全文获取类型
收费全文 | 3908篇 |
免费 | 2篇 |
专业分类
化学工业 | 20篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
轻工业 | 13篇 |
石油天然气 | 2篇 |
无线电 | 4篇 |
一般工业技术 | 4篇 |
冶金工业 | 3852篇 |
自动化技术 | 10篇 |
出版年
2023年 | 2篇 |
2020年 | 1篇 |
2018年 | 3篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2003年 | 11篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 117篇 |
1998年 | 1263篇 |
1997年 | 732篇 |
1996年 | 476篇 |
1995年 | 244篇 |
1994年 | 167篇 |
1993年 | 222篇 |
1992年 | 20篇 |
1991年 | 45篇 |
1990年 | 43篇 |
1989年 | 41篇 |
1988年 | 48篇 |
1987年 | 30篇 |
1986年 | 36篇 |
1985年 | 32篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 29篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 76篇 |
1976年 | 179篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有3910条查询结果,搜索用时 0 毫秒
991.
992.
BACKGROUND AND OBJECTIVE: Hypertrophic scarring and rigid scar contracture are disorders of wound healing for which there is presently no effective therapy. The dermal fibroblast plays a major role in scar fibrillogenesis and contracture. The objective of this study was to establish a selective and effective method to destroy fibroblasts. STUDY DESIGN/MATERIALS AND METHODS: An antifibroblast conjugate was synthesized by covalent attachment of the antifibroblast antibody PR2D3 to the photosensitizer Sn-chlorin e6. Fibroblasts were cultured in fibroblast-populated collagen lattices (FPCLs), incubated with the conjugate and exposed to light. The effect of the treatment on cell viability and the rate of contraction of the FPCL were assessed. RESULTS: The toxicity of antifibroblast conjugates increased with increasing conjugate concentration, light dose, and number of photosensitizers per antibody molecule, until nearly complete killing was achieved. The rate of lattice contraction after irradiation linearly correlated with the remaining viable fraction of fibroblasts. These conjugates were not cytotoxic to keratinocytes cultured on collagen lattices, and nonspecific conjugates could not cause significant fibroblast killing. Spatial selectivity was demonstrated using a light mask. CONCLUSIONS: Antibody-targeted photolysis is an effective and selective technique for controlling FPCL contraction in vitro and may have potential in vivo applications to modulate extracellular matrix remodeling by connective tissue cells. 相似文献
993.
994.
OBJECTIVE: To establish whether variations exist in the philosophy and approach of three groups of childbirth teachers working in different organisations in the UK. PARTICIPANTS: Two midwifery Parentcraft Sisters working in the UK maternity services, three National Childbirth Trust Antenatal Teachers and two Active Birth Teachers working in the voluntary sector, and two Midwife Teachers. METHOD: Semi-structured interviews were tape-recorded, transcribed and analysed using a grounded theory approach to identify common categories. FINDINGS: All three groups of teachers identified similar aims for antenatal education, with the need to build clients' confidence in their ability to give birth and care for their babies as the most important. However, the process by which the various teachers attempted to realise their aims appeared to be very different. IMPLICATIONS FOR PRACTICE: In order to ensure the prioritization of antenatal education with purchasers and providers, childbirth teachers need to define more clearly the criteria by which it can be audited. 相似文献
995.
First degree atrioventricular block occurred in a 69-year-old patient with a calcified atrioventricular septum tumour. The patient suffered several episodes of syncope and the only abnormality found in the routine clinical work-up was a remarkable first degree atrioventricular block. The echocardiogram, computed tomography (CT) and the magnetic resonance imaging (MRI) procedure showed a calcified tumour in the posterior part of the left ventricle, between the left atrium and left ventricle, just beneath the aortic root spreading to the interventricular septum. It was suggested that the first degree atrioventricular block was caused by the tumour. The symptoms were relieved by implantation of permanent cardiac pacemaker. 相似文献
996.
997.
ML Janssen-Heijnen RM Schipper PJ Klinkhamer MA Crommelin WJ Mooi JW Coebergh 《Canadian Metallurgical Quarterly》1998,77(11):2053-2057
We studied the incidence and survival rates for the histological subtypes of non-small-cell lung cancer, using data from the Eindhoven Cancer Registry over the period 1975-94. The proportions with adenocarcinoma and large-cell undifferentiated carcinoma increased from 11% to 21% and from 11% to 15%, respectively, while those with squamous cell carcinoma decreased from 78% to 62%. The increase in the proportion with adenocarcinoma was only found among men. Although the overall prognosis for patients with non-small-cell lung cancer has remained unchanged, there have been divergent changes between morphological subtypes. Relative 1- and 5-year survival rates for squamous cell carcinoma have improved slightly from 48% to 51% and from 14% to 16%, respectively, because of an increase in the proportion with localized tumours, while relative 1- and 5-year survival rates for adenocarcinoma have decreased from 59% to 45% and from 28% to 18%, respectively, because of a decrease in localized tumours. The proportion with localized tumours and the relative 1-year survival for large-cell undifferentiated carcinoma (about 18% and 30% respectively) were markedly lower. The divergent trends could partly be explained by changes in the histological classification of tumours, but changes in patterns of risk and biological behaviour of adenocarcinoma cannot be excluded. 相似文献
998.
ML Genova C Bovina M Marchetti F Pallotti C Tietz G Biagini A Pugnaloni C Viticchi A Gorini RF Villa G Lenaz 《Canadian Metallurgical Quarterly》1997,410(2-3):467-469
We investigated NADH oxidation in non-synaptic and synaptic mitochondria from brain cortex of 4- and 24-month-old rats. The NADH oxidase activity was significantly lower in non-synaptic mitochondria from aged rats; we also found a significant decrease of sensitivity of NADH oxidation to the specific Complex I inhibitor, rotenone. Since the rotenone-binding site encompasses Complex I subunits encoded by mtDNA, these results are in accordance with the mitochondrial theory of aging, whereby somatic mtDNA mutations are at the basis of cellular senescence. Accordingly, a 5 kb deletion was detected only in the cortex of the aged animals. 相似文献
999.
A new instrument for laparoscopic access consists of a trocarless, reusable, visual-access cannula with an external thread that ends in a blunt tip. The device has no sharp ends or moving parts. The cannula does not transect but radially stretches and elevates vessels, fascia, and muscle fibers, preserving the fascia's natural gridiron shutter mechanism at the access site. The outer thread stabilizes the cannula, and no fascial suture is necessary. In a prospective clinical trial between 1994 and 1997, the instrument was used in 203 patients requiring 234 access ports for diagnostic and operative laparoscopies. No device-related complications or failed attempts were recorded. The cannula caused less tissue trauma at access sites, and may decrease the frequency of hernias and postoperative access site pain. 相似文献
1000.
C Gicquel ML Raffin-Sanson V Gaston X Bertagna PF Plouin M Schlumberger A Louvel JP Luton Y Le Bouc 《Canadian Metallurgical Quarterly》1997,82(8):2559-2565
Abnormalities of the 11p15 region with overexpression of the normally imprinted insulin-like growth factor II (IGF-II) gene have been implicated in the pathogenesis of adrenocortical tumors. We evaluated the frequency and distribution of 11p15 loss of heterozygosity (LOH) and IGF-II gene overexpression in a series of 82 sporadic adrenocortical tumors, screened for pathological functional imprinting of the 11p15 region in tumors not exhibiting LOH and evaluated the expression of H19 gene in these tumors. Abnormalities of the 11p15 region as LOH (loss of the maternal allele and duplication of the paternal allele) and/or IGF-II gene overexpression are frequent features of the malignant state and were found in 27 of 29 (93.1%) of the malignant tumors and in only 3 of 35 (8.6%) of the benign tumors. Tumors without abnormality of the 11p15 region (mainly benign tumors) did not exhibit pathological functional imprinting. In tumors with mosaicism for 11p15 LOH, biallelic expression of the IGF-II gene was constant in the tumor cell contingent not undergoing LOH. Abrogation of H19 expression correlated with the loss of the maternal allele (LOH or pathological imprinting), but did not always correlate with overexpression of the IGF-II gene. These data indicate the involvement of dysregulation of the 11p15 region in late steps of adrenocortical tumorigenesis and provide us with new molecular markers for a better diagnostic and prognostic evaluation of adrenocortical tumors. 相似文献