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   3417篇
  免费   4篇
综合类   1篇
化学工业   19篇
机械仪表   2篇
建筑科学   3篇
轻工业   10篇
无线电   6篇
一般工业技术   8篇
冶金工业   3363篇
自动化技术   9篇
  2020年   1篇
  2017年   1篇
  2016年   1篇
  2014年   3篇
  2012年   4篇
  2011年   2篇
  2009年   1篇
  2008年   2篇
  2007年   5篇
  2006年   2篇
  2005年   3篇
  2004年   1篇
  2003年   8篇
  2002年   3篇
  2001年   3篇
  2000年   1篇
  1999年   127篇
  1998年   1147篇
  1997年   591篇
  1996年   413篇
  1995年   196篇
  1994年   187篇
  1993年   175篇
  1992年   38篇
  1991年   33篇
  1990年   44篇
  1989年   43篇
  1988年   39篇
  1987年   35篇
  1986年   33篇
  1985年   39篇
  1984年   1篇
  1983年   5篇
  1982年   13篇
  1981年   13篇
  1980年   17篇
  1979年   1篇
  1978年   6篇
  1977年   52篇
  1976年   125篇
  1975年   3篇
  1972年   2篇
  1964年   1篇
  1955年   1篇
排序方式: 共有3421条查询结果,搜索用时 15 毫秒
51.
52.
Despite the fact that the neuroleptic drugs have been widely used for more than 40 years, one of their most common side-effects, akathisia, has been relatively neglected. There are still no universally agreed diagnostic criteria for akathisia, particularly chronic akathisia, and in this review article, we discuss the controversies surrounding the voluntary nature of its motor features and the importance of the dysphoric component. We also review the published epidemiological studies to show the great variation in frequency of occurrence. Finally, we discuss the possible neurotransmitters involved in the pathophysiology and treatment of this condition.  相似文献   
53.
54.
55.
A cohort of 39 patients (28 male, 11 female) that had undergone total meniscectomy as adolescents (mean age 16 years) underwent FISP 3D Magnetic Resonance Imaging at a mean follow up of 30 years. The presence of meniscal tissue was assessed by two independent observers blinded to the operation details. The volume of any meniscal tissue present was calculated. A posterior horn remnant was seen in 57% of medial and 45% of lateral meniscectomy cases. The mean volume of an operated medial meniscal remnant was 0.29 mL compared with a mean volume of 1.15 mL for an intact medial meniscus. The mean volume of an operated lateral meniscal remnant was 0.30 mL compared with 1.07 mL for an intact lateral meniscus. We have shown that the incidence of incomplete excision of the posterior horn is more common after total medial meniscectomy, and that at a mean follow up of 30 years there is no convincing in vivo MRI evidence of long-term meniscal regeneration.  相似文献   
56.
57.
58.
59.
Because of concerns among veterans over Agent Orange exposure, the Department of Veterans Affairs (VA) has conducted a series of studies of specific cancers among Vietnam veterans. Lung cancer is the topic of investigation in this report. The VA's Patient Treatment File (PTF) was used to identify 329 Vietnam era veterans with a diagnosis of lung cancer made between 1983 and 1990. The PTF is a computerized hospitalized database of inpatient records, including patients' demographic data, and diagnoses. A record is created for each patient discharged from any one of the VA's Medical Centers. Variables abstracted from the military record include education, race, branch of service, Military Occupational Specialty Code, rank, and units served within Vietnam. Two hundred sixty-nine controls were randomly selected from the PTF file of men hospitalized for a reason other than cancer. A second control group numbering 111 patients with colon cancer was also selected from the PTF file. Data were also gathered on exposure to Agent Orange through the location of each individual ground troop veteran's unit in relation to an area sprayed and the time elapsed since that area was sprayed. The crude odds ratio between service in Vietnam and lung cancer was of borderline significance (odds ratio = 1.39 with 95% confidence interval = 1.01-1.92). The relationship disappeared when the confounder year of birth was considered. We conclude from these data that there is no evidence of increased risk in lung cancer associated with service in Vietnam at this time.  相似文献   
60.
The humoral immune response of neonates to T cell-independent type 2 (TI-2) Ags is markedly defective. We previously demonstrated that multivalent membrane Ig cross-linking, using dextran-conjugated anti-Ig Abs (anti-Ig-dextran), is an in vitro model for membrane Ig-dependent TI-2 induction of Ig secretion. In this work, we demonstrate that highly purified neonatal B cells are intrinsically defective in IgM secretion in response to anti-Ig-dextran and cytokines in vitro, as well as other modes of B cell activation, relative to adult B cells. However, costimulation of anti-Ig-dextran-activated neonatal B cells with either CD40-ligand, a recombinant bacterial lipoprotein, or LPS restores the IgM secretory response of neonatal B cells to adult levels. Analysis of Ig isotype secretion indicates that neonatal B cells have an enhanced capacity to secrete IgE and IgA relative to other Ig isotypes. These data suggest that neonatal B cells are competent to secrete Ig in response to TI-2 Ags if adequate costimuli are provided, and thus may have particular relevance for the design of vaccine strategies in the immunodeficient host. The data also suggest that neonatal B cells are programmed to secrete relatively enhanced amounts of IgE and IgA, which may be relevant for antimicrobial resistance at mucosal surfaces.  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