全文获取类型
收费全文 | 18029篇 |
免费 | 1213篇 |
国内免费 | 223篇 |
学科分类
工业技术 | 19465篇 |
出版年
2024年 | 55篇 |
2023年 | 245篇 |
2022年 | 621篇 |
2021年 | 804篇 |
2020年 | 522篇 |
2019年 | 510篇 |
2018年 | 636篇 |
2017年 | 686篇 |
2016年 | 630篇 |
2015年 | 615篇 |
2014年 | 831篇 |
2013年 | 1362篇 |
2012年 | 1117篇 |
2011年 | 1265篇 |
2010年 | 1019篇 |
2009年 | 941篇 |
2008年 | 981篇 |
2007年 | 908篇 |
2006年 | 829篇 |
2005年 | 577篇 |
2004年 | 496篇 |
2003年 | 470篇 |
2002年 | 416篇 |
2001年 | 354篇 |
2000年 | 319篇 |
1999年 | 301篇 |
1998年 | 366篇 |
1997年 | 272篇 |
1996年 | 211篇 |
1995年 | 191篇 |
1994年 | 160篇 |
1993年 | 111篇 |
1992年 | 78篇 |
1991年 | 52篇 |
1990年 | 54篇 |
1989年 | 55篇 |
1988年 | 59篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 37篇 |
1982年 | 34篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
介绍了北营公司X70配套埋弧焊丝用H08D盘条的开发研制情况.其生产工艺的关键点为:转炉采用“双渣法除磷”,脱氧合金化在转炉和LF炉两个阶段完成,连铸采用结晶器电磁搅拌及末端电磁搅拌、恒定拉速;盘条采用控冷控轧及轧后延迟型斯太尔摩冷却工艺等措施.生产的成品盘条成分、力学性能、金相组织等指标均满足客户拉拔工艺要求. 相似文献
2.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS). 相似文献
4.
5.
6.
Glass columns (length 50 cm, i.d. 4 cm) containing 900 g of uranium ore waste were subjected to a three-step process: (1) acid drainage generation, (2) neutralization and precipitation treatment and, again, (3) acid drainage generation. In the first acid generation step, lasting about one year, different variables (pyrite addition, inoculation and irrigation solution) were tested by measuring effluent pH, redox potential, total iron and sulphate. Conditions of acid generation were satisfactorily reproduced, reaching stable pH values around 2.0 that were determined mainly by pyrite addition and the type of irrigation solution used (distilled water or ferrous sulphate). The neutralization and precipitation treatment consisted of alternating irrigations of a neutralizing solution (CaO saturated plus NaOH) and a precipitating solution (ferric sulphate saturated). This treatment caused accumulation of basic iron sulphate and iron oxide precipitates according to SEM studies. After this treatment, the barrier effect created by the reaction products was checked, using irrigation solutions similar to the first step. The effluents collected showed higher pH and lower redox potential, total iron and sulphate values than those observed before the treatment, evidencing inhibition of acid drainage generation. 相似文献
7.
8.
Amanda Alliband Daniel W. Lenz Laura E. Stevenson Travis Whitmer Rex Cash Dennis Burns Sarah Hall William T.K. Stevenson 《Progress in Organic Coatings》2008
A model has been proposed to explain the failure of the original BMS10-39 epoxy paint on upper vertical surfaces in B-52 fuel tanks. The model involves interaction of the paint with DIEGME, a fuel system ice inhibitor (FSII) in jet fuel, that is distilled from the liquid fuel. In this communication, distillation experiments used to support the model are refined to better match the mass transfer of vapor from fuel in a B-52 fuel tank at close to room temperature. The interaction of these lower temperature distillates with the paint affirms the earlier model. On the basis of these experiments it is proposed that paint failure may be controlled or eliminated by reducing the level of DIEGME in the fuel. Proposed changes in military jet fuel composition are detailed. 相似文献
9.
10.
Here we are presenting the case of a 70-years-old woman who has hepatic cirrhosis anti-HCV and insulin-dependent diabetes mellitus, without relevant epidemiologic ascendants or previous transfusions and HBV, HIV negatives. On admission to our hospital she showed signs of autoimmune hemolytic anaemia (AHA) which was confirmed by positive direct Coombs test and an improvement in blood test after corticoid treatment. Having discarded other possible causes such as drugs infectious diseases or essential mixed cryoglobulinemia (CME), we put forward the possible association between AHA and infection by HCV, where AHA was an extrahepatic immunological manifestation of HCV. This fact has never been brought to light in previous medical literature. 相似文献