全文获取类型
收费全文 | 3452篇 |
免费 | 103篇 |
国内免费 | 87篇 |
专业分类
电工技术 | 34篇 |
综合类 | 123篇 |
化学工业 | 108篇 |
金属工艺 | 116篇 |
机械仪表 | 72篇 |
建筑科学 | 222篇 |
矿业工程 | 31篇 |
能源动力 | 15篇 |
轻工业 | 73篇 |
水利工程 | 32篇 |
石油天然气 | 40篇 |
武器工业 | 24篇 |
无线电 | 101篇 |
一般工业技术 | 241篇 |
冶金工业 | 2306篇 |
原子能技术 | 27篇 |
自动化技术 | 77篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 47篇 |
2020年 | 37篇 |
2019年 | 37篇 |
2018年 | 36篇 |
2017年 | 35篇 |
2016年 | 23篇 |
2015年 | 43篇 |
2014年 | 43篇 |
2013年 | 72篇 |
2012年 | 77篇 |
2011年 | 75篇 |
2010年 | 71篇 |
2009年 | 76篇 |
2008年 | 64篇 |
2007年 | 85篇 |
2006年 | 101篇 |
2005年 | 68篇 |
2004年 | 51篇 |
2003年 | 50篇 |
2002年 | 45篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 95篇 |
1998年 | 677篇 |
1997年 | 423篇 |
1996年 | 266篇 |
1995年 | 158篇 |
1994年 | 134篇 |
1993年 | 178篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 31篇 |
1989年 | 37篇 |
1988年 | 22篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1978年 | 6篇 |
1977年 | 59篇 |
1976年 | 135篇 |
1975年 | 6篇 |
1955年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有3642条查询结果,搜索用时 8 毫秒
991.
BA Parker 《Canadian Metallurgical Quarterly》1993,31(3):19-21
1. Families of persons with severe mental illness are often anguished because of stressors and are unprepared to be caregivers. Their needs must be addressed by mental health professionals. 2. Family members may experience grief, guilt, anger, powerlessness, and fear. 3. Education and peer groups may be most helpful to family members in dealing with their distress and becoming better prepared caregivers. 相似文献
992.
SA Rezikian AF Voevodin IN Klots MS Shtutman BA Lapin 《Canadian Metallurgical Quarterly》1993,38(2):76-78
We characterized the simian immunodeficiency virus isolated from Cercopithecus aethiops (subspecies C. a. pygerythrus) originating from Kenya. SIV was isolated and continuously produced with the MOLT4 clone 8 cell line and was designated as SIV-SU1. SIV-SU1 isolate replicated with high efficiency in MOLT4 clone 8, MT-2 with moderate efficiency in CEM x 174 and with poor efficiency in HUT-78, U937, C8166. The infection of MT-2, C8166 and HUT-78 resulted in extensive cell killing. Western blotting of purified preparations of SIV-SU1 revealed viral proteins of 130, 68, 55, 41, 24, 17 kDa. Cross-reactivity of SIV-SU1 proteins with HIV-1, HIV-2, SIVmac, SIVsm, SIVmnd was studied by radioimmunoprecipitation assay. The most extensive cross-reactivity was observed with SIVmac. Total cellular DNA from chronically infected cells was hybridized to SIVagm266 DNA probes. Detection of cross-hybridizing DNA sequences required very low stringency, and the restriction endonuclease fragmentation pattern of SIV-SU1 differed from other SIVs. 相似文献
993.
BACKGROUND: Harlequin ichthyosis is an inherited skin disorder that usually results in death shortly after birth. Although the clinical features of this disorder are well described, the underlying molecular basis is not understood. In this article, we discuss the results of the latest histologic, immunochemical, and Western immunoblotting studies done in our laboratory and propose a hypothesis for molecular basis of this disorder. OBSERVATIONS: Previous experiments done in our laboratory show suggestive evidence for defective lipid synthesis and protein dephosphorylation in harlequin ichthyosis. Our latest study shows that the catalytic subunit of one of the most prevalent protein phosphatase, type 2A protein phosphatase, appears to be altered in some cases of type 2 harlequin ichthyosis. CONCLUSIONS: Based on these observations and the known functions of protein phosphatase in keratinocytes, we hypothesize that the underlying molecular basis of harlequin ichthyosis may be related to mutations affecting protein dephosphorylation. We further describe approaches by which this hypothesis can be tested. 相似文献
994.
995.
B Vitiello RC Veith SE Molchan RA Martinez BA Lawlor J Radcliffe JL Hill T Sunderland 《Canadian Metallurgical Quarterly》1993,34(7):428-433
Abnormalities of the noradrenergic system have been documented in the central nervous system of patients with dementia of the Alzheimer's type (DAT). To evaluate the autonomic sympathetic system in DAT, we measured lying and standing blood pressure (BP), pulse, and plasma epinephrine (E) and norepinephrine (NE) in 60 DAT patients (mean age +/- SD = 65 +/- 8 years), and 20 normal elderly controls. DAT patients had normal baseline findings (BP, pulse, NE, and E). Upon standing, plasma NE and E significantly increased in both DAT patients and controls, without group differences. However, the systolic BP response to standing was reduced in DAT patients compared with the normal controls (repeated measures ANOVA, p < 0.01). This impaired response of the systolic BP on standing was particularly evident in DAT patients with symptoms of depression. Severely impaired DAT patients did not differ in E, NE, BP, pulse, or in orthostatic changes from mild-to-moderately impaired patients. These results suggest that the sympathetic response to the stress of standing is functionally impaired in DAT. This deficit was especially evident when DAT was accompanied by depression, consistent with prior studies in non-demented depressed patients. 相似文献
996.
997.
Using the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone, we have detected a lipid-derived carbon-centered free radical generated from intact L1210 lymphoblastic leukemia cells that were exposed to 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (edelfosine or ET-18-OCH3) and oxidative stress. The spectral characteristics, including hyperfine splitting constants of aN = 15.61G and aH = 2.65G, were consistent with the spin trapping of an alkyl radical. Radical detection required iron and prior enrichment of cellular components with the polyunsaturated fatty acid docosahexaenoic acid; unmodified cells failed to generate detectable free radical. Ascorbate further enhanced radical generation. The detection of lipid-derived free radicals when intact cells are exposed to edelfosine provides further evidence that oxidative stress may play an important role in the cytotoxic mechanism of this class of anticancer drug. 相似文献
998.
BA Rubin 《Canadian Metallurgical Quarterly》1993,40(4):303-323
Adenoviruses produce a variety of serious diseases in people of all ages. The mode of transmission of adenovirus infections includes respiratory, fomite, droplet, venereal, and faecal-oral routes. They have been shown to spread with ease in AIDS patients, in young children and in hospitalized patients. A constant rate of about 8% of world-wide reported virus infections were observed to be due to adenovirus infections. In the military, it can cause serious respiratory disease (ARD) of epidemic proportion in new recruits. The present commercial vaccine is prepared in unique triple-layered tablets containing live lyophilized virus. This vaccine has been taken by more than ten million subjects during the past 25 years with no adverse reaction and with near total eradication of ARD epidemics among new recruits at training centers. As the epidemiology of adenovirus diseases becomes more clearly defined, the need for and the possible role of potential vaccines, is becoming more evident. 相似文献
999.
Standards of care have recently been established for the diagnosis and treatment of child abuse. This article addresses the key areas of treatment with which each primary care physician should be acquainted. As part of a community-based approach to this problem, the physician can positively impact the prognosis for the victimized child and his or her family. 相似文献
1000.
M Tieder J Blonder S Strauss U Shaked J Maor D Gabizon H Manor BA Sela 《Canadian Metallurgical Quarterly》1993,64(4):526-531
The treatment of X-linked hypophosphatemia (XLH) consists of phosphate and vitamin D3 derivatives. Transient hypercalciuria and hypercalcemia are well-known signs of vitamin D intoxication. Despite urinary calcium excretion control, the danger of nephrocalcinosis in treated patients has been emphasized. It has recently been suggested that hyperoxaluria might be a causative factor of nephrocalcinosis other than calcium in phosphate-treated XLH patients. We measured urinary oxalate and phosphate excretion in 12 patients with the syndrome of hereditary hypophosphatemic rickets with hypercalciuria (HHRH) receiving only oral phosphates and in 5 XLH patients receiving both oral phosphates and vitamin D. No correlation was found between the dosage of phosphate supplements or urinary phosphate excretion and urinary oxalate excretion, in either group of patients. Nephrocalcinosis, presenting as hyperechogenicity of the medullary pyramids, was found in 2 of the 5 XLH patients and only in 2 HHRH patients who had been treated with excessive doses of vitamin D2 and calcium, prior to the true diagnosis being established. We conclude: (1) hyperoxaluria is not a cause of nephrocalcinosis in phosphate-treated patients with hereditary hypophosphatemic rickets; (2) prolonged phosphate treatment alone does not induce nephrocalcinosis in HHRH patients, and (3) we believe that in XLH patients, nephrocalcinosis is essentially due to vitamin D overdosage at some stage, or noncompliance in phosphate intake, leading to repeated undetected hypercalciuric periods. 相似文献