全文获取类型
收费全文 | 540篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 124篇 |
金属工艺 | 12篇 |
机械仪表 | 16篇 |
建筑科学 | 15篇 |
能源动力 | 20篇 |
轻工业 | 30篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 73篇 |
一般工业技术 | 103篇 |
冶金工业 | 47篇 |
原子能技术 | 3篇 |
自动化技术 | 93篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 33篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 42篇 |
2012年 | 23篇 |
2011年 | 45篇 |
2010年 | 26篇 |
2009年 | 19篇 |
2008年 | 35篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 18篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 31 毫秒
81.
No doubt that chlorination has been successfully used for the control of water borne infections diseases for more than a century. However identification of chlorination byproducts (CBPs) and incidences of potential health hazards created a major issue on the balancing of the toxicodynamics of the chemical species and risk from pathogenic microbes in the supply of drinking water. There have been epidemiological evidences of close relationship between its exposure and adverse outcomes particularly the cancers of vital organs in human beings. Halogenated trihalomethanes (THMs) and haloacetic acids (HAAs) are two major classes of disinfection byproducts (DBPs) commonly found in waters disinfected with chlorine. The total concentration of trihalomethanes and the formation of individual THM species in chlorinated water strongly depend on the composition of the raw water, on operational parameters and on the occurrence of residual chlorine in the distribution system. Attempts have been made to develop predictive models to establish the production and kinetics of THM formations. These models may be useful for operational purposes during water treatment and water quality management. It is also suggested to explore some biomarkers for determination of DBP production. Various methods have been suggested which include adsorption on activated carbons, coagulation with polymer, alum, lime or iron, sulfates, ion exchange and membrane process for the removal of DBPs. Thus in order to reduce the public health risk from these toxic compounds regulation must be inforced for the implementation of guideline values to lower the allowable concentrations or exposure. 相似文献
82.
Polymerization of methyl methacrylate (MMA) by the charge-transfer complex formed by the interaction of 2,2′-bipyridine (bpy), MMA, and carbon tetrachloride (CCl4) was studied in dimethylsulfoxide (DMSO) at 60°C. The rate of polymerization (Rp) is sensitive to the [CCl4] at low concentration of CCl4, but at a higher concentration it is practically independent of [CCl4]. Rp is proportional to [MMA]1.45±0.04 and [bpy]0.52±0.04 when [CCl4] > [bpy], and the average rate constant, k, at 60°C for the polymerization of MMA was 7.14 ± 0.40 × 10−6 L mol−1s−1. Kinetic studies showed that the polymerization proceeds through free radical intermediates. This article also reports the polymerization of MMA initiated by bpy and CCl4 and accelerated by Lewis acid, hexakis (dimethylsulfoxide)iron(III) perchlorate [Fe(DMSO)6](ClO4)3 at 60°C. The glass transition temperature and molecular weights of the samples were investigated by using differential scanning calorimetry and gel permeation chromatography techniques, respectively. Probable reaction mechanisms are proposed to explain the observed results. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2097–2103, 1997 相似文献
83.
Lois J. Gschwender Carl E. Snyder Shashi K. Sharma Stephanie R. Flanagan 《Lubrication Science》1999,16(1):35-50
The US Air Force Wright Laboratory's Materials Directorate has been involved with the development and transition of advanced fluids and lubricants since the 1950s. The driving force for the development of new hydraulic fluids has primarily been and still is, improved fire resistance, although biodegradability and low toxicity have become increasingly important. This paper briefly traces the use of military aircraft hydraulic fluids from the beginning to the current state-of-the-art. 相似文献
84.
85.
Conventional cell separation against multiple markers generally requires the attachment of antibody tags, typically fluorescent or magnetic, to selected cell types in a heterogeneous suspension. This work describes how such separation can be accomplished in a series of microfluidic systems without the need for such tags. Two capture stages containing antibody-functionalized alginate hydrogels are utilized for the isolation of CD34+ and Flk1+ cells from untreated, whole human blood. The capture-release capability of these degradable coatings is harnessed by a mixing chamber and a simple valving system such that the suspension emerging from the first capture stage is prepared for the second capture stage for further enrichment. With this configuration, we demonstrate the isolation of CD34+/Flk1+ endothelial progenitor cells from blood enabled by the depletion of CD34+/Flk1-hematopoietic stem cells population. This ability to achieve isolation of cells against multiple markers in an untagged separation method is of particular significance in applications involving cell implantation-based therapeutics including tissue engineering and molecular analysis. 相似文献
86.
Integrated Framework for Quantifying and Predicting Weather-Related Highway Construction Delays 总被引:1,自引:0,他引:1
Somkiat Apipattanavis Kevin Sabol Keith R. Molenaar Balaji Rajagopalan Yunping Xi Ben Blackard Shekhar Patil 《Canadian Metallurgical Quarterly》2010,136(11):1160-1168
Constant exposure to the environment makes highway construction highly dependent on weather. However, highway construction contracts are often unclear about the potential influence of weather-related delays on highway construction project schedules. There is a need to discourage litigation arising from weather-related delays by including in contracts a reasonable number of nonwork days as a consequence of adverse weather and providing an equitable criteria for the course of action when the predictions in the contracts turn out to be inaccurate. To address this need, an integrated framework consisting of the following two key components is proposed: (1) identification of attributes of weather that cause construction delays and (2) generation of synthetic weather sequences using a stochastic weather generator to quantify and provide probabilistic forecasts of weather threshold values. The utility of this framework is demonstrated through its application to construction work on a project in Texas. The use of probabilistic forecast of construction delay attributes provided by a semiparametric weather generator in this research is an example of interdisciplinary study to help address this problem. The result of the research is better decision support for agencies who wish to author contracts that more equitably allow for the influence of weather during construction. 相似文献
87.
Anurag Gupta Hannu Huhtinen Chandra Shekhar Kim Schlesier Pankaj Srivastava Amit Srivastava O. N. Srivastava Reino Laiho A. V. Narlikar 《Journal of Superconductivity and Novel Magnetism》2010,23(8):1461-1466
Superconductivity in a LaOFeAs system is known to get introduced by F-doping (LaO1−x
F
x
FeAs) even under ambient conditions and oxygen deficiency (LaO1−x
FeAs) under high pressure conditions. Hitherto unreported, superconductivity in F-free undoped LaOFeAs samples is observed
and confirmed for the first time by various characterization tools–resistive ρ(T,B), magnetic M(T,B) and modulated microwave absorption (MMA) measurements. The ρ(T) at B=0 shows a clear superconducting transition with an onset at T
con∼17 K and a tail-like behavior when R goes to zero at T
c0∼8 K. In the presence of B, the superconducting transition shifts to lower T with a rate ∼−5.5 and −1.65 T/K, depending on whether the ρ(T) has dropped to 90% or 5% of its normal state value, respectively. M(T) in zero field cooling at B=10 mT shows diamagnetic downturn below at ∼12 K. At T<T
c0 the change in MMA with B shows a low field (B∼1 mT) peak, which vanishes at T>T
c0, indicating the presence of weak link superconducting networks in the sample. The sample shows a complex electrical and magnetic
behavior in the normal state. For instance, ρ(T) reveals a weak SDW-like anomaly at T∼132 K along with a resistivity minimum at T
min ∼78 K. M(T) also shows the presence of a magnetic anomaly at T∼130 K. Both below and above T
con, presence of an additional ferromagnetic component is observed in the isothermal M(B) loop measurements. The superconducting and normal state features of our sample are compared with other undoped and doped
LaOFeAs systems reported in the literature. 相似文献
88.
Microstructure and Property Evolution for Hot-Rolled and Cold-Rolled Austenitic Stainless Steel 316L
Nitin Kumar Sharma Shashank Shekhar 《Transactions of the Indian Institute of Metals》2017,70(5):1277-1284
Grain boundary character distribution plays an important role in determining the functional and mechanical properties of polycrystalline materials. The aim of this work was to achieve improved coincident site lattice (CSL) fraction without increasing low angle grain boundary (LAGB) proportion. We utilized single-step thermo-mechanical processing route involving rolling followed by short heat treatment and compared the effect of rolling temperature. Our results indicated that rolling at elevated temperature led to significant increase in the fraction of special boundaries while keeping the fraction of LAGB very low, as desired. We conducted thermal stability of our sample-conditions at elevated temperatures for various lengths of time and found the microstructure of the samples to be stable up to 1000 °C. This study showed that even commercially suitable process (single step processing with short heat treatment duration) could lead to microstructure with considerable increase in CSL boundaries fraction, improved hardness values and good thermal stability. 相似文献
89.
90.
A modified approach for the collimation testing of an incoherent optical beam using the Lau effect coupled with moiré readout is proposed. In the experimental set-up a white-light incoherent source illuminates a coarse grating G1. The collimating lens is mounted on a translation stage, so that the grating G1 can be adjusted to be at the ‘in-focus’, ‘at-focus’ or ‘out-of-focus’ position. Grating G2 and grating G3 are mounted on a precision rotational stage and are so positioned that the lines of the gratings make a small but equal and opposite angle with the vertical. The inclination angle of the resulting moiré fringe demonstrates the quality of collimation of optical beam. The proposed technique can also be conveniently used for measurement of the focal length of a collimating lens, at a very low cost. 相似文献