全文获取类型
收费全文 | 5535篇 |
免费 | 591篇 |
国内免费 | 1156篇 |
出版年
2024年 | 34篇 |
2023年 | 109篇 |
2022年 | 234篇 |
2021年 | 358篇 |
2020年 | 297篇 |
2019年 | 374篇 |
2018年 | 265篇 |
2017年 | 223篇 |
2016年 | 234篇 |
2015年 | 367篇 |
2014年 | 420篇 |
2013年 | 410篇 |
2012年 | 574篇 |
2011年 | 479篇 |
2010年 | 308篇 |
2009年 | 310篇 |
2008年 | 319篇 |
2007年 | 289篇 |
2006年 | 227篇 |
2005年 | 217篇 |
2004年 | 184篇 |
2003年 | 179篇 |
2002年 | 152篇 |
2001年 | 132篇 |
2000年 | 109篇 |
1999年 | 73篇 |
1998年 | 46篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 28篇 |
1994年 | 27篇 |
1993年 | 20篇 |
1992年 | 29篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1985年 | 6篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1973年 | 6篇 |
1972年 | 12篇 |
1971年 | 8篇 |
1970年 | 7篇 |
1968年 | 7篇 |
1967年 | 4篇 |
排序方式: 共有7282条查询结果,搜索用时 15 毫秒
31.
草鱼出血病病毒多肽的免疫原性 总被引:10,自引:1,他引:9
采用中和试验比较了草鱼出血病病毒GCHV873的11个多肽的免疫原性,确定了主要中和抗原。纯化的单个病毒多肽免疫家兔获得抗血清,多太VP1、VP5、VP6和VP9的抗血清具有中和效价,而VP2、VP3、VP4、VP8、VP10和VP11则不能诱生中和抗体。其中VP5的抗血清中和效价最高,因此,VP6极可能是病毒多肽中的主要中和抗原。 相似文献
32.
芦苇耐盐变异植株及其细胞学鉴定 总被引:5,自引:0,他引:5
用甲基磺酸乙酯(EMS)处理芦苇(Phragm itescom m unis Trin.)胚性愈伤组织。从处理后的愈伤组织诱导获得芦苇耐盐变异植株R5002-12。变异植株能在含有1% NaCl的MS培养基上生长。细胞学检查变异植株是混倍体,染色体数目变异范围在100至33 之间。分蘖植株具有相似的形态学及染色体变异特性 相似文献
33.
Ke Zeng John P. Rose Hong-Chi Chen Corey L. Strickland Chen-Pei D. Tu Bi-Cheng Wang 《Proteins》1994,20(3):259-263
A chimeric enzyme (GST121) of the human α-glutathione S-transferases GST1-1 and GST2-2, which has improved catalytic efficiency and thermostability from its wild-type parent proteins, has been crystallized in a space group that is isomorphous with that reported for crystals of GST1-1. However, a single-site (G82R) mutant of GST121, which exhibits a significant reduction both in vitro and in vivo in protein thermostability, forms crystals that are not isomorphous with GST1-1. The mutant protein crystallizes in space group P212121, with cell dimensions a = 49.5, b = 92.9, c = 115.9 Å, and one dimer per asymmetric unit. Preliminary crystallographic results show that a mutation of the surface residue Gly 82 from a neutral to a charged residue causes new salt bridges to be formed among the GST dimers, suggesting that the G82R mutant might aggregate more readily than does GST121 in solution resulting in a change of its solution properties. © 1994 Wiley-Liss, Inc. 相似文献
34.
沈阳西部污灌水中有机污染物的分析刘海玲,张丽珊,姚家彪,于殿臣,朱岩,可夫,姜萍(中国科学院沈阳应用生态研究所,110015)AnalysisofOrganicPollutantsinIrrigatedsewageInWesternShenyang.... 相似文献
35.
采用聚合酶链式反应(PCR)技术,对HPV-18序列中引物HP_1、HP_2之间的片段(F)进行扩增,通过两组阴、阳性对照实验证明扩增片段的特异性。用不同Mg浓度的缓冲系统进行PCR反应发现,缓冲系统中Mg浓度高低是影响HPV-18/HP_1、HP_2特异扩增的重要因素,高浓度Mg导致扩增特异性降低。对17例宫颈癌组织DNA进行PCR检测,有9例检出F片段,其检出率是53%,为HPV-18与宫颈癌的相关性提供证据。 相似文献
36.
草鱼出血病病毒多肽的荧光染色 总被引:1,自引:0,他引:1
将草鱼出血病病毒(GrassCarpHemorrhageVirus,GCHV)置于还原性的溶液中,然后加入等体积的NaHCO3配制的异硫氰酸荧光索溶液进行多肽的标记,再经SDS-PAGE分析,在紫外灯下即可检测到GCHV全部的11个结构多肽的荧光带。该方法最小检测量为500ng,由该方法回收的多肽具有抗原活性,可作为抗原进行免疫学实验。 相似文献
37.
Introns are essential for growth-regulated expression of the mouse thymidylate synthase gene. 总被引:5,自引:1,他引:4 下载免费PDF全文
The thymidylate synthase (TS) gene is expressed at much higher levels in proliferating cells than in quiescent cells. We have been studying the sequences that are important for regulating the mouse TS gene. We previously showed that DNA sequences upstream of the essential promoter elements as well as downstream of the ATG codon are both necessary (but neither is sufficient) for normal regulation in growth-stimulated cells. In the present study, we examined the possible roles of the coding region, polyadenylation signal, and introns as downstream regulatory elements. Minigenes consisting of 1 kb of the TS 5'-flanking region, the coding region (with or without various introns at their normal locations), and polyadenylation signals from the TS gene, the human beta-globin gene, and the bovine growth hormone gene were stably transfected into wild-type mouse 3T6 cells. Minigenes that contained introns 5 and 6, 1 and 2, or 1 alone were regulated regardless of which polyadenylation signal was included. A minigene that contained an internally deleted version of intron 1 was also regulated in response to growth stimulation. However, when all introns were omitted, there was little if any change in the level of minigene expression as cells progressed from G1 through S phase. These observations indicate that TS introns contain sequences that are necessary for normal growth-regulated expression of the mouse TS gene. These sequences appear to be associated with sequences that are important for splicing and to function in cooperation with upstream regulatory elements to bring about normal S-phase-specific expression. 相似文献
38.
Stimulation of gene expression by introns: conversion of an inhibitory intron to a stimulatory intron by alteration of the splice donor sequence. 总被引:6,自引:0,他引:6 下载免费PDF全文
Efficient expression of many mammalian genes depends on the presence of at least one intron. We previously showed that addition of almost any of the introns from the mouse thymidylate synthase (TS) gene to an intronless TS minigene led to a large increase in expression. However, addition of intron 4 led to a reduction in minigene expression. The goal of the present study was to determine why TS intron 4 was unable to stimulate expression. Insertion of intron 4 into an intron-dependent derivative of the ribosomal protein L32 gene did not lead to a significant increase in expression, suggesting that its inability to stimulate expression was due to sequences within the intron. Deleting most of the interior of intron 4, improving the putative branch point, removing purines from the pyrimidine stretch at the 3' end of the intron, or removing possible alternative splice acceptor or donor sites within the intron each had little effect on the level of expression. However, when the splice donor sequence of intron 4 was modified so that it was perfectly complementary to U1 snRNA, the modified intron 4 stimulated expression approximately 6-fold. When the splice donor site of TS intron 1 (a stimulatory intron) was changed to that of TS intron 4, the modified intron 1 was spliced very inefficiently and lost the ability to stimulate mRNA production. Our observations support the idea that introns can stimulate gene expression by a process that depends directly on the splicing reaction. 相似文献
39.
蛋白分泌作为细胞之间传递信号的途径之一,在微生物生存竞争中也扮演着重要的角色。革兰氏阴性菌可以通过Ⅵ型分泌系统(type Ⅵ secretion system, T6SS)将效应蛋白传递至胞外或原核和真核微生物中,从而介导微生物间的竞争或宿主-细菌的相互作用,最终建立竞争优势。本文主要总结了T6SS的结构与组成,并重点对效应蛋白的装配以及其与免疫蛋白的作用机制的研究进展进行阐述,为以后靶向T6SS抗菌药物的研制提供新思路。 相似文献
40.