全文获取类型
收费全文 | 12234篇 |
免费 | 96篇 |
国内免费 | 141篇 |
专业分类
电工技术 | 143篇 |
综合类 | 2篇 |
化学工业 | 631篇 |
金属工艺 | 453篇 |
机械仪表 | 83篇 |
建筑科学 | 183篇 |
矿业工程 | 4篇 |
能源动力 | 103篇 |
轻工业 | 383篇 |
水利工程 | 48篇 |
石油天然气 | 13篇 |
无线电 | 453篇 |
一般工业技术 | 322篇 |
冶金工业 | 601篇 |
原子能技术 | 99篇 |
自动化技术 | 8950篇 |
出版年
2023年 | 9篇 |
2022年 | 48篇 |
2021年 | 75篇 |
2020年 | 23篇 |
2019年 | 44篇 |
2018年 | 42篇 |
2017年 | 34篇 |
2016年 | 51篇 |
2015年 | 38篇 |
2014年 | 259篇 |
2013年 | 265篇 |
2012年 | 842篇 |
2011年 | 3160篇 |
2010年 | 1217篇 |
2009年 | 1060篇 |
2008年 | 765篇 |
2007年 | 650篇 |
2006年 | 513篇 |
2005年 | 651篇 |
2004年 | 582篇 |
2003年 | 633篇 |
2002年 | 309篇 |
2001年 | 41篇 |
2000年 | 50篇 |
1999年 | 67篇 |
1998年 | 275篇 |
1997年 | 131篇 |
1996年 | 96篇 |
1995年 | 44篇 |
1994年 | 55篇 |
1993年 | 35篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 37篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1977年 | 21篇 |
1976年 | 30篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Dr. Emrah Kara Dr. Nis Valentin Nielsen Bergrun Eggertsdottir Dr. Bernd Thiede Dr. Sandip M. Kanse Dr. Geir Åge Løset 《Chembiochem : a European journal of chemical biology》2020,21(13):1875-1884
We describe a novel, easy and efficient combinatorial phage display peptide substrate-mining method to map the substrate specificity of proteases. The peptide library is displayed on the pVII capsid of the M13 bacteriophage, which renders pIII necessary for infectivity and efficient retrieval, in an unmodified state. As capture module, the 3XFLAG was chosen due to its very high binding efficiency to anti-FLAG mAbs and its independency of any post-translational modification. This library was tested with Factor-VII activating protease (WT-FSAP) and its single-nucleotide polymorphism variant Marburg-I (MI)-FSAP. The WT-FSAP results confirmed the previously reported Arg/Lys centered FSAP cleavage site consensus as dominant, as well as reinforcing MI-FSAP as a loss-of-function mutant. Surprisingly, rare substrate clones devoid of basic amino acids were also identified. Indeed one of these peptides was cleaved as free peptide, thus suggesting a broader range of WT-FSAP substrates than previously anticipated. 相似文献
3.
Modern refractory castables contain between 3.5 and 5?wt.-% water that is necessary for sufficient flow during emplacement and for the formation of hydrate phases, necessary for the green strength of the material. Prior to the high temperature use of this material, it must be dried very carefully to avoid explosive spalling.This paper will demonstrate that beside conventional drying of pre-shaped materials in resistance furnaces microwave radiation is an energy saving and rapid method to remove pore water as well as hydrate bond water from the castable. In comparison to resistance furnaces, the use of microwave radiation does not affect the castable properties as there are mechanical strength (MOR, CCS), open porosity and pore size distribution. This study proved microwave radiation as valuable alternative with a series of tabular alumina based low cement castables (LLC) in which the water-to-cement-ratio (wcr = 0.64, 0.75, 0.82 and 1.13) was systematically altered by changing the cement concentration at constant mixing water concentration of 4.5%. 相似文献
4.
5.
Navab SinghAuthor Vitae Moitreyee Mukherjee-RoyAuthor VitaeSohan Singh MehtaAuthor Vitae 《Microelectronics Journal》2003,34(4):237-245
The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging. 相似文献
6.
Hannerz Harald; Albertsen Karen; Nielsen Martin Lindhardt; Tüchsen Finn; Burr Hermann 《Canadian Metallurgical Quarterly》2004,23(3):283
This study explored whether factors related to the work environment could predict changes in body mass index (BMI) and whether the effect of psychosocial factors was dependent on baseline BMI. The sample consisted of 1,980 male employees from the Danish National Work Environment Cohort Study. Changes in BMI between 1995 and 2000 were analyzed, by multiple regression, as a function of background variables and a series of occupational variables obtained in 1995. Age, baseline BMI, job insecurity, and psychological demands predicted changes in BMI. Job insecurity and high or low psychological demands increased the likelihood of weight gain among obese employees, whereas they increased the likelihood of weight loss among employees with a low BMI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Intensive fertilizer use has led to nitrate contamination of groundwater in many areas. This article examines the possibility of removing nitrates through the construction of artificial wetlands. A pilot study conducted in Denmark has found that the method is effective and economical, at least for small waterworks, though further treatment is necessary before an acceptable microbiological water quality is attained. 相似文献
8.
Adaptive motion control using neural network approximations 总被引:1,自引:0,他引:1
In this paper, we present a new adaptive technique for tracking control of mechanical systems in the presence of friction and periodic disturbances. Radial Basis Functions (RBFs) are used to compensate for the effects of nonlinearly occurring parameters in the friction and periodic disturbance model. Theoretical analysis, such as stability and transient performance, is provided. Furthermore, the performance of the adaptive RBF controller and its non-adaptive counterpart are compared. 相似文献
9.
Morten
rregaard Nielsen 《时间序列分析杂志》2005,26(2):279-304
Abstract. We consider semiparametric estimation in time‐series regression in the presence of long‐range dependence in both the errors and the stochastic regressors. A central limit theorem is established for a class of semiparametric frequency domain‐weighted least squares estimates, which includes both narrow‐band ordinary least squares and narrow‐band generalized least squares as special cases. The estimates are semiparametric in the sense that focus is on the neighbourhood of the origin, and only periodogram ordinates in a degenerating band around the origin are used. This setting differs from earlier studies on time‐series regression with long‐range dependence, where a fully parametric approach has been employed. The generalized least squares estimate is infeasible when the degree of long‐range dependence is unknown and must be estimated in an initial step. In that case, we show that a feasible estimate which has the same asymptotic properties as the infeasible estimate, exists. By Monte Carlo simulation, we evaluate the finite‐sample performance of the generalized least squares estimate and the feasible estimate. 相似文献
10.
Sludge reed bed facilities: operation and problems. 总被引:1,自引:0,他引:1
S Nielsen 《Water science and technology》2005,51(9):99-107
Short operating periods and problems with dewatering efficiency, vegetation, mineralisation and odour are primarily caused by incorrect construction of the filter, poor capillary connections, an inadequate number of basins, insufficient basin area and overloading during commissioning and during subsequent operation. Dimensioning should be based on the sludge quality including the dewatering qualities and not solely on calculations of the sludge production. Loading after planting depends on the development level of the vegetation. The loading program should ensure that reed establishment is not impeded and should prevent the sludge residue from growing so quickly horizontally and vertically that the reeds cannot colonise the sludge residue. Overloading results in an anaerobic sludge residue with ensuing methane production. Typically, a sludge reed bed facility with a loading period of maximum 5 days, must be built with 10 basins to permit a rest phase of about 40 days. Facilities with 8 basins, where it is possible to load 1 basin for 7 days, will be able to have a 7-week rest phase before the first basin is loaded again. Facilities with for example 8-13 basins and loading period of between 4 and 10 days are able to achieve rest periods of up to 2 to 2(1/2) months, which results in the optimal evapotranspiration and minerilization. The conditions and thus the possibilities vary depending upon the type of sludge. 相似文献