全文获取类型
收费全文 | 3761篇 |
免费 | 72篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 224篇 |
综合类 | 5篇 |
化学工业 | 1137篇 |
金属工艺 | 119篇 |
机械仪表 | 118篇 |
建筑科学 | 98篇 |
能源动力 | 153篇 |
轻工业 | 256篇 |
水利工程 | 8篇 |
石油天然气 | 3篇 |
无线电 | 191篇 |
一般工业技术 | 835篇 |
冶金工业 | 253篇 |
原子能技术 | 129篇 |
自动化技术 | 323篇 |
出版年
2023年 | 18篇 |
2022年 | 50篇 |
2021年 | 65篇 |
2020年 | 32篇 |
2019年 | 40篇 |
2018年 | 54篇 |
2017年 | 53篇 |
2016年 | 68篇 |
2015年 | 55篇 |
2014年 | 83篇 |
2013年 | 185篇 |
2012年 | 122篇 |
2011年 | 228篇 |
2010年 | 171篇 |
2009年 | 174篇 |
2008年 | 198篇 |
2007年 | 139篇 |
2006年 | 154篇 |
2005年 | 139篇 |
2004年 | 107篇 |
2003年 | 131篇 |
2002年 | 97篇 |
2001年 | 69篇 |
2000年 | 77篇 |
1999年 | 78篇 |
1998年 | 140篇 |
1997年 | 114篇 |
1996年 | 97篇 |
1995年 | 60篇 |
1994年 | 55篇 |
1993年 | 66篇 |
1992年 | 35篇 |
1991年 | 39篇 |
1990年 | 42篇 |
1989年 | 54篇 |
1988年 | 39篇 |
1987年 | 41篇 |
1986年 | 63篇 |
1985年 | 47篇 |
1984年 | 61篇 |
1983年 | 55篇 |
1982年 | 39篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 38篇 |
1978年 | 27篇 |
1977年 | 24篇 |
1976年 | 18篇 |
1974年 | 14篇 |
1973年 | 10篇 |
排序方式: 共有3852条查询结果,搜索用时 15 毫秒
81.
In this paper, we introduce a probabilistic distribution, called a smooth distribution, which is a generalization of variants of the uniform distribution such as q-bounded distribution and product distribution. Then, we give an algorithm that, under the smooth distribution, properly learns the class of functions of k terms given as
k
kn={g(f1(v), …, fk(v)) | g
k, f1, …, fk
n} in polynomial time for constant k, where
k is the class of all Boolean functions of k variables and
n is the class of terms over n variables. Although class
k
kn was shown by Blum and Singh to be learned using DNF as the hypothesis class, it has remained open whether it is properly learnable under a distribution-free setting. 相似文献
82.
Takuma Torii Tomio Kamada Kiyoshi Izumi Kenta Yamada 《Artificial Life and Robotics》2017,22(3):301-307
Artificial market simulations have the potential to be a strong tool for studying rapid and large market fluctuations and designing financial regulations. High-frequency traders, that exchange multiple assets simultaneously within a millisecond, are said to be a cause of rapid and large market fluctuations. For such a large-scale problem, this paper proposes a software or computing platform for large-scale and high-frequency artificial market simulations (Plham: /pl\(\Lambda\)m). The computing platform, Plham, enables modeling financial markets composed of various brands of assets and a large number of agents trading on a short timescale. The design feature of Plham is the separation of artificial market models (simulation models) from their execution (execution models). This allows users to define their simulation models without parallel computing expertise and to choose one of the execution models they need. This computing platform provides a prototype execution model for parallel simulations, which exploits the variety in trading frequency among traders, that is, the fact that some traders do not require up-to-date information of markets changing in millisecond order. We evaluated a prototype implementation on the K computer using up to 256 computing nodes. 相似文献
83.
84.
Bioaccumulation, temporal trend, and geographical distribution of synthetic musks in the marine environment 总被引:3,自引:0,他引:3
Nakata H Sasaki H Takemura A Yoshioka M Tanabe S Kannan K 《Environmental science & technology》2007,41(7):2216-2222
Bioaccumulation of synthetic musks in a marine food chain was investigated by analyzing marine organisms at various trophic levels, including lugworm, clam, crustacean, fish, marine mammal, and bird samples collected from tidal flat and shallow water areas of the Ariake Sea, Japan. Two of the polycyclic musks, HHCB and AHTN, were the dominant compounds found in most of the samples analyzed, whereas nitro musks were not detected in any of the organisms, suggesting greater usage of polycyclic musks relative to the nitro musks in Japan. The highest concentrations of HHCB were detected in clams (258-2730 ng/g lipid wt.), whereas HHCB concentrations in mallard and black-headed gull were low, and comparable with concentrations in fish and crab. These results are in contrast to the bioaccumulation pattern of polychlorinated biphenyls; for which a positive correlation between the concentration and the trophic status of organisms was found. Such a difference in the bioaccumulation is probably due to the metabolism and elimination of HHCB in higher trophic organisms. Temporal trends in concentrations of synthetic musks were examined by analyzing tissues of marine mammals from Japanese coastal waters collected during 1977-2005. HHCB concentrations in marine mammals have shown significant increase since the early 1990s, suggesting a continuous input of this compound into the marine environment. Comparison of the time trend for HHCB with those for PCBs and PBDEs suggested that the rates of increase in HHCB concentrations were higher than the other classes of pollutants. To examine the geographical distribution of HHCB, we have analyzed tissues of fish, marine mammals, and birds collected from several locations. Synthetic musks were not detected in a sperm whale (pelagic species) from Japanese coastal water and in eggs of south polar skua from Antarctica. While the number of samples analyzed is limited, these results imply a lack of long-range transportation potential of synthetic musks in the environment. 相似文献
85.
Design of a photocatalyst for bromate decomposition: surface modification of TiO2 by pseudo-boehmite
The rate of BrO3- reduction by a commercial TiO2 photocatalyst under UV illumination in an aqueous solution was increased by lowering the pH from 7 to 5. The effect is attributable to an enhancement of the electrical interaction between BrO3- and the positively charged surfaces of the TiO2 photocatalyst. The surface charge can be controlled by a surface modification of the TiO2 photocatalyst without controlling the pH of the water. In fact, the isoelectric point of surface-modified TiO2 was higher than that of the unloaded TiO2 photocatalyst, resulting in an increase in the rate of the photocatalytic reduction of BrO3- at a neutral pH. This increase is explained by an increase in the amount of adsorbed BrO3- on the photocatalyst surface. 相似文献
86.
Maeda-Yamamoto M Saito T Nesumi A Tokuda Y Ema K Honma D Ogino A Monobe M Murakami A Murakami A Tachibana H 《Journal of the science of food and agriculture》2012,92(11):2379-2386
BACKGROUND: The purpose of this study was to evaluate the effects of leaf order or crop season on anthocyanins and other chemicals in the anthocyanin‐rich tea cultivar ‘Sunrouge’ (Camellia sinensis x C. taliensis) by using high‐performance liquid chromatography, and to study the effect of ‘Sunrouge’ extract on acetylcholinesterase (AChE) activity in human neuroblastoma SK‐N‐SH cells. RESULTS: The total anthocyanin content was higher in the third (3.09 mg g?1) than in the second (2.24 mg g?1) or first crop season (1.79 mg g?1). The amount of anthocyanins contained in the stem was high (1.61 mg g?1). In the third crop season, the concentrations of delphinidin‐3‐O‐β‐D ‐(6‐(E)‐p‐coumaroyl)galactopyranoside (DCGa), cyanidin‐3‐O‐β‐D ‐(6‐(E)‐p‐coumaroyl)galactopyranoside, delphinidin‐3‐O‐β‐D ‐galactopyranoside, delphinidin‐3‐O‐β‐D ‐(6‐O‐(Z)‐p‐coumaroyl)galactopyranoside, cyanidin‐3‐O‐β‐D ‐galactoside, and delphinidin‐3‐O‐β‐D ‐glucoside were 1.57 mg g?1, 0.52 mg g?1, 0.40 mg g?1, 0.22 mg g?1, 0.14 mg g?1, and 0.11 mg g?1, respectively. DCGa accounted for about 50% of the anthocyanins present. The suppressive effect of ‘Sunrouge’ water extract on AChE activity in human neuroblastoma SK‐N‐SH cells was the strongest among the three tea cultivars (‘Sunrouge’, ‘Yabukita’ and ‘Benifuuki’). CONCLUSION: These results suggested that ‘Sunrouge’ might protect humans from humans from AChE‐related diseases by suppressing AChE activity. To obtain sufficient amounts of anthocyanins, catechins and/or caffeine for a functional food material, ‘Sunrouge’ from the third crop season should be used. Copyright © 2012 Society of Chemical Industry 相似文献
87.
88.
89.
Akira Inoue 《国际自动化与计算杂志》2010,7(2):213-218
In this paper, robust stability of nonlinear plants represented by non-symmetric Prandtl-Ishlinskii (PI) hysteresis model is studied. In general, PI hysteresis model is the weighted superposition of play or stop hysteresis operators, and the slopes of the operators are considered to be the same. In order to make a hysteresis model, a modified form of non-symmetric play hysteresis operator with unknown slopes is given. The hysteresis model is described by a generalized Lipschitz operator term and a bounded parasitic term. Since the generalized Lipschitz operator is unknown, a new condition using robust right coprime factorization is proposed to guarantee robust stability of the controlled plant with the hysteresis nonlinearity. As a result, based on the proposed robust condition, a stabilized plant is obtained. A numerical example is presented to validate the effectiveness of the proposed method. 相似文献
90.
Lianqi Zhang Hideyuki Noguchi Decheng Li Takahisa Muta Xiaoqing Wang Masaki Yoshio Izumi Taniguchi 《Journal of power sources》2008
On the basis of extreme similarity between the triangle phase diagrams of LiNiO2–LiTiO2–Li[Li1/3Ti2/3]O2 and LiNiO2–LiMnO2–Li[Li1/3Mn2/3]O2, new Li–Ni–Ti–O series with a nominal composition of Li1+z/3Ni1/2−z/2Ti1/2+z/6O2 (0 ≤ z ≤ 0.5) was designed and attempted to prepare via a spray-drying method. XRD identified that new Li–Ni–Ti–O compounds had cubic rocksalt structure, in which Li, Ni and Ti were evenly distributed on the octahedral sites in cubic closely packed lattice of oxygen ions. They can be considered as the solid solution between cubic LiNi1/2Ti1/2O2 and Li[Li1/3Ti2/3]O2 (high temperature form). Charge–discharge tests showed that Li–Ni–Ti–O compounds with appropriate compositions could display a considerable capacity (more than 80 mAh g−1 for 0.2 ≤ z ≤ 0.27) at room temperature in the voltage range of 4.5–2.5 V and good electrochemical properties within respect to capacity (more than 150 mAh g−1 for 0 ≤ z ≤ 0.27), cycleability and rate capability at an elevated temperature of 50 °C. These suggest that the disordered cubic structure in some cases may function as a good host structure for intercalation/deintercalation of Li+. A preliminary electrochemical comparison between Li1+z/3Ni1/2−z/2Ti1/2+z/6O2 (0 ≤ z ≤ 0.5) and Li6/5Ni2/5Ti2/5O2 indicated that charge–discharge mechanism based on Ni redox at the voltage of >3.0 V behaved somewhat differently, that is, Ni could be reduced to +2 in Li1+z/3Ni1/2−z/2Ti1/2+z/6O2 while +3 in Li6/5Ni2/5Ti2/5O2. Reduction of Ti4+ at a plateau of around 2.3 V could be clearly detected in Li1+z/3Ni1/2−z/2Ti1/2+z/6O2 with 0.27 ≤ z ≤ 0.5 at 50 °C after a deep charge associated with charge compensation from oxygen ion during initial cycle. 相似文献