全文获取类型
收费全文 | 741篇 |
免费 | 0篇 |
专业分类
化学工业 | 6篇 |
金属工艺 | 6篇 |
建筑科学 | 1篇 |
能源动力 | 3篇 |
轻工业 | 2篇 |
水利工程 | 1篇 |
无线电 | 10篇 |
一般工业技术 | 8篇 |
冶金工业 | 693篇 |
原子能技术 | 5篇 |
自动化技术 | 6篇 |
出版年
2017年 | 1篇 |
2014年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2005年 | 1篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 17篇 |
1998年 | 201篇 |
1997年 | 96篇 |
1996年 | 70篇 |
1995年 | 38篇 |
1994年 | 45篇 |
1993年 | 34篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1977年 | 28篇 |
1976年 | 54篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1967年 | 2篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有741条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
W Weder R Thurnheer U Stammberger M Bürge EW Russi KE Bloch 《Canadian Metallurgical Quarterly》1997,64(2):313-9; discussion 319-20
BACKGROUND: Lung volume reduction surgery is known to alleviate dyspnea and to improve pulmonary function, performance in daily activity, and quality of life in selected patients with severe pulmonary emphysema. We investigated the role of radiologically assessed emphysema morphology on functional outcome after a lung volume reduction operation. METHODS: The preoperative chest computed tomograms in 50 consecutive patients who had undergone surgical lung volume reduction were retrospectively reviewed by 6 physicians blinded to the clinical outcome. Emphysema morphology was determined according to a simplified classification (ie, homogeneous, moderately heterogeneous, and markedly heterogeneous; lobe predominance). We studied the impact of these morphologic aspects on functional outcome at 3 months. RESULTS: We found a fair interobserver agreement applying our classification system. Functional improvement after surgical lung volume reduction was best in markedly heterogeneous emphysema with an increase in forced expiratory volume in 1 second of 81% +/- 17% (mean +/- standard error, n = 17) compared with 44% +/- 10% (n = 16) for intermediately heterogeneous emphysema. But also in patients with homogeneous emphysema clinical relevant improvement of function could be observed (increase in forced expiratory volume in 1 second = 34% +/- 6%; n = 17). CONCLUSIONS: The morphologic type of emphysema, assessed by a simplified surgically oriented classification, is an important predictor of surgical outcome. Lung volume reduction surgery may also improve dyspnea and lung function in homogeneous emphysema. 相似文献
105.
BACKGROUND: Because of the brevity of the postpartum hospital stay, mothers and their newborns are discharged home before breastfeeding is well established. In 1992, feedback from patients who had given birth at Fletcher Allen Health Care (Burlington, VT) suggested a need for more consistent, expert, and timely assistance with breastfeeding in the hospital and better continuity of care during the first few weeks at home. QUALITY IMPROVEMENT TEAM: In 1993 a team developed objectives, analyzed the problem and possible solutions, and made eight recommendations on how the hospital could do more to promote breastfeeding. Implementation by team members and hospital staff included policy development, staff education, acquisition of funding, a visiting professorship, development of a lactation consultant coordinator and team, and patient surveys to evaluate the program. A late 1994 survey of 63 postpartum patients on their day of discharge indicated a high level of satisfaction with breastfeeding support in the hospital. CURRENT STATUS: Activities are being undertaken for lactation consultation coverage, further policy development, implementation of nurse competency validation, improved patient and family education materials, and continued evaluation of the breastfeeding support program through patient surveys. CONCLUSION: In the face of barriers such as the project's large scope, a paucity of internal team members, and a large number and variety of recommendations, some of the recommendations and follow-up plans have yet to be implemented. Yet the project has yielded improvements in care and provides a model of how hospitals can expand their traditional boundaries of care and quality improvement into community health issues. 相似文献
106.
We have reported previously that serotonin (5-HT) stimulates the mitogenesis of bovine pulmonary artery smooth muscle cells (SMCs) through active transport of 5-HT and cellular signaling that includes elevation of superoxide (O2.-) and enhancement of protein tyrosine phosphorylation. Ginkgo biloba extract 501 (EGb 501), which has been demonstrated to act as an antioxidant, was found to block both the elevated O2.- and the proliferative and hypertrophic influences of 5-HT on SMCs, but not to directly inhibit the associated activation of NAD(P)H oxidase or the stimulation of phosphorylation of GTPase-activating protein (GAP). A similar effect of Ginkgo biloba extract 501 occurred on Chinese hamster lung fibroblasts (CCL-39), where 5-HT receptor, as opposed to transporter, action has been associated with mitogenesis. We conclude from these studies that Ginkgo biloba extract 501 quenches O2.- formation by 5-HT, thereby blocking its mitogenic effect. Stimulation of protein tyrosine phosphorylation of GAP by 5-HT appears to precede the elevation of O2.-. 相似文献
107.
EW Schmidt 《Canadian Metallurgical Quarterly》1998,51(1-2):6-10
The pharmacokinetics of fenoterol (salbutamol, terbutaline) after systemic administration (i.v., infusion, nasal administration) can be best described by a three-compartmental model. Nasal administration causes an effect-time profile between that of infusion and inhalation. The effects of nasal administration on the lung function and the heart rate depend on the plasma levels of the beta2-agonist. The absorption rate after inhalation differs individually in a large variability (1-27% of the dosage). After inhalation the effect on the lung function does not depend on the absorption rate nor on the plasma levels of the beta2-agonist. After inhalation the effect on the lung function is three- to fivefold more expressed than predictable from the plasma level. From the pk/pd data it can be assumed, that there are 10-20 fold higher concentrations in the airways than in the plasma. It is assumed that there are structures nearby the beta2-receptor responsible for the long-lasting effect observed after inhalation. These depot structures cannot be reached from the plasma in concentrations needed for bronchodilation under in vivo conditions. In respect to the effect/side effect relations, there is no doubt that inhalation is the optimal solution for administering beta2-agonists. In respect to the effect/side effect relations more frequent administration of small doses seems to be more favourable than high doses inhaled in long periods. 相似文献
108.
Programmed cell death, or apoptosis, is a process of fundamental importance to cellular homeostasis in metazoan organisms (Ellis, R. E., Yuan, J., and Horvitz, H. R. (1991) Annu. Rev. Cell Biol. 7, 663-698). The caspase family of mammalian proteases, related to the nematode death protein CED-3, plays a crucial role in apoptosis and inflammation. We report here the isolation and characterization of a new caspase, tentatively termed ERICE (Evolutionarily Related Interleukin-1beta Converting Enzyme). Based on phylogenetic analysis, ERICE (caspase-13) is a member of the ICE subfamily of caspases which includes caspase-1 (ICE), caspase-4 (ICErel-II, TX, ICH-2), and caspase-5 (ICErel-III, TY). Overexpression of ERICE induces apoptosis of 293 human embryonic kidney cells and MCF7 breast carcinoma cells. Like other members of the subfamily, ERICE is not activated by the serine protease granzyme B, a caspase-activating component of cytotoxic T cell granules. Therefore, ERICE most likely does not play a role in granzyme B-induced cell death. ERICE, however, was activated by caspase-8 (FLICE, MACH, Mch-5), the apical caspase activated upon engagement of death receptors belonging to the tumor necrosis factor family. This is consistent with a potential role for ERICE in this receptor-initiated death pathway. 相似文献
109.
FH Wolfhagen HJ van Hoogstraten HR van Buuren GP van Berge-Henegouwen FJ ten Kate WC Hop EW van der Hoek MJ Kerbert HH van Lijf JW den Ouden AM Smit RA de Vries RA van Zanten SW Schalm 《Canadian Metallurgical Quarterly》1998,29(5):736-742
BACKGROUND/AIMS: Treatment with ursodeoxycholic acid has been shown to decrease the rate of disease progression in patients with primary biliary cirrhosis, although the effect is modest. Since primary biliary cirrhosis has many features of an autoimmune disorder, immunosuppressives added to ursodeoxycholic acid may be of value in the treatment of primary biliary cirrhosis. METHODS: A 1-year randomized, double-blind, placebo-controlled trial was carried out in 50 patients with primary biliary cirrhosis, who had already been treated with ursodeoxycholic acid for at least 1 year, but had not achieved complete disease remission. Patients were randomized to additional prednisone (30 mg per day initially, tapered to 10 mg daily after 8 weeks) and azathioprine (50 mg daily) or placebo. A subgroup of patients received cyclical etidronate and calcium. The principal aim of the study was to assess the short-term benefits and risks of the combined bile acid and low-dose immunosuppressive regimen. Primary endpoints were effects on symptoms, liver biochemistry, liver histology, bone mass and the occurrence of adverse events. RESULTS: Pruritus (p=0.02), alkaline phosphatase, aspartate aminotransferase, IgM and procollagen-III-propeptide improved significantly (all p<0.002) in the combined treatment group as compared to the placebo group. Histological scores for disease activity and disease stage decreased significantly within the combination treatment group (p<0.001). CONCLUSIONS: In patients with primary biliary cirrhosis receiving ursodeoxycholic acid, there is an additional beneficial effect of 1-year treatment with prednisone and azathioprine on symptoms and biochemical, fibrogenetic and histological parameters. These results strongly encourage the evaluation of this triple treatment regimen in long-term controlled trials of adequate size to document its effect on clinical events. 相似文献
110.
HD Craig M Günel O Cepeda EW Johnson L Ptacek GK Steinberg CS Ogilvy MJ Berg SC Crawford RM Scott E Steichen-Gersdorf R Sabroe CT Kennedy G Mettler MJ Beis A Fryer IA Awad RP Lifton 《Canadian Metallurgical Quarterly》1998,7(12):1851-1858
Cerebral cavernous malformation (CCM) is a Mendelian model of stroke, characterized by focal abnormalities in small intracranial blood vessels leading to hemorrhage and consequent strokes and/or seizures. A significant fraction of cases is inherited as an autosomal dominant trait with incomplete penetrance. Among Hispanic Americans, virtually all CCM is attributable to a founder mutation localized to 7q ( CCM1 ). Recent analysis of non-Hispanic Caucasian kindreds, however, has excluded linkage to 7q in some, indicating at least one additional CCM locus. We now report analysis of linkage in 20 non-Hispanic Caucasian kindreds with familial CCM. In addition to linkage to CCM1, analysis of linkage demonstrates linkage to two new loci, CCM2 at 7p13-15 and CCM3 at 3q25.2-27. Multilocus analysis yields a maximum lod score of 14.11, with 40% of kindreds linked to CCM1, 20% linked to CCM2 and 40% linked to CCM3, with highly significant evidence for linkage to three loci (linkage to three loci supported with an odds ratio of 2.6 x 10(5):1 over linkage to two loci and 1.6 x 10(9):1 over linkage to one locus). Multipoint analysis among families with high posterior probabilities of linkage to each locus refines the locations of CCM2 and CCM3 to approximately 22 cM intervals. Linkage to these three loci can account for inheritance of CCM in all kindreds studied. Significant locus-specific differences in penetrance are identified. These findings have implications for genetic testing of this disorder and represent an important step toward identification of the molecular basis of this disease. 相似文献