全文获取类型
收费全文 | 17235篇 |
免费 | 1076篇 |
国内免费 | 353篇 |
专业分类
电工技术 | 497篇 |
技术理论 | 5篇 |
综合类 | 1573篇 |
化学工业 | 2834篇 |
金属工艺 | 334篇 |
机械仪表 | 644篇 |
建筑科学 | 2263篇 |
矿业工程 | 170篇 |
能源动力 | 374篇 |
轻工业 | 1460篇 |
水利工程 | 207篇 |
石油天然气 | 237篇 |
武器工业 | 132篇 |
无线电 | 1079篇 |
一般工业技术 | 3143篇 |
冶金工业 | 1202篇 |
原子能技术 | 172篇 |
自动化技术 | 2338篇 |
出版年
2024年 | 68篇 |
2023年 | 287篇 |
2022年 | 375篇 |
2021年 | 775篇 |
2020年 | 501篇 |
2019年 | 459篇 |
2018年 | 419篇 |
2017年 | 492篇 |
2016年 | 577篇 |
2015年 | 604篇 |
2014年 | 1103篇 |
2013年 | 1395篇 |
2012年 | 1552篇 |
2011年 | 1055篇 |
2010年 | 919篇 |
2009年 | 1014篇 |
2008年 | 865篇 |
2007年 | 732篇 |
2006年 | 624篇 |
2005年 | 520篇 |
2004年 | 447篇 |
2003年 | 377篇 |
2002年 | 322篇 |
2001年 | 245篇 |
2000年 | 163篇 |
1999年 | 149篇 |
1998年 | 121篇 |
1997年 | 66篇 |
1996年 | 1076篇 |
1995年 | 493篇 |
1994年 | 348篇 |
1993年 | 28篇 |
1992年 | 28篇 |
1991年 | 25篇 |
1990年 | 25篇 |
1989年 | 26篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1985年 | 38篇 |
1984年 | 51篇 |
1983年 | 23篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1964年 | 22篇 |
1961年 | 14篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Syed Jafar Mehdi Hector Rosas-Hernandez Elvis Cuevas Susan M. Lantz Steven W. Barger Sumit Sarkar Merle G. Paule Syed F. Ali Syed Z. Imam 《International journal of molecular sciences》2016,17(9)
Currently, the lack of new drug candidates for the treatment of major neurological disorders such as Parkinson’s disease has intensified the search for drugs that can be repurposed or repositioned for such treatment. Typically, the search focuses on drugs that have been approved and are used clinically for other indications. Kinase inhibitors represent a family of popular molecules for the treatment and prevention of various cancers, and have emerged as strong candidates for such repurposing because numerous serine/threonine and tyrosine kinases have been implicated in the pathobiology of Parkinson’s disease. This review focuses on various kinase-dependent pathways associated with the expression of Parkinson’s disease pathology, and evaluates how inhibitors of these pathways might play a major role as effective therapeutic molecules. 相似文献
992.
以丙酮为溶剂,通过蒸发结晶法制得六硝基六氮杂异伍兹烷(CL-20)/二硝基甲苯(DNT)共晶炸药。利用扫描电镜(SEM)、X射线衍射(XRD)和热重/差示量热法(TGA/DSC)研究了共晶炸药的形貌、结构和热分解特性,测试了CL-20/DNT共晶炸药的机械感度和5s爆发点温度,并计算了其爆轰性能。结果表明,共晶炸药的微观形貌不同于原料CL-20,呈条状晶体;衍射峰明显不同于CL-20/DNT物理混合物的衍射峰,表明有新物相生成。在DSC曲线上,CL-20/DNT共晶几乎没有DNT的熔化吸热峰,而CL-20/DNT物理混合物中有明显的熔化峰,且二者的放热峰峰形和峰位不同;与原料CL-20相比,共晶炸药的分解峰温提前了21℃,放热量(ΔH)和最大热流量(Qmax)分别增加了39%和104%。与CL-20/DNT物理混合物相比,共晶炸药的5s爆发点温度和表观活化能分别增加3.9℃和65.7kJ/mol,撞击感度降低88.9%,摩擦感度降低40%,说明共晶炸药热稳定性增强。CL-20/DNT共晶炸药的理论爆速达到8 340m/s。 相似文献
993.
994.
A mechanism for the dynamic shaft resistance of vertically vibrating single end-bearing and infinitely long piles is proposed through the use of elastodynamics. The generalized expression for the shaft resistance is obtained by means of Hamilton's principle. The shaft resistance is divided analytically into three parts, namely, the Winkler spring, the membrane and the participating mass of the surrounding soil. In light of the contributions of these three components of shaft resistance, a physical model is presented for the nature of single piles subjected to dynamic loading. The three components are obtained as explicit forms. The first is linear to the pile settlement. The second is related to the derivative of the second order of the pile settlement. The third involves the participating mass of the surrounding soil. The effect of the properties of the soil-pile system on the dynamic responses of the characteristic coefficients of the shaft resistance is investigated. The results indicate that the Winkler spring contributes the most to the shaft resistance. The contributions of the membrane and the participating mass of the surrounding soil are negligible for cases of high incident frequency. 相似文献
995.
Debajyoti Bhaduri Pavel Penchev Khamis Essa Stefan Dimov Luke N. Carter Catalin I. Pruncu Daniele Pullini 《CIRP Annals》2019,68(1):237-240
A disadvantage of selective laser melting (SLM) processes for the manufacture of large parts is their slow build time per unit volume. A hybrid route is to generate core simple shapes traditionally, for example by machining, followed by adding final features by SLM. Here the mechanical integrity of such hybrid parts is studied, choosing the building of AlSi10Mg by SLM on a machined AA6082 base, in the shape of a tensile test piece, as a simple example. These materials are chosen for their relevance to lightweight parts. As-built parts fail at the SLM/machined interface but standard heat treatments transfer failures to the machined material. Optimised SLM processing conditions and microstructures of the SLM and interfacial regions are reported. 相似文献
996.
This paper introduces a new methodology to measure the elastic constants of transversely isotropic rocks from a single uniaxial compression test. We first give the mathematical proof that a uniaxial compression test provides only four independent strain equations. As a result, the exact determination of all five independent elastic constants from only one test is not possible. An approximate determination of the Young's moduli and the Poisson's ratios is however practical and efficient when adding the Saint–Venant relation as the fifth equation. Explicit formulae are then developed to calculate both secant and tangent definitions of the five elastic constants from a minimum of four strain measurements. The results of this new methodology applied on three granitic samples demonstrate a significant stress-induced nonlinear behavior, where the tangent moduli increase by a factor of three to four when the rock is loaded up to 20 MPa. The static elastic constants obtained from the uniaxial compression test are also found to be significantly smaller than the dynamic ones obtained from the ultrasonic measurements. 相似文献
997.
错果错-虾姑蛇绿混杂带位于狮泉河-永珠-嘉黎蛇绿混杂岩带中段,与其伴随的复理石是其洋盆沉积的记录,它的时代归属对约束狮泉河-永珠-纳木错弧后小洋盆的演化具有重要意义。本文以狮泉河-永珠-嘉黎蛇绿混杂岩带中段改则县错果错-虾姑蛇绿混杂带虾姑一带的碎屑岩为研究对象,对其进行岩石学和碎屑锆石年代学方面的研究。该区碎屑岩以薄层砂岩和页岩互层为主,具复理石沉积特征。砂岩碎屑锆石年代学分析结果显示,最小碎屑锆石年龄为119Ma,最小年龄峰值为120Ma,指示该地区碎屑岩的时代为早白垩世晚期。结合前人研究,在早白垩世晚期,北部的班公湖-怒江残余洋向南俯冲,南部的雅江洋向北俯冲,加快了中部狮泉河-永珠-纳木错小洋盆俯冲消减,冈底斯岛弧与喀喇昆仑-南羌塘-左贡陆块发生弧-陆碰撞,形成了规模有限的狮泉河-永珠-嘉黎蛇绿岩及早白垩世晚期残留海盆地,在虾姑一带沉积了虾姑碎屑岩,随后闭合,之后沉积了早白垩世末的多尼组和郞山组残海沉积。 相似文献
998.
999.
1000.
通过6根挤扩支盘桩的静载试验和桩身应力及桩端反力测试试验成果,分析挤扩支盘桩在竖向荷载下的变形受力特征,给出了对工程实践有指导意义的结论。 相似文献