全文获取类型
收费全文 | 3392篇 |
免费 | 178篇 |
国内免费 | 2篇 |
出版年
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 37篇 |
2016年 | 51篇 |
2015年 | 68篇 |
2014年 | 86篇 |
2013年 | 169篇 |
2012年 | 143篇 |
2011年 | 156篇 |
2010年 | 123篇 |
2009年 | 92篇 |
2008年 | 145篇 |
2007年 | 178篇 |
2006年 | 158篇 |
2005年 | 159篇 |
2004年 | 189篇 |
2003年 | 176篇 |
2002年 | 151篇 |
2001年 | 107篇 |
2000年 | 105篇 |
1999年 | 106篇 |
1998年 | 42篇 |
1997年 | 46篇 |
1996年 | 43篇 |
1995年 | 46篇 |
1994年 | 52篇 |
1993年 | 38篇 |
1992年 | 80篇 |
1991年 | 57篇 |
1990年 | 72篇 |
1989年 | 50篇 |
1988年 | 51篇 |
1987年 | 46篇 |
1986年 | 48篇 |
1985年 | 59篇 |
1984年 | 41篇 |
1983年 | 28篇 |
1982年 | 22篇 |
1981年 | 31篇 |
1979年 | 25篇 |
1978年 | 28篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 22篇 |
1974年 | 13篇 |
1973年 | 19篇 |
1972年 | 14篇 |
1970年 | 14篇 |
排序方式: 共有3572条查询结果,搜索用时 15 毫秒
1.
A spectrophotometric method for inorganic phosphate determination in the presence of thiol compounds is described. Thiol compounds, which interfere with the measurement of inorganic phosphate by a modification of the method of Gomori, are removed by carboxymethylation by iodoacetate prior to the formation and reduction of phosphomolybdate complex. A linear standard curve is obtained by this method, and the method is suitable for the assay of a phosphate-releasing enzyme when the measurement must be performed in the presence of thiol compounds. 相似文献
2.
The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells. 相似文献
3.
[3H]Dihydroergocryptine ([3H]DHE) was shown to bind to sites in membranes from neuroblastoma X glioma hybrid cells (NG 108-15) that had the characteristics expected of alpha-adrenergic receptors. The binding was saturable with 0.3 pmol [3H]DHE bound per mg of protein and of high affinity, with an apparent dissociation constant (KD) of 1.8 nM. The specificity of the binding site for various ligands was more similar to that of alpha 2 receptors than to that of alpha 1. No specific binding of [3H]WB-4101 was found in the membranes derived from NG 108 cells. This finding also indicated that the [3H]DHE binding site in the cell is the alpha 2 receptor. GTP lowered the affinity of agonists for the [3H]DHE binding site, although the nucleotide hardly affected the affinity of antagonists including [3H]DHE. 相似文献
4.
Reiko Yu-Ito Kazuko Ôba Ikuzo Uritani 《Bioscience, biotechnology, and biochemistry》2013,77(8):2087-2091
In addition to HMG-CoA reductase, another HMG-CoA utilizing enzyme is present in the Mt fraction of sweet potato root tissue and its activity interferes with the assay to HMG-CoA reductase activity. 相似文献
5.
K Sakurai N Seki R Fujii K Yagui Y Tokuyama F Shimada H Makino Y Suzuki N Hashimoto Y Saito T Egashira K Matsui A Kanatsuka 《Hormones et métabolisme》2000,32(8):316-320
Mutations of the hepatocyte nuclear factor 4 alpha (HNF-4alpha) gene have been demonstrated in maturity-onset diabetes of the young (MODY) 1 families. To investigate the possibility that the HNF-4alpha gene contributes to the onset of non-insulin-dependent diabetes mellitus (NIDDM) in Japanese patients, we screened all exons and flanking introns of this gene for mutations in 100 patients with NIDDM diagnosed after 25 years of age. We identified two missense mutations: M49V in exon 1c and T1301 in exon 4; and two nucleotide substitutions in introns: cytosine to thymidine at -5 nt in intron 1b and adenine to thymidine at -21 nt in intron 5. We screened an additional 220 diabetic subjects for the polymorphism in intron 1b. The c/t substitution in intron 1b was associated with NIDDM. This substitution in the polypyrimidine tract, an important cis-acting element directing intron removal, is likely to influence pre-mRNA splicing of this gene. T1301 in exon 4 was observed in only two diabetic subjects. This mutation could influence the conformation of this peptide, resulting in changes in ligand binding domain function. M49V in exon 1c was found in both diabetic and non-diabetic subjects; isoforms HNF-4alpha 4, 5, and 6 with this mutation may impair glucose metabolism in tissue. In contrast to the primary cause of nonsense and missense mutations of the HNF-4alpha gene in MODY1, the nucleotide substitution in intron 1b may partially contribute to development of NIDDM in combination with other genetic and environmental factors. 相似文献
6.
7.
Novel transcription map for the B19 (human) pathogenic parvovirus 总被引:30,自引:15,他引:15
8.
The axial growth of de-coated cocklebur (Xanthium pennsylvanicumWallr.) seeds, whose axes were divided into 4 zones, was examinedin relation to the temperature-dependent shift of the effectof C2H4 on germination. At 23?C, where both C2H4 and CO2 stimulatedgermination, CO2 promoted the axial growth at the radicle tipzone, whereas C2H4 promoted growth in the proximal portion ofthe axis. At 33?C, C2H4 inhibited germination, and stronglysuppressed the growth at the radicle tip, whereas the effectof CO2 did not change. The inhibition of growth at the radicletip zone was alleviated by O2 enrichment, which also reversedthe inhibition of germination. It is thus apparent that thetemperature-dependent shift of the action of C2H4 is associatedwith a temperature-dependent responsiveness of the radicle tipzone to C2H4. Growth of the radicle tip zone was sensitive toNaN3, whereas the proximal portion was sensitive to benzohydroxamicacid, an inhibitor of alternative respiration, suggesting thatthere may be an increase in the operation of the alternativerespiration path along a gradient of axial tissue from the tiptowards the cotyledonary side. The effects of CO2 and C2H4 arediscussed in relation to the different respiratory activitiesin each axial zone of cocklebur seeds. (Received May 9, 1986; Accepted November 6, 1986) 相似文献
9.
Although patients with primary hyperparathyroidism (1 degree HPT) were euthyroid, we measured serum thyroid hormone levels in 16 patients with 1 degree HPT together with 17 patients with hypercalcemia due to malignant diseases (HCM). In patients with 1 degree HPT, serum levels of T3, T4 and T3U were within normal range, but serum rT3 (reverse T3) levels (205 +/- 37 pg/ml, mean +/- SD) were significantly decreased as compared with those in normal controls (276 +/- 44 pg/ml, P less than 0.01). A significant inverse correlation was observed between the serum levels of rT3 and parathyroid hormone (PTH) (r = 0.54, P less than 0.05). After parathyroidectomy, serum rT3 levels were significantly elevated (240 +/- 56 pg/ml) compared to preoperative levels (P less than 0.01). Low levels of serum rT3 seemed to be attributed to the high levels of serum PTH. On the other hand, serum levels of T3 and T4 were low and serum rT3 levels were high in patients with HCM. Low serum rT3 allows for the differentiation of patients with 1 degree HPT from those with HCM. 相似文献
10.
Specific inhibitors of tyrosine-specific protein kinase, synthetic 4-hydroxycinnamamide derivatives 总被引:6,自引:0,他引:6
T Shiraishi T Domoto N Imai Y Shimada K Watanabe 《Biochemical and biophysical research communications》1987,147(1):322-328
Several newly synthesized 4-hydroxycinnamamide derivatives such as 3-(3',5'-di-isopropyl-4'-hydroxybenzylidene)-2-oxindol (ST 280), 3-(3',5'-di-methylthiomethyl-4'-hydroxybenzylidene)-2-oxindole (ST 458), alpha-cyano-3-ethoxy-4-hydroxy-5-phenylthiomethylcinnamamide (ST 638) and 3-(3'-ethoxy-4'-hydroxy-5'-phenylthiomethylbenzylidene)-2-pyrol idinone (ST 642) were found to inhibit tyrosine-specific protein kinase activity of the epidermal growth factor (EGF) receptor with IC50 values of 0.44 microM, 0.44 microM, 0.37 microM and 0.85 microM, respectively. None of them showed inhibitory effect on the enzyme activities of serine- and/or threonine-specific protein kinases such as cAMP-dependent protein kinase, Ca2+/phospholipid-dependent protein kinase C, casein kinase I and casein kinase II. In addition, none of them had effect on Na+/K+-ATPase or 5'-nucleotidase. The results suggest that the compound ST 280, ST 458, ST 638 and ST 642 are potent and specific inhibitors of tyrosine-specific protein kinase. 相似文献