全文获取类型
收费全文 | 11339篇 |
免费 | 598篇 |
国内免费 | 538篇 |
出版年
2024年 | 18篇 |
2023年 | 110篇 |
2022年 | 175篇 |
2021年 | 196篇 |
2020年 | 234篇 |
2019年 | 265篇 |
2018年 | 308篇 |
2017年 | 225篇 |
2016年 | 276篇 |
2015年 | 265篇 |
2014年 | 484篇 |
2013年 | 597篇 |
2012年 | 326篇 |
2011年 | 465篇 |
2010年 | 409篇 |
2009年 | 574篇 |
2008年 | 597篇 |
2007年 | 631篇 |
2006年 | 579篇 |
2005年 | 550篇 |
2004年 | 499篇 |
2003年 | 410篇 |
2002年 | 440篇 |
2001年 | 286篇 |
2000年 | 209篇 |
1999年 | 264篇 |
1998年 | 299篇 |
1997年 | 238篇 |
1996年 | 280篇 |
1995年 | 217篇 |
1994年 | 227篇 |
1993年 | 160篇 |
1992年 | 173篇 |
1991年 | 165篇 |
1990年 | 125篇 |
1989年 | 133篇 |
1988年 | 111篇 |
1987年 | 102篇 |
1986年 | 93篇 |
1985年 | 111篇 |
1984年 | 121篇 |
1983年 | 78篇 |
1982年 | 96篇 |
1981年 | 81篇 |
1980年 | 77篇 |
1979年 | 52篇 |
1978年 | 33篇 |
1977年 | 24篇 |
1976年 | 28篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 414 毫秒
1.
《Bioscience, biotechnology, and biochemistry》2013,77(9):2472-2475
Conjugational transfer of pLS20 in Bacillus subtilis Marburg 168 is restricted by the BsuM restriction-modification system. Restriction efficiency was measured using pLS20 derivatives possessing various numbers of XhoI sites, which are known to be recognized by BsuM. An increase in XhoI sites clearly reduced the conjugational efficiency of pLS20 as compared with that of pUB110 plasmid lacking XhoI. 相似文献
2.
Sandrine Poncet Armelle Delecluse Guido Anello ré Klier Georges Rapoport 《FEMS microbiology letters》1994,117(1):91-95
Abstract The genes encoding the CryIVB and CryIVD crystal polypeptides of B. thuringiensis subsp. israelensis were cloned indepently on a stable shuttle vector, and transfered into B. sphaericus 2297. Recombinant cells expressed the B. thuringiensis toxins during sporulation and were shown to be toxic to Aedes aegypti fourth instar larvae, whereas the parental strain was not. 相似文献
3.
Burt V. Bronk Joe D. Patton David N. Mellard 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,697(3):278-285
Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C. 相似文献
4.
5.
6.
《Journal of molecular biology》2021,433(22):167254
Tau is an intrinsically disordered protein implicated in many neurodegenerative diseases. The repeat domain fragment of tau, tau-K18, is known to undergo a disorder to order transition in the presence of lipid micelles and vesicles, in which helices form in each of the repeat domains. Here, the mechanism of helical structure formation, induced by a phospholipid mimetic, sodium dodecyl sulfate (SDS) at sub-micellar concentrations, has been studied using multiple biophysical probes. A study of the conformational dynamics of the disordered state, using photoinduced electron transfer coupled to fluorescence correlation spectroscopy (PET-FCS) has indicated the presence of an intermediate state, I, in equilibrium with the unfolded state, U. The cooperative binding of the ligand (L), SDS, to I has been shown to induce the formation of a compact, helical intermediate (IL5) within the dead time (∼37 µs) of a continuous flow mixer. Quantitative analysis of the PET-FCS data and the ensemble microsecond kinetic data, suggests that the mechanism of induction of helical structure can be described by a U ↔ I ↔ IL5 ↔ FL5 mechanism, in which the final helical state, FL5, forms from IL5 with a time constant of 50–200 µs. Finally, it has been shown that the helical conformation is an aggregation-competent state that can directly form amyloid fibrils. 相似文献
7.
《Developmental cell》2021,56(16):2329-2347.e6
8.
9.
Thermoanaerobacter brockii 《Anaerobe》1997,3(6)
Thermoanaerobacter brockiifermented serine to acetate and ethanol. It oxidized leucine to isovalerate, isoleucine to 2-methylbutyrate, and valine to isobutyrate only in the presence of thiosulfate, or when co-cultured withMethanobacteriumsp. This oxidative deamination was rendered thermodynamically possible by the ability ofT. brockiito reduce thiosulfate to sulfide or the transfer of reducing equivalents to the hydrogenotrophic methanogen. The results suggest thatT. brockiimay be of ecological significance in thermal environments in the turnover of amino acids, especially with thiosulfate or H2-utilizing methanogens are present. 相似文献
10.
Copper is an essential yet toxic metal ion. To satisfy cellular requirements, while, at the same time, minimizing toxicity,
complex systems of copper trafficking have evolved in all cell types. The best conserved and most widely distributed of these
involve Atx1-like chaperones and P1B-type ATPase transporters. Here, we discuss current understanding of how these chaperones bind Cu(I) and transfer it to the
Atx1-like N-terminal domains of their cognate transporter. 相似文献