全文获取类型
收费全文 | 2477篇 |
免费 | 8篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 48篇 |
金属工艺 | 2篇 |
机械仪表 | 12篇 |
建筑科学 | 17篇 |
能源动力 | 4篇 |
轻工业 | 30篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 65篇 |
一般工业技术 | 67篇 |
冶金工业 | 2158篇 |
原子能技术 | 15篇 |
自动化技术 | 57篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 7篇 |
2013年 | 20篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 84篇 |
1998年 | 643篇 |
1997年 | 374篇 |
1996年 | 221篇 |
1995年 | 123篇 |
1994年 | 114篇 |
1993年 | 149篇 |
1992年 | 26篇 |
1991年 | 38篇 |
1990年 | 34篇 |
1989年 | 50篇 |
1988年 | 40篇 |
1987年 | 44篇 |
1986年 | 42篇 |
1985年 | 22篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 54篇 |
1976年 | 116篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有2485条查询结果,搜索用时 15 毫秒
31.
F Deák á Horváth á Kiss Z Seres A Galonsky CK Gelbke H Hama L Heilbronn D Krofcheck WG Lynch DW Sackett HR Schelin MB Tsang J Kasagi T Murakami 《Canadian Metallurgical Quarterly》1995,52(1):219-227
An extruding wire knife was used to give adult male CFHB rats a minimally traumatic unilateral mechanical lesion of the medial forebrain bundle. In addition, some rats received bilateral intrastriatal injections of one of three fluorescent retrograde tracers either eight days before or eight days after the lesion. Injections made after the lesion revealed that about half of the animals had complete lesions of the nigrostriatal tract, while the other half were incompletely lesioned, the mean proportion of non-axotomized neurons being 23%. Over the 10 weeks following the lesions, the number of tyrosine hydroxylase-immunoreactive cells in the lesioned substantia nigra fell linearly, reaching a mean of 29% of that of the control substantia nigra. In the animals which were completely lesioned, neuronal survival at 10 weeks varied between 6 and 12%. That the disappearance of tyrosine hydroxylase-immunoreactive neurons was due to cell death rather than the loss of tyrosine hydroxylase itself was confirmed by labelling the cells with Fluoro Gold before axotomy; the tracer was seen in survival neurons, microglia and in a few involuted neurons which continued to be tyrosine hydroxylase-immunoreactive. This percentage of neurons surviving axotomy corresponds to the proportion of substantia nigra neurons which project to the contralateral striatum, and these neurons were in the region of the substantia nigra from which the contralateral projection originated. It is concluded that following mechanical transection of the nigrostriatal tract, all truly axotomized substantia nigra neurons die over a period of about 10 weeks. 相似文献
32.
33.
We report two patients with paraneoplastic limbic and brainstem encephalitis associated with occult nonmetastatic testicular seminoma. In each patient, the neoplasm was detectable only by testicular ultrasonography. Male patients with this syndrome in whom lung cancer is not found should undergo testicular ultrasonography as part of the search for an extrapulmonary neoplasm. A normal clinical testicular examination is insufficient to exclude an occult seminoma. 相似文献
34.
This study compared prototype and rote instruction of English names for Chinese visual characters. In the prototype condition, participants were taught the meaning of the prototype that served as the distinctive feature of multicomponent characters. In the rote condition, participants traced the character and wrote its translation. Participants learned more rapidly and maintained more words in the prototype condition. 相似文献
35.
36.
37.
38.
OBJECTIVE: To determine whether concurrent intravenous administration of the loop diuretic ethacrynic acid potentiates the toxicity of the aminoglycoside antibiotic gentamicin applied topically on the round window. STUDY DESIGN: The authors studied the effects on cochlear sensitivity of co-administered intracardiac ethacrynic acid (40 mg/kg) and high-dose topical gentamicin solution (100%) applied to the round window. Comparisons were made with animals receiving ethacrynic acid plus systemic gentamicin (100 mg/kg); topical gentamicin alone; systemic gentamicin alone; and intravenous ethacrynic acid alone. METHODS: Experiments were carried out on pigmented guinea pigs weighing 400 to 500 g. Changes in cochlear function were characterized by monitoring shifts in compound action potential (CAP) thresholds by use of chronic indwelling electrodes implanted at the round window, vertex, and contralateral mastoid. RESULTS: After 20 days animals receiving ethacrynic acid in combination with topical gentamicin to the round window failed to demonstrate a significant deterioration in cochlear sensitivity, whereas all animals receiving systemic gentamicin plus ethacrynic acid experienced profound increases in CAP thresholds. CONCLUSIONS: This study supports the contention that ethacrynic acid potentiates aminoglycoside ototoxicity by facilitating the entry of the antibiotics from the systemic circulation into the endolymph. In addition, this study answers important clinical concerns regarding the safety of the use of topical aminoglycoside agents in combination with loop diuretics. 相似文献
39.
OBJECTIVE: Multivariate statistical methods were used to identify patient-related variables that predicted length of stay in a single psychiatric facility. The study investigated whether these variables remained stable over time and could be used to provide individual physicians with data on length of stay adjusted for differences in clinical caseloads and to detect trends in the physicians' practice patterns. METHODS: Data on all patients discharged over two six-month periods were collected at an acute psychiatric inpatient facility. Stepwise multiple regression analyses were conducted on the two datasets. RESULTS: The results from both analyses revealed that five variables significantly predicted length of stay and were stable over time. They were a primary diagnosis of schizophrenia, the number of previous admissions, a primary diagnosis of a mood disorder, age, and a secondary diagnosis of an alcohol- or other drug-related disorder. For some physicians, the mean length of stay of their patients differed significantly from the length predicted by the regression model--generally, it was shorter. CONCLUSIONS: The results demonstrate that patient-related predictors of length of stay in a single psychiatric hospital can be identified using relatively simple statistical procedures and can be consistent across a large dataset and over time. 相似文献
40.
DW Bearg 《Canadian Metallurgical Quarterly》1998,59(9):636-641
This article summarizes an approach for improving the indoor air quality (IAQ) in a building by providing feedback on the performance of the ventilation system. The delivery of adequate quantities of ventilation to all building occupants is necessary for the achievement of good IAQ. Feedback on the performance includes information on the adequacy of ventilation provided, the effectiveness of the distribution of this air, the adequacy of the duration of operation of the ventilation system, and the identification of leakage into the return plenum, either of outdoor or supply air. Keeping track of ventilation system performance is important not only in terms of maintaining good IAQ, but also making sure that this system continues to perform as intended after changes in building use. Information on the performance of the ventilation system is achieved by means of an automated sampling system that draws air from multiple locations and delivers it to both a carbon dioxide monitor and dew point sensor. The use of single shared sensors facilitates calibration checks as well as helps to guarantee data integrity. This approach to monitoring a building's ventilation system offers the possibility of achieving sustainable performance of this important aspect of good IAQ. 相似文献