全文获取类型
收费全文 | 206396篇 |
免费 | 2216篇 |
国内免费 | 566篇 |
专业分类
电工技术 | 3517篇 |
综合类 | 142篇 |
化学工业 | 31865篇 |
金属工艺 | 10273篇 |
机械仪表 | 7022篇 |
建筑科学 | 4002篇 |
矿业工程 | 2161篇 |
能源动力 | 4632篇 |
轻工业 | 12887篇 |
水利工程 | 2920篇 |
石油天然气 | 7726篇 |
武器工业 | 22篇 |
无线电 | 21554篇 |
一般工业技术 | 45232篇 |
冶金工业 | 34448篇 |
原子能技术 | 6624篇 |
自动化技术 | 14151篇 |
出版年
2021年 | 2054篇 |
2019年 | 2000篇 |
2018年 | 3679篇 |
2017年 | 3725篇 |
2016年 | 4005篇 |
2015年 | 2239篇 |
2014年 | 3789篇 |
2013年 | 8743篇 |
2012年 | 5686篇 |
2011年 | 7228篇 |
2010年 | 5865篇 |
2009年 | 6494篇 |
2008年 | 6621篇 |
2007年 | 6501篇 |
2006年 | 5581篇 |
2005年 | 5129篇 |
2004年 | 4634篇 |
2003年 | 4558篇 |
2002年 | 4376篇 |
2001年 | 4477篇 |
2000年 | 4189篇 |
1999年 | 4204篇 |
1998年 | 10201篇 |
1997年 | 7196篇 |
1996年 | 5512篇 |
1995年 | 4136篇 |
1994年 | 3603篇 |
1993年 | 3844篇 |
1992年 | 2990篇 |
1991年 | 3000篇 |
1990年 | 2892篇 |
1989年 | 2854篇 |
1988年 | 2868篇 |
1987年 | 2513篇 |
1986年 | 2571篇 |
1985年 | 2858篇 |
1984年 | 2695篇 |
1983年 | 2559篇 |
1982年 | 2305篇 |
1981年 | 2272篇 |
1980年 | 2346篇 |
1979年 | 2360篇 |
1978年 | 2386篇 |
1977年 | 2489篇 |
1976年 | 2883篇 |
1975年 | 2189篇 |
1974年 | 2071篇 |
1973年 | 2168篇 |
1972年 | 1940篇 |
1971年 | 1756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Weekly storage of coolness in heavy walls (walls with large thermal inertia or large characteristic time constants or low Fourier numbers) was investigated numerically by considering one-dimensional heat conduction through the walls. The study consisted of first analyzing the heat flow through a single wall and considering various boundary conditions on the inside. The boundary conditions were: constant inside air tempeture throughout the day, variable inside air temperature on a 24-hour cycle, and variable inside air temperature on a 48-hour cycle. Next, the heat flow through walls was studied through a thermal network analysis of a simple building. In this case it was assumed that the ambient air temperature (following a periodic distribution) was increased suddenly and followed this new distribution for many days thereafter.It was concluded that walls with high thermal inertia or time constant can store coolness for several days. The larger the time constant of the wall (for example adobe as compared with brick) the longer it takes for the wall temperature to reach a steady periodic distribution after the change has occurred. However, because of low thermal conductivity of adobe, the retrieval of the stored coolness in these walls is slow, and the mean daily temperature of the room air in the adobe building does not change appreciably beyond seven days after the change. Increase of the wall thickness beyond 50 cm does not improve the thermal performance of the building significantly. 相似文献
995.
Vasilenko O. A. Maier A. A. Chashchin V. A. Gulaeva E. N. Bus'ko V. I. 《Journal of Engineering Physics and Thermophysics》1985,49(3):1105-1108
A method of calculating the temperature resistance coefficient and its temperature dependence for resistive materials in the approximation of a matrix-statistical structure is outlined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 477–481, September, 1985. 相似文献
996.
Immunoassay method for the determination of immunoglobulin G using bacterial magnetic particles. 总被引:7,自引:0,他引:7
We have developed a novel immunoassay method using bacterial magnetic particles for the determination of immunoglobulin G (IgG). Fluorescein isothiocyanate (FITC) conjugated anti IgG-bacterial magnetic particles were prepared. The fluorescence quenching caused by agglutination of FITC-anti IgG antibody-bacterial magnetic particle conjugates was measured by using a fluorescence spectrophotometer. The aggregates based on specific immunoreaction were separated by a gelatin solution. The aggregation of bacterial magnetic particle conjugates was enhanced by application of a magnetic field. The relative fluorescence intensity correlated linearly with a concentration of IgG in the range 0.5-100 ng/mL. 相似文献
997.
A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error. 相似文献
998.
Non-specific antitumoral activity of staphylococcal enterotoxins 总被引:2,自引:0,他引:2
O N Shcheglovitova A D Voskobo?nik M N Solov'eva M K Fan'kovskaia Iu V Ezepchuk 《Eksperimental?nai?a onkologii?a》1987,9(1):28-30
St. aureus enterotoxins A and B possess an antitumour effect. After intraperitoneal inoculation they decrease the size and in some cases prevent the development of the human hypernephroma in the cheek pouch of golden hamsters. The effect of enterotoxins may possibly consist in inducing the production of endogenous immune interferon which activates the host immune system and enhances the rejection of heterologous tumour cells. 相似文献
999.
A comparison is made between passive ring-resonator and interferometric fiber-optic gyroscope sensitivity to the radiation darkening of optical fibers. The radiation degradation factor for each type of gyroscope is developed, and figures of merit are given for comparing gyroscopes independently of the specific mechanization or modulation scheme used. It is shown that for most practical situations, interferometric gyros offer superior performance in radiation environments 相似文献
1000.
The rate of absorption of amino acids obtained from isolated krill protein administered to rat stomach was studied. Absorption of casein amino acids was determined for reference purposes. Rats subjected to 48-hour fasting were administered krill isolate and casein in the form of homogenates at a rate 540 mg protein per 100 g bw in 6 ml of distilled water. The concentration of free amino acids in the portal vein was measured after 30 minutes, 1, 3 and 6 hours. The content of amino acids was measured by ion-exchange chromatography with the use of an automatic analyzer of amino acids. The digestion of krill protein proceeds at a high rate. This ensures the maximal augmentation of the concentration of most amino acids in the blood of the portal vein 30 min after isolate administration to the stomach. 相似文献