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   3513篇
  免费   1篇
电工技术   1篇
化学工业   62篇
金属工艺   14篇
机械仪表   23篇
建筑科学   2篇
矿业工程   18篇
能源动力   2篇
轻工业   6篇
水利工程   15篇
石油天然气   28篇
无线电   9篇
一般工业技术   87篇
冶金工业   3199篇
原子能技术   27篇
自动化技术   21篇
  2022年   7篇
  2020年   6篇
  2018年   10篇
  2017年   6篇
  2016年   9篇
  2015年   5篇
  2014年   5篇
  2013年   7篇
  2012年   8篇
  2011年   12篇
  2010年   11篇
  2009年   6篇
  2008年   10篇
  2007年   9篇
  2006年   8篇
  2004年   9篇
  2003年   8篇
  2002年   4篇
  2001年   8篇
  1999年   72篇
  1998年   928篇
  1997年   545篇
  1996年   396篇
  1995年   243篇
  1994年   166篇
  1993年   186篇
  1992年   26篇
  1991年   38篇
  1990年   31篇
  1989年   33篇
  1988年   34篇
  1987年   22篇
  1986年   22篇
  1985年   26篇
  1984年   5篇
  1983年   8篇
  1982年   21篇
  1981年   32篇
  1980年   37篇
  1979年   13篇
  1978年   11篇
  1977年   137篇
  1976年   268篇
  1975年   12篇
  1973年   5篇
  1972年   6篇
  1971年   4篇
  1969年   4篇
  1965年   4篇
  1964年   4篇
排序方式: 共有3514条查询结果,搜索用时 0 毫秒
71.
72.
A new class of potent, orally active phenyl piperazine-based GH secretagogues have been discovered from attempts to mimic the arrangement of the phenyl substituent in the spiroindanyl piperidine and spiroindoline sulfonamide privileged structures of 4 and 1, respectively. The best of these compounds, 18 (EC50 = 2.8 nM) is nearly as potent as MK-0677 for releasing GH from rat pituitary cells.  相似文献   
73.
T cells infiltrating the iris/ciliary body of Lewis rats with anterior uveitis (AU) that had been induced by myelin basic protein (MBP) immunization were previously found to share surface markers common to the T cells that cause experimental autoimmune encephalomyelitis (EAE). To determine whether these AU-associated T cells are in fact the same as those that infiltrate the central nervous system to cause EAE, we examined TCR V gene expression in T cells infiltrating the anterior chamber in rats with AU. As with EAE, we found a biased expression of Vbeta8.2 and Valpha2 in the iris/ciliary body and, although one would expect an influx of nonspecific inflammatory T cells, these biases were still evident at the peak of AU. An analysis of the TCR Vbeta8.2 and Valpha2 sequences derived from the iris/ciliary body demonstrated the presence of the same complementarity determining region 3 motifs found in MBP-specific T cells that are pathogenic for EAE and found in T cells derived from the central nervous system of rats with EAE. Finally, T cells isolated from the iris/ciliary body of rats with AU were found to proliferate in a specific fashion to MBP Ags. Thus, it appears that MBP-specific T cells are pathogenic for AU as well as EAE in the Lewis rat. In addition, the long-term presence of this highly restricted MBP response in the iris/ciliary body indicates that distinct immunoregulatory mechanisms exist in the environment of the eye. This provides an interesting model with which to address questions pertaining to the nature of T cells infiltrating the eye and their regulation during EAE and other systemic diseases.  相似文献   
74.
75.
76.
Systemic enzymes (wobenzime and wobe-mugos) were approved, that had been prescribed as part of polychemotherapy to 24 patients with malignant lymphomas, who presented with large masses of lymphatic nodes poorly resorbable against the background of polychemotherapy and who were assigned for a high-total dose irradiation, which fact would undoubtedly entail sclerosing of adjacent intact tissues. The use of the enzymes made for the optimum realization of the polychemotherapy effect and permitted avoiding a good many of undesirable side events and complication thereof. The above systemic enzymes are well tolerated by patients; they induce no significant changes in the cellular composition or in blood biochemical indices.  相似文献   
77.
For the specific analysis of the variability of RR intervals of the cardiac rhythm, a method for measuring the instantaneous cardiac rhythm (ICR) represented by a multifractal dynamical model (MDM) has been developed. The advantages of this method, compared to the statistical methods of analysis of the RR intervals used, have been demonstrated. The method allows possible catastrophes of the cardiovascular system to be predicted. Using the data of Holter monitoring and the program system developed, we have plotted ICR curves, an ICR piecewise linear trend, and variability charts for three randomly chosen time intervals. The self-similarity (fractality) of the ICR up to an accuracy of 5% has been shown based on the explicit data. The MDM parameters have been calculated based on the ICR data. The analysis of the dynamics of these parameters has been conducted and their compliance with the status of the patient examined has been studied. The relevance of the ICR examination within MDM is closely related to the necessity of recognizing new markers of adverse cardiovascular episodes. The research performed shows that the results obtained could be taken as a basis for developing a new mathematical method of ICR examination based on Holter monitoring.  相似文献   
78.
We report the purification and characterization of glucose-1-phosphate cytidylyltransferase, the first of five enzymes committed to biosynthesis of CDP-D-abequose from Salmonella enterica strain LT2. The purification was greatly facilitated by using a cloned rfbF gene encoding this enzyme. Pure enzyme was obtained by 64-fold enrichment in three chromatography steps. The NH2-terminal sequence of the purified enzyme was in agreement with the sequence predicted from the nucleotide sequence of the rfbF gene. The SDS-polyacrylamide gel electrophoresis estimated subunit M(r) of 31,000 agrees well with the M(r) of 29,035 calculated from the amino acid composition deduced from the nucleotide sequence of the rfbF gene. The glucose-1-phosphate cytidylyltransferase catalyzes a reversible bimolecular group transfer reaction and steady-state kinetic measurements, including product inhibition patterns, indicate that this reaction proceeds by a "ping-pong" type of mechanism. The Km values for CTP, alpha-D-glucose 1-phosphate, CDP-D-glucose, and pyrophosphate are 0.28, 0.64, 0.11, and 1.89 mM, respectively.  相似文献   
79.
Sensory integration (SI) therapy is a controversial--though popular--treatment for the remediation of motor and academic problems. It has been applied primarily to children with learning disabilities, under the assumption that such children (or at least a subgroup of them) have problems in sensory integration to which some or all of their learning difficulties can be ascribed. The present article critically examines the related issues of whether children with learning disabilities differentially exhibit concomitant problems in sensory integration, and whether such children are helped in any way by means specific to SI therapy. An overview of theoretical contentions and empirical findings pertaining to the first issue is presented, followed by a detailed review of recent studies in the SI therapy research literature, in an effort to resolve the second issue. Results of this critique raise serious doubts as to the validity or utility of SI therapy as an appropriate, indicated treatment for the clinical population in question--and, by extension, for any other groups diagnosed as having "sensory integrative dysfunction." It is concluded that the current fund of research findings may well be sufficient to declare SI therapy not merely an unproven, but a demonstrably ineffective, primary or adjunctive remedial treatment for learning disabilities and other disorders.  相似文献   
80.
Scientific-Research Physical Chemistry Institute. All-Union Scientific-Research Institute of Automatic Machinery. Institute of Nuclear Reactors, Russian Scientific Center "Kurchatovskii institut." Translated from Atomnaya énergiya, Vol. 76, No. 2, pp. 148–151, February, 1994.  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