全文获取类型
收费全文 | 22503篇 |
免费 | 2089篇 |
国内免费 | 2353篇 |
出版年
2024年 | 53篇 |
2023年 | 229篇 |
2022年 | 546篇 |
2021年 | 846篇 |
2020年 | 676篇 |
2019年 | 860篇 |
2018年 | 820篇 |
2017年 | 674篇 |
2016年 | 973篇 |
2015年 | 1332篇 |
2014年 | 1656篇 |
2013年 | 1720篇 |
2012年 | 1978篇 |
2011年 | 1875篇 |
2010年 | 1272篇 |
2009年 | 1109篇 |
2008年 | 1340篇 |
2007年 | 1210篇 |
2006年 | 1109篇 |
2005年 | 1028篇 |
2004年 | 956篇 |
2003年 | 869篇 |
2002年 | 804篇 |
2001年 | 451篇 |
2000年 | 375篇 |
1999年 | 317篇 |
1998年 | 246篇 |
1997年 | 206篇 |
1996年 | 149篇 |
1995年 | 104篇 |
1994年 | 94篇 |
1993年 | 73篇 |
1992年 | 123篇 |
1991年 | 109篇 |
1990年 | 70篇 |
1989年 | 84篇 |
1988年 | 47篇 |
1987年 | 62篇 |
1986年 | 42篇 |
1985年 | 47篇 |
1984年 | 45篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 28篇 |
1980年 | 25篇 |
1979年 | 31篇 |
1978年 | 27篇 |
1976年 | 19篇 |
1974年 | 19篇 |
1972年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Urinary galactitol in galactosemic patients 总被引:2,自引:0,他引:2
72.
73.
ELECTRON MICROSCOPY OF VIRUS-INFECTED YEAST CELLS 总被引:1,自引:0,他引:1
74.
75.
76.
本文报告了25%烧伤后注射免疫抑制剂(地寨米松磷酸钠)大鼠7种肠道细菌的定量、内脏及血液的细菌培养和肠壁的病理形态学改变。单纯烧伤组(B组)和单纯注射免疫抑制剂组(Ⅰ组)动物肠壁的病理改变较轻,肠道菌群改变不明显,其肠道细菌易位率也很低。烧伤后注射免疫抑制剂的动物(BⅠ组)肠壁病变严重,肠道菌群改变明显。其中,肠杆菌在回肠、盲肠,结肠内容物中的菌量均明显升高;回肠内容物中拟杆菌的菌量明显减少;该组动物肠道细菌易位率也明显增高,达60%。此外,BⅠ组、Ⅰ组部分动物发生了由棒状杆菌及由棒状扦菌和肠杆菌混合引起的内源性感染。根据不同肠段肠壁病变严重程度、菌群变化的部位以及不同部位肠管生理功能的不同,我们推测,回肠以上肠段是肠道细菌易位的主要部位。 相似文献
77.
A proteolytically modified form of the Escherichia coli single-stranded DNA-Binding protein (SSB) has been crystallized from 15% saturated sodium citrate. Crystals as large as 1.0 mm x 0.3 mm x 0.2 mm were obtained and these diffract beyond 3A resolution. X-ray photographic analysis demonstrated a rhombohedral unit cell of space group R3 with an equivalent triple centered hexagonal unit cell having dimensions of a = b = 62.9A and c = 264.3A. These crystals were judged to be adequate for a three dimensional structure determination. 相似文献
78.
79.
M H Kim R Nakayama P Manos J E Tomlinson E Choi J D Ng D Holten 《Journal of lipid research》1989,30(5):663-671
Rats were fasted or fasted and refed simple purified diets so the effects of individual carbohydrates or fats could be studied. Freshly isolated hepatocytes from these animals were used to measure both apoE synthesis and mRNA levels so any changes in apoE synthesis that might occur without changes in its mRNA could be detected. Some of these experiments were done with both sexes. Both fasting and fasting and refeeding a 60% glucose fat-free diet significantly increased spoE synthesis. However, cyclic AMP is not likely to rapidly mediate the effect of fasting since dibutyryl cAMP slightly lowered (rather than increased) apoE synthesis and mRNA when injected into rats for 4.5 h. Dietary fat had no effect either in the absence of carbohydrate or when consumption of carbohydrate was constant in pair-fed rats. ApoE mRNA levels remained normal for 4 days in primary hepatocytes cultured in medium that had only amino acids as an energy source. Added hormones or fructose had no significant effect. Thus, only fasting and fasting and refeeding glucose were able to significantly change apoE synthesis or mRNA levels. Synthesis of apoE may be regulated to increase when apoE is secreted with very low density lipoprotein or when apoE in secreted high density lipoprotein is needed to acquire cholesteryl esters for the synthesis of bile salts and acids by liver. 相似文献
80.
Summary The condensation reactions of activated nucleotides, ImpN or 2-MeImpN, with the selfcomplementary ribo-octanucleotide GCGCGCGC or with the partially self-complementary heptanucleotide GCGCGCG were studied. The templatedirected reaction of 2-meImpC with the heptamer yields the 3–5 octamer as the main product. All other reactions yield 2–5-linked octamers and pyrophosphates as major products. Surprisingly, 2-MeImpG facilitates the reaction of 2-MeImpC with the heptamer.Procedures for the analysis by gel electrophoresis of the oligomeric products obtained in reactions of this kind are described. 相似文献