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   479篇
  免费   8篇
电工技术   19篇
化学工业   76篇
金属工艺   7篇
机械仪表   11篇
建筑科学   5篇
能源动力   6篇
轻工业   27篇
无线电   90篇
一般工业技术   61篇
冶金工业   155篇
原子能技术   15篇
自动化技术   15篇
  2022年   8篇
  2021年   7篇
  2020年   1篇
  2019年   7篇
  2018年   1篇
  2017年   2篇
  2016年   6篇
  2015年   6篇
  2014年   7篇
  2013年   24篇
  2012年   11篇
  2011年   21篇
  2010年   9篇
  2009年   10篇
  2008年   14篇
  2007年   12篇
  2006年   14篇
  2005年   12篇
  2004年   14篇
  2003年   17篇
  2002年   13篇
  2001年   11篇
  2000年   8篇
  1999年   12篇
  1998年   59篇
  1997年   40篇
  1996年   20篇
  1995年   9篇
  1994年   18篇
  1993年   18篇
  1992年   6篇
  1991年   6篇
  1990年   11篇
  1989年   14篇
  1988年   6篇
  1987年   5篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1983年   3篇
  1982年   1篇
  1981年   5篇
  1980年   2篇
  1978年   1篇
  1977年   3篇
  1976年   2篇
  1974年   1篇
  1973年   1篇
排序方式: 共有487条查询结果,搜索用时 16 毫秒
481.
A novel human T cell line (SALT-3) was established from the pleural effusion of a patient with adult T cell leukemia (ATL) of lymphoma type. SALT-3 showed atypical T cell markers such as CD1-CD2-CD3-CD4+CD5+CD7+CD8-CD19-CD20-CD25+HLA-DR+. T cell receptor alpha/beta and gamma/delta were undetectable. Human T cell lymphotropic virus type 1 (HTLV-I) particles were seen on SALT-3 cells by electron microscopic analysis. HTLV-I gag p19, proviral DNA and mRNA of HTLV-I genes were also detected in the cells. Chromosome analysis showed abnormal karyotypes as 47, XY, partial trisomy of No.3 chromosome, and trisomy of No. 7 chromosome. Furthermore, SALT-3 were susceptible to the infection of human immunodeficiency virus type 1 (HIV-1) and the cells were rapidly killed after HIV-1 infection. This newly established HTLV-I-infected human T cell line would be a useful tool to study biological activities of atypical type of ATL cells and to examine the cytotoxic effects of HIV-1 and it's modulators.  相似文献   
482.
Lipopolysaccharide (LPS) is a potent bone resorbing factor. We investigated the effect of LPS on osteoclast formation in three types of cultures. LPS inhibited osteoclast formation induced by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], in a dose-dependent manner, in cultures of whole bone marrow cells without dexamethasone. LPS increased the amount of granulocyte-macrophage colony stimulating factor (GM-CSF) in the culture supernatant, and anti-GM-CSF antiserum almost abolished the inhibition of osteoclast formation by LPS, thereby indicating that GM-CSF generated by treatment with LPS may be responsible for the inhibition of osteoclast formation. In cultures with dexamethasone, the amount of GM-CSF was decreased to one-third of that with 1,25(OH)2D3 alone and was not changed by treatment with LPS. In this culture system, LPS enhanced osteoclast formation. In the coculture system of nonadherent bone marrow cells and a stromal cell line in the presence of 1,25(OH)2D3 and dexamethasone, where no detectable GM-CSF was present in the supernatant, LPS markedly enhanced osteoclast formation, whereas exogenously added GM-CSF (100 pg/ml) almost completely inhibited osteoclast formation. LPS stimulated pit formation on dentin slices by the osteoclast-like cells formed by in vitro culture system.  相似文献   
483.
The intrinsic or acquired resistance of urothelial cancer to chemotherapy is one major obstacle to successful treatment. Generally, the expression level of P-glycoprotein in urothelial cancer is low, so we accordingly investigated the expression of multidrug resistance-associated protein (MRP). We examined the expression of MRP mRNA by means of slot-blotting samples of 11 renal pelvic and/or ureteral tumors, 33 bladder tumors, one lung metastasis from a ureter tumor, 7 non-cancerous urothelia from patients with transitional-cell carcinoma (TCC) and one urothelium from a patient with renal-cell carcinoma (RCC). We also estimated, by Southern blotting, whether or not the MRP gene was amplified in clinical specimens that overexpressed MRP mRNA. MRP was detected immunohistochemically using a polyclonal antibody against MRP. In all, 5 of 11 renal pelvic and/or ureter tumors (45.5%), 17 of 33 bladder tumors (51.5%) and 4 of 7 non-cancerous urothelia of TCC patients (57.1%) expressed more than 2-fold the MRP mRNA levels of drug-sensitive human KB cells. There was no significant difference in the MRP mRNA level between primary and recurrent tumors. Low-grade urothelial carcinomas (G1 and G2 TCCs) expressed significantly higher levels of MRP mRNA than the high-grade G3 TCC. The MRP gene was not amplified in urothelial carcinomas, irrespective of their expression levels of MRP mRNA. Immunohistochemically, MRP was located mainly on the plasma membrane, but also detected on the cytoplasm of cancer cells. MRP may be one mechanism responsible for intrinsic drug resistance in low-grade urothelial cancer.  相似文献   
484.
The patient was a 20-year-old female who complained of hoarseness and dysphagia. Chest X-ray showed bilateral hilar lymphadenopathy. Sarcoidosis was diagnosed histologically on the basis of granuloma without necrosis, by transbronchial lung biopsy (TBLB). Bronchofiberscopic findings revealed no granuloma of the vocal cords. Examination of the central nervous system with MRI identified no abnormalities. Hoarseness and dysphagia were thought to have been caused by glossopharyngeal and vagus nerve paresis. These signs improved markedly after two weeks of steroid therapy. This is a rare case of sarcoidosis associated with glossopharyngeal & vagus nerve paresis.  相似文献   
485.
A Japanese voxel phantom in upright posture, JM2, has been developed on the basis of CT images of a healthy Japanese adult male. Body characteristics of JM2 were compared with those of the supine voxel phantom, JM, previously developed using CT images of the same person. Differences were found in the shapes of the spine and lower abdomen and the locations of several organs such as kidneys, liver and stomach between the two phantoms. Specific absorbed fractions (SAFs) for 24 target and 11 sources organs were calculated for monoenergetic photon ranging from 0.01 to 4 MeV. It was found that the SAFs for the kidneys as source organ and the lower large intestine wall as target organ in JM2 were significantly higher than those in JM for all photon energies. The differences of the SAFs between the two phantoms were attributed to the differences in the organ distance and organ geometry depending on the posture.  相似文献   
486.
X rays have been widely used for nondestructive analysis of nano-scaled materials for a long time; however, the effects of x-ray radiation have been less extensively discussed. In this work, by means of the in-situ x-ray diffraction and the ex-situ high-resolution electron microscopy, we have quantitatively investigated the x-ray effect on the oxidation behavior of Cu nanoparticles prepared by the vapor condensation method. Clear evidence shows that the x-ray irradiation increases the oxidation thickness as well as the oxidation rate. The results are of critical importance not only for the oxidation studies but also for the nanomaterial researches with x-ray related equipment.  相似文献   
487.
Lithium salts have been widely used in the treatment of mood disorders, but the mechanism of action is still not clear. In this work, a methodology for two-dimensional Lithium-7 imaging on clinical systems is presented. The data were acquired using a phosphorus volume head coil that was re-tuned for the Lithium-7 frequency. A spectroscopic sequence was used to acquire the free induction decay (FID) after volume excitation using a hard pulse. The results obtained on the head of patients undergoing lithium treatment (n = 7, 0.6 mEq/1 average serum level) demonstrate that images of adequate signal to noise ratio (100:1) can be obtained in acceptable imaging times (55 min) using the proposed methodology. The distribution of ’’Li appears uniform in the brains of the patients studied.  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