全文获取类型
收费全文 | 4956篇 |
免费 | 323篇 |
国内免费 | 387篇 |
专业分类
5666篇 |
出版年
2024年 | 6篇 |
2023年 | 74篇 |
2022年 | 168篇 |
2021年 | 257篇 |
2020年 | 164篇 |
2019年 | 205篇 |
2018年 | 196篇 |
2017年 | 156篇 |
2016年 | 212篇 |
2015年 | 284篇 |
2014年 | 367篇 |
2013年 | 388篇 |
2012年 | 441篇 |
2011年 | 378篇 |
2010年 | 248篇 |
2009年 | 227篇 |
2008年 | 257篇 |
2007年 | 180篇 |
2006年 | 172篇 |
2005年 | 165篇 |
2004年 | 156篇 |
2003年 | 155篇 |
2002年 | 106篇 |
2001年 | 118篇 |
2000年 | 83篇 |
1999年 | 97篇 |
1998年 | 46篇 |
1997年 | 33篇 |
1996年 | 37篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 19篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 31篇 |
1989年 | 8篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 6篇 |
1974年 | 3篇 |
排序方式: 共有5666条查询结果,搜索用时 0 毫秒
121.
Venkatachalam TK Sudbeck EA Mao C Uckun FM 《Bioorganic & medicinal chemistry letters》2001,11(4):523-528
122.
The in vitro chaperone-like activity of Mycobacterium tuberculosis small heat shock protein Hsp16.3 was found to be dramatically enhanced to the same extent after preheat treatment at or over 60 degrees C. Structural analysis using gel filtration, native pore-gradient PAGE, nondenaturing PAGE, and far-UV CD spectroscopy consistently revealed no significant difference between the native and the preheated Hsp16.3 proteins. However, near-UV CD spectroscopy clearly demonstrated that the tertiary structure of preheated Hsp16.3 is quite similar to its native conformation, with a minor but significant difference. Further analysis using differential scanning calorimetry indicated that Hsp16.3 exhibited a structural transition near 60 degrees C. All these results together indicate that Hsp16.3 suffers a phase change at approximately 60 degrees C, which seem to remove a structural energy barrier for the protein to refold to a conformational status with increased chaperone-like activity. 相似文献
123.
124.
Mao W Fukuoka S Iwai C Liu J Sharma VK Sheu SS Fu M Liang CS 《American journal of physiology. Heart and circulatory physiology》2007,293(3):H1636-H1645
Evidence suggests that the autoimmune cardiomyopathy produced by a peptide corresponding to the sequence of the second extracellular loop of the beta(1)-adrenergic receptor (beta(1)-EC(II)) is mediated via a biologically active anti-beta(1)-EC(II) antibody, but the mechanism linking the antibody to myocyte apoptosis and cardiac dysfunction has not been well elucidated. Since the beta(1)-EC(II) autoantibody is a partial beta(1)-agonist, we speculate that the cardiomyopathy is produced by the beta(1)-receptor-mediated stimulation of the CaMKII-p38 MAPK-ATF6 signaling pathway and endoplasmic reticulum (ER) stress, and that excess norepinephrine (NE) exaggerates the cardiomyopathy. Rabbits were randomized to receive beta(1)-EC(II) immunization, sham immunization, NE pellet, or beta(1)-EC(II) immunization plus NE pellet for 6 mo. Heart function was measured by echocardiography and catheterization. Myocyte apoptosis was determined by terminal deoxytransferase-mediated dUTP nick-end labeling and caspase-3 activity, whereas CaMKII, MAPK family (JNK, p38, ERK), and ER stress signals (ATF6, GRP78, CHOP, caspase-12) were measured by Western blot, immunohistochemistry, and kinase activity assay. beta(1)-EC(II) immunization produced progressive LV dilation, systolic dysfunction, and myocyte apoptosis. These changes were associated with activation of GRP78 and CHOP and increased cleavage of caspase-12, as well as increased CaMKII activity, increased phosphorylation of p38 MAPK, and nucleus translocation of cleaved ATF6. NE pellet produced additive effects. In addition, KN-93 and SB 203580 abolished the induction of ER stress and cell apoptosis produced by the beta(1)-EC(II) antibody in cultured neonatal cardiomyocytes. Thus ER stress occurs in autoimmune cardiomyopathy induced by beta(1)-EC(II) peptide, and this is enhanced by increased NE and caused by activation of the beta(1)-adrenergic receptor-coupled CaMKII, p38 MAPK, and ATF6 pathway. 相似文献
125.
Background
Biological networks characterize the interactions of biomolecules at a systems-level. One important property of biological networks is the modular structure, in which nodes are densely connected with each other, but between which there are only sparse connections. In this report, we attempted to find the relationship between the network topology and formation of modular structure by comparing gene co-expression networks with random networks. The organization of gene functional modules was also investigated. 相似文献126.
Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China 总被引:2,自引:0,他引:2
Yuze Mao Hongsheng Yang Yi Zhou Naihao Ye Jianguang Fang 《Journal of applied phycology》2009,21(6):649-656
In this study the red alga, Gracilaria lemaneiformis, was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 3 weeks at the Marine Aquaculture Laboratory of the Institute
of Oceanology, Chinese Academy of Sciences (IOCAS) in Qingdao, Shandong Province, North China. The nutrient uptake rate and
nutrient reduction efficiency of ammonium and phosphorus from scallop excretion were determined. The experiment included four
treatments each with three replicates, and three scallop monoculture systems served as the control. Scallop density (407.9 ± 2.84 g
m−3) remained the same in all treatments while seaweed density differed. The seaweed density was set at four levels (treatments
1, 2, 3, 4) with thallus wet weight of 69.3 ± 3.21, 139.1 ± 3.80, 263.5 ± 6.83, and 347.6 ± 6.30 g m−3, respectively. There were no significant differences in the initial nitrogen and phosphorus concentration between each treatment
and the control group (ANOVA, p > 0.05). The results showed that at the end of the experiment, the nitrogen concentration in the control group and treatment
1 was significantly higher than in the other treatments. There was also a significant difference in phosphorus concentration
between the control group and the IMTA treatments (ANOVA, p < 0.05). Growth rate, C and N content of the thallus, and mortality of scallop was different between the IMTA treatments.
The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus changed with different cultivation density
and time. The maximum reduction efficiency of ammonium and phosphorus was 83.7% and 70.4%, respectively. The maximum uptake
rate of ammonium and phosphorus was 6.3 and 3.3 μmol g−1 DW h−1. A bivalve/seaweed biomass ratio from 1:0.33 to 1:0.80 (treatments 2, 3, and 4) was preferable for efficient nutrient uptake
and for maintaining lower nutrient levels. Results indicate that G. lemaneiformis can efficiently absorb the ammonium and phosphorus from scallop excretion and is a suitable candidate for IMTA. 相似文献
127.
128.
以塔里木河中游荒漠河岸林胡杨为研究对象,选择中游河道新沙吉利克、坎白吾斯坦两个断面,分析塔里木河中游胡杨径向生长量的特点,基于离断面较近的气象站长时间序列的气温数据,采用相关性分析和MannKendall突变检验方法研究塔里木河中游胡杨径向生长量对温度动态变化的响应。结果显示:(1)塔里木河中游的河流沿岸,胡杨径向生长变化与温度变化均呈增加趋势;新沙吉利克、坎白吾斯坦断面胡杨径向生长量突变分别发生在1993年和1998年以后,且该地区的胡杨径向生长量对温度具有滞后性。(2)从时段分析发现,当年6~9月的温度对胡杨径向生长量的促进作用最大,6~9月的温度可能是该地区胡杨径向生长的限制性因子。(3)当年平均温度在13~33℃时,胡杨径向生长量达到最大值;当温度超过33℃,胡杨径向生长量呈现减弱趋势。研究表明,当年平均温度过高或过低都会抑制胡杨的径向生长。 相似文献
129.
GS3, a major QTL for grain length and weight and minor QTL for grain width and thickness in rice, encodes a putative transmembrane protein 总被引:25,自引:0,他引:25
Fan C Xing Y Mao H Lu T Han B Xu C Li X Zhang Q 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,112(6):1164-1171
The GS3 locus located in the pericentromeric region of rice chromosome 3 has been frequently identified as a major QTL for both grain
weight (a yield trait) and grain length (a quality trait) in the literature. Near isogenic lines of GS3 were developed by successive crossing and backcrossing Minghui 63 (large grain) with Chuan 7 (small grain), using Minghui
63 as the recurrent parent. Analysis of a random subpopulation of 201 individuals from the BC3F2 progeny confirmed that the GS3 locus explained 80–90% of the variation for grain weight and length in this population. In addition, this locus was resolved
as a minor QTL for grain width and thickness. Using 1,384 individuals with recessive phenotype (large grain) from a total
of 5,740 BC3F2 plants and 11 molecular markers based on sequence information, GS3 was mapped to a DNA fragment approximately 7.9 kb in length. A full-length cDNA corresponding to the target region was identified,
which provided complete sequence information for the GS3 candidate. This gene consists of five exons and encodes 232 amino acids with a putative PEBP-like domain, a transmembrane
region, a putative TNFR/NGFR family cysteine-rich domain and a VWFC module. Comparative sequencing analysis identified a nonsense
mutation, shared among all the large-grain varieties tested in comparison with the small grain varieties, in the second exon
of the putative GS3 gene. This mutation causes a 178-aa truncation in the C-terminus of the predicted protein, suggesting that GS3 may function
as a negative regulator for grain size. Cloning of such a gene provided the opportunity for fully characterizing the regulatory
mechanism and related processes during grain development. 相似文献