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   1410篇
  免费   85篇
电工技术   25篇
化学工业   351篇
金属工艺   19篇
机械仪表   31篇
建筑科学   50篇
矿业工程   1篇
能源动力   30篇
轻工业   143篇
水利工程   7篇
石油天然气   5篇
武器工业   1篇
无线电   164篇
一般工业技术   221篇
冶金工业   143篇
原子能技术   8篇
自动化技术   296篇
  2023年   7篇
  2022年   57篇
  2021年   59篇
  2020年   36篇
  2019年   37篇
  2018年   41篇
  2017年   23篇
  2016年   53篇
  2015年   49篇
  2014年   43篇
  2013年   88篇
  2012年   75篇
  2011年   99篇
  2010年   61篇
  2009年   75篇
  2008年   54篇
  2007年   62篇
  2006年   55篇
  2005年   50篇
  2004年   40篇
  2003年   42篇
  2002年   36篇
  2001年   28篇
  2000年   20篇
  1999年   23篇
  1998年   40篇
  1997年   28篇
  1996年   25篇
  1995年   23篇
  1994年   24篇
  1993年   10篇
  1992年   11篇
  1991年   6篇
  1990年   4篇
  1989年   12篇
  1988年   9篇
  1987年   3篇
  1986年   7篇
  1985年   11篇
  1984年   10篇
  1983年   7篇
  1982年   6篇
  1981年   8篇
  1980年   4篇
  1979年   6篇
  1978年   4篇
  1977年   3篇
  1976年   8篇
  1975年   3篇
  1974年   3篇
排序方式: 共有1495条查询结果,搜索用时 71 毫秒
161.
BACKGROUND: End-stage liver disease due to hepatitis C virus (HCV) is the most common indication for liver transplantation in U.S. veterans. We investigated the influence of HCV genotypes on the incidence and timing of recurrent HCV hepatitis, survival, infectious morbidity, and response to interferon-alpha therapy in this unique patient population. METHODS: HCV genotype was determined by direct sequencing of the NS5 region of HCV with type-specific primers. RESULTS: Genotype 1a (66%, 32/47) was the predominant genotype. Type 1b was found in 25% (12/47) of patients and type 2b was found in 9% (4/47). Histopathologically recurrent HCV hepatitis developed in 53% (25/47) of the patients after transplantation. This group included 45% (14/31) of the patients with type 1a, 67% (8/12) of the patients with type 1b, and 25% (1/4) of the patients with type 2b (P>0.5). The time to recurrence and the severity of HCV recurrence as defined by aminotransferase levels or Knodell scores were not different among the three genotypes. There was a trend toward a higher incidence of major infections in patients with type 1b (75%) versus type 1a (48%) and type 2b (50%) (P=0.11). The response to interferon-a therapy did not differ significantly among the genotypes. Mortality at 5 years was 16% (5/31) in patients with genotype 1a, 42% (5/12) in patients with genotype 1b, and 50% (2/4) in patients with genotype 2b (P=0.06). CONCLUSIONS: The incidence, time to recurrence, and response to interferon-alpha therapy did not differ between the various genotypes in our liver transplant recipients. However, there was a trend toward higher infectious morbidity and overall mortality in patients with genotype 1b after transplantation.  相似文献   
162.
Rate Monotonic vs. EDF: Judgment Day   总被引:13,自引:2,他引:11  
Since the first results published in 1973 by Liu and Layland on the Rate Monotonic (RM) and Earliest Deadline First (EDF) algorithms, a lot of progress has been made in the schedulability analysis of periodic task sets. Unfortunately, many misconceptions still exist about the properties of these two scheduling methods, which usually tend to favor RM more than EDF. Typical wrong statements often heard in technical conferences and even in research papers claim that RM is easier to analyze than EDF, it introduces less runtime overhead, it is more predictable in overload conditions, and causes less jitter in task execution.Since the above statements are either wrong, or not precise, it is time to clarify these issues in a systematic fashion, because the use of EDF allows a better exploitation of the available resources and significantly improves system's performance.This paper compares RM against EDF under several aspects, using existing theoretical results, specific simulation experiments, or simple counterexamples to show that many common beliefs are either false or only restricted to specific situations.  相似文献   
163.
164.
PURPOSE: To verify tolerance and clinical efficacy of high-dose chemotherapy (HDCT) in metastatic breast cancer (MBC). PATIENTS AND METHODS: We submitted to HDCT with autologous peripheral blood cells transplant 66 patients, with MBC responding to induction chemotherapy. The condizioning regimen was ICE: iphosphamide 3.3 g/m2 dd. -8/-6, carboplatin 450 mg/m2 plus etoposide 400 mg/m2 dd. -5/-3 (21 patients = 78%); CTM: cyclophosphamide 100 mg/kg dd. -4/-3, tyothepa 500 mg:m2 d.-5, mytoxantrone 40 mg/m2 d. -6 (6 patients, 22%). RESULTS: Median number of aphereses was 2 (range 1-5), median amount of CD34+ cells/kg bw of 10 x 10E6 (range 3.5-38.2). Median recovery time was 10th day for PMN (range 8-37) while for platelets it was 9th day (range 8-37): total hospital stay was of 24 days (range 22-48). After induction therapy we had PR in 13/27 metastatic patients (48%) and CR in 14/27 (52%). After conditioning treatment we had PR in 12/27 (44%) and CR in 15/27 (56%). Median time to progression was 19 months (range 7-38) and median survival 52 months (range 7-59+), with 30% surviving beyond 4 years. CONCLUSIONS: Feasibility of HDCT in advanced breast cancer seems verified. The promising results need to be confirmed.  相似文献   
165.
Replies to comments by 7 authors (see records 2001-18772-008, 2001-18772-009, 2001-18772-010, 2001-18772-011, and 2001-18772-012) in reference to the F. Rothbaum et al's original article (see record 2000-02781-001), which highlighted evidence of cultural variations in, and noted ways in which attachment theory is laden with Western values and meaning in comparisons of the US and Japan. Here, Rothbaum et al defend their central thesis and note areas of their agreement and disagreement with the aforementioned comments and criticisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
166.
A model has been applied to release of plasticizers from polymer films through vapor phase, for which the overall rate of release may be generally determined by evaporation of the plasticizer from the surface of the film, and/or by migration to the surface at below saturation in the polymer. The experimental system employed made use of n-butyl formate, diethyl-phthalate, di-n-butylphthalate, and N,n-butylbenzenesulfonamide as model molecules in polycaprolactam films, both with the aims of studying undesirable loss of plasticizers, and of simulating a model able to envisage releasing, at a constant rate, of any desired additive, with relatively high solubility and vapor pressure, to the content of packaging films. Experimental measurements were made (at 298–333 K) by investigating in a suitable cell the permeation of plasticizers both at concentrations below and above the saturation limit. Rate of evaporation of plasticizers from the membrane surface above the saturation limit, measured in this cell, were found to coincide satisfactorily with those calculated by application of the mass transfer theory to evaporation from a stationary liquid into a stirred gas, at a known velocity of gas flowing past the surface. From these latter rates and solubilities, the mass transfer coefficients H for evaporation could be obtained, as well as from experimental time lags the diffusivities Dp through the polymer membrane. In the light of the theoretical model a correlation was found between activation energies of H and evaporation enthalpies of the model molecules.  相似文献   
167.
168.
The potentialities for 1-aryl-5-methyl-3-hydroxypyrazoles as intermediates in the field of dyes have been analysed. Some azoic derivatives have been synthesized and both electronic spectra and tinctorial properties on various substrates (wool, nylon, polyester, plasticized PVC) examined. The effect of substituents on the position of the long wavelength absorption maxima is discussed in terms of Hammett σ constants and interesting relationships are obtained. For each application the most important technical properties are assessed and significant fastness to various agents is evaluated.Finally a comparison with properties of similar pyrazol-5-one derivatives is made.  相似文献   
169.
170.
Summary An investigation of the distribution of the cyclic oligomers of poly(lactic acid), formed both by pyrolysis of the polymer and by equilibration with a catalyst, has been performed by Negative Chemical Ionization and Thermospray Mass Spectrometry.The results indicate that the two methods can be used to obtain information on the relative amounts of the oligomers present in the mixture.  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