全文获取类型
收费全文 | 3694篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 290篇 |
金属工艺 | 106篇 |
机械仪表 | 113篇 |
建筑科学 | 6篇 |
矿业工程 | 59篇 |
能源动力 | 22篇 |
轻工业 | 31篇 |
水利工程 | 49篇 |
石油天然气 | 148篇 |
无线电 | 170篇 |
一般工业技术 | 643篇 |
冶金工业 | 1764篇 |
原子能技术 | 186篇 |
自动化技术 | 88篇 |
出版年
2022年 | 24篇 |
2021年 | 29篇 |
2019年 | 27篇 |
2018年 | 58篇 |
2017年 | 58篇 |
2016年 | 63篇 |
2015年 | 29篇 |
2014年 | 50篇 |
2013年 | 79篇 |
2012年 | 68篇 |
2011年 | 57篇 |
2010年 | 60篇 |
2009年 | 55篇 |
2008年 | 67篇 |
2007年 | 73篇 |
2006年 | 58篇 |
2005年 | 52篇 |
2004年 | 80篇 |
2003年 | 41篇 |
2002年 | 36篇 |
2001年 | 45篇 |
2000年 | 44篇 |
1999年 | 55篇 |
1998年 | 446篇 |
1997年 | 289篇 |
1996年 | 203篇 |
1995年 | 126篇 |
1994年 | 101篇 |
1993年 | 139篇 |
1992年 | 38篇 |
1991年 | 40篇 |
1990年 | 29篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 30篇 |
1983年 | 27篇 |
1982年 | 35篇 |
1981年 | 45篇 |
1980年 | 53篇 |
1979年 | 31篇 |
1978年 | 29篇 |
1977年 | 130篇 |
1976年 | 225篇 |
1975年 | 41篇 |
1974年 | 35篇 |
1973年 | 31篇 |
1972年 | 25篇 |
1969年 | 25篇 |
排序方式: 共有3707条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
A method of measuring and identifying the static parameters of a bipolar transistor is considered. The characteristic of the transistor, from which the parameters of the model are determined, is chosen depending on what group the calculated parameters belong to. The characteristics are measured in such a way that the equations of the model describing them can be reduced to the simplest form. 相似文献
5.
Vascular injuries may occur as complications of elbow dislocation and usually involve the brachial artery. A case report is presented in which only the radial artery was compromised as a result of the dislocation. 相似文献
6.
KhKh Sharafetdinov VA Meshcheriakova OA Plotnikova 《Canadian Metallurgical Quarterly》1998,86(3):30-33
The paper analyzes left ventricular structure-fraction relationships in the development of postinfarct aneurysm. The altered internal architectonics induces to systemic hemodynamic changes, drastically elevated intraventricular pressure. This is caused by to the dysfunction of the papillary-trabecular complex in the left ventricular cavity, which in turn. This leads to the fact that the heart work as a positive-displacement pump, by losing its capacity as a centrifugal component, by making the myocardium require additional energy expenditures, which in turn appears as varying heart failure. This investigation is of definite practical value in developing adequate correction methods for postinfarct aneurysm which can occur with the retained or formed certain ratios of cardiac structures. 相似文献
7.
The properties of a spinel copper cobaltite obtained by thermal decomposition of mixed nitrates of both metals at 350°C and normal pressure are described. It has been shown that the maximum copper content (x) in the spinel CuxCo3?xO4 does not exceed 0.9. When the copper amount in the initial mixture is higher a second phase CuO is formed. The copper ions are distributed over the A- and the B-sites of the spinel lattice, i.e. the spinel is partially inverted. Such a model explains well the data obtained about the lattice parameter, IR-absorption and the magnetic susceptibility of the samples with different x. 相似文献
8.
9.
The article established the regularities of change of the physicomechanical characteristics and strength of glass textolites in single and repeated thermal loading. It shows that under multiple loading the intense loss of strength of the investigated materials is due to increased porosity on account of the large number of microcracks appearing in the structure. A correlation is obtained between the elastic and strength characteristics and porosity in dependence on the temperature of multiple heating which in the first approximation is described by a polynomial of second degree with respect to temperature, multiplied by the reciprocal of porosity.Translated from Problemy Prochnosti, No. 6, pp. 53–58, June, 1991. 相似文献
10.
N. Balchev D. Kovacheva V. Lovchinov K. Konstantinov K. Petrov 《Journal of Superconductivity》1993,6(1):49-54
The preparation conditions, phase composition, and superconducting properties of Bi-Pb-Sr-Ca-Cu oxide materials from different nominal compositions have been investigated. Nearly single-phase samples from Bi2Pb0.4Sr2Ca3Cu4O
y
, as well as from the proposed compositions Bi1.8Pb0.4Sr2Ca3Cu4O
y
and Bi1.8Pb0.4Sr2Ca2.5Cu3.5O
y
were obtained by a solid-state reaction in air. Samples with the third nominal composition showed the best superconducting properties (T
on=111 K and zero resistance atT
0=103 K). A possible mechanism for the 2223 phase formation in the three investigated compositions has been discussed. 相似文献