全文获取类型
收费全文 | 4762篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 17篇 |
能源动力 | 1篇 |
轻工业 | 2篇 |
无线电 | 1篇 |
一般工业技术 | 2篇 |
冶金工业 | 4736篇 |
自动化技术 | 3篇 |
出版年
2020年 | 2篇 |
2018年 | 1篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 141篇 |
1998年 | 1443篇 |
1997年 | 855篇 |
1996年 | 533篇 |
1995年 | 296篇 |
1994年 | 259篇 |
1993年 | 289篇 |
1992年 | 29篇 |
1991年 | 54篇 |
1990年 | 54篇 |
1989年 | 59篇 |
1988年 | 57篇 |
1987年 | 53篇 |
1986年 | 62篇 |
1985年 | 44篇 |
1983年 | 8篇 |
1982年 | 21篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 2篇 |
1978年 | 12篇 |
1977年 | 124篇 |
1976年 | 277篇 |
1975年 | 7篇 |
1962年 | 1篇 |
1955年 | 5篇 |
排序方式: 共有4763条查询结果,搜索用时 15 毫秒
51.
52.
JJ Strain 《Canadian Metallurgical Quarterly》1977,134(3):253-256
Total amounts of antimicrobial drugs used to treat inpatients during 1975 were calculated for three Canadian general hospitals, one of them the principal teaching hospital of a medical school. Use of drugs was compared with that reported for Boston City Hospital during periods when antimicrobial therapy was and was not supervised by infectious disease consultants. Ampicillin, tetracyclines, cephalosporins, erythromycin and aminoglycosides for prophylactic oral administration were used excessively in the three hospitals. The degree of overuse was comparable to that at Boston City Hospital during years when drug use was uncontrolled. Overuse or improper choice of antimicrobial drug decreases the quality of patient care and increases its cost. More rigorous education is needed for both medical students and practising physicians in the rational use of antimicrobial drugs. Informal consultation with an infectious disease unit should be required before certain overly popular or toxic antibiotics are administered to hospitalized patients. 相似文献
53.
The hypothesis that physiognomic perception, rather than being an immature mode, characterizing, in particular, children, primitives, and schizophrenics, is, instead, a basic mode, was tested. Children of both Eastern and Western parentage in Grades 3, 5, 6, and 11 were given the Physiognomic Form Perception Test, an instrument specially developed for testing physiognimic perception. No decrease with age in such perception was noted. Although there was a tendency for scores to increase with age for girls of Eastern origin, in general the scores do not increase with age. Physiognomic perception is apparently not acquired. Sex differences were not significant. 相似文献
54.
Ro 2-2985 increased mean arterial blood pressure in both the venous bypass preparation and the intact animal; however, total peripheral resistance increased in the venous bypass preparation with a constant cardiac output but decreased in the intact animal with an increase in cardiac output. These observations indicate a drug-related increase in the distensibility of the aorta at the same arterial pressure. In vivo ventricular function curves were shifted to the left indicating enhanced myocardial performance with the translocation of large volumes of blood to the central circulation since total body venous compliance was significantly decreased. Beta adrenergic blocking doses of propranolol blocked the positive inotropic effect of Ro 2-2985 while myocardial depression produced by toxic doses of propranolol was reversed. This observation suggests several mechanisms for the Ro 2-2985 metabolic mediation of myocardial muscle contraction. The cardiovascular effects produced by Ro 2-2985 were accompanied by a marked polycythemia and a decrease in plasma volume without a change in total circulating blood volume, while blood glucose values showed a nonsignificant increase. Ro 2-2985 produced a marked increase in cardiac output. The increase in myocardial performance appears to be complex since myocardial force of contraction, dT/dt, dP/dt:P40 and Vmax were all increased. RO 2-2985 increased coronary flow without an increase in resistance. There were no significant increases in myocardial arteriovenous glucose, lactate, K+, Ca++, Na+ or Cl. 相似文献
55.
ES Flamm HB Demopoulos ML Seligman JJ Tomasula V De Crescito J Ransohoff 《Canadian Metallurgical Quarterly》1977,46(3):328-335
Two models have been used to study the effects of ethanol on injuries of the central nervous system. The spinal cords of cats were injured by delivering a 200 gm-cm impact to the exposed dura mater. A second group of animals received a similar injury to the exposed dura mater overlying the cerebral hemispheres. The animals were divided into two groups, those that received an infusion of ethanol before injury, and control animals that received no ethanol. The parameters of injury used in this model produced small and insignificant lesions in those animals that received no ethanol; however, when the animals were pretreated with ethanol, a considerable increase in the extent of the injury was noted. These include alterations in membranes-bound enzymes and clotting mechanisms, and alteration of cell membranes through abnormal free radical reactions. 相似文献
56.
57.
Clinical and morphologic observations are described in a 46 year old woman with fatal trichinosis. Attention is called to the occurrence of extensive ventricular endocardial damage with superimposed thrombosis; Evidence is presented to indicate that the most likely cause of the endocardial damage is the associated eosinophilia. The mechanism by which eosinophils damage endocardium, however, remains obscure. 相似文献
58.
JA Beatty JJ Callanan A Terry O Jarrett JC Neil 《Canadian Metallurgical Quarterly》1998,72(1):767-771
We describe the histopathological, immunohistochemical, and molecular characterization of a lymphoma arising in a 7-year-old cat following experimental infection with feline immunodeficiency virus (FIV). The tumor was high grade and of B-cell lineage. The transformed cell had an immature phenotype (CD79a+, CD79b-, CD21-, immunoglobulin heavy and light chain negative), confirmed by antigen receptor gene analysis, which showed germ line configuration. Single-copy, clonally integrated FIV provirus was detected in tumor genomic DNA. FIV p24 antigen was not detected in tumor cells by immunostaining. This study provides the first evidence that the feline lentivirus may play a direct role in cell transformation under certain circumstances. 相似文献
59.
60.