The problem of constructing the synthesising control function providing the transfer of this system from the initial state to the origin is considered. The sufficiently simple for numerical implementation algorithm of solution of the above-mentioned problem is obtained. It is shown that for local null controllability of the considered system, it is sufficient that the conditions of the Kalman's type were satisfied. In addition, the estimates restricting the choice of initial conditions and external disturbances under which the transfer is guaranteed are obtained. The main idea of the method of construction of the desired control function consists in reducing the original problem to stabilisation of a special kind linear non-stationary system and solving the Cauchy problem for an auxiliary system of ordinary differential equations closed by stabilising control. The simplicity of the realisation of this algorithm is determined by the construction of the auxiliary system and its stabilisation that could be obtained by analytical methods. The effectiveness of the method is illustrated by solving the problem of crane control and its numerical simulation. 相似文献
7.
Online gaming addiction has been increasingly recognized as a mental disorder. However, the predictive factors that lead to online gaming addiction are not well established. The aim of this study was to identify factors that may influence the development of online gaming addiction. A total of 263 patients with problematic online gaming addiction (255 males (97%) and 8 females (3%), age: mean = 20.4 ± 5.8 years) and153 healthy comparison subjects (118 males (77%) and 35 females (23%), age: 21.2 ± 5.5 years, range) were recruited for participation in the current study. Hierarchical logistic regression analyses among each set of variables were conducted. Individual factors (sex and age), cognitive factors (IQ and perseverative errors), psychopathological conditions (ADHD, depression, anxiety, and impulsivity), and social interaction factors (family environment, social anxiety, and self-esteem) were evaluated in a stepwise fashion. All four factors were associated with online gaming addiction, with psychopathological conditions being the strongest risk factors for the addiction. Individual factors, psychological factors, and social interactions were associated with the development of pure online gaming addiction. As before, psychological factors (attention, mood, anxiety and impulsivity) were the strongest risk factors for online gaming addiction in patients with pure online gaming addiction. Psychopathologies, including ADHD and depression, were the strongest factors associated with the development of online gaming addiction in individuals. 相似文献
8.
针对传统的小区内开环功率控制算法通常以提升本小区的吞吐量性能为目标,忽略了当前小区用户对邻小区用户同频干扰的问题,为提升边缘用户性能的同时兼顾系统整体性能,提出了一种LTE系统小区间上行联合功率控制(UJPC)算法。该算法采用单基站三扇区为系统模型,以最优化系统吞吐量比例公平函数为目标,首先根据最小信干噪比(SINR)约束值和用户最大发射功率这两个约束条件得到相应的数学优化模型,然后采用连续凸近似的方法求解优化问题得出各个基站所管辖的小区内所有用户的最优发射功率。仿真结果表明,与基准的开环功控方案相比,联合功控方案在保证系统平均频谱利用率的情况下能够较大幅度地提高小区边缘频谱利用率,其最佳性能增益能达到50%。 相似文献
9.
10.
E-business success factors are Important for traditional enterprises to implement e-business. This topic is attracting more and more researchers to study. This paper makes an exploratory study on the factors influencing e-business success. Firstly, based on the literature review, 52 factors are suggested. Secondly, two rounds of survey with Delphi method are conducted. Qualitative and quantitative analysis are used to identify 57 factors. This is the foundation of empirical study. 相似文献