全文获取类型
收费全文 | 15904篇 |
免费 | 1577篇 |
国内免费 | 3116篇 |
出版年
2024年 | 60篇 |
2023年 | 271篇 |
2022年 | 519篇 |
2021年 | 776篇 |
2020年 | 688篇 |
2019年 | 752篇 |
2018年 | 639篇 |
2017年 | 542篇 |
2016年 | 689篇 |
2015年 | 1046篇 |
2014年 | 1300篇 |
2013年 | 1255篇 |
2012年 | 1631篇 |
2011年 | 1491篇 |
2010年 | 970篇 |
2009年 | 922篇 |
2008年 | 1045篇 |
2007年 | 930篇 |
2006年 | 879篇 |
2005年 | 679篇 |
2004年 | 572篇 |
2003年 | 484篇 |
2002年 | 392篇 |
2001年 | 309篇 |
2000年 | 284篇 |
1999年 | 224篇 |
1998年 | 156篇 |
1997年 | 130篇 |
1996年 | 98篇 |
1995年 | 105篇 |
1994年 | 113篇 |
1993年 | 70篇 |
1992年 | 81篇 |
1991年 | 77篇 |
1990年 | 45篇 |
1989年 | 51篇 |
1988年 | 37篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 41篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1978年 | 10篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1973年 | 8篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
21.
Kunio Takeda Atsuya Shigemura Satoshi Hamada Weicheng Gu Defu Fang Katsushi Sasa Kazuaki Hachiya 《Journal of Protein Chemistry》1992,11(2):187-192
The effect of protein conformations on the reaction rate of Ellman's reagent, 5,5-dithiobis (2-nitrobenzoic acid) (DTNB) with sulfhydryl (SH) groups of proteins was examined. The stopped-flow method was applied to follow the reaction of DTNB with SH group of two proteins, bovine serum albumin (BSA) and ovalbumin (OVA), at various concentrations of guanidine hydrochloride and urea. The rates for both the proteins were faster in guanidine than in urea. The rate sharply depended on the protein conformations, which were monitored by changes of helix contents on the basis of the circular dichroism measurements. The reaction rate of DTNB with SH groups of BSA was maximal around 2 M guanidine and 5 M urea. On the other hand, the reaction rate of DTNB with OVA was maximal at 3.5 M guanidine, while it gradually increased with an increase in the urea concentration. The amount of reactive SH group participating in the reaction with DTNB was also estimated by the absorbance change at 412 nm. The magnitudes of absorbance change for the reaction with free SH groups of OVA at low concentrations of the denaturants were appreciably smaller than those for BSA with one free SH group. Most of the four SH groups of OVA might react with DTNB above 5 M guanidine, although only a part of them did even at 9 M urea. 相似文献
22.
23.
24.
Evidence that the G1-S and G2-M transitions are controlled by different cdc2 proteins in higher eukaryotes. 总被引:71,自引:0,他引:71
Xenopus eggs contain two distinct cdc2 homologs of 34 and 32 kd. We show that the 32 kd cdc2 protein, like the 34 kd protein, is a kinase. However, unlike the 34 kd homolog, the 32 kd cdc2 kinase activity does not decrease dramatically at the end of mitosis. The 32 kd protein does not associate with mitotic cyclins B1 and B2 but does associate with cyclin A and a novel doublet of proteins of 54 kd that may regulate its activity. We also show that depletion of the 32 kd cdc2 homolog from a Xenopus extract blocks DNA replication, but does not inhibit entry into mitosis. By contrast, depletion of the 34 kd cdc2 homolog or absence of mitotic cyclins from an extract does not inhibit replication, but does block entry into mitosis. Our results indicate that in higher eukaryotes, DNA replication (G1-S) and mitosis (G2-M) may be controlled by distinctly different cdc2 proteins. 相似文献
25.
Rong-Xiang Fang Zhen Pang Dong-Ming Gao Ke-Qiang Mang Nam-Hai Chua 《Plant molecular biology》1991,17(6):1255-1257
26.
M. Yang Fang Ming J. Hubble A. D. Lockett R. R. Rathbone J. A. Howell 《Biotechnology Techniques》1992,6(5):409-412
A simple thermal monitoring technique has been successfully applied to an adsorption system using a novel ion exchanger with
a large internal void volume (voidage) which can be operated at high superficial velocity (SV). Temperature changes resulting
from heats of adsorption could be followed effectively using semi-conductor thermistor devices inserted into the resin through
the column wall. Results show that, despite the high feed rates adopted, the thermal signals generated can be consistently
related to the position of the breakthrough front within the bed. 相似文献
27.
世界蚜虫分类研究进展 总被引:4,自引:0,他引:4
本文综述了世界蚜虫分类研究进展。内容包括形态分类、细胞分类、生物化学分类以及化石研究等,并以M.L.Sharma的文献目录为基础,对世界蚜虫分类研究报告篇数进行统计。结果表明:世界各国蚜虫分类研究进展极不平衡,美国、加拿大、日本及欧洲的一些国家包括荷兰、丹麦、瑞典、捷克、波兰、德国等其α分类任务基本完成,印度也进展较快,离完成α分类任务为期不远。苏联欧洲部分也已基本完成,亚洲部分和中国尚有大量α级分类工作有待完成。 相似文献
28.
29.
30.