全文获取类型
收费全文 | 1496篇 |
免费 | 82篇 |
专业分类
1578篇 |
出版年
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 35篇 |
2014年 | 49篇 |
2013年 | 106篇 |
2012年 | 70篇 |
2011年 | 84篇 |
2010年 | 51篇 |
2009年 | 58篇 |
2008年 | 94篇 |
2007年 | 97篇 |
2006年 | 81篇 |
2005年 | 87篇 |
2004年 | 98篇 |
2003年 | 103篇 |
2002年 | 74篇 |
2001年 | 31篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 15篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有1578条查询结果,搜索用时 0 毫秒
1.
Atsunori Kashiwagi Kazuyuki Sasaki Tamio Noguchi Takehiko Tanaka 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,582(2):221-233
A factor responsible for stimulating an increase in ornithine decarboxylase activity in the liver of mice was found in tumor cell-free ascites fluid of mice 3 days after inoculation of tumor cells. The factor was purified about 70-fold in 25% yield from tumor cell-free ascites fluid. As little as 1 μg of protein of purified fraction, injected intraperitoneally into normal mice, significantly increased the activity of ornithine decarboxylase in the liver. The most active preparation of the factor formed two major protein bands on analytical polyacrylamide gel electrophoresis and both these bands stained with periodic acid-Schiff's reagent. The factor was a heat-labile, alkaline-stable, acidic protein with a molecular weight of more than 300 000. It was inactivated by treatment with 10 mM dithiothreitol, 5M urea, pronase or mixed glycosidase, but was stable on treatment with DNAase, RNAase or neuraminidase. 相似文献
2.
3.
Expression of adrenocorticotropin-releasing hormone precursor gene in placenta and other nonhypothalamic tissues in man 总被引:1,自引:0,他引:1
T Usui Y Nakai T Tsukada H Jingami H Takahashi J Fukata H Imura 《Molecular endocrinology (Baltimore, Md.)》1988,2(9):871-875
Adrenocorticotropin-releasing hormone (CRH) is a peptide originally isolated from the hypothalamus. Immunocytochemical and RIA studies have revealed that CRH-like peptide is also localized in human nonhypothalamic tissues and some tumors. To see if CRH is synthesized in these nonhypothalamic tissues and tumors, we examined preproCRH mRNA in these tissues by Northern blot analysis using a cloned human preproCRH gene as a probe. PreproCRH mRNA was detected in human hypothalamus, cerebral cortex, adrenal gland, placenta, pheochromocytoma, and thymic carcinoid. The content of preproCRH mRNA in placenta was apparently greater than that in the whole hypothalamus. 相似文献
4.
p-nitrophenyl penta-N-acetyl-beta-chitopentaoside as a novel synthetic substrate for the colorimetric assay of lysozyme 总被引:3,自引:0,他引:3
p-Nitrophenyl beta-glycosides of N-acetylchitooligosaccharides (PNP-(GlcNAc)n n = 3-5) were examined as substrates for lysozyme [EC 3.2.1.17]. The enzyme released predominantly p-nitrophenyl N-acetyl-beta-D-glucosaminide (PNP-GlcNAc) from each substrate. Furthermore, the initial rate of PNP-GlcNAc formation in lysozyme-catalyzed hydrolysis of p-nitrophenyl penta-N-acetyl-beta-chitopentaoside (PNP-(GlcNAc)5) was about 350 and 25 times faster than those of p-nitrophenyl tri-N-acetyl-beta-chitotrioside (PNP-(GlcNAc)3) and p-nitrophenyl tetra-N-acetyl-beta-chitotetraoside (PNP-(GlcNAc)4), respectively. From these results, a new colorimetric assay method of lysozyme using PNP-(GlcNAc)5 as a substrate was developed on the basis of the determination of p-nitrophenol liberated from the substrate by lysozyme through a coupled reaction involving beta-N-acetylhexosaminidase (NAHase). The assay system gave a linear dose-response curve in the range of 2-120 micrograms of lysozyme in a 15-60 min incubation. The present assay was not significantly influenced by the ionic strength of the medium and was reproducible. This method using PNP-(GlcNAc)5 as a substrate was shown to be useful for lysozyme assay. 相似文献
5.
6.
Masanori Kasahara Toshinao Takenouchi Kazumasa Ogasawara Hitoshi Ikeda Tsuguyo Okuyama Naoshi Ishikawa Junko Moriuchi Akemi Wakisaka Yuko Kikuchi Miki Aizawa Takehisa Kaneko Noboru Kashiwagi Yasuharu Nishimura Takehiko Sasazuki 《Immunogenetics》1983,17(5):485-495
To study the gene products of the HLA complex, we produced two monoclonal antibodies, termed HU-18 and HU-23. They were active in complement-dependent cytotoxicity and detected B-cell alloantigens encoded by a locus (or loci) linked to HLA. When three types of HLA-DR4 homozygous B-cell lines with different HLA-D specificities were tested for reactivity with HU-18 and HU-23, they displayed distinct reaction patterns depending on the HLA-D specificities they possessed: EBV-Wa (HLA-DYT homozygous), negative for both HU-18 and HU-23; KT2 and KOB (HLA-DKT2 homozygous), positive only for HU-18; and ER (HLA-Dw4 homozygous), positive for both. These differential reaction patterns were further confirmed by testing against a panel of 17 HLA-DR4-positive peripheral blood lymphocytes with known HLA-D specificities. Thus, these monoclonal antibodies allow us to identify HLA-DYT, HLA-DKT2, and HLA-Dw4 solely by serologic methods. This is the first clearcut serologic identification of these three HLA-DR4-associated HLA-D specificities, which have been indistinguishable by conventional serology and identified only by cellular techniques. It is hoped that immunochemical investigations using HU-18 and HU-23 will advance our understanding of the HLA-D region on a molecular level. 相似文献
7.
Takehiko Kono 《Biotechnology and bioengineering》1968,10(2):105-131
As a rate equation of microbial cell growth, the Monod equation is widely used. However, this equation cannot fully correspond to real courses of microbial cell growth in many batch cultivations. Especially, predicted values based on this equation do not agree with observed values in many continuous cultivations. In this paper, which introduces new concepts of critical concentration and coefficient of consumption activity, the growth rate equation which corresponds to the whole period including lag period is newly derived and characteristics of microbial cell growth in batch cultivation are clarified. Further, applying the new rate equation to continuous cultivation, a general equation with which to calculate cell concentration is derived and characteristics of microbial cell growth in continuous cultivation are clarified. The calculated values of cell concentration based on the new theory showed quite good agreement with the observed values in both batch and continuous cultivation. 相似文献
8.
Kaoru Nakamura Takehiko Miyai Kiyoko Inoue Seiji Kawasaki Shinzaburo Oka Atsuyoshi Ohno 《Biocatalysis and Biotransformation》1990,3(1):17-24
Esters of 3-methyl-2-oxobutanoic acid are reduced with bakers' yeast by three methods: free bakers' yeast in water, immobilized bakers' yeast in water, and immobilized bakers' yeast in hexane. Although (R)-hydroxy esters are obtained in all cases, the enantiomeric excess varies from 3% (reduction of the methyl ester with free bakers' yeast in water) to 93% (reduction of the butyl ester with immobilized bakers' yeast in hexane) depending on the structure of substrate and on the reaction conditions. The mechanism of the present stereochemical control is discussed. 相似文献
9.
Noriko Usui Kouji Matsushima Anne M. Pilaro Dan L. Longo Robert H. Wiltrout 《Biotherapy》1996,9(4):199-208
Recombinant human interleukin 1α (rh IL-1α) and etoposide (VP-16) synergize for direct growth inhibition of several human
tumor cell linesin vitro. Our previous studies demonstrated that VP-16 increased the number of membrane-associated IL-1 receptors (IL-1Rs) and also
enhanced the internalization of receptor-bound rh IL-1α. The purposes of this study were to test our hypothess that these
events were critical to the synergy between rhIL-1α and VP-16, to determine whether rhIL-1α and VP-16 synergize to increase
superoxide (SO) anion radical productionin vitro since SO anion has been implicated in the toxic effects of IL-1, and to investigate the antitumor efficacy of the combinaton
against tumors in vivo. A375/C6 melanoma cells and OVCAR-3 ovarian carcinoma cells were tested with IL-1 receptor antagonist
(IL-1ra) before exposure to rhIL-1α, VP-16 and rhIL-1α plus VP-16. The synergistic or antagonistic effects were assessed by
MTT assay. SO production was measured by reduction of cytochrome C. Athymic female mice bearing the A375/C6 melanoma were
treated by rhIL-1α, VP-16, and rhIL-1α+VP-16. The antitumor effects were evaluated by quantitating tumor growth and survival
time. Pretreatment with the IL-1ra abrogated the synergistic effects of rhIL-1α and VP-16. The production of SO radical by
A375/C6 cells was increased 2.5 fold by the combination of rhIL-1α and VP-16, and the addition of exogenous SOD blocked the
synergy between rhIL-1α and VP-16. However, when A375/S0D15 cells which over-expressed manganese superoxide dismutase (MnSOD)
after MnSOD cDNA transfecton were exposed to rhIL-1α and VP-16, in vitro antagonism was observed. In vivo studies demonstrated
that the combination of rhIL-1α and VP-16 delayed tumor growth better than either agent alone, although long-term survival
was not improved because of substantial toxicity. Our results suggest that the synergistic antitumor effects of IL-1α and
VP-16 may be due to IL-1R modulation and increased internalization of IL-1-IL-1R complex by VP-16 treatment, as well as to
a subsequent increase in SO anion radical production from the tumor cells exposed to both drugs. Thus, the combnation of IL-1α
and VP-16 might prove useful for the treatment of malignant diseasein vivo, if the increased toxicity can be reduced or managed.
The US Government’s right to retain a non-exclusive royalty-free license on and to any copyright is acknowledged. 相似文献
10.
Two-microelectrode voltage-clamp measurements were made to determine the kinetics and voltage dependence of ionic currents across the soma membrane of the Hermissenda type B photoreceptor. The voltage-dependent outward potassium currents, IA and ICa(2+)-K+, the inward voltage-dependent calcium current, ICa2+ and the light-induced current, IIgt, were then described with Hodgkin-Huxley-type equations. The fast-activating and inactivating potassium current, IA, was described by the equation; IA(t) = gA(max)(ma infinity[1-exp(-t/tau ma)])3 x (ha infinity [1-exp(-t/tau ha)] + exp(-t/tau ha)) (Vm-EK), where the parameters ma infinity, ha infinity, tau ma, and tau ha are functions of membrane potential, Vm, and ma infinity and ha infinity are steady-state activation and inactivation parameters. Similarly, the calcium-dependent outward potassium current, ICa(2+)-K+, was described by the equation, ICa(2+)-K+ (t) = gc(max)(mc infinity(VC)(1-exp[-t/tau mc (VC)]))pc (hc infinity(VC) [1-exp(-t/tau hc)] + exp(-t/tau hc(VC)])pc(VC-EK). In high external potassium, ICa(2+)-K+ could be measured in approximate isolation from other currents as a voltage-dependent inward tail current following a depolarizing command pulse from a holding potential of -60 mV. A voltage-dependent inward calcium current across the type B soma membrane, ICa2+, activated rapidly, showed little inactivation, and was described by the equation: ICa2+ = gCa(max) [1 + exp](-Vm-5)/7]-1 (Vm-ECa), where gCa(max) was 0.5 microS. The light-induced current with both fast and slow phases was described by: IIgt(t) = IIgt1 + IIgt2 + IIgt3, IIgti = gIgti [1-exp(- ton/tau mi)] exp(-ton/tau hi)(Vm-EIgti) (i = 1, 2).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献