全文获取类型
收费全文 | 8943篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 5篇 |
化学工业 | 79篇 |
金属工艺 | 21篇 |
机械仪表 | 12篇 |
建筑科学 | 19篇 |
能源动力 | 3篇 |
轻工业 | 60篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 64篇 |
一般工业技术 | 74篇 |
冶金工业 | 8538篇 |
原子能技术 | 2篇 |
自动化技术 | 52篇 |
出版年
2020年 | 5篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 31篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 20篇 |
2009年 | 26篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 18篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 16篇 |
1999年 | 294篇 |
1998年 | 2717篇 |
1997年 | 1509篇 |
1996年 | 965篇 |
1995年 | 563篇 |
1994年 | 435篇 |
1993年 | 545篇 |
1992年 | 68篇 |
1991年 | 112篇 |
1990年 | 104篇 |
1989年 | 91篇 |
1988年 | 99篇 |
1987年 | 94篇 |
1986年 | 97篇 |
1985年 | 68篇 |
1984年 | 5篇 |
1983年 | 12篇 |
1982年 | 38篇 |
1981年 | 43篇 |
1980年 | 82篇 |
1979年 | 7篇 |
1978年 | 15篇 |
1977年 | 188篇 |
1976年 | 442篇 |
1975年 | 10篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1963年 | 3篇 |
1956年 | 3篇 |
1955年 | 7篇 |
排序方式: 共有8951条查询结果,搜索用时 656 毫秒
61.
BACKGROUND: Mechanical ventilation with positive end-expiratory pressure (PEEP) can impair renal hemodynamics. Fenoldopam, a dopamine receptor agonist, has been shown, in animal experiments, to improve renal perfusion. The purpose of the current study was to examine the effects of this agent on altered renal hemodynamics secondary to positive pressure ventilation. METHODS: Twelve patients requiring mechanical ventilation of their lungs and PEEP for the treatment of hypoxemia after multiple trauma or visceral surgery were studied. Hemodynamic variables, renal vascular resistance, urine flow, creatinine, inulin and PAH clearance, and excretion of sodium and potassium (NaE and KE) were measured before and after introduction of a level of PEEP high enough to decrease urine flow rate by 25% or more, and after administration of intravenous fenoldopam. RESULTS: No hemodynamic effect resulted from 0.1 microgram.kg-1.min-1, but 0.2 micrograms.kg-1.min-1 fenoldopam decreased both diastolic and mean arterial blood pressure from 66 +/- 37 (mean +/- SEM) to 57 +/- 21 mmHg, and from 83 +/- 3 to 74 +/- 4 mmHg, respectively. Renal vascular resistance was reduced from 54 +/- 12 to 19 +/- 5 dynes.s.cm-5 at 0.2 micrograms.kg-1.min-1. Fenoldopam produced a dose-related increase in renal blood flow and PAH clearance. With 0.2 micrograms.kg-1.min-1 fenoldopam, urine flow increased from 81 +/- 25 to 116 +/- 29 ml/h, NaE from 28 +/- 7 to 85 +/- 70 microM/min, and KE from 65 +/- 12 to 109 +/- 16 microM/min. CONCLUSIONS: The results of the current study indicate that intravenous fenoldopam at a dose of 0.2 micrograms.kg-1.min-1 improves renal hemodynamics and increases Na and K excretion in patients requiring mechanical ventilation of their lungs and PEEP. These effects are probably caused by an increased kidney perfusion secondary to renal artery vasodilation. 相似文献
62.
63.
64.
65.
Joshua Vaughan Joel Fortgang William Singhose Jeffrey Donnell Thomas Kurfess 《Mechatronics》2008,18(4):179-186
It is commonly accepted that hands-on experiences increase both learning and enjoyment during coursework. Mechatronics projects provide both interesting and relevant hands-on experiences for a wide range of topics including design processes, basic mechatronics concepts, technical communication, and working in a group environment. ME2110: Creative Decisions and Design at Georgia Tech integrates mechatronics and technical communication into a sophomore level mechanical design class. This paper describes the course in detail, highlighting the course goals and layout, tools provided to the students, industry involvement, and the main challenges of administering such a course. 相似文献
66.
This study examined why Websites were co-linked using Canadian university Websites as the test set. Pages that co-linked to
these university Websites were located using Yahool. A random sample of 859 co-linking pages (the page that initiated the
co-link) was retrieved and the contents of the page, as well as the context of the link, were manually examined to record
the following variables: language, country, type of Website, and the reasons for co-linking. The study found that in over
94% of cases, the two co-linked universities were related academically; many of these cases (38%) showed a relationship specifically
in teaching or research. This confirms results, from previous quantitative studies, that Web co-links can be a measure of
the similarity or relatedness of sites being co-linked and that Web co-link analysis can thus be used to study relationships
among linked Websites. 相似文献
67.
RC Smith JS Lyles JA Mettler AA Marshall LF Van Egeren BE Stoffelmayr GG Osborn V Shebroe 《Canadian Metallurgical Quarterly》1995,70(8):729-732
PURPOSE: To use a controlled, randomized design to assess the effect on patient satisfaction of an intensive psychosocial training program for residents. METHOD: Twenty-six first-year residents, in two internal medicine and family practice community-based programs affiliated with the Michigan State University College of Human Medicine, were randomly assigned during 1991 and 1992 to a control group or a one-month intensive training program. Experiential teaching focused on many psychosocial skills required in primary care. A 29-item questionnaire administered before and after the residents' training evaluated their patients' satisfaction regarding patient disclosure, physician empathy, confidence in physician, general satisfaction, and comparison of the physician with other physicians. Analyses of covariance with groups and gender as factors and pre-training patient satisfaction scores as the covariate evaluated the effect of the training. RESULTS: The patients of the trained residents expressed more confidence in their physicians (p = .01) and more general satisfaction (p = .02) than did the patients of controls. The effect of training on patient satisfaction with patient disclosure (p < .01) and physician empathy (p < .05) was greater for female than for male residents. CONCLUSION: The intensive psychosocial training program for residents improved their patients' satisfaction. 相似文献
68.
69.
70.
Syncytium-inducing (SI) variants of human immunodeficiency virus type 1 (HIV-1) are evolutionary variants that are associated with rapid CD4+ cell loss and rapid disease progression. The heteroduplex tracking assay (HTA) was used to detect evolutionary V3 variants by amplifying the V3 sequences from viral RNA derived from 50 samples of patient plasma. For this V3-specific HTA (V3-HTA), heteroduplexes were formed between the patient V3 sequences and a probe with the subtype B consensus V3 sequence. Evolution was then measured by divergence from the consensus. The presence of evolutionary variants was correlated with SI detection data on the same samples from the MT-2 cell culture assay. Evolutionary variants were correlated with the SI phenotype in 88% of the samples, and 96% of the SI samples contained evolutionary variants. In most cases the evolutionary V3 variants represented discrete clonal outgrowths of virus. Sequence analysis of the six discordant samples that did not show this correlation indicated that three non-syncytium-inducing (NSI) samples had V3 sequences that had evolved away from the consensus sequence but not toward an SI genotype. A fourth sample showed little evolution away from the consensus but was SI, which indicates that not all SI variants require basic substitutions in V3. The other two samples had SI-like genotypes and NSI phenotypes, suggesting that V3-HTA was able to detect SI emergence in these samples in the absence of their detection in vitro. V3-HTA was also used to confirm SI variant selection in MT-2 cells and to examine the possibility of variant selection during virus culture in peripheral blood cells. 相似文献