全文获取类型
收费全文 | 6370篇 |
免费 | 400篇 |
国内免费 | 3篇 |
专业分类
6773篇 |
出版年
2022年 | 30篇 |
2021年 | 48篇 |
2020年 | 26篇 |
2019年 | 41篇 |
2018年 | 67篇 |
2017年 | 59篇 |
2016年 | 90篇 |
2015年 | 145篇 |
2014年 | 169篇 |
2013年 | 352篇 |
2012年 | 320篇 |
2011年 | 326篇 |
2010年 | 204篇 |
2009年 | 204篇 |
2008年 | 330篇 |
2007年 | 317篇 |
2006年 | 295篇 |
2005年 | 302篇 |
2004年 | 311篇 |
2003年 | 343篇 |
2002年 | 305篇 |
2001年 | 206篇 |
2000年 | 231篇 |
1999年 | 190篇 |
1998年 | 86篇 |
1997年 | 79篇 |
1996年 | 69篇 |
1995年 | 69篇 |
1994年 | 58篇 |
1993年 | 60篇 |
1992年 | 128篇 |
1991年 | 126篇 |
1990年 | 115篇 |
1989年 | 112篇 |
1988年 | 107篇 |
1987年 | 81篇 |
1986年 | 82篇 |
1985年 | 54篇 |
1984年 | 71篇 |
1983年 | 57篇 |
1982年 | 47篇 |
1981年 | 34篇 |
1980年 | 33篇 |
1979年 | 48篇 |
1978年 | 39篇 |
1977年 | 33篇 |
1976年 | 28篇 |
1974年 | 36篇 |
1971年 | 28篇 |
1970年 | 29篇 |
排序方式: 共有6773条查询结果,搜索用时 7 毫秒
71.
S Harihara M Hirai Y Suutou K Shimizu K Omoto 《Human biology; an international record of research》1992,64(2):161-166
Individuals of the following Asian populations were surveyed for the presence of a 9-base-pair deletion of mitochondrial DNA (mtDNA): Ainu, Japanese, Korean, Negrito, and Vedda. Although the variation was detected in every population except the Vedda, the frequencies of the variation differed widely among the populations, suggesting a geographic cline. 相似文献
72.
T Abe T Fujino R Fukuyama S Minoshima N Shimizu H Toh H Suzuki T Yamamoto 《Journal of biochemistry》1992,111(1):123-128
A complementary DNA clone encoding the entire human long-chain acyl-CoA synthetase was isolated and the total 698-amino acid sequence was deduced. The amino acid sequence of human long-chain acyl-CoA synthetase shows 84.9% identity to that of rat long-chain acyl-CoA synthetase. The nucleotide sequences of the protein coding regions between human and rat long-chain acyl-CoA synthetase mRNAs are highly conserved (85.6%), whereas those of the 3' untranslated regions are less conserved (72%). The location of the human long-chain acyl-CoA synthetase gene was identified on chromosome 4 by spot hybridization of flow-sorted chromosomes. Computer-assisted homology search revealed a significant similarity of the enzyme with the enzymes of the luciferase family. Based on this similarity, the structure of human long-chain acyl-CoA synthetase can be divided into five domains: the N-terminus, two domains similar to those in enzymes of the luciferase family, a long gap region between the similar domains and the C-terminus. 相似文献
73.
A novel enzyme, arylalkyl acylamidase, which shows a strict specificity for N-acetyl arylalkylamines, but not acetanilide derivatives, was purified from the culture broth of Pseudomonas putida Sc2. The purified enzyme appeared to be homogeneous, as judged by native and SDS/PAGE. The enzyme has a molecular mass of approximately 150 kDa and consists of four identical subunits. The purified enzyme catalyzed the hydrolysis of N-acetyl-2-phenylethylamine to 2-phenylethylamine and acetic acid at the rate of 6.25 mumol.min-1.mg-1 at 30 degrees C. It also catalyzed the hydrolysis of various N-acetyl arylalkylamines containing a benzene or indole ring, and acetic acid arylalkyl esters. The enzyme did not hydrolyze acetanilide, N-acetyl aliphatic amines, N-acetyl amino acids, N-acetyl amino sugars or acylthiocholine. The apparent Km for N-acetylbenzylamine, N-acetyl-2-phenylethylamine and N-acetyl-3-phenylpropylamine are 41 mM, 0.31 mM and 1.6 mM, respectively. The purified enzyme was sensitive to thiol reagents such as Ag2SO4, HgCl2 and p-chloromercuribenzoic acid, and its activity was enhanced by divalent metal ions such as Zn2+, Mg2+ and Mn2+. 相似文献
74.
S Shimizu M Kataoka K Shimizu M Hirakata K Sakamoto H Yamada 《European journal of biochemistry》1992,209(1):383-390
A novel lactonohydrolase, an enzyme that catalyzes the hydrolysis of aldonate lactones to the corresponding aldonic acids, was purified 10-fold to apparent homogeneity, with a 61% overall recovery, from Fusarium oxysporum AKU 3702, through a purification procedure comprising DEAE-Sephacel, octyl-Sepharose CL-4B and hydroxyapatite chromatographies and crystallization. The molecular mass of the native enzyme, as estimated by high-performance gel-permeation chromatography, is 125 kDa, and the subunit molecular mass is 60 kDa. The enzyme contains 15.4% (by mass) glucose equivalent of carbohydrate, and about 1 mol calcium/subunit. The enzyme hydrolyzes aldonate lactones, such as D-galactono-gamma-lactone and L-mannono-gamma-lactone, stereospecifically. Furthermore, it can catalyze the asymmetric hydrolysis of D-pantoyl lactone, which is a promising chiral building block for the chemical synthesis of D-pantothenate. These reactions are reversible, and the reaction equilibrium at pH 6.0 has a molar ratio of nearly 1:1 with D-pantoyl lactone and D-pantoic acid. The Km and Vmax for D-galactono-gamma-lactone are 3.6 mM and 1440 U/mg, respectively, and those for D-galactonate are 52.6 mM and 216 U/mg, respectively. The enzyme also irreversibly hydrolyzes several aromatic lactones, such as dihydrocoumarin and homogentisic-acid lactone. 相似文献
75.
H Shimizu A Ishida-Yamamoto R A Eady 《The journal of histochemistry and cytochemistry》1992,40(6):883-888
We used colloidal gold (1-nm diameter) with silver enhancement, in conjunction with a low-temperature post-embedding immunolabeling technique, to localize several antigens in normal skin at both the light and the electron microscopic level within the same tissue blocks. Normal skin subjected to cyrofixation and cryosubstitution and embedded in Lowicryl K11M was used as a substrate. Semi-thin sections (1 micron) were incubated in primary antibody (against epidermal basement membrane zone associated antigens and two keratin sub-types), biotinylated secondary antibodies, and then in 1-nm gold-conjugated streptavidin. Finally, the 1-nm gold label was enhanced using silver staining. Labeling of both basement membrane and keratin antigens was well demonstrated, and the area in the semi-thin sections showing the best structural preservation and the greatest intensity of immunolabeling was used to identify the part of the block to be used for ultra-thin sectioning. Ultra-thin sections were treated using a similar procedure to that employed for semi-thin sections. The labeling with silver-enhanced 1-nm gold probes was intense and readily visible by electron microscopy, even at low magnification. We have found this technique to have a high degree of specificity and sensitivity for labeling both intra- and extracellular antigens in skin, with the added advantage of providing the means for studies at both light microscopic and electron microscopic level. 相似文献
76.
Both cyclooxygenase and lipoxygenase inhibitor partially restore the anorexia by interleukin-1 beta.
Y Shimomura T Inukai S Kuwabara H Shimizu M Takahashi N Sato Y Uehara Y Tanaka I Kobayashi 《Life sciences》1992,51(18):1419-1426
Since the peripheral prostaglandin synthetizing system may at least partly involved in the anorexia that follows central interleukin-1 beta (IL-1) administration, this study was undertaken to investigate the effect of ibuprofen (ip), selective cyclooxygenase blocker and AA 861, selective lipoxygenase inhibitor, on changes of food and water intake by a single injection of IL-1 (2 micrograms/rat, ip). We demonstrated that food and water intake were suppressed by peripheral administration of IL-1. Throughout the entire observation periods, suppressed food intake was partially restored to control levels by ibuprofen, while water intake completely restored. In addition, no significant differences about water/food intake were observed in the IL-1 + ibuprofen-treated groups, respectively. In the next experiment, IL-1 induced anorexia was also partially restored to the control level following pretreatment with AA 861. These results may suggest that other mechanism including lipoxygenase blocker besides prostaglandin production may be involved in IL-1 induced anorexia. 相似文献
77.
78.
79.
Tissue and subcellular distributions of an inhibitory GDP/GTP exchange protein (GDI) for the rho proteins by use of its specific antibody 总被引:3,自引:0,他引:3
K Shimizu K Kaibuchi H Nonaka J Yamamoto Y Takai 《Biochemical and biophysical research communications》1991,175(1):199-206
We have recently purified from bovine brain cytosol to near homogeneity a GDP/GTP exchange protein for the rho proteins, named rho GDI, that inhibits the dissociation of GDP from and the subsequent binding of GTP to the rho proteins. In the present study, we made a monoclonal antibody against rho GDI and studied its tissue distribution in rat and its subcellular distribution in rat cerebrum by use of this antibody. rho GDI was found in most rat tissues as described for the rho proteins. In rat cerebrum, rho GDI was mostly found in the cytosol of neuron body and synaptosome. In synaptosome, it was mainly found in the synaptic cytosol. 相似文献
80.
T Takano Z Honda T Watanabe S Uchida T Shimizu K Kurokawa 《Biochemical and biophysical research communications》1991,177(1):54-60
Distribution of platelet activating factor (PAF) receptor was examined in the guinea pig kidney. Northern blot analysis showed a single band electrophoresed just below the 28S rRNA, and the mRNA was richest in the cortex with lesser amounts in the outer and then inner medulla. Scatchard analysis of membrane fraction using [3H]WEB 2086, a specific PAF receptor antagonist, revealed a single binding site with Bmax of 522, 228, 58 fmol/mg protein for the cortex, outer medulla and inner medulla, respectively. Kd values were in the same order of magnitude (10(-8) M). These results indicate the presence of a single class of PAF receptor in the guinea pig kidney which is most abundant in the cortex. 相似文献