全文获取类型
收费全文 | 1052篇 |
免费 | 76篇 |
国内免费 | 95篇 |
专业分类
1223篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 42篇 |
2021年 | 64篇 |
2020年 | 53篇 |
2019年 | 66篇 |
2018年 | 45篇 |
2017年 | 42篇 |
2016年 | 63篇 |
2015年 | 55篇 |
2014年 | 83篇 |
2013年 | 88篇 |
2012年 | 97篇 |
2011年 | 79篇 |
2010年 | 64篇 |
2009年 | 63篇 |
2008年 | 66篇 |
2007年 | 46篇 |
2006年 | 42篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 3篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 16篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1223条查询结果,搜索用时 0 毫秒
131.
132.
Age and growth characteristics of Schizopygopsis younghusbandi Regan, 1905 in the Yarlung Tsangpo River in Tibet,China 总被引:1,自引:0,他引:1
Y.‐J. Duan C.‐X. Xie X.‐J. Zhou B.‐S. Ma B. Huo 《Zeitschrift fur angewandte Ichthyologie》2014,30(5):948-954
To better understand the biology of Schizopygopsis younghusbandi Regan, 1905 and its relationship with management considerations, this study describes the relationships between otolith size and fish length and age, verifies annual periodicity of otolith annulus formation, and estimates the S. younghusbandi growth parameters. These age and growth characteristics were studied using 694 specimens collected from August 2008 to August 2009. Otoliths grew asymmetrically throughout the range of standard length (SL) studied, showing a clear pattern of alternating translucent and opaque bands. Marginal increment ration (MIR) analysis of specimens up to 6 years of age indicated that one opaque band and one translucent band were laid down each year. Maximum observed age was 17 years, corresponding to a female of 35.8 cm SL and 589.1 g body weight (BW). The SL‐BW relationship was described as BW = 1.122 × 10?5 SL3.030 for sexes combined. The von Bertalanffy growth function was used to model back‐calculated lengths as Lt = 338.4 (1?e?0.233 (t + 0.403)) for males, and Lt = 433.9 (1?e?0.194 (t + 0.397)) for females. Growth performance of S. younghusbandi was relatively higher than those of other Schizothoracinaes inhabiting the same river. 相似文献
133.
Background
Tuberculosis (TB), caused by Mycobacterium tuberculosis complex (MTBC), is one of the major causes of death in the world today. Although China has the second largest global case rate of tuberculosis, a systematic study of TB prevalence in China has not been completed. From 2006 to 2007, the base line surveillance of tuberculosis was carried out by Ministry of Health, and more than 4000 representative strains were selected from 31 provinces in China.Methodology/Principal Findings
The aim of the present research was to survey the genotypes of representative Mycobacterium tuberculosis (M. tuberculosis) strains from China using spacer oligonucleotide typing (spoligotyping), and to analyze the relationship between genotype and drug resistance for the first time. A total of 4017 clinical isolates were collected from 2007 to 2008 throughout China. Among those M. tuberculosis isolates, 2500 (62.2%) isolates were Beijing genotypes. The percentage of Beijing genotypes in northern China was higher than in southern China (76.5% vs. 53.2%). Additionally, the frequencies of rifampin-resistant, ofloxacin-resistant and multidrug-resistant isolates were significantly higher in Beijing genotype strains than non-Beijing strains. Furthermore, a novel genotype named “China Southern genotype (CS)” was only isolated from Fujian and Guangdong provinces. Hence, it is very practical to uncover the reason for prevalence of the CS type in southern China.Conclusions/Significance
In conclusion, Beijing family genotypes were still the predominant genotype throughout China, which exhibited a greater correlation with rifampin-resistance, ofloxacin-resistance and MDR phenotypes than other TB spoligotypes, and some regions of China showed several unique characters in the distribution of M. tuberculosis genotypes. Our research represents an important contribution for the TB control and research community, which completes broad pictures on drug resistance levels and distribution of M. tuberculosis strain types over China. 相似文献134.
谷胱甘肽硫转移酶(GST)的固定化及酶学特性研究 总被引:1,自引:0,他引:1
对谷胱甘肽硫转移酶的固定化、游离酶和固定化酶的酶学特性进行了研究,通过试验,确定谷胱甘肽硫转移酶的最佳固定化条件为先用2%壳聚糖吸附酶,然后再加戊二醛交联,交联用戊二醛浓度为1.2%,交联时间6h;游离酶的最适温度为45—55℃,最适pH值为6.5-7.0:固定化酶的最适温度为45-50℃,最适pH值为7.0;游离酶和固定化酶的最适酶促反应时间为30min。 相似文献
135.
Effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum 总被引:1,自引:0,他引:1
The effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum at the temperature of 19.6–21.6 °C, the salinity of 34‰ and pH of 8.0 were investigated from May 18 to July 18, 2006. In this study, the early, middle and late umbo-veliger larvae with the shell lengths of 100, 140, and 190 μm were subject to temporary food deprivation for up to 4.5, 20, and 25d at 0.5, 4, 5d intervals, followed by refeeding for the remaining of a 24, 20, 25d period, respectively. The results suggested that the larvae should have shown considerable tolerance to starvation due to their endogenous and exterior nutrition material, for larvae and time to the point-of-no-return (PNR: the threshold point during starvation after which larvae could no longer metamorphose even if food is provided) were calculated to be 4.25, 17.54, and 22.17d. As the starvation period prolonged, the mean shell length of larvae starved got close to constants at 1.5, 4, and 15d after starvation, which were different for larvae at different stages when starvation began, survival of larvae decreased, and was lower in treatments starved earlier in development than those starved later, for the early, middle and late umbo-veliger larvae, after 4.5, 20 and 25d of starvation period, few larvaes were alive. After starvation period, the alive larvaes were able to metamorphose and had a capability of compensatory growth when refeeding was given. Starvation not only affected metamorphosis rate, but also caused the delay in the time to metamorphosis and the decrease in the metamorphosed sizes. For example, for the continuously-fed larvae, duration to metamorphosis was 20.7d, for larvae with a size of 100-μm starved for up to 4d, larvae with a size of 140-μm starved for up to 16d, larvae with a size of 190-μm starved for up to 20d, duration to metamorphosis were 29.7, 31.7, and 37.7d, the delay in duration to metamorphosis were 9, 11, and 17d, respectively. Furthermore, importance of nutrition material for maintaining larval survival during starvation and the compensatory growth on larvae at the same feeding time were discussed. 相似文献
136.
根据OC-IΔD86基因序列, 设计合成了7条寡核苷酸片段, 通过重叠延伸PCR技术合成了OC-IΔD86基因, 利用设计好的BamH I/ Xho I酶切位点将OC-IΔD86基因克隆到原核表达载体pet21b中, 在1 mmol/L的IPTG 诱导后5 h, OC-IDD86融合基因在大肠杆菌中得到表达, 表达产物处于可溶状态, 其表达量占总蛋白的11.4%, 可溶性蛋白的16.4%; 利用Ni-NTA系统纯化该蛋白并经PEG20000浓缩后, 活性分析表明该蛋白酶抑制剂在体外表现出对木瓜蛋白酶明显的抑制作用。这为转OC-IΔD86基因的抗根结线虫植物基因工程抗体制备, 以及进一步体内的抗根结线虫研究奠定了基础。 相似文献
137.
138.
Yong Liang De-Yun Zhang Shuhong Ouyang Jingzhong Xie Qiuhong Wu Zhenzhong Wang Yu Cui Ping Lu Dong Zhang Zi-Ji Liu Jie Zhu Yong-Xing Chen Yan Zhang Ming-Cheng Luo Jan Dvorak Naxin Huo Qixin Sun Yong-Qiang Gu Zhiyong Liu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2015,128(8):1617-1629
139.
140.
Furazolidone‐containing triple and quadruple eradication therapy for initial treatment for Helicobacter pylori infection: A multicenter randomized controlled trial in China 下载免费PDF全文
Yong Xie Zhenyu Zhang Junbo Hong Wenzhong Liu Hong Lu Yiqi Du Weihong Wang Jianming Xu Xuehong Wang Lijuan Huo Guiying Zhang Chunhui Lan Xiaoyan Li Yanqing Li Hong Wang Guoxin Zhang Yin Zhu Xu Shu Ye Chen Jiangbin Wang Nonghua Lu the Chinese Society of Gastroenterology Chinese Study Group on Helicobacter pylori 《Helicobacter》2018,23(5)