全文获取类型
收费全文 | 3967篇 |
免费 | 19篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 4篇 |
综合类 | 9篇 |
化学工业 | 26篇 |
金属工艺 | 9篇 |
机械仪表 | 15篇 |
建筑科学 | 13篇 |
矿业工程 | 5篇 |
能源动力 | 5篇 |
轻工业 | 29篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 23篇 |
一般工业技术 | 40篇 |
冶金工业 | 3771篇 |
原子能技术 | 1篇 |
自动化技术 | 30篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 24篇 |
2008年 | 16篇 |
2007年 | 39篇 |
2006年 | 10篇 |
2005年 | 20篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 3篇 |
1999年 | 138篇 |
1998年 | 1236篇 |
1997年 | 668篇 |
1996年 | 457篇 |
1995年 | 255篇 |
1994年 | 206篇 |
1993年 | 238篇 |
1992年 | 30篇 |
1991年 | 41篇 |
1990年 | 46篇 |
1989年 | 48篇 |
1988年 | 37篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 29篇 |
1983年 | 3篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 62篇 |
1976年 | 147篇 |
1975年 | 1篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1962年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有3990条查询结果,搜索用时 15 毫秒
991.
992.
MJ Avram TC Krejcie CU Niemann C Klein WB Gentry CA Shanks TK Henthorn 《Canadian Metallurgical Quarterly》1997,87(6):1381-1393
BACKGROUND: The cardiovascular effects of halothane are well recognized, but little is known of how this affects drug distribution. The effect of halothane anesthesia on physiologic factors that affect drug disposition from the moment of injection was investigated. METHODS: The dispositions of markers of intravascular space and blood flow (indocyanine green), extracellular space and free water diffusion (inulin), and total body water and tissue perfusion (antipyrine) were determined in four purpose-bred coonhounds. The dogs were studied while awake and while anesthetized with 1%, 1.5%, and 2% halothane in a randomized order determined by a repeated measures Latin square experimental design. Marker dispositions were described by recirculatory pharmacokinetic models based on frequent early and less frequent later arterial blood samples. These models characterize the role of cardiac output and its distribution on drug disposition. RESULTS: Halothane caused a significant and dose-dependent decrease in cardiac output. The disposition of antipyrine was most profoundly affected by halothane anesthesia, which increased both nondistributive intercompartmental clearance and volume while decreasing fast and slow tissue clearances and elimination clearance in a halothane dose-dependent manner. CONCLUSIONS: Halothane-induced changes in blood flow to the compartments of the antipyrine recirculatory model were not proportional to changes in cardiac output. Halothane anesthesia significantly increased (to more than double) the area under the drug concentration versus time curve due to an increase in the apparent peripheral blood flow not involved in drug distribution, despite a dose-dependent cardiac output decrease. Recirculatory pharmacokinetic models include the best aspects of traditional compartmental and physiologic pharmacokinetic models while offering advantages over both. 相似文献
993.
994.
GV Herdy VG Lopes ML Arag?o CA Pinto PA Tavares Júnior FB Azeredo PM Nascimento 《Canadian Metallurgical Quarterly》1998,71(2):121-126
New bisantrene analogues were synthesized, bearing one or two 4,5-dihydro-1H-imidazol-2-yl hydrazone side chains at positions 1,4 or 9 of the anthracene ring system. A 10-azabioisostere was also prepared. The position of substituents in structurally isomeric drugs modulates topoisomerase II poisoning and specificity, along with cytotoxicity. 相似文献
995.
996.
997.
998.
GJ Wang ND Volkow JS Fowler NR Pappas CT Wong K Pascani CA Felder RJ Hitzemann 《Canadian Metallurgical Quarterly》1998,22(8):1850-1854
It is generally believed that women are more vulnerable to alcohol's toxic effects than men. Studies in male alcoholics have consistently shown reductions in brain glucose metabolism. However, such studies have not been done in female alcoholics. The purpose of this study was to evaluate if similar or worse brain metabolic abnormalities occurred in female alcoholics. For this purpose, we measured regional brain metabolism with positron emission tomography and [18F]fluorodeoxyglucose in 10 recently detoxified female alcoholics and compared it with that in 12 age-matched female controls. There were no differences between alcoholics and control females in regional brain glucose metabolism whether we used regions of interest analysis or statistical parameter maps methods. These results do not support a higher toxicity for the effects of alcohol in the female brain, as assessed with regional brain glucose metabolism, because metabolic values in female alcoholics did not differ from those of controls, whereas metabolic values in male alcoholics are generally lower than those in controls. However, this study is confounded by the fact that the severity of alcohol use in these female alcoholics was less than that of the male alcoholics previously investigated in positron emission tomography studies. Future studies in male subjects with alcoholism of moderate severity are required to address gender differences in sensitivity to alcohol effects in brain metabolism. 相似文献
999.
J Regadera G Espa?a MA Roias JA Recio M Nistal CA Suárez-Quian 《Canadian Metallurgical Quarterly》1997,18(6):623-636
The human vas deferens (VD) is often considered simply as a conduit to transfer mature sperm from the epididymis to the ejaculatory duct. The cells that make up the epithelium of the VD, however, exhibit many characteristics of cells found in more complex epithelia, which are involved in absorption and/or secretion. In the present investigation, morphometry was utilized to characterize in detail the changes incurred by the human VD during its development, growth, and aging and to determine if these changes correlate with testicular maturation. In addition, the specific types of keratins present in the epithelial cells were defined, as well as desmin distribution in the muscular layers, during the various phases of the development, growth, and involution of the human VD. Results of the morphometric study are consistent with the interpretation that the development, growth, and aging of the VD are delayed, but parallel to, the identical phases exhibited by the human testis. Further, a differential expression of distinct keratin types was observed in the VD during the various phases examined in this study. Taken together, these two correlations may suggest that the VD is unlikely to function solely as a conduit for sperm. The rationale for this interpretation is as follows: 1) the complex developmental and maturational changes measured in the present investigation in the human VD are common to other absorptive and/or secretory epithelia; and 2) these changes parallel developmental changes observed in other androgen-dependent epithelia of the male reproductive tract, which also function to contribute components to seminal fluid as well as to provide a conduit for sperm. 相似文献
1000.
JB Gibbs SL Graham GD Hartman KS Koblan NE Kohl CA Omer A Oliff 《Canadian Metallurgical Quarterly》1997,1(2):197-203
BACKGROUND: Intra-arterial regional anaesthesia (IARA) may be useful for ambulatory hand surgery in patients with poor veins. This randomized, double-blind study assessed which of the three doses of lignocaine gives the optimal analgesia with a minimum of adverse effects. METHODS: A preservative-free, alkalinized 0.5% lignocaine 1, 2 or 2.89 mg/kg body weight was injected into the radial arteries of 60 adult patients, allocated to three equal groups, to produce anaesthesia for carpal tunnel releases, capsulotomies, tenosynovectomies, palmar fasciectomies, Z-plastics, arthroplastics, arthrodeses etc. RESULTS: Surgical analgesia and motor block were best in group 3 (P < 0.01), whereas injection and tourniquet pain scores were similar in the three groups. Onset of analgesia was similar in all groups, and varied between 2 and 15 min. Cannulation time, surgery start time and tourniquet time were also similar in all groups, as were operating conditions and patient's acceptance of the method. No significant cardiovascular changes were observed after tourniquet release in any of the groups. Plasma lignocaine concentrations were lowest in group 1 (1 mg/kg) (P < 0.001). Five patients in group 1, seven in group 2 and seventeen in group 3 developed small bruises at the cannulation site (P < 0.001). Six patients (two in group 1, three in group 2 and one in group 3) had minor symptoms of lignocaine toxicity after tourniquet release (NS). No other complications were observed. CONCLUSIONS: The highest dose of lignocaine produces best surgical analgesia, without increasing the risk of toxicity. However, many patients receiving this dose will develop bruises at the injection site, and an occasional patient may need supplemental analgesia. 相似文献