全文获取类型
收费全文 | 11346篇 |
免费 | 549篇 |
国内免费 | 1篇 |
专业分类
11896篇 |
出版年
2021年 | 109篇 |
2020年 | 83篇 |
2019年 | 108篇 |
2018年 | 322篇 |
2017年 | 278篇 |
2016年 | 352篇 |
2015年 | 261篇 |
2014年 | 389篇 |
2013年 | 678篇 |
2012年 | 807篇 |
2011年 | 1028篇 |
2010年 | 595篇 |
2009年 | 264篇 |
2008年 | 581篇 |
2007年 | 521篇 |
2006年 | 506篇 |
2005年 | 364篇 |
2004年 | 304篇 |
2003年 | 309篇 |
2002年 | 242篇 |
2001年 | 156篇 |
2000年 | 235篇 |
1999年 | 176篇 |
1998年 | 141篇 |
1997年 | 83篇 |
1996年 | 94篇 |
1995年 | 92篇 |
1994年 | 102篇 |
1993年 | 91篇 |
1992年 | 89篇 |
1991年 | 98篇 |
1989年 | 66篇 |
1988年 | 83篇 |
1987年 | 73篇 |
1985年 | 99篇 |
1984年 | 84篇 |
1983年 | 84篇 |
1982年 | 88篇 |
1981年 | 92篇 |
1980年 | 92篇 |
1979年 | 80篇 |
1978年 | 82篇 |
1976年 | 71篇 |
1975年 | 79篇 |
1974年 | 93篇 |
1973年 | 66篇 |
1972年 | 75篇 |
1970年 | 62篇 |
1969年 | 70篇 |
1968年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Jaroslav Dršata Martin Beránek VladimÍr Palička 《Journal of enzyme inhibition and medicinal chemistry》2013,28(1):31-36
Incubation of 50 mM d -glucose with aspartate aminotransferase (AST, EC 2.6.1.1) preparations (purified pig heart enzyme or a rat liver 20,000 × g supernatant) at 25°C had no effect on enzyme activity. 50 mM d -fructose or d -ribose gradually inhibited pig heart AST under the same conditions to zero activity after 14 days. 50 mM dl -glyceraldehyde decreased enzyme activity to zero after 6 days of incubation. The inhibition of pig heart AST by 50 mM d -fructose or d -ribose was marked even at a temperature of 4°C but it was less pronounced than at 25°C. There was no effect of 0.5 mM 2-oxoglutarate on AST activity during incubation, while the presence of 25 mM l -aspartate decreased it rapidly. 0.5 mM 2-oxoglutarate partly prevented inhibition of AST by d -ribose or d -fructose, while an analogous experiment with 25 mM aspartate resulted in a rapid decline similar to that in the absence of sugars. 相似文献
12.
13.
Ruth Duncan Pavla Rejmanova Jindrich Kopeček John B. Lloyd 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(1):143-150
Synthetic 125I-labelled N-(2-hydroxypropyl)methacrylamide copolymers containing four different, potentially degradable peptidyl side chains were incubated with rat visceral yolk sacs cultured in vitro. All copolymers were captured by fluid-phase pinocytosis and three of the side chains were susceptible to lysosomal hydrolysis, resulting in release of [125I]iodotyrosine back into the culture medium. Uptake and degradation was completely inhibited by 2,4-dinitrophenol. The thiol-proteinase inhibitor leupeptin did not affect the rate of pinocytosis, but caused different degrees of inhibition of hydrolysis depending on side chain composition. 相似文献
14.
F. Šrámek 《Biologia Plantarum》1999,42(4):582-582
15.
16.
17.
M. Konečná 《Zeitschrift fur angewandte Ichthyologie》2012,28(5):806-810
This study focuses on assessing the reproduction mode of an important model species for evolutionary and behavioural ecology by using digital image analysis: the European bitterling Rhodeus amarus (Bloch, 1782). Specifications of mode of reproduction were determined using oocyte size distribution, seasonal dynamics in mean oocyte diameter and total number of oocytes in ovary samples gained from April to July 2007. The rapid oocyte count was enabled by using lucia image analysis software, which also provided measurement and colour estimations of oocytes. Bitterling ovaries showed features typical for indeterminate spawners, i.e. a continuous distribution of oocyte size over the reproductive season and recruitment of new pre‐vitelogenic oocytes in the second half of the reproductive season. These results are consistent with the view that the European bitterling is a batch spawning fish with indeterminate fecundity. 相似文献
18.
J. Nečas 《Biologia Plantarum》1970,12(5):359-367
Populations of theChloretta vulgaris Beijeb. strain ?esnokov “V” clones (progenies of single cells) grown up from cells treated by chemical mutagens were cultivated on the surface of solid media. The differentiation of growth types according to their growth rates in the populations originating from the same sample of cells but growing under different conditions was compared. The strain studied exhibited much greater growth rate variability on the complete medium than on the minimal one. Short time changes of light regime during the cultivation for the purpose of inducing reparation processes in the mutagen damaged cells did not manifest themselves significantly in the composition of resulting clonal populations. The possibility of selection of growth types under conditions studied was considered. 相似文献
19.
Hana Votavová Vladimír Gut Karel Bláha Jaroslav Šponar 《International journal of biological macromolecules》1982,4(6):341-346
DNA complexes with polypeptides (Lys-Ala-Ala)1)] and (Lys-Ala-Ala)34 have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)10 DNA differed substantially from those of (Lys-Ala-Ala)34 prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with Tm increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with Tm values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)10-DNA system but a slow redistribution of (Lys-Ala-Ala)34 on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding. 相似文献
20.
The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium. 相似文献