全文获取类型
收费全文 | 6023篇 |
免费 | 189篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 337篇 |
综合类 | 17篇 |
化学工业 | 1488篇 |
金属工艺 | 166篇 |
机械仪表 | 121篇 |
建筑科学 | 114篇 |
矿业工程 | 2篇 |
能源动力 | 254篇 |
轻工业 | 529篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 533篇 |
一般工业技术 | 1048篇 |
冶金工业 | 1003篇 |
原子能技术 | 119篇 |
自动化技术 | 482篇 |
出版年
2023年 | 32篇 |
2022年 | 66篇 |
2021年 | 112篇 |
2020年 | 54篇 |
2019年 | 64篇 |
2018年 | 94篇 |
2017年 | 83篇 |
2016年 | 101篇 |
2015年 | 85篇 |
2014年 | 163篇 |
2013年 | 342篇 |
2012年 | 243篇 |
2011年 | 332篇 |
2010年 | 249篇 |
2009年 | 277篇 |
2008年 | 299篇 |
2007年 | 253篇 |
2006年 | 221篇 |
2005年 | 228篇 |
2004年 | 184篇 |
2003年 | 190篇 |
2002年 | 172篇 |
2001年 | 141篇 |
2000年 | 118篇 |
1999年 | 124篇 |
1998年 | 401篇 |
1997年 | 247篇 |
1996年 | 171篇 |
1995年 | 127篇 |
1994年 | 138篇 |
1993年 | 112篇 |
1992年 | 62篇 |
1991年 | 56篇 |
1990年 | 48篇 |
1989年 | 67篇 |
1988年 | 46篇 |
1987年 | 39篇 |
1986年 | 39篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 48篇 |
1982年 | 33篇 |
1981年 | 34篇 |
1980年 | 26篇 |
1979年 | 29篇 |
1978年 | 32篇 |
1977年 | 36篇 |
1976年 | 56篇 |
1975年 | 15篇 |
1974年 | 16篇 |
排序方式: 共有6227条查询结果,搜索用时 15 毫秒
951.
952.
Kaori Takemura Rina Watanabe Ryuji Kameishi Naoya Sakaguchi Hiroyuki Kamachi Atsushi Kume Ichirou Karahara Yuko T. Hanba Tomomichi Fujita 《Microgravity science and technology》2017,29(6):467-473
The photosynthetic and anatomical responses of bryophytes to changes in gravity will provide crucial information for estimating how these plant traits evolved to adapt to changes in gravity in land plant history. We performed long-term hypergravity experiments at 10g for 4 and 8 weeks using the moss Physcomitrella patens with two centrifuges equipped with lighting systems that enable long-term plant growth under hypergravity with irradiance. The aims of this study are (1) to quantify changes in the anatomy and morphology of P. patens, and (2) to analyze the post-effects of hypergravity on photosynthesis by P. patens in relation to these changes. We measured photosynthesis by P. patens for a population of gametophores (e.g., canopy) in Petri dishes and plant culture boxes. Gametophore numbers increased by 9% for a canopy of P. patens, with 24–27% increases in chloroplast sizes (diameter and thickness) in leaf cells. In a canopy of P. patens, the area-based photosynthesis rate (A canopy) was increased by 57% at 10g. The increase observed in A canopy was associated with greater plant numbers and chloroplast sizes, both of which involved enhanced CO2 diffusion from the atmosphere to chloroplasts in the canopies of P. patens. These results suggest that changes in gravity are important environmental stimuli to induce changes in plant growth and photosynthesis by P. patens, in which an alteration in chloroplast size is one of the key traits. We are now planning an ISS experiment to investigate the responses of P. patens to microgravity. 相似文献
953.
Hua‐Jun Qiu Peng Du Kailong Hu Jiaojiao Gao Huanglong Li Pan Liu Toshiaki Ina Koji Ohara Yoshikazu Ito Mingwei Chen 《Advanced materials (Deerfield Beach, Fla.)》2019,31(19)
Developing bifunctional electrocatalysts with high activities and long durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial toward the practical implementation of rechargeable metal–air batteries. Here, a 3D nanoporous graphene (np‐graphene) doped with both N and Ni single atoms/clusters is reported. The predoping of N by chemical vapor deposition (CVD) dramatically increases the Ni doping amount and stability. The resulting N and Ni codoped np‐graphene has excellent electrocatalytic activities for both the ORR and the OER in alkaline aqueous solutions. The synergetic effects of N and Ni dopants are revealed by density functional theory calculations. The free‐standing Ni,N codoped 3D np‐graphene shows great potential as an economical catalyst/electrode for metal–air batteries. 相似文献
954.
N. Inoue D. Ito Y. Hold-Geoffroy L. Mai B. Price T. Yamasaki 《Computer Graphics Forum》2020,39(2):451-462
We present RGB2AO, a novel task to generate ambient occlusion (AO) from a single RGB image instead of screen space buffers such as depth and normal. RGB2AO produces a new image filter that creates a non-directional shading effect that darkens enclosed and sheltered areas. RGB2AO aims to enhance two 2D image editing applications: image composition and geometry-aware contrast enhancement. We first collect a synthetic dataset consisting of pairs of RGB images and AO maps. Subsequently, we propose a model for RGB2AO by supervised learning of a convolutional neural network (CNN), considering 3D geometry of the input image. Experimental results quantitatively and qualitatively demonstrate the effectiveness of our model. 相似文献
955.
Makoto Ito Nam Ho Kim Nozomu Kogiso 《Structural and Multidisciplinary Optimization》2018,57(5):1919-1935
In this paper, a simple but efficient concept of epistemic reliability index (ERI) is introduced for sampling uncertainty in input random variables under conditions where the input variables are independent Gaussian, and samples are unbiased. The increased uncertainty due to the added epistemic uncertainty requires a higher level of target reliability, which is called the conservative reliability index (CRI). In this paper, it is assumed that CRI can additively be decomposed into the aleatory part (the target reliability index) and the epistemic part (the ERI). It is shown theoretically and numerically that ERI remains same for different designs, which is critically important for computational efficiency in reliability-based design optimization. Novel features of the proposed ERI include: (a) it is unnecessary to have a double-loop uncertainty quantification for handling both aleatory and epistemic uncertainty; (b) the effect of two different sources of uncertainty can be separated so that designers can better understand the optimization outcome; and (c) the ERI needs to be calculated once and remains the same throughout the design process. The proposed method is demonstrated with two analytical and one numerical examples. 相似文献
956.
Makoto Ishiguro Nobuhiko Ichihara Yujiro Yanai Michio Nagai Katsuyuki Takada Yoichi Suga Yoji Ito 《Journal of the Society for Information Display》2018,26(4):208-213
We have successfully developed a cosmetic film with polymerized cholesteric material. The film features a variety of colors by helical pitch gradients, diffusive texture, and arbitrary color patterns. It hides the display when turned off, and transmits display images when turned on. We believe it could change the display in the OFF‐state from the conventional black wall to specially designed decorations. In addition, they can be applied to hidden sensors. 相似文献
957.
Kailong Hu Tingting Yu Yanyi Zhang Xiaorong Lin Yilu Zhao Guoqiang Xie Xingjun Liu Xi Lin Jun-ichi Fujita Hua-Jun Qiu Yoshikazu Ito 《Advanced functional materials》2021,31(38):2103632
Catalyzing oxygen reduction reaction (ORR) and accelerating oxygen diffusion are two key challenges for the requirements of the cathode catalysts in the metal-air batteries. A promising strategy for improving both ORR performance and mass diffusion simultaneously is to build carbon-based catalysts with ORR-active chemical dopants and 3D interconnected porosity. Herein, a 3D nanoporous N-doped carbon with bicontinuous porosity and interconnected open-pore channels is reported, which is prepared by a polyaniline-assisted template method. The polyaniline can efficiently inhibit the surface diffusion-caused template coarsening, achieving a small pore size of 35 nm. The small porous morphology gives rise to a high N-dopant concentration up to 7.20 at.%, which in turn exhibits a commercial Pt/C-comparable ORR performance together with satisfied durability in alkaline media. Using these nanoporous carbon catalysts as air electrodes, an all-solid-state flexible Al-air battery is assembled with the measured maximum power density reaching 130.5 mW cm−2, as compared to 106.2 mW cm−2 when the commercial Pt/C standard is used. This study provides an efficient method to synthesize 3D N-doped carbon with bicontinuous nano-sized pore channels for wide-ranging applications in portable and flexible devices. 相似文献
958.
It has been found that tack values of pressure-sensitive adhesives are dependent on the surface energies for adherends. The parabolic curves with maxima are obtained from the plots of tack values versus critical surface tensions for the substrates. The maximum occurs at the region where the two surface tensions are almost similar. On the other hand, tack is measured as a dynamic value indicated as the force necessary to deform the adhesive mass. To explain why the tack values is controlled by the surface character of the adherend, a mechanism is proposed for adhesive bond breaking. Primarily, bonding occurs by wetting the surface with adhesive. When the adhesive bond breaks by external force, unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface of the adherend. As the total area of wetted spots is determined by surface energy, the tack value is dependent on the critical surface tension of the adherend. 相似文献
959.
Hiroyuki Shimasaki O. S. Privett Ichiro Hara 《Journal of the American Oil Chemists' Society》1977,54(3):119-123
The formation of fluorescent products in the reaction of methyl linoleate hydroperoxide with glycine in aqueous emulsions
correlated directly with the decrease in diene conjugation and the increase in thiobarbituric acid (TBA) reactive substances.
These correlations also were reflected in the course of the oxidation of methyl linoleate in aqueous emulsions with glycine
and indicated that glycine reacted with products of peroxide decomposition as opposed to intermediates of autoxidation in
hydroperoxide formation. Thin layer chromatography (TLC) and selective solvent extraction demonstrated that the products of
the reaction contained many substances with a fluorescent spectrum similar to those of lipofuscin pigments. When methyl esters
of polyunsaturated fatty acids or other polyunsaturated lipids underwent oxidation adsorbed on silica gel particles, products
with similar fluorescent spectral properties were formed illustrating that fluorescent substances were formed in a variety
of reactions associated with the oxidation of unsaturated lipids. 相似文献
960.
Seiichi Suda Koichi Kawahara Mitsunobu Kawano Hiroyuki Yoshida Toru Inagaki 《Journal of the American Ceramic Society》2007,90(4):1094-1100
Matrix-type nickel oxide (NiO)/samarium-doped ceria (SDC) composite particles, in which NiO and SDC nano-particles were homogeneously dispersed, were synthesized by spray pyrolysis (SP) for an anode precursor of intermediate-temperature solid oxide fuel cells (IT-SOFCs). SP of an aqueous solution containing Ni, Ce, and Sm salts resulted in capsule-type composite particles that had NiO enveloped with SDC. The capsule-type composite particles actually prevent Ni aggregation between particles, but they cannot have a large contact area between nickel (Ni) and SDC. A matrix-type composite particle is expected to have a large contact area because the matrix-type composite is comprised of nanometer-sized Ni and SDC particles. An adequate addition of ethylene glycol successfully resulted in matrix-type NiO/SDC composite particles. The matrix-type composite particles also showed higher anode performance than the capsule-type composite particles in these experiments and they were effective as precursors of high-performance IT-SOFC anodes. 相似文献