全文获取类型
收费全文 | 406944篇 |
免费 | 5988篇 |
国内免费 | 2346篇 |
专业分类
电工技术 | 8176篇 |
技术理论 | 5篇 |
综合类 | 1255篇 |
化学工业 | 65044篇 |
金属工艺 | 17297篇 |
机械仪表 | 11956篇 |
建筑科学 | 10349篇 |
矿业工程 | 2440篇 |
能源动力 | 9541篇 |
轻工业 | 38643篇 |
水利工程 | 4246篇 |
石油天然气 | 8515篇 |
武器工业 | 245篇 |
无线电 | 44047篇 |
一般工业技术 | 76307篇 |
冶金工业 | 75429篇 |
原子能技术 | 8986篇 |
自动化技术 | 32797篇 |
出版年
2021年 | 3534篇 |
2019年 | 3108篇 |
2018年 | 5016篇 |
2017年 | 4974篇 |
2016年 | 5414篇 |
2015年 | 4100篇 |
2014年 | 6731篇 |
2013年 | 17811篇 |
2012年 | 11306篇 |
2011年 | 15277篇 |
2010年 | 12163篇 |
2009年 | 13399篇 |
2008年 | 14106篇 |
2007年 | 14296篇 |
2006年 | 12453篇 |
2005年 | 11151篇 |
2004年 | 10234篇 |
2003年 | 9588篇 |
2002年 | 9585篇 |
2001年 | 9662篇 |
2000年 | 9143篇 |
1999年 | 9225篇 |
1998年 | 21551篇 |
1997年 | 15731篇 |
1996年 | 12052篇 |
1995年 | 9165篇 |
1994年 | 8126篇 |
1993年 | 7958篇 |
1992年 | 6114篇 |
1991年 | 5885篇 |
1990年 | 5840篇 |
1989年 | 5836篇 |
1988年 | 5520篇 |
1987年 | 4833篇 |
1986年 | 4774篇 |
1985年 | 5442篇 |
1984年 | 5143篇 |
1983年 | 4791篇 |
1982年 | 4290篇 |
1981年 | 4548篇 |
1980年 | 4162篇 |
1979年 | 4346篇 |
1978年 | 4223篇 |
1977年 | 4648篇 |
1976年 | 6013篇 |
1975年 | 3757篇 |
1974年 | 3574篇 |
1973年 | 3674篇 |
1972年 | 3105篇 |
1971年 | 2829篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Tests of a prototype model of TUK-84 and the corresponding experimental procedures used at the test center of the All-Russia
Research Institute of Technical Physics are described. The results are presented, and it is shown that the prototype withstood
the tests.
__________
Translated from Atomnaya énergiya, Vol. 100, No. 6, pp. 441–445, June, 2006. 相似文献
992.
Fractures of group II (according to the classification given in Part 1) are described in detail. The deviations of the structure of a fracture from the groups of fiber and crystalline fractures are explained by the chemical micro- and macroinhomogeneity of the metal. The characteristics of fractures, the causes of their formation, the methods for fighting and eliminating them, and the interrelation with the mechanical properties of the steel are described. Every kind of fracture is illustrated. 相似文献
993.
This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input AC voltage of 220 Vrms and an output voltage of 400 VDC has been implemented in the laboratory. An efficiency of 97.8 % at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper 相似文献
994.
1. In 1980, the skin of certain frogs belonging to the genus Phyllomedusinae was found to contain two new peptides that proved to be selective mu-opioid agonists. Given the name dermorphins, these were the first members of a peptide family that in the past 15 years has grown to reach a total of seven naturally occurring peptides and nearly 30 synthetic analogs. 2. Dermorphin peptides are potent analgesics in rodents and primates, including man. Some dermorphins can enter the blood-brain barrier and produce central antinociception after peripheral administration. 3. The dermorphin family also includes mu 1-opioid receptor selective agonists that produce intense opioid analgesia, but stimulate pulmonary ventilation. 4. Experiments in rats and mice chronically exposed to dermorphins have shown that not only do they have higher antinociceptive efficacy and potency than morphine, but they are also less likely than morphine to produce tolerance, dependence and opiate side effects. 相似文献
995.
GS Wengler A Lanfranchi T Frusca R Verardi A Neva D Brugnoni S Giliani M Fiorini P Mella F Guandalini E Mazzolari S Pecorelli LD Notarangelo F Porta AG Ugazio 《Canadian Metallurgical Quarterly》1996,348(9040):1484-1487
BACKGROUND: X-linked severe combined immunodeficiency (SCIDXI) is an inherited immune defect which leads to death in infancy from severe infections. The defect is caused by mutations of the IL-2RG gene that encodes for the common gamma chain shared by several cytokine receptors. The disease is characterised by lack of T and NK cells with normal numbers of B cells. SCIDXI can be cured by bone marrow transplantation (BMT) or prevented by abortion after prenatal diagnosis. METHODS: A male fetus was diagnosed as having SCIDXI by molecular, immunophenotypic, and functional analyses. The fetus was injected intraperitoneally under ultrasound guidance with CD34 haematopoietic progenitor cells purified from paternal bone marrow and T-cell depleted by E rosetting. Chimerism analysis was by HLA-DQ alpha typing and gamma-chain staining on cord blood. FINDINGS: A healthy 3.6 kg boy was delivered by caesarean section at 38 weeks of gestation with no clinical or laboratory signs of graft-versus-host disease. Engraftment of donor-derived CD2 cells was found at birth. At 3.5 months of age the infant is well and his T-cell counts and function are normal. INTERPRETATION: In-utero transplantation of haematopoietic progenitor cells allowed immune reconstitution of a fetus with SCIDXI and may be an alternative to elective abortion. Our report should encourage applications of this method to other inherited disorders curable by BMT. 相似文献
996.
997.
Space vector modulation has recently become a popular PWM method of supplying a high performance drive. An adaptation of SVM modulation is presented here. This system is called bus clamped space vector modulation. This method has some practical advantages when compared to normal SVM. These include a reduced average switching frequency, easy digital implementation and asynchronous control and switching frequencies 相似文献
998.
999.
1000.