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   1967篇
  免费   0篇
电工技术   1篇
综合类   1篇
化学工业   12篇
金属工艺   1篇
机械仪表   1篇
建筑科学   1篇
矿业工程   1篇
能源动力   1篇
轻工业   26篇
水利工程   1篇
石油天然气   1篇
无线电   8篇
一般工业技术   31篇
冶金工业   1863篇
原子能技术   2篇
自动化技术   16篇
  2023年   1篇
  2022年   1篇
  2020年   1篇
  2018年   1篇
  2016年   1篇
  2013年   5篇
  2012年   3篇
  2011年   6篇
  2010年   5篇
  2009年   4篇
  2008年   4篇
  2007年   2篇
  2006年   3篇
  2005年   5篇
  2004年   4篇
  2003年   2篇
  2002年   5篇
  2001年   3篇
  2000年   4篇
  1999年   61篇
  1998年   546篇
  1997年   298篇
  1996年   227篇
  1995年   112篇
  1994年   94篇
  1993年   125篇
  1992年   23篇
  1991年   24篇
  1990年   20篇
  1989年   40篇
  1988年   25篇
  1987年   25篇
  1986年   18篇
  1985年   21篇
  1983年   2篇
  1982年   14篇
  1981年   14篇
  1980年   15篇
  1978年   5篇
  1977年   62篇
  1976年   120篇
  1975年   4篇
  1974年   4篇
  1973年   2篇
  1971年   1篇
  1969年   1篇
  1964年   1篇
  1961年   1篇
  1958年   1篇
  1955年   1篇
排序方式: 共有1967条查询结果,搜索用时 687 毫秒
81.
A cardiac transplant recipient with multiple coronary artery fistulae draining into the right ventricle is described. These fistulae presumably resulted from repeated endomyocardial biopsies. The diagnosis of coronary artery fistulae was made at the annual coronary arteriography. The magnitude of the shunt remained small over eight years of follow-up.  相似文献   
82.
The prognosis in patients with primary brain tumors treated with surgery, radiotherapy and conventional chemotherapy remains poor. To improve outcome, combination high-dose chemotherapy (HDC) has been explored in children, but rarely in adults. This study was performed to determine the tolerability of three-drug combination high-dose thiotepa (T) and etoposide (E)-based regimens in pediatric and adult patients with high-risk or recurrent primary brain tumors. Thirty-one patients (13 children and 18 adults) with brain tumors were treated with high-dose chemotherapy: 19 with BCNU (B) and TE (BTE regimen), and 12 with carboplatin (C) and TE (CTE regimen). Patients received growth factors and hematopoietic support with marrow (n = 15), peripheral blood progenitor cells (PBPC) (n = 11) or both (n = 5). The 100 day toxic mortality rate was 3% (1/31). Grade III/IV toxicities included mucositis (58%), hepatitis (39%) and diarrhea (42%). Five patients had seizures and two had transient encephalopathy (23%). All patients had neutropenic fever and all pediatric patients required hyperalimentation. Median time to engraftment with absolute neutrophil count (ANC) >0.5 x 10(9)/l was 11 days (range 8-37 days). Time to ANC engraftment was significantly longer (P = 0.0001) in patients receiving marrow (median 14 days, range 10-37) than for PBPC (median 9.5 days, range 8-10). Platelet engraftment >50 x 10(9)/l was 24 days (range 14-53 days) in children. In adults, platelet engraftment >20 x 10(9)/l was 12 days (range 9-65 days). In 11 patients supported with PBPC, there was a significant inverse correlation between CD34+ dose and days to ANC (rho = -0.87, P = 0.009) and platelet engraftment (rho = -0.85, P = 0.005), with CD34+ dose predicting time to engraftment following HDC. Overall, 30% of evaluable patients (7/24) had a complete response (CR) (n = 3) or partial response (PR) (n = 4). Median time to tumor progression (TTP) was 7 months, with an overall median survival of 12 months. These TE-based BCNU or carboplatin three-drug combination HDC regimens are safe and tolerable with promising response rates in both children and older adults.  相似文献   
83.
The percutaneous cardiopulmonary support system (PCPS) was used in a 64-year-old woman with cardiogenic shock due to sustained ventricular fibrillation (Vf) caused by severe aortic stenosis and regurgitation. The Vf attack was resistant to cardioversion and adrenaline for lack of left ventricular support by PCPS. She was transported to the operation theater with PCPS in situ and emergency aortic valve replacement was performed. Although preoperative cardiac resuscitation time was long (35 minutes), she was discharged from the hospital on foot without any neurological complications on 84th postoperative day. Because PCPS does not decrease left ventricular systolic stress in poorly contracting dilated heart, early surgical treatment is needed in patients with severely damaged heart.  相似文献   
84.
85.
We examined whether timeline icons improved older and younger adults' comprehension of medication information. In Experiment 1, comprehension of instructions with the icon (icon/text format) and without the icon (text-only format) was assessed by questions about information that was (a) implicit in the text but depicted explicitly by the icon (total dose in a 24 hour period), (b) stated and depicted in the icon/text condition (medication dose and times), and (c) stated but not depicted by the icon (e.g., side effects). In a separate task, participants also recalled medication instructions (with or without the icon) after a study period. We found that questions about dose and time information were answered more quickly and accurately when the icon was present in the instructions. Notably, icon benefits were greater for information that was implicit rather than stated in the text. This finding suggests that icons can improve older and younger adults' comprehension by reducing the need to draw some inferences. The icon also reduced effective study time (study time per item recalled). In Experiment 2, icon benefits did not occur for a less integrated version of the timeline icon that, like the text, required participants to integrate dose and time information in order to identify the total daily dose. The integrated version of the icon again improved comprehension, as in Experiment 1, as well as drawing inferences from memory. These findings show that integrated timeline icons improved comprehension primarily by aiding the integration of dose and time information. These findings are discussed in terms of a situation model approach to comprehension.  相似文献   
86.
Our objective was to examine the influence of feeding and endogenous GH secretion on circulating IGF-I in colostrum-deprived newborn pigs fed colostrum (n = 4), formula (control, n = 4), or water (n = 4). In another four formula-fed pigs, GH was ablated (GRF-A) with two intravenous injections of a GH releasing-factor antagonist (N-Ac-Tyr1,D-Arg2)-GRF(1-29)-NH2. Blood was serially sampled in all pigs to measure plasma IGF-I and GH profiles. Feeding increased plasma IGF-I concentration two- to fourfold and decreased GH secretion. Despite a more than 80% decrease in the plasma GH in GRF-A pigs, the circulating IGF-I concentration was similar to that in control pigs. In colostrum-fed pigs, plasma IGF-I was higher than that in control pigs, despite equal nutrient intake and lower circulating GH. There were no differences in plasma IGF binding protein (IGFBP)-3 levels among the treatment groups. However, the relative abundance of plasma IGFBP-4 was lower, and that of IGFBP-1 higher, in unfed pigs than in any of the three fed groups. The plasma insulin concentration was not different among fed pigs, but it was lower in unfed pigs. Our results indicate that the circulating IGF-I concentration is more dependent on nutrient intake than on GH in newborn pigs, despite relatively high GH concentrations. However, because the nutrient content in the formula was designed to match that of colostrum, a factor other than nutrient intake and GH was responsible for the maximal increase in circulating IGF-I concentration observed in colostrum-fed pigs.  相似文献   
87.
BACKGROUND: Meningeal hemangiopericytoma is an uncommon neoplasm with a high propensity for recurrence. The purpose of this study was to analyze the efficacy of different treatment options in patients with recurrent disease. METHODS: The records of all patients with recurrent meningeal hemangiopericytoma treated at the study institution between 1976 and 1996 were reviewed. RESULTS: Thirty-four consecutive patients were studied. The mainstay of treatment was brain surgery in 21 patients (62%); the median time to recurrence from surgery was 12 months. Ten patients (29%) had 20 recurrent central nervous system (CNS) lesions treated by stereotactic radiosurgery. Of these, 3 previously nonirradiated patients (all with lesion size < 25 mm) achieved a complete response, which persisted at a median of 3 years. In 14 lesions (70%) a partial response (PR) occurred with a median duration of 12 months, whereas 3 lesions (15%) remained stable. Two patients with inoperable CNS lesions received external beam radiation therapy and both had PRs lasting 14 and 24 months, respectively. Nine patients (26%) received radiation therapy for metastatic disease. Of these, seven patients remained stable with good symptomatic relief, and two patients experienced tumor progression. Chemotherapy with doxorubicin-containing regimens was administered in 7 patients (21%); there was only 1 PR that lasted 8 months. The median survival from first recurrence was 4.6 years. CONCLUSIONS: Surgical management is important for the successful treatment of patients with recurrent meningeal hemangiopericytoma. Radiosurgery plays a definite role in the treatment of smaller recurrent CNS lesions. Radiation therapy is helpful in the management of inoperable tumors. More effective chemotherapeutic agents are needed.  相似文献   
88.
89.
This study examined differences between long-term exercising (LE) and long-term nonexercising (LNE) women [n = 24; age 56.4 +/- 6.2 (SD) yr] for resting metabolic rate (RMR) and energy expenditure in the free-living state by using doubly labeled water (DLW). There was a statistically significant difference (P = 0.0002) between the 12 LE (94.85 +/- 8.44 kJ . kg-1 . day-1) and 12 LNE (81.16 +/- 6.62 kJ . kg-1 . day-1) for RMR, but this difference was only marginally significant (P = 0.06) when the data (MJ/day) were subjected to an analysis of covariance with fat-free mass as the covariate. The DLW data indicated that the eight most active LE (12.99 +/- 3.58 MJ/day) expended significantly (P = 0.01) more energy than did the eight least active LNE (9.30 +/- 1.15 MJ/day). Energy expenditures ranged from 7.64 to 18.15 MJ/day, but there was no difference (P = 0.96) between the LE and LNE in energy expenditure during activity that was not designed to either improve or maintain fitness. These cross-sectional data on 49- to 70-yr-old women therefore suggest that 1) aerobic-type training results in a greater RMR per unit of body mass and also when statistical control is exerted for the effect of the metabolically active fat-free mass, 2) there is a large range in the energy intake necessary to maintain energy balance, and 3) aerobic training does not result in a compensatory reduction in energy expenditure during the remainder of the day.  相似文献   
90.
Human procathepsin L has been expressed in E. coli in the form of inclusion bodies. The recombinant protein was isolated, refolded and processed at pH 5.5 by the addition of dextran sulfate which increased the overall yield of cathepsin L almost 10-fold. After the auto-activation of the 38 kDa procathepsin L at least three processing sites were determined by N-terminal amino acid sequencing. After replacing the Ala205 residue by glutamic acid, cathepsin B-like specificity was introduced into cathepsin L. This mutation resulted in a 15-fold increased activity toward the substrate Z-Arg-Arg-AMC and in a 29-fold decreased activity toward Z-Phe-Arg-AMC. Residue 205 is thereby confirmed experimentally to be critical for the specificity of cathepsins B and L.  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