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   1037篇
  免费   3篇
化学工业   72篇
金属工艺   10篇
机械仪表   7篇
建筑科学   1篇
能源动力   14篇
轻工业   22篇
水利工程   1篇
石油天然气   2篇
无线电   9篇
一般工业技术   13篇
冶金工业   875篇
原子能技术   3篇
自动化技术   11篇
  2018年   3篇
  2016年   4篇
  2014年   4篇
  2013年   6篇
  2012年   14篇
  2011年   5篇
  2009年   7篇
  2007年   6篇
  2006年   5篇
  2005年   4篇
  2003年   4篇
  2001年   7篇
  1999年   27篇
  1998年   244篇
  1997年   144篇
  1996年   112篇
  1995年   56篇
  1994年   49篇
  1993年   64篇
  1992年   9篇
  1991年   9篇
  1990年   13篇
  1989年   15篇
  1988年   9篇
  1987年   18篇
  1986年   10篇
  1985年   16篇
  1983年   3篇
  1982年   7篇
  1981年   4篇
  1980年   8篇
  1979年   3篇
  1978年   2篇
  1977年   26篇
  1976年   63篇
  1975年   4篇
  1973年   2篇
  1955年   2篇
  1946年   2篇
  1944年   2篇
  1943年   2篇
  1941年   2篇
  1940年   2篇
  1939年   2篇
  1938年   2篇
  1937年   4篇
  1936年   2篇
  1935年   2篇
  1934年   3篇
  1926年   2篇
排序方式: 共有1040条查询结果,搜索用时 31 毫秒
61.
WW Arkinstall 《Canadian Metallurgical Quarterly》1997,157(2):133; author reply 133-133; author reply 134
  相似文献   
62.
The ketogenic diet, a treatment for intractable epilepsy, is rarely initiated because it requires strict compliance with a diet that is perceived to be unpalatable. In a case study of a 15-year-old girl with uncontrolled epilepsy, we used a stimulus-choice procedure to assess relative preferences of 33 foods from the diet and to develop two treatments based on Premack's principle. The results of a multielement analysis showed that both treatments increased dietary compliance. Compliance was maintained with generalization of treatment across settings, and was associated with a 40% reduction in seizures.  相似文献   
63.
The spontaneously hypertensive rat (SHR) exhibits a transition from stable compensated left ventricular (LV) hypertrophy to heart failure (HF) at a mean age of 21 months that is characterized by a decrease in alpha-myosin heavy chain (alpha-MHC) gene expression and increases in the expression of the atrial natriuretic factor (ANF), pro-alpha1(III) collagen, and transforming growth factor beta1 (TGF-beta1) genes. We tested the hypotheses that angiotensin-converting enzyme inhibition (ACEI) in SHR would prevent and reverse HF-associated changes in gene expression when administered prior to and after the onset of HF, respectively. We also investigated the effect of ACEI on circulating and cardiac components of the renin-angiotensin system. ACEI (captopril 2 g/L in the drinking water) was initiated at 12, 18, and 21 months of age in SHR without HF and in SHR with HF. Results were compared with those of age-matched normotensive Wistar-Kyoto (WKY) rats, and to untreated SHR with and without evidence of HF. ACEI initiated prior to failure prevented the changes in alpha-MHC, ANF, pro-alpha1(III) collagen, and TGF-beta1 gene expression that are associated with the transition to HF. ACEI initiated after the onset of HF lowered levels of TGF-beta1 mRNA by 50% (P<.05) and elevated levels of alpha-MHC mRNA two- to threefold (P<.05). Circulating levels of renin and angiotensin I were elevated four- to sixfold by ACEI, but surprisingly, plasma levels of angiotensin II were not reduced. ACEI increased LV renin mRNA levels in WKY and SHR by two- to threefold but did not influence LV levels of angiotensinogen mRNA. The results suggest that the anti-HF benefits of ACEI in SHR may be mediated, at least in part, by effects on the expression of specific genes, including those encoding alpha-MHC, ANF, TGF-beta1, pro-alpha1(III) collagen, and renin-angiotensin system components.  相似文献   
64.
Mutations in the tyrosine kinase, Btk, result in a mild immunodeficiency in mice (xid). While B lymphocytes from xid mice do not proliferate to anti-immunoglobulin (Ig), we show here induction of the complete complement of cell cycle regulatory molecules, though the level of induction is about half that detected in normal B cells. Cell cycle analysis reveals that anti-Ig stimulated xid B cells enter S phase, but fail to complete the cell cycle, exhibiting a high rate of apoptosis. This correlated with a decreased ability to induce the anti-apoptosis regulatory protein, Bcl-xL. Ectopic expression of Bcl-xL in xid B cells permitted anti-Ig induced cell cycle progression demonstrating dual requirements for induction of anti-apoptotic proteins plus cell cycle regulatory proteins during antigen receptor mediated proliferation. Furthermore, our results link one of the immunodeficient traits caused by mutant Btk with the failure to properly regulate Bcl-xL.  相似文献   
65.
This study was undertaken to determine the usefulness of magnetic resonance imaging (MRI) in the diagnosis of flexor tendon rupture in patients who had prior surgery. Magnetic resonance imaging scans were performed on 11 digits (16 tendons) with the clinical diagnosis of flexor tendon rupture. Clinical suspicion correlated with MRI and surgical findings. Clinical examination yielded a 60% accuracy in diagnosis. MRI differentiated rupture from adhesions with a 100% accuracy rate. The MRI scan is a valuable tool in diagnosing tendon ruptures and may help reduce the incidence of unnecessary tendon explorations.  相似文献   
66.
The purpose of this study was to develop a substantive grounded theory of courage among middle-aged adults with long-term health concerns. Twenty-five persons from rural and non-metropolitan areas of Central Illinois were selected to participate in this study based on theoretical sampling procedures. Interviews of 1 to 2 hours using openended questions were audiotaped and transcribed verbatim. The data were analysed using grounded theory methods. Courage among middle-aged adults with long-term health concerns was determined to consist of an ongoing progressive-regressive process of becoming and being courageous. Being courageous involves being fully aware of and accepting the threat of a long-term health concern, solving problems using discernment, and developing enhanced sensitivities to personal needs and the world in general. Courageous behaviour consists of taking responsibility and being productive. Courage is not limitless, and the process of becoming and being courageous is dependent on intrapersonal and interpersonal factors. Health-care providers facilitate this process by demonstrating competence and communicating effectively. Outcomes of being courageous include personal integrity and thriving in the midst of normality.  相似文献   
67.
OBJECTIVE AND IMPORTANCE: We report a case of a posterior fossa neuroepithelial tumor with unusual clinical presentation, magnetic resonance imaging appearance, and morphological features. CLINICAL PRESENTATION: This 66-year-old man presented with a history of gait ataxia, dizziness, and tinnitus and was found to have a large tumor in the posterior fossa and cerebellopontine angle. INTERVENTION: Gross total excision of the tumor was accomplished. Histologically, the most unique features were macrovesicular accumulations of lipid, giving the tumor (at least focally) an appearance virtually identical to that of mature adipose tissue. Evidence of biphasic neuronal and glial differentiation was noted by immunohistochemistry and electron microscopy. CONCLUSION: A literature review is presented. Diagnostically, this neoplasm seems to fit in a unique group of rarely described, lipomatous neuroectodermal tumors that show divergent neuronal and glial differentiation.  相似文献   
68.
Eight children with the cyst of choledochus, ageing from 1 month to 15 years, were treated for the period of 20 years in clinic. Cystoduodenostomy is the method of choice for the treatment. All the patients have recovered.  相似文献   
69.
This case report describes the use of a single lateral arm flap sequentially transferred to two defects in a bilateral hand injury. We believe this is a novel approach in reconstructing defects in bilateral hands when a staged reconstruction is planned.  相似文献   
70.
OBJECTIVES: To evaluate the prevalence, clinical and radiological characteristics, association with HLA B27 in a subgroup of patients with inflammatory bowel disease (IBD) and subclinical sacroileitis. The sensitivity of the diagnostic criteria for spondyloarthropathy in this group of patients is evaluated. MATERIALS AND METHODS: All patients with inflammatory bowel disease attending an outpatient gastroenterology unit from January 1994 to June 1994 were recruited. A total of 62 patients with IBD and without clinical evidence of axial involvement were included in the study. The demographic, clinical, and radiological characteristics were collected. The radiological examination included PA and lateral views for the dorso-lumbar, and three views (Ferguson, right and left oblique views) for the sacroiliac joints. Films were interpreted by three independent readers. The HLA B27 allele distribution was analyzed in the 62 patients and in 80 healthy controls. The modified New York criteria, Amor criteria, and European Spondyloarthropathy Study Group criteria were evaluated. Patients were prospectively followed for two years with the same initial protocol. The statistical management of data was performed with the information program SPSS/PC. RESULTS: Fifteen cases of silent sacroileitis were detected, and most of them were grade 2 unilateral sacroileitis. There was no correlation between sacroileitis and IBP type, extradigestive symptoms, disease duration, sex, or peripheral arthritis. The frequency of HLA B27 in the sacroileitis group was 20% (p < 0.05). During the two-year follow-up period none of these cases has changed from diagnostic category. The sensitivity of diagnostic the criteria for spondyloarthropathy was low in these patients (40%-53%). CONCLUSIONS: A high frequency of asymptomatic sacroileitis in patients with IBD was detected. We propose the term Silent Axial Arthropathy to define this category of patients and, as with other authors, we consider this is a third form of rheumatic syndrome in IBD, different from the classical forms of peripheral arthritis and ankylosing spondylitis.  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