全文获取类型
收费全文 | 84487篇 |
免费 | 19160篇 |
国内免费 | 5585篇 |
出版年
2024年 | 179篇 |
2023年 | 757篇 |
2022年 | 1828篇 |
2021年 | 3120篇 |
2020年 | 3894篇 |
2019年 | 5888篇 |
2018年 | 5993篇 |
2017年 | 5907篇 |
2016年 | 6543篇 |
2015年 | 7002篇 |
2014年 | 7511篇 |
2013年 | 8316篇 |
2012年 | 6829篇 |
2011年 | 6208篇 |
2010年 | 6155篇 |
2009年 | 4631篇 |
2008年 | 4063篇 |
2007年 | 3309篇 |
2006年 | 2888篇 |
2005年 | 2493篇 |
2004年 | 2289篇 |
2003年 | 2133篇 |
2002年 | 1787篇 |
2001年 | 1544篇 |
2000年 | 1274篇 |
1999年 | 958篇 |
1998年 | 496篇 |
1997年 | 441篇 |
1996年 | 416篇 |
1995年 | 416篇 |
1994年 | 380篇 |
1993年 | 312篇 |
1992年 | 392篇 |
1991年 | 353篇 |
1990年 | 276篇 |
1989年 | 250篇 |
1988年 | 182篇 |
1987年 | 227篇 |
1986年 | 182篇 |
1985年 | 170篇 |
1984年 | 124篇 |
1983年 | 121篇 |
1982年 | 100篇 |
1981年 | 91篇 |
1980年 | 59篇 |
1979年 | 73篇 |
1978年 | 81篇 |
1976年 | 55篇 |
1973年 | 66篇 |
1972年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The inhibitory effect of two chemokine decoy receptors (CDRs), DARC and D6, on breast cancer metastasis is mainly due to their ability to sequester pro-malignant chemokines. We hypothesized that genetic variants in the DARC and CCBP2 (encoding D6) genes may be associated with breast cancer progression. In the present study, we evaluated the genetic contributions of DARC and CCBP2 to metastatic potential, indicated by lymph node metastasis (LNM). Ten single-nucleotide polymorphisms (SNPs) (potentially functional SNPs and block-based tagging SNPs) in DARC and CCBP2 were genotyped in 785 breast cancer patients who had negative lymph nodes and 678 patients with positive lymph nodes. Two non-synonymous SNPs, rs12075 (G42D) in DARC and rs2228468 (S373Y) in CCBP2, were observed to be associated with LNM in univariate analysis and remained significant after adjustment for conventional clinical risk factors, with odds ratios (ORs) of 0.54 (95% confidence interval [CI], 0.37 to 0.79) and 0.78 (95% CI, 0.62 to 0.98), respectively. Additional functional experiments revealed that both of these significant SNPs could affect metastasis of breast cancer in xenograft models by differentially altering the chemokine sequestration ability of their corresponding proteins. Furthermore, heterozygous GD genotype of G42D on human erythrocytes had a significantly stronger chemokine sequestration ability than homozygous GG of G42D ex vivo. Our data suggest that the genetic variants in the CDR genes are probably associated with the varied metastatic potential of breast cancer. The underlying mechanism, though it needs to be further investigated, may be that CDR variants could affect the chemokine sequestration ability of CDR proteins. 相似文献
994.
Nathan S. Garcia Fei-Xue Fu Cynthia L. Breene Elizabeth K. Yu Peter W. Bernhardt Margaret R. Mulholland 《欧洲藻类学杂志》2013,48(1):128-139
We examined the combined effects of light and pCO2 on growth, CO2-fixation and N2-fixation rates by strains of the unicellular marine N2-fixing cyanobacterium Crocosphaera watsonii with small (WH0401) and large (WH0402) cells that were isolated from the western tropical Atlantic Ocean. In low-pCO2-acclimated cultures (190 ppm) of WH0401, growth, CO2-fixation and N2-fixation rates were significantly lower than those in cultures acclimated to higher (present-day ~385 ppm, or future ~750 ppm) pCO2 treatments. Growth rates were not significantly different, however, in low-pCO2-acclimated cultures of WH0402 in comparison with higher pCO2 treatments. Unlike previous reports for C. watsonii (strain WH8501), N2-fixation rates did not increase further in cultures of WH0401 or WH0402 when acclimated to 750 ppm relative to those maintained at present-day pCO2. Both light and pCO2 had a significant negative effect on gross : net N2-fixation rates in WH0402 and trends were similar in WH0401, implying that retention of fixed N was enhanced under elevated light and pCO2. These data, along with previously reported results, suggest that C. watsonii may have wide-ranging, strain-specific responses to changing light and pCO2, emphasizing the need for examining the effects of global change on a range of isolates within this biogeochemically important genus. In general, however, our data suggest that cellular N retention and CO2-fixation rates of C. watsonii may be positively affected by elevated light and pCO2 within the next 100 years, potentially increasing trophic transfer efficiency of C and N and thereby facilitating uptake of atmospheric carbon by the marine biota. 相似文献
995.
996.
997.
998.
Yuxiang Yao Hongzhi Tang Huixue Ren Hao Yu Lijuan Wang Ping Xu 《Journal of bacteriology》2012,194(20):5714-5715
We announce a 4.63-Mb genome assembly of an isolated bacterium that is the first sequenced nicotine-degrading Arthrobacter strain. Nicotine catabolism genes of the nicotine-degrading plasmid pAO1 were predicted, but plasmid function genes were not found. These results will help to better illustrate the molecular mechanism of nicotine degradation by Arthrobacter. 相似文献
999.
M. Ts. Itigilova N. A. Tashlykova E. Yu. Afonina 《Contemporary Problems of Ecology》2016,9(6):783-789
The content and accumulation of particular heavy metals in phyto- and zooplankyon from the technogenically transformed Lake Kenon (Chita, Transbaikalia) have been studied. Algae contains the highest concentrations of Zn and Sr. Zooplankton is characterized by concentrations of Ni, Cu, Cd, and Hg either below or equivalent to those known for other water bodies. It has been shown that the distribution of heavy metals in the studied water body is differentiated. Their greatest concentration has been registered in the plankton of technogenically contaminated sites—CHPP and Oil Tank Farm. 相似文献
1000.
Evidence for the effect of serotonin receptor 1A gene (HTR1A) polymorphism on tractability in Thoroughbred horses
下载免费PDF全文
![点击此处可从《Animal genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Y. Hori T. Tozaki Y. Nambo F. Sato M. Ishimaru M. Inoue‐Murayama K. Fujita 《Animal genetics》2016,47(1):62-67
Tractability, or how easily animals can be trained and controlled, is an important behavioural trait for the management and training of domestic animals, but its genetic basis remains unclear. Polymorphisms in the serotonin receptor 1A gene (HTR1A) have been associated with individual variability in anxiety‐related traits in several species. In this study, we examined the association between HTR1A polymorphisms and tractability in Thoroughbred horses. We assessed the tractability of 167 one‐year‐old horses reared at a training centre for racehorses using a questionnaire consisting of 17 items. A principal components analysis of answers contracted the data to five principal component (PC) scores. We genotyped two non‐synonymous single nucleotide polymorphisms (SNPs) in the horse HTR1A coding region. We found that one of the two SNPs, c.709G>A, which causes an amino acid change at the intracellular region of the receptor, was significantly associated with scores of four of five PCs in fillies (all Ps < 0.05) and one PC in colts (P < 0.01). Horses carrying an A allele at c.709G>A showed lower tractability. This result provides the first evidence that a polymorphism in a serotonin‐related gene may affect tractability in horses with the effect partially different depending on sex. 相似文献