全文获取类型
收费全文 | 2725篇 |
免费 | 46篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 2772篇 |
出版年
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 25篇 |
2017年 | 16篇 |
2016年 | 13篇 |
2015年 | 20篇 |
2014年 | 32篇 |
2013年 | 70篇 |
2012年 | 47篇 |
2011年 | 73篇 |
2010年 | 54篇 |
2009年 | 62篇 |
2008年 | 67篇 |
2007年 | 59篇 |
2006年 | 54篇 |
2005年 | 55篇 |
2004年 | 30篇 |
2003年 | 43篇 |
2002年 | 40篇 |
2001年 | 44篇 |
2000年 | 43篇 |
1999年 | 55篇 |
1998年 | 374篇 |
1997年 | 249篇 |
1996年 | 175篇 |
1995年 | 106篇 |
1994年 | 91篇 |
1993年 | 93篇 |
1992年 | 46篇 |
1991年 | 34篇 |
1990年 | 36篇 |
1989年 | 42篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 24篇 |
1985年 | 31篇 |
1984年 | 17篇 |
1983年 | 28篇 |
1982年 | 18篇 |
1981年 | 34篇 |
1980年 | 22篇 |
1979年 | 30篇 |
1978年 | 24篇 |
1977年 | 52篇 |
1976年 | 95篇 |
1975年 | 27篇 |
1974年 | 15篇 |
1973年 | 16篇 |
1971年 | 13篇 |
1969年 | 10篇 |
排序方式: 共有2772条查询结果,搜索用时 15 毫秒
31.
MM Berenson TD Johnson NR Markowitz KN Buchi WS Samowitz 《Canadian Metallurgical Quarterly》1993,104(6):1686-1691
BACKGROUND: Antireflux therapy has generally failed to induce regression of Barrett's epithelium. It was hypothesized that squamous epithelium could be restored if the columnar tissue was ablated while gastric acid secretion was suppressed. METHODS: Ten white men with Barrett's esophagus received 40 mg of omeprazole daily. Thereafter, every 2-5 weeks they underwent videotaped endoscopies to argon laser photoablate columnar tissue, obtain biopsy specimens, and assess results. Squamous re-epithelialization was assessed by correlation of videotapes and directed biopsies. RESULTS: Patients had one to eight areas ablated, totaling 0.5-12.0 cm2. Videotape assessments were corroborated by biopsy in all but one instance. Thirty-eight of 40 treatment locations partially or completely re-epithelialized with squamous tissue. Squamous regrowth appeared to occur by spread from contiguous squamous borders and de novo from glandular tissue. Regrowth was influenced by the extent of squamous borders and completeness of ablations. Nonablated glandular tissue persisted beneath squamous epithelium. CONCLUSIONS: Ablation of Barrett's epithelium and suppression of acid secretion facilitated squamous re-epithelialization. A progenitor cell within the metaplastic tissue has the potential to differentiate normally. 相似文献
32.
Blascovich Jim; Brennan Kelly; Tomaka Joe; Kelsey Robert M.; Hughes Pamela; Coad Mary Lou; Adlin Richard 《Canadian Metallurgical Quarterly》1992,63(1):164
Investigated in 3 experiments the relationships between affect intensity and basal, evoked, and perceived cardiac arousal. Affect intensity was assessed using R. J. Larsen and E. Diener's (1987) Affect Intensity Measure (AIM). Cardiac arousal was evoked with exercise in the 1st study and with mental arithmetic in the 2nd and 3rd. Perceived cardiac arousal was measured under optimal conditions using a standard heartbeat discrimination procedure. Women as a group scored higher on the AIM. Affect intensity was unrelated to basal or evoked cardiac arousal and was negatively related to perceived cardiac arousal in all 3 studies. Data suggest that affect intensity, although unrelated to actual physiological arousal, is negatively related to the accuracy with which individuals perceive their own arousal. Results are discussed within the context of an expanded arousal-regulation model (J. Blascovich, 1990). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
Effects of forage level and canola seed supplementation on site and extent of digestion of organic matter, carbohydrates, and energy by steers 总被引:1,自引:0,他引:1
The objective of this study was to determine the effects of fat supplementation from canola seed (CS) on ruminal fermentation and postruminal digestion of OM, carbohydrates, and energy of diets containing different levels of forage. Six ruminally and duodenally cannulated beef steers (354 kg +/- 18) were given ad libitum access to six isonitrogenous diets that were offered twice daily in a 6 x 6 Latin square design. Treatments were arranged as a 2 x 3 factorial with two forage levels (70 vs 30% of dietary DM as corn silage) and three forms of CS supplementation including no CS or CS added at 10% of dietary DM as whole CS treated with alkaline hydrogen peroxide or untreated crushed CS. Fat from CS provided 5% of dietary DM. The remaining dietary ingredients were corn, canola meal, molasses, and urea. No interactions (P > .05) between dietary forage level and CS supplementation were observed for ruminal characteristics or digestion of OM, carbohydrates, and energy in the rumen, postruminally, or in the total tract. Fat supplementation from CS did not affect (P > .05) DMI. With few exceptions, fat supplementation did not affect (P > .05) ruminal, postruminal, or total tract digestibilities of OM, structural and nonstructural carbohydrates, and GE. Ruminal disappearance of GE was decreased (P < .05) when diets were supplemented with fat from whole treated CS, and total tract digestibilities of OM and GE were decreased (P < .05) when diets were supplemented with fat from CS in either form. Ruminal pH, concentrations of NH3 N and total VFA, and molar proportions of acetate, propionate, and butyrate were not affected (P > .05) by fat supplementation. Results suggest that fat supplementation from CS (at 5% of dietary DM) as whole treated or untreated crushed had no negative effects on ruminal fermentation of OM, carbohydrates, or energy when steers were given ad libitum access to diets containing high or low forage. 相似文献
34.
A Hughes 《BT Technology Journal》2003,21(4):175-185
Over the last decade, the area of programmable networking seems to have matured significantly; it now attracts interest from
both academic and industrial institutions. Many projects have either focused on or made use of work done in this area; however,
until now, programmable networks have not been used to improve the process of engineering router software. This project does
just this. Previous publications have outlined a software system that makes the experimental analysis of routers — and hence
router software — more accessible to network researchers. The software system provides a configuration system designed to
manage a test-bed consisting of multiple programmable routers. It allows administrators to quickly and easily configure the
test-bed using a high-level policy language. This paper discusses this language and presents rationale for design choices.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
35.
Hughes Rosemary B.; Nosek Margaret A.; Howland Carol A.; Groff Janet Y.; Mullen Patricia Dolan 《Canadian Metallurgical Quarterly》2003,48(3):182
Objective: To pilot test a health promotion intervention for women with physical disabilities. Design: Pre- and postintervention questionnaires. Participants: Two groups of women with physical disabilities (n=15). Intervention: Seven-session weekly workshop intervention grounded primarily in social-cognitive theory. Setting: Disability and rehabilitation settings. Main Outcome Measures: Indicators of health status. Results: Statistically significant positive changes between pre- and postintervention scores on measures of self-efficacy for dietary behaviors, medical decision making, social interaction, physical functioning, impact of physical limitation on role activities, and vitality. Conclusion: Women with disabilities who participate in this health promotion intervention may exhibit improvements on indicators of health status. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
RE Hughes AG Schneeberger KN An BF Morrey SW O''Driscoll 《Canadian Metallurgical Quarterly》1997,6(5):444-448
A retrospective case reference study examining the use of alcohol and tobacco in 303 women aged 40 or over suffering from oral or oropharyngeal cancer was conducted in the south-west Netherlands. Both alcohol and tobacco consumption are important in the development of oral and oropharyngeal cancer with increased consumption of both markedly increasing the risks of cancer, but alcohol having the greater effect. 相似文献
37.
Switched-current (SI) signal processing circuits with video frequency performance are presented. The delay cells employ negative feedback to produce a `virtual earth' at the input node to improve transmission accuracy. Fully differential structures with common-mode feedback are used to reduce charge injection errors and crosstalk from digital signals. An IC test circuit, in a 1 μm standard digital CMOS process, containing simple delay lines and an FIR filter section is described, and measured performance is given. Typically, a 2T delay line sampling at 13.3 MHz gave a low-frequency gain error of -54 dB, a settling error of -60 dB, a third-harmonic distortion of -40 dB with 75% modulation, and an S /N ratio of 60 dB. Scaling of the memory cell device dimensions and currents should permit SI operation at clock frequencies beyond 100 MHz 相似文献
38.
The techniques of Feulgen staining, acridine orange staining, and a sperm chromatin structure assay using acridine orange and flow cytometry were compared for selective examination of bovine sperm nuclei. Twenty frozen semen samples were simultaneously analysed by all three methods. The prevalence of abnormally condensed DNA and its relationship to other semen traits were determined in ejaculates from 70 bulbs presented for routine examination for breeding soundness and in frozen semen from 348 bulls evaluated over five years. A breeding trial with 118 beef heifers using semen from six bulls with different degrees of nuclear abnormalities was performed to assess the importance of the defects with respect to fertility. The results indicate that few spermatozoa with abnormal DNA condensation are found in normal semen, but the incidence increases with disturbance of spermatogenesis. However, high numbers of abnormally condensed nuclei were found in the absence of an increase in other defects. This nuclear defect might be at least partially of epididymal origin; it can lower fertility and can be compensated for by increasing the numbers of normal spermatozoa in the insemination dose. The percentage of abnormally condensed sperm nuclei as detected by Feulgen staining was significantly correlated with that detected by microscopy after acridine orange staining and by the sperm chromatin structure assay. We therefore consider the Feulgen technique to be a valuable tool for assessing the nuclear integrity of bovine spermatozoa. 相似文献
39.
The absorption and elimination of [14C]-phenol (63.5 nmol) after oral, dermal, intratracheal, or intravenous administration in rat was rapid and extensive. Urinary elimination of radioactivity predominated, with a range of 75-95% of the dose detected in urine by 72 h post-exposure. Washing the dermal site 72 h post-exposure removed 14% of the dose. Two per cent of the dose was detected in the skin. The urinary metabolites at 4 and 8 h after administration by the four routes included phenyl sulphate and lower amounts of phenyl glucuronide. Phenol was poorly retained in the body after administration by the four routes. Phenol remaining in the body was widely distributed, with accumulation primarily in the liver, lung, and kidney. 相似文献
40.