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   3219篇
  免费   13篇
  国内免费   13篇
电工技术   17篇
综合类   12篇
化学工业   36篇
金属工艺   21篇
机械仪表   11篇
建筑科学   12篇
矿业工程   1篇
能源动力   5篇
轻工业   74篇
水利工程   3篇
石油天然气   2篇
无线电   2篇
一般工业技术   40篇
冶金工业   2969篇
自动化技术   40篇
  2023年   2篇
  2022年   10篇
  2021年   9篇
  2020年   5篇
  2019年   4篇
  2018年   3篇
  2017年   4篇
  2015年   11篇
  2014年   6篇
  2013年   43篇
  2012年   23篇
  2011年   16篇
  2010年   14篇
  2009年   20篇
  2008年   14篇
  2007年   11篇
  2006年   6篇
  2005年   9篇
  2004年   4篇
  2003年   11篇
  2001年   2篇
  2000年   2篇
  1999年   98篇
  1998年   930篇
  1997年   563篇
  1996年   349篇
  1995年   171篇
  1994年   143篇
  1993年   206篇
  1992年   25篇
  1991年   12篇
  1990年   21篇
  1989年   17篇
  1988年   20篇
  1987年   18篇
  1986年   18篇
  1985年   20篇
  1983年   9篇
  1982年   14篇
  1981年   20篇
  1980年   26篇
  1979年   2篇
  1978年   11篇
  1977年   94篇
  1976年   208篇
  1975年   7篇
  1973年   2篇
  1964年   1篇
  1955年   4篇
  1954年   1篇
排序方式: 共有3245条查询结果,搜索用时 11 毫秒
61.
62.
PURPOSE: Arteriography is the diagnostic test of choice before lower extremity revascularization, because it is a means of pinpointing stenotic or occluded arteries and defining optimal sites for the origin and termination of bypass grafts. We evaluated whether a duplex ultrasound scan, used as an alternative to arteriography, could be used as a means of accurately predicting the proximal and distal anastomotic sites in patients requiring peripheral bypass grafts and, therefore, replace standard preoperative arteriography. METHODS: Forty-one patients who required infrainguinal bypass grafts underwent preoperative duplex arterial mapping (DAM). Based on these studies, an observer blinded to the operation performed predicted what operation the patient required and the best site for the proximal and distal anastomoses. These predictions were compared with the actual anastomotic sites chosen by the surgeon. RESULTS: Whether a femoropopliteal or an infrapopliteal bypass graft was required was predicted correctly by means of DAM in 37 patients (90%). In addition, both anastomotic sites in 18 of 20 patients (90%) who had femoropopliteal bypass grafts and 5 of 21 patients (24%) who had infrapopliteal procedures were correctly predicted by means of DAM. CONCLUSION: DAM is a reliable means of predicting whether patients will require femoropopliteal or infrapopliteal bypass grafts, and, when a patient requires a femoropopliteal bypass graft, the actual location of both anastomoses can also be accurately predicted. Therefore, DAM appears able to replace conventional preoperative arteriography in most patients found to require femoropopliteal reconstruction. Patients who are predicted by means of DAM to require crural or pedal bypass grafts should still undergo preoperative contrast studies to confirm these results and to more precisely locate the anastomotic sites.  相似文献   
63.
ABSTRACT To study the importance of hydrophobic interaction on the mechanism of acid milk gel formation, milk coagulation process was monitored at 30 °C in presence of various levels of sodium dodecyl sulphate (SDS). As a function of the SDS concentration, acid milk coagulability was either enhanced or reduced. Main pH‐induced biochemical changes were preserved despite the presence of SDS (such as pH‐induced demineralization and pH‐induced protein solubilization). It could be assumed that SDS‐modified casein micelles ability to coagulate by lowering of pH might seem to be governed essentially by the level of SDS‐induced k‐casein micellar dissociation, at natural milk pH.  相似文献   
64.
Results of isolation of glycopeptide-resistant enterococci from fecal samples of pigs and chickens were found to differ strongly depending upon the type and age of animals and isolation technique (direct selective plate or broth enrichment). Isolations were frequent in broiler chickens and in sows but rare in layer chickens.  相似文献   
65.
The effects of bilateral infusions of antisense oligodeoxynucleotides (ODNs) for the two isoforms of glutamic acid decarboxylase (GAD65; GAD67) into the nucleus accumbens on the performance of intact rats in a task designed to assess sustained attention were tested. The task required the animals to discriminate between signal and non-signal events. Signals and non-signals were presented randomly and unpredictably. The task generated all four response types of a sustained attention task, i.e., hits, misses, correct rejections, false alarms. Infusions of the scrambled sequence ODNs did not affect performance. Likewise, infusions of the GAD67 ODNs failed to produce any effect. However, infusions of the GAD65 ODNs into the nucleus accumbens resulted in a robust and reliable decrease in the relative number of hits. Similarly, the combined infusion of GAD65+67 ODNs impaired the hit rate but did not affect the animals' ability to reject non-signals. Following each treatment series, performance rapidly returned to baseline, further indicating the specificity and reversibility of the effects of the infusions of the ODNs. While these data suggest that translation arrest of specifically the GAD65 isoform of the enzyme in the nucleus accumbens impairs attentional performance, the neuronal mechanisms mediating these effects remain unsettled.  相似文献   
66.
67.
Fusion proteins constructed of a tumor-specific Ab joined to IL-2 (Ab-IL-2) have been used in the past to deliver cytokine directly to the site of tumor cells in vivo. These molecules mimic the activity of IL-2 and assist in activating and expanding antitumor effector cells. To enhance the cytolytic activity of CTL specific for peptide epitopes of the Her-2/neu tumor Ag presented by HLA-A*0201 molecules, a fusion protein was constructed consisting of a single chain Ab specific for Her-2/neu, linked to IL-2 (neu-Ab-IL-2). When added to a mixture of tumor cells and Her-2/neu-specific CTL, the protein was found to augment lysis of tumor cells. In addition, the hybrid molecule also promoted lysis of Her-2/neu expressing tumors by non-tumor-specific cloned T cell lines, including Th1 CD4 cells. Analysis of the mechanism of cytotoxicity revealed that the fusion protein mediates the formation of stable conjugates between T cells expressing IL-2R and tumor cells expressing Her-2/neu, resulting in lysis through the Fas-Fas ligand pathway. Lysis induction was independent of specific engagement by the TCR. When tested for its ability to enhance tumor cell eradication by Her-2/neu-specific CD8+ T cells in an adoptive transfer model in SCID mice, neu-Ab-IL-2 facilitated the elimination of tumor cells in vivo. Surprisingly, the combination of non-tumor-specific CD8+ T cells and fusion protein also induced a significant delay of tumor growth. This represents a novel approach for redirecting non-tumor-specific T cells to eliminate tumors.  相似文献   
68.
Although maternal antibodies can protect against infectious disease in infancy, they can also suppress active immune responses. The effects of circulating maternal antibodies, with and without colostrum and milk antibodies, on passive protection and active immunity to human rotavirus (HRV) were examined in gnotobiotic pigs. Pigs received intraperitoneal injections of high-titer serum (immune pigs [groups 1 and 2]) from immunized sows, low-titer serum from naturally infected sows (control pigs [groups 3 and 4]), or no serum (group 5). Immune or control colostrum and milk were added to the diet of groups 2 and 4, respectively. After inoculation (3 to 5 days of age) and challenge (postinoculation day [PID] 21) with virulent HRV, the effects of maternal antibodies on protection (from diarrhea and virus shedding), and on active antibody responses (measured by quantitation of antibody-secreting cells [ASC] in intestinal and systemic lymphoid tissues by ELISPOT) were evaluated. Groups 1 and 2 had significantly less diarrhea and virus shedding after inoculation but higher rates of diarrhea and virus shedding after challenge than did groups 3 and 5. Group 1 and 2 pigs had significantly fewer immunoglobulin A (IgA) ASC in intestinal tissues at PID 21 and at postchallenge day (PCD) 7 compared to group 5. Significantly fewer IgG ASC were present in the intestines of group 2 pigs at PID 21 and PCD 7 compared to group 5. There was a trend towards fewer ASC in intestinal tissues of group 2 than group 1, from PID 21 on, with significantly fewer IgA ASC at PCD 7. IgG ASC in the duodenum and mesenteric lymph nodes of group 3 and 4 pigs were significantly fewer than in group 5 at PCD 7. These decreases in ASC emphasize the role of passive antibodies in impairing induction of ASC rather than in merely suppressing the function of differentiated B cells. To be successful, vaccines intended for populations with high titers of maternal antibodies (infants in developing countries) may require higher titers of virus, multiple doses, or improved delivery systems, such as the use of microencapsulation or immune stimulating complexes, to overcome the suppressive effects of maternal antibodies.  相似文献   
69.
Species-specific nested PCR was used to detect Treponema amylovorum, Treponema denticola, Treponema maltophilum, Treponema medium, Treponema pectinovorum, Treponema socranskii, and Treponema vincentii in dental plaque. Subjects with periodontitis harbored all species, but T. pectinovorum and T. vincentii were not found in plaque from disease-free subjects.  相似文献   
70.
Bicalutamide is a new, nonsteroidal antiandrogen with a favorable toxicity profile. We report the first case of fulminant hepatic failure associated with its use.  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