全文获取类型
收费全文 | 3452篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
综合类 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 3篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
轻工业 | 11篇 |
无线电 | 6篇 |
一般工业技术 | 9篇 |
冶金工业 | 3389篇 |
自动化技术 | 9篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2014年 | 2篇 |
2012年 | 5篇 |
2011年 | 1篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 127篇 |
1998年 | 1150篇 |
1997年 | 592篇 |
1996年 | 415篇 |
1995年 | 200篇 |
1994年 | 191篇 |
1993年 | 180篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 44篇 |
1989年 | 43篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 39篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 53篇 |
1976年 | 127篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有3454条查询结果,搜索用时 11 毫秒
141.
A recent report has noted an association between Helicobacter pylori and hyperemesis gravidarum. We present two cases in which first-trimester patients with severe hyperemesis gravidarum requiring intravenous fluid replacement were placed on oral erythromycin therapy for other nonrelated conditions. Surprisingly, marked rapid improvement of the hyperemesis gravidarum was observed with complete resolution of all symptomatology. Both these patients tested seropositive for Helicobacter pylori. These unexpected, marked therapeutic responses are consistent with the recently reported association between hyperemesis gravidarum and Helicobacter pylori and possibly suggest a new therapeutic modality for similar patients. 相似文献
142.
BACKGROUND AND PURPOSE: Many stroke models in rats are based on occlusion of the middle cerebral artery, which supplies a significant portion of multifunctional cortical and deep structures in the cerebral hemisphere. The purpose of this study was to develop a model for direct observation in real time of blood flow in and around focal ischemic regions of the cortex of known function. METHODS: Cranial windows were placed over the parietal cortex of adult Wistar and Sprague-Dawley rats anesthetized with ketamine and xylazine. Whisker barrel cortex responding to stimulation of the contralateral whiskers was identified by an intrinsic optical signal. Transits of vital dyes were recorded by videomicroscopy before and after ligation of three to six branches and major collaterals of the middle cerebral artery through the dura. Infarcts were demonstrated with triphenyl-tetrazolium chloride staining; their relation to barrel cortex was determined by Nissl and cytochrome oxidase histology. RESULTS: Reduced blood flow in small ischemic regions was outlined by patient blue violet in the surrounding nonischemic area; arteriovenous latencies increased more than four times in ischemic cortex. Infarcts,typically 3 mm or less, were seen at 24 hours in 8 of 16 Wistar and 9 of 9 Sprague-Dawley rats. The ministrokes were confirmed by histology to be in the somatosensory cortex. CONCLUSIONS: This model of local ischemia, produced deliberately in the functionally defined barrel cortex in rats, leads to ministrokes. Changes can be followed by videomicroscopy as they develop, and processes of recovery can potentially be monitored. Infarcts are confirmed by histology for their location and extent in the somatic representation. 相似文献
143.
144.
The purpose of this study was to compare the clinical efficacy of scaling and root planing alone versus tetracycline fiber therapy used adjunctively with scaling and root planing in the treatment of nonresponsive active periodontitis in patients under supportive periodontal therapy. Thirty patients who were receiving supportive treatment and had at least two nonadjacent periodontitis sites with a probing depth of between 4 and 8 mm and bleeding on probing, or had aspartate aminotransferase (AST) levels above 800 microIU in the gingival crevicular fluid in separate quadrants participated in this study. For each patient, the test sites were treated with scaling and root planing plus tetracycline fibers while the control site was treated with scaling and root planing only. Probing depths, clinical attachment levels, gingival recession, AST levels, and bleeding on probing were recorded and subgingival plaque samples were collected at baseline and 1, 3, and 6 months following treatment. At 3 months after treatment, there was a reduction of bleeding on probing and probing depth, and a gain of clinical attachment in both test and control sites. The mean reduction in probing depth of the test sites was 1.38 mm and the attachment gain was 0.8 mm after 6 months. The clinical response obtained at 3 months following therapy was maintained throughout the 6-month follow-up period. However, there were no statistically significant differences between sites treated with scaling and root planing alone and those treated with combined tetracycline therapy. Most of the reductions of probing depths in the fiber group were attributed to gingival recession. The present study did not confirm the efficacy of adjunctive tetracycline fibers in treating nonresponsive sites in maintenance subjects with regard to probing depth reduction or clinical attachment gain. Reinfection of the pockets from untreated sites and extra-crevicular regions may explain the insignificant response to local tetracycline therapy. 相似文献
145.
Fatty masses, especially solid lipomas, in the paediatric abdomen are very rare. We present such a case, that of an 11-year-old boy who was admitted with abdominal pain and distension. The pre-operative diagnosis of lipoma was suggested by US and CT. The diagnosis of simple lipoma arising in the leaves of the small bowel mesentery, without immature cells, was verified microscopically after the operation. The tumour was enucleated from the mesenterium leaving the intestine intact. We underline the importance of US and CT as pre-operative diagnostic tools. 相似文献
146.
147.
KT Izutsu CM Belton A Chan S Fatherazi JP Kanter Y Park RJ Lamont 《Canadian Metallurgical Quarterly》1996,144(2-3):145-150
Porphyromonas gingivalis, a periodontal pathogen can invade primary cultures of gingival epithelial cells. This invasion was significantly inhibited (74-81%) by thapsigargin and 1,2-bis(2-aminophenoxy)ethane-N,N,N1,N1-tetraacetic acid, acetoxymethyl ester (BAPTA/AM), but not by EDTA or amiloride. Release of Ca2+ from an intracellular store and the subsequent increase in cytosolic [Ca2+] may, therefore, be involved in the invasion process, while Ca2+ influx is not. Moreover, cytosolic [Ca2+] was found to increase transiently in about 30% of gingival epithelial cells acutely exposed to P. gingivalis, but not in unexposed cells, or in cells exposed to noninvasive Escherichia coli. These findings indicate that P. gingivalis invasion of epithelial cells is correlated with activation of [Ca2+]-dependent host cell signaling systems. 相似文献
148.
SM Carroll CM Carroll RW Stremel SJ Heilman GR Tobin JH Barker 《Canadian Metallurgical Quarterly》1997,63(4):1034-1040
BACKGROUND: Cardiomyoplasty (CMP) uses the latissimus dorsi muscle (LDM) to assist the heart in cases of cardiac failure. Distal ischemia and necrosis of the LDM is a recognized complication of CMP that can reduce distal muscle function and the mechanical effectiveness of CMP. METHODS: Canine (n = 9) LDMs were subjected to a 10-day period of vascular delay followed by a simulated CMP. Two weeks after simulated CMP (corresponding to the healing delay between CMP and the onset of LDM stimulation used in the clinical setting), LDM perfusion was measured in the distal, middle, and proximal segments of the muscle, and circumferential (distal and middle squeezing muscle function) and longitudinal (proximal pulling muscle function) force generation and fatigue rates were measured. The results were compared with the contralateral nondelayed simulated CMP. RESULTS: Muscle perfusion was significantly (p < 0.05) greater in the distal and middle segments of vascular-delayed LDMs. Circumferential muscle force generation and fatigue rates were significantly (p < 0.05) improved in the vascular-delayed LDMs. CONCLUSIONS: Vascular delay can significantly improve LDM perfusion and function in a model that closely reflects clinical CMP, and the use of vascular delay may improve clinical outcomes in CMP. 相似文献
149.
150.