全文获取类型
收费全文 | 6312篇 |
免费 | 108篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 259篇 |
综合类 | 4篇 |
化学工业 | 1077篇 |
金属工艺 | 193篇 |
机械仪表 | 113篇 |
建筑科学 | 84篇 |
矿业工程 | 1篇 |
能源动力 | 186篇 |
轻工业 | 430篇 |
水利工程 | 21篇 |
石油天然气 | 4篇 |
无线电 | 790篇 |
一般工业技术 | 1020篇 |
冶金工业 | 1740篇 |
原子能技术 | 174篇 |
自动化技术 | 333篇 |
出版年
2023年 | 19篇 |
2022年 | 52篇 |
2021年 | 79篇 |
2020年 | 35篇 |
2019年 | 39篇 |
2018年 | 84篇 |
2017年 | 58篇 |
2016年 | 94篇 |
2015年 | 59篇 |
2014年 | 104篇 |
2013年 | 210篇 |
2012年 | 156篇 |
2011年 | 207篇 |
2010年 | 164篇 |
2009年 | 174篇 |
2008年 | 203篇 |
2007年 | 200篇 |
2006年 | 193篇 |
2005年 | 170篇 |
2004年 | 168篇 |
2003年 | 177篇 |
2002年 | 158篇 |
2001年 | 150篇 |
2000年 | 158篇 |
1999年 | 192篇 |
1998年 | 640篇 |
1997年 | 406篇 |
1996年 | 268篇 |
1995年 | 209篇 |
1994年 | 203篇 |
1993年 | 185篇 |
1992年 | 103篇 |
1991年 | 91篇 |
1990年 | 96篇 |
1989年 | 95篇 |
1988年 | 84篇 |
1987年 | 76篇 |
1986年 | 72篇 |
1985年 | 78篇 |
1984年 | 57篇 |
1983年 | 54篇 |
1982年 | 57篇 |
1981年 | 57篇 |
1980年 | 35篇 |
1979年 | 43篇 |
1978年 | 29篇 |
1977年 | 45篇 |
1976年 | 73篇 |
1975年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有6429条查询结果,搜索用时 0 毫秒
991.
Urinary trypsin inhibitor (UTI) is a physiological protease inhibitor and inter-alpha-trypsin inhibitor (ITI) is regarded as a precursor of UTI. The purpose of this study is to determine the mechanism of the UTI release from ITI. To examine this, ITI was digested by human neutrophil elastase at various concentrations, and UTI-related proteins which were of the same size as UTI were obtained. The amino acid sequence of the 15 amino acid residues at the N-terminal of UTI-related proteins, corresponded to that of UTI. The amino acid sequences of the small amount of peptides detected corresponded to those of peptides from the heavy chain1 (H1) and the heavy chain2 (H2) of ITI, suggesting that most UTI-related proteins do not combine with peptides from the H1 and H2 of ITI. It was also revealed that UTI-related proteins have several physiological activities similar to those of UTI, i.e., human trypsin inhibitory activity, human neutrophil elastase inhibitory activity, inhibition of tumor necrosis factor-alpha (TNF-alpha) production from rat macrophages and of superoxide production from rabbit leukocytes. These results demonstrated that ITI is a precursor of UTI which is digested by human neutrophil elastase to release UTI, and that its elastase inhibitory activity is derived from UTI. 相似文献
992.
993.
Determination of cyanide in whole blood by capillary gas chromatography with cryogenic oven trapping
A Ishii H Seno K Watanabe-Suzuki O Suzuki T Kumazawa 《Canadian Metallurgical Quarterly》1998,70(22):4873-4876
Cyanide, one of the most important toxic substances, has been found measurable with high sensitivity by capillary gas chromatography (GC) with cryogenic oven trapping upon injection of headspace (HS) vapor samples. The entire amount of cyanide in the HS sample could be cryogenically trapped prior to on-line GC analysis. A 0.5-mL volume of blood in the presence or absence of cyanide and propionitrile (internal standard, IS) was added to a vial containing 0.25 mL of distilled water, 0.3 g of Na2-SO4, 0.2 mL of 50% H3PO4, and 0.1 g of ascorbic acid (when needed), and the mixture was heated at 70 degrees C for 15 min. A 5-mL volume of the HS vapor was introduced into a GC capillary column in the splitless mode at -30 degrees C oven temperature that was programmed up to 160 degrees C for GC analysis with nitrogen-phosphorus detection. A sharp peak was obtained for cyanide under the present conditions, and backgrounds were very clean. The extraction efficiencies of cyanide and IS were 2.89-3.22 (100 or 500 ng/mL) and 2.42%, respectively. The calibration curve showed good linearity in the range of 25-1000 ng/mL and the detection limit was approximately 2 ng/mL. The coefficients of intraday and interday variations were 2.9 and 11.8%, respectively. The mean blood cyanide level measured for actual fire victims was 687 +/- 597 ng/mL (mean +/- SD, n = 9). Endogenous blood cyanide concentration for healthy subjects was 8.41 +/- 3.09 ng/mL (mean +/- SD, n = 6). 相似文献
994.
995.
S Shindo A Kojima K Iyori T Ishimoto M Kobayashi O Suzuki K Kamiya Y Tada 《Canadian Metallurgical Quarterly》1998,28(5):498-502
A 6-year prospective study of 80 abdominoplasties is reported. Type and incidence of complications are presented with particular attention toward the incidence of fluid collection following abdominoplasty, such as seroma and hematoma. Ultrasound was performed in 56 patients (70%), with normal findings in 27 patients (48%). Accurate diagnosis of fluid collection in 29 patients (51.8%), seroma in 24 (42.8%), and hematoma in 5 (9%) was confirmed with the aid of ultrasound. The advantage of early radiological diagnosis alerted the surgeon for positive findings of fluid collection areas in the abdominal wall, which resulted in close observation and early intervention whenever indicated. Ultrasound of the abdominal wall following abdominoplasty provides a noninvasive, accurate, and low-cost method of diagnosing fluid collection in the abdominal wall. This method, if performed routinely postabdominoplasty, will aid the surgeon in managing potential complications such as wound-healing problems, infection, and patient discomfort. 相似文献
996.
The letter reports the concept of a new switching/amplifying network, and its basic performance, for scanning the down-link beam rapidly in multibeam satellite systems. Experiments in the K-band have shown 85% power-combining efficiency, more than 17 dB isolation and 400 ns switching speed. 相似文献
997.
Samejima S. Inoue T. Kagoshima K. Inoue M. Suzuki M. 《Selected Areas in Communications, IEEE Journal on》1983,1(1):118-125
An experimental one-way multiaddress data communication system accommodating many small receive-only terminals is described. In this system, a digital facsimile is used as the output equipment. A simple one-way transmission protocol adopting the flag synchronization method has been developed so that facsimile equipment of different speeds can be used. The receive-only terminal comprises an antenna, an RF receiver, a demodulator, and a channel selector. The antenna is an offset parabolic type with an effective diameter of 60 cm and uses a printed spiral type primary radiator. Dimensions of the terminal are 70 cm wide, 88 cm deep, and 126 cm high. The satellite channel bit rate is 64 kbits/s in order to transmit multiple facsimile data simultaneously. Experiments using the Japanese "CS" satellite have been carried out to verify the system feasibility. The normal bit error rate was less than 10-6and line errors occurred less than once in three facsimile transmissions. 相似文献
998.
Paveena Srirangsan Kiyoshi Kawai Naoko Hamada-Sato Manabu Watanabe Toru Suzuki 《Food chemistry》2010,119(1):209-213
In order to improve the remaining activity of a practically important freeze-dried enzyme, xanthine oxidase (XOD), the effects of disaccharide (sucrose and trehalose), polymer (bovine serum albumin: BSA and dextran) and a mixture of them on the loss of XOD activity during freeze-drying and subsequent storage were investigated. All samples were amorphous solids and their glass transition temperatures (Tg) were evaluated by using differential scanning calorimetry. Although dextran showed no stabilizing effect on the freeze-dried XOD, the others protected XOD from the activity loss during freeze-drying to a certain extent. It was found that the mixture of disaccharide (sucrose or trehalose) and BSA improved the XOD activity synergistically. The XOD activity of the samples decreased gradually during storage at a temperature range of between 25 and 60 °C. Samples stored at temperatures below the Tg showed a lower loss of XOD activity than those stored at just the Tg. 相似文献
999.
ABSTRACT: Ultrasound has been used for the last 50 y in different processing applications. Depending on the power and frequency of the sound waves, ultrasound techniques can be classified in different categories. Low-intensity ultrasound uses high frequencies in the range of 100 kHz to 10 MHz and is mostly used for therapeutic purpose (frequencies between 1 and 10 MHz) and to passively monitor the characteristics of materials (frequencies between 100 kHz and 10 MHz). High-intensity ultrasound (HIU), on the other hand, uses lower frequencies in the range of 20 to 100 kHz and it is commonly used for cleaning, disrupting, and restructuring materials. The objective of this study is to evaluate the effect of HIU on functional properties of anhydrous milk fat (AMF), palm kernel oil (PKO), and an all-purpose shortening (Sh). Results from this research shows that HIU induced primary and secondary nucleation in the lipid, generating smaller crystals and as a consequence harder materials. HIU affected hardness more efficiently when applied at higher crystallization temperatures (26 and 28 °C) as shown for AMF data, and when the sonication was applied after the first crystals were formed as observed for PKO and Sh systems. In addition to changes in hardness, AMF and Sh networks obtained after sonication were characterized by a steeper and sharper melting profile. This research shows that HIU can be used as an additional processing tool to tailor the functional properties of lipids with the potential to be used in the processing of trans-free shortenings. 相似文献
1000.
Effects of lipase,lipoxygenase, peroxidase and free fatty acids on volatile compound found in boiled buckwheat noodles 总被引:1,自引:0,他引:1
Tatsuro Suzuki Sun‐Ju Kim Yuji Mukasa Toshikazu Morishita Takahiro Noda Shigenobu Takigawa Naoto Hashimoto Hiroaki Yamauchi Chie Matsuura‐Endo 《Journal of the science of food and agriculture》2010,90(7):1232-1237
BACKGROUND: Relationships between buckwheat (Fagopyrum esculentum Moench) flour lipase, lipoxygenase and peroxidase activity, along with levels of individual free fatty acids (FFAs) and levels of headspace volatile compounds of boiled buckwheat noodles, were investigated for 12 different buckwheat varieties. Enzyme activities and FFA levels in flour were correlated with their respective varietal arrays of boiled noodle headspace volatile compounds, measured by gas chromatography–mass spectrometry. RESULTS: The volatiles hexanal, tentative butanal, tentative 3‐methylbutanal and tentative 2‐methylbutanal showed significant positive correlation with one another, indicating that they may be generated through similar mechanisms. These important volatile components of buckwheat flavor were also positively correlated with lipase and/or peroxidase activity, indicating that enzymatic reactions are important in flavor generation in boiled buckwheat noodles. On the other hand, pentanal, which showed no significant correlation with any enzyme activity, showed a significant positive correlation to the levels of C18:2 and C18:3 FFAs, suggesting the existence of a ‘non‐enzymatic’ and/or ‘uncertain enzymatic pathway’ for flavor generation in boiled buckwheat noodles. CONCLUSION: Lipase and peroxidase in buckwheat flour are important for flavor generation of boiled buckwheat noodles. This information is important for increasing desirable flavor of buckwheat products as well as for selecting varieties with improved flavor. Copyright © 2010 Society of Chemical Industry 相似文献