全文获取类型
收费全文 | 2550篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 2篇 |
机械仪表 | 10篇 |
建筑科学 | 5篇 |
矿业工程 | 1篇 |
能源动力 | 2篇 |
轻工业 | 33篇 |
水利工程 | 2篇 |
无线电 | 9篇 |
一般工业技术 | 20篇 |
冶金工业 | 2437篇 |
原子能技术 | 2篇 |
自动化技术 | 13篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2014年 | 1篇 |
2013年 | 17篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 8篇 |
2000年 | 2篇 |
1999年 | 64篇 |
1998年 | 805篇 |
1997年 | 431篇 |
1996年 | 287篇 |
1995年 | 160篇 |
1994年 | 112篇 |
1993年 | 149篇 |
1992年 | 14篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 19篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 55篇 |
1976年 | 154篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1955年 | 2篇 |
1944年 | 1篇 |
排序方式: 共有2562条查询结果,搜索用时 15 毫秒
1.
Abdallah M. Altass H. M. El-Sayed R. Al Gorair Arej S. Jahdaly B. A. AL Sobhi M. 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(4):811-819
Protection of Metals and Physical Chemistry of Surfaces - Three nonionic surfactants molecules (NS) derived from a fused pyridine characterized by IR and 1HNMR spectra were synthesized and examined... 相似文献
2.
3.
RIDA AL‐ADAMAT SERWAN M. J. BABAN IAN FOSTER 《The International journal of environmental studies》2013,70(3):337-350
The Jordanian government has encouraged irrigated agriculture since the early 1990s by providing low cost loans to drill private wells. The impacts of this practice on land use change were examined within a small (362 km2) area of the Jordanian Badia using Geoinformatics. Aerial photographs, SPOT and Landsat TM imageries were used, in a GIS environment, to map and examine changes in the farming patterns since 1990. Field surveys and questionnaires were used to ground truth the remotely sensed data. The results indicate that the cultivated area has increased from just 28.5 ha in 1990 to over 1000 ha in 2000 and that the number of farms has increased from 2 to 32 over the same time period. Furthermore, farm locations are moved annually restricted by the position of the well and land availability; this also causes land use change. 相似文献
4.
The optimum conditions for the production of coprecipitate from sheep milk were studied. The best percentage of calcium chloride added to milk was 0.2%, which resulted in a recovery of 97.5% of milk proteins. At low pH (4.5–5), the recovery of protein was low, but it increased at higher pH values (5.5–6.5); recovery was greatest at pH 6.5. The optimum heating temperature to obtain coprecipitate from sheep milk was 85–95°C. The functional properties of the sheep milk coprecipitate were studied. At pH values higher than 6, there were no differences between the solubility of sheep milk coprecipitate and sheep milk sodium caseinate, but the solubility of coprecipitate at pH values lower than 5 was relatively higher than those of the caseinate. At pH ≥6, the emulsion activity index (EAI) for emulsions of sheep milk coprecipitate and caseinate increased as pH increased; at all pH values, the EAI of the coprecipitate was higher than that of the caseinate. Sheep milk coprecipitate showed higher foaming ability and stability than sheep milk sodium caseinate. 相似文献
5.
Most of our present knowledge about the impacts of solar UVB radiation on terrestrial ecosystems comes from studies with plants. Recently, the effects of UVB on the growth and survival of consumer species have begun to receive attention, but very little is known about UVB impacts on animal behavior. Here we report that manipulations of the flux of solar UVB received by field-grown soybean crops had large and consistent effects on the density of the thrips (Caliothrips phaseoli, Thysanoptera: Thripidae) populations that invaded the canopies, as well as on the amount of leaf damage caused by the insects. Solar UVB strongly reduced thrips herbivory. Thrips not only preferred leaves from plants that were not exposed to solar UVB over leaves from UVB-exposed plants in laboratory and field choice experiments, but they also appeared to directly sense and avoid exposure to solar UVB. Additional choice experiments showed that soybean leaf consumption by the late-season soybean worm Anticarsia gemmatalis (Lepidoptera: Noctuidae) was much less intense in leaves with even slight symptoms of an early thrips attack than in undamaged leaves. These experiments suggest that phytophagous insects can present direct and indirect behavioral responses to solar UVB. The indirect responses are mediated by changes in the plant host that are induced by UVB and, possibly, by other insects whose behavior is affected by UVB. 相似文献
6.
AL Schwartz PC Van Veldhuisen DE Gaasterland F Ederer EK Sullivan MN Cyrlin 《Canadian Metallurgical Quarterly》1999,127(1):8-19
PURPOSE: To compare the incidence of encapsulated bleb after trabeculectomy in eyes with and without previous argon laser trabeculoplasty and to assess other risk factors for encapsulated bleb development. METHODS: After medical treatment failure, eyes enrolled in the Advanced Glaucoma Intervention Study (AGIS) were randomly assigned to sequences of interventions starting with either argon laser trabeculoplasty or trabeculectomy. In the present study we compared the clinical course for 1 year after trabeculectomy in 119 eyes with failed argon laser trabeculoplasty with that of 379 eyes without previous argon laser trabeculoplasty. Data on bleb encapsulation were collected at the time that the encapsulation was diagnosed, and 3 and 6 months later. RESULTS: Of multiple factors examined in the AGIS data for the risk of developing encapsulated bleb, only male gender and high school graduation without further formal education were statistically significant. Encapsulation occurred in 18.5% of eyes with previous argon laser trabeculoplasty failure and 14.5% of eyes without previous argon laser trabeculoplasty (unadjusted relative risk, 1.27; 95% confidence limits = 0.81, 2.00; P = .23). After adjusting for age, gender, educational achievement, prescribed systemic beta-blockers, diabetes, visual field score, and years since glaucoma diagnosis, this difference remains statistically not significant. Four weeks after trabeculectomy, mean intraocular pressure was 7.5 mm Hg higher in eyes with (22.5 mm Hg) than without (15.0 mm Hg) encapsulated bleb; at 1 year after trabeculectomy and the resumption of medical therapy when needed, this excess was reduced to 1.4 mm Hg. CONCLUSIONS: This study, as did two previous studies, found male gender to be a risk factor for bleb encapsulation. Four studies, including the present study, have reported a higher rate of encapsulation in eyes with previous argon laser trabeculoplasty; in two of the studies, one of which was the present study, the rate was not statistically significantly higher; in the other two studies the rate was significantly higher. The 4-week postoperative mean intraocular pressure was higher in eyes with than without encapsulated bleb; with the resumption of medical treatment the two means converged after 1 year. 相似文献
7.
BACKGROUND: Obesity and hypotonia in children with Prader-Willi syndrome (PWS) are accompanied by abnormal body composition and diminished energy expenditure resembling a growth hormone deficient state. Hypothalamic dysfunction in PWS often includes decreased growth hormone (GH) secretion, suggesting a possible therapeutic role for exogenous GH treatment. OBJECTIVES AND METHODS: After 6 months of observation to determine baseline growth rate, and with the use of a 12-month randomized controlled study design, the effects of GH treatment (1 mg/m2/d) on growth, body composition, strength and agility, pulmonary function, resting energy expenditure (REE), and fat utilization were assessed in 54 children with PWS (n = 35 treatment and n = 19 control). Percent body fat and bone mineral density were measured by dual x-ray absorptiometry. Indirect calorimetry was used to determine REE and to calculate respiratory quotients. RESULTS: Stimulated levels of GH in response to clonidine testing were low in all patients (peak, 2.0 ng/mL). After 12 months, GH-treated subjects showed significantly increased height velocity Z scores (mean, 1.0 1.7 to 4.6 2.9; P <.001), decreased percent body fat (mean, 46.3% 8.4% to 38.3% 10.7%; P <.001), and improved respiratory muscle function, physical strength, and agility (sit-ups, weight-lifts, running speed, and coordination). A significant decline in respiratory quotients occurred during GH therapy (0.81 to 0.77, P <.001), but total REE did not change. CONCLUSIONS: GH treatment of children with PWS accelerated growth, decreased percent body fat, and increased fat oxidation but did not significantly increase total REE. Improvements in respiratory muscle strength, physical strength, and agility also occurred, suggesting that GH treatment may have value in reducing some physical disabilities experienced by children with PWS. 相似文献
8.
9.
10.