全文获取类型
收费全文 | 248篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 66篇 |
金属工艺 | 3篇 |
机械仪表 | 3篇 |
能源动力 | 6篇 |
轻工业 | 18篇 |
无线电 | 38篇 |
一般工业技术 | 32篇 |
冶金工业 | 46篇 |
原子能技术 | 4篇 |
自动化技术 | 39篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 18篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 5篇 |
排序方式: 共有259条查询结果,搜索用时 31 毫秒
251.
Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 μg L(-1)) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg(-1)) and Barwa (3.1 mg kg(-1)). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO(2) (40-62 wt.%), Al(2)O(3) (9-21 wt.%) and K(2)O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity. 相似文献
252.
Saha K Bajaj A Duncan B Rotello VM 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(14):1903-1918
Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed. 相似文献
253.
The Indian PHWR 总被引:1,自引:0,他引:1
The nuclear power program in India at present is based mainly on a series of Pressurized Heavy Water Reactors (PHWRs). Starting from Rajasthan Atomic Power Station comprising two units of 200 MWe Canadian designed PHWRs in 1973, the program has come a long way with 12 PHWR units in operation and 6 units under construction which includes 2 units of 540 MWe PHWRs. Narora Atomic Power Station commissioned in 1991 marked major indigenization and standardization of PHWR designs. The choice of PHWRs in the current stage of India's Nuclear Power Plants program is based on long-term objectives in the right available resources and infrastructure. These reactors use natural uranium as fuel and heavy water as moderator and coolant. The nuclear power stations in India are generally planned as twin-unit modules, sharing common facilities such as service building, spent fuel bay, etc.This paper brings out the key features of the design of Indian PHWR, highlighting the areas of evolution in successive project. Also covered are highlights of the operating experience with these reactors. 相似文献
254.
Hijacking Chemical Reactions of P450 Enzymes for Altered Chemical Reactions and Asymmetric Synthesis
Eerappa Rajakumara Dubey Saniya Priyanka Bajaj Rajanna Rajeshwari Jyotsnendu Giri Mehdi D. Davari 《International journal of molecular sciences》2023,24(1)
Cytochrome P450s are heme-containing enzymes capable of the oxidative transformation of a wide range of organic substrates. A protein scaffold that coordinates the heme iron, and the catalytic pocket residues, together, determine the reaction selectivity and regio- and stereo-selectivity of the P450 enzymes. Different substrates also affect the properties of P450s by binding to its catalytic pocket. Modulating the redox potential of the heme by substituting iron-coordinating residues changes the chemical reaction, the type of cofactor requirement, and the stereoselectivity of P450s. Around hundreds of P450s are experimentally characterized, therefore, a mechanistic understanding of the factors affecting their catalysis is increasingly vital in the age of synthetic biology and biotechnology. Engineering P450s can enable them to catalyze a variety of chemical reactions viz. oxygenation, peroxygenation, cyclopropanation, epoxidation, nitration, etc., to synthesize high-value chiral organic molecules with exceptionally high stereo- and regioselectivity and catalytic efficiency. This review will focus on recent studies of the mechanistic understandings of the modulation of heme redox potential in the engineered P450 variants, and the effect of small decoy molecules, dual function small molecules, and substrate mimetics on the type of chemical reaction and the catalytic cycle of the P450 enzymes. 相似文献
255.
We present a general framework for a higher-order spline level-set(HLS) method and apply this to biomolecule surfaces construction. Starting from a first order energy functional,we obtain a general level set formulation of geometric partial differential equation,and provide an efficient approach to solving this partial differential equation using a C2 spline basis. We also present a fast cubic spline interpolation algorithm based on convolution and the Z-transform,which exploits the local relationship of interpolatory cubic spline coefficients with respect to given function data values. One example of our HLS method is demonstrated,which is the construction of biomolecule surfaces(an implicit solvation interface) with their individual atomic coordinates and solvated radii as prerequisites. 相似文献
256.
Shreya Pare Anil Kumar Varun Bajaj Girish Kumar Singh 《IEEE/CAA Journal of Automatica Sinica》2019,6(6):1471-1486
In this paper, a comprehensive energy function is used to formulate the three most popular objective functions: Kapur's, Otsu and Tsalli's functions for performing effective multilevel color image thresholding. These new energy based objective criterions are further combined with the proficient search capability of swarm based algorithms to improve the efficiency and robustness. The proposed multilevel thresholding approach accurately determines the optimal threshold values by using generated energy curve, and acutely distinguishes different objects within the multi-channel complex images. The performance evaluation indices and experiments on different test images illustrate that Kapur's entropy aided with differential evolution and bacterial foraging optimization algorithm generates the most accurate and visually pleasing segmented images. 相似文献
257.
258.
Void nucleation is a critical issue in wetting because it negatively impacts the solder joint and diminishes its electrical and mechanical properties. Generally, the Kirkendall effect (unbalanced diffusion) and Kirkendall voids (KVs) are developed due to dissimilar diffusivities of species (Cu and Sn) in a diffusion process. However, voids are also nucleated in the supersaturating condition, creating an additional position at or inside the “Kirkendall voids” interface. Various factors (surface modification, reinforcement of fourth elements, substrate type, and impurities) and the environment also support the nucleation of voids. Many researchers have discussed that KVs are nucleated into to intermetallic compounds layers. Reviewing the significant parameters for developing the KV in solid–liquid and solid–solid conditions is essential. Hence, in this review, the potential process of development of the KVs, concepts of thermodynamics, chemical reactions, and growth kinetics are developed. The position and reduction of KVs nucleation are also explained in this paper. 相似文献
259.
Deepika Sharma Gagangeet Singh Aujla Rohit Bajaj 《International Journal of Communication Systems》2023,36(12):e4058
The evolution of intelligent and data-driven systems has pushed for the tectonic transition from ancient medication to human-centric Healthcare 4.0. The rise of Internet of Things, Internet of Systems, and wireless body area networks has endowed the health care ecosystem with a new digital transformation supported by sophisticated machine learning and artificial intelligence algorithms. Under this umbrella, health care recommendation systems have emerged as a driver for providing patient-centric personalized health care services. Recommendation systems are automatic systems that derive the decisions on the basis of some valid input parameters and vital health information collected through wearable devices, implantable equipments, and various sensor. Therefore, to understand the state-of-the-art developments in the health care ecosystem, this paper provides a comprehensive survey on health care recommendation systems and the associated paradigms. This survey starts from the ancient health care era and move toward the Healthcare 4.0 in a phased manner. The road map from Healthcare 1.0 to Healthcare 4.0 is analyzed to highlight different technology verticals supporting the digital transformation. This study also provides the systematic review of the health care systems, the types of health care systems, and the recommender systems. Moreover, a deep analysis of health care recommender systems and its types is also presented. Finally, the open issues and challenges associated with the adaption and implementation of human-centric Healthcare 4.0 ecosystem are discussed. This is provided to find out the possible research questions and gaps so that the corresponding solutions could be developed in the near future. 相似文献