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   3381篇
  免费   209篇
  3590篇
  2022年   11篇
  2021年   23篇
  2020年   17篇
  2019年   8篇
  2018年   19篇
  2017年   24篇
  2016年   61篇
  2015年   75篇
  2014年   108篇
  2013年   152篇
  2012年   180篇
  2011年   194篇
  2010年   132篇
  2009年   136篇
  2008年   211篇
  2007年   229篇
  2006年   204篇
  2005年   205篇
  2004年   209篇
  2003年   215篇
  2002年   216篇
  2001年   46篇
  2000年   34篇
  1999年   55篇
  1998年   76篇
  1997年   62篇
  1996年   46篇
  1995年   52篇
  1994年   43篇
  1993年   38篇
  1992年   50篇
  1991年   29篇
  1990年   28篇
  1989年   25篇
  1988年   29篇
  1987年   19篇
  1986年   22篇
  1985年   29篇
  1984年   32篇
  1983年   23篇
  1982年   32篇
  1981年   19篇
  1980年   21篇
  1979年   13篇
  1978年   19篇
  1977年   21篇
  1976年   20篇
  1975年   19篇
  1974年   12篇
  1973年   15篇
排序方式: 共有3590条查询结果,搜索用时 0 毫秒
1.
2.
Previous reports have described antigens that are recognized on human melanoma cells by autologous cytolytic T lymphocytes (CTL). The genes coding for a number of these antigens have been identified. Here we report the cloning of a gene that codes for an antigen recognized by autologous CTL on a human renal carcinoma cell line. This antigen is presented byHLA-B7 and is encoded by a new gene that we have namedRAGE1. No expression ofRAGE1 was found in normal tissues other than retina. RAGE1 expression was found in only one of 57 renal cell carcinoma samples, and also in some sarcomas, infiltrating bladder carcinomas, and melanomas. This represents the first identification of an antigen recognized by autologous CTL on a renal tumor.  相似文献   
3.
Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above the estimated energy cost of body weight maintenance reached 244 ± 9.8 MJ (Mean ± SEM). Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. Mean body weight loss was 5.0 kg (SEM = 0.6) (p <0.001) and it was entirely accounted for by the loss of fat mass (p <0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p <0.001) which represented about 78% of the estimated energy deficit. Subcutaneous fat loss was slightly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomography (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm2 (SEM = 5) to 52 cm2 (SEM = 6) (p <0.001). At the same submaximal power output level, subjects oxidized more lipids than carbohydrates after the program as indicated by the changes in the respiratory exchange ratio (p <0.05). Intrapair resemblance was observed for the changes in body weight (p <0.05), fat mass (P <0.01), percent fat (p <0.01), body energy content (p <0.01), sum of 10 skinfolds (p <0.01), abdominal visceral fat (p <0.01), fasting plasma triglycerides (p <0.05) and cholesterol (p <0.05), maximal oxygen uptake (p <0.05), and respiratory exchange ratio during submaximal work (p <0.01). We conclude that even though there were large individual differences in response to the negative energy balance and exercise protocol, subjects with the same genotype were more alike in responses than subjects with different genotypes particularly for body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during sub-maximal exercise were also seen despite the fact that all subjects had experienced the same exercise and nutritional conditions for about three months.  相似文献   
4.
5.
Purification and Characterization of a Human Brain Galectin-1 Ligand   总被引:2,自引:0,他引:2  
Abstract: Our previous studies have characterized an endogenous lectin from human brain identified as galectin-1. A soluble ligand of galectin-1 was purified from human brain by affinity chromatography and preparative electrophoresis. The purified ligand (termed HBGp82, for human brain galectin-1-binding polypeptide of 82,000 daltons) has an apparent molecular mass of 82 kDa and is glycosylated by N -linked biantennary complex structures. HBGp82 was partially characterized by microsequencing of peptide fragments. Similar peptides were found in a heat shock of protein of 90,000 daltons, hsp90. However, comparison of apparent molecular weights and matrix-assisted laser desorption mass spectrometry clearly showed that HBGp82 differs to some degree from hsp90.  相似文献   
6.
From November 1977 to March 1978 we recorded the scent-marking behaviour of free-ranging coyotes in southern Québec. Fourteen animals were marked by foot-pad ablation, which made it possible to recognize individuals' tracks in the snow and therefore to relate scent-marking with social organization. We observed 949 scent-marks. The identity of the animals was known for 50% of the tracking distances. Animals living in territorial groups (pairs and pairs with juveniles) marked more than twice as much as solitary non-territorial individuals. In addition the former used stronger forms of marking significantly more often than the latter.  相似文献   
7.
8.
9.
Important regions of rRNA are rich in nucleotide modifications that can have strong effects on ribosome biogenesis and translation efficiency. Here, we examine the influence of pseudouridylation and 2′-O-methylation on translation accuracy in yeast, by deleting the corresponding guide snoRNAs. The regions analyzed were: the decoding centre (eight modifications), and two intersubunit bridge domains—the A-site finger and Helix 69 (six and five modifications). Results show that a number of modifications influence accuracy with effects ranging from 0.3- to 2.4-fold of wild-type activity. Blocking subsets of modifications, especially from the decoding region, impairs stop codon termination and reading frame maintenance. Unexpectedly, several Helix 69 mutants possess ribosomes with increased fidelity. Consistent with strong positional and synergistic effects is the finding that single deletions can have a more pronounced phenotype than multiple deficiencies in the same region. Altogether, the results demonstrate that rRNA modifications have significant roles in translation accuracy.  相似文献   
10.
Analysis of total aromatic amino acid (free and bound) in some cucumber accessions selected previously for resistance to western flower thrips, Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae], indicated that low concentrations of these essential nutrients, relative to total leaf protein, were correlated with a reduction in damage by the insect. Further analysis of samples of four important horticultural crops (lettuce, tomato, pepper and cucumber) with unknown levels of resistance to thrips showed a significant genotypic variation in the concentrations of total aromatic amino acids relative to the total leaf protein. Accessions from each crop with low or high concentrations of aromatic amino acids in proteins were exposed to thrips larvae. Regression analysis showed a highly significant positive correlation between aromatic amino acid concentration in leaf protein and thrips damage, regardless of crop species. It is concluded that higher concentrations of aromatic amino acids in plant proteins are important for successful thrips development. These results provide plant breeders with a promising tool for indirect selection without using undesirable insect bioassays.  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