全文获取类型
收费全文 | 1983篇 |
免费 | 96篇 |
出版年
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 19篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 71篇 |
2014年 | 67篇 |
2013年 | 102篇 |
2012年 | 137篇 |
2011年 | 120篇 |
2010年 | 72篇 |
2009年 | 69篇 |
2008年 | 113篇 |
2007年 | 113篇 |
2006年 | 94篇 |
2005年 | 129篇 |
2004年 | 97篇 |
2003年 | 100篇 |
2002年 | 106篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 31篇 |
1998年 | 27篇 |
1997年 | 34篇 |
1996年 | 22篇 |
1995年 | 29篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 24篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1977年 | 7篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 7篇 |
1970年 | 5篇 |
1969年 | 10篇 |
排序方式: 共有2079条查询结果,搜索用时 15 毫秒
1.
Haruhide Kawabe Hiroshi Naganawa Shinichi Kondo Hamao Umezawa Susumu Mitsuhashi 《Microbiology and immunology》1978,22(9):515-521
A clinical isolate of Staphylococcus aureus resistant to gentamicin, kanamycin and 3′,4′-dideoxykanamycin B contained two enzymes capable of inactivating gentamicin, i.e., an aminoglycoside 2″-phosphotransferase and aminoglycoside acetyltransferase. 相似文献
2.
Beta-adrenergic agonists and cyclic AMP decrease intracellular resting free-calcium concentration in ileum smooth muscle 总被引:2,自引:0,他引:2
I Parker Y Ito H Kuriyama R Miledi 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1987,230(1259):207-214
Intracellular free-calcium levels were measured in strips of longitudinal smooth muscle from guinea-pig ileum; fura-2 was used as a calcium monitor. At rest the calcium concentration was about 180 nM, and this rose to 300-400 nM following electrical stimulation and during spontaneous calcium transients (all measurements at 23-25 degrees C). Isoprenaline suppressed the spontaneous calcium transients, and reduced the resting calcium level to about 130 nM. This fall in resting calcium concentration was seen even in muscle strips which did not have spontaneous activity. Elevation of intracellular cyclic AMP levels, produced by forskolin or dibutyryl cyclic AMP, mimicked the actions of isoprenaline. We conclude that the relaxant effects of beta-adrenergic agonists of visceral smooth muscle may be explained partly by a fall in intracellular resting free-calcium level, mediated via an increase in cyclic AMP. 相似文献
3.
The changes in monoamine levels of different brain regions following Japanese encephalitis virus (JEV) intraperitoneal inoculation were examined in experimentally JEV-infected mice. In addition, virus distribution was studied using infectivity assay and immuno-histochemistry of viral antigen. 1) The level of monoamines in brain tissues was not affected by 48 hours after viral inoculation, but marked effects were elicited at 96 hours after the inoculation. The cerebral concentration of 5-hydroxyindole-3-acetic acid (5 HIAA) was increased, while that of dopamine (DA) showed a decrease. Especially these alteration were observed in the cerebral cortex, but not in the cerebellum. 2) The viral growth in the brain was observed at 48 hours after the inoculation. The growth in the cerebellum, however, was found to be lower than those in other cerebral regions. 3) The viral antigen was detected in the cerebral cortex, hippocampus, mesencephalon and diencephalon in addition to the substantia nigra and striatum. From these results, it is presumed that clinical manifestation of JEV infection may involve the changes in the metabolism of neurotransmitter, especially those of DA and serotonin in the brain. 相似文献
4.
Experiments were carried out to determine the cause of individual differences in the passive cutaneous anaphylaxis (PCA) response in guinea pigs. The intensity of 4-h homologous PCA produced by anti-penicillin G serum was not markedly different among eight reactive sites on the back of a specified animal, whereas considerable individual differences were observed in the PCA response, even at a specified reactive site. PCA was significantly inhibited by an antihistaminic agent, promethazine, and the tissue histamine content was significantly reduced after PCA, suggesting histamine release as a mediator. The intensity of PCA in individual animals was highly correlated with that of the histamine-induced cutaneous reaction elicited at a site adjoining the PCA but was unrelated to skin histamine content. These results suggest that the difference in susceptibility to histamine has a considerable effect on individual differences in the PCA response in guinea pigs. 相似文献
5.
Distribution of a matrix component of the midbody during the cell cycle in Chinese hamster ovary cells 总被引:24,自引:12,他引:12
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Monoclonal antibodies were raised against isolated spindles of CHO (Chinese hamster ovary) cells to probe for molecular components specific to the mitotic apparatus. One of the antibodies, CHO1, recognized an antigen localized to the midbody during mitosis. Immunofluorescence staining of metaphase cells showed that although the total spindle area was labeled faintly, the antigen corresponding to CHO1 was preferentially localized in the equatorial region of the spindle. With the progression of mitosis, the antigen was further organized into discrete short lines along the spindle axis, and eventually condensed into a bright fluorescent dot at the midzone of the intercellular bridge between two daughter cells. Parallel immunostaining of tubulin showed that the CHO1-stained area corresponded to the dark region where microtubules are entrapped by the amorphous dense matrix components and possibly blocked from binding to tubulin antibody. Immunoblot analysis indicated that CHO1 recognized two polypeptides of mol wt 95,000 and 105,000. The immunoreaction was always stronger in preparations of isolated midbodies than in mitotic spindle fractions. The protein doublet was retained in the particulate matrix fraction after Sarkosyl extraction (Mullins, J. M., and J. R. McIntosh. 1982. J. Cell Biol. 94:654-661), suggesting that CHO1 antigen is indeed a component of the dense matrix. In addition to the equatorial region of spindles and midbodies, CHO1 also stained interphase centrosomes, and nuclei in a speckled pattern that was cell cycle-dependent. Thus, the midbody appears to share either common molecular component(s) or a similar epitope with interphase centrosomes and nuclei. 相似文献
6.
Shinichi Ikemoto Seiji Wada Masato Kamizuru Nobuyuki Hayahara Taketoshi Kishimoto Masanobu Maekawa 《Cancer immunology, immunotherapy : CII》1992,34(5):289-293
Summary The authors examined interleukin-2 (IL-2) production and interferon (IFN) production of peripheral blood mononuclear cells in 28 patients with renal cell carcinoma and 17 control subjects. The peripheral blood was obtained prior to the initiation of therapeutic procedures. The patients were divided into two groups according to tumor size, 5 cm and >5 cm. The production of IL-2 and IFN was measured by immunoradiometric assay. As a result, in the patients with tumors >5 cm, IL-2 and IFN production was impaired. However, in the patients with tumors 5 cm, IFN production was enhanced, though IL-2 production was not significantly different from that of the control subjects. There was no significant correlation between IL-2 production and IFN production. 相似文献
7.
A mitosis-specific centrosomal component was studied with a human autoantibody, SP-H, which immunostained mitotic poles and interphase nuclei, and a single polypeptide with an apparent molecular mass of 200 to 230 kDa in various lines of cultured cells. Early mitotic PtK1 cells treated with 10 micrograms/ml taxol contained short bundles of parallel microtubules around the nuclei and cell periphery. At the time of nuclear envelope breakdown, the nuclear staining by SP-H disappeared, and the antigen relocated at one end of the parallel microtubules. Determination of the microtubule polarity demonstrated that the peripheral bundles of microtubules were arranged with their minus ends directed to the cell periphery, and the SP-H antigen was specifically localized at this end. Parallel microtubules were further rearranged first into a fan-like shape, and then into completely radial structures as observed by De Brabander et al. (Int. Rev. Cytol. 101, 215-274 (1986)). The SP-H antigen was always detected at the minus end domain of such microtubule-containing structures during the transformation process. When microtubules were depolymerized by nocodazole treatment, the SP-H antigen appeared as discrete cytoplasmic foci, suggesting that the antigen may self-associate, forming multimeric structures. The antigen in mitotic HeLa cell extracts co-sedimented in vitro with exogenous brain microtubules. The microtubule-associated SP-H antigen was insensitive to ATP extraction, but was removed from microtubules by treatment with 0.5 M NaCl. Thus the 200 to 230 kDa centrosomal component could be a novel microtubule-associated protein with affinity for the minus end of microtubules, and it might play an essential role in the organization of spindle poles during mitosis. 相似文献
8.
Pharmacological and biochemical characteristics of the partially purified -aminobutyric acid (GABA)B receptor using baclofen affinity column chromatography have been examined. The Scatchard analysis of [3H]GABA binding to the purified GABAB receptor showed a linear relationship and the KD and Bmax values were 60 nM and 118 pmol/mg of protein, respectively. Although GTP and Mg2+ did not affect on the GABAB receptor binding, Ca2+ significantly increased [3H]GABA binding to the purified GABAB receptor in a dose-dependent manner and showed its maximum effect at 2 mM. The enhancement of the binding by Ca2+ was found to be due to the increase of Bmax by the Scatchard analysis. The treatments with pronase and trypsin significantly decreased the binding of [3H]GABA, but phospholipase A2 had no significant effect on the binding. In addition, treatment with glycosidases such as glycopeptidase A and -galactosidase significantly decreased the binding of [3H]GABA to the purified GABAB receptor. These results suggest that purification of the solubilized GABAB receptor by the affinity column chromatography may result in the functional uncoupling of GABAB receptor with GTP-binding protein. Furthermore, the present results suggest that cerebral GABAB receptor may be a glycoprotein and membrane phospholipids susceptible to phospholipase A2 treatment may not be involved in the exhibition of the binding activity.Special issue dedicated to Dr. Eugene Roberts. 相似文献
9.
A potential approach for gene therapy targeting hepatoma using a liver-specific promoter on a retroviral vector. 总被引:7,自引:0,他引:7
S Kuriyama M Yoshikawa S Ishizaka T Tsujii K Ikenaka T Kagawa N Morita K Mikoshiba 《Cell structure and function》1991,16(6):503-510
Recent technological advances made in molecular biology and in vitro culture of human and other mammalian cells have led to broad medical and scientific acceptance of the feasibility of gene therapy for genetic diseases. Cancer might practically be one of the attractive targets for such therapy. For the treatment of cancer, it is important to manipulate the gene of interest such that it is expressed solely in cancer cells. We have developed a tissue-specific gene expression system, based on a tissue-specific promoter on a retroviral vector. A murine ecotropic retroviral vector was constructed in which the Escherichia coli beta-galactosidase gene served as a reporter; it was expressed under control of the albumin enhancer element and promoter. The tissue specificity of this vector was first assessed in vitro, and beta-galactosidase activity was detected exclusively in hepatoma cell lines. This recombinant retrovirus was injected directly into a subcutaneous tumor composed of transplantable murine MH-134 hepatoma cells, and expression of the gene was observed in vivo. Then this recombinant retrovirus was injected via the spleen or directly into the liver, resulting in the gene expression in dividing hepatocytes in partially hepatectomized mice, but not in nondividing hepatocytes in normal mice. Gene transfer specific to dividing hepatocytes and expression by means of retroviral vectors should possess high potential for selective elimination of hepatoma cells surrounded by nondividing normal hepatocytes. 相似文献
10.
Nalidixic acid-resistant mutations of the gyrB gene of Escherichia coli 总被引:41,自引:0,他引:41
Jun-ichi Yamagishi Hiroaki Yoshida Michiko Yamayoshi Shinichi Nakamura 《Molecular & general genetics : MGG》1986,204(3):367-373
Summary DNA fragments of 3.4 kb containing the gyrB gene were cloned from Escherichia coli KL-16 and from spontaneous nalidixic acid-resistant mutants. The mutations (nal-24 and nal-31) had been determined to be in the gyrB gene by transduction analysis. Nucleotide sequence analysis of the cloned DNA fragments revealed that nal-24 was a G to A transition at the first base of the 426th codon of the gyrB gene, resulting in an amino acid change from aspartic acid to asparagine, and nal-31 was an A to G transition at the first base of the 447th codon, resulting in an amino acid change from lysine to glutamic acid. This indicates that mutations in the gyrB gene are responsible for nalidixic acid resistance. 相似文献