全文获取类型
收费全文 | 22629篇 |
免费 | 1746篇 |
国内免费 | 1777篇 |
出版年
2024年 | 52篇 |
2023年 | 301篇 |
2022年 | 700篇 |
2021年 | 1268篇 |
2020年 | 862篇 |
2019年 | 1079篇 |
2018年 | 965篇 |
2017年 | 769篇 |
2016年 | 1047篇 |
2015年 | 1479篇 |
2014年 | 1719篇 |
2013年 | 1803篇 |
2012年 | 2069篇 |
2011年 | 1796篇 |
2010年 | 1131篇 |
2009年 | 1001篇 |
2008年 | 1122篇 |
2007年 | 906篇 |
2006年 | 870篇 |
2005年 | 680篇 |
2004年 | 598篇 |
2003年 | 539篇 |
2002年 | 457篇 |
2001年 | 410篇 |
2000年 | 377篇 |
1999年 | 358篇 |
1998年 | 230篇 |
1997年 | 212篇 |
1996年 | 196篇 |
1995年 | 185篇 |
1994年 | 140篇 |
1993年 | 128篇 |
1992年 | 153篇 |
1991年 | 121篇 |
1990年 | 104篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 59篇 |
1986年 | 31篇 |
1985年 | 40篇 |
1984年 | 21篇 |
1983年 | 25篇 |
1982年 | 8篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
51.
In humans, a deficiency of the lysosomal hydrolase α-
-iduronidase (IDUA; EC 3.2.1.76) results in the lysosomal storage of the glycosaminoglycans heparan sulfate and dermatan sulfate, thereby causing the lysosomal storage disorder mucopolysaccharidosis type I. The gene for IDUA is split into 14 exons spanning approximately 19 kb. We report the sequence of two noncontiguous segments of the IDUA gene, one 1.8-kb segment containing exons 1 and 2 and surrounding sequences and a second segment of 4.5 kb containing the last 12 exons. The potential promoter for IDUA has only GC box type consensus sequences consistent with a housekeeping promoter and is bounded by an Alu repeat sequence. The first two exons of IDUA are separated by an intron of 566 bp, then there is a large intron of approximately 13 kb, and the last 12 exons are clustered within 4.5 kb. No consensus polyadenylation signal was found in the 3′ untranslated region, although two variant polyadenylation signals are proposed. 相似文献
52.
1-Aminocyclopropane-l-carboxylate (ACC) synthase from applefruits was purified over 5,000-fold by conventional column chromatography.By immunizing mice with this partially purified enzyme preparation,8 hybridoma lines producing monoclonal antibodies against appleACC synthase were isolated. While all 8 clones immunoprecipitatednative ACC synthase, only two clones recognized the putative(48 kDa) ACC synthase on Western blots. When a partially purifiedACC synthase preparation was incubated with S-adenosyl-L-[carboxyl-14C]methionine(AdoMet), only one radioactive protein of 48 kDa was detectedon sodium dodecyl sulfate-poly-acrylamide gel electrophoresis.This radioactive protein was specifically immunoprecipitatedby the monoclonal antibodies, indicating that apple ACC synthaseis specifically radiolabeled by its substrate AdoMet, as istomato ACC synthase. Thus, the monoclonal antibodies recognizedboth native and AdoMet-inactivated forms of ACC synthase. Whilethese antibodies failed to im-munoprecipitate ACC synthase isolatedfrom ripe tomato fruits, ripe avocado fruits or auxin-treatedmungbean hypocotyls, they were effective in immunoprecipitatingthe enzyme isolated from ripe pear fruits. (Received August 11, 1990; Accepted October 17, 1990) 相似文献
53.
C T Liu Z M Guo 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1991,197(4):400-403
To study biochemical changes in cerebrospinal fluid (CSF), we developed a reliable technique for repeated collection of CSF in anesthetized strain 13 guinea pigs. The animal's head was mounted in a stereotaxic instrument with ventral tilt at 30 degrees, and cisternal puncture was made with an L-shaped, 23-gauge needle through the shaved skin. Clear CSF was collected in a 1-ml syringe surrounded by crushed ice. Each collection procedure lasted for 3 min, and three consecutive collections produced about 0.2 ml of CSF. Sampling was repeated at 3-hr intervals. With intravenous saline infusion (10 ml/kg.hr), a total volume of 0.6-1.0 ml of CSF was collected over 6 to 12 hr. Animals maintained a mean blood pressure, heart rate, and minute volume, with few changes during CSF sampling for the entire collection. 相似文献
54.
55.
56.
57.
58.
S Y Yan Z R Mao H Y Yang M A Tu S H Li G P Huang G S Li L Guo G Q Jin R F He 《The International journal of developmental biology》1991,35(4):429-435
The nucleus of a blastula cell from Tilapia (Oreochromis nilotica, family Cichlidae, order Perciformes) was transplanted into an enucleated egg of Loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes). From among 3747 nucleo-cytoplasmic hybrid (NCH) eggs two NCH larval fish (0.05%) were obtained; one died on the 6th day and the other died on the 12th day after the operation. Morphological examinations showed that both NCH larval fish had developed normally with an opened mouth except they could not take food after complete utilization of their egg yolk on the 5th day of development. The possible mechanisms for obtaining such inter-order NCH larval fish are discussed. This is the first report indicating that inter-order NCH larval fish can be obtained in spite of their evolutionary divergence. 相似文献
59.
60.
Uniformly fatty livers from orotic acid-fed rats secreted almost no very low density lipoproteins (VLDL) but normal amounts of nascent high density lipoproteins (HDL) accumulated in perfusates. When lecithin:cholesterol acyltransferase (LCAT) was inhibited, nascent HDL were uniformly discoidal and lacked cholesteryl esters. Lipid and apoprotein compositions of nascent HDL from normal and fatty livers were similar whether LCAT was inhibited or not. Apolipoprotein B-100 was not detected in perfusates of uniformly fatty livers, but small amounts of apolipoprotein B-48 were present in HDL2 fractions. Nascent lipoproteins were not seen in Golgi compartments, but lipid-rich particles were clearly evident in endoplasmic reticulum cisternae adjacent to the cis face of the Golgi complex, suggesting that orotic acid blocks VLDL secretion by preventing translocation of nascent particles from the endoplasmic reticulum to the cis Golgi compartment. The accumulation of normal amounts of discoidal HDL in liver perfusates despite virtual absence of triglyceride-rich lipoproteins in Golgi secretory compartments, the space of Disse, and the perfusate is inconsistent with the concept that nascent HDL are exclusively a product of surface remnants cast off during lipolysis of chylomicrons and VLDL. 相似文献