全文获取类型
收费全文 | 484233篇 |
免费 | 164238篇 |
国内免费 | 29765篇 |
专业分类
678236篇 |
出版年
2018年 | 6242篇 |
2016年 | 7516篇 |
2015年 | 9288篇 |
2014年 | 10609篇 |
2013年 | 13600篇 |
2012年 | 15528篇 |
2011年 | 16404篇 |
2010年 | 13449篇 |
2009年 | 17422篇 |
2008年 | 15809篇 |
2007年 | 16114篇 |
2006年 | 14313篇 |
2005年 | 13808篇 |
2004年 | 13809篇 |
2003年 | 12719篇 |
2002年 | 13193篇 |
2001年 | 21215篇 |
2000年 | 19157篇 |
1999年 | 19769篇 |
1998年 | 12711篇 |
1997年 | 12727篇 |
1996年 | 11835篇 |
1995年 | 11866篇 |
1994年 | 11236篇 |
1993年 | 10971篇 |
1992年 | 17957篇 |
1991年 | 17938篇 |
1990年 | 18354篇 |
1989年 | 17377篇 |
1988年 | 16271篇 |
1987年 | 15124篇 |
1986年 | 14078篇 |
1985年 | 13476篇 |
1984年 | 11034篇 |
1983年 | 9348篇 |
1982年 | 8140篇 |
1981年 | 7291篇 |
1980年 | 7062篇 |
1979年 | 10108篇 |
1978年 | 8308篇 |
1977年 | 7801篇 |
1976年 | 7409篇 |
1975年 | 7497篇 |
1974年 | 8412篇 |
1973年 | 8274篇 |
1972年 | 8136篇 |
1971年 | 7420篇 |
1970年 | 6619篇 |
1969年 | 6567篇 |
1968年 | 6082篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
E A Ivanova 《Ontogenez》1987,18(3):320-323
The influence of testosterone on the rate of total protein synthesis in the reproductive tract tissues and muscles was studied in the guinea pig male embryos from 26 days of development until birth. The rate of protein synthesis was estimated by the intensity of 3H-leucine incorporation per 1 mg protein for 30 min. Testosterone increased the rate of protein synthesis at all studies stages. A higher rate of protein synthesis was revealed at the stages of active morphogenesis and growth of rudiments and organs of genital system and correlated with their ability of 3H-testosterone uptake (Ivanova, 1982). 相似文献
992.
Binding of ADP to beef-heart mitochondrial ATPase (F1) 总被引:1,自引:0,他引:1
1. ADP binding to beef-heart mitochondrial ATPase (F1), in the absence of Mg2+, has been determined by separating the free ligand by ultrafiltration and determining it in the filtrate by a specially modified isotachophoretic procedure. 2. Since during the binding experiments the 'tightly' bound ADP (but not the ATP) dissociates, it is necessary to take this into account in calculating the binding parameters. 3. The binding data show that only one tight binding site (Kd about 0.5 microM) for ADP is present. 4. It is not possible to calculate from the binding data alone the number of or the dissociation constants for the weak binding sites. It can be concluded, however, that the latter is not less than about 50 microM. 相似文献
993.
U. Behrens N. Fedoroff A. Laird M. Müller-Neumann P. Starlinger J. Yoder 《Molecular & general genetics : MGG》1984,194(1-2):346-347
Summary The cloning of the controlling element Ac from the wx-m7 allele of Zea mays is described. The cloned fragment carries a 4.3 kb insertion that by restriction analysis is indistinguishable from the Ac insertion in Ac wx-m9. It is located approximately 2.5 kb upstream of the Ac wx-m9 insertion.
Offprint requests to: P. Starlinger 相似文献
994.
A method of retaining phloroglucinol proof of lignin 总被引:2,自引:0,他引:2
E O Speer 《Stain technology》1987,62(4):279-280
995.
D. Y. Sorokin E. N. Detkova G. Muyzer 《Extremophiles : life under extreme conditions》2010,14(1):71-77
Evidence on the utilization of simple fatty acids by sulfate-reducing bacteria (SRB) at extremely haloalkaline conditions are practically absent, except for a single case of syntrophy by Desulfonatronum on acetate. Our experiments with sediments from soda lakes of Kulunda Steppe (Altai, Russia) showed sulfide production with sulfate as electron acceptor and propionate and butyrate (but not acetate) as an electron donor at a pH 10–10.5 and a salinity 70–180 g l?1. With propionate as substrate, a highly enriched sulfidogenic culture was obtained in which the main component was identified as a novel representative of the family Syntrophobacteraceae. With butyrate as substrate, a pure SRB culture was isolated which oxidized butyrate and some higher fatty acids incompletely to acetate. The strain represents the first haloalkaliphilic representative of the family Desulfobacteraceae and is described as Desulfobotulus alkaliphilus sp. nov. 相似文献
996.
H. E. Webb 《BMJ (Clinical research ed.)》1992,304(6837):1260-1261
997.
The evolution of the A family of chorion genes was examined by comparing new protein and DNA sequences from the silkmoths Antheraea pernyi and Bombyx mori with previously known sequences from Antheraea polyphemus. The comparisons indicated that the A family and its major subfamilies are ancient and revealed how parts of the genes corresponding to distinct regions of the protein structure have evolved, both by base substitutions and by segmental reduplications and deletions. 相似文献
998.
The chromosomes of the D genome of wheat and the genome R of rye can be distinguished at meiosis by C-banding in triticale-wheat hybrid plants. All members of both genomes almost exclusively formed univalents at metaphase I. However, at anaphase I the frequencies of equationally dividing chromosomes were higher for rye than for wheat chromosomes. The differential centromere behaviour at anaphase I is ascribed to differences in the time at which wheat and rye univalents are formed during the first meiotic prophase. 相似文献
999.
From six to 89 months after surgery 82 patients who had been treated by radical surgery (118 excisions) for intractable hidradenitis suppurativa were reviewed. Local recurrence rates varied greatly with the disease site, being low after axillary (3%) and perianal surgery (0%) and high after inguinoperineal (37%) and submammary (50%) excision. Recurrence results from inadequate excision or an unusually wide distribution of apocrine glands, but physical factors such as obesity, local pressure, and skin maceration played a part in a few patients. Recurrence due to inadequate surgery tended to be the most troublesome. At follow up 75 (91%) of the patients were pleased with the results of their operation. A quarter of the patients developed disease at a new anatomical site after operation. Radical surgery gives good symptomatic control of severe hidradenitis suppurativa of the axilla, inguinoperineal, and perianal regions but is less satisfactory for submammary disease. 相似文献
1000.
Stability of o-phthalaldehyde-derived isoindoles 总被引:1,自引:0,他引:1
The degradation of 1-alkylthio-2-alkylisoindoles, generated in situ by reaction of o-phthalaldehyde with primary alkylamines in the presence of selected thiols, was studied under conditions typical of those used in precolumn derivatization applications. In all cases, loss of isoindole followed pseudo first order kinetics and was strongly accelerated by excess o-phthalaldehyde in the reaction mixture. Reactivity toward o-phthalaldehyde was found to be influenced by a number of experimental parameters including thiol structure, thiol concentration, amine structure, solvent composition, and pH. In the absence of excess o-phthalaldehyde, the stability of all derivatives examined was excellent. These results provide a basis for optimization of reaction conditions for maximum derivative stability. 相似文献