全文获取类型
收费全文 | 2517篇 |
免费 | 88篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 161篇 |
综合类 | 4篇 |
化学工业 | 927篇 |
金属工艺 | 73篇 |
机械仪表 | 57篇 |
建筑科学 | 72篇 |
矿业工程 | 2篇 |
能源动力 | 96篇 |
轻工业 | 288篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 143篇 |
一般工业技术 | 453篇 |
冶金工业 | 62篇 |
原子能技术 | 63篇 |
自动化技术 | 199篇 |
出版年
2023年 | 8篇 |
2022年 | 28篇 |
2021年 | 57篇 |
2020年 | 33篇 |
2019年 | 35篇 |
2018年 | 48篇 |
2017年 | 43篇 |
2016年 | 62篇 |
2015年 | 38篇 |
2014年 | 84篇 |
2013年 | 157篇 |
2012年 | 119篇 |
2011年 | 174篇 |
2010年 | 100篇 |
2009年 | 144篇 |
2008年 | 143篇 |
2007年 | 133篇 |
2006年 | 99篇 |
2005年 | 114篇 |
2004年 | 98篇 |
2003年 | 89篇 |
2002年 | 89篇 |
2001年 | 61篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 33篇 |
1997年 | 40篇 |
1996年 | 40篇 |
1995年 | 29篇 |
1994年 | 40篇 |
1993年 | 30篇 |
1992年 | 28篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 29篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有2611条查询结果,搜索用时 312 毫秒
121.
The mechanical force to polymeric materials in vacuum at 77 K produces mechano radicals, mechano anions and mechano cations due to homogeneous and heterogeneous scissions of the covalent bonds comprising polymer main chain. The ionic degree of the covalent bond was estimated by calculating the “absolute ΔMulliken atomic charge,” which was defined as the difference between the Mulliken atomic charges of the two adjacent atoms comprising the covalent bond of the polymer main chain. The ionic yield of the covalent bond increased with increasing the absolute ΔMulliken atomic charge. The empirical formula for the ionic yield was obtained with the absolute ΔMulliken atomic charge, and indicates that the ionic yield could be estimated from its chemical structure. 相似文献
122.
Takeshi Kikutani J. Radhakrishnan Sadaaki Arikawa Akira Takaku Norimasa Okui Xia Jin Fumio Niwa Yosuke Kudo 《应用聚合物科学杂志》1996,62(11):1913-1924
High-speed bicomponent spinning of poly(ethylene terephthalate)(PET)(core) and poly-propylene (PP) (sheath) was carried out and the structure development in the individual components, PET and PP, was investigated. The orientation and crystallinity development in the PET component was enhanced as compared to that of the single-component spinning while the PP component remained in a low orientation state and had a pseudohexagonal crystal structure even at high take-up speeds. To clarify the mutual interaction between the two components in bicomponent spinning, a semiquantitative numerical simulation was performed. The simulation results obtained using the Newtonian fluid model showed that the solidification stress in the PET component was enhanced while that of the PP component was decreased in comparison with the corresponding single-component spinning. This is due to the difference in the temperature dependence of their elongational viscosity. Simulation with an upper-convected Maxwell model as the constitutive equation suggested that significant stress relaxation of the PP component can occur in the spinline if the PET component solidifies earlier than does PP. Based on the structural characterization results, and the simulation results, it was concluded that the difference in the activation energy of the elongational viscosity and solidification temperature between the two polymers are the main factors influencing the mutual interaction in the bicomponent spinning process. © 1996 John Wiley & Sons, Inc. 相似文献
123.
Ninomiya Yuma Sasaki Hideaki Yoshikawa Takeshi Maeda Masafumi 《Metallurgical and Materials Transactions B》2019,50(1):407-415
Metallurgical and Materials Transactions B - The dissolution and passivation of pure Cu and Cu-5 wt pct Ag anodes in H2SO4-CuSO4 electrolyte were investigated by a direct... 相似文献
124.
Makino SI Kawamoto K Takeshi K Okada Y Yamasaki M Yamamoto S Igimi S 《International journal of food microbiology》2005,104(2):189-196
Food-borne outbreaks caused by Listeria monocytogenes have been recognized in US and European countries. Only sporadic cases, of neonatal listeriosis, have been reported in Japan. Since L. monocytogenes has been often isolated from foods in Japan, food-borne outbreaks potentially could have occurred. In February 2001, L. monocytogenes serotype 1/2b was isolated from a washed-type cheese during routine Listeria monitoring of 123 domestic cheeses. Further samples from products and the environments at the plant that produced the contaminated cheese were examined for L. monocytogenes. L. monocytogenes serotype 1/2b was detected in 15 cheese samples, at most probable number that ranged from <30 to 4.6 x 10(9)/100 g, and in environmental samples. Studies with people who had consumed cheese from the plant revealed 86 persons who had been infected with L. monocytogenes. Thirty-eight of those people had developed clinical symptoms of gastroenteritis or the common cold type after the consumption of cheese. Isolates from those patients exhibited the same serotype, pathogenicity for mice and HeLa cells, DNA fingerprinting patterns and PCR amplification patterns. From the epidemiological and genetic evidence, it appeared that the outbreak was caused by cheese. This is the first documented incidence of food-borne listeriosis in Japan. 相似文献
125.
Natsuko Goda Kana Shimizu Yohta Kuwahara Takeshi Tenno Tamotsu Noguchi Takahisa Ikegami Motonori Ota Hidekazu Hiroaki 《International journal of molecular sciences》2015,16(7):15743-15760
Intrinsically disordered proteins (IDPs) that lack stable conformations and are highly flexible have attracted the attention of biologists. Therefore, the development of a systematic method to identify polypeptide regions that are unstructured in solution is important. We have designed an “indirect/reflected” detection system for evaluating the physicochemical properties of IDPs using nuclear magnetic resonance (NMR). This approach employs a “chimeric membrane protein”-based method using the thermostable membrane protein PH0471. This protein contains two domains, a transmembrane helical region and a C-terminal OB (oligonucleotide/oligosaccharide binding)-fold domain (named NfeDC domain), connected by a flexible linker. NMR signals of the OB-fold domain of detergent-solubilized PH0471 are observed because of the flexibility of the linker region. In this study, the linker region was substituted with target IDPs. Fifty-three candidates were selected using the prediction tool POODLE and 35 expression vectors were constructed. Subsequently, we obtained 15N-labeled chimeric PH0471 proteins with 25 IDPs as linkers. The NMR spectra allowed us to classify IDPs into three categories: flexible, moderately flexible, and inflexible. The inflexible IDPs contain membrane-associating or aggregation-prone sequences. This is the first attempt to use an indirect/reflected NMR method to evaluate IDPs and can verify the predictions derived from our computational tools. 相似文献
126.
采用了微量润滑技术的钻削在长距或小孔径的条件下有必要对所供给的油雾和压缩空气进行最佳化分析.本文首先对切削变形与切削热分布的总能量进行了分析,并在把普通钻削过程中油雾假设为稳态可压缩绝热紊流状态的假设条件下,通过分析得到油膜厚度、气流速度、压缩空气温度和刀具平均温度等重要影响参数的相互关系.最后,给出微量润滑钻削条件下,切削过程中所需的油膜和压缩空气的最佳容量. 相似文献
127.
Osteocytes connect with neighboring osteocytes and osteoblasts through their processes and form an osteocyte network. Shear stress on osteocytes, which is induced by fluid flow in the lacunae and canaliculi, has been proposed as an important mechanism for mechanoresponses. The lacunocanalicular structure is differentially developed in the compression and tension sides of femoral cortical bone and the compression side is more organized and has denser and thinner canaliculi. Mice with an impaired lacunocanalicular structure may be useful for evaluation of the relationship between lacunocanalicular structure and mechanoresponses, although their bone component cells are not normal. We show three examples of mice with an impaired lacunocanalicular structure. Ablation of osteocytes by diphtheria toxin caused massive osteocyte apoptosis, necrosis or secondary necrosis that occurred after apoptosis. Osteoblast-specific Bcl2 transgenic mice were found to have a reduced number of osteocyte processes and canaliculi, which caused massive osteocyte apoptosis and a completely interrupted lacunocanalicular network. Osteoblast-specific Sp7 transgenic mice were also revealed to have a reduced number of osteocyte processes and canaliculi, as well as an impaired, but functionally connected, lacunocanalicular network. Here, we show the phenotypes of these mice in physiological and unloaded conditions and deduce the relationship between lacunocanalicular structure and mechanoresponses. 相似文献
128.
Hideki Shige Toshitsugu Ishikawa Michio Suzukawa Masato Nishiwaki Takeshi Yamashita Kei Nakajima Toshimitsu Ito Kenji Higashi Makoto Ayaori Atsushi Yonemura Paul Nestel Haruo Nakamura 《Lipids》1998,33(12):1169-1175
The effects of vitamin E on cholesteryl ester (CE) metabolism in 1774 cells were examined. Pretreatment of 1774 cells with
vitamin E at concentrations above 50 μM significantly decreased acetylated low density lipoprotein (LDL)-induced incorporation
of [14C]oleate into CF in cells in a dose-dependent manner. This was partly due to vitamin E Also significantly inhibiting the uptake
of [3H]CE-labeled acetylated LDL by 1774 cells. A trend existed toward suppression of acyl-CoA:cholesterol acyltransferase (ACAT)
activity in the cell lysate at high vitamin E concentration, but there was no effect on hydrolysis of CE. These data indicate
that vitamin E reduces the uptake of modified LDL and suppresses ACAT activity, resulting in less cholesterol esterification
in macrophages; a novel mechanism underlying the antiatherogenic properties of vitamin E. 相似文献
129.
Abnormalities in the Metabolism of Fatty Acids and Triacylglycerols in the Liver of the Goto-Kakizaki Rat: A Model for Non-Obese Type 2 Diabetes
下载免费PDF全文
![点击此处可从《Lipids》网站下载免费的PDF全文](/ch/ext_images/free.gif)
130.
We previously reported that a copolymer consisting of N-isopropylacrylamide (NIPAM) and benzophenone (BP) units, behaves as a photosensitizer showing temperature-controlled oxygenation activity in water (J. Am. Chem. Soc.2006, 128, 8751). This polymer shows a heat-induced oxygenation enhancement at low temperature region (5-20 °C), while showing a heat-induced oxygenation suppression at high temperature region (20-60 °C), resulting in an off-on-off activity profile against the temperature window. This is driven by a heat-induced phase transition of the polymer from coil to micelle and then to globule states. In the present work, effects of adding an amine component (N-[3-(dimethylamino)propyl]acrylamide: DMAPAM) to the polymer on the sensitization activity were studied, where the relationship between the phase transition behavior and the activity was clarified by several spectroscopic analyses. The polymers, poly(NIPAMx-co-BPy-co-DMAPAMz), show activity controlled by temperature and pH. The off-on-off activity profile shifts to higher temperature with a pH decrease. This is because protonation of the DMAPAM units leads to an increase in the polymer polarity and, hence, the polymer aggregates at higher temperature. In addition, increase in the DMAPAM content of the polymer leads to further shift of the activity profile. In contrast, at pH < 8, no activity enhancement is observed because complete protonation of the DMAPAM units suppresses polymer aggregation. 相似文献