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   2624篇
  免费   87篇
  国内免费   1篇
电工技术   45篇
综合类   4篇
化学工业   454篇
金属工艺   31篇
机械仪表   39篇
建筑科学   87篇
矿业工程   4篇
能源动力   49篇
轻工业   219篇
水利工程   18篇
石油天然气   5篇
无线电   357篇
一般工业技术   384篇
冶金工业   479篇
原子能技术   18篇
自动化技术   519篇
  2021年   38篇
  2020年   20篇
  2019年   27篇
  2018年   34篇
  2017年   49篇
  2016年   51篇
  2015年   50篇
  2014年   68篇
  2013年   121篇
  2012年   114篇
  2011年   131篇
  2010年   101篇
  2009年   112篇
  2008年   128篇
  2007年   106篇
  2006年   118篇
  2005年   101篇
  2004年   97篇
  2003年   90篇
  2002年   69篇
  2001年   46篇
  2000年   50篇
  1999年   58篇
  1998年   118篇
  1997年   66篇
  1996年   74篇
  1995年   50篇
  1994年   41篇
  1993年   46篇
  1992年   32篇
  1991年   26篇
  1990年   26篇
  1989年   18篇
  1988年   28篇
  1987年   33篇
  1986年   27篇
  1985年   29篇
  1984年   26篇
  1983年   21篇
  1982年   24篇
  1981年   27篇
  1980年   21篇
  1979年   20篇
  1978年   10篇
  1977年   19篇
  1976年   33篇
  1975年   14篇
  1974年   16篇
  1973年   17篇
  1972年   12篇
排序方式: 共有2712条查询结果,搜索用时 31 毫秒
31.
An advanced integral-type pressurized water reactor (IPWR) with a maximum thermal power of 65 MW has been developed at the Korea Atomic Energy Research Institute (KAERI). This 65 MW IPWR enhances the safety and reliability by adopting inherent safety design characteristics and an advanced passive design feature.  相似文献   
32.
33.
34.
The purpose of the present study was to determine the genetic control of baseline breathing pattern by examining the mode of inheritance between two inbred murine strains with differential breathing characteristics. Specifically, the rapid, shallow phenotype of the C57BL/6J (B6) strain is consistently distinct from the slow, deep phenotype of the C3H/HeJ (C3) strain. The response distributions of segregant and nonsegregant progeny were compared with the two progenitor strains to determine the mode of inheritance for each ventilatory characteristic. The BXH recombinant inbred (RI) strains derived from the B6 and C3 progenitors were examined to establish strain distribution patterns for each ventilatory trait. To establish the mode of inheritance, baseline breathing frequency (f), tidal volume, and inspiratory time (TI) were measured five times in each of 178 mature male animals from the two progenitor strains and their progeny by using whole body plethysmography. With respect to f and TI, the two progenitor strains were consistently distinct, and segregation analyses of the inheritance pattern suggest that the most parsimonious genetic model for response distributions of f and TI is a two-loci model. In similar experiments conducted on 82 mature male animals from 12 BXH RI strains, each parental phenotype was represented by one or more of the RI strains. Intermediate phenotypes emerged to confirm the likelihood that parental strain differences in f and TI were determined by more than one locus. Taken together, these studies suggest that the phenotypic difference in baseline respiratory timing between male B6 and C3 mice is best explained by a genetic model that considers at least two loci as major determinants.  相似文献   
35.
36.
A meta-analysis was performed on 18 studies in which a cognitive–behavioral therapy was compared with the same therapy supplemented by hypnosis. The results indicated that the addition of hypnosis substantially enhanced treatment outcome, so that the average client receiving cognitive–behavioral hypnotherapy showed greater improvement than at least 70% of clients receiving nonhypnotic treatment. Effects seemed particularly pronounced for treatments of obesity, especially at long-term follow-up, indicating that unlike those in nonhypnotic treatment, clients to whom hypnotic inductions had been administered continued to lose weight after treatment ended. These results were particularly striking because of the few procedural differences between the hypnotic and nonhypnotic treatments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
37.
38.
Carbamoyl-phosphate synthetase (CPSase) consists of a 120-kDa synthetase domain (CPS) that makes carbamoyl phosphate from ATP, bicarbonate, and ammonia usually produced by a separate glutaminase domain. CPS is composed of two subdomains, CPS.A and CPS.B. Although CPS.A and CPS.B have specialized functions in intact CPSase, the separately cloned subdomains can catalyze carbamoyl phosphate synthesis. This report describes the construction of a 58-kDa chimeric CPSase composed of Escherichia coli CPS.A catalytic subdomains and the mammalian regulatory subdomain. The catalytic parameters are similar to those of the E. coli enzyme, but the activity is regulated by the mammalian effectors and protein kinase A phosphorylation. The chimera has a single site that binds phosphoribosyl 5'-pyrophosphate (PRPP) with a dissociation constant of 25 microM. The dissociation constant for UTP of 0.23 mM was inferred from its effect on PRPP binding. Thus, the regulatory subdomain is an exchangeable ligand binding module that can control both CPS.A and CPS.B domains, and the pathway for allosteric signal transmission is identical in E. coli and mammalian CPSase. A deletion mutant that truncates the polypeptide within a postulated regulatory sequence is as active as the parent chimera but is insensitive to effectors. PRPP and UTP bind to the mutant, suggesting that the carboxyl half of the subdomain is essential for transmitting the allosteric signal but not for ligand binding.  相似文献   
39.
Criteria for detection of chromosome aberrations by Comparative Genomic Hybridization (CGH) are not standardized and improvement of this part of the analysis is of paramount importance to the applicability of the technique. The aim of this work was to suggest CGH detection criteria that increase the specificity and sensitivity and at the same time include chromosome regions previously excluded from CGH analysis. We analyzed 33 hybridizations with normal DNA and modified our CGH software in order to use a selection of these normal analyses as a model for interpretation of analyses of unknown samples. This approach was successfully tested on 14 samples with known aberrations.  相似文献   
40.
Excessive brain iron has been found in several neurodegenerative diseases. However, little information is available about mechanism of iron uptake by different types of brain cells including neurons. In this study, transferrin-bound iron (Tf-Fe) accumulation in the cultured cerebellar granule cell was investigated in vitro. After 5 days of culture, the cells were incubated with 1 microM of double-labelled transferrin (1251-Tf-59Fe) at 37 degrees C for 60 min. The cellular Tf-Fe and transferrin (Tf) uptake was analysed. The result showed (1) Tf uptake by the cells increased rapidly at the first 5 min, reaching its maximum after about 20 min of incubation; (2) Tf-Fe uptake kept increasing in a linear manner during the whole period of incubation; (3) the addition of either NH4Cl or CH3NH2, the blockers of Tf-Fe uptake via inhibiting iron release from Tf within endosomes, decreased the cellular Tf-Fe uptake but had no significant effect on Tf uptake; (4) trypsin and unlabelled Tf-Fe inhibited the uptake rate of Tf-Fe as well as Tf. The results suggested that Tf-Fe transport across the membrane of this type of neuron, much like other mammalian cells, was mediated by Tf-TfR endocytosis. Dysfunction of Tf or TfR would possibly lead to iron irregulation in the brain and consequently cause damage to neuronal functions.  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