首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4159篇
  免费   0篇
化学工业   14篇
金属工艺   2篇
建筑科学   1篇
矿业工程   3篇
能源动力   6篇
轻工业   3篇
无线电   1篇
一般工业技术   5篇
冶金工业   4116篇
自动化技术   8篇
  2022年   1篇
  2021年   2篇
  2020年   2篇
  2013年   2篇
  2011年   3篇
  2010年   1篇
  2009年   2篇
  2007年   1篇
  2006年   1篇
  2005年   2篇
  2004年   4篇
  2003年   12篇
  1999年   122篇
  1998年   1224篇
  1997年   760篇
  1996年   456篇
  1995年   253篇
  1994年   206篇
  1993年   250篇
  1992年   32篇
  1991年   37篇
  1990年   54篇
  1989年   47篇
  1988年   69篇
  1987年   47篇
  1986年   44篇
  1985年   45篇
  1983年   7篇
  1982年   20篇
  1981年   31篇
  1980年   40篇
  1978年   4篇
  1977年   121篇
  1976年   242篇
  1975年   5篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1961年   1篇
  1955年   5篇
  1954年   1篇
排序方式: 共有4159条查询结果,搜索用时 15 毫秒
51.
A modified technique for vaso-vasostomy is described with the aim to achieve better results in operative recanalization and restoration of fertility after vasectomy. Vaso-vasostomy is a success when the man is able to produce fertile semen. Criteria for a fertile semen are mentioned. Fertile semen was obtained in all 5 patients treated by this modified technique.  相似文献   
52.
The effects of age, sex, and neutering on the prevalence of canine intestinal parasitism were evaluated by fecal examination of 1,468 pet dogs admitted to the University of Missouri Veterinary Teaching Hospital during 1975. Evidence of hookworm infection was encountered in 35.8% of the dogs examined, whipworms in 18.5%, ascarids in 17.9%, tapeworms in 5.2%, and coccidia in 4.5%. Evidence of intestinal parasitism was not detected in 653 (44.4%) dogs. Whipworm infections were detected less often in young dogs than in older ones, whereas ascarid and coccidial infections were more prevalent in pups that in mature dogs. In dogs more than 6 months old, hookworm infections were the most common parasitism. Tapeworm infections were diagnosed sporadically in all age groups. For most of these parasites, castrated males and spayed females had decreased prevalence of infection, compared with their respective intact counterparts. There were significant (P less than 0.05) differences in the prevalence of both ascarid and hookworm infections between intact and spayed female dogs. Also, there were significant (P less than 0.001) differences between age categories for all parasites observed. Overall, parasitism tended to decrease with age.  相似文献   
53.
54.
1. Chemical and morphological features of uraemic bone disease were studied by comparison of bone composition in 44 patients with uraemia (12 dialysed and 32 non-dialysed) and 36 control subjects. The significant changes included decreased bone mineral carbonate associated with calcium, a concomitant increase in phosphate, and an increase in magnesium. There was also an increase in osteoid and a reduction in the specific gravity of the compact bone. 2. The most marked changes in bone composition were observed in patients with uraemia of more than 1 year's duration, who had been dialysed. Bone mineral sodium concentrations were not significantly altered in any group. 3. The changes in bone mineral composition appeared to be the result of several simultaneous and/or successive mechanisms: (i) loss of fixed base, calcium carbonate; (ii) replacement of carbonate by phosphate; (iii) the addition of immature bone mineral, which contains high concentrations of phosphate and relatively low concentrations of carbonate. 4. These observations are consistent with earlier views of the bone salt as an indefinite calcium/phosphate/carbonate complex. Variations in bone composition may arise from a reciprocal relationship between phosphate and carbonate. The bone mineral analogue that best explains these variations in bone composition is octacalcium phosphate carbonate [Ca4 (PO4)2(HPO4)x(CO3)1-x,zH2O].  相似文献   
55.
Experience with short tube decompressive jejunostomy in twenty-nine patients with small bowel obstruction is presented. Many advantages are gained by operative decompression of obstructed, dilated small bowel. The favorable results with its use make short tube decompressive jejunostomy a safe, acceptable method of decompressing dilated small bowel.  相似文献   
56.
57.
58.
59.
ts-2, a temperature-sensitive and plaque morphology mutant of respiratory syncytial virus and sole representative of complementation group B, was compared with members of the other complementation groups of respiratory syncytial virus (group A [ts-1] and group C [ts-7]). ts-2 was found to be 10- to 1,000-fold more restricted in growth and ability to spread at restrictive temperatures (37, 38, and 39 degrees C) than at the permissive temperature (32 degrees C). In temperature shift-up experiments, the ts defect of ts-1 and other members of complementation group A was found to effect a late function that was required for at least 13 h in the replicative cycle. The ts lesion of ts-7 affected a function early in the replication cycle. In contrast, ts-2 was not temperature sensitive when studied by the shift-up technique. The discrepancy between the ts plaque property and failure to detect temperature sensitivity during the shift-up experiment was resolved when it was shown that ts-2 had a defect in adsorption or penetration or both at the restrictive temperature. Clonal analysis of revertant ts-2 showed a coordinate restoration of ts+ phenotype ans syncytium-forming capacity. It appears that ts-2 has a defect in a protein that is involved in adsorption and/or penetration of virus and is also responsible for cell fusion activity.  相似文献   
60.
The concept that carbohydrate intolerance improves after hemodialysis has been challenged. Critical to this issue is the reproducibility of GTT in a dialysis population. Thirty-nine oral or i.v. GTT were performed on ten stable hemodialysis patients at weekly intervals for three weeks. Blood glucose was determined by both oxygen consumption rate during glucose oxidation and the ferricyanide method. The coefficient of variation of blood glucose ratios (Glucose at time X/Fasting glucose) by glucose oxidase varied considerably. With the i.v. GTT the coefficients of variation at 90 and 120 minutes were 27.9 and 36.8 percent in one patient but below 15 percent at 60, 90, and 120 minutes in the other four patients. Three of the five patients who received oral GTT displayed coefficients of variation greater than 20 percent at one or more sampling times. The coefficients of variation of the growth hormone ratio (Growth hormone at time X/Fasting growth hormone) during i.v. and oral GTT ranged from 2.1 to 83.6 percent. Coefficients of variation of insulinogenic indexes ranged from 16.3 to 59.3 percent. In summary, large variations in glucose, growth hormone and insulin occur during both oral and i.v. GTT when repeated on a weekly basis in stable hemodialysis patients.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号