全文获取类型
收费全文 | 507945篇 |
免费 | 7699篇 |
国内免费 | 1626篇 |
专业分类
电工技术 | 9450篇 |
综合类 | 739篇 |
化学工业 | 75930篇 |
金属工艺 | 16871篇 |
机械仪表 | 14489篇 |
建筑科学 | 13442篇 |
矿业工程 | 1315篇 |
能源动力 | 14437篇 |
轻工业 | 52361篇 |
水利工程 | 4182篇 |
石油天然气 | 5306篇 |
武器工业 | 13篇 |
无线电 | 65206篇 |
一般工业技术 | 94159篇 |
冶金工业 | 95416篇 |
原子能技术 | 7844篇 |
自动化技术 | 46110篇 |
出版年
2021年 | 3680篇 |
2020年 | 2762篇 |
2019年 | 3451篇 |
2018年 | 5613篇 |
2017年 | 5496篇 |
2016年 | 5899篇 |
2015年 | 4310篇 |
2014年 | 7359篇 |
2013年 | 23980篇 |
2012年 | 12669篇 |
2011年 | 17890篇 |
2010年 | 13918篇 |
2009年 | 15896篇 |
2008年 | 16732篇 |
2007年 | 16732篇 |
2006年 | 15096篇 |
2005年 | 13806篇 |
2004年 | 13446篇 |
2003年 | 13132篇 |
2002年 | 12542篇 |
2001年 | 13013篇 |
2000年 | 12111篇 |
1999年 | 13004篇 |
1998年 | 31017篇 |
1997年 | 21975篇 |
1996年 | 16958篇 |
1995年 | 13073篇 |
1994年 | 11645篇 |
1993年 | 11341篇 |
1992年 | 8299篇 |
1991年 | 7915篇 |
1990年 | 7617篇 |
1989年 | 7365篇 |
1988年 | 7127篇 |
1987年 | 5905篇 |
1986年 | 5918篇 |
1985年 | 7108篇 |
1984年 | 6406篇 |
1983年 | 5956篇 |
1982年 | 5408篇 |
1981年 | 5589篇 |
1980年 | 5167篇 |
1979年 | 4966篇 |
1978年 | 4616篇 |
1977年 | 5506篇 |
1976年 | 7032篇 |
1975年 | 3961篇 |
1974年 | 3748篇 |
1973年 | 3814篇 |
1972年 | 3044篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
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
142.
143.
Detailed study on fusion characteristics of rigid poly(vinyl chloride) nanocomposites: The comparison of using multiple regression analysis and artificial neural network 下载免费PDF全文
Fusion behavior of poly(vinyl chloride) (PVC) compounds plays an important role in the development of physical properties of processed material. The fusion characteristics in PVC processing are governed by material variables that affect the fusion with some interactions. In this research, the aim was to characterize the effects of formulation ingredients on fusion characteristics of PVC. Four material parameters, including the contents of nanoclay (NC), azodicarbonamide, calcium stearate, and processing aid, are proposed as affecting variables. The fusion time (FT) as well as fusion factor (FF) are considered fusion indicators and are experimentally determined in some different levels of affecting parameters. The multivariable regression analysis (MRA) and the Artificial Neural Network (ANN) modeling are considered as two analytical methods. The regression analysis result for the FT denotes, in part, significant linear and quadratic effects of NC and also its significant interactions with azodicarbonamide and calcium stearate, whereas that of FF indicates only a linear effect of NC. ANN modeling is performed with a three‐layer (input, hidden, and output) neural network. The results of the comparison of the MRA and ANN predictions with experimental values are reported as the correlation coefficient (R2), mean‐square error, and mean absolute percentage error for both FF and FT parameters. The obtained values clearly denote that the ANN results are more precise and especially more general than those of MRA. However, in the case of FT, improvement of the ANN modeling is much greater than that of FF. J. VINYL ADDIT. TECHNOL., 21:147–155, 2015. © 2014 Society of Plastics Engineers 相似文献
144.
Jasmin Kuhn Philipp M. Klein Nader Al Danaf Joel Z. Nordin Sren Reinhard Dominik M. Loy Miriam Hhn Samir El Andaloussi Don C. Lamb Ernst Wagner Yoshitsugu Aoki Taavi Lehto Ulrich Lchelt 《Advanced functional materials》2019,29(48)
Phosphorodiamidate morpholino oligomers (PMOs) are oligonucleotide analogs that can be used for therapeutic modulation of pre‐mRNA splicing. Similar to other classes of nucleic acid‐based therapeutics, PMOs require delivery systems for efficient transport to the intracellular target sites. Here, artificial peptides based on the oligo(ethylenamino) acid succinyl‐tetraethylenpentamine (Stp), hydrophobic modifications, and an azide group are presented, which are used for strain‐promoted azide‐alkyne cycloaddition conjugation with splice‐switching PMOs. By systematically varying the lead structure and formulation, it is determined that the type of contained fatty acid and supramolecular assembly have a critical impact on the delivery efficacy. A compound containing linolenic acid with three cis double bonds exhibits the highest splice‐switching activity and significantly increases functional protein expression in pLuc/705 reporter cells in vitro and after local administration in vivo. Structural and mechanistic studies reveal that the lipopeptide PMO conjugates form nanoparticles, which accelerate cellular uptake and that the content of unsaturated fatty acids enhances endosomal escape. In an in vitro Duchenne muscular dystrophy exon skipping model using H2K‐mdx52 dystrophic skeletal myotubes, the highly potent PMO conjugates mediate significant splice‐switching at very low nanomolar concentrations. The presented aminoethylene‐lipopeptides are thus a promising platform for the generation of PMO‐therapeutics with a favorable activity/toxicity profile. 相似文献
145.
146.
The 2011 AASHTO Roadside Design Guide (RDG) contains perhaps the most widely used procedure for choosing an appropriate length of need (LON) for roadside barriers. However, this procedure has several limitations. The procedure uses a highly simplified model of vehicle departure, and the procedure does not allow designers to specify an explicit level of protection. A new procedure for choosing LON that addresses these limitations is presented in this paper. This new procedure is based on recent, real-world road departure trajectories and uses this departure data in a more realistic way. The new procedure also allows LON to be specified for a precisely known level of protection – a level which can be based on number of crashes, injury outcomes or even estimated crash cost – while still remaining straightforward and quick to use like the 2011 RDG procedure. 相似文献
147.
148.
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
149.
150.