全文获取类型
收费全文 | 11685篇 |
免费 | 1061篇 |
国内免费 | 1154篇 |
出版年
2024年 | 44篇 |
2023年 | 196篇 |
2022年 | 407篇 |
2021年 | 674篇 |
2020年 | 474篇 |
2019年 | 556篇 |
2018年 | 523篇 |
2017年 | 397篇 |
2016年 | 525篇 |
2015年 | 766篇 |
2014年 | 922篇 |
2013年 | 919篇 |
2012年 | 1089篇 |
2011年 | 979篇 |
2010年 | 555篇 |
2009年 | 538篇 |
2008年 | 624篇 |
2007年 | 534篇 |
2006年 | 422篇 |
2005年 | 332篇 |
2004年 | 317篇 |
2003年 | 268篇 |
2002年 | 258篇 |
2001年 | 186篇 |
2000年 | 167篇 |
1999年 | 154篇 |
1998年 | 109篇 |
1997年 | 97篇 |
1996年 | 101篇 |
1995年 | 73篇 |
1994年 | 83篇 |
1993年 | 59篇 |
1992年 | 69篇 |
1991年 | 72篇 |
1990年 | 51篇 |
1989年 | 34篇 |
1988年 | 42篇 |
1987年 | 23篇 |
1986年 | 31篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1977年 | 11篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
本文以O139死菌免疫健康家兔,经吸收去除非特异性凝集素制成的特异性诊断血清,专供诊断霍乱弧菌O139之用。采用玻片凝集试验对5株O139菌株及126株肠道菌进行验证,在敏感性和特异性方面均获得满意的结果。 相似文献
102.
103.
柴达木盆地第四系介形类化石带与磁性柱 总被引:13,自引:2,他引:11
柴达木盆地东部晚上新世-全新世湖相沉积巨厚,无明显间断,微体化石丰富。区内已建厚度超过2000m的第四系磁性柱中,记录了布容、松山和高斯极性时带。由于有剖面上部的同位素测年数据和剖面中、下部的介形类化石带序列的对比成果配合验证,布容、松山极性时下限的确定和布拉克、莫纳、琵琶湖、奥尔杜威、马默思等亚极性时的鉴别依据充足可信。据此极性年表标定的晚上新世-第四纪介形类化石带序列中12个标准化石的时限得以识别。古生态研究与壳体元素分析的资料表明,始见于距今305万年的Microlimnocytheresinensis指示低温水体,该化石带的出现标志着中新世以来柴达木盆地古气候的首次明显变冷。 相似文献
104.
Competition between Adjacent Meiotic Recombination Hotspots in the Yeast Saccharomyces Cerevisiae 总被引:1,自引:0,他引:1 下载免费PDF全文
In a wild-type strain of Saccharomyces cerevisiae, a hotspot for meiotic recombination is located upstream of the HIS4 gene. An insertion of a 49-bp telomeric sequence into the coding region of HIS4 strongly stimulates meiotic recombination and the local formation of meiosis-specific double-strand DNA breaks (DSBs). When strains are constructed in which both hotspots are heterozygous, hotspot activity is substantially less when the hotspots are on the same chromosome than when they are on opposite chromosomes. 相似文献
105.
Vinculin Proteolysis Unmasks an ActA Homolog for Actin-based Shigella Motility 总被引:2,自引:0,他引:2 下载免费PDF全文
Roney O. Laine William Zeile Fan Kang Daniel L. Purich Frederick S. Southwick 《The Journal of cell biology》1997,138(6):1255-1264
In polarized Madin-Darby canine kidney (MDCK) cells, the transferrin receptor (TR) is selectively delivered to the basolateral surface, where it internalizes transferrin via clathrin-coated pits and recycles back to the basolateral border. Mutant tailless receptors are sorted randomly in both the biosynthetic and endocytic pathways, indicating that the basolateral sorting of TR is dependent upon a signal located within the 61–amino acid cytoplasmic domain. To identify the basolateral sorting signal of TR, we have analyzed a series of mutant human TR expressed in MDCK cells. We find that residues 19–41 are sufficient for basolateral sorting from both the biosynthetic and endocytic pathways and that this is the only region of the TR cytoplasmic tail containing basolateral sorting information. The basolateral sorting signal is distinct from the YTRF internalization signal contained within this region and is not tyrosine based. Detailed functional analyses of the mutant TR indicate that residues 29–35 are the most important for basolateral sorting from the biosynthetic pathway. The structural requirements for basolateral sorting of internalized receptors from the endocytic pathway are not identical. The most striking difference is that alteration of G31DNS34 to YTRF impairs basolateral sorting of newly synthesized receptors from the biosynthetic pathway but not internalized receptors from the endocytic pathway. Also, mutations have been identified that selectively impair basolateral sorting of internalized TRs from the endocytic pathway without affecting basolateral sorting of newly synthesized receptors. These results imply that there are subtle differences in the recognition of the TR basolateral sorting signal by separate sorting machinery located within the biosynthetic and endocytic pathways. 相似文献
106.
107.
Hong-Bo Qu Xian-En Zhang Wen-Wu Chui Shu-Zheng Zhang Gao-Xiang Li Fan Ouyang 《Biotechnology Techniques》1995,9(6):445-450
Summary A dual-enzyme electrode flow injection system that can simultaneously determine glucose and maltose is used for an on-line study of starch hydrolyses catalysed by amylases. With the working system, determinations can be made every 2 minutes. A 10 L sample size with recycled back-flow minimises any loss of the reaction medium. The production, growth and decay of glucose and maltose concentrations during starch hydrolysis under various enzymatic conditions can thus be closely monitored, making it useful for the study of the catalytic kinetics of amylases and in screening and analysing enzyme systems. 相似文献
108.
鹅掌楸属植物引导组织和花粉管生长 总被引:9,自引:0,他引:9
应用光学显微镜和常规石蜡切片技术研究了鹅掌楸属(LiriodendronL.)两种植物雌蕊引导组织的分布和个体发育,引导组织是由心皮边缘或内表面的表皮细胞层或亚细胞层发育形成,是由一层细胞组成的连续层,覆盖干柱头、花柱道和珠柄的表面,引导组织的细胞形态学因其所在部位不同而有差异。在电境水平上研究了柱头和花柱引导组织的超微结构,引导组织细胞是分泌型的传递细胞,其分泌面发育了明显的壁内突,细胞质中富含内质网、多聚核糖体、各种小泡、高尔基体和线粒体,大液泡通常远离分泌面。文中还探讨了花粉管生长后引导组织的变化。 相似文献
109.
Antibodies against aflatoxin Q1 (AFQ1) were obtained from rabbits after immunization of either AFQ1-hemisuccinate or AFQ2a conjugated to bovine serum albumin. Both radioimmunoassay and enzyme-linked immunosorbent assaY (ELISA) were used for the determination of antibody titers and specificities. Antibodies obtained from rabbits after immunization with AFQ1-hemisuccinate-bovine serum albumin had the highest affinity to aflatoxin B1, whereas antibodies obtained from rabbits after immunization with AFQ2a-bovine serum albumin bound most effectively with AFQ2a. AFQ2a antibody was selected for the subsequent direct and indirect ELISA for the detection of AFQ1 in biological fluids. When AFQ2a-peroxidase and AFQ2a antibody were used, direct ELISA was able to detect as low as 2 ppb (ng/ml) of AFQ1 spiked in the urine samples that had been subjected to a Sep-Pak cleanup treatment. In indirect ELISA in which the antigen (AFQ2a-bovine serum albumin) was coated to the solid phase followed by reaction with rabbit antibody and goat anti-rabbit immunoglobulin G-peroxidase conjugate, 50-fold less antibody was used without sacrificing sensitivity. Recoveries of AFQ1 added to urine samples (2 to 40 ppb) were 46.3 to 73% and 65.8 to 85.8% for direct and indirect ELISA, respectively. 相似文献
110.