全文获取类型
收费全文 | 17000篇 |
免费 | 995篇 |
国内免费 | 3篇 |
出版年
2023年 | 106篇 |
2021年 | 199篇 |
2020年 | 177篇 |
2019年 | 207篇 |
2018年 | 420篇 |
2017年 | 411篇 |
2016年 | 531篇 |
2015年 | 606篇 |
2014年 | 722篇 |
2013年 | 1120篇 |
2012年 | 1239篇 |
2011年 | 1216篇 |
2010年 | 833篇 |
2009年 | 603篇 |
2008年 | 830篇 |
2007年 | 710篇 |
2006年 | 717篇 |
2005年 | 559篇 |
2004年 | 560篇 |
2003年 | 521篇 |
2002年 | 469篇 |
2001年 | 277篇 |
2000年 | 238篇 |
1999年 | 224篇 |
1998年 | 149篇 |
1997年 | 132篇 |
1996年 | 122篇 |
1995年 | 133篇 |
1994年 | 104篇 |
1993年 | 101篇 |
1992年 | 154篇 |
1991年 | 152篇 |
1990年 | 136篇 |
1989年 | 156篇 |
1988年 | 147篇 |
1987年 | 112篇 |
1986年 | 119篇 |
1985年 | 171篇 |
1983年 | 133篇 |
1982年 | 116篇 |
1981年 | 121篇 |
1979年 | 148篇 |
1978年 | 109篇 |
1975年 | 101篇 |
1974年 | 130篇 |
1973年 | 124篇 |
1972年 | 103篇 |
1970年 | 117篇 |
1969年 | 117篇 |
1968年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
Adolf Češka 《Folia Geobotanica》1966,1(2):93-100
Various possibilities of usingSörensen’s coefficient of floristic similarity in plant sociology are summarized. A new formula (11). derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés. 相似文献
212.
The existence of six amylase heterogeneity variants in serum and urine has been discovered in a group of 111 families with twins, and the frequence of each variant was determined. It had been shown that each of these amylase heterogeneity variants is inherited codominantly, and the mode of inheritance is demonstrated schematically.These amylase heterogeneity variants may be used as an aid to twin zygosity determination and also in paternity problems. 相似文献
213.
Forearm veins were studied to determine whether patients with primary varicosity of the saphenous veins had a generalized abnormality of the venous system. Distensibility of the superficial forearm and hand veins was measured in 25 patients with varicosity of the saphenous veins, and in 25 control subjects. Patients with saphenous varicosity had a significantly greater distensibility of the undistorted forearm veins than control subjects. Hysteresis of distensibility curves was more prnounced in patients with varicosity than in control subjects; mean hysteresis index was 0.65 ± 0.06 versus 0.28 ± 0.02 in controls. These investigations suggest that an increased distensibility of the venous system is the predisposing factor in the development of varicose veins. 相似文献
214.
The relationship of different soya meal components to gibberellin (GA) production was studied. Fluorometric assay confirmed that under the given fermentation conditions, only gibberellic acid (GA3) was synthesized on medium containing corn steep. On substituting soya flour for corn steep, the same amount of GA3 was produced and in addition gibberellin A (GA1) was formed. The GA3: GA1 ratio was 1∶1. The course of fermentation in media containing the soya meal protein fraction (fraction I), the soya meal amino acid complex, the corn steep amino acid complex and individual amino acids (γ-aminobutyric acid or tryptophane) was the same as in the control medium containing soya meal. The soya meal fraction II, which is characterized by a high cellulose and carbohydrate content, raised GA production by 25% as compared with production in medium containling soya meal; it simultaneously stimulated GA3 production, so that the final GA3: GA1 ratio was 4∶1. 相似文献
215.
Было установлено, что актиномицет Str. noursei образует амиды некоторых разветвленных алифатических кислот: изобутирамид, метилэтилацетамид, изовалерамид, а, вероятно, и более сложные гомологи, как изокапронамид, изоэнантамид и 4-метилкапронамид. Обсуждается биогенез этих веществ. 相似文献
216.
217.
Antiserum был подготовлен противингибитор вируса haemagglutination (IVH)одна из эмбриона chorioallantoic мембр анныепутем иммун изации морских св инокЭто анти-инги битора в сыворотке заблокирован ингибирование IVH из chorioallantoicмембран в haemagglutination испытанияно ника кого влияния на ре цепторы эритроци товСыворотке кро] ви не влияет рост chorioallantoic мембраны клет ок инет нейтрализ овать воздействи е на вирус гриппа Она снизилась спо собность chorioallantoic мембр ан для adsorb вируса гри ппа, а также степен ь размножения вир усав такого рода тканиАвторы хоте ли бы поблагодари ть г-н Г. Ruttkay-Ne -палубе и для проведения эле ктрофореза меру ния. 相似文献
218.
The work is concerned with the question of the effect of humic acids on the biological action of agropyrene, the effective substance from the rootstock of Agropyron repens (L.) P. BEAUV. The test organism was the alga Scenedesmus obliquus (TURP.) KRÜGER, cultivated in mineral solution. The basic biological test was the determination of the number and size of the cells of this alga. It was found that the way in which agropyrene acts on combined application with humus acids depends on which humus fraction is used. It can display a synergic action if humic acid is used, since this substance probably facilitates the penetration of agropyrene into the cells. On the other hand, fulvic acid counteracts the activity of agropyrene and this most probably by mutual binding and blocking of active groups and links. 相似文献
219.
5-Bromo-2’-deoxyuridine-2-14C was prepared from 5-bromouracil-2-14C and 2’-de-oxyguanosine using trans-N-deoxyribosylase fromLactobacillus helveticus and incorporated into DNA ofAllium cepa roots. After isolating the DNA and hydrolyzing it enzymatically to deoxynucleoside-5’-phosphates a radioactive nucleotide was detected which yielded 5-bromo-2’-deoxyuridine-2-14C on enzymatic dephosphorylation. The incorporation of 5-iodo-2’-deoxy-uridine-2-14C was followed only by microautoradiography. 相似文献
220.