全文获取类型
收费全文 | 6730篇 |
免费 | 4篇 |
专业分类
电工技术 | 24篇 |
综合类 | 1篇 |
化学工业 | 90篇 |
金属工艺 | 4篇 |
机械仪表 | 5篇 |
建筑科学 | 17篇 |
矿业工程 | 3篇 |
能源动力 | 44篇 |
轻工业 | 22篇 |
水利工程 | 2篇 |
石油天然气 | 5篇 |
无线电 | 23篇 |
一般工业技术 | 34篇 |
冶金工业 | 6420篇 |
自动化技术 | 40篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 22篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 15篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 181篇 |
1998年 | 2043篇 |
1997年 | 1140篇 |
1996年 | 743篇 |
1995年 | 376篇 |
1994年 | 333篇 |
1993年 | 395篇 |
1992年 | 50篇 |
1991年 | 100篇 |
1990年 | 76篇 |
1989年 | 86篇 |
1988年 | 84篇 |
1987年 | 89篇 |
1986年 | 78篇 |
1985年 | 79篇 |
1984年 | 10篇 |
1983年 | 18篇 |
1982年 | 43篇 |
1981年 | 49篇 |
1980年 | 44篇 |
1979年 | 5篇 |
1978年 | 17篇 |
1977年 | 161篇 |
1976年 | 324篇 |
1975年 | 15篇 |
1973年 | 7篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1955年 | 8篇 |
排序方式: 共有6734条查询结果,搜索用时 15 毫秒
51.
Purified Semliki forest virus in aerosols is inactivated rapidly at 40% and above 70% relative humidity. At all humidities tested the decay of virus infectivity runs parallel with the decrease in hemagglutination activity, whereas the biological integrity of the virus ribonucleic acid is preserved. Also, free infectious ribonucleic acid is stable after spraying at all relative humidities. Evidence is presented for the hypothesis that above 20% relative humidity, virus inactivation in aersols is mainly due to surface-dependent factors, damaging the virus coat. 相似文献
52.
Pulmonary effects of chronic exposure to airborne cadmium 总被引:1,自引:0,他引:1
In haemoglobinometry grave errors are still being made even though an internationally accepted standardized method is available for the determination of the haemoglobin content of blood. Up to the present only haemiglobincyanide reference solutions have been available on a wide scale to check the measuring stage of the standardized haemiglobincyanide method. These reference solutions are shown to remain stable, under proper storage conditions, for more than 10 years. Concentrated haemoglobin solutions have become available recently, offering the possibility to control the dilution and conversion steps of the haemiglobincyanide method. Such a solution is shown to remain stable, under proper storage conditions, for at least a year. Using both haemiglobincyanide reference solutions and concentrated haemoglobin solutions, as well as having the possibility of checking the cyanide content of the reagent used, an acceptable intra-laboratory control program may now be set up. 相似文献
53.
The cheating and intention of a partner as determinants of evaluative decisions among juvenile offenders 总被引:1,自引:0,他引:1
A 17 year-old male, who was mentally and bodily retarded from the age of 7 years. At the age of 16 years, several neurological signs appeared. Pathologically, there was widespread myelin loss and tissue sponginess in the white matter of the cerebrum and cerebellum, bilaterally and symmetrically. A great many Alzheimer type II glia and Opalski glia were widely distributed in the cerebral cortex and the basal ganglia. Despite severe destruction of the white matter, mesenchymal and gliofibre proliferation were not noticed. In the liver, Laennec's cirrhosis and a great many copper granules in the cytoplasm of the parenchymal cells were identified. From the above mentioned findings the present case, being a new type, could be called "Demyelinating type of Wilson's disease". 相似文献
54.
Replies to L. E. Beutler et al (see record 1973-31675-001) who presented data in defense of using the number of patients rather than the number of therapists as the unit of analysis for assessing the reliability of process psychotherapy variables. The present paper presents data suggesting that the Beutler et al interpretation of their research findings is not valid. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
56.
A procedure for the preparation of highly purified pig prothrombin is described. Compared to the initial clotting activity of the starting plasma, this protein was purified 776 times with a final yield of 8 per cent. The purified zymogen showed a specific activity of 1,460 NH units/mg of protein , a molecular weight of 65,000 as determined by SDS-polyacrylamide disc gel electroesis, E 1.0 mg/ml 1.0 cm, 280 nm = 1.45 at pH 7.0 and the following amino acid composition: Asx 51, Thr 38, Glx 62, Pro 23, Gly44, Ala 25, Half-Cys 30, Val 35, Met 3, Ile 30, Leu 32, Tyr 19, Phe 22, Lys 36, His 8, Arg 28, and Trp 13, which accounts for a minimum molecular weight of 59,370 (carbohydrates not computed). Alanine was found as the only N-terminal residue. Carboxypeptidases A and B failed to release any C-terminal residue. By hydrazinolysis however 0.4 mole of serine was released per mole of prothrombin. The activation of crude and chromatographed pig prothrombin was investigated. 相似文献
57.
Antigenic analysis of Chlamydia psittaci, C. trachomatis, and Lymphogranuloma venereum (LGV) revealed basic physicochemical differences among the three chlamydial strains. These were manifested in structural, isoelectric points, absorption spectra, and in the characteristics of the chromophobe-containing proteins. The effective period of sonication for C. psittaci and C. trachomatis is around 60 min during which the linkages most susceptible to external sonication forces were broken, releasing all attainable cellular components. Denaturation studies demonstrated that less than 50% of protein content of C. psittaci was denatured after 1 h of sonication, only 5% in the case of C. trachomatis. The protein and carbohydrate content of the most reactive fractions in macrophage-spreading inhibition test were different for LGV and C. trachomatis. The structural differences appear to determine the antigenic properties observed among the chlamydial strains as well as the specificity and probably the mechanisms (s) of cellular immune reactivity to Chlamydiae. This in turn may explain the failure of chlamydial vaccines, prepared from stock strains, to protect immunized children against 'wild' chlamydial strains. 相似文献
58.
The author discussed the increase in the frequency of traumatic paralyses of the ocular muscles, and reported 6 cases of inferior oblique muscle paresis caused by local blunt or sharp traumas (haematoma, contusion, rupture, incarceration) and one case of traumatic Brownian pseudo-paralysis. The localisation of the injuries in 3 cases was on the inferior temporal part and in the other 3 cases on the superior part of the bulbar conjunctiva. Atypical horizontal deviation and characteristic vertical deviation, torsion and torticollis were observed in the majority of cases. One patient recovered spontaneously. 3 patients became asymptomatic after correction by prisms and one after recession of contralateral superior rectus muscle. The symptoms remained unchanged in the case of a "blow out" fracture (in spite of operation) and a Brown's syndrome (without treatment). 相似文献
59.
The development of independence in daily living skills of 256 patients with spina bifida was assessed by means of a new Functional Activities scoring system. The score was derived from nine categories of activity; five are to do with self-care, three with locomotion and one with social interaction. The reasons for the variation in achievement between individuals with the same degree of paralysis are discussed, as are the differences in learning curves for single activities. The scoring system enables a quantitative assessment to be made of the current status of an individual patient, and enables more realistic therapeutic goals to be set. 相似文献
60.
M Colinabarranco González MW Orozco Romo JC Vadillo N Valverde 《Canadian Metallurgical Quarterly》1976,41(3-4):84-89
Plasmatic renin levels were measured in 17 adults patients with diagnosis of diabetes mellitus and systemic arterial hypertension. None of them was under antihypertensive therapy. The results obtained showed lessening of renin levels in 13 cases, normal levels in two cases, no valuable results in one and Significative increase in other. Renal biopsy was performed in 8 patients and in all cases nephropathies were demonstrated; only one of them had normal renin levels. We have concluded that more than 75% of our cases were hyporeninemic hypertensive patients. Our findings are according with other medical papers that have been published before. Finally, we try to explain the mechanisms upon which theorethical causes are based. 相似文献