全文获取类型
收费全文 | 65432篇 |
免费 | 8684篇 |
国内免费 | 5718篇 |
专业分类
电工技术 | 6685篇 |
技术理论 | 1篇 |
综合类 | 7620篇 |
化学工业 | 5767篇 |
金属工艺 | 2296篇 |
机械仪表 | 5576篇 |
建筑科学 | 7585篇 |
矿业工程 | 2045篇 |
能源动力 | 2118篇 |
轻工业 | 6803篇 |
水利工程 | 2189篇 |
石油天然气 | 2185篇 |
武器工业 | 1193篇 |
无线电 | 5065篇 |
一般工业技术 | 7570篇 |
冶金工业 | 2345篇 |
原子能技术 | 658篇 |
自动化技术 | 12133篇 |
出版年
2024年 | 462篇 |
2023年 | 1302篇 |
2022年 | 2457篇 |
2021年 | 2613篇 |
2020年 | 2783篇 |
2019年 | 2320篇 |
2018年 | 2298篇 |
2017年 | 2771篇 |
2016年 | 3073篇 |
2015年 | 3144篇 |
2014年 | 4147篇 |
2013年 | 4252篇 |
2012年 | 5375篇 |
2011年 | 5276篇 |
2010年 | 3879篇 |
2009年 | 3804篇 |
2008年 | 3620篇 |
2007年 | 4262篇 |
2006年 | 3685篇 |
2005年 | 3072篇 |
2004年 | 2448篇 |
2003年 | 2086篇 |
2002年 | 1660篇 |
2001年 | 1489篇 |
2000年 | 1301篇 |
1999年 | 1057篇 |
1998年 | 876篇 |
1997年 | 739篇 |
1996年 | 600篇 |
1995年 | 538篇 |
1994年 | 454篇 |
1993年 | 358篇 |
1992年 | 285篇 |
1991年 | 223篇 |
1990年 | 203篇 |
1989年 | 177篇 |
1988年 | 129篇 |
1987年 | 83篇 |
1986年 | 48篇 |
1985年 | 52篇 |
1984年 | 58篇 |
1983年 | 33篇 |
1982年 | 39篇 |
1981年 | 15篇 |
1980年 | 39篇 |
1979年 | 38篇 |
1965年 | 16篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1955年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Christina Dirk‐Faitakis D Grant Allen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(7):737-745
This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, Cg, max/Cg, relative value of the half‐saturation constant in the Monod expression, Ks, and effective diffusivity of α‐pinene in the biofilm, De. Copyright © 2005 Society of Chemical Industry 相似文献
42.
Displacement Discontinuity Method for Fracture Mechanics Analysis of Reissner Plates: Static and Dynamic 总被引:1,自引:0,他引:1
This paper is concerned with the displacement discontinuity method applied to the shear deformable plates (Reissner’s and
Mindlin’s theories) with cracks subjected to static and dynamic loads. Fundamental solutions of dislocation are derived using
the Fourier transform method and the Laplace transformation technique. Boundary integral equations are presented in terms
of rotations/displacement on the crack surfaces. The Chebyshev polynomials of the second kind are used to evaluate the integral
equations with hypersingular kernels on the crack boundaries and determine the stress intensity factors at the crack tips.
Comparisons are made with other numerical solutions to demonstrate the proposed method is accurate both for static and dynamic
problems. 相似文献
43.
44.
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
45.
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
46.
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
47.
以网络技术和信息技术为依托,建立职业安全健康动态监控信息系统,进行职业安全健康管理的监控和预警,提高安全管理的现代化水平。 相似文献
48.
Herbert S. Bennett 《Journal of research of the National Institute of Standards and Technology》2007,112(4):209-221
In this paper, we present the theory for calculating Raman line shapes as functions of the Fermi energy and finite temperatures in zinc blende, n-type GaAs for donor densities between 1016 cm−3 and 1019 cm−3. Compared to other theories, this theory is unique in two respects: 1) the many-body effects are treated self-consistently and 2) the theory is valid at room temperature for arbitrary values of the ratio R = (Q2/α), where Q is the magnitude of the normalized wave vector and α is the normalized frequency used in the Raman measurements. These calculations solve the charge neutrality equation self-consistently for a two-band model of GaAs at 300 K that includes the effects of high carrier concentrations and dopant densities on the perturbed densities of states used to calculate the Fermi energy as a function of temperature. The results are then applied to obtain the carrier concentrations from Fermi energies in the context of line shapes in Raman spectra due to the coupling between longitudinal optical phonons and plasmons. Raman measurements have been proposed as a non-destructive method for wafer acceptance tests of carrier density in semiconductor epilayers. The interpretation of Raman spectra to determine the majority electron density in n-type semiconductors requires an interdisciplinary effort involving experiments, theory, and computer-based simulations and visualizations of the theoretical calculations. 相似文献
49.
The authors used visual search tasks in which components of the classic flanker task (B. A. Eriksen & C. W. Eriksen, 1974) were introduced. In several experiments the authors obtained evidence of parallel search for a target among distractor elements. Therefore, 2-stage models of visual search predict no effect of the identity of those distractors. However, clear compatibility effects of the distractors were obtained: Responses were faster when the distractors were compatible with the response than when they were incompatible. These results show that even in parallel search tasks identity information is extracted from the distractors. In addition, alternative interpretations of the results in terms of the occasional identification of a distractor before or after the target was identified could be ruled out. The results showed that flat search slopes obtained in visual search experiments provide no benchmark for preattentive processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献