全文获取类型
收费全文 | 44120篇 |
免费 | 4032篇 |
国内免费 | 206篇 |
出版年
2018年 | 512篇 |
2017年 | 495篇 |
2016年 | 662篇 |
2015年 | 752篇 |
2014年 | 964篇 |
2013年 | 1148篇 |
2012年 | 1340篇 |
2011年 | 1366篇 |
2010年 | 908篇 |
2009年 | 904篇 |
2008年 | 1259篇 |
2007年 | 1259篇 |
2006年 | 1259篇 |
2005年 | 1082篇 |
2004年 | 1039篇 |
2003年 | 987篇 |
2002年 | 949篇 |
2001年 | 2839篇 |
2000年 | 2521篇 |
1999年 | 1858篇 |
1998年 | 637篇 |
1997年 | 560篇 |
1996年 | 498篇 |
1995年 | 427篇 |
1994年 | 414篇 |
1992年 | 1328篇 |
1991年 | 1207篇 |
1990年 | 1140篇 |
1989年 | 1092篇 |
1988年 | 987篇 |
1987年 | 964篇 |
1986年 | 856篇 |
1985年 | 844篇 |
1984年 | 603篇 |
1983年 | 554篇 |
1982年 | 398篇 |
1979年 | 674篇 |
1978年 | 479篇 |
1977年 | 448篇 |
1976年 | 393篇 |
1975年 | 518篇 |
1974年 | 593篇 |
1973年 | 590篇 |
1972年 | 599篇 |
1971年 | 581篇 |
1970年 | 547篇 |
1969年 | 546篇 |
1968年 | 452篇 |
1967年 | 390篇 |
1966年 | 419篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
W J Theuvenet T Nolthenius-Puylaert Z L Giedrojc Juraha J M Borghouts R van Twisk 《Plastic and reconstructive surgery》1984,74(4):539-543
Idiopathic calcinosis of the scrotum is a rare disease that may cause massive deformation of the scrotal wall. The first patient we present was also known to have neurofibromatosis. In the second patient we describe, nodules of idiopathic calcinosis of the scrotum were seen with walls that evidenced no epithelial lining, as well as calcification in epithelial cysts. At present, the only possible treatment is excision, and we excised the afflicted skin without problems in primary wound closure. 相似文献
52.
The effects of Heterosigma akashiwo on juvenile Oncorhynchus tshawytscha and its implications for fish culture 总被引:2,自引:0,他引:2
E. A. Black J.N. C. Whyth J. W. Bagshaw N. G. Ginther 《Zeitschrift fur angewandte Ichthyologie》1991,7(3):168-175
The effects of natural blooms of Heterosigma akashiwo on freshwater-and saltwater-acclimated juvenile chinook salmon were assessed. Rates of fish mortality in the blooms were independent of acclimation of fish to seawater and the ambient oxygen levels, but were dependent on concentration of algae and ambient water temperatures. No pathological abnormality to gills or other internal organs in the fish were evident. Aeration or oxygenation of fish cages did not enhance or inhibit fish survival in a H. akashiwo bloom. Cause of death was considered to be due to a labile ichthyotoxic agent. 相似文献
53.
54.
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
55.
Determination of products of acetohydroxy acid synthase by the colorimetric method, revisited 总被引:2,自引:0,他引:2
The enzyme acetohydroxy acid synthase (AHAS, EC 4.1.3.18) catalyzes two competing reactions of physiological importance: condensation of two molecules of pyruvate to form acetolactate (AL) or condensation of pyruvate and 2-ketobutyrate to form acetohydroxybutyrate (AHB). The activity of AHAS is most frequently analyzed using the Westerfeld method, in which the acetoin formed upon decarboxylation of AL is determined by colorimetric reaction with creatine and alpha-naphthol. However, there has been confusion as to the interpretation of the results of this assay in the presence of both substrates, conditions which lead to formation of both AL and AHB. By applying this assay to enzymatically prepared samples of AL and AHB which have also been analyzed by two other independent methods, we show here that the color yield for AHB in the commonly used assay is 35-40% that for equivalent amounts of acetoin or AL. The relative color yield is not significantly affected by varying the time or temperature of various steps in the color-forming reaction. This information could in principle be used, together with an independent specific assay for AHB, to determine the composition of an AHAS product mixture; it would, however, be less accurate than a simultaneous chromatographic method. 相似文献
56.
57.
58.
59.
R Lightowlers Z Chrzanowska-Lightowlers M Marusich R A Capaldi 《The Journal of biological chemistry》1991,266(12):7688-7693
Strains of the yeast Saccharomyces cerevisiae disrupted in YCOX4, the nuclear gene encoding cytochrome c oxidase subunit IV, do not assemble a functional or spectrally visible oxidase. We report the characterization of a yeast strain, RM1, expressing a mutated YCOX4 gene which is temperature sensitive for respiration at 37 degrees C, but incorporates cytochrome aa3 over all growth temperatures. The mutant enzyme is less stable than the wild type, with subunit IV readily proteolyzed without gross denaturation of the complex but with a concomitant loss of oxidase activity. When grown fermentatively at 37 degrees C, cytochrome c oxidase from the mutant strain had a turnover number of less than 3% of the normal complex, while Km values and subunit levels were comparable to normal. Thus alterations in subunit IV can perturb the enzyme structure and alter its catalytic rate, implying a role for this subunit in cytochrome c oxidase function as distinct from assembly. 相似文献
60.
In 0.05--0.1 mmol.l-1 concentration, bilirubin inhibits ADP-activated respiration of isolated liver mitochondria; it has no effect on respiration in the absence of ADP. Bilirubin-induced inhibition of respiration is not abolished by serum albumin, but bilirubin bound to serum albumin and the photodegradation products of bilirubin have no inhibitory effect. 相似文献