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   1963篇
  免费   65篇
  国内免费   1篇
电工技术   10篇
综合类   1篇
化学工业   198篇
金属工艺   11篇
机械仪表   40篇
建筑科学   27篇
矿业工程   3篇
能源动力   22篇
轻工业   126篇
水利工程   16篇
石油天然气   6篇
无线电   45篇
一般工业技术   217篇
冶金工业   1229篇
原子能技术   13篇
自动化技术   65篇
  2023年   7篇
  2022年   23篇
  2021年   32篇
  2020年   24篇
  2019年   31篇
  2018年   31篇
  2017年   49篇
  2016年   34篇
  2015年   28篇
  2014年   33篇
  2013年   49篇
  2012年   60篇
  2011年   60篇
  2010年   65篇
  2009年   43篇
  2008年   36篇
  2007年   35篇
  2006年   32篇
  2005年   29篇
  2004年   29篇
  2003年   25篇
  2002年   11篇
  2001年   12篇
  2000年   9篇
  1999年   44篇
  1998年   368篇
  1997年   221篇
  1996年   126篇
  1995年   65篇
  1994年   60篇
  1993年   60篇
  1992年   17篇
  1991年   16篇
  1990年   14篇
  1989年   23篇
  1988年   17篇
  1987年   16篇
  1986年   18篇
  1985年   18篇
  1983年   3篇
  1982年   8篇
  1981年   12篇
  1980年   18篇
  1978年   8篇
  1977年   26篇
  1976年   74篇
  1975年   5篇
  1970年   1篇
  1965年   1篇
  1954年   1篇
排序方式: 共有2029条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Experimental glomerulonephritis was induced in rats to investigate the consequence of the antigen-antibody interaction on the surface of glomerular endothelial cells (GENs). A lectin, Lens culinaris hemoagglutinin (LCH), was first planted in the left kidney by isolated perfusion of a left kidney, and then the circulation was reestablished. Rabbit anti-LCH antibodies were injected from the tail vein 3 minutes after the recirculation of the left kidney, and acute glomerulonephritis ensued. Fifteen minutes after the injection, rabbit immunoglobulin G (IgG), rat C3, and LCH were observed exclusively on the surface of GENs. Accumulation of platelets was prominent. Three hours later, the immune deposits were seen in the subendothelial space, and the polymorphonuclear cells were the dominant infiltrate in the glomeruli. Up to the seventh day, immune deposits were seen in the subendothelial space, and the widening of this area was increasingly observed. Fourteen days later, immune deposits containing rat IgG were observed in the subepithelial area, but they were only occasionally seen in the subendothelial space and in the mesangial area. No crescent formation was seen at day 14, but the mesangial area was expanded, with an increased number of cells. The number of nuclei in the cross-section of a glomerulus increased after the induction of glomerulonephritis, but the number of leukocyte common antigen-positive cells (infiltrating cells) decreased gradually from day 4 to day 14. The staining of Thy-1.1, a marker of mesangial cell, was markedly enlarged in the glomerulus at day 14. These data suggest that mesangial proliferative glomerulonephritis can be induced by the antigen-antibody interaction on the surface of GENs.  相似文献   
5.
During the last decade, episodes of sepsis have increased and Escherichia coli has remained the most frequent clinical isolate. Lipopolysaccharides (LPS; endotoxin) are the major toxic and antigenic components of gram-negative bacteria and qualify as targets for therapeutic interventions. Molecules that neutralize the toxic effects of LPS are actively investigated. In this paper, we describe a murine monoclonal antibody (MAb; WN1 222-5), broadly cross-reactive and cross-protective for smooth (S)-form and rough (R)-form LPS. As shown in enzyme-linked immunosorbent assay and the passive hemolysis assay, WN1 222-5 binds to the five known E. coli core chemotypes, to Salmonella core, and to S-form LPS having these core structures. In immunoblots, it is shown to react with both the nonsubstituted core LPS and with LPS carrying O-side chains, indicating the exposure of the epitope in both S-form and R-form LPS. This MAb of the immunoglobulin G2a class is not lipid A reactive but binds to E. coli J5, an RcP+ mutant which carries an inner core structure common to many members of the family Enterobacteriaceae. Phosphate groups present in the inner core contribute to the epitope but are not essential for the binding of WN1 222-5 to complete core LPS. Cross-reactivity for clinical bacterial isolates is broad. WN1 222-5 binds to all E. coli clinical isolates tested so far (79 blood isolates, 80 urinary isolates, and 21 fecal isolates) and to some Citrobacter, Enterobacter, and Klebsiella isolates. This pattern of reactivity indicates that its binding epitope is widespread among members of the Enterobacteriaceae. WN1 222-5 exhibits biologically relevant activities. In vitro, it inhibits the Limulus amoebocyte lysate assay activity of S-form and R-form LPS in a dose-dependent manner and it neutralizes the LPS-induced release of clinically relevant monokines (interleukin 6 and tumor necrosis factor). In vivo, WN1 222-5 blocks endotoxin-induced pyrogenicity in rabbits and lethality in galactosamine-sensitized mice. The discovery of WN1 222-5 settles the long-lasting controversy over the existence of anti-core LPS MAbs with both cross-reactive and cross-protective activity, opening new possibilities for the immunotherapy of sepsis caused by gram-negative bacteria.  相似文献   
6.
Urogenital aging is a complex of urogenital symptoms involving the lower urinary tract, the genital tract and the pelvic floor. These symptoms involve hypoestrogenism in the menopausal woman. This review concludes that irritative urinary and local vaginal symptoms are quite amenable to estrogen therapy. Urinary incontinence is thought to be benefited by treatment with estrogen, although controversy exists. There is a limited role for estrogen in problems of urogenital prolapse, rectal symptoms, and sexuality in menopause.  相似文献   
7.
Our previous receiver operating characteristic (ROC) study indicated that the detection accuracy of microcalcifications by radiologists is significantly reduced if mammograms are digitized at 0.1 mm x 0.1 mm. Our recent study also showed that detection accuracy by computer decreases as the pixel size increases from 0.035 mm x 0.035 mm. It is evident that very large matrix sizes have to be used for digitizing mammograms in order to preserve the information in the image. Efficient compression techniques will be needed to facilitate communication and archiving of digital mammograms. In this study, we evaluated two compression techniques: full frame discrete cosine transform (DCT) with entropy coding and Laplacian pyramid hierarchical coding (LPHC). The dependence of their efficiency on the compression parameters was investigated. The techniques were compared in terms of the trade-off between the bit rate and the detection accuracy of subtle microcalcifications by an automated detection algorithm. The mean-square errors in the reconstructed images were determined and the visual quality of the error images was examined. It was found that with the LPHC method, the highest compression ratio achieved without a significant degradation in the detectability was 3.6:1. The full frame DCT method with entropy coding provided a higher compression efficiency of 9.6:1 at comparable detection accuracy. The mean-square errors did not correlate with the detection accuracy of the microcalcifications. This study demonstrated the importance of determining the quality of the decompressed images by the specific requirements of the task for which the decompressed images are to be used. Further investigation is needed for selection of optimal compression technique for digital mammograms.  相似文献   
8.
This study reports the cellular localization of interferon-gamma (IFN-gamma) and MHC class II antigen (Ia) in the spinal cord of rats with experimental autoimmune encephalomyelitis induced by adoptive transfer of myelin basic protein-specific T cells. Numerous IFN-gamma-positive cells, stained with two different monoclonal antibodies against IFN-gamma, were present from days 3 to 7 after cell transfer. Their number was greatly reduced on day 10. A subpopulation of T cells was IFN-gamma positive. Moreover, a large number of ED1-positive macrophages contained IFN-gamma immunoreactivity. The transient presence of immune cells containing IFN-gamma immunoreactivity in experimental autoimmune encephalomyelitis suggests a pathogenic role of this cytokine in immune-mediated demyelination of the central nervous system.  相似文献   
9.
Mother–daughter dyads from incestuous vs nonclinical families were compared in terms of (1) family life stress, (2) problem-solving appraisal, (3) direct coping behaviors, (4) mother–daughter communication, and (5) family adaptation and cohesion. 15 mother–daughter pairs from an incestuous family involving an adult male caretaker were matched on several variables to 16 mother–daughter pairs from a nonclinical family. The results revealed that mothers from the incest group (compared with the nonclinical group) reported greater amounts of family life stress, had more negative perceptions of their problem-solving appraisal, and reported more communication difficulties. The daughters from the incest group appeared to be quite similar to the nonclinical group daughters, although they did acknowledge more family stress. Implications of the results for therapeutic interventions as well as future research were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
BACKGROUND: The influence of tumor and patient characteristics on survival as well as acute normal tissue toxicity was retrospectively analyzed. PATIENTS AND METHODS: 427 patients with inoperable non-small cell lung cancer were retrospectively analyzed. Two thirds received a total dose of at least 70 Gy, and one third was irradiated with 60 to 66 Gy (2.0 to 2.5 Gy per fraction; split-course technique). 92% had a Karnofsky performance index of > or = 80%. Kaplan-Meier survival curves were generated and comparisons were made by the log-rank test. Prognostic factors were adjusted for by a proportional hazards analysis. RESULTS: Five-year survival rates (+/- SE) and the median survival times (95% confidence interval) were 2 +/- 2% and 11.1 months (9.1 ... 14.5) after 60 to 66 Gy; 8 +/- 2% and 14.9 months (13.3 ... 16.5) after 70+ Gy. The difference was significant in univariate (p = 0.0013) and multivariate analysis (p = 0.0006). Tumor stage (p = 0.0029: I + II > III; IIIA > IIIB) and gender (p = 0.0387: female > male patients) reached significance in multivariate analysis. Acute pneumonitis and esophagitis were observed in 11% and 9% of cases. CONCLUSIONS: Inoperable non-small cell lung cancer stage I to IIIA should be treated in a curative intention with total doses of about 70 Gy. This is feasible with acceptable normal tissue toxicity. Stage IIIB patients have a particular bad prognosis and should only be treated palliatively.  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