全文获取类型
收费全文 | 198775篇 |
免费 | 2130篇 |
国内免费 | 633篇 |
专业分类
电工技术 | 4068篇 |
综合类 | 123篇 |
化学工业 | 26801篇 |
金属工艺 | 7540篇 |
机械仪表 | 5481篇 |
建筑科学 | 4058篇 |
矿业工程 | 749篇 |
能源动力 | 4685篇 |
轻工业 | 14461篇 |
水利工程 | 1698篇 |
石油天然气 | 2847篇 |
武器工业 | 7篇 |
无线电 | 27349篇 |
一般工业技术 | 37528篇 |
冶金工业 | 45754篇 |
原子能技术 | 3579篇 |
自动化技术 | 14810篇 |
出版年
2021年 | 1254篇 |
2019年 | 1288篇 |
2018年 | 2132篇 |
2017年 | 2112篇 |
2016年 | 2179篇 |
2015年 | 1497篇 |
2014年 | 2634篇 |
2013年 | 7994篇 |
2012年 | 4477篇 |
2011年 | 6147篇 |
2010年 | 4954篇 |
2009年 | 5796篇 |
2008年 | 6171篇 |
2007年 | 6229篇 |
2006年 | 5650篇 |
2005年 | 5333篇 |
2004年 | 5271篇 |
2003年 | 5113篇 |
2002年 | 4914篇 |
2001年 | 5327篇 |
2000年 | 4943篇 |
1999年 | 5469篇 |
1998年 | 15715篇 |
1997年 | 10367篇 |
1996年 | 7969篇 |
1995年 | 5813篇 |
1994年 | 5028篇 |
1993年 | 5048篇 |
1992年 | 3405篇 |
1991年 | 3268篇 |
1990年 | 3233篇 |
1989年 | 3059篇 |
1988年 | 2797篇 |
1987年 | 2245篇 |
1986年 | 2310篇 |
1985年 | 2615篇 |
1984年 | 2319篇 |
1983年 | 2073篇 |
1982年 | 1912篇 |
1981年 | 2056篇 |
1980年 | 1803篇 |
1979年 | 1674篇 |
1978年 | 1663篇 |
1977年 | 2037篇 |
1976年 | 2719篇 |
1975年 | 1426篇 |
1974年 | 1375篇 |
1973年 | 1320篇 |
1972年 | 1128篇 |
1971年 | 959篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Zinc and Phytate Distribution in Peas. Influence of Heat Treatment, Germination, pH, Substrate, and Phosphorus on Pea Phytate and Phytase 总被引:1,自引:0,他引:1
The largest proportions of zinc and phytate, 88.7 and 97.1%, respectively, were in the Garfield pea cotyledon; the greatest concentrations were in the germ. Cooking peas by two different methods resulted in 13% phytate reduction. Peas incubated 6.5 hr from 25 to 80°C yielded maximum phytate loss (25%) at 60°C due to phytase activated hydrolysis. Germination (10 d) decreased pea phytate 75% and increased phytase activity 12-fold. Semi-purified germinated pea phytase showed temperature optimum at 45°C, pH optimum of 5.2, 30% inhibition by 1 mM inorganic P, and substrate preference for pyrophosphate. Incubation of early germinated peas at optima pH and temperature is suggested for maximum phytate reduction. 相似文献
992.
T. MATTILA-SANDHOLM T. ALI-VEHMAS G. WIRTANEN U. RÖNNER M. SANDHOLM 《International Journal of Food Science & Technology》1991,26(3):325-336
Automated monitoring of the microbiological quality of heat-processed foods by the resazurin reduction test was applied to microtitration plate incubator-fluorimeter technology. The appearance and disappearance of the fluorescing peak of resorufin was monitored on microtitration trays. Pasteurized or ultra-high temperature-treated starch-based soup was used as the model food system. Bacillus subtilis spores (ultra-high temperature treatment) and vegetative cells of Enterococcus faecalis (pasteurization) were inoculated into the soup before the heat treatment at levels which resulted in some survival. The timing of appearance of maximum fluorescence correlated with the number of bacteria in pre-incubated samples. Automated resazurin-reduction fluorimetry was compared with conventional plating, turbidometry and microcolony count by the direct epifluorescent filter technique. The results of the resazurin test correlated well with those of all the other methods tested. Fluorimetry had the advantage that the results could be read within 1–5h and the reproducibility was superior to the other methods. 相似文献
993.
Self-organizing communication networks 总被引:3,自引:0,他引:3
994.
The tsunami of December 2004 destroyed infrastructure in many coastal areas in South-East Asia. In January 2005, the Danish Government gave a tsunami relief grant to Thailand to re-establish the wastewater management services in some of the areas affected by the tsunami. This paper describes the systems which have been built at three locations: (a) Baan Pru Teau: A newly-built township for tsunami victims which was constructed with the contribution of the Thai Red Cross. Conventional septic tanks were installed for the treatment of blackwater from each household and its effluent and grey water (40 m3/day) are collected and treated at a 220 m2 subsurface flow constructed wetland. (b) Koh Phi Phi Don island: A wastewater collection system for the main business and hotel area of the island, a pumping station and a pressure pipe to the treatment facility, a multi-stage constructed wetland system and a system for reuse of treated wastewater. The constructed wetland system (capacity 400 m3/day) consists of vertical flow, horizontal subsurface flow, free water surface flow and pond units. Because the treatment plant is surrounded by resorts, restaurants and shops, the constructed wetland systems are designed with terrains as scenic landscaping. (c) Patong: A 5,000 m2 constructed wetland system has been established to treat polluted water from drainage canals which collect overflow from septic tanks and grey water from residential areas. It is envisaged that these three systems will serve as prototype demonstration systems for appropriate wastewater management in Thailand and other tropical countries. 相似文献
995.
Hida H. Tsukada Y. Ogawa Y. Toyoshima H. Fujii M. Shibahara K. Kohno M. Nozaki T. 《Electron Devices, IEEE Transactions on》1989,36(10):2223-2230
The authors describe a novel design concept for enhancement (E) and depletion (D) mode FET formation using i-AlGaAs/n-GaAs doped-channel hetero-MISFET (DMT) and a novel self-aligned gate process technology for submicrometer-gate DMT-LSIs based on E/D logic gates. 0.5-μm gate E-DMTs (D-DMTs) with a lightly doped drain (LDD) structure show an average V t of 0.18 (-0.46) V, a V t standard deviation of 22.6 (24.9) mV, and a maximum transconductance of 450 (300) mS/mm. The V t shift is less than 50 mV with a decrease in gate length down to 0.5 μm. The gate forward turn-on voltage V f is more than 0.9 V, i.e. about 1.6 times that for MESFETs. This superiority in V f, preserved in the high-temperature range, leads to an improvement in noise margin tolerance by a factor of three. In addition, 31-stage ring oscillators operate with a power consumption of 20 (1.0) mW/gate and a propagation delay of 4.8 (14.5) ps/gate. Circuit simulation based on the experimental data predicts 140 ps/gate and 1 mW/gate for DMT direct-coupled FET logic circuits under standard loading conditions. DMTs and the technology developed here are very attractive for realizing low-power and/or high speed LSIs 相似文献
996.
997.
T. M. Morris 《Journal of the Institute of Brewing》1987,93(1):13-17
Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values. 相似文献
998.
Vaporization of alloying elements is a serious problem in the laser welding of many important engineering alloys. Since the
available mass transfer correlations are not applicable for credible assessment of the rates of transport of vaporized species
in the gas phase, the role of gas phase mass transfer in the overall vaporization of alloying elements was examined by conducting
several critical experiments. The rates of transport of alloying elements in the weld pool were determined from numerically
computed fluid flow fields. Since the weld pool is surrounded by plasma during laser welding, the role of plasma in the vaporization
of alloying elements was physically modeled by allowing molten copper drops to vaporize isothermally both in the presence
and absence of plasma. The transport of alloying elements in both liquid and gas phases was found to be rapid and the overall
vaporization rates were controlled by the plasma influenced intrinsic vaporization of alloying elements at the weld pool surface.
The experimentally obtained rates of vaporization of alloying elements from laser melted stainless steel weld pools were compared
with the corresponding theoretically calculated values. 相似文献
999.
An experimental and theoretical study into the use of Fabry-Perot etalons as static repetition rate upconverters outside the laser cavity is discussed. It is shown that the output repetition rate can be increased up to 12 times while maintaining high average power 相似文献
1000.