全文获取类型
收费全文 | 644篇 |
免费 | 0篇 |
专业分类
化学工业 | 73篇 |
机械仪表 | 3篇 |
建筑科学 | 8篇 |
矿业工程 | 2篇 |
能源动力 | 1篇 |
轻工业 | 35篇 |
水利工程 | 2篇 |
无线电 | 11篇 |
一般工业技术 | 29篇 |
冶金工业 | 475篇 |
自动化技术 | 5篇 |
出版年
2024年 | 5篇 |
2023年 | 5篇 |
2022年 | 3篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2007年 | 6篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 123篇 |
1997年 | 66篇 |
1996年 | 62篇 |
1995年 | 33篇 |
1994年 | 27篇 |
1993年 | 32篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 21篇 |
1976年 | 34篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 6篇 |
1971年 | 9篇 |
1968年 | 2篇 |
1967年 | 5篇 |
1966年 | 6篇 |
1955年 | 2篇 |
1924年 | 2篇 |
1917年 | 2篇 |
1911年 | 2篇 |
1910年 | 2篇 |
1906年 | 3篇 |
1901年 | 2篇 |
1899年 | 2篇 |
排序方式: 共有644条查询结果,搜索用时 15 毫秒
631.
632.
633.
634.
635.
MA Kamel H Troonen HP Kapprell A el-Ayady FD Miller 《Canadian Metallurgical Quarterly》1995,47(4):399-403
The seroendemicity of hepatitis E virus (HEV) in an entire village population located in the Egyptain Nile Delta is described. Serum specimens were obtained from 68% of the total population of 1,850 villagers. The lack of serum specimen was greatest in the youngest age group (< 5). Commercially available enzyme immunoassays (EIA) for antibody to hepatitis A virus (anti-HAV), to hepatitis B virus core antigen (anti-HBc), to second-generation hepatitis C virus (anti-HCV) core and nonstructural antigen, and to hepatitis E virus (HEV) were used. Only repeated reactive sera were coded as positive. Stool specimens were examined for Schistosoma mansoni by the Kato method and standard methods for the examination of the liver and spleen by ultrasonography were used. Unadjusted for nonrespone, the seroprevalence of anti-HEV was 17.2% (SE +/- 1.1). Anti-HEV seroprevalence increased by age and was not associated statistically with any of the other viral markers including HCV. Anti-HAV seroprevalence was consistently > 95%, even in the youngest age group (< 5). The overall sero-endemicity of HEV was higher than reported elsewhere and appears not to have been introduced into the village population recently. 相似文献
636.
Portal hypertension is an uncommon but serious complication in children. The etiology may be intrahepatic or from an extrahepatic vascular occlusion. The pathophysiology is unknown, but the development of increased vascular resistance and portal flow are believed to be the primary changes. Increased portal flow is created by a decrease in systemic vascular resistance regionalized to the splanchnic vascular bed. Abnormally reduced response to vasoactive substances may be responsible. Advances in ultrasonography and endoscopy may improve our ability to evaluate portal hypertensive vascular changes. However, pharmacologic management is still limited to controlling the hemodynamic disturbances after they have occurred. Nonsurgical shunt management is increasingly being used in children, limiting the need for surgical shunt placement. Liver transplantation is now a viable option for managing end-stage disease. Future management depends on understanding the role of vasoactive substances controlling portal flow velocity, subsequent development of targeted pharmacologic therapy, and application of nonsurgical shunt technology in children. Transjugular intrahepatic portosystemic shunt placement is the next technologic advance moving from the adult into the pediatric realm. 相似文献
637.
In atropine-pretreated guinea pigs, electric stimulation of vagus (ESV, 10 Hz, 5 ms, 2 V or 10 V, for 90 s) increased intrapulmonary pressure (IPP), and Evans blue extravasation in trachea, main bronchi, peripheral and distal intrapulmonary airways in a voltage-dependent manner. ONO-1078, a noval leukotriene antagonist, (0.03 and 0.1 mg.kg-1, iv) showed no remarkable inhibiting effect on ESV-induced increase of IPP. However, the agent significantly inhibited ESV-induced increase of Evans blue extravasation in the airways, especially in lower potency of stimulation (2 V). The results suggest that leukotrienes may be involved in airway microvascular leakage in response to neurogenic inflammation. 相似文献
638.
FD Hobbs JE Kenkre YH Carter GH Thorpe RL Holder 《Canadian Metallurgical Quarterly》1996,46(408):395-400
BACKGROUND: The applications of new diagnostic technologies such as near patient tests are relevant to the further development and potential of primary care. Through their use, doctors in the community may increase the accuracy of their diagnoses and improve their ability to monitor disease. A reliable indicator of disease activity in various clinical conditions is C-reactive protein (CRP) and a near patient test for this is now available, although there is little information on its use outside hospitals. AIM: A study was set up to evaluate the feasibility of using a novel near patient test for CRP in primary care to validate the results against the laboratory "gold standard' for CRP (Beckman Array) and to compare results with the usual inflammation test used in general practice. METHOD: Prospective recording of CRP as a near patient test on an "intention to investigate' basis, with validation of results against the Beckman Array system for CRP and hospital laboratory erythrocyte sedimentation rate results, in six general medical practices in Birmingham. Main outcome measures were change in local laboratory usage, characteristics of patients chosen for testing, use of quality control, and comparison of readings with results from the same sample sent to an independent laboratory. RESULTS: Tests of CRP levels were rarely requested before the study was undertaken. During the 3-month study period, 181 near patient tests were carried out, 146 (81%) to establish a diagnosis and the remainder for disease monitoring. Out of the tests, 67% were performed by general practitioners, mostly during the consultation itself. Using a cut-off level of 10 mg I-1, the near patient test and the Beckman Array gave results which agreed in 84% of cases. The sensitivity and specificity of the near patient test results were 97 and 79%, respectively. The predictive value of a positive result was 59% and that of a negative result was 99%. Cohen's Kappa was 62% and the overall mean bias for results in the range of the test was 6.11 mg I-1 (SE = 3.07 mg I-1). Each test took 6 min on average to perform, including all preparations, blood letting, performing the test and averaging the time for quality control estimations. The cost per test averaged pounds 1.72, rising to pounds 4.17 including labour, capital costs, quality controls and consumables (general practitioner performing the assay at average frequency found in this study). CONCLUSIONS: Measurement of CRP is rarely used in primary care and awareness of its value could be raised. This near patient test proved feasible for use by general practitioners and practice nurses. Its reliability compared with a laboratory result was satisfactory overall, and excellent with adequate operator technique. 相似文献
639.
The authors present a rare soft tissue mass of the lower extremity that has been presented in the podiatric literature only once. Spindle cell hemangioendothelioma was first identified 9 years ago, and approximately 45 cases have been documented in the literature. This lesion presents as a slow growing and often painless lesion of the extremities, with low malignant potential and high local recurrence. This patient was treated with surgical excision after a mass, which had been present for more than 10 years, began enlarging and became painful. A review of the literature and the case presentation will be given. 相似文献
640.
A Chao TM Becker SW Jordan R Darling FD Gilliland CR Key 《Canadian Metallurgical Quarterly》1996,7(2):205-213
Minority women in New Mexico (United States)--including American Indian and Hispanic women--have shown disproportionately high incidence rates of invasive cervical cancer during the 1960s and 1970s. Several public health programs in New Mexico were directed toward early detection of cervical cellular abnormalities, particularly targeting the state's minority women. To evaluate the effectiveness of these programs, we examined the New Mexico Surveillance, Epidemiology, and End Results (SEER) data collected from 1969-92, and calculated average annual, age-specific, and age-adjusted incidence rates by ethnic group (American Indian, Hispanic, and non-Hispanic White) for five-year time intervals. We also calculated age-adjusted mortality rates for cervical cancer in the same ethnic groups using state vital records. Age-adjusted incidence rates for invasive cervical cancer show substantial temporal decreases, especially for minority women in the state. The age-adjusted incidence rate decreased by 66 percent, from 30.3 to 10.3 per 100,000 for American Indian women, and by 61 percent, from 26.1 to 10.2 per 100,000 for Hispanic women. A stage shift to earlier stages of cervical neoplasia occurred over the study period, with a substantially higher proportion of in situ compared with invasive cancers diagnosed in the most recent cf the most remote time period. The ratio of incidence rates of in situ to invasive cancers changed dramatically for both American Indian and Hispanic women. Cervical cancer mortality rates decreased steadily among Hispanic women from 1958 to 1992; the decrease among American Indian women was less stable and fluctuated due to small numbers. Ongoing targeted screening programs should help to reduce cervical cancer incidence and mortality further in New Mexico. 相似文献