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   979篇
  免费   3篇
化学工业   3篇
能源动力   5篇
轻工业   2篇
无线电   6篇
一般工业技术   24篇
冶金工业   939篇
自动化技术   3篇
  2022年   1篇
  2021年   2篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2014年   4篇
  2013年   1篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2007年   2篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2000年   3篇
  1999年   29篇
  1998年   291篇
  1997年   166篇
  1996年   97篇
  1995年   61篇
  1994年   70篇
  1993年   56篇
  1992年   5篇
  1991年   4篇
  1990年   3篇
  1989年   9篇
  1988年   7篇
  1987年   8篇
  1986年   6篇
  1985年   6篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   9篇
  1980年   11篇
  1979年   4篇
  1978年   3篇
  1977年   30篇
  1976年   70篇
  1975年   1篇
  1954年   1篇
排序方式: 共有982条查询结果,搜索用时 15 毫秒
91.
92.
93.
BACKGROUND: Myocardial revascularization in patients with left ventricular failure (ejection fraction < 30%) offers survival comparable to heart transplantation. The functional outcome, however, has yet to be determined. In order to assess the clinical results in patients with LVEF < 30% undergoing coronary artery bypass grafts (CABG), 101 consecutive patients operated between 1/91 and 1/97 were reviewed retrospectively. METHODS: The patients were stratified according to presentation: 65 pts had angina (Group 1) and 36 congestive failure (Group 2). Mean age (62 +/- 7 vs 60 +/- 8 yrs), sex (90 vs 88% male), LVEF (0.28 +/- 0.04 vs 0.29 +/- 0.04), prior myocardial infarction (1.2 +/- 0.4 vs 1.2 +/- 0.5 episodes/pt), presence of vital myocardium at scintiscan or low-dose dobutamine echocardiography (92 vs 93%), need for preoperative IABP (3.1 vs 8.3%), aortic cross-clamp (53 +/- 21 vs 60 +/- 21 min) and cardiopulmonary bypass (104 +/- 31 vs 114 +/- 36 min) times were comparable. RESULTS: There was only 1 (1%) perioperative death due to low-output syndrome. Eleven pts (6 vs 5, Group 1 vs Group 2) had postoperative low-output syndrome, requiring IABP in 7 pts (4 vs 3). There were 14 (10 vs 4, Group 1 vs Group 2) deaths during follow-up (29 +/- 19 months, range 2-67), with an overall actuarial survival of 91 +/- 4 vs 100% at 1 yr and 74 +/- 9 vs 78 +/- 10% at 5 yrs in Group 1 vs Group 2, respectively (p = ns). Actuarial symptom-free survival was 89 +/- 4 vs 84 +/- 6% at 1 yr and 49 +/- 9 vs 28 +/- 11% at 5 yrs, respectively (p = 0.05). Despite the high recurrence of congestive failure (22 vs 66% in Group 1 vs Group 2, p = 0.004), improvement in functional class (3.1 +/- 0.8 vs 1.5 +/- 0.7 in Group 1 and 2.7 +/- 0.7 vs 1.8 +/- 0.5 in Group 2) and LVEF (0.28 +/- 0.04 vs 0.38 +/- 0.04 in Group 1 and 0.29 +/- 0.04 vs 0.40 +/- 0.06 in Group 2) was found in both groups at follow-up. CONCLUSIONS: In spite of improving early and late survival after revascularization for ischemic left ventricular failure, patients presenting with congestive failure have an unsatisfactory symptom-free survival. Further studies are necessary to ascertain the relative indications to revascularization or transplantation in this specific patient subgroup.  相似文献   
94.
95.
A novel enzyme that catalyzes the disproportionation of chlorite into chloride and oxygen was purified from a gram-negative bacterium, strain GR-1 to homogeneity. A four-step purification procedure comprising Q-Sepharose, hydroxyapatite, and phenyl-Superose chromatography and ultrafiltration resulted in a 13.7-fold purified enzyme with a final specific activity of 2.0 mmol min-1 (mg protein)-1. The dismutase obeyed Michaelis-Menten kinetics. The Vmax and Km calculated for chlorite were 2,200 U (mg protein)-1 and 170 microM, respectively. Dismutase activity was inhibited by hydroxylamine, cyanide, and azide, but not by 3-amino-1,2,4-triazole. Chlorite dismutase had a molecular mass of 140 kDa and consisted of four 32-kDa subunits. The enzyme was red-colored and had a Soret peak at 392 nm. Per subunit, it contained 0.9 molecule of protoheme IX and 0.7 molecule of iron. Chlorite dismutase displayed maxima for activity at pH 6.0 and 30 degrees C.  相似文献   
96.
OBJECTIVE: To analyze the effects of flutamide in patients with physical and/or mental disorders consulting for urinary symptoms secondary to benign prostatic hyperplasia (BPH). METHODS: 50 patients with BPH in whom surgical treatment was contraindicated due to their physical and/or mental condition were treated with flutamide 250 mg/day. Four patients presented with urinary retention and 46 patients had prostatic symptomatology. Patients were evaluated using the symptoms score (I-PSS) and quality of life (QL). Prostate volume was measured by transabdominal US; the maximum flow rate at spontaneous micturition and residual urine were determined. RESULTS: At 12 months, the I-PSS and QL scores decreased by a mean of 7 and 3 points, respectively. The US demonstrated that treatment had reduced prostatic volume by a mean of 10 gms. The maximum flow rate at spontaneous micturition increased 3 ml/sec and residual urine decreased by 15 ml. CONCLUSION: Flutamide is another alternative to surgery in specific patients with BPH.  相似文献   
97.
98.
A light microscopy system has been designed for freezing and lyophilization studies of protein pharmaceuticals. The system consists of a cascade of four Peltier thermoelectric modules in the lyophilization cell to freeze samples to -60 degrees C, controllers to regulate temperature and pressure conditions, and a video camera to record the events under study. Specific demonstration of the system was conducted using recombinant CD4-IgG and human growth hormone (hGH) as model proteins. Observations of recrystallization during warming of frozen CD4-IgG solution and lyophilization of hGH solution are discussed. These examples demonstrate that the system is a useful tool for the fundamental understanding of freezing and lyophilization of protein pharmaceuticals.  相似文献   
99.
BACKGROUND: Osteolipomas are distinguished from other intracranial lipomas by their arrangement of central adipose and peripheral osseous tissues and by characteristically arising in the suprasellar/interpeduncular region. METHODS: We report computed tomography (CT), magnetic resonance imaging (MRI), and pathology findings from this 34-year-old man who underwent surgical removal of this benign lesion. RESULTS: This case displays the distinctive histopathology that has been reported in 13 of 31 (42%) lipomas in this region. In contrast, ossification of lipomas at other intracranial sites is relatively rare. CONCLUSIONS: Ossification should be expected in many suprasellar/interpeduncular lipomas, and osteolipoma should be included in the radiologic differential diagnosis of fat-intensity masses with calcification in this region.  相似文献   
100.
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