全文获取类型
收费全文 | 3338篇 |
免费 | 13篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 17篇 |
综合类 | 12篇 |
化学工业 | 61篇 |
金属工艺 | 29篇 |
机械仪表 | 15篇 |
建筑科学 | 14篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 74篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
无线电 | 13篇 |
一般工业技术 | 65篇 |
冶金工业 | 2995篇 |
原子能技术 | 8篇 |
自动化技术 | 40篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2017年 | 4篇 |
2015年 | 11篇 |
2014年 | 7篇 |
2013年 | 49篇 |
2012年 | 27篇 |
2011年 | 20篇 |
2010年 | 16篇 |
2009年 | 24篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 14篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 100篇 |
1998年 | 930篇 |
1997年 | 563篇 |
1996年 | 352篇 |
1995年 | 171篇 |
1994年 | 147篇 |
1993年 | 208篇 |
1992年 | 26篇 |
1991年 | 13篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 29篇 |
1978年 | 13篇 |
1977年 | 95篇 |
1976年 | 210篇 |
1975年 | 7篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1965年 | 4篇 |
1962年 | 5篇 |
1961年 | 3篇 |
1960年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有3364条查询结果,搜索用时 15 毫秒
111.
KL Hammond IM Hanson AG Brown LA Lettice RE Hill 《Canadian Metallurgical Quarterly》1998,74(1-2):121-131
The human myeloid leukemias are a diverse group of disorders characterized by massive clonal expansion of myeloid cells showing variable degrees of differentiation block. Leukemic dendritic cells were generated in culture from chronic myelogenous leukemia (CML). These were used to stimulate autologous T cells to develop leukemia-specific cytotoxicity. Available data suggest that the cells responsible for the cytolytic activity are at least in part CD8+ and HLA restricted in their function. Additional data suggest that some anti-CML cellular activity may be Fas mediated. T-cell receptor studies provide evidence for an oligoclonal response implying a recognition of a limited number of antigens. We have used culture techniques similar to those used for CML to study the ability of AML cells to differentiate toward dendritic cells. Four of five patients have shown acute leukemia-derived dendritic cells. This work offers an avenue for the development of novel strategies for the control of human myeloid leukemias. 相似文献
112.
A male, wild-caught kangaroo rat developed anorexia and wasting. The animal was euthanized and a gastric trichobezoar found at necropsy. The paucity of information regarding the clinical medicine of this species is a hindrance to those charged with the care of kangaroo rats. Gastric trichobezoar should be considered as a differential diagnosis in cases of anorexia in kangaroo rats. 相似文献
113.
BACKGROUND: Whether intraoperative laparoscopic cholangiography should be routine is debatable. METHODS: We reviewed the cholangiography experience in 669 consecutive laparoscopic cholecystectomies. RESULTS: Mean age of the patients was 39 years, 78% were female, and 29% had acute cholecystitis. Cholecystectomy was completed laparoscopically in 606 (91%). Laparoscopic cholangiography was completed in 562 (93%) and 348 (62%) were routine (no preoperative indication). The mean operating time in 1996 was 61 minutes. Out of the 348 routine cholangiograms, 17 demonstrated evidence of unsuspected choledocholithiasis. Five patients had choledocholithiasis documented by laparoscopic common bile duct exploration and/or endoscopic retrograde cholangiopancreatography. Two patients had normal postoperative cholangiopancreatography. One of 10 patients managed expectantly was readmitted postoperatively with obstructive jaundice. In 4 patients, routine cholangiography revealed unexpected anatomy, and in 2, this prevented misidentification and transection of the common bile duct. CONCLUSION: Laparoscopic cholangiography is safe, quick, detects unsuspected choledocholithiasis, and can prevent common bile duct transection. It should be routine. 相似文献
114.
115.
CA Porr DS Kronfeld LA Lawrence RS Pleasant PA Harris 《Canadian Metallurgical Quarterly》1998,76(7):1875-1879
Diet and exercise are two management factors that affect bone density and strength. We proposed that bone density and calcium status would be affected by deconditioning for 12 wk and by dietary Ca concentration. Eleven highly conditioned Arabian horses were taken out of training and placed in stalls for 12 wk. Horses were walked on a mechanical walker in two 30-min sessions, 7 d/wk. Diets were designated CC (.36% Ca) and HC (.62% Ca). Data were collected every 21 d. Serum or plasma were analyzed for total and ionized Ca, parathyroid hormone, osteocalcin, hydroxyproline, electrolytes, and blood gases. Bone mineral content (BMC) of the left third metacarpal bone was estimated by radiographic photometry using an aluminum step wedge, which was exposed in each radiograph, as a reference standard for an image analysis system. During deconditioning, BMC decreased by approximately 1.1 g/2 cm, or .45% per week. This decrease was unaffected by dietary Ca. Serum Ca concentration increased with deconditioning. The results suggest that dietary Ca at twice the currently recommended level did not prevent the loss of BMC in response to deconditioning. Loss of BMC during 12 wk of stall confinement may weaken bones, increasing the risk of skeletal injuries when training is resumed. 相似文献
116.
AJ Murray J Cavalieri MJ D'Occhio TR Whyte LJ Maclellan LA Fitzpatrick 《Canadian Metallurgical Quarterly》1998,50(1-2):11-26
The aim of this study was to determine the effect on ovarian follicular growth and atresia, of acute treatment with either 100 mg of progesterone (n = 10), 200 mg of progesterone (n = 10), 10 mg of oestradiol + 100 mg of progesterone (n = 10), 10 mg of oestradiol (n = 10) or no treatment (n = 10), given on Day 10 of a 17-day treatment with a norgestomet implant in randomly cycling Bos indicus heifers. The fate of the dominant follicle on Day 10, emergence of the new cohort of follicles and the intervals from implant removal to ovulation were recorded by ultrasonography. Plasma concentrations of Luteinizing hormone (LH), progesterone and oestradiol were determined during the time when the norgestomet implant was in place. All treatments resulted in the emergence of a new cohort of follicles within 5 days of administration. The day of emergence of the ovulatory follicle tended to be delayed after treatment with 100 mg of progesterone (2.7 +/- 0.3 days after treatment), 200 mg of progesterone (3.7 +/- 0.5 days after treatment), 10 mg of oestradiol + 100 mg of progesterone (4.4 +/- 0.2 days after treatment) and 10 mg of oestradiol (4.6 +/- 0.4 days after treatment) compared to control heifers (1.4 +/- 1.4 days after time of treatment). The mean interval from implant removal to onset of oestrus was significantly shorter after treatment with 100 mg of progesterone (38.4 +/- 2.6 h) than after treatment with 200 mg of progesterone (61.5 +/- 3.9 h) but otherwise, the mean interval from implant removal to onset of oestrus did not differ. Oestrus synchrony, measured by the sample standard deviation of oestrus onset, was tighter in all treatment groups compared to untreated control heifers. The mean interval from implant removal to ovulation did not differ significantly between groups. The synchrony of ovulation, measured by the sample standard deviation of the interval from implant removal to ovulation, was significantly tighter after treatment with 100 mg of progesterone, 200 mg of progesterone and 10 mg of oestradiol compared to control heifers. Treatment with 10 mg of oestradiol resulted in ovulation in seven of 10 heifers before implant removal, three of which failed to ovulate after implant removal. Progesterone administered on Day 10 lowered plasma LH concentrations (P < 0.05), whereas treatment with oestradiol caused a surge of LH and ovulation. Progesterone administered with oestradiol prevented the LH surge. A combination treatment of oestradiol and progesterone given on Day 10 of a 17-day norgestomet treatment in a range of follicular states resulted in the consistent emergence of a new cohort of follicles which included the eventual ovulatory follicle. 相似文献
117.
RA Nugent M Murphy ST Schlachter CJ Dunn RJ Smith ND Staite LA Galinet SK Shields DG Aspar KA Richard 《Canadian Metallurgical Quarterly》1993,36(1):134-139
Vinylidenebisphosphonic acid tetraethyl ester (1) and diazo ketones 7a-1 in ether at 22 degrees C yield pyrazoline bisphosphonate tetraethyl esters 8a-1 in moderate to good yield. These compounds were evaluated in animal models of arthritis: rat adjuvant-induced polyarthritis (AIP) and murine antigen-induced arthritis (AIA) and a murine model of chronic inflammation, the delayed type hypersensitivity granuloma reaction (DTH-GRA). (5-Benzoyl-2,4-dihydro-3H-pyrazol-3-ylidene)-bisphosphonic acid tetraethyl ester (8a), and [5-(3-fluorobenzoyl)-2,4-dihydro-3H-pyraxol-3-ylidene]- bisphosphonic acid tetraethyl ester (8d) significantly inhibited the arthritis models, AIP (15 mg/kg) and AIA (25 mg/kg), as well as the DTH-GRA (25 mg/kg). Conversion of 8a to the corresponding bisphosphonic acid, 10a, resulted in loss of activity. Compounds with alkyl substituents on the pyrazoline nitrogen, 9a-d, were inactive in the DTH-GRA. These results show that 8a and 8d have novel antiinflammatory activity and are capable of inhibiting chronic arthritis and inflammation in animals. Such compounds might be useful in man for treating chronic tissue injury associated with arthropathies such as inflammatory joint disease as well as other chronic inflammatory diseases. 相似文献
118.
GIu Sharaevski? LA Tiunov VV Chumakov VS Sukhorukov 《Canadian Metallurgical Quarterly》1996,317(8):66-70, 80
From position of the uniform concept of the accident medicine the problems of toxicological supply of the ships of MNF are considered. Peculiarities of chemical accidents in the ship conditions are marked. The question about principles of harmful chemical substances regulating, forming air environment of ship living quarters is discussed. The prospects of practical use of antidotal means, intended for protection of personnel from toxic action of carbon dioxide and chemical combinations, causing development of toxic edema of lungs are given. 相似文献
119.
Diabetic ulcers are the most common foot injuries leading to lower extremity amputation. Family physicians have a pivotal role in the prevention or early diagnosis of diabetic foot complications. Management of the diabetic foot requires a thorough knowledge of the major risk factors for amputation, frequent routine evaluation and meticulous preventive maintenance. The most common risk factors for ulcer formation include diabetic neuropathy, structural foot deformity and peripheral arterial occlusive disease. A careful physical examination, buttressed by monofilament testing for neuropathy and noninvasive testing for arterial insufficiency, can identify patients at risk for foot ulcers and appropriately classify patients who already have ulcers or other diabetic foot complications. Patient education regarding foot hygiene, nail care and proper footwear is crucial to reducing the risk of an injury that can lead to ulcer formation. Adherence to a systematic regimen of diagnosis and classification can improve communication between family physicians and diabetes subspecialists and facilitate appropriate treatment of complications. This team approach may ultimately lead to a reduction in lower extremity amputations related to diabetes. 相似文献
120.
The -514 polymorphism in the hepatic lipase gene (LIPC) is associated with decreased hepatic lipase activity. In the present study, the interaction between body mass index (BMI), the -514 polymorphism, and hepatic lipase activity was examined in 118 white men and in 51 African American men. BMI was significantly positively correlated with hepatic lipase activity in both populations. BMI was similar in men with genetic differences in hepatic lipase activity, indicating that high hepatic lipase activity did not cause increased BMI. The data therefore suggest that high BMI leads to increased hepatic lipase activity. The actions of BMI and the -514 polymorphism on hepatic lipase activity appear to be additive and independent, rather than synergistic. This finding indicates that hepatic lipase activity is a multifactorial trait, determined in part by polymorphism within the LIPC gene as well as by factors that influence BMI. 相似文献