全文获取类型
收费全文 | 2466篇 |
免费 | 3篇 |
专业分类
综合类 | 1篇 |
化学工业 | 40篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
建筑科学 | 5篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 13篇 |
石油天然气 | 1篇 |
无线电 | 3篇 |
一般工业技术 | 49篇 |
冶金工业 | 2327篇 |
原子能技术 | 3篇 |
自动化技术 | 20篇 |
出版年
2017年 | 2篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2000年 | 3篇 |
1999年 | 82篇 |
1998年 | 777篇 |
1997年 | 398篇 |
1996年 | 257篇 |
1995年 | 152篇 |
1994年 | 111篇 |
1993年 | 146篇 |
1992年 | 25篇 |
1991年 | 32篇 |
1990年 | 37篇 |
1989年 | 33篇 |
1988年 | 35篇 |
1987年 | 44篇 |
1986年 | 30篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 16篇 |
1980年 | 29篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 33篇 |
1976年 | 102篇 |
1975年 | 8篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 4篇 |
1966年 | 1篇 |
1955年 | 1篇 |
1938年 | 1篇 |
1931年 | 1篇 |
1925年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有2469条查询结果,搜索用时 15 毫秒
991.
992.
The Adoption and Safe Families Act of 1997 mandates the development of a system to rate the performance of state child welfare programs. The resulting system, built on broader efforts to measure outcomes for children and families who receive support and services from the child welfare system, will inform perspectives on family foster care in the next century. Drawing on findings from evaluations of recent reform initiatives in Alabama, North Carolina, and Ohio, this article suggests that performance measurement systems must be adaptable to changing circumstances, particularly when improvements in one area can affect standards and expectations in others. 相似文献
993.
P Kopp OK Arseven L Sabacan T Kotlar J Dupuis H Cavaliere CL Santos JL Jameson G Medeiros-Neto 《Canadian Metallurgical Quarterly》1999,84(1):336-341
Pendred's syndrome is an autosomal recessive disease characterized by goiter, impaired iodide organification, and congenital sensorineural deafness. The gene mutated in Pendred's syndrome, PDS (Pendred's syndrome gene), was cloned very recently and encodes the putative sulfate transporter pendrin. Pendred's syndrome may account for up to 10% of the cases with hereditary hearing loss, and pendrin mutations have also been found in a kindred with non-syndromic deafness. In this study, 41 individuals from a large, highly inbred pedigree from Northeastern Brazil were examined for features of Pendred's syndrome. Linkage studies and sequence analysis of the coding region of the PDS gene were performed with DNA from 36 individuals. The index patient, with the classical triad of deafness, positive perchlorate test, and goiter, was found to be homozygous for a deletion of thymidine 279 in exon 3, resulting in a frameshift and a premature stop codon at amino acid 96. This alteration resulted in truncation of the protein in the first transmembrane domain. Two other patients with deafness were found to be homozygous for this mutation; 19 were heterozygous and 14 were homozygous for the wild type allele. Surprisingly, 6 deaf individuals in this kindred were not homozygous for the PDS gene mutation; 3 were heterozygous and 3 were homozygous for the wild type allele, suggesting a probable distinct genetic cause for their deafness. All 3 homozygous individuals for the PDS mutation had goiters. However, goiters were also found in 10 heterozygous individuals and in 6 individuals without the PDS mutation and are most likely caused by iodine deficiency. In conclusion, we identified a novel mutation in the PDS gene causing Pendred's syndrome. The comparison of phenotype and genotype reveals, however, that phenocopies generated by distinct environmental and/or genetic causes are present in this kindred and that the diagnosis of Pendred's syndrome may be difficult without molecular analysis. 相似文献
994.
CL Swaggerty IY Pevzner PJ Ferro TL Crippen MH Kogut 《Canadian Metallurgical Quarterly》2003,32(5):483-488
We recently showed that in vitro heterophil functional efficiency in commercial broiler chickens is genetically controlled and may be a sex-associated trait. To further characterize the genetic mechanism(s) of heterophil functional efficiency, we wanted to determine whether the feathering gene, present on the Z sex chromosome, contributes to heterophil functional efficiency. Heterophils from two pairs of broiler lines were evaluated; each pair contained a fast feather (FF) (lines A and X) and a slow feather (SF) line (lines B and Y). On days 1 and 4 post-hatch, heterophils isolated from two sets of pure line broilers (A and B, and X and Y) were evaluated for their ability to (1) phagocytize Salmonella enteritidis, and (2) exhibit bactericidal activity against S. enteritidis. On days 1 and 4 post-hatch, heterophils isolated from the FF lines were statistically (P < or = 0.02) more proficient at phagocytizing S. enteritidis than heterophils from SF lines. Bactericidal activity was also statistically (p < or = 0.02) greater on day 1 post-hatch in the heterophils isolated from FF lines compared to heterophils isolated from SF lines. These data indicate that the presence of the FF gene locus on the Z sex chromosome contributes to heterophil function and may contribute to the early innate immune competence of a flock. 相似文献
995.
996.
Prostaglandins sensitize some nociceptors to noxious mechanical, thermal and chemical stimuli; however, not all nociceptors are sensitized by prostaglandins. We used cultures of dorsal root ganglion neurons from neonatal rats to determine whether prostaglandins differentially alter the responsiveness of populations of neurons to the chemical stimulus bradykinin. Groups of dorsal root ganglion neurons were defined by size of the cell soma and by the presence of immunoreactivity for substance P. An increase in the concentration of free intracellular Ca2+ was used as an indicator of responsiveness to bradykinin. Pretreatment (5 min) with prostaglandin E2 (100 nM) increased the proportion of intermediate-size neurons (somal areas of 240-320 microns2) that responded to 30 nM bradykinin by two-fold but did not alter the proportion of small-size neurons (somal areas of 160-239 microns2) that responded. Pretreatment with prostaglandin E2 had no effect on the maximum increase in free intracellular Ca2+ evoked by 30 nM bradykinin in either population of neurons, defined by size. Although pretreatment with PGE2 did not increase the proportion of intermediate-size neurons that responded to a lower concentration of bradykinin (3 nM), it did increase the concentration of free intracellular Ca2+ evoked by 3 nM bradykinin. Both results were consistent with a leftward shift in the stimulus-response relationship for bradykinin following pretreatment with PGE2. Small- and intermediate-size neurons that responded to bradykinin also differed in their expression of immunoreactivity for substance P. Furthermore, intermediate-size neurons that expressed immunoreactivity for substance P were more likely to respond to bradykinin after treatment with prostaglandin E2. These results support the hypothesis that prostaglandin E2 sensitizes some normally unresponsive primary afferent neurons to chemical stimuli. One population of neurons which becomes responsive to bradykinin after treatment with prostaglandin E2 can be defined based on cell size, and furthermore, these neurons are likely to express substance P. During inflammation, recruitment of primary afferent neurons that are immunoreactive for substance P would enhance the participation of substance P in central mechanisms that contribute to hyperalgesia. 相似文献
997.
This paper reports on research which examined the use of statistical process control (SPC) in the quality improvement process of a printed circuit board (PCB) manufacturer. The implementation of SPC is discussed along with the difficulties encountered and benefits achieved. The findings indicate that SPC is a tool which can be of considerable assistance in the quality improvement process of PCB manufacture. However, the variety of manufacturing technologies used and the number of interconnecting processes makes the application of SPC more difficult than in other traditional industries. The lessons learned include that the introduction of SPC must not be rushed, that discipline and support from all levels in the organization are crucial to its success, that SPC cannot be used in isolation—it needs the structure of a continuous improvement initiative, and that getting processes in a state of statistical control and capable, and keeping them there, is a difficult task which involves considerable effort and patience. 相似文献
998.
999.
1000.