全文获取类型
收费全文 | 208662篇 |
免费 | 2238篇 |
国内免费 | 370篇 |
专业分类
电工技术 | 3075篇 |
综合类 | 749篇 |
化学工业 | 31001篇 |
金属工艺 | 10025篇 |
机械仪表 | 6554篇 |
建筑科学 | 3818篇 |
矿业工程 | 2274篇 |
能源动力 | 3087篇 |
轻工业 | 10647篇 |
水利工程 | 3310篇 |
石油天然气 | 8740篇 |
武器工业 | 16篇 |
无线电 | 16206篇 |
一般工业技术 | 41455篇 |
冶金工业 | 47642篇 |
原子能技术 | 7106篇 |
自动化技术 | 15565篇 |
出版年
2018年 | 3417篇 |
2017年 | 3752篇 |
2016年 | 4375篇 |
2015年 | 2441篇 |
2014年 | 3361篇 |
2013年 | 6727篇 |
2012年 | 6368篇 |
2011年 | 7730篇 |
2010年 | 5056篇 |
2009年 | 5614篇 |
2008年 | 5505篇 |
2007年 | 5459篇 |
2006年 | 4682篇 |
2005年 | 7091篇 |
2004年 | 6146篇 |
2003年 | 5524篇 |
2002年 | 4276篇 |
2001年 | 4184篇 |
2000年 | 3624篇 |
1999年 | 3779篇 |
1998年 | 12653篇 |
1997年 | 8603篇 |
1996年 | 6132篇 |
1995年 | 4265篇 |
1994年 | 3586篇 |
1993年 | 3718篇 |
1992年 | 2476篇 |
1991年 | 2585篇 |
1990年 | 2685篇 |
1989年 | 2566篇 |
1988年 | 2575篇 |
1987年 | 2387篇 |
1986年 | 2413篇 |
1985年 | 2437篇 |
1984年 | 2266篇 |
1983年 | 2203篇 |
1982年 | 2103篇 |
1981年 | 2356篇 |
1980年 | 2233篇 |
1979年 | 2322篇 |
1978年 | 2515篇 |
1977年 | 3002篇 |
1976年 | 4334篇 |
1975年 | 2331篇 |
1974年 | 2340篇 |
1973年 | 2382篇 |
1972年 | 2193篇 |
1971年 | 1952篇 |
1970年 | 1732篇 |
1969年 | 1649篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Fominski V. Yu. Nevolin V. N. Fominski D. V. Romanov R. I. Gritskevich M. D. 《Technical Physics Letters》2020,46(1):83-86
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air... 相似文献
82.
Ugur Gezer Ebru E. Y?rüker Metin Keskin Cemil Burak Kulle Yoganiranjana Dharuman Stefan Holdenrieder 《International journal of molecular sciences》2015,16(12):29654-29662
Circulating nucleic acids (CNAs) are under investigation as a liquid biopsy in cancer as potential non-invasive biomarkers, as stable structure in circulation nucleosomes could be valuable sources for detection of cancer-specific alterations in histone modifications. Our interest is in histone methylation marks with a focus on colorectal cancer, one of the leading cancers respective the incidence and mortality. Our previous work included the analysis of trimethylations of lysine 9 on histone 3 (H3K9me3) and of lysine 20 on histone 4 (H4K20me3) by chromatin immuno- precipitation-related PCR in circulating nucleosomes. Here we asked whether global immunologic measurement of histone marks in circulation could be a suitable approach to show their potential as biomarkers. In addition to H3K9me3 and H4K20me3 we also measured H3K27me3 in plasma samples from CRC patients (n = 63) and cancer free individuals (n = 40) by ELISA-based methylation assays. Our results show that of three marks, the amounts of H3K27me3 (p = 0.04) and H4K20me3 (p < 0.001) were significantly lower in CRC patients than in healthy controls. For H3K9me3 similar amounts were measured in both groups. Areas under the curve (AUC) in receiver operating characteristic (ROC) curves indicating the power of CRC detection were 0.620 for H3K27me3, 0.715 for H4K20me3 and 0.769 for the combination of both markers. In conclusion, findings of this preliminary study reveal the potential of blood-based detection of CRC by quantification of histone methylation marks and the additive effect of the marker combination. 相似文献
83.
84.
85.
Verbovitskii Yu. V. Denis R. V. Shtender V. V. Zavalii I. Yu. 《Powder Metallurgy and Metal Ceramics》2015,54(3-4):220-226
Powder Metallurgy and Metal Ceramics - Multiphase La 2 MgNi 9 alloys are synthesized by induction melting. The crystalline structures of all phases in the alloys are determined with X-ray... 相似文献
86.
87.
88.
Adem Sreedhar I. Neelakanta Reddy Qui Thanh Hoai Ta Gitae Namgung Eunbin Cho Jin-Seo Noh 《Ceramics International》2019,45(6):6985-6993
In this paper, novel morphology correlation between silver nanowires (AgNWs) and cobalt (Co)-doped ZnO (Co-ZnO) flake-like thin films (nanowire/flake-like) has been proposed for enhanced photoelectrochemical (PEC) water splitting activity. Here in, high-quality AgNWs/Co-ZnO heterostructures enabled superior visible light water splitting activity compared to the pure ZnO and AgNWs/ZnO. To address the strategic effect of AgNWs coupling and transition metal (Co-2?at%) doping into the ZnO host lattice, we have carried out the X-ray diffraction, field emission scanning microscopy, X-ray photoelectron spectroscopy, UV–Vis transmittance, water contact angle and PEC analyses. In this way, PEC water splitting activity was mainly examined by linear sweep voltammetry (I-V), amperometric I-t and photoconversion efficiency (η) studies. The experimental results provide clear evidence of morphology correlation between AgNWs and Co-ZnO flake-like structures for strong visible light absorption. Specifically, AgNWs/Co-ZnO composites exhibited significant enhancement in the photocurrent density (7.0?×?10?4 A/cm2) than AgNWs/ZnO (3.2?×?10?4 A/cm2) and pure ZnO (1.5?×?10?6 A/cm2). As a result, detailed AgNWs/Co-ZnO geometry has great potential for photoconversion efficiency (0.73%). In a word, the merits of controllable AgNWs/Co-ZnO heterostructure are proposed to improve the visible light harvesting and charge carrier generation for energy conversion devices. 相似文献
89.
Metallurgist - Kinetics of austenite grain growth within a heat-affected zone is studied for low carbon low-alloy steels of different alloying composition. The effect of Ti/N ratio on the metal... 相似文献
90.
I. P. Ivanchenko A. N. Prokopenko 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2020,53(6):671-680
Equipment of the Krasnoyarsk HPP is considered as an example to analyze the dependence of crack formation in runner blades on the operating conditions of t 相似文献