全文获取类型
收费全文 | 6409篇 |
免费 | 671篇 |
国内免费 | 693篇 |
出版年
2023年 | 62篇 |
2022年 | 167篇 |
2021年 | 245篇 |
2020年 | 218篇 |
2019年 | 271篇 |
2018年 | 233篇 |
2017年 | 193篇 |
2016年 | 276篇 |
2015年 | 340篇 |
2014年 | 472篇 |
2013年 | 457篇 |
2012年 | 520篇 |
2011年 | 466篇 |
2010年 | 318篇 |
2009年 | 328篇 |
2008年 | 387篇 |
2007年 | 320篇 |
2006年 | 312篇 |
2005年 | 251篇 |
2004年 | 262篇 |
2003年 | 230篇 |
2002年 | 212篇 |
2001年 | 124篇 |
2000年 | 113篇 |
1999年 | 110篇 |
1998年 | 81篇 |
1997年 | 77篇 |
1996年 | 51篇 |
1995年 | 41篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 55篇 |
1991年 | 44篇 |
1990年 | 41篇 |
1989年 | 36篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 13篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 22篇 |
1974年 | 15篇 |
1972年 | 13篇 |
1968年 | 14篇 |
1966年 | 13篇 |
排序方式: 共有7773条查询结果,搜索用时 15 毫秒
1.
2.
Jianhua Zhang Mei Liu Hongjian Jin Liandong Deng Jinfeng Xing Anjie Dong 《AAPS PharmSciTech》2010,11(2):894-903
Lactate esters are widely used as food additives, perfume materials, medicine additives, and personal care products. The objective
of this work was to investigate the effect of a series of lactate esters as penetration enhancers on the in vitro skin permeation of four drugs with different physicochemical properties, including ibuprofen, salicylic acid, dexamethasone
and 5-fluorouracil. The saturated donor solutions of the evaluated drugs in propylene glycol were used in order to keep a
constant driving force with maximum thermodynamic activity. The permeability coefficient (K
p), skin concentration of drugs (SC), and lag time (T), as well as the enhancement ratios for K
p and SC were recorded. All results indicated that lactate esters can exert a significant influence on the transdermal delivery
of the model drugs and there is a structure-activity relationship between the tested lactate esters and their enhancement
effects. The results also suggested that the lactate esters with the chain length of fatty alcohol moieties of 10–12 are more
effective enhancers. Furthermore, the enhancement effect of lactate esters increases with a decrease of the drug lipophilicity,
which suggests that they may be more efficient at enhancing the penetration of hydrophilic drugs than lipophilic drugs. The
influence of the concentration of lactate esters was evaluated and the optimal concentration is in the range of 5∼10 wt.%.
In sum, lactate esters as a penetration enhancer for some drugs are of interest for transdermal administration when the safety
of penetration enhancers is a prime consideration. 相似文献
3.
4.
5.
6.
7.
Abstract. 1. Clip cages have been used widely by experimental ecologists to contain insects on plants.
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments. 相似文献
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments. 相似文献
8.
D K Whittaker S Ryan K Weeks W M Murphy 《American journal of physical anthropology》1987,73(3):389-396
The approximal surfaces of premolars and molars of 376 adult British-Romano skulls were examined for wear facets. The type of wear was designated as convex, concave, sigmoid, or flat, and the degree was categorised on a three-point scale. Concave wear facets were more frequently seen in the older age groups, but the type of wear was similar on right and left sides. Taking all teeth together or as individual tooth types, concave wear was significantly more likely on mesial rather than distal surfaces. The degree of wear was age related and similar on right and left sides in both males and females. It is suggested that the distribution of concave facets may be related to movements between adjacent teeth. 相似文献
9.
The cell wall lipopolysaccharide of the green sulfur bacterium Chlorobium vibrioforme f. thiosulfatophilum was obtained by the phenol-chloroform-petroleum ether and the hot phenol-water methods, respectively. It contained mannose, glucose, galacturonic acid, glucosamine, glycine, and small amounts of rhamnose, galactose and glucuronic acid. In addition to d-glycero-d-mannoheptose, the corespecific constituents 2-keto-3-deoxyoctonate and l-glycero-d-mannoheptose were found. Polyacrylamide gel-electrophoresis in the presence of sodium deoxycholate gave no indication for the presence of O-specific repeating units. Degradation of the lipopolysaccharide required 10% acetic acid (100° C, 2 h). The lipid A moiety contained the total of glucosamine of the lipopolysaccharide as well as small amounts of 2,3-diamino-2,3-dideoxy-glucose. It was phosphate-free. The fatty acid spectrum comprised 3-OH-14:0, 3-OH-16:0, and iso-3-OH-18:0 besides little 12:0, 14:0 and 16:0. Hydroxylaminolysis and sodium methylate treatment revealed all of the three hydroxy fatty acids to be amidebound.Abbreviations DOC
sodium deoxycholate
- PAGE
polyacrylamide gel-electrophoresis 相似文献
10.
S G Whittaker F K Zimmermann B Dicus W W Piegorsch S Fogel M A Resnick 《Mutation research》1989,224(1):31-78
The diploid yeast strain D61.M was used to study induction of mitotic chromosome loss. The test relies upon the uncovering and expression of multiple recessive markers reflecting the presumptive loss of the chromosome VII homologue carrying the corresponding wild-type alleles. The underlying 'loss event' is probably complex since the predicted centromere-linked lethal tetrad segregations for chromosome VII are not recovered. Instead, the homologue bearing the multiple recessive markers is patently homozygous. An interlaboratory study was performed in which 16 chemicals were tested under code in 2 laboratories. The results generated by the Berkeley and Darmstadt laboratories were in close agreement. Acetonitrile, ethyl acetate, 4-acetylpyridine, propionitrile and nocodazole were identified as potent inducers of mitotic chromosome loss. Acetone, dimethyl sulfoxide and 2-methoxyethyl acetate either elicited weak responses or yielded ambiguous results. Water, carbon tetrachloride, 4-fluoro-D,L-phenylalanine, amphotericin B, griseofulvin, cadmium chloride, ethyl methanesulfonate and methylmercury(II) chloride failed to induce chromosome loss. These data suggest that the system described herein represents a reliable assay for chemically induced chromosome loss in yeast. 相似文献