全文获取类型
收费全文 | 1480篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 124篇 |
金属工艺 | 15篇 |
机械仪表 | 28篇 |
建筑科学 | 28篇 |
矿业工程 | 2篇 |
能源动力 | 28篇 |
轻工业 | 86篇 |
无线电 | 70篇 |
一般工业技术 | 138篇 |
冶金工业 | 901篇 |
原子能技术 | 5篇 |
自动化技术 | 58篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 43篇 |
2012年 | 31篇 |
2011年 | 22篇 |
2010年 | 25篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 27篇 |
2006年 | 20篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 43篇 |
1998年 | 274篇 |
1997年 | 160篇 |
1996年 | 105篇 |
1995年 | 67篇 |
1994年 | 49篇 |
1993年 | 62篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 13篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 28篇 |
1976年 | 53篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有1489条查询结果,搜索用时 10 毫秒
71.
A certain equivalent state-variable representation of a system defined by a rational transfer function, and stimulated by an impulse function, leads to equations in which not only the impulse response but also the step response and, if need be, the ramp response, are simply derived from the state variables. 相似文献
72.
73.
PM Johnson AO Ogbimi MJ Diver AW Thomson RD Bremner CH Horne 《Canadian Metallurgical Quarterly》1980,59(2):437-440
Placental protein 5 (PP5), pregnancy-specific glycoprotein (SP1), pregnancy-associated alpha 2-glycoprotein (SP3) and chorionic gonadotrophin could not be demonstrated in appreciable molar quantities in the soluble fraction from microvillous plasma membrane preparations isolated from the syncytiotrophoblast of full-term human placentae. However, progesterone, total oestriol and placental lactogen may have some association with this membrane. 相似文献
74.
Seven normal male subjects performed 5-min bicycle exercise ranging from 50-100% maximum oxygen uptake at 4 ATA and three were also studied at 6 ATA. At all pressures, the subjects breathed 0.2 ATA O2 plus nitrogen. All subjects were able to perform maximum work at all pressures. No pressure-dependent variations in heart rate, O2 uptake, or CO2 output were noted. At both 4 and 6 ATA, ventilation was decreased at exercise levels greater than 80% maximum O2 uptake. The magnitude of the decrease was not great, however, and signified only minor CO2 retention. In some instances exercise ventilation closely approached the 15-S maximum breathing capacity and these subjects noted severe dyspnea, possibly due to dynamic compression of large airways. In three subjects, respiratory frequency was measured as well as minute ventilation; this relationship did not change with depth. Subjects performing heavy exercise at 6 ATA noted disturbances of consciousness, presumably due to N2 narcosis. 相似文献
75.
76.
Robert J. Thomson Robert K. Belford Robert Q. Cannell 《Journal of the science of food and agriculture》1983,34(11):1159-1162
Post-germination but pre-emergence waterlogging of winter wheat for 3 days or more, delayed emergence and decreased the final number of plants in two experiments on sandy loam and clay soils in outdoor conditions. Coating seeds with calcium peroxide improved emergence to a small extent, but would appear to offer only a small benefit to establishment of wheat already treated with insecticide/fungicide dressings and sown under normal conditions in the field. 相似文献
77.
The fit of tumor multiplicity data from 93 mouse skin, lung, and liver carcinogenicity experiments to Poisson, negative binomial, and normal distributions was studied. The data were fitted well by the negative binomial distribution. This distribution has two parameters, the mean tumor multiplicity and an exponent determined by the interanimal homogeneity of tumor response. The value of the latter parameter was related to animal strain and the target tissue studied in the carcinogenicity experiments. The null distribution of the two-sample likelihood ratio test based on the negative binomial with common exponent model for tumor multiplicity data was shown by simulation studies to be approximately chi 2 with 1 d.f. Simulation also indicated that the likelihood ratio test has sufficiently better performance when the negative binomial model is valid to make its use more attractive than the more commonly used Wilcoxon test or Student t test. Charts for estimating the number of animals per group that are required to detect specified differences in tumor multiplicities are provided for several commonly used assays. 相似文献
78.
79.
80.