全文获取类型
收费全文 | 88117篇 |
免费 | 5528篇 |
国内免费 | 10篇 |
专业分类
93655篇 |
出版年
2023年 | 574篇 |
2022年 | 519篇 |
2021年 | 1133篇 |
2020年 | 1019篇 |
2019年 | 1078篇 |
2018年 | 2630篇 |
2017年 | 2370篇 |
2016年 | 3183篇 |
2015年 | 4121篇 |
2014年 | 4133篇 |
2013年 | 5649篇 |
2012年 | 6613篇 |
2011年 | 5993篇 |
2010年 | 3745篇 |
2009年 | 2863篇 |
2008年 | 4648篇 |
2007年 | 4476篇 |
2006年 | 4340篇 |
2005年 | 3648篇 |
2004年 | 3575篇 |
2003年 | 3210篇 |
2002年 | 2986篇 |
2001年 | 2125篇 |
2000年 | 2100篇 |
1999年 | 1600篇 |
1998年 | 672篇 |
1997年 | 475篇 |
1996年 | 497篇 |
1995年 | 478篇 |
1994年 | 380篇 |
1993年 | 333篇 |
1992年 | 899篇 |
1991年 | 777篇 |
1990年 | 703篇 |
1989年 | 706篇 |
1988年 | 666篇 |
1987年 | 628篇 |
1986年 | 589篇 |
1985年 | 581篇 |
1984年 | 528篇 |
1983年 | 406篇 |
1982年 | 351篇 |
1979年 | 440篇 |
1978年 | 337篇 |
1975年 | 329篇 |
1974年 | 378篇 |
1973年 | 381篇 |
1972年 | 340篇 |
1970年 | 319篇 |
1969年 | 321篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
1. Within the range of the given conditions of measuring static and dynamic properties of the rabbit gastrocnemius muscle the following results were obtained: a) the dependence of the maxima of isotonic shortening upon the relative length of the muscle at constant load is linear; b) the parameters of the non-linear dependence of the passive elastic force of the muscle upon its relative length (measured in series) were identified using asymptotic regression; c) the time course of isotonic contractions (at an interval from 0 to 0.3 s after the beginning of stimulation) could be satisfactorily approximated by responses of a linear system to a step-function; d) the time course of isometric contractions (at an interval from 0 to 0.3 s after the beginning of stimulation) could be closely approximated by responses of a linear system to a step-function. 2. The time constants of isotonic and isometric contractions were determined as the parameters of the corresponding linear systems. 3. The maximum rates of the isometric and isotonic contractions were determined as maxima of the first derivatives of the responses of the corresponding models. 4. The experimental set-up made it possible to compare the values of the parameters concomitantly followed at various muscle lengths and at various loads. 相似文献
103.
J Ignacio Andrés Jesús Alcázar José M Alonso Adolfo Díaz Javier Fernández Pilar Gil Laura Iturrino Encarna Matesanz Theo F Meert Anton Megens Victor K Sipido 《Bioorganic & medicinal chemistry letters》2002,12(2):249-253
Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described. 相似文献
104.
105.
106.
Using reversed-phase high-performance liquid chromatography with electrochemical detection we have demonstrated the occurrence of 5,6,7,8-tetrahydropterin and 5,6,7,8-tetrahydrobiopterin in Drosophila melanogaster. The former is the first time that has been detected in vivo. The identification has been based on the retention times, hydrodinamic voltagrams and the differential concentration in three strains of Drosophila melanogaster. Compared to the wild type, the Punch2 mutant has diminished levels of both pteridines, whereas Henna-recessive3 lacks completely tetrahydropterin and has increased levels of tetrahydrobiopterin, as expected according to their biochemical lesions. 相似文献
107.
Effect of auto-oxidized phospholipids on oxidative enzyme assays based on tetrazolium salt reduction
The influence of auto-oxidized phospholipids on the reduction of the tetrazolium salt MTT coupled to the NAD+-dependent lactate dehydrogenase reaction was studied. The following results were obtained: (1) peroxidized phosphatidylcholine interfered in the time-course of the lactate dehydrogenase-mediated MTT reduction; (2) there was a time-dependent decrease in the hydroperoxide content of phosphatidylcholine vesicles during the incubation; (3) the diminution of phosphatidylcholine hydroperoxides required the presence of all the components of the system except MTT; (4) hydroperoxide diminution and MTT reduction were mediated by the superoxide radical O2-, since both processes were inhibited by superoxide dismutase; (5) EDTA inhibited the hydroperoxide decrease and abolished the interference of peroxidized phosphatidylcholine with MTT reduction. It was concluded that hydroperoxides compete with MTT for the electrons coming from substrate oxidation. The superoxide radical O2- and traces of some contaminating metal ion are involved in the process. This is a potential complication in the study of the effect of lipids on enzymatic activities assayed by the tetrazolium salt method. 相似文献
108.
The expression of murine leukemia virus (MuLV)-related antigens in oocytes and early embryos of Swiss mice was studied by the unlabeled antibody peroxidase-antiperoxidase method using an antiserum to the major core protein, p30, of AKR MuLV. This procedure resulted in an intense staining, at antibody dilutions up to 1:500, of the germinal vesicles of oocytes and the interphase nuclei of early embryos. Nuclear staining was restricted to a specific period of oocyte growth and embryo development. It developed gradually in oocytes having reached one third to one half the full-grown size and persisted until meiotic maturation. In early embryos, nuclear staining was present from the one-cell stage to the morula, but disappeared during transition from morula to blastocyst and was not seen in expanded blastocysts. Nuclear staining was abolished by absorption of the anti-p30 serum with detergent-disrupted virions of Gross(A), AKR, Kirsten and Moloney MuLV, and Kirsten MSV(MuLV), but not with the Friend and Rauscher strains of MuLV, the xenotropic BALB:virus 2, a mouse tropic and an amphotropic clone of wild mouse MuLV, or with FeLV and RSV. On the basis of these results, it is suggested that the nuclear antigen (termed germinal vesicle antigen) reacting with the anti-p30 serum is the product of a cellular gene having a normal function in early embryonic development, and that sequences related to this gene are incorporated into the genome of AKR-type MuLV. 相似文献
109.
Preincubation of resting cells of Saccharomyces cerevisiae double mutant can1 gap1 (with a single transport system for L-lysine) with metabolic substrates stimulated subsequent uptake of lysine. While in the wild type the stimulation is connected primarily with carrier protein synthesis (delayed, cycloheximide-inhibitable effect) in the mutant an immediate tapping of an energy source (antimycin-inhibited) is practically solely involved. 相似文献
110.