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   5068篇
  免费   23篇
  国内免费   1篇
电工技术   15篇
化学工业   131篇
金属工艺   18篇
机械仪表   20篇
建筑科学   17篇
矿业工程   1篇
能源动力   28篇
轻工业   64篇
水利工程   2篇
石油天然气   2篇
无线电   58篇
一般工业技术   92篇
冶金工业   4556篇
原子能技术   4篇
自动化技术   84篇
  2023年   5篇
  2022年   8篇
  2021年   12篇
  2020年   13篇
  2019年   16篇
  2018年   10篇
  2017年   20篇
  2016年   19篇
  2015年   9篇
  2014年   21篇
  2013年   44篇
  2012年   34篇
  2011年   50篇
  2010年   33篇
  2009年   32篇
  2008年   19篇
  2007年   18篇
  2006年   29篇
  2005年   17篇
  2004年   21篇
  2003年   18篇
  2002年   8篇
  2001年   7篇
  2000年   7篇
  1999年   161篇
  1998年   1368篇
  1997年   749篇
  1996年   516篇
  1995年   270篇
  1994年   244篇
  1993年   261篇
  1992年   40篇
  1991年   75篇
  1990年   64篇
  1989年   91篇
  1988年   74篇
  1987年   67篇
  1986年   69篇
  1985年   54篇
  1984年   4篇
  1983年   6篇
  1982年   17篇
  1981年   27篇
  1980年   48篇
  1979年   3篇
  1978年   11篇
  1977年   122篇
  1976年   267篇
  1975年   5篇
  1955年   3篇
排序方式: 共有5092条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
This article is a discussion of the use of narrow-band light sources coupled with cameras equipped with band-pass filters to document patterned injuries on human skin. Several case reports are included.  相似文献   
65.
We have isolated a putative serine/threonine receptor kinase gene with an expression pattern indicating that it may play a role in the stylar response to pollination. Differential display PCR was used to select tobacco mRNAs with increased accumulation following pollination. NTS16, a cDNA identified by this method, is homologous to a ca. 2.4 kb mRNA primarily expressed in pistil tissues. Levels of this mRNA increase during floral development and are further increased by pollination reaching maximal accumulation 12-18 hours after pollination and then declining. mRNA levels can also be increased by the application of ethylene to unpollinated flowers. A polypeptide encoded by the NTS 16 open reading frame has sequence similarity to the catalytic domain of several receptor protein kinases from plants including the S-receptor kinases implicated in the rejection of self-pollen in Brassica species and the Pto gene product of tomato which confers resistance to a bacterial pathogen.  相似文献   
66.
AIMS/BACKGROUND: To characterise clinically a large kindred segregating retinitis pigmentosa and sensorineural hearing impairment in an autosomal dominant pattern and perform genetic linkage studies in this family. Extensive linkage analysis in this family had previously excluded the majority of loci shown to be involved in the aetiologies of RP, some other forms of inherited retinal degeneration, and inherited deafness. METHODS: Members of the family were subjected to detailed ophthalmic and audiological assessment. In addition, some family members underwent skeletal muscle biopsy, electromyography, and electrocardiography. Linkage analysis using anonymous microsatellite markers was performed on DNA samples from all living members of the pedigree. RESULTS: Patients in this kindred have a retinopathy typical of retinitis pigmentosa in addition to a hearing impairment. Those members of the pedigree examined demonstrated a subclinical myopathy, as evidence by abnormal skeletal muscle histology, electromyography, and electrocardiography. LOD scores of Zmax = 3.75 (theta = 0.10), Zmax = 3.41 (theta = 0.10), and Zmax = 3.25 (theta = 0.15) respectively were obtained with the markers D9S118, D9S121, and ASS, located on chromosome 9q34-qter, suggesting that the causative gene in this family may lie on the long arm (q) of chromosome 9. CONCLUSIONS: These data indicate that the gene responsible for the phenotype in this kindred is located on chromosome 9 q. These data, together with evidence that a murine deafness gene is located in a syntenic area of the mouse genome, should direct the research community to consider this area as a candidate region for retinopathy and/or deafness genes.  相似文献   
67.
68.
Four genes on the short arm of human chromosome 19 (HSA 19p) were assigned to bovine chromosome 7 (BTA 7) using a bovine x rodent somatic hybrid cell panel. These four genes were cartilage oligomeric matrix protein (COMP), lymphoblastic leukemia derived sequence 1 (LYL1), lysosomal alpha-mannosidase (MANB), and RAS oncogene family member RAB3A. Bovine sequence tagged sites were developed for the four genes and used for screening a bovine x rodent somatic cell panel. All four genes were mapped to bovine synteny group U22 (BTA 7) with a correlation coefficient of 0.901-1.000. This study confirms that the centromeric region of BTA 7 is conserved with HSA 19p.  相似文献   
69.
70.
The TaqIB cholesteryl ester transfer protein (CETP) gene polymorphism (B1B2) is a determinant of HDL cholesterol in nondiabetic populations. Remarkably, this gene effect appears to be modified by environmental factors. We evaluated the effect of this polymorphism on HDL cholesterol levels and on the lipoprotein response to a linoleic acid-enriched, low-cholesterol diet in patients with type 1 diabetes. In 44 consecutive type 1 diabetic patients (35 men), CETP polymorphism, apolipoprotein (apo) E genotype, serum lipoproteins, serum CETP activity (measured with an exogenous substrate assay, n = 30), clinical variables, and a diet history were documented. The 1-year response to diet was assessed in 14 type 1 diabetic patients, including 6 B1B1 and 6 B1B2 individuals. HDL cholesterol was higher in 10 B2B2 than in 14 B1B1 homozygotes (1.63 +/- 0.38 vs. 1.24 +/- 0.23 mmol/l, P < 0.01). HDL cholesterol, adjusted for triglycerides and smoking, was 0.19 mmol/l higher for each B2 allele present. CETP activity levels were not significantly different between CETP genotypes. Multiple regression analysis showed that VLDL + LDL cholesterol was associated with dietary polyunsaturated:saturated fatty acids ratio (P < 0.02) and total fat intake (P < 0.05) in the B1B1 homozygotes only and tended to be related to the presence of the apo E4 allele (P < 0.10). In response to diet, VLDL + LDL cholesterol fell (P < 0.05) and HDL cholesterol remained unchanged in 6 B1B1 homozygotes. In contrast, VLDL + LDL cholesterol was unaltered and HDL cholesterol decreased (P < 0.05) in 6 B1B2 heterozygotes (P < 0.05 for difference in change in VLDL + LDL/HDL cholesterol ratio). This difference in response was unrelated to the apo E genotype. Thus, the TaqIB CETP gene polymorphism is a strong determinant of HDL cholesterol in type 1 diabetes. This gene effect is unlikely to be explained by a major influence on the serum level of CETP activity, as an indirect measure of CETP mass. Our preliminary data suggest that this polymorphism may be a marker of the lipoprotein response to dietary intervention.  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