全文获取类型
收费全文 | 23248篇 |
免费 | 355篇 |
国内免费 | 122篇 |
专业分类
电工技术 | 499篇 |
综合类 | 64篇 |
化学工业 | 3176篇 |
金属工艺 | 940篇 |
机械仪表 | 658篇 |
建筑科学 | 547篇 |
矿业工程 | 67篇 |
能源动力 | 607篇 |
轻工业 | 1839篇 |
水利工程 | 213篇 |
石油天然气 | 179篇 |
武器工业 | 1篇 |
无线电 | 2600篇 |
一般工业技术 | 4079篇 |
冶金工业 | 6143篇 |
原子能技术 | 420篇 |
自动化技术 | 1693篇 |
出版年
2021年 | 150篇 |
2020年 | 115篇 |
2019年 | 162篇 |
2018年 | 231篇 |
2017年 | 230篇 |
2016年 | 257篇 |
2015年 | 176篇 |
2014年 | 298篇 |
2013年 | 825篇 |
2012年 | 508篇 |
2011年 | 780篇 |
2010年 | 560篇 |
2009年 | 625篇 |
2008年 | 719篇 |
2007年 | 747篇 |
2006年 | 631篇 |
2005年 | 720篇 |
2004年 | 590篇 |
2003年 | 639篇 |
2002年 | 676篇 |
2001年 | 672篇 |
2000年 | 601篇 |
1999年 | 617篇 |
1998年 | 2165篇 |
1997年 | 1405篇 |
1996年 | 1047篇 |
1995年 | 718篇 |
1994年 | 618篇 |
1993年 | 641篇 |
1992年 | 358篇 |
1991年 | 344篇 |
1990年 | 341篇 |
1989年 | 343篇 |
1988年 | 292篇 |
1987年 | 268篇 |
1986年 | 246篇 |
1985年 | 276篇 |
1984年 | 217篇 |
1983年 | 200篇 |
1982年 | 185篇 |
1981年 | 217篇 |
1980年 | 202篇 |
1979年 | 165篇 |
1978年 | 152篇 |
1977年 | 279篇 |
1976年 | 387篇 |
1975年 | 127篇 |
1974年 | 109篇 |
1973年 | 117篇 |
1972年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
In this paper, implementation of the Benchmark Simulation Model No 2 (BSM2) within Matlab-Simulink is presented. The BSM2 is developed for plant-wide WWTP control strategy evaluation on a long-term basis. It consists of a pre-treatment process, an activated sludge process and sludge treatment processes. Extended evaluation criteria are proposed for plant-wide control strategy assessment. Default open-loop and closed-loop strategies are also proposed to be used as references with which to compare other control strategies. Simulations indicate that the BM2 is an appropriate tool for plant-wide control strategy evaluation. 相似文献
12.
Intensive use of the benchmark simulation model No. 1 (BSM1), a protocol for objective comparison of the effectiveness of control strategies in biological nitrogen removal activated sludge plants, has also revealed a number of limitations. Preliminary definitions of the long-term benchmark simulation model No. 1 (BSM1_LT) and the benchmark simulation model No. 2 (BSM2) have been made to extend BSM1 for evaluation of process monitoring methods and plant-wide control strategies, respectively. Influent-related disturbances for BSM1_LT/BSM2 are to be generated with a model, and this paper provides a general overview of the modelling methods used. Typical influent dynamic phenomena generated with the BSM1_LT/BSM2 influent disturbance model, including diurnal, weekend, seasonal and holiday effects, as well as rainfall, are illustrated with simulation results. As a result of the work described in this paper, a proposed influent model/file has been released to the benchmark developers for evaluation purposes. Pending this evaluation, a final BSM1_LT/BSM2 influent disturbance model definition is foreseen. Preliminary simulations with dynamic influent data generated by the influent disturbance model indicate that default BSM1 activated sludge plant control strategies will need extensions for BSM1_LT/BSM2 to efficiently handle 1 year of influent dynamics. 相似文献
13.
K. Borer G. Czapek F. Hasenbalg M. Hauser S. Janos P. Loaiza U. Moser K. Pretzl C. Schütz P. Wicht S. Wüthrich 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):112-115
The ORPHEUS dark matter detector consists of 450 g superconducting tin granules with diameters of 28 and 36 μm. The detector has been operating in the shallow site of the underground laboratory in Bern (70 m.w.e). First preliminary results on WIMP detection sensitivity will be presented. 相似文献
14.
An efficient method for preparation of semiconductor quantum rod films for robust lasing in a cylindrical microcavity is reported. A capillary tube, serving as the laser cavity, is filled with a solution of nanocrystals and irradiated with a series of intense nanosecond laser pulses to produce a nanocrystal film on the capillary surface. The films exhibit intense room‐temperature lasing in whispering‐gallery modes that develop at the film–capillary interface as corroborated from the spacing detected for the lasing modes. Good lasing stability is observed at moderate pump powers. The method was applied successfully to several quantum‐rod samples of various sizes. 相似文献
15.
Kelson C. Lopes Flvia S. Pereira Regiane C. M. U. Araújo Mozart N. Ramos Roy E. Bruns 《Chemometrics and Intelligent Laboratory Systems》2004,70(2):157-163
Factorial design and principal component models are used to determine how ab initio H-bond stretching frequencies depend on characteristics of the molecular orbital wave functions of acetylene–HX, ethylene–HX and cyclopropane–HX π-type hydrogen complexes with X=F, Cl, CN, NC and CCH. The results obtained for the three sets of complexes show that factorial design and principal component analyses complement each other. Factorial design calculations clearly show that these frequencies are affected mostly by inclusion of electron correlation on the calculation level. On average, their values are increased by about 25 cm−1 due to a change from the Hartree–Fock (HF) to Möller–Plesset 2 (MP2) level. Valence, diffuse and polarization main effects as well as valence–diffuse, diffuse–correlation and polarization–correlation interaction effects are also important to better describe a factorial model to the H-bond stretching frequencies of these hydrogen complexes. This simplified model has been successful in reproducing the complete ab initio results, which correspond to two hundred and forty calculations. Principal component analyses applied only to hydrogen-bonded complexes whose experimental frequencies are known, has revealed that the six-dimensional original space can be accurately represented by a bidimensional space defined by two principal components. Its graphical representation reveals that the experimental intermolecular stretching frequencies are in closest agreement with the MP2/6–31+G and MP2/6–311+G ab initio results. 相似文献
16.
17.
We present calculations of the magnetoconductivity in a two-dimensional electron system including the Rashba spin-orbit interaction. Essential for these calculations is an extension of the self-consistent Born approximation which takes into account the electron spin degree of freedom. The calculated magnetoconductivity exhibits, besides the beating in the Shubnikov-de Haas oscillations, a modulation related to the spin-orbit induced crossings of Landau levels, as a consequence of spin-conserving scattering between spin-orbit coupled states. 相似文献
18.
19.
I. Budić-Leto T. Lovrić J. Gajdoš Kljusurić I. Pezo U. Vrhovšek 《European Food Research and Technology》2006,222(3-4):397-402
Identification of anthocyanins in the wine made of the Croatian autochthonous grape variety of Babić (Vitis vinifera L.) was carried out and their profile was determined by means of high-performance liquid chromatography with diode array
and mass spectrometric detection. Dependence of anthocyanins content and profile on maceration treatment conditions was investigated.
Statistically significant differences of anthocyanins concentration in wines Babić produced by various maceration treatments
were confirmed by the use of multivariate analysis of variances. The investigation results indicated that the maceration temperature
exerts higher influence on anthocyanins concentration than the duration of maceration. In addition, on the basis of anthocyanin
composition and using different multivariate statistical analyses, differentiation of wines Babić according to maceration
treatments was procured. 相似文献
20.
U. KEICH 《时间序列分析杂志》2003,24(2):173-192
Abstract. In Keich (2000 ),we define a stationary tangent process, or a locally optimal stationary approximation, to a real non-stationary smooth Gaussian process. This paper extends the idea by constructing a discrete tangent – a `locally' optimal stationary approximation – for a discrete time, real Gaussian process. Analogously to the smooth case, our construction relies on a generalization of the recursion formula for the orthogonal polynomials of the spectral distribution function. More precisely, we use a generalization of the Schur parameters to identify the stationary tangent. By way of discretizing, we later demonstrate how this tangent can be used to obtain `good' local stationary approximations to non-smooth continuous time, real Gaussian processes. Further, we demonstrate how, analogously to the curvatures in the smooth case, the Schur parameters can be used to determine the order of stationarity of a non-smooth process. 相似文献