首页 | 官方网站   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   1007篇
  免费   34篇
  国内免费   4篇
工业技术   1045篇
  2024年   2篇
  2023年   7篇
  2022年   66篇
  2021年   81篇
  2020年   22篇
  2019年   27篇
  2018年   28篇
  2017年   28篇
  2016年   46篇
  2015年   32篇
  2014年   44篇
  2013年   74篇
  2012年   64篇
  2011年   67篇
  2010年   44篇
  2009年   43篇
  2008年   43篇
  2007年   39篇
  2006年   29篇
  2005年   28篇
  2004年   27篇
  2003年   16篇
  2002年   24篇
  2001年   7篇
  2000年   8篇
  1999年   10篇
  1998年   9篇
  1997年   14篇
  1996年   14篇
  1995年   6篇
  1994年   7篇
  1993年   8篇
  1992年   4篇
  1991年   6篇
  1990年   6篇
  1989年   3篇
  1988年   1篇
  1987年   6篇
  1986年   3篇
  1985年   10篇
  1984年   9篇
  1983年   5篇
  1982年   11篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1977年   5篇
  1976年   4篇
  1971年   1篇
排序方式: 共有1045条查询结果,搜索用时 0 毫秒
51.
A group of 37 patients--20 (54%) men and 17 (46%) women--aged 2-65, mean 31.6 years, was treated between 1978 and 1995 for different kinds of primary mediastinal germ cell tumours. In 14 (37.8%) of them a mature solid teratoma was diagnosed, in 13 (35.1%)--dermoid cyst, in 5 (13.5%)--malignant teratoma, in 1 (2.7%)--immature teratoma, in 4 (10.8%)--seminoma. Mediastinal tumour was removed completely in 30 (81.1%) patients, partially in 7 (18.9%). Out of 37 patients, 3 (8.1%) died during postoperative time. Out of 26 patients discharged after surgical removal of mature teratomas, all are alive and have been followed-up for 10 years (17 patients) or 5 years (6 patients). Out of 8 discharged after surgical removal of malignant neoplasm, 3 are alive and all of them had primary mediastinal seminoma. One of them has survived 17 years after complete resection, and two patients--7.5 years and 2 years after partial resection and radiotherapy. Mean survival time is 4 years and 2 months for all patients with malignant neoplasm.  相似文献   
52.
The occurrence of a data flow anomaly is often an indication of the existence of a programming error. The detection of such anomalies can be used for detecting errors and to upgrade software quality. This paper introduces a new, efficient algorithm capable of detecting anomalous data flow patterns in a program represented by a graph. The algorithm based on static analysis scans the paths entering and leaving each node of the graph to reveal anomalous data action combinations. An algorithm implementing this type of approach was proposed by Fosdick and Osterweil [2]. Our approach presents a general framework which not only fillls a gap in the previous algorithm, but also provides time and space improvements.  相似文献   
53.
Results of calculations are presented, which are concerned with applications of the heuristic linear reinforcement systems to the control of pebble-bed HTRs with the OTTO-loading scheme. Control results of three types of systems applications are presented and discussed. The systems were found to be satisfactory for control of the complex physical plants.  相似文献   
54.
Butyltins (BTs) and phenyltins (PhTs) were determined in the livers of marine mammals found by-caught or stranded along the Polish coast of the Baltic Sea. During the investigation an original analytical method was developed. Butyltin compounds were detected in all the liver samples, whereas phenyltins were not detected in any of the samples. The total concentrations of BTs ranged from 43.9 to 7698 ng(Sn) x g(-1) dry weight. Age-related trends to accumulate BTs in immature porpoises were found. At the same time there were no male-female differences in BTs concentrations observed. No statistically significant spatial distribution differences were found between the locations corresponding to the open Baltic Sea waters and inside the Gulf of Gdańsk, which is characterized by high maritime activity. In comparison to butyltin levels in marine mammals from other geographic regions, the samples analyzed indicate a significant degree of tributyltin pollution along the Polish coast of the Baltic Sea. On the basis of a literature review, higher BT levels are usually found in waters close to highly industrialized areas, such as Japan, Hong Kong, and the United States.  相似文献   
55.
One of the greatest disadvantages of the weighted signal averaging method is its sensitivity to the presence of noise and outliers in data and the need to estimate the noise variance in all signal cycles. The robust weighted averaging method based on the epsilon-insensitive loss function is free of these disadvantages, but has a very high computational burden and requires a choice of the insensitivity parameter epsilon. In this study, a new computationally effective algorithm for robust weighted averaging with automatic adjustment of the insensitivity parameter is introduced.  相似文献   
56.
Protein phosphorylation is one of the most important known posttranslational modifications. Tandem mass spectrometry has become an important tool for mapping out the phosphorylation sites. However, when a peptide generated from the enzymatic or chemical digestion of a phosphoprotein is highly phosphorylated or contains many potential phosphorylation residues, phosphorylation site assignment becomes difficult. Separation and enrichment of phosphopeptides from a digest mixture is desirable and often a critical step for MS/MS-based site determination. In this work, we present a novel open tubular immobilized metal ion affinity chromatography (OT-IMAC) method, which is found to be more effective and reproducible for phosphopeptide enrichment, compared to a commonly used commercial product, Ziptip from Millipore. A strategy based on a combination of OT-IMAC, sequential dual-enzyme digestion, and matrix-assisted laser desorption/ionization (MALDI) quadrupole time-of-flight tandem mass spectrometry for phosphoprotein characterization is presented. It is shown that MALDI MS/MS with collision-induced dissociation can be very effective in generating fragment ion spectra containing rich structural information, which enables the identification of phosphorylation sites even from highly phosphorylated peptides. The applicability of this method for real world applications is demonstrated in the characterization and identification of phosphorylation sites of a Na(+)/H(+) exchanger fusion protein, His182, which was phosphorylated in vitro using the kinase Erk2.  相似文献   
57.
Stramski D  Piskozub J 《Applied optics》2003,42(18):3634-3646
We present an approach based on three-dimensional Monte Carlo radiative transfer simulations for estimating scattering error in measurements of light absorption by aquatic particles with a typical laboratory double-beam spectrophotometer. The scattering error is calculated by combining the weighting function describing the angular distribution of photon losses that are due to scattering on suspended particles with the volume scattering function of particles. We applied this method to absorption measurements made on marine phytoplankton, a diatom Thalassiosira pseudonana and a cyanobacterium Synechococcus. Assuming that the scattering phase function is described by the Henyey-Greenstein formula, we determined the backscatter probability of phytoplankton, which yields the best correction for scattering error at a light wavelength of 750 nm, where true absorption is null. The backscattering ratio estimated for both phytoplankton species is significantly higher than previously reported data based on Mie-scattering calculations for homogeneous spheres. Depending on the type of particles, the corrected absorption spectra obtained with our method may be similar or significantly different from spectra obtained with the null-point correction based on wavelength-independent scattering error.  相似文献   
58.
Branch-price-and-cut has proven to be a powerful method for solving integer programming problems. It combines decomposition techniques with the generation of both columns and valid inequalities and relies on strong bounds to guide the search in the branch-and-bound tree. In this paper, we present how to improve the performance of a branch-price-and-cut method by using the primal-dual interior point algorithm. We discuss in detail how to deal with the challenges of using the interior point algorithm with the core components of the branch-price-and-cut method. The effort to overcome the difficulties pays off in a number of advantageous features offered by the new approach. We present the computational results of solving well-known instances of the vehicle routing problem with time windows, a challenging integer programming problem. The results indicate that the proposed approach delivers the best overall performance when compared with a similar branch-price-and-cut method which is based on the simplex algorithm.  相似文献   
59.
The aim of our study was to estimate the surface expressions of CD95 (APO-1/Fas) antigen and the intracellular expressions of anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax in CD4(+)CD25(+)FoxP3(+) T regulatory lymphocytes (Tregs) as well as the percentage of CD8(+)CD28(+) T cytotoxic cells in peripheral blood of patients with pre-eclampsia in comparison with healthy pregnant women in the third trimester of physiological pregnancy. Twenty-four women with pre-eclampsia and 20 normal third trimester pregnant women were included in the study. The lymphocytes were isolated from peripheral blood samples and labeled with monoclonal antibodies. The expressions of surface antigens and intracellular proteins were estimated using flow cytometry. The population of CD4(+)CD25(+)FoxP3(+) Treg cells was significantly lower in peripheral blood of patients with pre-eclampsia when compared to normal third trimester pregnant women. The percentages of CD4(+)CD25(+)FoxP3(+) Treg cells that express Bcl-2 protein were significantly lower in peripheral blood of patients with pre-eclampsia when compared to healthy pregnant women, whereas the percentages of CD4(+)CD25(+)FoxP3(+) Treg cells with the expressions of Bax protein did not differ in both groups. Moreover, the mean fluorescence intensity (MFI) of Bcl-2 protein in CD4(+)CD25(+)FoxP3(+) Treg cells was significantly lower and MFI of Bax protein significantly higher in pre-eclampsia when compared to the control group. The percentage of CD8(+)CD28(+) T cells did not differ in both studied groups but MFI of CD28 antigen on T CD8(+) cells was significantly higher in pre-eclampsia when compared to the control group. The obtained results suggest that the deficit of CD4(+)CD25(+)FoxP3(+) Treg lymphocytes which is observed in pre-eclampsia may be associated with altered apoptosis signaling in Tregs.  相似文献   
60.
Potential catalysts for the partial oxidation of methane to methanol have been synthesised and tested in high pressure annular reactors. Uranium oxide and molybdenum oxide catalysts and iron sodalite catalyst have been tested under the conditions reported in the patents and under conditions which allow comparison with reactions carried out in the gas phase. None of the catalysts tested showed an improvement on the gas phase results. It was found that the oxidative nature of the metal oxide catalysts is an inherent feature which reduces the selectivity to methanol.  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-23

京公网安备 11010802026262号