全文获取类型
收费全文 | 1564647篇 |
免费 | 24786篇 |
国内免费 | 7028篇 |
专业分类
电工技术 | 34611篇 |
综合类 | 6455篇 |
化学工业 | 274093篇 |
金属工艺 | 64979篇 |
机械仪表 | 44183篇 |
建筑科学 | 47345篇 |
矿业工程 | 11557篇 |
能源动力 | 50399篇 |
轻工业 | 119858篇 |
水利工程 | 15725篇 |
石油天然气 | 37836篇 |
武器工业 | 150篇 |
无线电 | 198037篇 |
一般工业技术 | 292151篇 |
冶金工业 | 193412篇 |
原子能技术 | 34234篇 |
自动化技术 | 171436篇 |
出版年
2021年 | 15609篇 |
2020年 | 11968篇 |
2019年 | 14704篇 |
2018年 | 17161篇 |
2017年 | 16487篇 |
2016年 | 22062篇 |
2015年 | 17551篇 |
2014年 | 28790篇 |
2013年 | 88086篇 |
2012年 | 37063篇 |
2011年 | 50643篇 |
2010年 | 43931篇 |
2009年 | 51844篇 |
2008年 | 46919篇 |
2007年 | 44296篇 |
2006年 | 45876篇 |
2005年 | 40878篇 |
2004年 | 42778篇 |
2003年 | 42525篇 |
2002年 | 41360篇 |
2001年 | 38518篇 |
2000年 | 36728篇 |
1999年 | 36378篇 |
1998年 | 54834篇 |
1997年 | 45155篇 |
1996年 | 39058篇 |
1995年 | 32874篇 |
1994年 | 30511篇 |
1993年 | 30464篇 |
1992年 | 26681篇 |
1991年 | 23775篇 |
1990年 | 24072篇 |
1989年 | 23158篇 |
1988年 | 21651篇 |
1987年 | 19920篇 |
1986年 | 19234篇 |
1985年 | 22544篇 |
1984年 | 22508篇 |
1983年 | 20456篇 |
1982年 | 19442篇 |
1981年 | 19612篇 |
1980年 | 18202篇 |
1979年 | 18621篇 |
1978年 | 17908篇 |
1977年 | 18074篇 |
1976年 | 19713篇 |
1975年 | 16070篇 |
1974年 | 15543篇 |
1973年 | 15659篇 |
1972年 | 13122篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
124.
125.
V. N. Tsygankov V. V. Safonov A. I. Kozlov V. P. Gavrilov 《Inorganic Materials》2003,39(10):1076-1078
The GeO2–NiO system is studied in the stability range of Ni2GeO4 by temperature-dependent resistivity measurements, in combination with x-ray diffraction, differential thermal analysis, and thermogravimetry. The resistivity of the starting mixtures and heat-treated samples is measured in the composition range 55–90 mol % NiO. The effect of air humidity on the resistivity of the samples is examined. 相似文献
126.
A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid
meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising
the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model
is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated
by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation.
The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest.
Sponsored by The Research Council of Norway, project number 125676/410
Dedicated to the memory of Prof. Mike Crisfield, a respected colleague 相似文献
127.
The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture. 相似文献
128.
This study investigates the citation patterns in the journal, Medical Principles and Practice from its inception in 1989 through 2000 (volumes 1-9). The data set includes 4740 references appended to the 221 original
research articles. All of the citations were entered into a ProCite database for analysis. Specifically, this study addresses:
(1) bibliometric patterns of cited works in terms of publication format, subject scatter, authorship characteristics, age
of citations, geographic distribution, and language distribution; (2) productivity of journal titles; (3) the role of self-citation;
and (4) how selected bibliometric indicators apply. Some of the findings include: journal articles are most frequently cited;
English language publications dominate the literature; there is a trend of multiple authorship; and the pattern of aging is
below the norm for medical literature. The results of the study can provide a benchmark to measure the user behavior of a
particular group of researchers as well as for the provision of collection development and management decisions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
129.
C. Thibeault 《Journal of Electronic Testing》2003,19(6):625-635
The purpose of this paper is to introduce a new I
DDQ measurement technique based on active successive approximations, called ASA-I
DDQ. This technique has unique features facilitating a speed-up in I
DDQ measurement. Experimental results suggest that a significant speed-up factor (up to 4) can be obtained over the QuiC-Mon technique. Such a speed-up is a key element in the replacement of single-threshold I
DDQ testing since it amplifies the effectiveness of post-processing techniques. 相似文献
130.