全文获取类型
收费全文 | 418525篇 |
免费 | 3091篇 |
国内免费 | 1255篇 |
专业分类
电工技术 | 7771篇 |
综合类 | 363篇 |
化学工业 | 62380篇 |
金属工艺 | 14324篇 |
机械仪表 | 11884篇 |
建筑科学 | 11738篇 |
矿业工程 | 870篇 |
能源动力 | 11223篇 |
轻工业 | 44392篇 |
水利工程 | 3559篇 |
石油天然气 | 1840篇 |
武器工业 | 13篇 |
无线电 | 55801篇 |
一般工业技术 | 77198篇 |
冶金工业 | 75054篇 |
原子能技术 | 5579篇 |
自动化技术 | 38882篇 |
出版年
2021年 | 2816篇 |
2020年 | 2158篇 |
2019年 | 2806篇 |
2018年 | 3858篇 |
2017年 | 3925篇 |
2016年 | 4273篇 |
2015年 | 3501篇 |
2014年 | 5770篇 |
2013年 | 19336篇 |
2012年 | 10255篇 |
2011年 | 14734篇 |
2010年 | 11323篇 |
2009年 | 12912篇 |
2008年 | 13962篇 |
2007年 | 14322篇 |
2006年 | 12815篇 |
2005年 | 11990篇 |
2004年 | 11596篇 |
2003年 | 11300篇 |
2002年 | 10938篇 |
2001年 | 11158篇 |
2000年 | 10302篇 |
1999年 | 10795篇 |
1998年 | 24041篇 |
1997年 | 17624篇 |
1996年 | 13946篇 |
1995年 | 11009篇 |
1994年 | 9803篇 |
1993年 | 9382篇 |
1992年 | 7148篇 |
1991年 | 6815篇 |
1990年 | 6417篇 |
1989年 | 6125篇 |
1988年 | 5871篇 |
1987年 | 4893篇 |
1986年 | 4839篇 |
1985年 | 5982篇 |
1984年 | 5605篇 |
1983年 | 4837篇 |
1982年 | 4500篇 |
1981年 | 4448篇 |
1980年 | 4218篇 |
1979年 | 4085篇 |
1978年 | 3774篇 |
1977年 | 4549篇 |
1976年 | 6102篇 |
1975年 | 3117篇 |
1974年 | 3014篇 |
1973年 | 2895篇 |
1972年 | 2321篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
CIE TC8‐01 has adopted a new color appearance model: CIECAM021 replaces the CIECAM97s.2 The new model consists of a number of refinements and simplifications of the CIECAM97s color appearance model. This article describes further tests to the robustness of the forward and reverse modes. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 99–106, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20087 相似文献
992.
Martinez S. Bullo F. Cortes J. Frazzoli E. 《Automatic Control, IEEE Transactions on》2007,52(12):2214-2226
This paper analyzes a number of basic coordination algorithms running on synchronous robotic networks. We provide upper and lower bounds on the time complexity of the move-toward-average and circumcenter laws, both achieving rendezvous, and of the centroid law, achieving deployment over a region of interest. The results are derived via novel analysis methods, including a set of results on the convergence rates of linear dynamical systems defined by tridiagonal Toeplitz and circulant matrices. 相似文献
993.
994.
Carnel L. Gordon I. Van Gestel D. Vanhaeren D. Eyben P. Beaucarne G. Poortmans J. 《Electron Device Letters, IEEE》2007,28(10):899-901
Thin-film polysilicon solar cells are a promising low-cost alternative for bulk silicon solar cells due to their reduced material thickness. Recently, we showed that the use of an amorphous silicon/polycrystalline silicon heterojunction emitter instead of a diffused homojunction emitter led to a boost in the open-circuit voltage by 90 mV. Now, we present a full evidence that shows that this improvement is related to the absence of dopant smearing along the grain boundaries. By using scanning spreading resistance microscopy, we found an enlargement of the junction area by a factor of five in case of a homojunction. The tips of the dopant spikes represent lowly doped areas with an enhanced recombination. 相似文献
995.
The objective of this investigation was to demonstrate that the firmness of a commercial vegetable product, diced and frozen red pepper (Capsicum annum var. Sendt), could be improved by the use of exogenous pectinesterase in an industrially relevant process. The diced pepper pieces 10 × 10 × 7 mm3 were infused under vacuum with a commercially available pectinesterase. The range of optimal process conditions was: 15-20°C, 45 min infusion time, a 10-25 mM CaCl2 infusion brine, a w/w ratio of pepper fruit to infusion brine of 1.5:1, and an enzyme dosage of 30-60 pectinesterase units (PEU) per kg pepper fruit. The firmness as measured by back extrusion was improved by a factor of two to three. The effect of firming was robust and conserved after freezing and heating in a simulated household cooking process. The firming process seems easily adaptable to industrial conditions and may be applicable to other vegetable and fruit products. 相似文献
996.
The infrastructure renewal program at MIT consists of a large number of projects with an estimated budget that could approach $1 billion. Infrastructure renewal at the Massachusetts Institute of Technology (MIT) is the process of evaluating and investing in the maintenance of facility systems and basic structure to preserve existing campus buildings. The selection and prioritization of projects must be addressed with a systematic method for the optimal allocation of funds and other resources. This paper presents a case study of a prioritization method utilizing multi-attribute utility theory. This method was developed at MIT's Department of Nuclear Engineering and was deployed by the Department of Facilities after appropriate modifications were implemented to address the idiosyncrasies of infrastructure renewal projects and the competing criteria and constraints that influence the judgment of the decision-makers. Such criteria include minimization of risk, optimization of economic impact, and coordination with academic policies, programs, and operations of the Institute. A brief overview of the method is presented, as well as the results of its application to the prioritization of infrastructure renewal projects. Results of workshops held at MIT with the participation of stakeholders demonstrate the feasibility of the prioritization method and the usefulness of this approach. 相似文献
997.
998.
999.
1000.
Anne J. Kershen 《Landscape Research》2004,29(3):261-275
For hundreds of years Spitalfields, the 250 acres that border the London Borough of Tower Hamlets and the City of London, has been a first point of settlement for immigrants. Its tradition of political and religious non-conformity and its proximity to the City of London and the docks have acted as a unique beacon to those seeking refuge and economic opportunity in a capital city. Spitalfields has provided a landscape upon which the incomers have engraved a 'home away from home', for themselves and their families. Using the 'Spitalfields experience' as a focal point, the concept and construction of home by migrants in the diaspora is explored, and some of the cultural tools that the Huguenots, eastern European Jews and Bangladeshis—the protagonist subject groups of this essay—have used to construct their homes in the elsewhere are examined. Due to the spatial limitations of this work, language, diet and religion have been selected as the topics under the microscope. All three facilitated the maintenance of links with the sending societies whilst, in some, though not in every instance, creating a bridge to assimilation. The usage and effectiveness of these tools is compared and contrasted and the role played by Spitalfields over the past four centuries in the creation of homes by those in an alien environment is assessed. 相似文献