全文获取类型
收费全文 | 1491篇 |
免费 | 6篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 74篇 |
金属工艺 | 4篇 |
机械仪表 | 9篇 |
建筑科学 | 13篇 |
矿业工程 | 2篇 |
能源动力 | 6篇 |
轻工业 | 26篇 |
水利工程 | 9篇 |
无线电 | 34篇 |
一般工业技术 | 70篇 |
冶金工业 | 1148篇 |
原子能技术 | 7篇 |
自动化技术 | 83篇 |
出版年
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 9篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 15篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 38篇 |
1998年 | 340篇 |
1997年 | 203篇 |
1996年 | 135篇 |
1995年 | 78篇 |
1994年 | 64篇 |
1993年 | 87篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 37篇 |
1976年 | 75篇 |
1975年 | 8篇 |
1970年 | 2篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有1497条查询结果,搜索用时 453 毫秒
51.
Urinary amino acid excretion was determined in 31 leukemic patients and 29 normal individuals by rapid gas chromatographic analysis of 16 amino acids as their N-acetyl-n-propyl esters. The leukemic patients were concurrently undergoing, or had recently completed, chemotherapy. It was found that aspartic acid, threonine, and serine were of significance in distinguishing between patients "on" therapy and those "off" therapy. Patients with advanced disease have the greatest aminoaciduria, although both the normal and leukemic populations have wide individual ranges. Within both populations, men excrete a greater variety and quantity of amino acids than women. It is concluded that analysis of urinary amino acids represents a history of complex metabolic events, which is potentially useful for evaluating patient response to chemotherapy in leukemia. 相似文献
52.
53.
This paper deals with two similar inequalities:
where K denotes simple Kolmogorov entropy (i.e., the very first version of Kolmogorov complexity having been introduced by Kolmogorov
himself) and KP denotes prefix entropy (self-delimiting complexity by the terminology of Li and Vitanyi [1]). It turns out that from (1)
the following well-known geometric fact can be inferred:
where V is a set in three-dimensional space, S
xy
, S
yz
, S
xz
are its three two-dimensional projections, and |W| is the volume (or the area) of W . Inequality (2), in its turn, is a corollary of the well-known Cauchy—Schwarz inequality. So the connection between geometry
and Kolmogorov complexity works in both directions.
Received April 20, 1993, and in final form December 6, 1993. 相似文献
54.
A new imaging system for 1 MA scale wire-array Z-pinch experiments that produces up to five high-resolution x-ray images per experimental pulse has been developed. Calibrated areal density measurements of the Z-pinch plasma can be obtained from each pulse. The system substitutes five molybdenum (Mo) X pinches for the normal copper return-current conductors to provide point sources of x-rays for point-projection radiography. Each backlighting X pinch consists of four Mo wires, the x-ray burst timing of which was controlled by varying the wire diameter (mass) from 10.2 to 30 microm in the five X pinches. Typical images have a 16x8 mm2 field of view at the wire array and a magnification of about 6.5:1 on the x-ray-sensitive film. Titanium (Ti) filters in front of the films transmit continuum radiation in the spectral range of 3-5 keV. Inclusion on the Ti of a step wedge having known thickness increments of the same material as the wires enables the calibrated areal density measurements to be made of the exploding wire plasmas. Here, we used tungsten (W) step wedges with step thicknesses ranging from 0.015 to 1.1 microm to obtain accurate (+/-10%) areal density measurements of W plasmas from the spatial profile of film exposure. When imaging arrays that produce intense radiation pulses, a plastic monofilament "quencher" is placed on axis to avoid film saturation. Images have subnanosecond temporal resolution and about 7 microm spatial resolution. 相似文献
55.
56.
57.
58.
59.
Prof. Dr. Andreas Leson Gregor Englberger Daniel Hammer Stefan Makowski Carl‐Friedrich Meyer Michael Leonhard Hans‐Joachim Scheibe Volker Weihnacht 《真空研究与实践》2015,27(4):24-28
Diamond‐like carbon thin films enhance efficiency — laser arc deposition of ta‐C Rising prices for fossil fuels as well as the increasing effects of the climate change due to the emission of greenhouse gases reveal the necessity of saving energy. Low friction coatings have an enormous potential in saving energy. Carbon based coatings — named as DLC coatings — are especially well suited for low friction coatings. In particular hydrogen‐free tetrahedral amorphous carbon (ta‐C) coatings are of great interest due to their extraordinary low wear properties. In addition they show excellent low friction properties and especially in combination with specific lubricants the so‐called super low friction effect. For the deposition of ta‐C coatings PVD methods have to be applied instead of CVD methods as it is the case for conventional DLC coatings. We have developed a deposition method which is based on a pulsed arc steered by a laser (Laser‐Arc). This allows us to use large cathodes resulting in a high long‐term stability. Furthermore, the carbon plasma source can be combined with a filtering unit removing almost all droplets and particles, which usually are characteristic for an arc process. The resulting Laser‐Arc source allows for the deposition of smooth and virtually defect‐free ta‐C coatings with a competitive deposition rate. 相似文献
60.
Florenza Lüder Ripoli Annika Mohr Susanne Conradine Hammer Saskia Willenbrock Marion Hewicker-Trautwein Silvia Hennecke Hugo Murua Escobar Ingo Nolte 《International journal of molecular sciences》2016,17(5)
Mammary neoplasms are the tumors most affecting female dogs and women. Formalin-fixed, paraffin-embedded (FFPE) tissues are an invaluable source of archived biological material. Fresh frozen (FF) tissue is considered ideal for gene expression analysis. However, strategies based on FFPE material offer several advantages. Branched-DNA assays permit a reliable and fast workflow when analyzing gene expression. The aim of this study was to assess the comparability of the branched-DNA assay when analyzing certain gene expression patterns between FF and FFPE samples in canine mammary tumors. RNA was isolated from 109 FFPE samples and from 93 FF samples of different canine mammary tissues. Sixteen (16) target genes (Tp53; Myc; HMGA1; Pik3ca; Mcl1; MAPK3; FOXO3; PTEN; GATA4; PFDN5; HMGB1; MAPK1; BRCA2; BRCA1; HMGA2; and Her2) were analyzed via branched-DNA assay (b-DNA). ACTB, GAPDH, and HPRT1 were used as data normalizers. Overall, the relative gene expression of the two different origins of samples showed an agreement of 63%. Still, care should be taken, as FFPE specimens showed lower expression of the analyzed targets when compared to FF samples. The fact that the gene expression in FFPE proved to be lower than in FF specimens is likely to have been caused by the effect of storage time. ACTB had the best performance as a data normalizer. 相似文献