全文获取类型
收费全文 | 5446篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 2篇 |
化学工业 | 14篇 |
建筑科学 | 2篇 |
能源动力 | 1篇 |
轻工业 | 7篇 |
水利工程 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 9篇 |
冶金工业 | 5389篇 |
自动化技术 | 17篇 |
出版年
2017年 | 2篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 165篇 |
1998年 | 1668篇 |
1997年 | 918篇 |
1996年 | 581篇 |
1995年 | 334篇 |
1994年 | 293篇 |
1993年 | 311篇 |
1992年 | 40篇 |
1991年 | 61篇 |
1990年 | 70篇 |
1989年 | 61篇 |
1988年 | 68篇 |
1987年 | 69篇 |
1986年 | 54篇 |
1985年 | 62篇 |
1984年 | 1篇 |
1983年 | 10篇 |
1982年 | 27篇 |
1981年 | 27篇 |
1980年 | 53篇 |
1979年 | 3篇 |
1978年 | 13篇 |
1977年 | 156篇 |
1976年 | 340篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有5449条查询结果,搜索用时 0 毫秒
31.
RA Hyman 《Canadian Metallurgical Quarterly》1976,120(3):551-552
A number renal and suprarenal pseudotumors have been described during the past two decades, paralleling the development of selective visceral angiography. An apparent left upper pole renal mass in a 71-year-old hypertensive man was found to ba a bulbous portion of the splenic vein during angiography. The anatomical basis of this renal pseudotumor is discussed. 相似文献
32.
GL Johnson RA Meyer DC Schwartz J Korfhagen S Kaplan 《Canadian Metallurgical Quarterly》1976,38(5):611-619
Left ventricular function was evaluated echocardiographically within 24 hours of cardiac catheterization in 45 children with fixed aortic stenosis. Left ventricular systolic time intervals, mean velocity of circumferential fiber shortening, left ventricular end-diastolic volume and shortening fraction were evaluated. Some patients with severe aortic stenosis had a shortened preejection period, prolonged ejection time and increased mean velocity of circumferential fiber shortening in comparison with normal subjects, but these findings were not consistent within the group with severe aortic stenosis or apparent in patients with mild or moderate aortic stenosis. Left ventricular end-diastolic volume was smaller in children with severe obstruction than in normal children. Evaluation of the shortening fraction provided good separation of patients with significant obstruction from those with mild disease. Further, there was a linear correlation between the shortening fraction and the left ventricular-aortic gradient demonstrated at cardiac catheterization. This correlation was also of use in evaluating the response of patients to surgical relief of obstruction. Pre- and postoperative echocardiographic evaluation of the shortening fraction appears to provide a readily available noninvasive method of assessing the course and severity of obstruction in fixed aortic stenosis in children. 相似文献
33.
34.
We have used dacryoscintigraphy to study the efficiency of the lacrimal system following the repair of a divided lower canaliculus in 4 children. This test has been reliable in evaluating lacrimal function and suggests that a canaliculus can be repaired and splinted satisfactorily. Our experience with dacryoscintigraphy confirms that it is a safe comfortable, and reliable method for studying the patency of the lacrimal drainage system. 相似文献
35.
Clinical and pathological study of 24 cases of gliosarcoma 总被引:1,自引:0,他引:1
The authors review the clinical and pathological features of 24 patients with gliosarcoma. The study revealed the following findings. Gliosarcoma occurs more frequently than is indicated in the literature, and in our series was present in 8% of all cases of glioblastoma multiforme. The presenting features are not significantly different from those of glioblastoma multiforme. The lesion often presents itself at surgery as a firm, well circumscribed mass within the temporal lobe, and at surgery it is commonly mistaken for a meningioma. There is an increased likelihood of metastasis compared to that of glioblastoma. The prognosis is no worse than that of glioblastoma, in spite of the addition of sarcomatous elements. 相似文献
36.
Two experiments were conducted to determine the effect of acute heat stress on late-stage chicken embryos. Embryos were incubated at a normal control temperature (37.5 degrees C.) for 16 days and were then subjected to 40.6, 43.3, 46.1 or 48.9 degrees C. for various periods of time in another incubator of the same type. At the end of the stress period all embryos were placed back into the control incubator for the remainder of the incubation period. Exposure of embryos for 24 hours to a temperature of 40.6 degrees C, caused no major detrimental effects on hatchability. Exposure for 6 hours to the temperature of 43.3 degrees C, caused a decrease in hatchability with a severe decline in hatchability occurring after 9 hours of exposure. Exposure to 46.1 degrees C. for 3 hours or 48.9 degrees C for 1 hour killed all embryos. Chicks which hatched following a severe heat stress had a high incidence of clubbed, wiry down and exhibited an unsteady gait. 相似文献
37.
RA Henderson 《Canadian Metallurgical Quarterly》1976,3(3):293-295
A new technique to insert acupuncture needles into the tissue without touching the needle with the fingers of the acupuncturist was developed by the authors. It is easy to perform and completely eliminates the problem of contamination. The bending of the needle is less frequent and the pain sensation of the patient is also minimized. 相似文献
38.
39.
40.
Five feeder pigs 4 to 6 months old were orally inoculated with transmissible gastroenteritis virus. Diagnosis of transmissible gastroenteritis was made on the basis of clinical signs and examination of intestinal mucosa by the fluorescent antibody technique. Immunoglobulins were extracted from intestinal fluid of infected feeder pigs. Virus-binding and neutralizing antibodies were detected in intestinal extracts between 7 and 56 days after infection. The concentration of binding antibodies reached a peak at 21 days after infection and was on the decline at the end of the experiment on the 56th postinfection day. In contrast, neutralizing intestinal antibody concentration was increasing on day 56. In both systems, the predominant immunoglobulin was of the IgA class. Examination of blood serums of the pigs by the plaque-reduction technique showed progressive antibody increases ranging in titer from 1:8 on day 7 to 1:256 on day 56 after infection. An analysis of the protein profiles from these serums showed a significant increase in the concentration of gamma-globulins and a decrease in the albumin fraction. 相似文献