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   8861篇
  免费   34篇
  国内免费   4篇
电工技术   23篇
综合类   2篇
化学工业   418篇
金属工艺   43篇
机械仪表   61篇
建筑科学   97篇
矿业工程   4篇
能源动力   66篇
轻工业   195篇
水利工程   8篇
石油天然气   6篇
无线电   182篇
一般工业技术   252篇
冶金工业   7299篇
原子能技术   28篇
自动化技术   215篇
  2021年   17篇
  2020年   16篇
  2018年   24篇
  2017年   21篇
  2016年   12篇
  2015年   15篇
  2014年   23篇
  2013年   129篇
  2012年   52篇
  2011年   59篇
  2010年   62篇
  2009年   52篇
  2008年   41篇
  2007年   61篇
  2006年   72篇
  2005年   51篇
  2004年   44篇
  2003年   58篇
  2002年   35篇
  2001年   52篇
  2000年   53篇
  1999年   261篇
  1998年   2472篇
  1997年   1394篇
  1996年   901篇
  1995年   473篇
  1994年   393篇
  1993年   492篇
  1992年   65篇
  1991年   78篇
  1990年   81篇
  1989年   74篇
  1988年   83篇
  1987年   83篇
  1986年   69篇
  1985年   66篇
  1984年   25篇
  1983年   39篇
  1982年   58篇
  1981年   54篇
  1980年   84篇
  1979年   27篇
  1978年   29篇
  1977年   164篇
  1976年   316篇
  1975年   26篇
  1974年   16篇
  1973年   15篇
  1970年   12篇
  1968年   12篇
排序方式: 共有8899条查询结果,搜索用时 15 毫秒
51.
BACKGROUND: Children with paratesticular rhabdomyosarcoma (RMS) have both a good prognosis and a high survival rate. The clinical behaviour and outcome of the disease in adults is not well described. PATIENTS AND METHODS: We reviewed retrospectively our experience with paratesticular RMS in patients older than 16 years during a 16-year period (1975-1991). RESULTS: Thirteen adult patients with paratesticular RMS are reported. Median age was 21 years (range 16 to 31). Presentation characteristics were scrotal mass in 11 cases, lumbar pain and weight loss in 5 cases, hypercalcemia in 3 cases and thrombocytopenia in 3 cases. There were 5 patients with stage IV, 2 with stage IIB and 6 with stage IA (IRS classification). The 5 stage IV patients are reported in detail, with initial bone marrow infiltration encountered in 4 of them. Objective response to chemotherapy was achieved in all 6 patients with measurable disease (2 CR + 4 PR). Two of 7 patients who received adjuvant chemotherapy relapsed at 7 and 11 months. After a median follow-up of 90 months, 8 patients (5 stage IV, 3 stage IA) died from disease progression. CONCLUSION: Metastatic disease with bone marrow involvement at presentation and aggressive behaviour seem to be more relevant in adult paratesticular RMS patients compared with children.  相似文献   
52.
53.
Ligation of CD95 (APO-1/Fas) cell surface receptors induces death in apoptosis-sensitive cells. Induction of apoptosis in adherent gamma interferon-stimulated HT-29 and COLO 205 colon carcinoma cells by cross-linking CD95 with anti-APO-1 monoclonal antibody resulted in detachment of the cells from hyaluronate starting about 1 h after antibody exposure. Loss of adhesion was paralleled by a substantial reduction of the multifunctional cell surface adhesion molecule CD44. As evidenced by cycloheximide treatment, this effect was not caused by impaired protein synthesis. Depletion of surface CD44 was also not due to membrane blebbing, since cytochalasin B failed to inhibit ascension from hyaluronate. Instead, ELISA and time kinetics showed increasing amounts of soluble CD44 in the supernatant of CD95-triggered cells. SDS-PAGE revealed that soluble CD44 had an apparent molecular mass of about 20 kD less than CD44 immunoprecipitated from intact cells. Thus, CD95-triggering induced shedding of CD44. Shedding is a novel mechanism operative in early steps of CD95-mediated apoptosis. Shedding surface molecules like CD44 might contribute to the active disintegration of dying epithelial cells in vivo.  相似文献   
54.
In single-particle tracking experiments, the diffusion coefficient D may be measured from the trajectory of an individual particle in the cell membrane. The statistical distribution of single-trajectory diffusion coefficients is examined by Monte Carlo calculations. The width of this distribution may be useful as a measure of the heterogeneity of the membrane and as a test of models of hindered diffusion in the membrane. For some models, the distribution of the short-range diffusion coefficient is much narrower than the observed distribution for proteins diffusing in cell membranes. To aid in the analysis of single-particle tracking measurements, the distribution of D is examined for various definitions of D and for various trajectory lengths.  相似文献   
55.
In April 1991, 91 hospitalized patients in Cairo were reported to the Egyptian Ministry of Health with botulism intoxication. To define the spectrum of illness and identify a food vehicle, 45 patients were interviewed and a case-control investigation was conducted among families of 5 hospitalized patients. Clinical specimens and specimens of implicated food were tested for toxin and cultured for Clostridium botulinum. Hospitalized patients had symptoms consistent with botulism; 18 (20%) of 91 reported patients died. Illness was associated with eating faseikh (uneviscerated, salted mullet fish; lower 95% confidence limit of odds ratio = 6.6, P < .001). All 5 case-families purchased faseikh from one shop. Very high levels of type E botulinal toxin were detected in faseikh reported to be purchased from the implicated shop; C. botulinum type E was isolated from cultures of clinical specimens and from the faseikh. This is the first documented outbreak of botulism in Egypt and the largest type E outbreak ever reported.  相似文献   
56.
57.
OBJECTIVES: Antral gastritis is frequent in alcoholics. The role of H. pylori in the pathogenesis of gastritis in these patients is not well known. The aim of our study was to study the role of H. pylori and cirrhosis in the pathogenesis of antral gastritis in alcoholic patients. METHODS: Seventy-nine patients were included in the study. All underwent upper gastrointestinal tract endoscopy with antral biopsies, independently of the presence of abdominal pain, and had serological examination for H. pylori antibodies. RESULTS: Cirrhosis and gastritis were present in 50 and 40 patients respectively, H. pylori serological assay and histological identification of the bacterium were positive in 35 (44%) and 19 (24%) patients respectively. Discrepancy between the 2 tests were observed more frequently in cirrhotic patients. A positive serology with a negative histologic examination for H. pylori was present for 18 cirrhotic and 4 noncirrhotic patients (p < 0.05). A gastritis without evidence of H. pylori was more frequent in cirrhotic than in noncirrhotic patients. H. pylori was histologically present in 11 of 29 cirrhotic patients and in 8 of the 11 noncirrhotic patients with a gastritis (p < 0.05). CONCLUSIONS: Discrepancies between histological examination and H. pylori serology in patients with cirrhosis might be due to the inhospitable environment for H. pylori in case of portal hypertension; the positive serology could be in relation with a past infection.  相似文献   
58.
PURPOSE: To demonstrate a superselective intraarterial chemotherapy as a therapeutic alternative in the treatment of previously treated recurrent lymph node metastases in breast cancer. METHODS: 14 patients with recurrent lymph node metastases in cases of breast cancer were presented to be treated by intraarterial chemotherapy of 25 mg mitoxantrone/m2 over a period of 24 hours. In two patients with superclavicular lymph node involvement an intraarterial therapy could not be carried out because of a vascular connection to the anterior spinal artery. Involved lymph stations could be reached in superselective technique by side branches of the subclavian artery. Heparin coverage was given intravenously. Every patient had had surgery, radiation, systemic chemo- and hormonal therapy before and was now graded as inoperable. Therapy indication was given by local tumour-induced symptoms. RESULTS: In the 12 treated cases complete remission was seen in three, partial remission in 4, a steady state in two and a progressive disease in three. There were no complications or severe side effects. CONCLUSION: Intraarterial chemotherapy is an effective and well tolerated treatment in recurrent lymph node metastases in cases of breast cancer even if conventional therapies can no longer be used.  相似文献   
59.
60.
The author describes a patient who has a successful coronary artery bypass. Six weeks later, after a physical examination of the chest, she had unbearable sharp, stabbing pain around the incision which was not responding to nerve blocks, analgesics, nonsteroidal anti inflammatory agents, and epidural blocks. The pain was responsive to mexilitine and disappeared after three weeks of treatment.  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