全文获取类型
收费全文 | 1992篇 |
免费 | 54篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 50篇 |
综合类 | 38篇 |
化学工业 | 54篇 |
金属工艺 | 42篇 |
机械仪表 | 25篇 |
建筑科学 | 43篇 |
矿业工程 | 8篇 |
能源动力 | 6篇 |
轻工业 | 82篇 |
水利工程 | 25篇 |
石油天然气 | 10篇 |
武器工业 | 7篇 |
无线电 | 31篇 |
一般工业技术 | 58篇 |
冶金工业 | 1508篇 |
原子能技术 | 20篇 |
自动化技术 | 73篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 25篇 |
2011年 | 61篇 |
2010年 | 51篇 |
2009年 | 44篇 |
2008年 | 49篇 |
2007年 | 50篇 |
2006年 | 37篇 |
2005年 | 49篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 33篇 |
1998年 | 443篇 |
1997年 | 264篇 |
1996年 | 169篇 |
1995年 | 97篇 |
1994年 | 79篇 |
1993年 | 79篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1978年 | 3篇 |
1977年 | 58篇 |
1976年 | 115篇 |
1975年 | 2篇 |
1965年 | 2篇 |
1963年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有2080条查询结果,搜索用时 31 毫秒
151.
BA Loughner HA Gremillion PE Mahan RE Watson 《Canadian Metallurgical Quarterly》1997,55(4):363-9; discussion 369-70
PURPOSE: Attachments of the medial capsule of the temporomandibular joint (TMJ) to structures other than the medial fossa wall are thought to exist and to have functional significance. This study evaluated these relationships. MATERIALS AND METHODS: The anatomic relationships between the medial capsule and other medial structures, the sphenomandibular ligament, discomalleolar ligament, and auriculotemporal nerve, were examined in 14 cadaver heads. RESULTS: The results showed that the sphenomandibular ligament attaches separately from the medial capsule of the TMJ and therefore has no functional significance to the biomechanics of the joint. The discomalleolar ligament was found to be a continuation of the retrodiscal tissues and minimally associated with the medial capsule. The auriculotemporal nerve was not found to be in a relationship with the medial aspect of the condyle to the extent that mechanical irritation is possible during TMJ movement or disc displacement. 相似文献
152.
Arterial thrombi are primarily composed of platelets. Platelets are bound to injured endothelial cells, sub-endothelial matrices, and other platelets by a range of adhesive proteins. Some of these reactions are governed by shear forces. The role of adhesive proteins in the pathogenesis of arterial thrombosis is not fully understood. The aim of this study was to examine the involvement of von Willebrand factor (vWF), fibrinogen (Fg), and fibronectin (FN) in the formation of microvascular thrombi in vivo using a helium-neon laser-induced thrombosis method. Transmission electron microscopy demonstrated that laser irradiation resulted in platelet-rich thrombosis in arterioles and venules, and revealed that this occurred in the absence of endothelial denudation. The mean wall shear rates in mesenteric arterioles and venules were 641 +/- 40 and 280 +/- 20 s-1, respectively. Shear rates increased approximately fivefold in arterioles and tenfold in venules during the formation of occlusive thrombi. Antibody to vWF inhibited thrombosis in arterioles and venules. Antibodies to Fg and FN inhibited thrombosis in venules but not in arterioles. These results confirm that vWF, Fg and FN were involved in thrombogenesis in vivo and demonstrated that significantly higher shear rates were required for the reactions involving vWF than those involving either Fg or FN. 相似文献
153.
JE Hovens LM Vogtl?nder HA Verhoeve PL Thunnissen 《Canadian Metallurgical Quarterly》1994,138(7):363-365
A 38-year-old woman was treated for mutism with clozapine. After a week liver function disturbances developed, which disappeared when the treatment was discontinued. Histopathological investigation of a liver biopsy specimen revealed extensive liver cell necrosis. So far two patients have been described with cholestatic jaundice induced by clozapine, and one patient with toxic hepatitis due to clozapine. 相似文献
154.
155.
J Werwath HA Arfmann DH Pieper KN Timmis RM Wittich 《Canadian Metallurgical Quarterly》1998,180(16):4171-4176
A 4,103-bp long DNA fragment containing the structural gene of a gentisate 1,2-dioxygenase (EC 1.13.11.4), gtdA, from Sphingomonas sp. strain RW5 was cloned and sequenced. The gtdA gene encodes a 350-amino-acid polypeptide with a predicted size of 38.85 kDa. Comparison of the gtdA gene product with protein sequences in databases, including those of intradiol or extradiol ring-cleaving dioxygenases, revealed no significant homology except for a low similarity (27%) to the 1-hydroxy-2-naphthoate dioxygenase (phdI) of the phenanthrene degradation in Nocardioides sp. strain KP7 (T. Iwabuchi and S. Harayama, J. Bacteriol. 179:6488-6494, 1997). This gentisate 1,2-dioxygenase is thus a member of a new class of ring-cleaving dioxygenases. The gene was subcloned and hyperexpressed in E. coli. The resulting product was purified to homogeneity and partially characterized. Under denaturing conditions, the polypeptide exhibited an approximate size of 38.5 kDa and migrated on gel filtration as a species with a molecular mass of 177 kDa. The enzyme thus appears to be a homotetrameric protein. The purified enzyme stoichiometrically converted gentisate to maleylpyruvate, which was identified by gas chromatography-mass spectrometry analysis as its methyl ester. Values of affinity constants (Km) and specificity constants (Kcat/Km) of the enzyme were determined to be 15 microM and 511 s-1 M-1 x 10(4) for gentisate and 754 microM and 20 s-1 M-1 x 10(4) for 3, 6-dichlorogentisate. Three further open reading frames (ORFs) were found downstream of gtdA. The deduced amino acid sequence of ORF 2 showed homology to several isomerases and carboxylases, and those of ORFs 3 and 4 exhibited significant homology to enzymes of the glutathione isomerase superfamily and glutathione reductase superfamily, respectively. 相似文献
156.
The spontaneous growth of 315 patients (109 girls and 208 boys) with Prader-Willi syndrome (PWS) was analysed in a mixed longitudinal and cross-sectional manner. 33 patients were seen in the department between 1970 and 1994; height and weight of 76 patients from Germany were evaluated by means of a questionnaire with detailed measuring instructions, and 206 definite cases were added from the literature. Mean ( SD) length of newborn babies with PWS was 50.2+/-2.8 cm (145 boys) and 48.9 3.3 cm (79 girls). Mean weight at birth was 2945 570 g in boys and 2782+/-594 g in girls. During the 1st year, the children's growth was nearly normal, thereafter short stature was present in approximately 50% of PWS patients. Between 3 and 13 years of age, the 50th percentile for height in PWS is roughly identical with the 3rd percentile in healthy controls. Body weight was normal for all boys and girls during the first 2 years. Thereafter, a rapid weight gain occurred; after an age of 10 years weight-for-height index in nearly all patients exceeded the normal range. The extent of pubertal growth was reduced for the group. Mean adult height was 161.6+/-8.1 cm (23 males) and 150.2+/-5.5 cm (21 females). Head circumference for age was normal for boys and girls. CONCLUSION: Reference data on spontaneous development of growth and weight gain of children with Prader-Willi syndrome are described allowing a better counselling of patients and parents. 相似文献
157.
HA Scheraga 《Canadian Metallurgical Quarterly》1998,16(2):447-460
An earlier theoretical approach to the hydrophobic interaction, based on statistical mechanical treatments of models for liquid water and for aqueous solutions of hydrocarbons, is summarized here. Experimental verification of the theoretical thermodynamic parameters for hydrophobic interactions, and applications of the theory to some aspects of protein structure, are presented. 相似文献
158.
Methane output and lactation response in Holstein cattle with monensin or unsaturated fat added to the diet 总被引:1,自引:0,他引:1
FD Sauer V Fellner R Kinsman JK Kramer HA Jackson AJ Lee S Chen 《Canadian Metallurgical Quarterly》1998,76(3):906-914
We measured effects of continuous vs twice-daily feeding, the addition of unsaturated fat to the diet, and monensin on milk production, milk composition, feed intake, and CO2-methane production in four experiments in a herd of 88 to 109 milking Holsteins. Methane and CO2 production increased with twice-daily feeding, but the CO2:CH4 ratio remained unchanged. Soybean oil did not affect the milkfat percentages, but fatty acid composition was changed. All saturated fatty acids up to and including 16:0 decreased (P < .01), whereas 18:0 and trans 18:1 increased (P < .001). The 18:2 conjugated dienes also increased (P < .01) when the cows were fed soybean oil. Monensin addition to the diet at 24 ppm decreased methane production (P < .01); the CO2:CH4 ratios reached 15, milk production increased (P < .01), and milkfat percentage and total milkfat output decreased (P < .01), as did feed consumption, compared with cows fed diets without monensin (P < .05). Milk fatty acid composition showed evidence of depressed ruminal biohydrogenation: saturated fatty acids (P < .05) decreased and 18:1 increased (P < .001); most of the increase was seen in the trans 18:1 isomer. As with soybean oil feeding, addition of monensin also increased (P < .05) the concentration of conjugated dienes. The monensin feeding trial was repeated 161 d later with 88 cows, of which 67 received monensin in the diet in the first trial and 21 cows were newly freshened and had never received monensin. Methane production again decreased (P < .05), but this time the CO2:CH4 ratio did not change and all other monensin-related effects were absent. The ruminal microflora in the cows that had previously received monensin seemed to have undergone some adaptive changes and no longer responded as before. 相似文献
159.
160.
A Younes J Romaguera O Mesina F Hagemeister AH Sarris MA Rodriguez P McLaughlin HA Preti C Bachier F Cabanillas 《Canadian Metallurgical Quarterly》1998,103(3):678-683
Based on the single-agent activity of both paclitaxel and cyclophosphamide in the treatment of non-Hodgkin's lymphoma (NHL), we conducted a phase II study to evaluate the efficacy of the combination of the two drugs in patients with refractory and relapsed aggressive NHL. All patients received 900 mg/m2 bolus of cyclophosphamide intravenously daily for 3 consecutive days with a concurrent infusion of 150 mg/m2 of paclitaxel over 72 h (50 mg/m2/d). 24 h after the completion of chemotherapy, patients received subcutaneous injections of 5 microg/kg of granulocyte-colony stimulating factor (G-CSF) daily until white cell count recovery. Treatment was repeated every 3 weeks. Patients who had at least a partial response (PR) after two courses continued to receive a maximum of four courses. Patients with responding disease were allowed to undergo high-dose chemotherapy followed by stem-cell/bone marrow transplantation if they were eligible. Of the 77 patients who were eligible for the study, 74 (96%) were evaluable for toxicity and treatment response. The overall response rate was 45% (95% CI 33-57%). Patients who received treatment after their disease relapsed from a complete response (CR) had an 81% response rate (38% CRs), whereas those with primary refractory disease had a 22% response rate. Toxicities of > grade 2 included alopecia (100%) and stomatitis (25%). Neutropenic fever of grade > 2 occurred after 18% of the courses, and platelet count of < or = 20 x 10(9)/l developed after 20% of the courses. Thus, the combination of paclitaxel plus high-dose cyclophosphamide is an effective new regimen in the treatment of refractory and relapsed NHL. 相似文献