全文获取类型
收费全文 | 3719篇 |
免费 | 299篇 |
国内免费 | 155篇 |
出版年
2023年 | 41篇 |
2022年 | 69篇 |
2021年 | 110篇 |
2020年 | 85篇 |
2019年 | 119篇 |
2018年 | 124篇 |
2017年 | 71篇 |
2016年 | 107篇 |
2015年 | 103篇 |
2014年 | 199篇 |
2013年 | 275篇 |
2012年 | 138篇 |
2011年 | 191篇 |
2010年 | 147篇 |
2009年 | 199篇 |
2008年 | 216篇 |
2007年 | 178篇 |
2006年 | 205篇 |
2005年 | 168篇 |
2004年 | 158篇 |
2003年 | 134篇 |
2002年 | 134篇 |
2001年 | 94篇 |
2000年 | 82篇 |
1999年 | 96篇 |
1998年 | 94篇 |
1997年 | 50篇 |
1996年 | 58篇 |
1995年 | 47篇 |
1994年 | 55篇 |
1993年 | 38篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 31篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 30篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1972年 | 6篇 |
排序方式: 共有4173条查询结果,搜索用时 46 毫秒
141.
142.
取健康昆明种小鼠72只,随机分为3组,即自来水(tap water,TW)对照组、45 ppm(mg/L)深层海水(deep sea water,DSW)组、90 ppm深层海水组,每组24只,均为雄性,自由喂养8周,观察深层海水对小鼠胸腺指数、脾指数,脾淋巴细胞增殖,巨噬细胞吞噬功能,外周血CD4+、CD8+T细胞百分含量及CD4+/CD8+T细胞比值,血清免疫球蛋白(IgG、IgM、IgA)的影响。结果表明,深层海水可显著提高小鼠胸腺、脾指数,增强巨噬细胞吞噬功能,促进脾淋巴细胞增殖,提高外周血CD4+细胞百分含量及CD4+/CD8+细胞比例,增加血清IgA、IgM含量。因而,深层海水可增强小鼠机体的免疫功能。 相似文献
143.
本文将90只条件相同小鼠随机分成3组,A组服90 ppm(mg/mL)深层海水,B组服45 ppm深层海水,C组服自来水,均自由饮用30 d,第31 d时行耐缺氧实验、游泳耐力实验,断头采血,测定血细胞、肝肾功能及各种酶的变化。结果表明,在相同的饲养条件下三组体重无明显改变。A、B组比C组小鼠力竭游泳时间及耐缺氧时间显著延长(P<0.05),耗氧量显著减少(P<0.05),天冬氨酸氨基转移酶、肌酸激酶、肌酸肌酶同工酶降低,有显著差别(P<0.05),血常规、肝肾功能、电解质无显著性差异。因而,深层海水能改善酶的功能,减少小鼠的耗氧量,能明显增强小鼠的耐受力。 相似文献
144.
145.
目的为了为揭示肌萎缩脊髓侧索硬化症(amyotrophic lateral sclerosis,ALS)认知功能障碍的机制提供依据,观察不同年龄ALS转基因小鼠海马中突触囊泡蛋白(synaptophysin,Syp)的表达情况。方法取95d、108d和122dALS转基因鼠海马,应用免疫荧光、Westernblot、RT-PCR技术检测Syp在海马中的表达变化。结果与同窝野生型鼠比较,Syp蛋白和mRNA表达水平在95d龄ALS转基因鼠海马中无明显变化,在108d与122d龄ALS转基因鼠海马中明显降低。结论Syp在ALS转基因鼠海马中表达减少表明,突触可塑性降低是ALS学习记忆能力下降的重要病理学基础。 相似文献
146.
Sawao Murao Yasuhiro Shimizu Masaru Kameda Toyokazu Nishino 《Bioscience, biotechnology, and biochemistry》2013,77(12):3075-3077
Several analogs modifying the 6-methoxy-2-methoxymethyl-3-(3,4-methyienedioxyphenyl)-1,4-benzodioxan-7-yl group of haedoxans were synthesized and their insecticidal activity was examined. 2-(2,6-Dimethoxyphenoxy)-1-hydroxy-6-(2-methoxy-5-methoxyethoxyphenyl)-3,7-dioxabicyclo-[3.3.0]octane, which lacked the 3-(3,4-methylenedioxybenzyloxy) moiety of the benzodioxanyl group, was not insecticidal, but caused prolonged paralysis of the housefly. A compound replacing the 6-(2-methoxy-5-methoxyethoxyphenyl) by 6-(5-butoxy-2-methoxyphenyl) exhibited insecticidal activity comparable to one thirty-thousandth of that of haedosan A. It became evident that the 1,4-benzodioxane framework charging the 3-(3,4-methylenedioxy)phenyl group is important for the insecticidal activity of haedoxans. 相似文献
147.
Kenji Mori 《Bioscience, biotechnology, and biochemistry》2013,77(12):2899-2905
3-Isobutyroxy-β-ionone (III) is the proposed structure of quiesone, the naturally occurring inhibitor of the germination of Peronospora tabacina conidia. This was synthesized as a racemate and shown to possess qualitatively identical biological activity as quiesone itself. Employing an intermediate of this synthesis, dl-dehydrovomifoliol (VII) was also synthesized. 相似文献
148.
《Bioscience, biotechnology, and biochemistry》2013,77(9):1531-1535
Glycosides were screened for their lowering effect on the postprandial blood glucose rise in vivo. The effect of phlorizin and other phenolic glycosides on the postprandial blood glucose response to glucose ingestion was evaluated in Std ddY mice. When phlorizin was simultaneously added, the peak blood glucose level was significantly decreased by 51% (p < 0.01) compared to vehicles following glucose ingestion by mice, while the blood insulin responses were generally similar. Screening experiments were conducted with different classes of phenolic glycosides added to a glucose solution. Reductions of 40–52% (p < 0.05) were observed in vehicles containing arbutin, 4-hydroxyphenyl-α-d-glucopyranoside (hydroquinone-α-glucoside) or glycyrrhizin, and of only 15–31% (not significant) in vehicles containing neohesperidin dihydrochalcone, glycyrrhetinic acid monoglucuronide, or 3,4-dimethoxyphenyl-β-d-glucopyranoside. No lowering effect was observed in vehicles containing salicin. Since glycyrrhizin, arbutin, and hydroquinone-α-glucoside blunted to varying degrees the postprandial blood glucose rise following glucose ingestion, they may be useful adjuvants for the treatment of diabetic subjects. 相似文献
149.
Lyang-ja Lee Akira Kimura Tatsurokuro Tochikura 《Bioscience, biotechnology, and biochemistry》2013,77(4):731-737
UDP-galactose 4-epimerase (EC 5.1.3.2) was purified to a homogeneous state from Bifidobacterium bifidutn grown on a glucose medium. The molecular weight was estimated to be about 90,000. The purified enzyme was very stable and 60 % of its initial activity survived three months of storage at 4°C even at a low protein concentration (0.2 mg/ml). The optimum pH was 9.0, and the Km values for UDP-galactose and UDP-glucose were 5.4 × 10-4 M and 1.4×10 -3 M. UDP was a competitive inhibitor. The enzyme activity was stimulated by various sugar phosphates, but was slightly inhibited by fructose 1,6-diphosphate (FDP). A high concentration of galactose or glucose, which had no effect by itself, inhibited the activity in combination with UMP. The inhibition by FDP was also enhanced by combination with UMP. 相似文献
150.
《Bioscience, biotechnology, and biochemistry》2013,77(7):1772-1780
The aim of present study is to evaluate the effects of Garcinia cambogia on the mRNA levels of the various genes involved in adipogenesis, as well as on body weight gain, visceral fat accumulation, and other biochemical markers of obesity in obesity-prone C57BL/6J mice. Consumption of the Garcinia cambogia extract effectively lowered the body weight gain, visceral fat accumulation, blood and hepatic lipid concentrations, and plasma insulin and leptin levels in a high-fat diet (HFD)-induced obesity mouse model. The Garcinia cambogia extract reversed the HFD-induced changes in the expression pattern of such epididymal adipose tissue genes as adipocyte protein aP2 (aP2), sterol regulatory element-binding factor 1c (SREBP1c), peroxisome proliferator-activated receptor γ2 (PPARγ2), and CCAT/enhancer-binding protein α (C/EBPα). These findings suggest that the Garcinia cambogia extract ameliorated HFD-induced obesity, probably by modulating multiple genes associated with adipogenesis, such as aP2, SREBP1c, PPARγ2, and C/EBPα in the visceral fat tissue of mice. 相似文献