全文获取类型
收费全文 | 54969篇 |
免费 | 6011篇 |
国内免费 | 14篇 |
出版年
2022年 | 355篇 |
2021年 | 896篇 |
2020年 | 566篇 |
2019年 | 676篇 |
2018年 | 791篇 |
2017年 | 721篇 |
2016年 | 1251篇 |
2015年 | 2001篇 |
2014年 | 2237篇 |
2013年 | 2690篇 |
2012年 | 3437篇 |
2011年 | 3352篇 |
2010年 | 2171篇 |
2009年 | 1874篇 |
2008年 | 2815篇 |
2007年 | 2695篇 |
2006年 | 2454篇 |
2005年 | 2409篇 |
2004年 | 2399篇 |
2003年 | 2215篇 |
2002年 | 2035篇 |
2001年 | 1168篇 |
2000年 | 1094篇 |
1999年 | 989篇 |
1998年 | 667篇 |
1997年 | 553篇 |
1996年 | 537篇 |
1995年 | 456篇 |
1994年 | 481篇 |
1993年 | 483篇 |
1992年 | 812篇 |
1991年 | 734篇 |
1990年 | 688篇 |
1989年 | 733篇 |
1988年 | 651篇 |
1987年 | 686篇 |
1986年 | 539篇 |
1985年 | 649篇 |
1984年 | 574篇 |
1983年 | 495篇 |
1982年 | 482篇 |
1981年 | 443篇 |
1980年 | 409篇 |
1979年 | 496篇 |
1978年 | 446篇 |
1977年 | 382篇 |
1976年 | 382篇 |
1975年 | 364篇 |
1974年 | 436篇 |
1973年 | 404篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Fillet samples of the toothfish Dissostichus eleginoides and D. mawsoni can be distinguished readily by muscle proteins revealed by isoelectric focusing and mitochondrial DNA markers. The proteins also distinguish toothfish from other species marketed under similar trade names. 相似文献
42.
Attempts to predict the response of species to long-term environmental change are generally based on extrapolations from laboratory experiments that inevitably simplify the complex interacting effects that occur in the field. We recorded heart rates of two genetic lineages of the brown mussel Perna perna over a full tidal cycle in-situ at two different sites in order to evaluate the cardiac responses of the two genetic lineages present on the South African coast to temperature and the immersion/emersion cycle. “Robomussel” temperature loggers were used to monitor thermal conditions at the two sites over one year. Comparison with live animals showed that robomussels provided a good estimate of mussel body temperatures. A significant difference in estimated body temperatures was observed between the sites and the results showed that, under natural conditions, temperatures regularly approach or exceed the thermal limits of P. perna identified in the laboratory. The two P. perna lineages showed similar tidal and diel patterns of heart rate, with higher cardiac activity during daytime immersion and minimal values during daytime emersion. Comparison of the heart rates measured in the field with data previously measured in the laboratory indicates that laboratory results seriously underestimate heart rate activity, by as much as 75%, especially during immersion. Unexpectedly, field estimates of body temperatures indicated an ability to tolerate temperatures considered lethal on the basis of laboratory measurements. This suggests that the interaction of abiotic conditions in the field does not necessarily raise vulnerability to high temperatures. 相似文献
43.
44.
45.
Carolyn Beebe Smith 《Neurochemical research》1991,16(9):1037-1046
Special issue dedicated to Dr. Louis Sokoloff. 相似文献
46.
47.
48.
Anthony J. Hesketh Caroline Maloney Christopher A. Behr Morris C. Edelman Richard D. Glick Yousef Al-Abed Marc Symons Samuel Z. Soffer Bettie M. Steinberg 《PloS one》2015,10(12)
Metastatic Ewing Sarcoma carries a poor prognosis, and novel therapeutics to prevent and treat metastatic disease are greatly needed. Recent evidence demonstrates that tumor-associated macrophages in Ewing Sarcoma are associated with more advanced disease. While some macrophage phenotypes (M1) exhibit anti-tumor activity, distinct phenotypes (M2) may contribute to malignant progression and metastasis. In this study, we show that M2 macrophages promote Ewing Sarcoma invasion and extravasation, pointing to a potential target of anti-metastatic therapy. CNI-1493 is a selective inhibitor of macrophage function and has shown to be safe in clinical trials as an anti-inflammatory agent. In a xenograft mouse model of metastatic Ewing Sarcoma, CNI-1493 treatment dramatically reduces metastatic tumor burden. Furthermore, metastases in treated animals have a less invasive morphology. We show in vitro that CNI-1493 decreases M2-stimulated Ewing Sarcoma tumor cell invasion and extravasation, offering a functional mechanism through which CNI-1493 attenuates metastasis. These data indicate that CNI-1493 may be a safe and effective adjuvant agent for the prevention and treatment of metastatic Ewing Sarcoma. 相似文献
49.
50.
Charles Romeo Naoko Moriwaki Kerry T. Yasunobu Irwin C. Gunsalus Hideo Koga 《Journal of Protein Chemistry》1987,6(3):253-261
The first 12 NH2-terminal amino acids of the Pseudomonas putida putidaredoxin reductase were shown to be Met-Asn-Ala-Asn-Asp-Asn-Val-Val-Ile-Val-Gly-Thr. Comparison of these data with the DNA sequence of the BamHI-HindIII 197-base fragment derived from the PstI 2.2-kb fragment obtained from the P. putida plasmid showed that the putidaredoxin reductase gene was downstream from the cytochrome P-450 gene and the intergenic region had the 24-nucleotide sequence TAAACACATGGGAGTGCGTGCTAA. The Shine-Dalgarno sequence GGAG was detected in this region. The initiating triplet for the reductase gene was GTG, which normally codes for valine, but in the initiating codon position codes for methionine. From the amino acid sequence and X-ray data comparisons with other flavoproteins, what appears to be the AMP binding region of the FAD can be recognized in the NH2-terminal portion of the reductase involving residues 5–35.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985. 相似文献