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   1022篇
  免费   1篇
电工技术   2篇
化学工业   17篇
金属工艺   8篇
机械仪表   6篇
建筑科学   1篇
能源动力   1篇
轻工业   1篇
水利工程   1篇
石油天然气   11篇
无线电   4篇
一般工业技术   62篇
冶金工业   898篇
原子能技术   9篇
自动化技术   2篇
  2021年   3篇
  2019年   2篇
  2018年   5篇
  2017年   7篇
  2016年   3篇
  2014年   3篇
  2013年   7篇
  2012年   3篇
  2011年   9篇
  2010年   6篇
  2009年   12篇
  2008年   8篇
  2007年   4篇
  2006年   9篇
  2005年   4篇
  2004年   5篇
  2003年   3篇
  2002年   5篇
  2001年   6篇
  2000年   3篇
  1999年   9篇
  1998年   272篇
  1997年   144篇
  1996年   112篇
  1995年   71篇
  1994年   48篇
  1993年   58篇
  1992年   12篇
  1991年   22篇
  1990年   18篇
  1989年   7篇
  1988年   5篇
  1987年   7篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1982年   8篇
  1981年   6篇
  1980年   9篇
  1978年   4篇
  1977年   25篇
  1976年   40篇
  1975年   3篇
  1974年   2篇
  1972年   3篇
  1971年   5篇
  1970年   3篇
  1968年   3篇
  1967年   2篇
  1964年   2篇
排序方式: 共有1023条查询结果,搜索用时 15 毫秒
151.
Complex evaluation of environmental state requires processing of extensive information describing various components and objects of environment. Characteristic of this information is territory fix--each environmental object has definite geographic position and border. The authors discuss effects of up-to-date geographic information technologies on evaluation of environmental state in Bashkortostan Republic. Examples of analysis and simulation of possible changes in environmental state are given.  相似文献   
152.
The current environment in which medicine is taught and practiced requires that medical schools pay increased attention to the faculty member's roles, rewards, career development, and productivity. Medical schools must make strategic decisions about the allocation of resources that can nurture their faculties and support the activities in academic and community settings in which faculty are involved. From 1993 to 1995 Allegheny University of the Health Sciences (formerly Medical College of Pennsylvania and Hahnemann University) designed a comprehensive system for the professional development of faculty. This system is based upon expanded categories of faculty academic activity and scholarship. New programs were implemented to reorient faculty toward conducting and documenting the expanded array of scholarly activities. The main characteristics of the new system are the establishment of formally defined performance expectations, the vertical alignment of the individual faculty member's objectives with the department's mission and the school's mission, and an increasing emphasis upon faculty interdependence, accountability, and use of sound business practices. The authors describe these and other aspects of the design of the new system in detail and report initial results and lessons learned from the system's implementation, evaluation, and dissemination throughout the university. The long-term success of this comprehensive professional development program will be assessed over time by observing how this institution advances its mission in a well-planned and cost-effective manner that retains talented, productive, and professionally fulfilled faculty.  相似文献   
153.
154.
For the problem of bending of a plate under the action of a concentrated force represented as pressure distributed over a small surface, we obtain a solution by methods of the moment theory of elasticity, the principal statements of which were given in Part 1. Moscow State Institute of Food Industry, Moscow, Russia. Translated from Problemy Prochnosti, No. 4, pp. 106–115, July–August, 1998.  相似文献   
155.
The role of a marker mutation and other genes in a decrease in viability was studied in the Drosophila melanogaster vg line. In flies of the C-S line, chromosome 2 was substituted by the homologous chromosome of the vg flies. In addition, the flies of the mutant phenotype with mutant genes partially or completely substituted by the wild-type C-S genes were obtained in saturating crosses C-S x vg. In the reciprocal variant of chromosome 2 substitution, the flies of the C-S phenotype with chromosomes 1, 3, and 4 from the vg line were obtained. Chromosome 2 of the vg line, introduced into C-S fly karyotype, proved to substantially reduce the heat resistance and life span of flies. In the case of reciprocal replacement (C-S line chromosome 2 substituted for the homologous chromosome of vg flies), a significant increase in viability was observed, which, however, never reached the level characteristic of the C-S line. As the vg genotype became saturated with C-S genes, the heat resistance and life span of flies increased substantially. However, even the complete saturation of mutant chromosomes with wild-type genes never resulted in the equal viability of vg and C-S flies. These data suggest that the low viability of the vg mutant is largely accounted for by the gene composition of the second chromosome and, primarily, by the presence of the vg gene. Nevertheless, there is evidence that, along with the pleiotropic effect of the marker mutation, other genes not linked to chromosome 2 are responsible for the studied physiological properties of the vg flies.  相似文献   
156.
The adenoid tissue is an immunecompetent lymphoid organ, which has the capacity of reacting against numerous antigens. We have studied the influence that the elimination of the said tissue would have on the total IgE serum levels in 33 patients of an average age of 5 and criteria of adenoidectomy and in whom these levels were measured before and after surgery. We have not noticed any statistically significant differences in the IgE values after adenoidectomy with respect to those prior to surgery, which were normal. Adenoidectomy, like other authors have observed after tonsillectomy, does not alter the IgE serum values.  相似文献   
157.
An allozyme variation of loci-encoding lactate dehydrogenase was compared in different vertebrate classes. A lower level of heterozygosity in warm-blooded as compared to cold-blooded vertebrates was shown. The highest heterozygosity was revealed in anurous and caudate amphibians; the lowest, in birds and mammals. Fishes and reptiles exhibited an intermediate level of heterozygosity. In higher groups of vertebrates, differences in the electrophoretic mobilities between alleles decreased. A key aspect of this is a hiatus of these differences in fishes and mammals. On the basis of this analysis, the following conclusions may be drawn: (1) the rate of amino-acid substitutions in homologous proteins is unequal in distant phylogenetic lineages; (2) the level of heterozygosity is related to the average amount of electrophoretic allelic differences at the class level; (3) significant differences in variation pattern in the phylogenetic lineage of vertebrates is probably associated with the evolutionary features of the genomic organization of groups at different evolutionary levels.  相似文献   
158.
We treated nine patients of mycoplasmal pneumonia with sparfloxacin (SPFX) the clinical efficacy, safety and usefulness of SPFX were evaluated. SPFX was administered orally at doses of 200 or 300 mg once daily, and we performed bronchoalveolar lavage (BAL) examinations in five patients. BAL was performed 5 hours after oral administration of 100 mg in one case, 19 hours after oral administration of 200 mg in four cases. Concentrations of SPFX and alubumine were measured in serum and in BALF (bronchoalveolar lavage fluid). The following results were obtained. 1. Nine patients were evaluated; eight patients judged as Good, one patient as Excellent. 2. The serum and BALF levels of SPFX was 0.79 microgram/ml, 0.107 microgram/ml 5 hours after single oral administration of 100 mg in one case and 19 hours after oral administration of 200 mg in four cases, those of levels of SPFX were 0.835 +/- 0.274 microgram/ml and 0.081 +/- 0.033 microgram/ml, respectively. 3. The ratio of SPFX/albumin in BALF was significantly higher than in the serum. From these results, we consider that SPFX is a useful antimicrobial agent for mycoplasmal pneumonia.  相似文献   
159.
Increased osteoclast activity is responsible for the enhanced bone destruction in postmenopausal osteoporosis, Paget's disease, bone metastasis, and hypercalcemia of malignancy. However, the number of known inhibitory factors that block osteoclast formation and bone resorption are limited. Therefore, we used an expression-cloning approach to identify novel factors produced by osteoclasts that inhibit osteoclast activity. A candidate clone was identified and isolated from a human osteoclast-like multinucleated cell (MNC) cDNA library, named osteoclast inhibitory peptide-1 (OIP-1), and the cDNA sequence was determined. This sequence matched that of the recently identified human stem cell antigen, was structurally similar to the mouse Ly-6 gene family, and the sequence predicted it was a glycosyl phosphatidyl inositol (GPI)-anchored protein that had a cleavable COOH-terminal peptide. Western blot analysis of conditioned media from 293 cells transfected with the OIP-1 cDNA clone confirmed that OIP-1 was released into the media as a membrane-bound GPI-linked protein. Interestingly, both recombinant OIP-1 expressed in Escherichia coli (which does not have GPI linker) and OIP-1 expressed by mammalian cells significantly reduced osteoclast-like MNC formation induced by 1,25-dihydroxyvitamin D3 or PTH-related protein in mouse and human bone marrow cultures, and inhibited 45Ca release from prelabeled bone in fetal rat organ cultures. In contrast, recombinant OIP-1 did not inhibit the growth of a variety of other cell types. These data indicate that OIP-1 is a novel, specific inhibitor of osteoclast formation and bone resorption.  相似文献   
160.
PURPOSE: To determine differences in temperature for very low birth weight (VLBW) infants when swaddled and unswaddled in heated, double-walled incubators. DESIGN: A crossover design was used with infants receiving both the swaddled and unswaddled conditions. SAMPLE: 15 very low birth weight infants (< 1,500 gms) with postconceptional ages of 29.1 +/- 1.5 weeks. MAIN OUTCOME VARIABLE: Infant temperature in swaddled and unswaddled conditions. RESULTS: Abdominal temperatures during swaddling were 0.2 degree C higher than the unswaddled condition. In the swaddled condition, infants required a lower incubator temperature (mean = 26.9 +/- 0.4) than when unswaddled (mean = 29.8 +/- 0.5).  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