全文获取类型
收费全文 | 22447篇 |
免费 | 2460篇 |
国内免费 | 1412篇 |
专业分类
电工技术 | 1479篇 |
技术理论 | 1篇 |
综合类 | 2167篇 |
化学工业 | 3651篇 |
金属工艺 | 805篇 |
机械仪表 | 968篇 |
建筑科学 | 3067篇 |
矿业工程 | 499篇 |
能源动力 | 1066篇 |
轻工业 | 2835篇 |
水利工程 | 362篇 |
石油天然气 | 212篇 |
武器工业 | 60篇 |
无线电 | 1996篇 |
一般工业技术 | 2728篇 |
冶金工业 | 568篇 |
原子能技术 | 131篇 |
自动化技术 | 3724篇 |
出版年
2024年 | 119篇 |
2023年 | 693篇 |
2022年 | 998篇 |
2021年 | 1200篇 |
2020年 | 1210篇 |
2019年 | 848篇 |
2018年 | 782篇 |
2017年 | 876篇 |
2016年 | 921篇 |
2015年 | 1016篇 |
2014年 | 1869篇 |
2013年 | 1932篇 |
2012年 | 2382篇 |
2011年 | 2325篇 |
2010年 | 1817篇 |
2009年 | 1857篇 |
2008年 | 1161篇 |
2007年 | 1162篇 |
2006年 | 872篇 |
2005年 | 404篇 |
2004年 | 189篇 |
2003年 | 175篇 |
2002年 | 196篇 |
2001年 | 179篇 |
2000年 | 162篇 |
1999年 | 139篇 |
1998年 | 129篇 |
1997年 | 91篇 |
1996年 | 97篇 |
1995年 | 78篇 |
1994年 | 48篇 |
1993年 | 53篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 13篇 |
1988年 | 26篇 |
1987年 | 89篇 |
1986年 | 78篇 |
1985年 | 18篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
51.
52.
53.
罗立祝 《机械工业高教研究》2008,(2):106-110
从高校招生的演变历史看,中国在1978年以前对工农阶层子女实行高校入学优惠政策主要源于国家对这一阶层的特殊偏好而实行平均主义分配政策所致。国家通过报考资格政策、优先录取政策和免试推荐入学政策人为地大幅度提高了工农阶层子女在高校大学生中所占的比例。从公平视角看,这项政策不仅违背了公平原则,而且降低了人才选拔的质量。 相似文献
54.
55.
A novel finger‐sensing nanocomposite with remarkable and reversible piezoresistivity is successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GNs) in a silicone rubber (SR) matrix. Because of the high aspect ratio of the graphite nanosheets, the nanocomposite displays a very low percolation threshold. The SR/GN nanocomposite with a volume fraction of conductive nanosheets closest to that for the percolation threshold presents a sharp positive‐pressure coefficient effect of the resistivity under very low pressure, namely, in the finger‐pressure range (0.3–0.7 MPa), whereby the abrupt transition could be attributed to compressive‐stress‐induced deformation of the conducting network. The super‐sensitive piezoresistive behavior of the nanocomposite is accounted for by an extension of the tunneling conduction theory which provides a good approximation to the piezoresistive effect. 相似文献
56.
The Jian kiln, located in present-day Jianyang county of Fujian province, mainly produced black-glazed tea bowls. Jian tea bowl was used as a utensil for tea tasting and was greatly appreciated by emperor Huizong of the Northern Song dynasty. The black glaze of Jian bowl was sometimes marked with streaks or spots, usually called “hare's fur” or “oil spot”, which are the crystalline markings of iron oxide precipitated during firing in the dragon kiln. In this study, black-glazed Jian bowl sherds excavated from the late Northern Song strata of Luhuaping and Daluhoumen Jian kiln sites were adopted as test samples. Based on the physico-chemical foundation for the formation of glaze microstructure, the correlation among composition, microstructure, and visual appearance has been investigated by means of energy-dispersive X-ray fluorescence, X-ray diffraction, and field emission electron microscopy. For the first time, the study provides realizing proofs for two kinds of microstructural forming mechanics. 相似文献
57.
The present study is an investigation on the behaviors of concrete-filled thin-walled steel tubular members subjected to combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. ABAQUS software is used in this paper for the finite element analysis (FEA). A comparison of results calculated using this modeling shows generally good agreement with test results. The FEA modeling is then used to investigate the influence of important parameters that determine the ultimate strength of the composite members under combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. The parametric studies provide information for the development of formulae for calculating the ultimate strength of the composite members subjected to combined loading. 相似文献
58.
合同管理是建设工程项目管理的一项重要内容。周宁水电站建设单位通过加强工程招标、合同变更处理、索赔处理、工程价款审核与支付及竣工结算等方面的管理工作,使土建工程造价得到了控制,同时也保证了工程进度、质量目标的实现。 相似文献
59.
《Computers & Mathematics with Applications》2007,53(1):104-114
This paper deals with the generalization and sharp versions of the Wolstenholme cyclic inequality and their applications. The inequalities of this paper improve and unify corresponding known results. Several interesting inequalities including the celebrated Ozeki inequality are obtained. Extensions of the Wolstenholme inequality for a complex polygon and the Wolstenholme inequality for a convex quadrilateral are derived. As example of applications, the well-known Erdös–Mordell inequality is improved in this paper. In addition, several extensions, unifications and refinements of Gueron–Shafrir’s inequalities and Mitrinović–Pecaric’s inequality are established. 相似文献
60.
FD Fuchs 《Canadian Metallurgical Quarterly》1996,67(4):267-269
We have treated 50 patients with stage III, VI malignant tumors confirmed by pathology. The patients were divided into two groups. One group was treated by combination of chemotherapy and traditional Chinese medicine (treatment group); the other only by chemotherapy (control group). The effect of cancer treatment was evaluated according to the criteria of WHO. The results showed that the effective rate was 80% in treatment group and 52% in control group. The pain relieving rate was 68% in treatment group and 40% in control group (P < 0.01). This fact demonstrates that the application of traditional Chinese medicine can invigorate blood circulation, eliminate blood stasis, soften hardness and dissolve the mass, nourish blood and increase vigor. This kind of application can not only enhance the effect of cancer treatment but also increase the cancer pain relieving rate. 相似文献