全文获取类型
收费全文 | 2544篇 |
免费 | 162篇 |
专业分类
2706篇 |
出版年
2022年 | 35篇 |
2021年 | 74篇 |
2020年 | 36篇 |
2019年 | 43篇 |
2018年 | 58篇 |
2017年 | 46篇 |
2016年 | 84篇 |
2015年 | 103篇 |
2014年 | 118篇 |
2013年 | 152篇 |
2012年 | 177篇 |
2011年 | 165篇 |
2010年 | 113篇 |
2009年 | 86篇 |
2008年 | 127篇 |
2007年 | 116篇 |
2006年 | 115篇 |
2005年 | 96篇 |
2004年 | 82篇 |
2003年 | 62篇 |
2002年 | 55篇 |
2001年 | 63篇 |
2000年 | 46篇 |
1999年 | 46篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1992年 | 27篇 |
1990年 | 30篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 30篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 13篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1975年 | 19篇 |
1974年 | 17篇 |
1973年 | 17篇 |
1972年 | 22篇 |
1971年 | 13篇 |
1970年 | 15篇 |
1969年 | 14篇 |
排序方式: 共有2706条查询结果,搜索用时 0 毫秒
61.
China R Mukherjee S Sen S Bose S Datta S Koley H Ghosh S Dhar P 《Microbiological research》2012,167(8):500-506
Polyphenolic extracts (PE) of edible flower of Sesbania grandiflora were tested to evaluate its antimicrobial effect against some common pathogenic bacteria and growth promoting property against probiotic organism Lactobacillus acidophilus. The antimicrobial activity of S. grandiflora flower PE against selected pathogens was evaluated using both in vitro and in situ methods. In vitro studies suggested that PE has inhibitory effect against Staphylococcus aureus, Shigella flexneri 2a, Salmonella Typhi, Escherichia coli and Vibrio cholerae. The gram-positive organism S. aureus was the most sensitive organism to PE and minimum inhibitory concentration (MIC) was found to be 0.013 mg/mL where as the MIC of PE against V. cholerae was the highest (0.25 mg/mL). On the other hand PE showed growth promoting effect on the common probiotic bacterium L. acidophilus. The major finding was that S. grandiflora PE induced a significant biomass increase of L. acidophilus grown in liquid culture media. PE showed reduction of S. aureus growth in food (fish) during storage at 10°C. High performance liquid chromatography analysis showed that rutin, a major flavonoid of the PE diminished in the culture medium MRS broth with the growth of L. acidophilus. 相似文献
62.
Mattagajasingh I Mukherjee AK Das P 《Zeitschrift für Naturforschung. C, Journal of biosciences》2006,61(7-8):583-591
Thirty-one species of Mammillaria were selected to study the molecular phylogeny using random amplified polymorphic DNA (RAPD) markers. High amount of mucilage (gelling polysaccharides) present in Mammillaria was a major obstacle in isolating good quality genomic DNA. The CTAB (cetyl trimethyl ammonium bromide) method was modified to obtain good quality genomic DNA. Twenty-two random decamer primers resulted in 621 bands, all of which were polymorphic. The similarity matrix value varied from 0.109 to 0.622 indicating wide variability among the studied species. The dendrogram obtained from the unweighted pair group method using arithmetic averages (UPGMA) analysis revealed that some of the species did not follow the conventional classification. The present work shows the usefulness of RAPD markers for genetic characterization to establish phylogenetic relations among Mammillaria species. 相似文献
63.
64.
A R Grivell M N Berry D C Henly J W Phillips P G Wallace B J Gannon D W Henderson T M Mukherjee J G Swift 《Experimental cell research》1986,165(1):11-28
The controlled centrifugation of isolated rat hepatocytes at 260 000 g results in the formation of membrane-bounded cell fragments that we have termed 'cytospheres'. A method is described for the isolation of these cytospheres. Cytospheres are spherical, have a mean diameter of 9.2 +/- 3.2 microns (SD) and a protein content of 225 +/- 12 mg/g wet wt. About 3% of the protein from the original isolated hepatocyte suspension is recoverable. Transmission electron microscopy (TEM) shows cytospheres to possess a trilaminar membrane, and a finely granular hyaloplasm generally devoid of organelles, filaments and microtubules. Freeze-fracture studies reveal a membrane structure typical of a plasma membrane. Ouabain and wheat germ agglutinin (WGA)-binding studies indicate that the original orientation of the plasma membrane is maintained throughout the formation of the cytospheres. The cytospheres have also been characterized biochemically. Cytospheres are enriched in the enzymes normally associated with the hyaloplasm, whereas the activities of enzymes localized in organelles are greatly diminished. Lipid analysis of the cytosphere membrane indicates that it is derived from the plasma membrane of the hepatocyte. Cytospheres are sensitive to changes in the osmolarity and ionic composition of their environment. Cytospheres should therefore prove a useful preparation for the study of hyaloplasm metabolism and of plasma membrane receptor and permeability properties. 相似文献
65.
Jones KS Nath M Petrow-Sadowski C Baines AC Dambach M Huang Y Ruscetti FW 《Journal of virology》2002,76(24):12723-12734
Little is known about the requirements for human T-cell leukemia virus type 1 (HTLV-1) entry, including the identity of the cellular receptor(s). Previous studies have shown that although the HTLV receptor(s) are widely expressed on cell lines of various cell types from different species, cell lines differ dramatically in their susceptibility to HTLV-Env-mediated fusion. Human cells (293, HeLa, and primary CD4(+) T cells) showed higher levels of binding at saturation than rodent (NIH 3T3 and NRK) cells to an HTLV-1 SU immunoadhesin. A direct comparison of the binding of the HTLV-1 surface glycoprotein (SU) immunoadhesin and transduction by HTLV-1 pseudotyped virus revealed parallels between the level of binding and the titer for various cell lines. When cells were treated with phorbol myristate acetate (PMA), which down-modulates a number of cell surface molecules, the level of SU binding was markedly reduced. However, PMA treatment only slightly reduced the titer of murine leukemia virus(HTLV-1) on both highly susceptible and poorly susceptible cells. Treatment of target cells with trypsin greatly reduced binding, indicating that the majority of HTLV SU binding is to proteins. Polycations, which enhance the infectivity of several other retroviruses, inhibited HTLV-1 Env-mediated binding and entry on both human and rodent cells. These results suggest that factors other than the number of primary binding receptors are responsible for the differences in the titers of HTLV-1 pseudotypes between highly susceptible cells and poorly susceptible cells. 相似文献
66.
The present study examines the role of cerebroventricular administered (IIIrd ventricle) galanin on LHRH and LH release in adult and immature male rats. In both age groups, galanin stimulated LHRH synthesis and release from the hypothalamus, leading to a higher release of pituitary LH which in turn increased plasma LH levels. Galantide, a galanin receptor blocker, on the other hand, drastically reduced hypothalamic LHRH and plasma LH while increasing pituitary LH. In vitro incubation of anterior pituitary cells with galanin followed by LHRH resulted in increased release of pituitary LH but not by galanin alone. Galantide exhibited no such effect either alone or with LHRH. These results indicate that galanin is an important regulator for both hypothalamic LHRH and hypophysial LH and its role is independent of age in the case of male rats. 相似文献
67.
Manisha Patel 《Journal of neurochemistry》1998,71(3):1068-1074
Abstract: The objective of this study was to determine whether free radicals play a pathogenic role in neuronal apoptosis. The ability of Mn(III) tetrakis(benzoic acid) porphyrin (MnTBAP), a superoxide dismutase mimic, to inhibit staurosporine-induced neuronal apoptosis was tested in mixed cerebrocortical cultures. Staurosporine produced concentration-dependent cell death that was markedly inhibited by MnTBAP. Immunocytochemical analyses of cultures for neuron- and astrocyte-specific markers revealed that high concentrations of staurosporine induced the death of both neurons and astrocytes; both cell types were protected by MnTBAP. A less active congener of MnTBAP failed to protect cells against staurosporine-induced apoptosis. MnTBAP also protected cortical cultures against ceramide-induced apoptosis. These results support a role for oxidative stress in neuronal apoptosis. 相似文献
68.
69.
70.
Visceral leishmaniasis, also known as kala-azar (KA) is generally caused byLeishmania donovani. Organic pentavalent antimonials (SbV) is the first line of treatment for KA. However, the number of KA patients unresponsive
to treatment with Sb(V) is steadily increasing in India and elsewhere. The primary objective of this work is to determine
the factor(s) associated with the rise of unresponsiveness. Analysis of the clonal population of parasites clearly indicated
that wild type parasites isolated from KA patients who were clinically cured after treatment with Sb(V), were a mixture of
resistant and sensitive cells. The resistant promastigotes were also resistant as amastigotesin vivo. It was further observed that Stibanate sensitive parasites can be made resistant to the drug by repeated passages in experimental
animals followed by incomplete treatment with suboptimal doses of the drug. These results suggest that the steady rise in
Sb(V) unresponsiveness of KA patients in India is due to infection with resistant parasites, generated as a result of irregular
and often incomplete treatment of the patients. 相似文献