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   2856篇
  免费   0篇
  国内免费   3篇
综合类   1篇
化学工业   117篇
金属工艺   27篇
机械仪表   1篇
建筑科学   3篇
矿业工程   13篇
能源动力   1篇
轻工业   2篇
水利工程   20篇
石油天然气   76篇
无线电   2篇
一般工业技术   133篇
冶金工业   2418篇
原子能技术   37篇
自动化技术   8篇
  2019年   2篇
  2011年   1篇
  2010年   2篇
  2007年   1篇
  2005年   11篇
  2004年   32篇
  2003年   13篇
  2002年   14篇
  2001年   14篇
  2000年   3篇
  1999年   84篇
  1998年   740篇
  1997年   452篇
  1996年   285篇
  1995年   162篇
  1994年   119篇
  1993年   169篇
  1992年   38篇
  1991年   33篇
  1990年   39篇
  1989年   28篇
  1988年   22篇
  1987年   33篇
  1986年   34篇
  1985年   21篇
  1984年   8篇
  1983年   15篇
  1982年   21篇
  1981年   29篇
  1980年   36篇
  1979年   18篇
  1978年   26篇
  1977年   74篇
  1976年   135篇
  1975年   21篇
  1974年   14篇
  1973年   14篇
  1972年   9篇
  1971年   12篇
  1970年   12篇
  1969年   12篇
  1968年   9篇
  1967年   12篇
  1966年   7篇
  1965年   4篇
  1964年   6篇
  1963年   1篇
  1962年   3篇
  1958年   4篇
  1955年   4篇
排序方式: 共有2859条查询结果,搜索用时 15 毫秒
1.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine.  相似文献   
2.
3.
A genetic linkage map of human chromosome 21q (HC21q) containing 43 markers genotyped by the polymerase chain reaction in the CEPH pedigrees is presented. The markers placed on this map are highly polymorphic with an average heterozygosity of 61%. The average interval size of the markers localized at 1000:1 odds is 2.5 cM. The map has a total length of 65.5 cM, with male and female lengths of 47.7 and 83.3 cM, respectively. The genotypes used in the construction of this map were subjected to rigorous error checking, which is reflected in the shorter map length compared to previous maps; the estimated error rate in genotyping is less than 0.04%. As noted in previous linkage maps there is increased recombination in females on proximal HC 21q and in the male in a region near the telomere. This map of HC 21 represents a highly informative and dense meiotic linkage map and will be useful in linking disease phenotypes to loci on this chromosome.  相似文献   
4.
5.
6.
The crystal structure of [NpO2{OC(NH2)2}5]ClO4·H2O and [NpO2Cl{OC(NH2)2}4] was studied by X-ray diffraction. The electronic absorption spectra of these complexes were recorded. The coordination polyhedron of Np in both complexes is a distorted pentagonal bipyramid. There is no cation-cation interaction of neptunyl cations in these complexes.  相似文献   
7.
The main phase transformations during synthesis of β‐sialon from kaolin of the Prosyanovskii deposit (Ukraine) under test-industrial production conditions have been studied. Sialon was prepared by carbothermal reduction in graphite-tube furnaces in nitrogen. It is shown that the process is characterized by the simultaneous occurrence of several chemical reactions with formation of intermediate phases (Si2ON2, X1‐phase), silicon carbide, and (apart from β‐sialon) sialons based on AlN polytypes. The phase composition of the final product is determined not only by the charge composition but also by the set of production parameters. Results of the work may provide a basis for commercial preparation of sialon powder.  相似文献   
8.
The results of development work on the SVBR-75/100 modular fast reactor cooled by lead–bismuth coolant are presented. The design is based on the experience gained operating reactors in nuclear-powered submarines. The SVBR-75/100 reactor is inherently safe because of its low power, the chemical inertness and high boiling point of the lead–bismuth coolant, and the integrated basin-type arrangement of the first-loop equipment. This eliminates the conflict between the safety and economic requirements that is characteristic of conventional-type reactors. The lower power makes it possible to build the reactor in a factory and deliver the reactor using any form of transportation to the nuclear power plant site. All safety systems operate passively. Most of these systems are used as normal-operating systems. This creates conditions for multipurpose applications of such reactor modules in developed and developing countries.  相似文献   
9.
The design and implementation of clinical trials (CTs) carried out to evaluate antimicrobial and anti-infective drugs and devices are one of the most difficult challenges in contemporary periodontal research and product development. The overwhelming amount of evidence which has established a microbial etiology for periodontitis is the basis for developing and testing antimicrobial treatments. Well-designed antimicrobial CTs start with a carefully crafted hypothesis and a protocol which explicitly integrates the requirements of the patient, the clinician, the sponsor, and regulatory authorities. Surrogate variables for effectiveness must be clinically relevant, scientifically sound, and statistically valid. Currently, clinical attachment level measurements and alveolar bone assessments are accepted as proof of effectiveness. Indication and claim support of the antimicrobial product guide the design and implementation of the CT. Adverse microbiologic consequences, such as lack of antimicrobial susceptibility, wrong spectrum, incorrect dosage, non-compliance, and drug interference, must be monitored. Successful CTs balance a large group of variables used to screen, randomize, and assign subjects to experimental and control groups to ensure that prognostic and risk factors are properly accounted for.  相似文献   
10.
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