全文获取类型
收费全文 | 3124篇 |
免费 | 205篇 |
出版年
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 15篇 |
2019年 | 25篇 |
2018年 | 42篇 |
2017年 | 39篇 |
2016年 | 56篇 |
2015年 | 97篇 |
2014年 | 111篇 |
2013年 | 185篇 |
2012年 | 190篇 |
2011年 | 195篇 |
2010年 | 121篇 |
2009年 | 128篇 |
2008年 | 191篇 |
2007年 | 214篇 |
2006年 | 172篇 |
2005年 | 193篇 |
2004年 | 186篇 |
2003年 | 174篇 |
2002年 | 168篇 |
2001年 | 56篇 |
2000年 | 52篇 |
1999年 | 77篇 |
1998年 | 45篇 |
1997年 | 40篇 |
1996年 | 34篇 |
1995年 | 43篇 |
1994年 | 22篇 |
1993年 | 28篇 |
1992年 | 44篇 |
1991年 | 25篇 |
1990年 | 28篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1977年 | 14篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 6篇 |
排序方式: 共有3329条查询结果,搜索用时 15 毫秒
71.
S Hattori N Ohmi M Maekawa M Hoshino M Kawakita S Nakamura 《Biochemical and biophysical research communications》1991,177(1):83-89
Cellular fractionation of GTPase activating protein (GAP) activity using bovine cerebral cortex revealed that about half of GAP activity was found in membrane fraction. GAP activity of membrane was not solubilized with 0.5% (v/v) triton X-100 and was immunoprecipitated with antibody against carboxy-terminus of neurofibromatosis type 1 (NF1) gene product. In contrast, soluble GAP activity was precipitated with antibody against GAP but not with anti-NF1. These results suggest that NF1 gene product is a GTPase activating protein toward ras p21 with completely different intracellular distribution from that of GAP. 相似文献
72.
Tomio Takamatsu Kasuhiko Yamazaki Masanori Kayano 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1992,584(2):261-266
A gas chromatographic—mass spectrometric method was developed to determine eperisone hydrochloride, 4′-ethyl-2-methyl-3-piperidinopropiophenone hydrochloride, in human plasma over the concentration range 0.2–40 ng/ml. Excellent sensitivity was achieved by selection of a favorable fragment ion, m/z 98, of eperisone and reduction of heat decomposition of eperisone by using a splitless injector and a shortened capillary column. The method described here allows the determination of plasma concentrations as low as 0.2 ng/ml, the concentration attained 6 h after a single oral administration of 50 mg. At eperisone hydrochloride concentrations higher than 0.5 ng/ml, the mean inter-day variation of accuracy of the assay was less than 12%. 相似文献
73.
Induction of DNA damage by dimethylarsine, a metabolite of inorganic arsenics, is for the major part likely due to its peroxyl radical 总被引:8,自引:0,他引:8
K Yamanaka M Hoshino M Okamoto R Sawamura A Hasegawa S Okada 《Biochemical and biophysical research communications》1990,168(1):58-64
To reveal the mechanisms of previously reported lung-specific DNA strand scissions in murine after oral administration of dimethylarsinic acid (DMAA), a main metabolite of inorganic arsenics in mammals, the ultimate substance causing DNA lesion was investigated using dimethylarsine which was a further metabolite of DMAA. The alkaline elution assay using 3H-labeled DNA showed that a major portion of the strand breaks was not suppressed by SOD and catalase, suggesting an ultimate substance other than active oxygen participated in the DNA damage. By ESR analysis, a radical estimated to be (CH3)2AsOO. was detected as a reaction product of dimethylarsine and molecular oxygen. This peroxyl radical, rather than active oxygen, was assumed to play a major role in DNA damage. 相似文献
74.
On the basis of previous data that 1,25(OH)2D3 suppressed both helper and suppressor activities of CD4 and CD8 cells in the pokeweek mitogen-stimulated culture, we examined the further effect of 1,25(OH)2D3 on both cells to define how 1,25(OH)2D3 is involved in the deterioration of their functions. 1,25(OH)2D3 suppressed the pokeweed mitogen and phytohemagglutinin-induced DNA synthesis of CD4 and CD8 cells. The suppression by 1,25(OH)2D3 of DNA synthesis was caused by a time lag in reaching maximal response. 1,25(OH)2D3 also suppressed interleukin-2 production of CD4 and CD8 cells. 1,25(OH)2D3 did not, however, affect their interleukin-2 receptor expression detected within 24 hr after phytohemagglutinin stimulation. In addition, 1,25(OH)2D3 failed to suppress DNA synthesis of CD4 and CD8 cells when cultured with a large amount of interleukin-2. Suppression by 1,25(OH)2D3 of proliferation and interleukin-2 production in CD4 and CD8 cells would bring about the decrease of their helper or suppressor functions by inhibiting their expansion or maturation. 相似文献
75.
Aggregation of human lymphoblastoid cells by tumor-promoting phorbol esters and dihydroteleocidin B 总被引:1,自引:0,他引:1
H Hoshino M Miwa H Fujiki T Sugimura 《Biochemical and biophysical research communications》1980,95(2):842-848
Human lymphoblastoid cells transformed by Epstein-Barr virus aggregated rapidly in the presence of tumor-promoting phorbol esters and dihydroteleocidin B. Cell aggregation was almost complete after incubation for 6 hours. In amounts of a few ng, they induced significant aggregation. Their abilities to aggregate cells could be measured quantitatively and correlated well with their effects in promoting skin tumors. 相似文献
76.
Transport systems for branched-chain amino acids in Pseudomonas aeruginosa. 总被引:5,自引:4,他引:1 下载免费PDF全文
T Hoshino 《Journal of bacteriology》1979,139(3):705-712
The cells of Pseudomonas aeruginosa showed high activity for leucine transport in the absence of Na+, giving a Km value of 0.34 microM. In the presence of Na+, however, two Km values, 0.37 microM (LIV-I system) and 7.6 microM (LIV-II system), were obtained. The former system seemed to serve not only for the entry of leucine, isoleucine, and valine, but also for that of alanine and threonine, although less effectively. However, the LIV-II system served for the entry of branched-chain amino acids only. The LIV-II system alone was operative in membrane vesicles, for the transport of branched-chain amino acids in membrane vesicles required Na+ and gave single Km values for the respective amino acids. When cells were osmotically shocked, the activity of the LIV-I system decreased, whereas the LIV-II system remained unaffected. The shock fluid from P. aeruginosa cells showed leucine-binding activity with a dissociation constant of 0.25 microM. The specificity of the activity was very similar to that of the LIV-I system. These results suggest that a leucine-binding protein(s) in the periplasmic space may be required for the transport process via the LIV-I system of P. aeruginosa. 相似文献
77.
A successful embalming procedure necessary for long-lasting preservation of the cadaver and its subsequent anatomical dissection has been undertaken in our laboratory. In short, the procedure consists of a preembalming treatment with blood clot disperser, removal of blood clots, drainage of blood, and arterial embalming with an embalming machine via both carotid and femoral triangles of the body. The embalming fluid is prepared from methyl alcohol and a small amount of formalin as the fixatives, ethylene glycol as a preservative, and liquefied phenol as a mould preventive. Coloring of the blood vessels is also useful in their identification. Other matters relevant to embalming problems are also discussed. 相似文献
78.
Abstract A bleomycin-resistance gene, designated blmA , has been cloned from bleomycin-producing Streptomyces verticillus by Sugiyama et al. (Gene 151 (1994) 11–16). The present study shows that Escherichia coli harboring the blmA -carrying pUC plasmid overproduced β-lactamase, encoded by an ampicillin-resistance gene on the plasmid, when cultured in the presence of bleomycin, which suggests that bleomycin may act as an inducer (or an activator) for the expression of the specific gene in the presence of blmA . We constructed a vector, designated pMAB50, which senses bleomycin and produces a pigment, using blmA and a Streptomyces tyrosinase gene located under the control of β-lactamase promoter: E. coli harboring pMAB50 produced the melanin pigment in the presence of bleomycin-type antibiotics, suggesting that the transformed E. coli can be employed as a reporter organism to screen bleomycin analogues. 相似文献
79.
Roland Seifert Jiro Hoshino Hans Kröger 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(2):259-264
The distribution of cytosolic activity of nicotinamide:S-adenosylmethionine methyltransferase (nicotinamide methylase, EC 2.1.1.1) in normal tissues from adult rat and mouse and in tumors and the change in the enzyme activity during the the development of rat tissues were studied. (1) Rat liver exhibited the highest nicotinamide methylase activity among all adult tissues tested; other rat tissues, like adrenal, pancreas, kidney, brain and mouse tissues, had only less than 15% of the adult rat liver activity. (2) 3 days before birth, fetal liver showed a very low nicotinamide methylase activity (2% of adult rat liver), which, however, increased already 1 day before birth and reached the adult level on the day 28 after birth. (3) In a variety of hepatomas and ascites tumors, an inverse correlation, with some exceptions, between tumor growth rate and nicotinamide methylase activity could be seen. In all hepatomas, with the exception of Morris hepatoma 5123tc, nicotinamide methylase activity was significantly decreased in comparison to normal adult rat liver. The highly malignant Zajdela hepatoma, Yoshida sarcoma, sarcoma 180 and Ehrlich ascites tumor methylated nicotinamide only at a negligibly low rate. (4) Cultured RLC cells (an established rat liver cell line) from the stationary growth phase or G1-arrested RLC cells had about half of the adult rat liver activity, yet the activity was 70% higher than that of the logarithmically growing RLC cells. 相似文献
80.