全文获取类型
收费全文 | 428377篇 |
免费 | 7661篇 |
国内免费 | 1394篇 |
专业分类
电工技术 | 7987篇 |
综合类 | 400篇 |
化学工业 | 65878篇 |
金属工艺 | 14707篇 |
机械仪表 | 12240篇 |
建筑科学 | 12460篇 |
矿业工程 | 969篇 |
能源动力 | 11423篇 |
轻工业 | 46254篇 |
水利工程 | 3446篇 |
石油天然气 | 1870篇 |
武器工业 | 13篇 |
无线电 | 56349篇 |
一般工业技术 | 80672篇 |
冶金工业 | 75770篇 |
原子能技术 | 5673篇 |
自动化技术 | 41321篇 |
出版年
2021年 | 3101篇 |
2020年 | 2133篇 |
2019年 | 2762篇 |
2018年 | 4429篇 |
2017年 | 4473篇 |
2016年 | 4789篇 |
2015年 | 3968篇 |
2014年 | 6395篇 |
2013年 | 20644篇 |
2012年 | 11014篇 |
2011年 | 15692篇 |
2010年 | 12130篇 |
2009年 | 13629篇 |
2008年 | 14744篇 |
2007年 | 15079篇 |
2006年 | 13403篇 |
2005年 | 12442篇 |
2004年 | 11966篇 |
2003年 | 11669篇 |
2002年 | 11323篇 |
2001年 | 11442篇 |
2000年 | 10539篇 |
1999年 | 10970篇 |
1998年 | 24178篇 |
1997年 | 17763篇 |
1996年 | 14064篇 |
1995年 | 11140篇 |
1994年 | 9908篇 |
1993年 | 9470篇 |
1992年 | 7234篇 |
1991年 | 6891篇 |
1990年 | 6505篇 |
1989年 | 6194篇 |
1988年 | 5946篇 |
1987年 | 4963篇 |
1986年 | 4895篇 |
1985年 | 6107篇 |
1984年 | 5745篇 |
1983年 | 4924篇 |
1982年 | 4606篇 |
1981年 | 4554篇 |
1980年 | 4295篇 |
1979年 | 4167篇 |
1978年 | 3852篇 |
1977年 | 4610篇 |
1976年 | 6156篇 |
1975年 | 3199篇 |
1974年 | 3064篇 |
1973年 | 2949篇 |
1972年 | 2353篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Kevin J. Hanley 《International journal for numerical methods in engineering》2020,121(21):4865-4877
An algorithm is presented for discrete element method simulations of energy-conserving systems of frictionless, spherical particles in a reversed-time frame. This algorithm is verified, within the limits of round-off error, through implementation in the LAMMPS code. Mechanisms for energy dissipation such as interparticle friction, damping, rotational resistance, particle crushing, or bond breakage cannot be incorporated into this algorithm without causing time irreversibility. This theoretical development is applied to critical-state soil mechanics as an exemplar. It is shown that the convergence of soil samples, which differ only in terms of their initial void ratio, to the same critical state requires the presence of shear forces and frictional dissipation within the soil system. 相似文献
52.
53.
Gökelma Mertol Einarsrud Kristian Etienne Tranell Gabriella Friedrich Bernd 《Metallurgical and Materials Transactions B》2020,51(2):850-860
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of... 相似文献
54.
J. Cochard P. Léonide J. Borgomano Y. Guglielmi G. Massonnat J-P. Rolando L. Marié A. Pasquier 《Journal of Petroleum Geology》2020,43(1):75-94
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation. 相似文献
55.
56.
57.
58.
Sarah Gilgunn Keefe Murphy Henning Stckmann Paul J. Conroy T. Brendan Murphy R. William Watson Richard J. OKennedy Pauline M. Rudd Radka Saldova 《International journal of molecular sciences》2020,21(23)
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies. 相似文献
59.
60.