全文获取类型
收费全文 | 4250篇 |
免费 | 579篇 |
国内免费 | 1篇 |
专业分类
4830篇 |
出版年
2021年 | 38篇 |
2018年 | 39篇 |
2016年 | 57篇 |
2015年 | 110篇 |
2014年 | 98篇 |
2013年 | 128篇 |
2012年 | 193篇 |
2011年 | 162篇 |
2010年 | 109篇 |
2009年 | 103篇 |
2008年 | 145篇 |
2007年 | 177篇 |
2006年 | 138篇 |
2005年 | 113篇 |
2004年 | 154篇 |
2003年 | 139篇 |
2002年 | 134篇 |
2001年 | 146篇 |
2000年 | 140篇 |
1999年 | 152篇 |
1998年 | 49篇 |
1997年 | 48篇 |
1996年 | 54篇 |
1995年 | 46篇 |
1994年 | 44篇 |
1993年 | 39篇 |
1992年 | 97篇 |
1991年 | 115篇 |
1990年 | 123篇 |
1989年 | 101篇 |
1988年 | 114篇 |
1987年 | 97篇 |
1986年 | 98篇 |
1985年 | 102篇 |
1984年 | 87篇 |
1983年 | 85篇 |
1982年 | 74篇 |
1981年 | 59篇 |
1980年 | 55篇 |
1979年 | 92篇 |
1978年 | 59篇 |
1977年 | 59篇 |
1976年 | 51篇 |
1975年 | 62篇 |
1974年 | 50篇 |
1973年 | 58篇 |
1972年 | 37篇 |
1971年 | 39篇 |
1969年 | 40篇 |
1967年 | 37篇 |
排序方式: 共有4830条查询结果,搜索用时 15 毫秒
91.
Filtered proteins including the low-molecular-weight protein lysozyme are reabsorbed by the proximal tubule via adsorptive endocytosis. This process starts with binding of the protein to the brush-border membrane. The binding of 125I-labelled egg-white lysozyme (EC 3.2.1.17) to isolated brush-border membranes of rat kidney and the effect of several low-molecular weight proteins on that binding was determined. The Scatchard plot revealed a one-component binding type with a dissociation constant of 5.3 μM and 53.0 nmol/mg membrane protein for the number of binding sites. The binding of the cationic lysozyme was inhibited competitively by the addition of cationic cytochrome c to the incubation medium, while the neutral myoglobin had no effect. The anionic β-lactoglobulin A inhibited the lysozyme binding in a noncompetitive manner. These data suggest that the binding takes place between positively charged groups of the protein molecule and negative sites on the brush-border membrane, and, the competition between the cationic cytochrome c and the cationic lysozyme for the binding sites may be responsible for the inhibitory effect of cytochrome c on renal lysozyme reabsorption. The binding step at the brush-border membrane appears to be cation-selective. 相似文献
92.
Production of Viscous Dextran-Containing Whey-Sucrose Broths by Leuconostoc mesenteroides ATCC 14935 下载免费PDF全文
Viscous broths were produced by growing Leuconostoc mesenteroides on a medium containing whey supplemented with sucrose. When combined with similarly produced xanthan-containing broths, a synergistic increase in viscosity was observed. 相似文献
93.
The mutant allele giant of Drosophila melanogaster affects the timing and the level of increase in ecdysteroid titer normally occurring at puparium formation. The third larval instar is extended by 4 days in phenotypically “giant” individuals during which the imaginal discs mature slower than normal and finally take on the folding pattern characteristic of maturity at a time when normal individuals have already formed puparia. After puparium formation, development occurs at the same rate in giant and wild-type animals. Feeding 20-hydroxyecdysone at 94 hr after oviposition allows giant larvae to develop at the same rate as wild-type larvae and to produce normal-sized adults (although at 94 hr the imaginal discs of giant lack much of the folding pattern of mature discs). Radioimmunological determination of ecdysteroid titers in giant and normal individuals indicates that the peak of ecdysteroid activity associated with puparium formation is lower in giant and occurs 4 days later than normal. These results indicate that giant is an ecdysteroid-deficient mutant with major effects on metamorphosis. Unlike previously reported ecdysteroid-deficient mutants, however, giant larvae eventually develop into adults and may be induced to undergo complete metamorphosis at the same time as wild type by feeding 20-hydroxyecdysone. 相似文献
94.
Duplication of chromosome 10p: confirmation of regional assignments of platelet-type phosphofructokinase. 总被引:1,自引:1,他引:0 下载免费PDF全文
S Schwartz M M Cohen S R Panny J H Beisel S Vora 《American journal of human genetics》1984,36(4):750-759
A proband, clinically thought to have trisomy 10p, was found to have an inverted duplication of 10p [46, XY, inv dup(10)(qter----p15.3::p15.3----p 11.1:)]. The phenotypic findings and cytogenetic observations were supported by relevant biochemical studies. The activity of phosphofructokinase (platelet-type; PFKP), previously localized to 10p, and hexokinase-I (HKI), putatively on 10p, demonstrated 153% and 149% of control activity in the proband's fibroblasts. These gene-dosage effects confirmed the clinical and cytogenetic observations as well as the localization of HKI to 10p. Additionally, phosphofructokinase (PFK) and hexokinase (HK), which are control points in the glycolytic pathway, were shown to be syntenic. 相似文献
95.
Effects of chronic hyperinsulinaemia on hepatic enzymes involved in lipogenesis and carbohydrate metabolism in the young rat. 下载免费PDF全文
Chronic (6 days) hyperinsulinaemia in young rats produced lower blood glucose concentrations and augmented body- and liver-weight gain. The insulin-treated rats had increased hepatic activities of citrate-cleavage enzyme, 'malic' enzyme and high-substrate (6.6 mM-phosphoenolpyruvate) pyruvate kinase, and decreased glucose 6-phosphatase. There were no changes in activities of phosphoenolpyruvate carboxykinase, phosphofructokinase, low-substrate (1.3 mM-phosphoenolpyruvate) pyruvate kinase, glucokinase and hexokinase. 相似文献
96.
97.
98.
Cytochalasin B prevents both migration and wound-associated replication when applied to wounded monolayers of bovine endothelium in tissue culture. The normal low background rate of replication in undisturbed areas of the cultures is not inhibited by cytochalasin B. These results suggest that some form of movement may be required for initiation of wound-associated replication by endothelial cells. 相似文献
99.
Velopharyngeal function following maxillary advancement. 总被引:5,自引:0,他引:5
In a series of 40 patients who had maxillary advancements, none developed velopharyngeal incompetence. Unlike the cleft palate patient who is more at risk, there are distinct anatomical characteristics in craniofacial dysostosis which favor maintenance of the integrity of the velopharyngeal mechanism. Hyponasality was eliminated in 5 patients with Crouzon's disease. On cephalometric study, it was observed that after maxillary advancement the nasopharyngeal volume was expanded and the angle formed by the hard and soft palates was increased. On phonating cephalograms, the velopharyngeal contact became more physiological after maxillary advancement in the craniofacial dysostosis patient. The only postoperative articulatory changes after maxillary advancement were in the production of the /s/ sound, which is particularly sensitive to changes in dentoalveolar relationships. 相似文献
100.
A Spira E Philippe N Spira J Dreyfus D Schwartz 《Biomedicine / [publiée pour l'A.A.I.C.I.G.]》1977,27(7):266-270
The pathological study of all placentas from women smoking at least five cigarettes daily during pregnancy (248 cases) and of those placentas from a corresponding control group randomised among all the non-smokers (196 cases) has been set up at the maternity hospital of Haguenau (France) since 1974. The systematic histological examination has shown among smokers a higher frequency of abonormal trophoblast and especially of nuclear clumps in the syncytiotrophoblast. On the other hand, according to a standard protocol, the grouping of various abnormalities has shown, among smokers, a higher frequency of "signs of hypoxia". The lack of relationship between these "signs of hypoxia" and the well-known decreased birthweight among smokers suggests that smoking during pregnancy could always go with a decreased birthweight without a corresponding decreased placental weight, and seldom with an intra-uterine hypoxia. These two effects are independent. 相似文献