全文获取类型
收费全文 | 11184篇 |
免费 | 701篇 |
国内免费 | 6篇 |
出版年
2022年 | 45篇 |
2021年 | 135篇 |
2020年 | 87篇 |
2019年 | 94篇 |
2018年 | 156篇 |
2017年 | 122篇 |
2016年 | 205篇 |
2015年 | 315篇 |
2014年 | 388篇 |
2013年 | 726篇 |
2012年 | 618篇 |
2011年 | 625篇 |
2010年 | 407篇 |
2009年 | 402篇 |
2008年 | 677篇 |
2007年 | 675篇 |
2006年 | 603篇 |
2005年 | 629篇 |
2004年 | 651篇 |
2003年 | 576篇 |
2002年 | 519篇 |
2001年 | 258篇 |
2000年 | 251篇 |
1999年 | 214篇 |
1998年 | 138篇 |
1997年 | 129篇 |
1996年 | 101篇 |
1995年 | 99篇 |
1994年 | 108篇 |
1993年 | 77篇 |
1992年 | 159篇 |
1991年 | 132篇 |
1990年 | 148篇 |
1989年 | 151篇 |
1988年 | 124篇 |
1987年 | 91篇 |
1986年 | 96篇 |
1985年 | 113篇 |
1984年 | 98篇 |
1983年 | 72篇 |
1982年 | 66篇 |
1981年 | 74篇 |
1980年 | 50篇 |
1979年 | 66篇 |
1978年 | 43篇 |
1977年 | 44篇 |
1976年 | 39篇 |
1975年 | 40篇 |
1974年 | 38篇 |
1973年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
K Murata Y Fukuda M Shimosaka K Watanabe T Saikusa A Kimura 《Applied and environmental microbiology》1985,50(5):1200-1207
The gene responsible for the methylglyoxal resistance of Saccharomyces cerevisiae was cloned, and its phenotypic characteristics were investigated. S. cerevisiae cells with the gene could accumulate large amounts of glutathione in the medium and should remarkably high resistance to various toxic compounds such as methylglyoxal, tetramethylthiuram disulfide, iodoacetamide, and heavy-metal ions. The gene was also expressed in Escherichia coli cells, and the resistance of E. coli cells to toxic compounds also increased as observed for S. cerevisiae cells. The phenotypic characteristics of the gene were applicable to the selection of the transformants of wild-type yeast strains having no genetic markers. 相似文献
92.
On the basis of anatomical and physiological results of the vertebrate retina, a method is proposed for analysing the respective fields of ganglion cells in the cat retina. In the model, we assume the following: (a) Ganglion cells receive their input from bipolar and/or amacrine cells. (b) The nonlinearity of ganglion cell responses is due to the activities of transient type amacrine cells. The method has been proved to be effective. According to the results of this investigation, the receptive field properties of X type and Y type ganglion cells are heterogeneous. Thus, it may be considered that their receptive fields consist of center and surround mechanisms. The receptive field properties of X-cells are almost linear and the X-cells seem to receive most of their input from bipolar cells. On the other hand, the ones of Y-cells are highly nonlinear. Consequently, it is conceivable that the Y-cells receive their input mainly from transient type amacrine cells. 相似文献
93.
94.
Level of translatable messenger RNA coding for argininosuccinate synthetase in the liver of the patients with quantitative-type citrullinemia 总被引:2,自引:0,他引:2
Mariko Sase Keiko Kobayashi Yasushi Imamura Takeyori Saheki Kyoko Nakano Satoshi Miura Masataka Mori 《Human genetics》1985,69(2):130-134
Summary The translation activity of mRNA coding for argininosuccinate synthetase in total RNA extracted from the liver of three patients with quantitative-type citrullinemia was determined using a cell-free translation system. In two patients, the hepatic content of the enzyme was about 20% of the control value, whereas translatable mRNA level for the enzyme was similar to or slightly lower than those of control livers. In the third patient, the enzyme content was about 50% of the control value, and mRNA activity for the enzyme was low normal. These results indicate that at least in the first two patients, the decrease in the enzyme protein is due either to increased degradation of the enzyme or to decreased translation in the patient's liver. 相似文献
95.
Koji Yamada Masumi Ohtsu Genki Kimura 《In vitro cellular & developmental biology. Plant》1985,21(8):428-432
Summary Sodium butyrate causes proliferation arrest with a G2 (4C) DNA content and induces formation of tetraploid cells upon removal
of the inhibitor, in rat 3Y1 diploid fibroblasts. We isolated tetraploid clones from the butyrate-treated 3Y1 cells with high
efficiency; among 21 clones randomly isolated, 5 were pure diploid, 7 were mainly tetraploid with a small contaminating diploid
population, and 7 were pure tetraploid. Among the pure tetraploid clones, two showed doubled chromosome numbers with slightly
broader distributions than that seen in parental 3Y1 cells. Butyrate further induced polyploid formation in the tetraploid
cells thus produced, but octaploid cells that resulted could not be maintained for prolongeed, cultivation. We found no difference
between the tetraploid and the (parental and parallel isolated) diploid clones in terms of colony-forming ability, proliferation
rate, and sensitivity to density-dependent inhibition of proliferation. These results suggest that doubling of chromosome
number by itself does not cause a change in proliferation property. The tetraploid clones had lower average saturation densities
possibly due to enlargement of cell size represented by higher cellular protein content. 相似文献
96.
Effects of glucagon on the redox states of cytochromes in mitochondria in situ in perfused rat liver 总被引:1,自引:0,他引:1
S Kimura T Suzaki S Kobayashi K Abe E Ogata 《Biochemical and biophysical research communications》1984,119(1):212-219
The effects of glucagon on the respiratory function of mitochondria in situ were investigated in isolated perfused rat liver. Glucagon at the concentrations higher than 20 pM and cyclic AMP (75 microM) stimulated hepatic respiration, and shifted the redox state of pyridine nucleotide (NADH/NAD) in mitochondria in situ to a more reduced state as judged by organ fluorometry and beta-hydroxybutyrate/acetoacetate ratio. The organ spectrophotometric study revealed that glucagon and cyclic AMP induced the reduction of redox states of cytochromes a(a3), b and c+c1. Atractyloside (4 micrograms/ml) abolished the effects of glucagon on these parameters and gluconeogenesis from lactate. These observations suggest that glucagon increases the availability of substrates for mitochondrial respiration, and this alteration in mitochondrial function is crucial in enhancing gluconeogenesis. 相似文献
97.
Satoshi Yoshida Masazumi Takeshita Akihiko Kawaguchi 《Biochemical and biophysical research communications》1984,124(2):322-328
The elongation of arachidoyl-CoA by swine cerebral microsomes resulted in the production of behenic acid (22:0) and lignoceric acid (24:0) concomitantly. When 4S-[4-2H1]NADPH was used for the elongation of arachidoyl-CoA, the incorporation of two deuterium atoms into 22:0 was observed by the technique of mass fragmentography. Furthermore, the incorporation of four deuterium atoms into 24:0 was also detected. On the other hand, when 4R-[4-2H1]NADPH was used, no deuterium was incorporated into the elongated products. 相似文献
98.
Adrenocorticotropic hormone-mediated changes in rat adrenal mitochondrial phospholipids 总被引:1,自引:0,他引:1
We examined the subcellular localization of ACTH (adrenocorticotropic hormone)-induced changes in adrenal phospholipids using dexamethasone-treated rats. In adrenal mitochondrial fraction, ACTH significantly enhanced both concentrations and contents of phosphatidylinositol (37%), phosphatidylcholine (22%), and phosphatidylethanolamine (20%). Other mitochondrial phospholipids including cardiolipin did not change upon administration of ACTH. In adrenal plasma membrane, endoplasmic reticulum, and peroxisomes, no increase in phospholipids was observed. The ACTH-induced increases in mitochondrial phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine were specific to adrenal among tissues tested. These changes were observed specifically in cortical cells rather than medulla. Nonsteroidogenic ACTH fragments and related peptides were unable to induce the change in adrenal mitochondrial phospholipids. From the dose-response profile with ACTH, the changes in mitochondrial phospholipids were closely related to ACTH-dependent stimulation of steroidogenesis. Furthermore, in vitro treatment with cyclic AMP enhanced both concentrations and contents of mitochondrial phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine similar to those by the in vivo administration of ACTH. Both in vivo and in vitro experiments revealed that the hormone-induced changes in mitochondrial phospholipids were sensitive to a protein-synthesis inhibitor, cycloheximide. However, aminoglutethimide and cytochalasin B, which strongly inhibited the hormone-induced formation of corticosterone, did not affect the increases in mitochondrial phospholipids. These results suggest that the hormone-induced increases in these phospholipids occur between ACTH-mediated ribosomal protein synthesis and corticosterone formation. 相似文献
99.
An anti-I-Ab monoclonal antibody, designated K14.83-11, was produced in a fusion between SP 2/0 Ag-14 myeloma cells and spleen cells from a B10.D2/n mouse primed in vivo against C57BL/10. Unlike other anti-I-Ab monoclonal antibodies thus far described, K14.83-11 was found to have a combination of features involving specificity, isotype, and function, unique among existing anti-I-A reagents. K14.83-11 exhibited a strong binding to the I-Ab gene product, with only slight cross-reactivity to the I-Ap/q family of allelic products and no reactivity towards I-Ak,d. When analyzed for isotype, K14.83-11 was found to be of a rare IgG3 isotype. With respect to biologic activity, K14.83-11 not only failed to produce the expected inhibition of specific anti-I-Ab T cell reactivity in vitro, but instead produced a striking enhancement of T cell responses against the I-Ab gene product. The possible relationship of IgG isotype and function was suggested when the immunoenhancing effect of K14.83-11 on reactive T lymphocytes was reversed to that of suppression with highly purified F(ab)2 fragments obtained by pepsin digestion. 相似文献
100.