全文获取类型
收费全文 | 7385篇 |
免费 | 563篇 |
国内免费 | 544篇 |
出版年
2024年 | 10篇 |
2023年 | 105篇 |
2022年 | 254篇 |
2021年 | 446篇 |
2020年 | 256篇 |
2019年 | 323篇 |
2018年 | 284篇 |
2017年 | 243篇 |
2016年 | 315篇 |
2015年 | 434篇 |
2014年 | 530篇 |
2013年 | 545篇 |
2012年 | 661篇 |
2011年 | 563篇 |
2010年 | 332篇 |
2009年 | 351篇 |
2008年 | 379篇 |
2007年 | 305篇 |
2006年 | 283篇 |
2005年 | 209篇 |
2004年 | 219篇 |
2003年 | 214篇 |
2002年 | 136篇 |
2001年 | 136篇 |
2000年 | 128篇 |
1999年 | 143篇 |
1998年 | 83篇 |
1997年 | 70篇 |
1996年 | 82篇 |
1995年 | 72篇 |
1994年 | 61篇 |
1993年 | 31篇 |
1992年 | 62篇 |
1991年 | 43篇 |
1990年 | 40篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 28篇 |
1986年 | 16篇 |
1985年 | 33篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有8492条查询结果,搜索用时 15 毫秒
31.
利福霉素生产菌产生钝化RifSV物质的分离及性质研究 总被引:1,自引:0,他引:1
利福霉素SV(简称RifSV)生产菌──地中海拟无枝菌酸菌在生物合成RifSV过程中,产生一种能钝化自身产物(RifSV)的物质.实验证实,该物质是由谷氨酸、天冬氨酸、赖氨酸及缬氨酸等14种常见氨基酸组成的蛋白质.分子量(MW)约2.5×104D,等电点(PI)为5.7—6.1.在100℃下加热10min,其活性丧失.作用于RifSV的最适pH值范围为7.4—8.6,最适温度为29℃,初步证实该物质是一种酶(暂称利福霉素钝化酶) 相似文献
32.
33.
大瓶螺碱性磷酸酶的分离纯化及部分性质研究李清漪,曾和期(西南师范大学生物系,重庆630715)碱性磷酸酶(EC3.1.3.1,简称AKP)是广泛存在于动物组织中的水解酶。对软体动物中AKP的研究仅有少数报道[1,2],对属于单壳贝类的水生食用螺──大... 相似文献
34.
B. O. Solomon A. -P. Zeng H. Biebl A. O. Ejiofor C. Posten W. D. Deckwer 《Applied microbiology and biotechnology》1994,42(2-3):222-226
Product formation during anaerobic degradation of glycerol byKlebsiella pneumoniae DSM 2026, under glycerol limitation and glycerol excess in continugius cultures, has been investigated. Major and minor products and by-products as well as gaseous products were measured. The results indicated a positive correlation between specific glycerol uptake and most product formation rates under glycerol limitation. The production of 1,3-propanediol, lactate, formate, acetate, succinate and the by-products of anaerobic glycerol degradation byK. pneumoniae, acetoin and 2,3-butanediol, was favoured by glycerol excess, while hydrogen generation and ethanol formation were best under glycerol limitation. It was also found that under glycerol limitation the rate of hydrogen evolution was generally higher than the CO2 production rate while under excess glycerol the reverse was true. Hence, on the basis of the ratio of the specific rates of evolution of H2 and CO2 (q
H
2/q
CO
2), it is possible to infer the existence of glycerol limitation. On the basis of the carbon and available electron balances, which are independent of metabolic pathways, the data are consistent. The NADH2 balance, which took into consideration the pathways of product formation, was also tested to check the validity of the assumed pathways and to check critically the consistency of the data. Good balances were also obtained.[ 相似文献
35.
36.
D Chen C Q Zeng M J Wentz M Gorziglia M K Estes R F Ramig 《Journal of virology》1994,68(11):7030-7039
37.
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
38.
The Golgi complexes of animal cells are said to become vesicular during cell division in order to allow the equal partitioning of organelles between daughter cells (Warren, 1985). However, in the epidermis of fifth stage larval Calpodes ethlius (Lepidoptera, Hesperi idae), cutical deposition is concurrent with cell division in preparation for pupation. We therefore looked at the Golgi complexes of these epidermal cells to see if they maintained their interphase form to allow them to continue to function during cell division. Dividing cells were recognized by changes in the nucleus and nuclear envelope, the form of the cell cortex and cell surface, and by the disposition of microtubules. Epidermal Golgi complexes consist of 3-5 cisternae capped by endoplasmic reticulum with transfer vesicles and rings of GC beads next to the cis face, and secretory vesicles on the trans face. Golgi complexes of dividing cells are structurally indistinguishable from those in interphase, their beads are in the rings characteristic of active GCs, and cuticle continues in uninterrupted lamellae above the apical microvilli. The observations suggest that Golgi complexes in dividing insect cells differ from those of most vertebrates by remaining functional through mitosis. 相似文献
39.
1989—1991年对黄麻栽培种圆果种(Corchoruscapsularis)和长果种(C.olit-orius)选用了具有不同茎色和腋芽性状的材料做了6个组合,获得134株杂种F_1苗。但苗株发根不良,在移栽后两周陆续死亡,最后幸存RR-5×(BL×77-19)F_1组合中两株植株并开花、结果。F_1均有腋芽,表现为父本的性状;花果形状偏向母本;茎色红同双亲。这两株的F_2,茎色和腋芽性状分离成4种表现型:红茎或青茎有腋芽及红茎或青茎无腋芽。其中红茎有腋芽的生长较快。对种间杂交技术、亲本间的花粉与柱头亲和性、杂交花的胚珠受精情况及染色体构型等方面也作了观察、研究。 相似文献
40.
本文应用系统分析方法,建立了一种一级吸收药物的生物利用度的简便估计的两点法。这种方法,只需测量血管内和血管外给药后的两个相同时点的血药浓度值。不论该药的处置系统是多少室,均能得到较好的结果。这种方法不仅比目前常用的点一点法和点一面法简单,而且结果更精确。 相似文献