全文获取类型
收费全文 | 22728篇 |
免费 | 2260篇 |
国内免费 | 1727篇 |
专业分类
电工技术 | 1164篇 |
技术理论 | 1篇 |
综合类 | 2592篇 |
化学工业 | 3051篇 |
金属工艺 | 1530篇 |
机械仪表 | 1716篇 |
建筑科学 | 1988篇 |
矿业工程 | 1042篇 |
能源动力 | 1366篇 |
轻工业 | 639篇 |
水利工程 | 1433篇 |
石油天然气 | 2205篇 |
武器工业 | 717篇 |
无线电 | 1189篇 |
一般工业技术 | 2999篇 |
冶金工业 | 1219篇 |
原子能技术 | 466篇 |
自动化技术 | 1398篇 |
出版年
2024年 | 63篇 |
2023年 | 267篇 |
2022年 | 547篇 |
2021年 | 596篇 |
2020年 | 672篇 |
2019年 | 578篇 |
2018年 | 589篇 |
2017年 | 757篇 |
2016年 | 926篇 |
2015年 | 848篇 |
2014年 | 1158篇 |
2013年 | 1519篇 |
2012年 | 1485篇 |
2011年 | 1597篇 |
2010年 | 1229篇 |
2009年 | 1267篇 |
2008年 | 1154篇 |
2007年 | 1502篇 |
2006年 | 1398篇 |
2005年 | 1175篇 |
2004年 | 1038篇 |
2003年 | 918篇 |
2002年 | 794篇 |
2001年 | 680篇 |
2000年 | 578篇 |
1999年 | 524篇 |
1998年 | 445篇 |
1997年 | 347篇 |
1996年 | 348篇 |
1995年 | 361篇 |
1994年 | 301篇 |
1993年 | 201篇 |
1992年 | 195篇 |
1991年 | 153篇 |
1990年 | 105篇 |
1989年 | 98篇 |
1988年 | 70篇 |
1987年 | 56篇 |
1986年 | 41篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 3篇 |
1961年 | 2篇 |
1959年 | 15篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
岩石物理横波速度曲线计算技术 总被引:15,自引:3,他引:12
横波速度是地震勘探中的重要参数。针对实际生产中缺乏横波速度测井曲线资料,利用经验公式计算精确度不高的问题,通过对横波速度计算理论模型的研究分析,选择Blot-Gassman模型法,利用岩石矿物成分、流体成分、孔隙度及密度等测井曲线进行横波速度测井曲线的计算,并对横波速度计算技术和流程进行研究。在实际工区进行了横波速度曲线计算,计算结果与实测横波吻合程度较高,误差小于10%,该技术在储层和流体识别预测的应用中取得了较好效果。 相似文献
2.
文章简要分析了我国目前在中硬岩石爆破中工业炸药的使用情况,介绍了山西兴安化学材料厂新研制的一种适用于硬岩爆破的高爆速、高威力水胶炸药新品种,对其性能、爆破效果、经济实用性和安全性等进行了阐述。 相似文献
3.
4.
S N Maitra 《Sadhana》1985,8(4):373-385
The burn time and burnout velocity of a multistage rocket flown vertically in vacuum with constant thrust tangential to the
flight path and a prescribed initial/final thrust-to-weight ratio in an arbitrary stage have been determined.
The present paper also deals with optimal staging under given conditions of flight. 相似文献
5.
6.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
7.
介绍了Robatech公司开发的PFC喷嘴。这种喷嘴为标准化组件,具有较大的适用性,既适用于新厂配套,也适用于老设备改造。 相似文献
8.
In this paper we describe, from a theoretical point of view, critical configurations for the projective reconstruction of
a set of points, for a single view, i.e. for calibration of a camera, in the case of projections from ℙk to ℙ2 for k ≥ 4. We give first a general result describing these critical loci in ℙk, which, if irreducible, are algebraic varieties of dimension k−2 and degree 3. If k=4 they can be either a smooth ruled surface or a cone and if k = 5 they can be a smooth three dimensional variety, ruled in planes, or a cone. If k≥ 6, the variety is always a cone, the
vertex of which has dimension at least k − 6. The reducible cases are studied in Appendix A.
These results are then applied to determine explicitly the critical loci for the projections from ℙk which arise from the dynamic scenes in ℙ3 considered in [13].
Marina Bertolini is currently Associate Professor of Geometry at the Department of Mathematics at the Università degli Studi di Milano, Italy.
Her main field of research is Complex Projective Algebraic Geometry, with particular interest for the classification of projective
varieties and for the geometry of Grassmann varieties. On these topics M. Bertolini has published more than twenty reviewed
papers on national and international journals. She has been for some years now interested also in applications of Algebraic
Geometry to Computer Vision problems.
Cristina Turrini is Associate Professor of Geometry at the Department of Mathematics of Università degli Studi di Milano, Italy. Her main
research interest is Complex Projective Algebraic Geometry: subvarieties of Grassmannians, special varieties, automorphisms,
classification. In the last two years she has started to work on applications of Algebraic Geometry to problems of Computer
Vision. She is author or co-author of about thirty reviewed papers. She is also involved in popularization of Mathematics,
and on this subject she is co-editor of some books. 相似文献
9.
10.
The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium
vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition
points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO3, RbVO3 and CsVO3, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition
temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric
state and depends upon sodium concentration. 相似文献