全文获取类型
收费全文 | 3136篇 |
免费 | 123篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 63篇 |
综合类 | 1篇 |
化学工业 | 609篇 |
金属工艺 | 68篇 |
机械仪表 | 75篇 |
建筑科学 | 69篇 |
矿业工程 | 5篇 |
能源动力 | 176篇 |
轻工业 | 199篇 |
水利工程 | 31篇 |
石油天然气 | 16篇 |
无线电 | 509篇 |
一般工业技术 | 695篇 |
冶金工业 | 294篇 |
原子能技术 | 32篇 |
自动化技术 | 433篇 |
出版年
2023年 | 32篇 |
2022年 | 61篇 |
2021年 | 125篇 |
2020年 | 86篇 |
2019年 | 105篇 |
2018年 | 132篇 |
2017年 | 111篇 |
2016年 | 128篇 |
2015年 | 68篇 |
2014年 | 105篇 |
2013年 | 247篇 |
2012年 | 130篇 |
2011年 | 149篇 |
2010年 | 132篇 |
2009年 | 154篇 |
2008年 | 125篇 |
2007年 | 117篇 |
2006年 | 95篇 |
2005年 | 67篇 |
2004年 | 49篇 |
2003年 | 52篇 |
2002年 | 68篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 53篇 |
1998年 | 69篇 |
1997年 | 56篇 |
1996年 | 56篇 |
1995年 | 41篇 |
1994年 | 39篇 |
1993年 | 36篇 |
1992年 | 36篇 |
1991年 | 33篇 |
1990年 | 18篇 |
1989年 | 33篇 |
1988年 | 33篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 26篇 |
1981年 | 29篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1978年 | 21篇 |
1977年 | 13篇 |
1976年 | 21篇 |
1975年 | 17篇 |
1974年 | 14篇 |
排序方式: 共有3275条查询结果,搜索用时 17 毫秒
1.
2.
Blends of EPDM and chlorobutyl (CIIR) rubbers are used in nuclear plants where they have to withstand the combined effect of radiation and hydrocarbon aging. To improve their mechanical properties as well as hydrocarbon and gamma radiation resistance, the blends are reinforced with 0.5, 1, 1.5, and 2 phr of MWCNT. The increase in mechanical properties was highest for 1.5 phr MWCNT with 69% increase in tensile strength. The improvement in properties was correlated to MWCNT dispersion and filler–polymer interactions, which were confirmed by TEM and FTIR analysis. Hydrocarbon transport coefficients decreased on addition of MWCNT. The nanocomposites were exposed to 0.5, 1, and 2 MGy cumulative doses of gamma radiation. Depending on the radiation dose, crosslinking and/or chain scission occurred causes changes in physical properties. MWCNT reinforcement reduced the magnitude of changes in mechanical and transport properties after γ-irradiation. ESR and FTIR spectra provided qualitative information on free radical formation and chemical changes due to γ-rays exposure. To further enhance the properties, hybrid nanocomposites with 1.5 phr MWCNT and varying nanoclay contents (0.5, 1, 1.5, 2, and 5 phr) were prepared. Due to synergism between MWCNT and nanoclay, the hybrid composites had superior properties with hybrid containing 5 phr nanoclay giving 98% increase in tensile strength. 相似文献
3.
4.
Karishma Tiwari Pulak Sarkar Solagna Modak Harwinder Singh Sumit Kumar Pramanik Santanu Karan Amitava Das 《Advanced materials (Deerfield Beach, Fla.)》2020,32(8):1905621
Separation membranes with higher molecular weight cut-offs are needed to separate ions and small molecules from a mixed feed. The molecular sieving phenomenon can be utilized to separate smaller species with well-defined dimensions from a mixture. Here, the formation of freestanding polyimine nanofilms with thicknesses down to ≈14 nm synthesized via self-assembly of pre-synthesized imine oligomers is reported. Nanofilms are fabricated at the water–xylene interface followed by reversible condensation of polymerization according to the Pieranski theory. Polyimine nanofilm composite membranes are made via transferring the freestanding nanofilm onto ultrafiltration supports. High water permeance of 49.5 L m-2 h−1 bar−1 is achieved with a complete rejection of brilliant blue-R (BBR; molecular weight = 825 g mol−1) and no more than 10% rejection of monovalent and divalent salts. However, for a mixed feed of BBR dye and monovalent salt, the salt rejection is increased to ≈18%. Membranes are also capable of separating small dyes (e.g., methyl orange; MO; molecular weight = 327 g mol−1) from a mixed feed of BBR and MO. Considering a thickness of ≈14 nm and its separation efficiency, the present membrane has significance in separation processes. 相似文献
5.
Metal Science and Heat Treatment - Mechanical properties of copper-alloyed bainitic gray cast iron are studied after isothermal quenching for bainite at different temperatures and holds. The... 相似文献
6.
Microsystem Technologies - This paper represents low power and high speed design issues of Hamming code generation and error detection circuit using complementary metal oxide semiconductor (CMOS)... 相似文献
7.
Sharma Rachit Kumar Sarkar Prabir Singh Harpreet 《Clean Technologies and Environmental Policy》2020,22(6):1269-1284
Clean Technologies and Environmental Policy - Manufacturing organizations are under continuous pressure to implement sustainability in their activities. There is a need to identify the... 相似文献
8.
S. Sarkar P. Mohan Raj S. Chakraborty G. Phanikumar K. Chattopadhyay P. Dutta 《Journal of Materials Science》2003,38(1):155-164
A three dimensional, transient model is developed for studying heat transfer, fluid flow and mass transfer for the case of a single-pass laser surface alloying process. The numerical study is performed in a co-ordinate system fixed to the laser which moves with a constant scanning speed. The coupled momentum, energy and species conservation equations are solved using a finite volume technique. Phase change processes are modelled using a fixed-grid enthalpy-porosity technique, which is capable of predicting the continuously evolving solid-liquid interface. The three-dimensional model is able to predict the species concentration distribution inside the molten pool during alloying, as well as in the entire cross section of the solidified alloy. Corresponding experimental results show a good qualitative agreement with the numerical predictions with regard to pool shape and final composition distribution. 相似文献
9.
Building useful systems with an ability to understand "real" natural language input has long been an elusive goal for Artificial Intelligence. Well-known problems such as ambiguity, indirectness, and incompleteness of natural language inputs have thwarted efforts to build natural language interfaces to intelligent systems. In this article, we report on our work on a model of understanding natural language design specifications of physical devices such as simple electrical circuits. Our system, called KA, solves the classical problems of ambiguity, incompleteness and indirectness by exploiting the knowledge and problem-solving processes in the situation of designing simple physical devices. In addition, KA acquires its knowledge structures (apart from a basic ontology of devices) from the results of its problem-solving processes. Thus, KA can be bootstrapped to understand design specifications and user feedback about new devices using the knowledge structures it acquired from similar devices designed previously.In this paper, we report on three investigations in the KA project. Our first investigation demonstrates that KA can resolve ambiguities in design specifications as well as infer unarticulated requirements using the ontology, the knowledge structures, and the problem-solving processes provided by its design situation. The second investigation shows that KA's problem-solving capabilities help ascertain the relevance of indirect design specifications, and identify unspecified relations between detailed requirements. The third investigation demonstrates the extensibility of KA's theory of natural language understanding by showing that KA can interpret user feedback as well as design requirements. Our results demonstrate that situating language understanding in problem solving, such as device design in KA, provides effective solutions to unresolved problems in natural language processing. 相似文献
10.
Results of scanning electron microscopy (SEM) and energy dispersive X-ray analytical (EDAX) investigations, conducted on some elevated structures displayed by flux grown rare earth orthochromite, RCrO3 (R = La, Yb) crystals, are presented. The peculiar structures exhibited by crystal surfaces indicate imperfections and impurity phases. EDAX of elevated structures reveals the various phases to be composed of lead associated materials which may probably be either Pb2CrO5 or Pb2OF2 (flux). Other secondary crystallization of impurity phases, ROF (R = La, Yb) is illustrated in the case of RCrO3 (R = La, Yb) crystals. The elevated structures illustrate their non-stoichiometric behaviour. Precipitation of impurity phases and formation of imperfections during the growth of RCrO3 (R = La, Yb) crystals and their effect on the crystalline quality is discussed. 相似文献