全文获取类型
收费全文 | 2565篇 |
免费 | 150篇 |
国内免费 | 1篇 |
专业分类
2716篇 |
出版年
2021年 | 27篇 |
2020年 | 15篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 19篇 |
2016年 | 32篇 |
2015年 | 89篇 |
2014年 | 91篇 |
2013年 | 122篇 |
2012年 | 128篇 |
2011年 | 141篇 |
2010年 | 83篇 |
2009年 | 70篇 |
2008年 | 125篇 |
2007年 | 130篇 |
2006年 | 123篇 |
2005年 | 109篇 |
2004年 | 121篇 |
2003年 | 114篇 |
2002年 | 103篇 |
2001年 | 100篇 |
2000年 | 84篇 |
1999年 | 71篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 32篇 |
1995年 | 29篇 |
1994年 | 23篇 |
1993年 | 30篇 |
1992年 | 62篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 40篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 37篇 |
1985年 | 47篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 24篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 14篇 |
1973年 | 11篇 |
1972年 | 14篇 |
1971年 | 12篇 |
1967年 | 10篇 |
排序方式: 共有2716条查询结果,搜索用时 15 毫秒
41.
Hiroshi Yanagawa Kiyotsugu Kojima Masahiko Ito Nobuhiko Handa 《Journal of molecular evolution》1990,31(3):180-186
Summary Amino acid amides effectively reacted to produce polypeptides in response to microwave heating during repeated hydration-dehydration cycles. The polypeptides, formed from a mixture of glycinamide, alaninamide, valinamide, and aspartic acid -amide, had molecular weights ranging from 1000 to 4000 daltons. Amino acids were incorporated into the polypeptides in proportion to the starting concentrations, with the exception of glycine whose incorporation was 1.5 times higher than that of the other amino acids. The polypeptides had some definite secondary structure, such as -helix and -sheet, in aqueous solution. This reaction provides not only a convenient method for abiotic peptide formation but also a convenient method for the chemical synthesis of peptides. 相似文献
42.
Purification and characterization of a peptide C-terminal alpha-amidating enzyme from porcine atrium
In many peptide hormones and neuropeptides, the carboxy-terminal alpha-amide structure is essential in eliciting biological activity. Here we report the purification and characterization of an alpha-amidating enzyme from porcine atrium, in which a high concentration of alpha-amidating activity was detected. The enzyme was purified to homogeneity from the membrane fraction of porcine atria by five steps of chromatography, including an affinity chromatography using a Sepharose column coupled with a substrate, Tyr-Phe-Gly. The purified enzyme was found to be composed of a single polypeptide chain with an apparent molecular weight of 92,000. This enzyme converted several synthetic peptides with C-terminal glycine to the corresponding des-glycine peptide alpha-amides. 相似文献
43.
Enhancement of plasminogen activator activity in cultured endothelial cells by granulocyte colony-stimulating factor 总被引:1,自引:0,他引:1
A hitherto unknown function of granulocyte colony-stimulating factor (G-CSF) was found using cultured endothelial cells. G-CSF stimulated activity of plasminogen activator (PA) in both extracellular and intracellular milieus of endothelial cells obtained from bovine carotid and aortic artery. This effect was dependent on the concentration of G-CSF added to the culture medium and on the treatment time. The extracellular activity was enhanced approximately 5-fold at a concentration of 5,000 colony-forming unit (CFU)/ml (2.6 nM) and in about a 15-hr treatment period. Analyses by fibrin and reverse fibrin autography revealed that activity of PA was much more increased than that of PA inhibitor in endothelial cells treated with G-CSF. 相似文献
44.
The thiobarbituric acid (TBA) reactivity of rat liver and brain homogenates was characterized to elucidate what kinds of aldehyde species contributed to the reactivity. Characteristic pH dependence of the reactivity with a maximum at around pH 3 and marked enhancement of the reactivity by t-butyl hydroperoxide (t-BuOOH) and ferric ion were similar to those of alkadienals. The amounts of aldehyde species, including alkadienals determined as 2,4-dinitrophenylhydrazones, were high enough to account for the enhanced reactivity. The reactivity was inhibited by ethylenediaminetetraacetic acid (EDTA) but not completely, suggesting the presence of malonaldehyde whose reactivity was not affected by EDTA. The amounts of malonaldehyde determined as 1-(2,4-dinitrophenyl)pyrazole could account for a part of the reactivity in the presence of EDTA. Hence, the TBA reactivity of liver and brain homogenates at around pH 3 in the presence of t-BuOOH and ferric ion may be accounted for by alkadienals and malonaldehyde and that in the presence of EDTA by malonaldehyde. 相似文献
45.
N Kojima K Handa W Newman S Hakomori 《Biochemical and biophysical research communications》1992,189(3):1686-1694
E-selectin has a "multi-recognition" capability in terms of epitope binding specificity, depending on adhesion conditions (static vs. low- or high-shear stress dynamic systems). Specifically, (i) adhesion based on expression of alpha 2-->3 sialylated Le(x) (SLe(x)) is prominent under static or low shear stress dynamic conditions; (ii) adhesion under high shear stress dynamic conditions does not depend on the known SLe(x) species, but rather on Lex with an adjacent unidentified sialosyl substitution, which shows different susceptibility to sialidases and antibodies compared to known SLe(x). 相似文献
46.
K Takano N Yamashita I Kojima M Kitaoka A Teramoto E Ogata 《Biochemical and biophysical research communications》1992,182(3):1408-1415
Activin A stimulated synthesis and secretion of intact FSH in dispersed human FSH-secreting adenoma cells. Significant stimulation was observed after 24 hr. Activin A caused an increase in Ca2+ concentration ([Ca2+]i). This response occurred soon after the activin A action. These effects were blocked in Ca(2+)-deficient medium and by nitrendipine (5 microM). Somatostatin inhibited the activin A-induced intact FSH secretion and the [Ca2+]i response. These findings indicated that Ca2+ influx through voltage-gated Ca2+ channel was involved in the activin A induced synthesis and secretion of intact FSH. 相似文献
47.
K Maruyama T Yuda A Okamoto S Kojima A Suginaka M Iwatsuru 《Biochimica et biophysica acta》1992,1128(1):44-49
The effect of poly(ethylene glycol) (PEG) on the circulation time of liposomes in mice was examined by employing amphipathic PEGs (phosphatidylethanolamine (PE) derivatives of PEG) with average molecular weights of 1000, 2000, 5000 and 12,000. The activity of dioleoyl phosphatidylethanolamine-PEG (DOPE-PEG) in prolonging the circulation time of egg phosphatidylcholine/cholesterol large unilamellar liposomes (ePC/CH LUVs) (200 nm) was proportional to the molecular weight of PEG, i.e., 12000 = 5000 greater than 2000 greater than 1000. On the other hand, inclusion of distearoylphosphatidylethanolamine-PEG (DSPE-PEG) or dipalmitoyl-phosphatidylethanolamine-PEG (DPPE-PEG) of low molecular weight such as 1000 and 2000 in distearoylphosphatidylcholine (DSPC)/CH LUVs or dipalmitoyl phosphatidylcholine (DPPC)/CH LUVs effectively increased their blood circulation time. At least 3 mol% of amphipathic PEG in liposomes was required for activity. Addition of CH, which has a bilayer-tightening effect, to DSPC/CH/DSPE-PEG2000 LUVs further increased the blood residence time. A size of less than 300 nm was essential for prolonging the residence time of amphipathic PEG-containing liposomes in blood. DSPC/CH/DSPE-PEG2000 LUVs (1:1:0.13, m/m) containing 6 mol% of PEG and 200 nm in diameter remained in the circulation for over 24 h after injection and may be clinically useful for sustained release of an entrapped drug in the bloodstream and for drug accumulation in solid tumors. 相似文献
48.
Haruko Ogawa Ako Hijikata Maho Amano Kyoko Kojima Hisako Fukushima Ineo Ishizuka Yoshie Kurihara Isamu Matsumoto 《Glycoconjugate journal》1996,13(4):555-566
The oligosaccharide structures ofCry j I, a major allergenic glycoprotein ofCryptomeria japonica (Japanese cedar, sugi), were analysed by 400 MHz1H-NMR and two-dimensional sugar mapping analyses. The four major fractions comprised a series of biantennary complex type N-linked oligosaccharides that share a fucose/xylose-containing core and glucosamine branches including a novel structure with a nongalactosylated fucosylglucosamine branch.Rabbit polyclonal anti-Cry j I IgG antibodies cross-reacted with three different plant glycoproteins having the same or shorter N-linked oligosaccharides asCry j I. ELISA and ELISA inhibition studies with intact glycoproteins, glycopeptides and peptides indicated that both anti-Cry j I IgGs and anti-Sophora japonica bark lectin II (B-SJA-II) IgGs included oligosaccharide-specific antibodies with different specificities, and that the epitopic structures against anti-Cry j I IgGs include a branch containing 1–6 linked fucose and a core containing fucose/xylose, while those against anti-B-SJA-II IgGs include nonreducing terminal mannose residues. The cross-reactivities of human allergic sera to miraculin andClerodendron Trichotomum lectin (CTA) were low, and inhibition studies suggested that the oligosaccharides onCry j I contribute little or only conformationally to the reactivity of specific IgE antibodies.Abbreviations
Cry j I
a major allergenic glycoprotein ofCryptomeria japonica
- B-SJA-II
Sophora japonica bark lectin II
- CTA
Clerodendron trichotomum lectin
- TFMS
trifluoromethanesulfonic acid
- HRP
horseradish peroxidase 相似文献
49.
50.
Wehrman ME Fike KE Kojima FN Bergfeld EG Cupp AS Mariscal V Sanchez T Kinder JE 《Theriogenology》1996,45(3):593-610
The synchronization of estrus with synthetic progestins or progesterone (P(4)) results in the development of a large, persistent ovarian follicle. The objectives of the present study were to determine if development of a persistent ovarian follicle during synchronization of estrus suppresses recruitment of additional follicles during FSH treatment. On Day 5 of the estrous cycle (estrus = Day 0), beef cows were treated with 0.5 or 2.0 P(4) releasing intravaginal devices (PRIDs) for 8 d (Experiment 1, n = 20), 5 or 2 d (Experiment 2, n = 44) before initiation of FSH treatment. Prostaglandin F(2alpha) (25 mg) was administered on Days 5 and 6. Superovulation was induced with 24 mg of recombinant bovine FSH (rbFSH, Experiment 1) or 28 mg of FSH-P (Experiment 2) over a 3- or 4-d period, respectively. The PRIDs were removed concurrently with the 5th injection of rbFSH or FSH-P. There was a treatment-by-day interaction (P < 0.001) for the concentration of 17beta-estradiol in cows treated for 8, 5 or 2 d before FSH treatment. In Experiment 1, FSH treatment initiated 8 d after insertion of a 0.5 PRID did not affect the number of CL (6.9 +/- 1.4 vs 6.7 +/- 1.6), ova/embryos (3.7 +/-1.3 vs 3.0 +/- 1.3) and transferable embryos (2.4 +/- 0.9 vs 3.0 +/- 0.9) compared with that of the 2.0 PRIDs. In Experiment 2, FSH treatment initiated 5 d after insertion of a 0.5 PRID decreased the number of CL (4.0 +/- 0.5 vs 8.3 +/- 0.8; P < 0.001), ova/embryos (3.0 +/- 0.6 vs 5.9 +/- 1.2; P < 0.03) and transferable embryos (2.3 +/- 0.6 vs 5.1 +/- 1.0; P < 0.03) compared with that of a 2.0 PRID, respectively. Initiation of FSH treatment 2 d after insertion of a 0.5 PRID compared with a 2.0 PRID had no affect on the number of CL (8.0 +/- 2.1 vs 8.7 +/- 1.2), total ova (4.8 +/- 1.4 vs 6.9 +/- 1.4) and transferable embryos (2.9 +/- 1.2 vs 6.1 +/- 1.7). In conclusion, treatment with low doses of P(4) (0.5 PRID) for 5 d but not for 2 or 8 d before initiation of FSH treatment results in the development of a dominant ovarian follicle, which reduces recruitment of ovarian follicles, and the number of CL, total ova and transferable embryos. 相似文献