全文获取类型
收费全文 | 2192篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 31篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 3篇 |
轻工业 | 12篇 |
水利工程 | 13篇 |
石油天然气 | 6篇 |
无线电 | 19篇 |
一般工业技术 | 76篇 |
冶金工业 | 1987篇 |
原子能技术 | 1篇 |
自动化技术 | 25篇 |
出版年
2020年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 6篇 |
2011年 | 8篇 |
2010年 | 15篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 18篇 |
2002年 | 7篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 62篇 |
1998年 | 686篇 |
1997年 | 315篇 |
1996年 | 237篇 |
1995年 | 116篇 |
1994年 | 101篇 |
1993年 | 126篇 |
1992年 | 14篇 |
1991年 | 28篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 37篇 |
1987年 | 31篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1978年 | 3篇 |
1977年 | 27篇 |
1976年 | 106篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1962年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2213条查询结果,搜索用时 15 毫秒
51.
SH Thomas JE Horner K Chew J Connolly B Dorani L Bevan S Bhattacharyya MG Bramble KH Han A Rodgers B Sen B Tesfayohannes H Wynne DN Bateman 《Canadian Metallurgical Quarterly》1997,16(9):495-500
1. Paracetamol is increasingly involved in self-poisoning in the United Kingdom and remains a common cause of fatal poisoning. 2. To document the epidemiology and early management of paracetamol poisoning data were collected on consecutive patients with suspected paracetamol poisoning presenting to 6 hospitals in the North East of England over 12 weeks in 1994. 3. There were 400 presentations (attendance rate 1.14/10(3) population/yr) involving 343 persons (45% male). Paracetamol concentrations at 4 h correlated weakly with reported paracetamol dose (R = 0.49, P < 0.0001) and were similar comparing those treated and not treated by gastric decontamination. 4. In 38 (9%) cases paracetamol concentrations were above the appropriate nomogram treatment line, including 3% and 20% of patients who reported ingesting less than and more than 12 g respectively. In 21 patients acetylcysteine treatment was deferred until admission to the ward, the mean delay involved was 2.8 h. 5. One patient died, from arrhythmias caused by co-ingested dothiepin. 6. Paracetamol poisoning is common. Most cases do not have potentially toxic plasma paracetamol concentrations, but those who do often present late and antidotal treatment may be delayed inappropriately. 相似文献
52.
SH Lisanby DP Devanand MS Nobler J Prudic L Mullen HA Sackeim 《Canadian Metallurgical Quarterly》1996,12(3):156-164
Numerous studies have confirmed the distinct biological behavior of two subsets of prostate cancer diagnosed incidentally after either transurethral resection (TURP) or open prostatectomy for presumed benign prostatic hyperplasia (BPH). Focal, low-grade lesions are associated with a low risk for clinical progression and are designated as stage T1a or A1. These cases have traditionally been managed conservatively with close clinical observation. In contrast, multifocal, high-volume, or high-grade tumors are associated with a more aggressive clinical course and are designated as stage T1b or A2. Early definitive intervention is usually advocated for these latter patients. Therefore, accurate pathological assignment to either stage T1a or T1b is crucial for selection of appropriate management options. A variety of methods for staging patients with incidentally detected prostate cancer have been proposed, including detailed histological analysis, repeat TURP or transurethral biopsy, serial prostate-specific antigen (PSA) analysis, and imaging with either transrectal ultrasound (TRUS) or magnetic resonance (MRI) techniques. This article critically examines the clinical utility of these staging modalities for patients with incidentally detected prostate cancer. 相似文献
53.
Despite the introduction in recent years of novel antifungal agents, the potency and broad spectrum of activity of amphotericin B have ensured that it remains the treatment of choice for most deep-seated mycoses. However, this agent is not without significant toxicity, particularly in patients who are already seriously ill and/or who are receiving other potentially nephrotoxic drugs. We review the various routes by which amphotericin B can be administered, focusing mainly on the intravenous route. The use of more rapid infusion rates, lipid-complexed preparations, sodium supplementation in salt-depleted patients and strategies to reduce the incidence of infusion-related reactions and nephrotoxicity are also considered. Finally, detailed recommendations for the administration of amphotericin B are provided. 相似文献
54.
The uptake of Listeria monocytogenes by a variety of cell types in vitro is facilitated by the protein products of the inlAB (internalin) operon expressed by the organism. In the case of mouse hepatocytes, the extent to which inlAB expression influenced the uptake of Listeria in vitro was markedly dependent upon the ratio of bacteria to cells. At a ratio of 100:1, greater than 40-fold fewer transposon-induced inl4B mutant listeriae entered hepatocytes compared to the isogenic wild-type control; the difference was only fourfold, however, in cultures inoculated at a 1:1 ratio. Similarly, the uptake of in-frame inlB or inlAB deletion mutants differed only fourfold from the uptake of wild-type or inlA mutant Listeria at a 1:1 multiplicity of infection. Mutations affecting inlB or inlAB, on the other hand, resulted in a marked decrease in the capacity of Listeria to proliferate within mouse hepatocytes in vivo and in vitro. Electron micrographs of Listeria-infected hepatocytes demonstrated the impaired capacity of inlB mutants to escape from endocytic vacuoles and to enter the cytoplasm where proliferation occurs. These findings indicate that the protein product of inlB exerts a significant effect on the intracellular replication of Listeria. 相似文献
55.
56.
57.
CM Lucas ED Franke MI Cachay A Tejada ME Cruz RD Kreutzer DC Barker SH McCann DM Watts 《Canadian Metallurgical Quarterly》1998,59(2):312-317
Asymmetric acetylcholinesterase (AChE) is anchored to the basal lamina (BL) of cholinergic synapses via its collagenic tail, yet the complement of matrix receptors involved in its attachment remains unknown. The development of a novel overlay technique has allowed us to identify two Torpedo BL components that bind asymmetric AChE: a polypeptide of approximately 140 kDa and a doublet of 195-215 kDa. These were found to stain metachromatically with Coomassie blue R-250, were solubilized by acetic acid, and were sensitive to collagenase treatment. Upon sequence analysis, the 140 kDa polypeptide yielded a characteristic collagenous motif. Another AChE-binding BL constituent, identified by overlay, corresponded to a heparan sulfate proteoglycan. Lastly, we established that this proteoglycan, but not the collagenous proteins, interacted with at least one heparin binding domain of the collagenic tail of AChE. Our results indicate that at least two BL receptors are likely to exist for asymmetric AChE in Torpedo electric organ. 相似文献
58.
SH Roth 《Canadian Metallurgical Quarterly》1998,25(7):1358-1363
OBJECTIVE: To evaluate the efficacy of tramadol as adjunctive therapy in patients with musculoskeletal pain attributed to osteoarthritis (OA) who experienced breakthrough pain while taking a nonsteroidal antiinflammatory drug (NSAID). METHODS: This single center, parallel, placebo controlled, 2 phase study was conducted in adults who experienced breakthrough OA pain while undergoing stable NSAID therapy. In a 24 h open label phase, patients took 100 mg of tramadol followed by 50 mg every 6 h (total 250 mg) in addition to their daily NSAID regimen. Supplemental analgesics were prohibited. Patients who met entry criteria and were willing to continue therapy were randomized to a 13 day double blind phase of adjunctive therapy with tramadol (50-100 mg every 4-6 h as needed for pain) or placebo; NSAID therapy was continued. The primary efficacy endpoint was the time to exit from the study because of therapeutic failure (i.e., insufficient pain relief or an inability to perform activities of daily living). RESULTS: The time to exit from the study because of insufficient pain relief tended to be longer in the tramadol group (250 mg/day) compared with the placebo group (p = 0.066). At the end of the double blind phase, pain at rest was significantly less severe in tramadol treated patients (p = 0.046). In addition, severity of pain on motion tended to be less severe in tramadol treated patients (p = 0.059). General severity of current pain and ability to perform activities of daily living were not significantly different with tramadol or placebo. Patients' overall assessment of therapy (p = 0.022) and investigator's rating of global improvement (p = 0.004) were significantly better with tramadol than with placebo. CONCLUSION: Tramadol may have a role as adjunctive treatment for breakthrough pain in patients receiving NSAID therapy for musculoskeletal pain attributed to OA. 相似文献
59.
The development and maturation of the endolymphatic sac (ES) and duct (ED) were studied in the newt Cynops pyrrhogaster. The ES first appears as an oval capsule at the dorsal-medial tip of the otic vesicle at stage 39, about 11 days after oviposition. The ES consists of polymorphous epithelial cells with a minimum of cytoplasm. The intercellular space (IS) between the epithelial cells is narrow and has a smooth surface. At stage 44, the size of the ES increases as many vacuoles in the IS become filled. At stage 46, 18 days after oviposition, the ES elongates markedly and a slit-like lumen is found in the ES. The epithelium contains a few cell organelles which are scattered in the cytoplasm. The vacuoles in the IS are fused, which expands the IS. Two days later (stage 48), floccular material (endolymph) is present in the expanded lumen. The IS dilates and has a wide and irregular appearance. At stage 50, approximately 26 days after oviposition, the ES extends and expands significantly and crystals (otoconia) can now be seen in the widened lumen of the ES. The cytoplasm of the cuboidal epithelial cells contains an abundance of vesicles surrounded by ribosomes and Golgi complexes. Intercellular digitations are formed in the expanded IS. At stage 54, the ES forms a large bellow-like pouch. Numerous otoconia accumulate in the lumen. Free floating cells and cell debris can be seen in the lumen at this stage. The epithelial cells contain numerous cytoplasmic organelles which are evenly distributed in the cytoplasm. Granules are found in the apical and lateral cytoplasm. The IS is loose and displays a labyrinthine appearance. The primitive ED first appears as a connection between the ES and the saccule but no lumen is present inside at stage 39. At stage 46, a narrow lumen is formed in the ED, which corresponds to the formation of the ES lumen. At stage 50, as the ED extends, floccular material is seen in the lumen. At stage 54, the ED bears numerous microvilli on its luminal surface. Otoconia and endolymph are present in the ED. Tight junctions between the epithelial cells are formed at stage 46. A fully developed intercellular junctional complex is produced at stage 54. Based on the development of the ES and ED, the maturation of function of the ES and ED are discussed. 相似文献
60.
We undertook the following study to quantitatively assess the changes in porcine bioprosthetic heart valve (PBHV) fiber architecture to increasing levels of fatigue damage using an in vitro accelerated test model. PBHVs were subjected to 0-500 million test cycles at 16 Hz, and small-angle light scattering (SALS) was used to quantify the gross fiber structure of the cusps. The degree of gross fiber alignment remained essentially constant from 0 to 500 million cycles over the entire cusp. Increasing fiber orientation randomness, indicative of local damage, was observed only in the vicinity of the nodulus of Arantii after 50 million cycles. The SALS data from the damaged regions suggested shearing between fiber layers, which may be part of the failure process and accelerates valve failure. Histological analysis revealed a relatively intact gross fiber structure with the collagen fiber crimp remaining, although delamination and de-registration of the crimp was also observed. Accelerated tested PBHVs also demonstrated a pronounced 'sagging', which began at the earliest cycle number tested (1.4 million cycles) and whose rate decreased logarithmically with cycle number. Results of this study suggest that PBHV cusps can alter their shape without any visually apparent material yielding or fiber failure under continual cyclic loading. Further, while most of the 4 mmHg pressure fixed PBHV's gross fiber architecture remains unchanged after 500 million cycles of accelerated testing, localized accumulated fiber damage can occur on a sub-visual structural level as early as 50 million cycles. 相似文献