全文获取类型
收费全文 | 2349篇 |
免费 | 75篇 |
出版年
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 26篇 |
2016年 | 37篇 |
2015年 | 60篇 |
2014年 | 80篇 |
2013年 | 144篇 |
2012年 | 125篇 |
2011年 | 120篇 |
2010年 | 70篇 |
2009年 | 96篇 |
2008年 | 136篇 |
2007年 | 122篇 |
2006年 | 140篇 |
2005年 | 124篇 |
2004年 | 125篇 |
2003年 | 145篇 |
2002年 | 156篇 |
2001年 | 46篇 |
2000年 | 46篇 |
1999年 | 47篇 |
1998年 | 48篇 |
1997年 | 41篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 29篇 |
1993年 | 27篇 |
1992年 | 28篇 |
1991年 | 29篇 |
1990年 | 30篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 14篇 |
1973年 | 7篇 |
1971年 | 10篇 |
1969年 | 8篇 |
1967年 | 6篇 |
排序方式: 共有2424条查询结果,搜索用时 312 毫秒
1.
Taiichiro Okajima Toshiharu Motomatsu Ken-ichi Kato Hiroshi Ibayashi 《Life sciences》1980,26(9):699-705
Intraventicular injection of beta-endorphin (beta LPH61?91) in urethane anesthetized male rats led to a dose dependent increase of plasma prolactin levels. Intravenous injection of apomorphine completely abolished the stimulatory effect of beta-endorphin. Animals treated with 6-hydroxydopamine (6-OHDA) and 6-OHDA plus desmethylimipramine showed inhibition of beta-endorphin induced prolactin release. These results suggest that beta-endorphin presynaptically inhibits the activity of dopaminergic neurones, leading to the stimulation of plasma prolactin levels. 相似文献
2.
Human chorionic gonadotropins (hCGs) highly purified from the urine of patients with trophoblastic diseases and of healthy pregnant women contain approximately four mucin-type sugar chains in one molecule. The structures of these sugar chains were studied comparatively by using a new sensitive method to obtain mucin-type sugar chains quantitatively as radioactive oligosaccharides from a small amount of glycoproteins. The mucin-type sugar chains of all hCGs include sialylated and nonsialylated Gal beta 1----3GalNAc and Gal beta 1----4GlcNAc beta 1----6(Gal beta 1----3)GalNAc. In the case of normal hCG and hydatidiform mole hCG, oligosaccharides containing the tetrasaccharide core occupy approximately 10% of the total mucin-type sugar chains. The ratio of the tetrasaccharide containing oligosaccharides is increased prominently to approximately 60% in choriocarcinoma hCG. The proportion in invasive mole hCG was also increased, but less than the proportion of choriocarcinoma hCG. 相似文献
3.
The effects of estrogen on the uridine uptake into cells were examined in primary cultures of liver parenchymal cells from Xenopus laevis. The total uptake of [3H]uridine into the estrogen-treated cells and its incorporation into RNA were about 1.5 times higher than the values for control cells. The uptake of [3H]adenosine and its incorporation into RNA were not affected by estrogen. An experiment in which liver parenchymal cells were double labeled with [3H]uridine and [3H]adenosine showed that estrogen elevated the specific radioactivity of the UTP pool 1.4-fold the value found for the control cells, but that of the ATP pool was not altered by estrogen. Short term labeling revealed that estrogen did not significantly alter the rate of the initial uptake of [3H]uridine into the cells, but it did stimulate [3H]uridine phosphorylation about 1.7-fold. Uridine kinase activity measured in cell-free extracts of hepatocytes treated with estrogen had a value 1.6 times that of the control cells. These data indicate that the stimulation of [3H]uridine uptake and phosphorylation in Xenopus laevis hepatocytes in the presence of estrogen is caused by the enhancement of uridine kinase activity. 相似文献
4.
In several vascular inflammatory reactions (i.e. immunity and thrombosis) inflammatory mediators lead to the activation of vascular endothelial cells (EC). To date, a number
of functional molecules induced on the surface of activated-EC have been identified. We report here that Globotetraosylceramide
(Gb4), a glycosphingolipid expressed in EC, is a novel inducible molecule on EC activated by TNF-α. The cell surface expression
of Gb4 is increased in a time-dependent manner under TNF-α stimulation, which shows distinct expression kinetics of major
proteins induced by TNF-α on EC. MALDI-TOF-MS analysis revealed that the enhanced Gb4 predominantly contains C24:0 fatty acid
in the ceramide moiety. Isolated caveolae/lipid raft-enriched detergent insoluble membrane domains in activated-EC predominantly
contain this molecular species of Gb4. Gb4 containing C16:0 fatty acid in the ceramide moiety, which is known to constitute
the major species of Gb4 in plasma, is also found as a major molecular species in EC. These observations indicate that Gb4,
especially with very long fatty acid, is enhanced in EC during its inflammatory reaction, and suggest the potential utility
of Gb4 as a biomarker for monitoring inflammation status of EC involving its related diseases. 相似文献
5.
Biotransformation of 1-nitropyrene and 2-nitrofluorene to novel metabolites, the corresponding formylamino compounds, in animal bodies 总被引:1,自引:0,他引:1
The present study provides the first evidence that nitropolycyclic aromatic hydrocarbons such as 1-nitropyrene and 2-nitrofluorene are metabolized to the corresponding formylamino compounds in animal bodies. The study shows that the formation of such novel metabolites, 1-formylaminopyrene and 2-formylaminofluorene, is due to N-formylation of the nitroreduction products, 1-aminopyrene and 2-aminofluorene, by liver formamidase in the presence of N-formyl-L-kynurenine. 相似文献
6.
Kazuo Nakamura Yoshifumi Amano Ooki Nakayama 《Applied microbiology and biotechnology》1989,31(4):351-354
Summary A microbial sensor of immobilized Thiobacillus thiooxidans S3 cells was assembled to determine free sulphite in wine. Sulphite oxidation activity of the immobilized cells was sufficiently high for use even after 3 months storage at 4° C. The sensitivity of this sensor was 116 nA·1·mg-1 for sulphur dioxide. The relationship between the current decrease and the sulphur dioxide concentration was linear up to 17 mg·1-1. The sampling rate achieved was 10 min per sample including washing time. This sensor method needed no pretreatment of wine samples, and wines diluted with 5 mM sulphuric acid solution could be directly introduced in the computer-aided analysis system. The pigments in red wine did not disturbed the analysis. 相似文献
7.
8.
Genetic characterization of human KB cell lines resistant to epidermal growth factor: Pseudomonas exotoxin conjugates 总被引:1,自引:0,他引:1
Pleiotropic human KB cell mutants, selected for resistance to a conjugate of epidermal growth factor with Pseudomonas exotoxin (PE-EGF), were characterized genetically. These mutants have a pleiotropic phenotype, which includes reduced number of EGF receptors and reduced growth rate. Hybrid cells between HeLa D98 and four out of five of these resistant cell lines were more resistant to PE-EGF than hybrids formed between HeLa D98 and parental KB cells. This result indicates that the phenotype of PE-EGF resistance is incompletely dominant in four out of five cases and recessive in one out of five variants. In three separate experiments, transfection of DNA from two of the dominant resistant cell lines resulted in transformation of wild-type KB cells to PE-EGF resistance, confirming the dominant nature of these mutations, which affect levels of EGF receptor in KB cells. 相似文献
9.
Ken-ichi Takita Akira Tanigami Takashi Tokino Carol Jones Yusuke Nakamura 《Genomics》1992,13(4):1296-1299
Fifty-four clones containing human inserts were selected from a cosmid library constructed from a somatic cell hybrid containing chromosome 11p15.3-p15.5 as its only human complement. In 32 of these clones, 63 polymorphic systems were identified with a panel of restriction enzymes: 57 conventional RFLP systems and 6 highly polymorphic VNTR systems. Although we examined the cosmid with only seven enzymes, 18 clones (including 6 VNTRs) were polymorphic with three or more enzymes. The results suggested that DNA sequences on the peritelomeric region of chromosome 11p tend to be highly variable. Because these markers are highly informative, they will be excellent resources for investigations of hereditary diseases and tumor suppressor genes in this region of chromosome 11. 相似文献
10.
K Yoshino S Kawagishi M Iwamoto N Amano 《Nihon seirigaku zasshi. Journal of the Physiological Society of Japan》1991,53(6):207-215
We developed a method for a determination of the amount of retrogradely transported HRP in the rat masseteric motoneuron using a modification of Mesulam's HRP histochemical protocol and an image processing system combined with a light microscope and a television camera. To test the validity and reproducibility of the new method, a quantitative comparison of the amount of dark blue granules of HRP-product in the cell body of masseteric motor neurons was performed between the right and left trigeminal motor nuclei of 70 rats, which resulted in no significant difference. An additional study used the method was made of the effects of administration of five dopamine receptor antagonists with different biochemical and pharmacologic properties on retrograde transport of HRP in the rat masseteric motoneuron. As a result, chlorpromazine, haloperidol, SCH 23390, and sulpiride significantly enhanced retrograde transport of HRP as against domperidone which showed no significant change in the transport. A possible regulatory system for retrograde transport of HRP in the masseteric motoneuron was discussed in relation to the action of the dopamine receptor. 相似文献