全文获取类型
收费全文 | 7193篇 |
免费 | 515篇 |
国内免费 | 3篇 |
出版年
2022年 | 32篇 |
2021年 | 65篇 |
2020年 | 71篇 |
2019年 | 72篇 |
2018年 | 85篇 |
2017年 | 89篇 |
2016年 | 144篇 |
2015年 | 258篇 |
2014年 | 271篇 |
2013年 | 370篇 |
2012年 | 432篇 |
2011年 | 455篇 |
2010年 | 281篇 |
2009年 | 267篇 |
2008年 | 389篇 |
2007年 | 403篇 |
2006年 | 412篇 |
2005年 | 395篇 |
2004年 | 359篇 |
2003年 | 385篇 |
2002年 | 397篇 |
2001年 | 104篇 |
2000年 | 77篇 |
1999年 | 102篇 |
1998年 | 142篇 |
1997年 | 97篇 |
1996年 | 89篇 |
1995年 | 92篇 |
1994年 | 91篇 |
1993年 | 95篇 |
1992年 | 72篇 |
1991年 | 66篇 |
1990年 | 54篇 |
1989年 | 65篇 |
1988年 | 67篇 |
1987年 | 33篇 |
1986年 | 39篇 |
1985年 | 42篇 |
1984年 | 61篇 |
1983年 | 50篇 |
1982年 | 59篇 |
1981年 | 75篇 |
1980年 | 51篇 |
1979年 | 48篇 |
1978年 | 39篇 |
1977年 | 38篇 |
1976年 | 37篇 |
1975年 | 41篇 |
1973年 | 28篇 |
1971年 | 25篇 |
排序方式: 共有7711条查询结果,搜索用时 281 毫秒
151.
152.
Seedlings of Pinus sylvestris were grown for 6 weeks under natural light conditions in a temperature controlled environment room. Cuttings from these plants were rooted in tap water or in indolebutyric acid (IBA) solutions for 60 days at an irradiance of 16 W m-2 . Experiments were performed at 3-week intervals during two growth seasons. — Seasonal changes in root formation were found in control cuttings as well as in IBA treated cuttings. The number of roots and the percentage of cuttings that rooted were high during early spring and autumn. During the summer period hardly any roots were formed. Stimulation of root formation by IBA occurred manily during spring and autumn when cuttings already possessed the ability to form roots. — The influence of photoperiod during stock plant growth was also investigated. Shorter photoperiod resulted in an increase in the number of roots and rooting percentage. The period during summer where rooting was inhibited under natural light conditions was considerably shortened when stock plants were grown at a photoperiod of only 4 h. The results demonstrate the importance of the growing conditions for stock plants for subsequent root formation. The results are discussed with special reference to the role of irradiance. 相似文献
153.
154.
Comparison of semiautomatic digitizer-tablet and simple point counting performance in morphometry 总被引:2,自引:0,他引:2
H J?rgen G Gundersen M Boysen A Reith 《Virchows Archiv. B, Cell pathology including molecular pathology》1981,37(3):317-325
A comparison is made between the efficiency of an opto-manual digitizer-tablet (MOP-AM 03) and simple point counting in the analysis of drawings of basal cells in the normal and pathologically altered chonchal epithelium. The analysis included estimation of the areas of cellular, nuclear and nucleolar sectional profiles as well as the cell basal width, i.e. the length of cell profile attachment to the basement membrane. The morphometric results obtained with the two methods are virtually identical. The efficiency of point counting is somewhat higher than that of the digitizer, but the prices of the two sets of equipment differ by one or two orders of magnitude. In general, the unquestionable measuring precision of the digitizer is unlikely to be of much impact in most biological studies due to the inevitable biological variation between individuals under study and the large variation which is always added at the level of single features by random sectioning. 相似文献
155.
156.
157.
158.
Thermoanaerobacter ethanolicus gen. nov., spec. nov., a new,extreme thermophilic,anaerobic bacterium
Two strains, JW 200 and JW 201, of an extreme thermophilic, non-spore-forming anaerobic bacterium were isolated from alkaline and slightly acidic hot springs located in Yellowstone National Park. Both strains were peritrichously flagellated rods. Cell size varied from 0.5–0.8 by 4–100 m; coccoid-shaped cells of about 1 m in diameter frequently occurred. Division was often unequal. Spheroplast-like forms were visible at the late logarithmic growth phase. The Gram reaction was variable. The DNA base composition of the two strains was between 37 and 39 mol% guanine plus cytosine as determined by buoyant density measurements and approximately 32% by the thermal denaturation method. The main fermentation products from hexoses were ethanol and CO2. Growth occurred between 37 and 78°C and from pH 4.4 to 9.8. The name Thermoanaerobacter ethanolicus gen. nov., spec. nov. was proposed for the two, new isolates. Strain JW 200 was designated as the type strain.A preliminary account of this work was presented at the annual meeting of the American Society for Microbiology, Los Angeles, CA, 1979 (J. Wiegel and L. G. Ljungdahl, Abstr. Annu. Meet. Am. Soc. Microbiol., 1979, 163, p. 105) and at the 27th IUPAC Congress Helsinki, 1979 (L. G. Ljungdahl and J. Wiegel, Abstracts p. 546) 相似文献
159.
Jürgen Kunze Ulrich H. Frenzel Elke Hüttig Frank-Reiner Grosse Hans-Rudolf Wiedemann 《Human genetics》1977,35(2):237-240
Summary We report a newborn with incontinentia pigmenti Bloch-Sulzberger and male phenotype. Chromosome analysis revealed a Klinefelter's syndrome 47,XXY. These findings are compatible with the hypothesis of dominant sexlinked genes carried on the X-chromosome in this disease.
Zusammenfassung Wir berichten über ein neugeborenes Kind mit männlichem Phänotyp bei Incontinentia pigmenti Bloch-Sulzberger. Bei der klinischen Abklärung fand sich die Gonosomenaberration eines Klinefelter-Syndroms 47,XXY. Dieser Befund geht konform mit der Vermutung eines dominant X-gekoppelten Erbganges dieser seltenen Hauterkrankung.相似文献
160.