全文获取类型
收费全文 | 4150篇 |
免费 | 100篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 216篇 |
综合类 | 5篇 |
化学工业 | 1271篇 |
金属工艺 | 116篇 |
机械仪表 | 128篇 |
建筑科学 | 117篇 |
能源动力 | 161篇 |
轻工业 | 246篇 |
水利工程 | 8篇 |
石油天然气 | 3篇 |
无线电 | 295篇 |
一般工业技术 | 902篇 |
冶金工业 | 358篇 |
原子能技术 | 145篇 |
自动化技术 | 302篇 |
出版年
2023年 | 23篇 |
2022年 | 56篇 |
2021年 | 57篇 |
2020年 | 28篇 |
2019年 | 35篇 |
2018年 | 64篇 |
2017年 | 53篇 |
2016年 | 73篇 |
2015年 | 66篇 |
2014年 | 82篇 |
2013年 | 201篇 |
2012年 | 130篇 |
2011年 | 228篇 |
2010年 | 173篇 |
2009年 | 188篇 |
2008年 | 216篇 |
2007年 | 155篇 |
2006年 | 166篇 |
2005年 | 158篇 |
2004年 | 113篇 |
2003年 | 153篇 |
2002年 | 115篇 |
2001年 | 88篇 |
2000年 | 103篇 |
1999年 | 86篇 |
1998年 | 169篇 |
1997年 | 142篇 |
1996年 | 105篇 |
1995年 | 72篇 |
1994年 | 64篇 |
1993年 | 75篇 |
1992年 | 55篇 |
1991年 | 44篇 |
1990年 | 45篇 |
1989年 | 66篇 |
1988年 | 46篇 |
1987年 | 44篇 |
1986年 | 62篇 |
1985年 | 65篇 |
1984年 | 72篇 |
1983年 | 60篇 |
1982年 | 42篇 |
1981年 | 40篇 |
1980年 | 31篇 |
1979年 | 32篇 |
1978年 | 24篇 |
1977年 | 26篇 |
1976年 | 18篇 |
1974年 | 19篇 |
1973年 | 12篇 |
排序方式: 共有4273条查询结果,搜索用时 15 毫秒
1.
Akira Minami Yuuki Kurebayashi Tadanobu Takahashi Tadamune Otsubo Kiyoshi Ikeda Takashi Suzuki 《International journal of molecular sciences》2021,22(6)
Sialidase cleaves sialic acid residues from glycans such as glycoproteins and glycolipids. In the brain, desorption of the sialic acid by sialidase is essential for synaptic plasticity, learning and memory and synaptic transmission. BTP3-Neu5Ac has been developed for sensitive imaging of sialidase enzyme activity in mammalian tissues. Sialidase activity in the rat hippocampus detected with BTP3-Neu5Ac increases rapidly by neuronal depolarization. It is presumed that an increased sialidase activity in conjunction with neural excitation is involved in the formation of the neural circuit for memory. Since sialidase inhibits the exocytosis of the excitatory neurotransmitter glutamate, the increased sialidase activity by neural excitation might play a role in the negative feedback mechanism against the glutamate release. Mammalian tissues other than the brain have also been stained with BTP3-Neu5Ac. On the basis of information on the sialidase activity imaging in the pancreas, it was found that sialidase inhibitor can be used as an anti-diabetic drug that can avoid hypoglycemia, a serious side effect of insulin secretagogues. In this review, we discuss the role of sialidase in the brain as well as in the pancreas and skin, as revealed by using a sialidase activity imaging probe. We also present the detection of influenza virus with BTP3-Neu5Ac and modification of BTP3-Neu5Ac. 相似文献
2.
Akira Yamamoto Kentaro Teramura Saburo Hosokawa Tsunehiro Tanaka 《Science and Technology of Advanced Materials》2015,16(2)
The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. 相似文献
3.
4.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature
下载免费PDF全文
![点击此处可从《European Journal of Lipid Science and Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
5.
Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges related to energy needs and environmental pollution. Photocatalytic particles need to be in contact with their respective media to exhibit efficient photocatalytic performances. However, it is difficult to separate nanometer-sized photocatalytic materials from reaction media later, which may lead to secondary pollution and a poor recycling performance. Hydrogel photocatalysts with a three-dimensional (3D) network structures are promising support materials for photocatalysts based on features such as high specific surface areas and adsorption capacities and good environmental compatibility. In this review, hydrogel photocatalysts are classified into two different categories depending on their elemental composition and recent progresses in the methods for preparing hydrogel photocatalysts are summarized. Moreover, current applications of hydrogel photocatalysts in energy conversion and environmental remediation are reviewed. Furthermore, a comprehensive outlook and highlight future challenges in the development of hydrogel photocatalysts are presented. 相似文献
6.
Suchapa Netpradit Suda Kiatkamjornwong Yujiro Ando Takeshi Ikeda 《Particulate Science and Technology》1998,16(4):311-327
We investigated the dependence of the toner charge-to-mass ratio (q/m) in a two-component electrophotographic developer on the shaking time, toner concentration (T/C), carrier sizes, and the carrier core and the coating materials, as well as the resulting print qualities in terms of print density, background density, tone reproduction, resolution, and dot gain. Four different sizes of spherical ferrite carriers, four different carrier coating materials, and an irregular iron carrier were used with two types of toner: 14 um red toner (NP-4080) and 8 um cyan toner (CLC-500). The q/m measurement by the blow-off method showed that the red toner charge was positive while the cyan toner charge was negative with these carriers. The toner q/m values, which depended on the shaking time and decreased with the increasing T/C were much more affected by the larger carrier and the smaller toner. The carriers which yielded charges in the proper range produced better print qualities than did the other carriers that yielded a toner q/m 相似文献
7.
A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitatite disaturated species
of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted
by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential
refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC.
The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chroamtograms obtained by
RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responsed in the same degree for different, authentic standards
of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human
lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those
reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis
among the molecular species containing disaturated species. 相似文献
8.
本文论述一种厚/薄铜复合PWB(及其可靠性),它允许PWB设计者在厚铜和薄铜之间以任何希望的图形进行随意选择,以使电源模块/分配电路可以和精细图形特征一起集成,从而适应离I/O数半导体封装的要求。 相似文献
9.
Wakejima A. Matsunaga K. Okamoto Y. Ando Y. Nakayama T. Miyamoto H. 《Electronics letters》2005,41(25):1371-1372
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power. 相似文献
10.
The copreheat-treatment of non-fusible and slightly fusible coals with A240 and hydrogenated A240 under high temperature-short contact-time conditions around 500 °C has been examined in an attempt to produce a formed coke with better anisotropic development. These conditions shortened the copreheat-treatment time and provided better anisotropic development in the resultant coke after carbonization. Effectiveness of short contact-time has been discussed in terms of the extent of depolymerization of coal molecules suitable for anisotropic development, this being related to coal liquefaction under similar conditions. 相似文献