全文获取类型
收费全文 | 3968篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 154篇 |
金属工艺 | 9篇 |
机械仪表 | 17篇 |
建筑科学 | 32篇 |
矿业工程 | 3篇 |
能源动力 | 37篇 |
轻工业 | 53篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 157篇 |
一般工业技术 | 135篇 |
冶金工业 | 3223篇 |
原子能技术 | 14篇 |
自动化技术 | 130篇 |
出版年
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2017年 | 14篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 64篇 |
2012年 | 31篇 |
2011年 | 32篇 |
2010年 | 19篇 |
2009年 | 25篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 34篇 |
2005年 | 24篇 |
2004年 | 33篇 |
2003年 | 27篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 114篇 |
1998年 | 917篇 |
1997年 | 520篇 |
1996年 | 360篇 |
1995年 | 209篇 |
1994年 | 195篇 |
1993年 | 217篇 |
1992年 | 31篇 |
1991年 | 51篇 |
1990年 | 50篇 |
1989年 | 50篇 |
1988年 | 59篇 |
1987年 | 48篇 |
1986年 | 49篇 |
1985年 | 54篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 38篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 103篇 |
1976年 | 237篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1970年 | 6篇 |
1968年 | 5篇 |
排序方式: 共有3992条查询结果,搜索用时 804 毫秒
31.
32.
33.
34.
J. Tomiska K. Kopecky M. S. Belegratis C. Myers 《Metallurgical and Materials Transactions A》1995,26(2):259-265
Thermodynamic excess functions of nickel-chromium alloys in the body-centered cubic (bcc) phase have been investigated by
computer-aided Knudsen cell mass spectrometry in the tem-perature range of 1300 to 1650 K. Activities, as well as molar excess
Gibbs energies, enthalpies, and entropies, were obtained from the ion intensities as a function of composition by fitting
to a subregular solution model [2-parameter thermodynamically adapted power (TAP) series:C
H
n
in J/mol,C
H
1
= 3900,C
H
1
= 44,610;C
S
n
in J/mol-K,C = 9.71, c= 13.52]. Based upon these data, the phase diagram has been recalculated. 相似文献
35.
36.
37.
The treatment of patients with uterine neoplasms may be significantly altered by the stage of disease at the time of diagnosis. A noninvasive and accurate means of staging these tumors is therefore desirable. This article discusses the magnetic resonance imaging techniques and findings that are essential for the accurate staging of uterine neoplasms. The imaging findings are presented following a discussion of the histopathologic findings, clinical presentation, diagnosis and staging, pathways of tumor spread, and treatment of each neoplasm. A comparison of magnetic resonance and other imaging techniques is also provided. 相似文献
38.
JN Myers 《Canadian Metallurgical Quarterly》1994,21(3):415-437
39.
40.
OBJECTIVE: Microvascular pericytes may contract in two different ways: In the first, a circumferential or radial mechanical force applied at right angles to the long axis of the vessel may constrict the underlying vessel affecting blood flow and transmural pressure. Retraction and elongation of pericyte processes may also occur tangentially and at right angles to the vessel axis and alter microvessel permeability by changing the amount of ablumenal surface covered or the openness of interendothelial junctions. In this study, cultured pericytes were utilized as a model experimental system to determine if vasoactive stimulation changes their shape in a manner consistent with this hypothesis. METHODS: Pericytes cultured from isolated rate capillaries were subjected to angiotensin II and histamine. Their response was monitored by measuring the area of non-yielding substrate covered by the pericytes and the manner in which their shape changed. Shape changes were quantified by calculating the surface area: perimeter perimeter ratios. RESULTS: Histamine significantly reduced surface area covered and the surface area:perimeter ratio. The pericyte processes retracted, resulting in elongated, spindle-shaped cells. These effects were nullified by the H1 blocker diphenhydramine suggesting a receptor-specific response. Angiotensin II also elicited contraction and reduced surface area, but the cells contracted laterally and longitudinally. The surface area: perimeter ratios also decreased. CONCLUSIONS: These results indicate that pericytes are capable of two types of contractile responses in culture, depending on the specific vasoactive stimulus. 相似文献