全文获取类型
收费全文 | 7408篇 |
免费 | 17篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 408篇 |
金属工艺 | 22篇 |
机械仪表 | 30篇 |
建筑科学 | 97篇 |
矿业工程 | 3篇 |
能源动力 | 27篇 |
轻工业 | 693篇 |
水利工程 | 15篇 |
石油天然气 | 5篇 |
无线电 | 182篇 |
一般工业技术 | 219篇 |
冶金工业 | 5551篇 |
原子能技术 | 18篇 |
自动化技术 | 135篇 |
出版年
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 17篇 |
2014年 | 21篇 |
2013年 | 107篇 |
2012年 | 40篇 |
2011年 | 62篇 |
2010年 | 39篇 |
2009年 | 49篇 |
2008年 | 49篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 43篇 |
2004年 | 44篇 |
2003年 | 34篇 |
2002年 | 28篇 |
2001年 | 37篇 |
2000年 | 21篇 |
1999年 | 176篇 |
1998年 | 1644篇 |
1997年 | 946篇 |
1996年 | 626篇 |
1995年 | 383篇 |
1994年 | 341篇 |
1993年 | 367篇 |
1992年 | 77篇 |
1991年 | 116篇 |
1990年 | 94篇 |
1989年 | 111篇 |
1988年 | 127篇 |
1987年 | 120篇 |
1986年 | 111篇 |
1985年 | 81篇 |
1984年 | 45篇 |
1983年 | 51篇 |
1982年 | 63篇 |
1981年 | 65篇 |
1980年 | 86篇 |
1979年 | 37篇 |
1978年 | 63篇 |
1977年 | 176篇 |
1976年 | 391篇 |
1975年 | 49篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1972年 | 37篇 |
1971年 | 38篇 |
1970年 | 31篇 |
1968年 | 15篇 |
1965年 | 15篇 |
排序方式: 共有7425条查询结果,搜索用时 15 毫秒
41.
42.
The purpose of this study was to examine whether exposure of rat pups to alcohol postnatally over a period of brain development similar to that of the human 3rd trimester results in a permanent loss of cells in the inferior olivary nucleus. It was hypothesized that a deficit of neurons in the inferior olive, the sole source of climbing fibers, may contribute to the cerebellar dysfunction observed following exposure to alcohol during development. Sprague-Dawley rat pups were artificially reared and administered alcohol over postnatal days 4-9. One artificially reared group received a daily alcohol dose of 4.5 g/kg, administered as a 10.2% solution in 2 of 12 daily feedings (10.2% group). This pattern of alcohol administration resulted in high peak blood alcohol concentrations with near total clearance. The other artificially reared group was fed a diet made isocaloric to the alcohol-containing diet (gastrostomy control group). Pups were allowed to grow to adulthood and killed on postnatal day 115. The total number of neurons in the inferior olivary nucleus was estimated using unbiased stereological methods. Exposure to alcohol resulted in a significant deficit in the number of neurons in the inferior olive at 115 days of age. The total number of neurons in the alcohol-exposed group was 40.12 +/- 8.7 x 10(3), compared with 53.37 +/- 3.7 x 10(3) in the artificially reared controls. These results indicate that there is a permanent deficit of neurons in the inferior olive after postnatal exposure to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
43.
44.
45.
46.
47.
Aqueous extracts of the coralline red algaeBossiella orbigniana have been shown to catalyze the enzymatic oxidation of arachidonic acid to a previously unreported ω6 eicosapentaenoic acid
product. This unique fatty acid contains a conjugated tetraene with absorption maxima at 293, 306, and 321 nm, and was identified
by spectral methods as 5(Z),8(Z),10(E),12(E),14(Z)-eicosapentaenoic acid. The compound was given the trivial name bosseopentaenoic
acid. Under experimental conditions, production of bosseopentaenoic acid was linear up to 2 hr and dioxygen was consumed.
Bosseopentaenoic acid, along with several other conjugated tetraenes, was also present in the algae endogenously as revealed
by a comparison of the ultraviolet (UV) spectra and the high-performance liquid chromatographic (HPLC) pattern of the purified
product and the organic extract ofBossiella. 相似文献
48.
49.
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
50.