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   455篇
  免费   29篇
  国内免费   11篇
电工技术   8篇
综合类   1篇
化学工业   126篇
金属工艺   9篇
机械仪表   4篇
建筑科学   10篇
能源动力   20篇
轻工业   64篇
水利工程   3篇
石油天然气   3篇
武器工业   2篇
无线电   52篇
一般工业技术   71篇
冶金工业   56篇
原子能技术   3篇
自动化技术   63篇
  2023年   10篇
  2022年   25篇
  2021年   22篇
  2020年   18篇
  2019年   18篇
  2018年   18篇
  2017年   23篇
  2016年   24篇
  2015年   17篇
  2014年   11篇
  2013年   32篇
  2012年   19篇
  2011年   21篇
  2010年   31篇
  2009年   24篇
  2008年   15篇
  2007年   11篇
  2006年   14篇
  2005年   11篇
  2004年   5篇
  2003年   9篇
  2002年   3篇
  2001年   3篇
  2000年   5篇
  1999年   10篇
  1998年   18篇
  1997年   9篇
  1996年   10篇
  1995年   4篇
  1994年   8篇
  1993年   10篇
  1992年   5篇
  1991年   3篇
  1989年   2篇
  1988年   2篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1983年   3篇
  1982年   3篇
  1980年   2篇
  1978年   2篇
  1976年   2篇
  1975年   2篇
  1970年   1篇
  1968年   1篇
排序方式: 共有495条查询结果,搜索用时 0 毫秒
141.
To be able to diagnose systemic candidiasis (SC) and to predict outcomes in SC patients are still challenging tasks for physicians. Previous proteomic studies suggest that anti-Candida methionine synthase (Met6p) IgG antibodies may be a candidate marker for SC. To evaluate their reliability for diagnosis, prognosis and risk stratification in SC, we developed a generic prototype strategy for their measurement in SC. Receiver-operating-characteristic curve analyses revealed a high diagnostic accuracy for this prototype format, which was slightly better to that for the widely used Western blot assays. Multivariate logistic-regression models showed a positive association between serum anti-Met6p IgG antibody levels and SC risk that was independent from established SC risk factors and other baseline variables. After adjusting for and stratifying according to known prognostic factors, a significant trend toward a lower two-month mortality risk with increasing levels was evidenced in SC patients at presentation. We conclude that these antibodies may be useful in discriminating SC from non-SC patients and determining risk stratification in SC. These may also confer protection against SC and be valuable for the design of future immunotherapies. Furthermore, our prototype format has the potential to make impact on other infectious diseases, cancers, allergies or autoimmune disorders.  相似文献   
142.
The mechanical relaxation in binary, ternary, quaternary, and quitary bulk metallic glasses with widely different glass-forming ability, or the critical cooling rate, has been studied. A single-roller melt-spinning apparatus was used for preparing thin specimens. The internal friction Q−1 and the oscillation frequency f of the specimens were measured using an inverted torsion pendulum with the free decay method. The measurements were performed from room temperature, through the glass transition temperature Tg, up to the crystallization temperature Tx. As the temperature is increased, the background Q−1 increases, and peaks can usually be seen near Tg and Tx. The shear modulus, which is proportional to f2, is changed near the Q−1 peak. The experimental data are presented and overall features of the results are discussed.  相似文献   
143.
Moyamoya arteriopathy (MA) is a rare cerebrovascular disorder characterized by ischemic/hemorrhagic strokes. The pathophysiology is unknown. A deregulation of vasculogenic/angiogenic/inflammatory pathways has been hypothesized as a possible pathophysiological mechanism. Since lipids are implicated in modulating neo-vascularization/angiogenesis and inflammation, their deregulation is potentially involved in MA. Our aim is to evaluate angiogenic/vasculogenic/inflammatory proteins and lipid profile in plasma of MA patients and control subjects (healthy donors HD or subjects with atherosclerotic cerebrovascular disease ACVD). Angiogenic and inflammatory protein levels were measured by ELISA and a complete lipidomic analysis was performed on plasma by mass spectrometry. ELISA showed a significant decrease for MMP-9 released in plasma of MA. The untargeted lipidomic analysis showed a cumulative depletion of lipid asset in plasma of MA as compared to HD. Specifically, a decrease in membrane complex glycosphingolipids peripherally circulating in MA plasma with respect to HD was observed, likely suggestive of cerebral cellular recruitment. The quantitative targeted approach demonstrated an increase in free sphingoid bases, likely associated with a deregulated angiogenesis. Our findings indicate that lipid signature could play a central role in MA and that a detailed biomarker profile may contribute to untangle the complex, and still obscure, pathogenesis of MA.  相似文献   
144.
The chemical modification by melt‐mixing of an EBAGMA terpolymer with LDPE and PET was investigated with the aim to use these EBAGMA/LDPE and EBAGMA/PET blends (in equal weight quantities) as compatibilizer master batches to improve the compatibility of the LDPE/PET system. It is shown that when the EBAGMA terpolymer is melt blended with LDPE, almost 40% of the initial amount of EBAGMA is linked to the LDPE backbone. In contrast, in the case of EBAGMA/PET, FT‐IR spectra indicate the total reactivity between the two components through the reaction of the epoxy group of EBAGMA with the PET terminal groups. SEM analysis shows that both master batches present two well‐interconnected phases.

  相似文献   

145.
Instance selection is becoming more and more relevant due to the huge amount of data that is being constantly produced. However, although current algorithms are useful for fairly large datasets, scaling problems are found when the number of instances is of hundreds of thousands or millions. In the best case, these algorithms are of efficiency O(n 2), n being the number of instances. When we face huge problems, scalability is an issue, and most algorithms are not applicable. This paper presents a divide-and-conquer recursive approach to the problem of instance selection for instance based learning for very large problems. Our method divides the original training set into small subsets where the instance selection algorithm is applied. Then the selected instances are rejoined in a new training set and the same procedure, partitioning and application of an instance selection algorithm, is repeated. In this way, our approach is based on the philosophy of divide-and-conquer applied in a recursive manner. The proposed method is able to match, and even improve, for the case of storage reduction, the results of well-known standard algorithms with a very significant reduction of execution time. An extensive comparison in 30 datasets form the UCI Machine Learning Repository shows the usefulness of our method. Additionally, the method is applied to 5 huge datasets with from 300,000 to more than a million instances, with very good results and fast execution time.  相似文献   
146.
A renotropic factor was partially purified by sequential gel filtration and anion exchanger chromatography from plasma of human kidney transplantation donors and a renal cancer patient after uninephrectomy. This activity increased the rate of [3H]thymidine incorporation into DNA in rat cortical tubules, but not in rat liver cells, within the range of 100-200 ng/ml protein. The renotropic activity was detected between 7 and 12 days after uninephrectomy, and at least in 1 case decreased thereafter. This activity was undetected in gel-filtrated plasma of patients after a nonurological surgical procedure. The potency of this renotropic activity and its elution by gel filtration are similar to those displayed by a renal growth factor activity isolated from uninephrectomized rat plasma, as recently reported.  相似文献   
147.
Recent reports of cancers that produce colony-stimulating factors (CSF) and which are associated with leukocytosis indicate that most are granulocyte CSF-producing tumors. A 71-year-old man with metastatic chest wall tumors from large cell lung cancer with marked leukocytosis and eosinophilia was reported. His maximal leukocyte count was 48300/microliter with 37.5% eosinophils. Granulocyte-macrophage CSF (GM-CSF) activity detected by enzyme-linked immunosorbent assay (ELISA) in serum was 112 pg/ml (normal range < 2.0 pg/ml), but G-CSF was normal. Immunohistochemical detection of GM-CSF protein on a chest wall tumor sample was positive. Irradiation of the chest wall tumor was performed and the leukocyte count decreased temporally. However, he died of respiratory failure due to progressive tumor growth 56 days after admission. Based on these results it appears that autocrine production of GM-CSF is a possible cause of this leukemoid reaction.  相似文献   
148.
The aim of our work was to detect Listeria monocytogenes in raw whole milk from five municipalities of Boyacá-Colombia using real-time PCR. A PCR hybridization probe format was used to analyze the presence of L. monocytogenes, using specific primers to amplify a 149 bp fragment from the metalloprotease gene (mpl). In this study on a total number of 81 samples, 21 gave positive results for L. monocytogenes by real-time PCR and 13 samples were positive by conventional method. These results indicate a high presence of this pathogen in this area of the country and that this method is considerably faster than current standard methods.  相似文献   
149.
A measurement system was designed and established to test the piezoresistive properties of resonant tunneling diodes (RTDs). The current-voltage characteristic shifts of RTD at different stress states were detected. The experimental results demonstrate that the piezoresistive sensitivity of RTD is larger than 1 × 10−8 Pa−1. To accurately represent the piezoresistive properties of RTD, the current-voltage characteristic coherence of the same RTD was tested. According to the experimental results, the largest relative resistance shift of an RTD in the same measurement environment is less than 3%, of which 1% is caused by the testing apparatuses. __________ Translated from Chinese Journal of Semiconductors, 2006, 27(10): 1 789–1 793 [译自: 半导体学报]  相似文献   
150.
Analysis of H-, K- and N-ras genes for point mutations by PCR-SSCP and direct sequencing of 46 oral SCCs that were previously analyzed for p53 mutations revealed that 9 (20%) had point mutations in either the H-ras or the N-ras. A novel mutation at codon 59 (GCC-ACC) of H-ras thus far reported only in v-H-ras of Harvey murine sarcoma virus was observed in a tumor of the cheek. Majority (8/9) of these mutations were observed in H-ras, one in N-ras and none in K-ras. This study indicated that the ras gene mutation was relatively high in oral cancers associated with tobacco chewing and the ras and p53 mutational events seem to be independent and mutually exclusive.  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