全文获取类型
收费全文 | 747672篇 |
免费 | 8938篇 |
国内免费 | 1930篇 |
专业分类
电工技术 | 13528篇 |
综合类 | 641篇 |
化学工业 | 116467篇 |
金属工艺 | 29452篇 |
机械仪表 | 23735篇 |
建筑科学 | 17550篇 |
矿业工程 | 4736篇 |
能源动力 | 19708篇 |
轻工业 | 64026篇 |
水利工程 | 8406篇 |
石油天然气 | 16559篇 |
武器工业 | 44篇 |
无线电 | 83790篇 |
一般工业技术 | 148662篇 |
冶金工业 | 130955篇 |
原子能技术 | 16876篇 |
自动化技术 | 63405篇 |
出版年
2021年 | 6706篇 |
2020年 | 5029篇 |
2019年 | 6412篇 |
2018年 | 10961篇 |
2017年 | 11158篇 |
2016年 | 11881篇 |
2015年 | 7586篇 |
2014年 | 12771篇 |
2013年 | 34878篇 |
2012年 | 20289篇 |
2011年 | 27850篇 |
2010年 | 22169篇 |
2009年 | 24662篇 |
2008年 | 25310篇 |
2007年 | 25012篇 |
2006年 | 22049篇 |
2005年 | 20023篇 |
2004年 | 19096篇 |
2003年 | 18700篇 |
2002年 | 17893篇 |
2001年 | 17787篇 |
2000年 | 16797篇 |
1999年 | 16990篇 |
1998年 | 39349篇 |
1997年 | 28253篇 |
1996年 | 21899篇 |
1995年 | 16791篇 |
1994年 | 15037篇 |
1993年 | 14738篇 |
1992年 | 11252篇 |
1991年 | 10767篇 |
1990年 | 10599篇 |
1989年 | 10235篇 |
1988年 | 9881篇 |
1987年 | 8682篇 |
1986年 | 8402篇 |
1985年 | 9747篇 |
1984年 | 8847篇 |
1983年 | 8377篇 |
1982年 | 7568篇 |
1981年 | 7713篇 |
1980年 | 7277篇 |
1979年 | 7312篇 |
1978年 | 7105篇 |
1977年 | 7899篇 |
1976年 | 9889篇 |
1975年 | 6330篇 |
1974年 | 6056篇 |
1973年 | 6188篇 |
1972年 | 5165篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
M. Landí n M. P. Gonz lez C. Souto A. Concheiro J. L. G mez-Amoza R. Martí nez-Pacheco 《Drug development and industrial pharmacy》1993,19(10):1211-1220
In tests of direct-compression hydrochlorothiazide tablets prepared with either of two varieties of microcrystalline cellulose (Avicel PH 101 and Avicel PH 102), PH 102 tablets had better mechanical properties (owing to lower compressibility of mixtures and greater Interparticle bonding), while PH 101 tablets released the active principle faster. These differences are related to observed differences In tablet micropore structure. 相似文献
993.
994.
M Dorson E Quillet MG Hollebecq C Torhy B Chevassus 《Canadian Metallurgical Quarterly》1995,26(5-6):361-368
In 1984 a programme of selection for resistance to viral haemorrhagic septicaemia virus (VHSV) in rainbow trout was initiated. The progenies of 14 males were submitted to a VHSV waterborne challenge. The mortality ranged from 30 to 95% and the heritability of resistance was estimated to be 0.63 +/- 0.26. One male consistently provided the most resistant offspring, and the second generation was produced from sires and dams selected among these families. The mean resistance improved and several females giving birth to resistant offspring were identified (0-10% mortality while the mortality in the controls was from 70 to 90%). The meiotic gynogenetic progeny of these females also demonstrated high resistance (mortality less than 10%). The role of superficial tissues in the resistance was confirmed and there was a striking difference in the growth of VHSV in fins excised and infected in vitro. The fins from resistant fish replicated the virus poorly as compared with the fins of susceptible fish. 相似文献
995.
996.
M. A. Maksimov 《Metallurgist》1995,39(6):118
Translated from Metallurg, Vol. 39, No. 6, p. 45, June, 1995. 相似文献
997.
An extensive Markov process, which considers both the coding redundancy and the intersample redundancy, is presented to measure the entropy value of an ECG signal more accurately. It utilizes the intersample correlations by predicting the incoming n samples based on the previous m samples which constitute an extensive Markov process state. Theories of the extensive Markov process and conventional n repeated applications of m-th order Markov process are studied first. After that, they are realized for ECG exact coding. Results show that a better performance can be achieved by the authors' system. The average code length for the extensive Markov system on the second difference signals was 2.512 b/sample, while the average Huffman code length for the second difference signals was 3.326 b/sample 相似文献
998.
A Schultz 《Canadian Metallurgical Quarterly》1995,91(7):31-34
With change abounding in Canada's health care system, nurses must redefine their roles. One role is in health promotion, a field where nurses have created a unique identity for themselves. But before advocating, the concept must be fully understood. 相似文献
999.
G Bottino G Antognozzi R Degrandi C Augeri G Bogliolo P Zoccali 《Canadian Metallurgical Quarterly》1995,17(2-3):63-66
Blood concentration of endogenous beta-endorphines can change during the clinical evolution of chronic bronchopneumopathies. The authors assessed the beta-endorphine concentrations in the pulmonary arterial and systemic arterial blood in 8 asthmatic patients during a symptom-free period and after methacholine-induced bronchospasm. The beta-endorphine analysis was performed in duplicate dor each sample, by means of a RIA assay. There is not difference in the systemic arterial blood concentration of beta-endorphines between asthmatic patients and normal subjects. Furthermore, there is no change in the beta-endorphine blood concentration during the passage through the pulmonary tissue after methacoline-induced bronchospasm. 相似文献
1000.