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   2390篇
  免费   0篇
化学工业   6篇
金属工艺   1篇
机械仪表   3篇
建筑科学   1篇
能源动力   2篇
轻工业   1篇
一般工业技术   13篇
冶金工业   2358篇
自动化技术   5篇
  2022年   1篇
  2021年   1篇
  2013年   2篇
  2012年   2篇
  2010年   1篇
  2008年   1篇
  2006年   2篇
  2004年   3篇
  2003年   7篇
  2000年   1篇
  1999年   82篇
  1998年   804篇
  1997年   478篇
  1996年   248篇
  1995年   156篇
  1994年   126篇
  1993年   138篇
  1992年   13篇
  1991年   16篇
  1990年   22篇
  1989年   25篇
  1988年   22篇
  1987年   22篇
  1986年   12篇
  1985年   9篇
  1983年   4篇
  1982年   4篇
  1981年   17篇
  1980年   10篇
  1978年   2篇
  1977年   44篇
  1976年   106篇
  1975年   4篇
  1973年   1篇
  1972年   1篇
  1955年   3篇
排序方式: 共有2390条查询结果,搜索用时 15 毫秒
991.
We examined the effects of hand dominance and the patients' stated preference of the sleeping position on the survival of vascular accesses for hemodialysis in different locations. Analysis was made of vascular access survival times after 1, 126 vascular access surgeries performed between January 1, 1989, and December 31, 1994. We found that hand dominance and access site were not related to any survival differences in patients with autogenous fistulas, but thigh grafts on both sides had greater survival than arm grafts. The preferential side for sleeping similarly did not seem to affect access survival, but patients who stated a sleep preference on the side opposite their vascular graft tended to have longer access survival time.  相似文献   
992.
BACKGROUND: Irradiation of platelet concentrates (PCs) with ultraviolet-B (UVB) light inactivates the contaminating white cells and might be an alternative to filtration for the prevention of alloimmunization to HLA antigens and subsequent refractoriness to further platelet transfusions in multiply transfused patients with bone marrow failure. STUDY DESIGN AND METHODS: Patients with hematologic malignancy, mainly acute myeloid leukemia, were prospectively assigned in a random manner to receive either UVB-irradiated or control, nonirradiated PCs. All patients were given red cells that were white cell reduced by filtration. Transfusion efficacy and alloimmunization were assessed by means of corrected count increments, requirement for red cells and PCs, and measurement of lymphocyte-reactive antibodies. RESULTS: UVB-irradiated PCs had a clinical efficacy similar to controls as judged by corrected count increments at 1 to 6 and 12 to 24 hours and by the median requirement for red cell and platelet transfusions. Alloimmunization determined by measurements of lymphocyte-reactive antibodies using both conventional and antiglobulin-augmented lymphocytotoxicity techniques was not abolished in recipients of UVB-irradiated PCs (4/30, 13%) but was less than that in controls (5/20, 25%; p = NS). The mean number of platelet transfusion episodes prior to the occurrence of alloimmunization was greater in the control group (27 vs. 10; p = 0.017). CONCLUSION: In this trial, UVB irradiation did not diminish the clinical efficacy of platelet transfusions. There was a small but nonsignificant reduction alloimmunization, but no difference in refractoriness of the two groups was observed. Larger prospective randomized studies are required to confirm these findings and to compare UVB irradiation with white cell reduction.  相似文献   
993.
In mid-January 1993, an outbreak of Escherichia coli O157:H7 infections associated with eating hamburger patties at a fast-food restaurant chain (chain A) was reported in Washington State. From mid-December to mid-January, 9 cases of E coli O157:H7-associated bloody diarrhea and the hemolytic-uremic syndrome had been reported in San Diego County, California. A total of 34 persons had bloody diarrhea, the hemolytic-uremic syndrome, or E coli O157:H7 organisms isolated from stool during the period November 15, 1992, through January 31, 1993. Organisms of E coli O157:H7 identified from 6 persons were indistinguishable from those of the Washington outbreak strain. Illness was associated with eating at chain A restaurants in San Diego (odds ratio, 13; 95% confidence interval, 1.7, 99) and with eating regular-sized hamburgers (odds ratio, undefined; lower-limit 95% confidence interval, 1.3). Improved surveillance by mandating laboratory- and physician-based reporting of cases of E coli O157:H7 infection and the hemolytic-uremic syndrome might have alerted health officials to this outbreak sooner, which could have resulted in earlier investigation and the institution of measures to prevent more cases.  相似文献   
994.
995.
996.
Fluorescence in situ hybridization, or chromosome painting, has become an invaluable tool in the cytogenetic evaluation of historical or chronic exposure because it can be used to detect stable genetic damage, such as translocations, which persist through cell division, quickly and easily. The recent development of chromosome-specific composite DNA probes for the mouse has allowed the use of chromosome painting in this commonly used animal model. In order to measure the persistence of radiation-induced translocations, C57BL/6 female mice were given a whole body acute dose of 0, 1, 2, 3 or 4 Gy 137Cs gamma rays at 8 weeks of age. Metaphase chromosomes from both peripheral blood and bone marrow cells were obtained from four mice in each dose group at 1, 8, 15 and 30 days post-irradiation. Chromosomes 2 and 8 were painted, while the remaining chromosomes were counterstained with propidium iodide. DAPI counterstain was used to differentiate between translocations and dicentrics because it brightly labels the centromeric heterochromatin. The equivalent of 100 cells from each tissue was scored from each mouse. The results show that the percentage of reciprocal translocations, at least at doses of 3 Gy or lower, did not decrease with time in either tissue. In contrast, the frequency of non-reciprocal translocations induced by doses of 3 Gy or lower, remained unchanged in the peripheral blood, but decreased after a week in the bone marrow, then remained constant. An increase in these two types of aberration was observed between 15 and 30 days in the bone marrow and may have been due to clonal expansion. Dicentrics decreased with time in both tissues, almost none remained in the bone marrow after 8 days. These data suggest that reciprocal translocations are persistent and will serve as an effective biodosimeter for radiation exposure.  相似文献   
997.
Attitudes of 40 interns towards rational drug use (RDU) were assessed, using a standardized Likert type scale. The assessment was repeated after 4 months to evaluate the effect of usual working conditions of the hospital. After this period, the attitudes had slided towards negative side (p < 0.01). At this point, an intervention in the form of a workshop was provided for half the group while other half served as control. A repeat assessment after another period of 4 months revealed that the attitudes of test group returned towards positive side (p < 0.01) while control group maintained its negative attitudes.  相似文献   
998.
999.
A term, male neonate suddenly developed respiratory distress and severe cyanosis while undergoing exchange transfusion for hyperbilirubinaemia. Transfusion-related acute lung injury was diagnosed. Because of persistent hypoxaemia despite aggressive treatment, two doses of surfactant were administered, resulting in marked improvement. Conclusion: Transfusion-related acute lung injury may occur in neonates, and may be successfully treated by surfactant replacement.  相似文献   
1000.
Two experiments were conducted to determine the effect of dietary linoleic to linolenic acid (LO:LN) ratio and dl-alpha-tocopheryl acetate (TA) supplementation on selected characteristics of the liver and cerebellum and on vitamin E status of turkey poults from hatch through 22 d of age. In Experiment 1, 1-d-old poults were fed diets containing no supplemental TA (0E) or 150 IU TA/kg diet (150E). Poults fed the 150E diet had greater (P < 0.001) concentrations of alpha-tocopherol (TOC) in the liver and plasma than those fed the 0E diet from 7 to 22 d of age. The 150E diet, however, did not completely overcome the decrease in liver and plasma TOC concentrations observed at these ages. The 150E diet had no effect on poult BW, feed efficiency, or on the weight, protein, lipid, or fatty acid concentrations of the liver. Thiobarbituric acid reactive substances assay of liver and hemolysis assay of red blood cells (RBC) showed that the 150E diet decreased the susceptibility of liver and RBC to in vitro peroxidation at 13 and 22 d of age. In Experiment 2, 1-d-old poults were fed the 0E and 150E diets in a complete factorial arrangement with decreasing ratios of LO:LN (10, 5, and 1). Dietary LO:LN ratio had no effect on RBC hemolysis or cerebellum TOC concentration. As the ratio of LO:LN decreased, the arachidonic acid content of liver and cerebellum lipids decreased. Ratios of n-6 to n-3 fatty acids in liver and cerebellum were directly related to dietary LO:LN at 13 and 22 d of age.  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