全文获取类型
收费全文 | 2684篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 65篇 |
金属工艺 | 5篇 |
机械仪表 | 1篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 2篇 |
轻工业 | 41篇 |
水利工程 | 3篇 |
无线电 | 28篇 |
一般工业技术 | 39篇 |
冶金工业 | 2463篇 |
原子能技术 | 6篇 |
自动化技术 | 15篇 |
出版年
2019年 | 5篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 18篇 |
2000年 | 6篇 |
1999年 | 85篇 |
1998年 | 776篇 |
1997年 | 397篇 |
1996年 | 293篇 |
1995年 | 144篇 |
1994年 | 121篇 |
1993年 | 139篇 |
1992年 | 25篇 |
1991年 | 36篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 76篇 |
1976年 | 170篇 |
1975年 | 11篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1967年 | 4篇 |
1965年 | 3篇 |
1961年 | 3篇 |
1960年 | 3篇 |
排序方式: 共有2693条查询结果,搜索用时 15 毫秒
871.
WJ Gardner 《Canadian Metallurgical Quarterly》1977,3(4):200-212
The Dandy-Walker malformation (DWM) is hydrocephalus that primarily affects the fourth ventricle, whose overdistention involves also the aqueduct and third ventricle. However, just the opposite is true in the Arnold-Chiari malformation (ACM) since the hydrocephalus is limited to the lateral ventricles which squeeze the third ventricle between them and compress the aqueduct and fourth ventricle. The evidence indicates that both result from hydrodynamic stresses in embryonal and early fetal life. This communication is offered in rebuttal to some statements in an otherwise authoritative and comprehensive article. 相似文献
872.
Sauna-takers disease. Hypersensitivity pneumonitis due to contaminated water in a home sauna 总被引:1,自引:0,他引:1
WJ Metzger R Patterson J Fink R Semerdjian M Roberts 《Canadian Metallurgical Quarterly》1976,236(19):2209-2211
Daily saunas taken by a young man were followed by fever, chills, malaise, dyspnea, cough, and myalgia from six to eight hours later. Symptoms, which were related to pouring water from a sauna bucket over the heating element, progressed to chronic dyspnea and fatigue. Serial serum samples showed precipitin reactions to bucket water and extracts of bucket mold. IgG antibody activity, demonstrated by radioimmunoassay, suggested that Pullularia was a major antigen. 相似文献
873.
874.
A case-control study of nasal cancer, based on death certificate statements on occupation in North Carolina counties with furniture-manufacturing industries, revealed a 4-fold excess risk linked to this occupation. Although woodworking exposures have been associated with nasal adenocarcinomas in several areas of the world, this is the first report of such a relationship in the United States. 相似文献
875.
Anisotropic magnetoresistance in ferromagnetic 3d alloys 总被引:9,自引:0,他引:9
The anisotropic magnetoresistance effect in 3d transition metals and alloys is reviewed. This effect, found in ferromagnets, depends on the orientation of the magnetization with respect to the electric current direction in the material. At room temperature, the anisotropic resistance in alloys of Ni-Fe and Ni-Co can be greater than 5%. The theoretical basis takes into account spin orbit coupling and d band splitting. Other properties such as permeability, magnetostriction, and Hall voltage have no simple relationship to magnetoresistance. Anisotropic magnetoresistance has an important use as a magnetic field detector for digital recording and magnetic bubbles. Such detectors because of their small size are fabricated using thin film technology. Film studies show that thickness, grain size, and deposition parameters play a significant role in determining the percentage change in magnetoresistance. In general, the change is smaller in films than bulk materials. Several tables and graphs that list bulk and film data are presented. 相似文献
876.
DA Southgate WJ Branch MJ Hill BS Drasar RL Walters PS Davies IM Baird 《Canadian Metallurgical Quarterly》1976,25(10):1129-1135
During a metabolic ward study, the addition of dietary fiber in the form of wheat bran biscuits to the diet of five volunteer subjects resulted in an increase in the stool wet weight and fecal solids. The excretion of fecal solids was highly correlated with the intake of unavailable carbohydrates, and fecal losses of water were similarly correlated with fecal excretion of these constituents. The major component of the increase in fecal solids was due to the noncellulosic polysaccharide fraction of dietary fiber. There was an increased fecal excretion of nitrogen fat and energy by most subjects when the supplement was eaten. However, the increased loss of energy in the feces was only 40-80 kcal/day, and therefore a large supplemental intake of dietary fiber had only minor effects on energy metabolism. Supplemental fiber is thus unlikely to induce a useful loss of calories in the management of obesity. The addition of dietary fiber caused an increased excretion of most inorganic constituents, particularly sodium and phosphorus; increased excretion of iron and magnesium was also found in two subjects. 相似文献
877.
Survey of hospitals and clinics where atomic bomb survivors and their comparisons reported having received radiation therapy confirmed that 137 were so treated. The malignancies of five subjects were possibly related to their earlier radiation therapy rather than their atomic bomb radiation exposure, stressing the importance of recording all medical X-ray exposures as a potential variable in epidemiological studies of cancer etiology. 相似文献
878.
879.
This investigation was designed to determine the role of echocardiography in the assessment of left ventricular function in patients with significant coronary arterial disease. Satisfactory echocardiograms were obtained in 43 patients with coronary arterial disease. The ventriculographic ejection fraction was determined by the area length method. The echocardiographic left ventricular end-diastolic dimension was increased to more than 5-4 cm in 17 patients. Fifteen of these patients had an ejection fraction of 0-45 or less. Three patients had a normal left ventricular end-diastolic dimension but an ejection fraction of less than 0-45. Twenty-three patients had an ejection fraction of more than 0-45 and a normal left ventricular end-diastolic dimension. The left ventricular end-diastolic dimension index was increased (greater than 3 cm/m2) in 15 patients, all of whom had ejection fraction of less than 0-45. Three patients had a normal left ventricular end-diastolic dimension index and an ejection fraction of less than 0-45. Twenty-five patients had a left ventricular end-diastolic dimension index of less than 3 cm/m2 or less and an ejection fraction of more than 0-45. The percentage fractional shortening of the echocardiographic left ventricular dimension was reduced in 25 patients. In 18 of these the ejection fraction was 0-45 or less. The percentage fractional shortening of the left ventricle was normal in 18 patients. In 2 of them the ejection fraction was less than 0-45. In summary, increase of the left ventricular end-diastolic dimension or left ventricular end-diastolic dimension index is usually associated with a critical reduction of the ejection fraction as determined by ventriculography. Since the ejection fraction is an important determinant of mortality related to bypass graft surgery, echocardiography should be useful in the detection of patients with a poor prognosis. 相似文献
880.
Foals with combined immunodeficiency (CID), a fatal genetic defect in the production of both B and T lymphocytes, are born without immunoglobulins and are unable to synthesise them. CID foals receiving immunoglobulins via the dam's colostrum may live up to four months of age. Those CID foals with failure of passive transfer (FPT) die at a much earlier age. The occurrence of CID is of value in studying passive transfer of immunoglobulins, as no confusion exists as to when passive transfer ends and active synthesis of immunoglobulins begins. A high correlation has been found between early foal disease and deaths and lack of passive transfer of immunoglobulins, even though many of these foals appear to nurse normally during the first few hours post partum. Evaluation of immunoglobulin levels in 24 hour post suckle samples would prove of value not only in diagnosing CID foals, but in recognising FPT in otherwise normal foals. 相似文献