全文获取类型
收费全文 | 7395篇 |
免费 | 68篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 26篇 |
化学工业 | 581篇 |
金属工艺 | 11篇 |
机械仪表 | 33篇 |
建筑科学 | 62篇 |
矿业工程 | 5篇 |
能源动力 | 44篇 |
轻工业 | 615篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 109篇 |
一般工业技术 | 284篇 |
冶金工业 | 5437篇 |
原子能技术 | 17篇 |
自动化技术 | 229篇 |
出版年
2018年 | 29篇 |
2017年 | 23篇 |
2016年 | 34篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 161篇 |
2012年 | 55篇 |
2011年 | 69篇 |
2010年 | 55篇 |
2009年 | 65篇 |
2008年 | 70篇 |
2007年 | 65篇 |
2006年 | 46篇 |
2005年 | 44篇 |
2004年 | 36篇 |
2003年 | 50篇 |
2002年 | 29篇 |
2001年 | 31篇 |
2000年 | 32篇 |
1999年 | 163篇 |
1998年 | 1536篇 |
1997年 | 875篇 |
1996年 | 601篇 |
1995年 | 353篇 |
1994年 | 330篇 |
1993年 | 340篇 |
1992年 | 70篇 |
1991年 | 112篇 |
1990年 | 81篇 |
1989年 | 109篇 |
1988年 | 120篇 |
1987年 | 117篇 |
1986年 | 106篇 |
1985年 | 76篇 |
1984年 | 43篇 |
1983年 | 45篇 |
1982年 | 64篇 |
1981年 | 64篇 |
1980年 | 75篇 |
1979年 | 38篇 |
1978年 | 70篇 |
1977年 | 173篇 |
1976年 | 372篇 |
1975年 | 59篇 |
1974年 | 52篇 |
1973年 | 29篇 |
1972年 | 41篇 |
1971年 | 40篇 |
1970年 | 31篇 |
1966年 | 26篇 |
排序方式: 共有7470条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
75.
Patients with chlamydial infections (Ct) attending the outpatient Venereal Disease Clinic of Copenhagen from July 1-November 30 1995 were asked to fill in a questionnaire focusing upon knowledge, attitude and behaviour related to sexually transmitted diseases (STDs) in order to strengthen the future prevention of Ct. The questionnaire was answered by 37 men and 35 women with a median age of 27 and 21 years and a median number of three and two sexual partners within the last six months, respectively. Half of the patients had previously had an STD, and 92% had been tested for HIV, of whom one homosexual man was known HIV-positive. Notification about exposure from a partner was the reason for attending for 24%. All but one were in favour of partner notification, but only 6% wanted provider referral. During last intercourse condoms had neither been used with a steady partner by 75% especially by the young and women, who thought themselves safe, nor with a casual partner by 52% especially among the young and men, mainly because of thoughtlessness or perception of low risk. Before the actual STD diagnosis only 49% were able to name one symptom and 35% one complication related to Ct. A majority (79%) stated, that fear of catching another Ct would lead to better protection, and 70% found that more information would have a preventive effect. Future Ct prevention programs in Denmark should include intensified chlamydial screening and partner notification together with centrally produced mass media information supplemented by individual counselling. 相似文献
76.
Daniel Grosjean Eric Grosjean II Edwin L. Williams 《Israel journal of chemistry》1994,34(3-4):365-373
The atmospheric oxidation of the unsaturated aldehyde 2-ethyl acrolein, CH2=C(C2H5)CHO, has been studied in laboratory experiments involving the reaction of ozone with 2-ethyl acrolein in the dark (with cyclohexane added to scavenge the hydroxyl radical), and the sunlight irradiation of 2-ethyl acrolein with NO in air. The major carbonyl products of the 2-ethyl acrolein reaction with ozone are formaldehyde, acetaldehyde, and the dicarbonyl ethylglyoxal, CH3CH2COCHO. Sunlight irradiation of 2-ethyl acrolein and NO led to the formation of three carbonyls (formaldehyde, acetaldehyde, and ethylglyoxal) and three peroxyacyl nitrates, (RC(O)OONO2), including PAN (R = CH3), PPN (R = C2H5), and the unsaturated compound EPAN (R = CH2=C(C2H5)). Mechanisms are outlined for the reactions of ozone and of the hydroxyl radical with 2-ethyl acrolein. These mechanisms are consistent with the observed carbonyl and peroxyacyl nitrate products. Thermal decomposition, a major atmospheric removal process for peroxyacyl nitrates, has been studied for EPAN. The decomposition rate of EPAN relative to that of PAN is 0.59–0.73 at 292–294 K and 1 atm of air. Atmospheric implications of these results are discussed. 相似文献
77.
This study extends Megargee's Minnesota Multiphasic Personality Inventory (MMPI)-based classification system to female offenders. MMPI-2s of 400 women in state and federal prisons were rescored and reconfigured to estimate their original MMPI profiles. Their MMPIs and MMPI-2s were classified according to the rules devised for the original MMPI. Next, the MMPI-2s were reclassified using new rules for classifying the MMPI-2s of male offenders. Neither approach led to satisfactory agreement between MMPI and MMPI-2. A major problem was that Scale 5 was more prominent in the women's MMPI-2 profiles than on their MMPIs. Using revised rules for classifying the original MMPIs and the MMPI-2s of female offenders, 386 of the 400 women (97%) could be classified on both versions of the MMPI, of whom 336 (87%) were classified identically. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
79.
European Food Research and Technology - Bei Bestimmungen des Proteingehalts von Haselnüssen in verschiedenen Handelsprodukten wie Nuß-Nougatcremes and Nußmus mit der... 相似文献
80.
Four sets of sweet potato clones obtained by meristem tip culture were used to investigate the effect of feathery mottle virus (FMV) infection on the appearance, sensory quality and chemical composition of the storage roots. This study, encompassing four generations, indicated that FMV infection had a slight effect on carbohydrate metabolism but no effect on the polyphenoloxidase-phenol system. Flavor and texture profile analyses indicated that for one clone, FMV-infected roots were more desirable when baked than healthy roots. Considering the study as a whole, FMV infection did not appear to adversely affect sweet potato sensory properties. Clones produced from the same parent by meristem tip culture might have different compositional and sensory properties. 相似文献