全文获取类型
收费全文 | 1459篇 |
免费 | 21篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 76篇 |
金属工艺 | 2篇 |
机械仪表 | 9篇 |
建筑科学 | 11篇 |
能源动力 | 10篇 |
轻工业 | 16篇 |
水利工程 | 6篇 |
无线电 | 11篇 |
一般工业技术 | 27篇 |
冶金工业 | 1258篇 |
原子能技术 | 1篇 |
自动化技术 | 49篇 |
出版年
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 18篇 |
2012年 | 9篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 12篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 40篇 |
1998年 | 358篇 |
1997年 | 193篇 |
1996年 | 139篇 |
1995年 | 69篇 |
1994年 | 82篇 |
1993年 | 78篇 |
1992年 | 17篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 25篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 27篇 |
1976年 | 89篇 |
1975年 | 6篇 |
1971年 | 2篇 |
1966年 | 2篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有1480条查询结果,搜索用时 15 毫秒
991.
JW Kim HR McDonald PE Rubsamen JK Luttrull JH Drouilhet DA Frambach DS Boyer FH Lambrou A Hendrick JN Weiss RE Engstrom M Ing 《Canadian Metallurgical Quarterly》1998,18(5):424-429
Tropomyosins (Tm) are a large family of isoforms obtained from multiple genes and by extensive alternative splicing. They bind in the alpha-helical groove of the actin filament and are therefore core components of this extensive cytoskeletal system. In non-muscle cells the Tm isoforms have been implicated in a diversity of processes including cytokinesis, vesicle transport, motility, morphogenesis and cell transformation. Using immunohistochemical localization in cultured primary cortical neurons with an antibody that potentially identifies all non-muscle TM5 gene isoforms compared with one that specifically identifies a subset of isoforms, the possibility was raised that there were considerably more isoforms derived from this gene than the four previously described. Using polymerase chain reaction (PCR) analysis we have now shown that the rat brain generates at least 10 mRNA isoforms using multiple combinations of terminal exons and two internal exons. There is extensive developmental regulation of these isoforms in the brain and there appears to be a switch in the preferential use of the two internal exons 6a to 6b from the embryonic to the adult isoforms. Specific isoforms using alternate carboxyl-terminal exons are differentially localized within the adult rat cerebellum. It is suggested that the tightly regulated spatial and temporal expression of Tm isoforms plays an important role in the development and maintenance of specific neuronal compartments. This may be achieved by isoforms providing unique structural properties to actin-based filaments within functionally distinct neuronal domains. 相似文献
992.
HR Montz 《Canadian Metallurgical Quarterly》1997,114(2):479-88; discussion 488-9
993.
JL Isaacsohn M Moser EA Stein K Dudley JA Davey E Liskov HR Black 《Canadian Metallurgical Quarterly》1998,158(11):1189-1194
BACKGROUND: Some wrinkles and unsightly facial expressions are due to overactivity of the underlying facial musculature. Botulinum A exotoxin reversably paralyses selected muscles. Botulinum toxin has been used to correct facial cosmetic concerns. OBJECTIVES: This paper describes the authors' experience with the cosmetic use of botulinum toxin. The areas that can be treated, the appropriate technique for each area and special considerations such as dose, dilution, and relevant anatomy are discussed. RESULTS: Our results have been published previously and are referenced in this paper. CONCLUSIONS: Botulinum toxin is safe and effective in the management of some facial lines and wrinkles. Its use is associated with a high degree of patient and physician satisfaction. 相似文献
994.
In papillary thyroid carcinoma lymphnode metastases at presentation do not seem to adversely affect survival, but do increase the risk of loco-regional tumor recurrence. The value of systematic versus selective lymphadenectomy is far less standardized, whereas the role of postoperative radioiodine in preventing either nodal recurrence or cancer death remains controversial. Clinical data of 36 N+ patients with papillary thyroid carcinoma who had undergone from 1990 to 1996 ipsilateral or bilateral neck dissection were retrospectively reviewed, to analyse the value of systematic lymphadenectomy. In our series of 50 extensive lymph node dissections (levels 2-6), the number of metastases in each specimen (mean value: 5) and the incidence of multiple level metastases (36%) were high. In 37.5% of the metastases at level 6 and in 11.1% at level 4, coexisting nodal involvement at level 2 was observed, without metastasization at intermediate levels. Multiple levels metastases and skip metastases were present in at least one third of the patients and could be excised only performing a complete dissection of the levels 2-6. Extra-capsular spread was found in 56% of the specimens. In 64.3% of these cases a functional neck dissection was performed. A modified radical or radical neck dissection was carried out in the other 35.7% of the cases. These patients received modified radical neck dissection (functional dissection with sacrifice of internal jugular vein) in 60% of the cases and radical neck dissection in the other 40%. In papillary thyroid carcinoma extensive lymphnode dissection at presentation has been stated to offer no advantage versus selective lymphadenectomy, causing increased morbidity. However, experienced surgeons report a low incidence (less than 5%) of accessory spinal nerve and cervical plexus permanent sequelae after functional neck dissection. In our opinion, patients with cervical lymph node metastases require a complete loco-regional neck dissection. Systematic lymphadenectomy, performed by lateral neck plus upper anterior mediastinal dissection, can yield a high disease-free survival. Moreover, this can limit the overall radio-iodine therapeutic dose and the risk of de-differentiation of recurrent tumor to the anaplastic type in patients with a long-term and near normal life-span. 相似文献
995.
M Wasa BP Bode SF Abcouwer CL Collins KK Tanabe WW Souba 《Canadian Metallurgical Quarterly》1996,224(2):189-197
BACKGROUND: Hip fracture is a preventable cause of disability among elderly people AIM: To study factors associated to hip fractures in Chile. PATIENTS AND METHODS: Patients admitted to seven public hospitals in Chile, with hip fracture not due to major accidents, were considered as cases. To each, at least one age and sex matched hospitalized control, without or neoplastic diseases, was assigned. All patients were subjected to an inquiry, using an instrument devised by the WHO. RESULTS: Two hundred sixty eight cases and 501 controls were studied. Cases and controls has similar educational and labor histories. The right hip was fractures in 47% of cases and the left in the rest. Compared with controls, cases had a higher body mass index, loss of height during life, rate of hysterectomy, incidence of smoking and a lower consumption of diary products. Cases had higher risk of falls inside their homes and controls outside. CONCLUSIONS: The obtained information may contribute to the development of preventive measures and reduce the public health impact of hip fracture. 相似文献
996.
Ecstasy (3,4-methylenedioxymethamphetamine or MDMA) is used with increasing frequency as a recreational drug. Accumulated evidence over recent years indicates a growing demand for the drug with a corresponding increase in number of reports of adverse effects from its use. There are reported metabolic disturbances due to MDMA use. These, in addition to the prolonged exercise involved in dancing at 'raves' where MDMA may be used, may exacerbate ketoacidosis. We report two cases of ketoacidosis complicated by MDMA ingestion. 相似文献
997.
L Thuesen K Rasmussen HR Andersen TV Nielsen AB Villadsen HH Hansen AP Schroeder SE Husted TT Nielsen 《Canadian Metallurgical Quarterly》1998,160(37):5344-5348
In the present study we compared the outcome of primary percutaneous coronary angioplasty (PTCA) (PTCA without prior or concomitant administration of thrombolytic drugs) in 82 consecutive patients with acute myocardial infarction (AMI) with the outcome of 82 AMI patients, who were treated with intravenous thrombolysis. The thrombolysis patients were prospectively matched to the angioplasty patients regarding age, sex, duration of symptoms and infarct localisation. The in-hospital mortality was 3.7% in the PTCA group versus 4.9% in the thrombolysis group. Thrombolysis-treated patients had increased use of diuretics and ACE-inhibitors as compared to PTCA-treated patients. The mean ejection fraction was 52 +/- 11% in the PTCA group versus 47 +/- 10% (p = 0.01) in the thrombolysis group. We conclude that initial Danish experience with primary PTCA is promising, and that this treatment may favourably affect the outcome of acute myocardial infarction. 相似文献
998.
999.
1000.
The N-terminal six transmenbrane helices (N6) and the C-terminal six transmembrane helices (C6) of lactose permease, each with a single Cys residue, were co-expressed, and cross-linking was studied. The proximity of paired Cys residues in helices I (positions 11, 14, 15, 18, 25, 28, 29, or 32) and VII (positions 227, 231, 232, 234, 235, 238, 239, 241, 242, 245, or 246) was studied by using homobifunctional thiol-specific chemical linkers of different lengths and chemical properties. The results demonstrate that Cys residues on one face of the periplasmic half of helix I (positions 32, 29, 28, or 25) cross-link to Cys residues on one face of the periplasmic half of helix VII (242 or 245). In contrast, no cross-linking is evident with paired Cys residues in the cytoplasmic halves of helices I (positions 11, 14, 15, or 18) and VII (positions 227, 230, 231, 232, 234, 235, 238, or 239). The results indicate that helices I and VII are in close proximity only at their periplasmic halves. Ligand binding decreases cross-linking efficiency of the Cys pair 28/245 or 25/242 with N, N'-o-phenylenedimaleimide (rigid 6 A) and increases efficiency with N,N'-p-phenylenedimaleimide (rigid 10 A) or 1,6-bismaleimidohexane (flexible 16 A), indicating that the inter-thiol distance is about 6 A in the absence of ligand and that ligand binding increases the distance up to 10 A. The inter-thiol distance for Cys pairs 29/245 or 32/245 is less than 6 A in the absence of ligand, and in the presence of ligand, distance increases to between 6 and 10 A. Taken together, the results indicate that ligand binding induces a translational or scissors-like rigid body movement of helix I and/or VII at the periplasmic interface between the helices. 相似文献