全文获取类型
收费全文 | 4075篇 |
免费 | 217篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 61篇 |
综合类 | 1篇 |
化学工业 | 813篇 |
金属工艺 | 86篇 |
机械仪表 | 71篇 |
建筑科学 | 80篇 |
矿业工程 | 10篇 |
能源动力 | 109篇 |
轻工业 | 494篇 |
水利工程 | 33篇 |
石油天然气 | 14篇 |
无线电 | 235篇 |
一般工业技术 | 504篇 |
冶金工业 | 1394篇 |
原子能技术 | 22篇 |
自动化技术 | 369篇 |
出版年
2024年 | 6篇 |
2023年 | 34篇 |
2022年 | 65篇 |
2021年 | 144篇 |
2020年 | 105篇 |
2019年 | 108篇 |
2018年 | 129篇 |
2017年 | 132篇 |
2016年 | 141篇 |
2015年 | 88篇 |
2014年 | 100篇 |
2013年 | 237篇 |
2012年 | 175篇 |
2011年 | 199篇 |
2010年 | 162篇 |
2009年 | 161篇 |
2008年 | 150篇 |
2007年 | 118篇 |
2006年 | 94篇 |
2005年 | 61篇 |
2004年 | 64篇 |
2003年 | 73篇 |
2002年 | 53篇 |
2001年 | 44篇 |
2000年 | 41篇 |
1999年 | 62篇 |
1998年 | 383篇 |
1997年 | 287篇 |
1996年 | 175篇 |
1995年 | 101篇 |
1994年 | 84篇 |
1993年 | 106篇 |
1992年 | 21篇 |
1991年 | 26篇 |
1990年 | 19篇 |
1989年 | 32篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 55篇 |
1976年 | 92篇 |
1973年 | 3篇 |
排序方式: 共有4296条查询结果,搜索用时 843 毫秒
21.
Pierre Darcy Patrick Da Costa Henry Mellotte Jean-Michel Trichard Grald Djga-Mariadassou 《Catalysis Today》2007,119(1-4):252-256
To comply with the new regulations on particulate matter, car manufacturers more and more commonly use diesel particulate filters (DPF). The working of these systems needs to periodically burn soot that has been accumulated during the loading of the DPF. This paper describes the kinetics of the non-catalytic and catalytic oxidation of real diesel soot with oxygen. From these experiments, mechanisms for catalyzed and non-catalyzed soot oxidation have been proposed. 相似文献
22.
da Costa D.B. Yacoub M.D. Filho J.C.S.S. Fraidenraich G. Mendes J.R. 《Communications Letters, IEEE》2006,10(1):13-15
This paper provides simple, exact, new closed-form expressions for the generalized phase crossing rate of Nakagami-m fading channels. Sample numerical results obtained by simulation are presented that validate the formulations developed here. A special case of this formulation is the Rayleigh case, whose result agrees with that obtained elsewhere in the literature. In passing, several new closed-form results concerning the statistics of the envelope, its in-phase and quadrature components, phase, and their time derivatives are obtained. 相似文献
23.
24.
Analysis of the function of the nervous system, based on clinical, neurological, and psychological studies in 78 patients with generalized periodontitis, revealed central regulation disorders without signs of organic lesions of the brain in 76% patients. The authors claim that stress and a high level of personal anxiety may be responsible for the development of these disorders, which was confirmed by the results of psychological testing. 相似文献
25.
26.
Ramon R. Costa Liu Hsu 《International Journal of Adaptive Control and Signal Processing》1992,6(1):19-33
A variable structure model reference adaptive controller (VS-MRAC) using only input and output measurements was recently proposed and shown to be globally asymptotically stable with superior transient behaviour and disturbance rejection properties. In this paper a singular perturbation approach is used in order to establish the robustness of the controller in the presence of unmodelled dynamics (parasitics) and disturbances. We develop a new Lyapunov-based technique to analyse the overall system and show that for sufficiently small parasitics the system remains stable and the output error is small in some sense. 相似文献
27.
We propose a new, less costly, design to test the equivalence of digital versus analogue mammography in terms of sensitivity and specificity. Because breast cancer is a rare event among asymptomatic women, the sample size for testing equivalence of sensitivity is larger than that for testing equivalence of specificity. Hence calculations of sample size are based on sensitivity. With the proposed design it is possible to achieve the same power as a completely paired design by increasing the number of less costly analogue mammograms and not giving the more expensive digital mammograms to some randomly selected subjects who are negative on the analogue mammogram. The key idea is that subjects who are negative on the analogue mammogram are unlikely to have cancer and hence contribute less information for estimating sensitivity than subjects who are positive on the analogue mammogram. To ascertain disease state among subjects not biopsied, we propose another analogue mammogram at a later time determined by a natural history model. The design differs from a double sampling design because it compares two imperfect tests instead of combining information from a perfect and imperfect test. 相似文献
28.
29.
This study sought to describe the changes in mortality among infants under one year of age in different areas of the city of Salvador, Bahia, during the period 1980-1988. This was done using estimates of variation in two indicators: proportional infant mortality and the coefficient of infant mortality. Values for the first indicator were separated into low, intermediate, high, and very high quartiles for 1980 and then calculated again using 1988 data. The second indicator was derived from the estimated number of live births using the rate of 33.4/1,000 inhabitants for 1980 and 31.4/1,000 for the years thereafter. The results showed that infant mortality in that age group had declined over the period, but that at the end of the period inequalities persisted in the distribution of infant deaths, which confirmed that conditions remained adverse for certain segments of the population. 相似文献
30.