全文获取类型
收费全文 | 1636篇 |
免费 | 106篇 |
专业分类
1742篇 |
出版年
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 33篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 46篇 |
2015年 | 60篇 |
2014年 | 66篇 |
2013年 | 92篇 |
2012年 | 114篇 |
2011年 | 106篇 |
2010年 | 84篇 |
2009年 | 44篇 |
2008年 | 76篇 |
2007年 | 73篇 |
2006年 | 80篇 |
2005年 | 76篇 |
2004年 | 58篇 |
2003年 | 62篇 |
2002年 | 71篇 |
2001年 | 26篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有1742条查询结果,搜索用时 15 毫秒
11.
Kees Nieuwenhuijsen Ad J. J. C. Lammers Karel J. de Neef A. Koos Slob 《International journal of primatology》1985,6(1):77-99
Reproductive physiology was studied in female stumptail macaques. Initially the monkeys were housed indoors (individually
and in small groups) and later as one large (92 individuals) social group in an outdoor cage. Most data were collected during
the 4-year outdoor period. Plasma progesterone determination in blood samples taken at weekly intervals allowed estimation
of ovulation and conception dates. The age at first ovulation (X =3.73 years) was positively correlated with body weight at 3 years of age. The average age at first birth was 4.90 years. Gestation
lengths averaged 176.6 days. Following a live birth ovulations returned after a mean interval of 11 months but following an
abortion or still birth this interval was 1 month. Usually a number of ovulatory cycles (X =2.37) preceded a conception. Interbirth intervals (IBIs) in the outdoor cage (X =619.4 days) were significantly longer than IBIs during the indoor period (X =523.1), because indoors the infants were weaned at the age of 7 months, while outdoors weaning occurred more naturally. IBIs
following abortions or still births (X =291.9 days) were significantly shorter than IBIs following live births. Age at first ovulation, age at first birth, IBIs,
and infant production rates were not correlated with dominance rank. Ovarian cycle lengths (X =30.2 days, mode = 28 days) were comparable to previously reported data from laboratory-housed stumptails. No systematic seasonal
fluctuations were found in the onset of sexual maturity, in ovarian cycle lengths, in copulation frequencies, and in distribution
of births. 相似文献
12.
RCA I-binding patterns of the Golgi apparatus 总被引:2,自引:0,他引:2
The distribution in the Golgi apparatus of binding sites for the galactose-specific Ricinus communis I lectin (RCA I) was studied in differently specialized cells, including goblet cells and absorptive enterocytes of the rat small intestine as well as acinar cells of the rat embryonic pancreas and submandibular gland. For the purpose of localizing the binding reactions, a pre-embedment method using horseradish peroxidase for electron microscopic visualization, and a post-embedding technique making use of the colloidal gold system were employed. The reactions obtained, localizing cell constituents which contain saccharides with terminal or internal beta-D-galactosyl residues, labeled diverse Golgi subcompartments. The goblet cells showed intense RCA I staining of the cisternae of the trans side of the Golgi stacks. The reaction was weak in the medial cisternae and the cis side of the stacks mostly was devoid of label. In the absorptive cells, in addition to the RCA I reaction of trans Golgi elements, binding sites for this lectin were concentrated in the stacks' medial section. In the embryonic acinar cells, accessible galactosyl residues were either confined to the trans and/or medial cisternae, or distributed across elements of all the stacked saccules. In the latter stacks, the reactions mostly were weak in the cis cisternae and increased in intensity towards the trans side. As regards the respective labeling patterns, similar percentages were calculated for the early and late stages of development: they were approximately 62% for the pattern which showed RCA I label limited to trans/medial cisternae and approximately 38% for the "cis-to-trans"-distributed RCA I reaction.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
13.
14.
Karel Mikulík Anna Jiráňová Jaroslav Weiser Ivan Janda Jana Šťastná Nguyen Quyen 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(1):99-107
Slowly cooled cells of Streptomyces aureofaciens contained mainly tight-couple ribosomes. Maximum rate of polyphenylalanine synthesis on ribosomes of S. aureofaciens was observed at 40°C, while cultures grew optimally at 28°C. Ribosomes of S. aureofaciens differed from those of E. coli in the amount of poly(U) required for maximum synthetic activity. The polyphenylalanine-synthesizing activity of E. coli ribosomes was about 3-times higher than that of S. aureofaciens ribosomes. The addition of protein S1 of E. coli or the homologous protein from S. aureofaciens had no stimulatory effect on the translation of poly(U). In order to localize alteration(s) of S. aureofaciens ribosomes in the elongation step of polypeptide synthesis we developed an in vitro system derived from purified elongation factors and ribosomal subunits. The enzymatic binding of Phe-tRNA to ribosomes of S. aureofaciens was significantly lower than the binding to ribosomes of E. coli. This alteration was mainly connected with the function of S. aureofaciens 50 S subunits. These subunits were not deficient in their ability to associate with 30 S subunits or with protein SL5 which is homologous to L7/L12 of E. coli. 相似文献
15.
Karel Rataj 《Folia Geobotanica》1970,5(2):213-216
In recent years 4 species of the genusEchinodorus have been imported in large quantities to Europe from Southern Brazil, being cultivated as decorative plants in aquaria. In spite of the fact that up to now not all organs from these plants are known, they differ so greatly from the known species by character of the submersed leaves that there is no doubt that the species, in question, viz.E. osiris, E. opacus, E. horemani andE. portoalegrensis, are new. 相似文献
16.
Karel Lenhart 《Mycopathologia》1968,36(2):150-160
Summary 1) The spores of the microconidial mutant I–18 of the dermatophyteMicrosporon gypseum in agar medium with GF germinated and formed germ tubes deformated in a characteristic way. From 1µg GF/ml up with an increasing antibiotic concentration (expressed in logarithms) the munber of colonies grown (expressed in probits) decreased linearly.2) As a sensitivity measure of the spores the median efficient dose ED 50 was used which was determined by means of a graphic probit analysis. For the strain used this value was determined in the range between 1.35–1.95µg GF/ml in three independent experiments.3) From the smears of a thickened spore suspension (1.6–14.2 × 107 viable spores) in medium containing a high GF concentration a very small, but as for the order a stable number of colonies grew, as found in eight independent experiments. On the medium containing 20µg GF/ml in average 61 colonies grew, on 40µg GF/ml 20 colonies, on 80µg GF/ml 3 colonies and on 160µg GF/ml 0.3 colony (expressed in 107 viable spores tested).4) A part of these colonies were isolated and transferred 29 times on a medium without the antibiotic. Two isolates only show a permanently increased resistance to GF, viz. the strain D-29 which is 50 × more resistant and the strain N-53 which is 3.5 × more resistant than the wild strain I-18. 相似文献
17.
Karel Beneš 《Biologia Plantarum》1962,4(1):61-68
V této práci byly aplikovány na rostlinných objektech reakce s β-oxynaftyl-merkurichloridem a p-nitrobromacetofenonem, popsané k pr?kazu bílkovinných SH na materiálu ?ivo?i?ném. V rostlinných meristematických buňkách obě tyto techniky stejně jako DDD1 a RSR1 jeví vět?inou intensivněj?í zbarvení jader ne? cytoplasmy. Rovně? po aplikaci reakcí na bílkovinné karboxyly a tyrosin je jádro intensivněji zbarveno ne? cytoplasma. Z toho lze soudit, ?e rozdíly v intensitě zbarvení jádra a cytoplasmy v meristematických buňkách rostlinných technikami k pr?kazu bílkovinných SH jsou zp?sobeny spí? rozdílem v celkové koncentraci bílkovin ne? zv??ením podílu cysteinu v jaderných bílkovinách. 相似文献
18.
Calamagrostis villosa stands occurring in areas deforested by air-pollution impact in the Moravian-Silesian Beskydy Mountains were characterized by a high dry mass of total underground biomass (3 300 g. m?2—the slope site, 2 850 g. m?2—the flat site). The percentage of living roots and rhizomes in total underground biomass was very high (about 70%). The total aboveground biomass was respectively, 321 g.m?2 (the slope site) and 726 g. m?2 (the flat site). In unstabilized habitats on steep slope, the higher plant biomass produced was allocated to a more developed root system. 相似文献
19.
20.
Ellen A. Meijer Sacco C. de Vries Peter Sterk Dorus W. J. Gadella Jr. Karel W. A. Wirtz Theo Hendriks 《Molecular and cellular biochemistry》1993,123(1-2):159-166
The extracellular protein EP2 was previously identified as non-specific lipid transfer protein based on its cDNA-derived amino acid sequence. Here, the purification of the EP2 protein from the medium of somatic embryo cultures is described. After two cycles of ion-exchange and gel permeation chromatography, a single silver-stained protein band with an apparent molecular mass of 10 kDa was observed on SDS-PAGE. This protein band was recognized by the antiserum raised against a EP2--galactosidase fusion-protein. Employing a fluorescent phospholipid analog, it was shown that the purified EP2 protein is capable of binding phospholipids and is able to enhance their transfer between artificial membranes. Employing a gel permeation assay, it could be demonstrated that the EP2 protein is also capable of binding palmitic and oleic acid as well as oleyl-CoA. Because in plants these fatty acids are used as precursor molecules for cutin, these results are in support of the proposed role of the EP2 protein to transport cutin monomers from their site of synthesis through the cell wall of epidermal cells to sites of cutin polymerization. 相似文献