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951.
Domancar Orona‐Tamayo Natalie Wielsch Alejandro Blanco‐Labra Ales Svatos Rodolfo Farías‐Rodríguez Martin Heil 《Molecular ecology》2013,22(15):4087-4100
Myrmecophytic Acacia species produce food bodies (FBs) to nourish ants of the Pseudomyrmex ferrugineus group, with which they live in an obligate mutualism. We investigated how the FBs are protected from exploiting nonmutualists. Two‐dimensional gel electrophoresis of the FB proteomes and consecutive protein sequencing indicated the presence of several Kunitz‐type protease inhibitors (PIs). PIs extracted from Acacia FBs were biologically active, as they effectively reduced the trypsin‐like and elastase‐like proteolytic activity in the guts of seed‐feeding beetles (Prostephanus truncatus and Zabrotes subfasciatus), which were used as nonadapted herbivores representing potential exploiters. By contrast, the legitimate mutualistic consumers maintained high proteolytic activity dominated by chymotrypsin 1, which was insensitive to the FB PIs. Larvae of an exploiter ant (Pseudomyrmex gracilis) taken from Acacia hosts exhibited lower overall proteolytic activity than the mutualists. The proteases of this exploiter exhibited mainly elastase‐like and to a lower degree chymotrypsin 1‐like activity. We conclude that the mutualist ants possess specifically those proteases that are least sensitive to the PIs in their specific food source, whereas the congeneric exploiter ant appears partly, but not completely, adapted to consume Acacia FBs. By contrast, any consumption of the FBs by nonadapted exploiters would effectively inhibit their digestive capacities. We suggest that the term ‘exclusive rewards’ can be used to describe situations similar to the one that has evolved in myrmecophytic Acacia species, which reward mutualists with FBs but safeguard the reward from exploitation by generalists by making the FBs difficult for the nonadapted consumer to use. 相似文献
952.
Lauren J. Cator Justin George Simon Blanford Courtney C. Murdock Thomas C. Baker Andrew F. Read Matthew B. Thomas 《Proceedings. Biological sciences / The Royal Society》2013,280(1763)
Previous studies have suggested that Plasmodium parasites can manipulate mosquito feeding behaviours such as probing, persistence and engorgement rate in order to enhance transmission success. Here, we broaden analysis of this ‘manipulation phenotype’ to consider proximate foraging behaviours, including responsiveness to host odours and host location. Using Anopheles stephensi and Plasmodium yoelii as a model system, we demonstrate that mosquitoes with early stage infections (i.e. non-infectious oocysts) exhibit reduced attraction to a human host, whereas those with late-stage infections (i.e. infectious sporozoites) exhibit increased attraction. These stage-specific changes in behaviour were paralleled by changes in the responsiveness of mosquito odourant receptors, providing a possible neurophysiological mechanism for the responses. However, we also found that both the behavioural and neurophysiological changes could be generated by immune challenge with heat-killed Escherichia coli and were thus not tied explicitly to the presence of malaria parasites. Our results support the hypothesis that the feeding behaviour of female mosquitoes is altered by Plasmodium, but question the extent to which this is owing to active manipulation by malaria parasites of host behaviour. 相似文献
953.
954.
Bilgin Tözün 《欧洲藻类学杂志》2013,48(4):363-370
Cytological investigations are reported for two Chondria species, the Pacific species Chondria nidifica Harvey and Chondria tenuissima (Goodenough et Woodward) C. A. Agardh from the shore of the Marmara Sea in Istanbul. Nuclear division during mitosis and meiosis has been followed in somatic cells and in tetrasporangial mother cells respectively of diploid tetrasporic plants. The spherical interphase nucleus stains densely, showing many chromatin granules. Mitotic nuclei in the apical groove show a large number of chromosomes at metaphase; the chromosome number has been estimated at diakinesis to be 40 in both C. nidifica and C. tenuissima. The meiotic nuclei of tetraspore mother cells in prophase contain several relatively large nucleolar-derivatives in both species. The nucleolar derivatives disappear completely before the chromosomes begin to differentiate. In meiotic prophase the tetraspore mother cell enlarges from its original diameter. The period of the second meiotic anaphase seems to be extremely short in comparison with other nuclear phases. When the chromosomes reach the poles, they spread and subsequently form a relatively compact mass at telophase. The spindle has not been observed in C. tenuissima. Photographs are presented of nucleoli and nucleolar-derivatives in mitotic and meiotic divisions. 相似文献
955.
956.
Hiroaki Kamachi Keisuke Tanaka Ryo C. Yanagita Akira Murakami Kazuma Murakami Harukuni Tokuda Nobutaka Suzuki Yu Nakagawa Kazuhiro Irie 《Bioorganic & medicinal chemistry》2013,21(10):2695-2702
We have recently developed a simplified analog of aplysiatoxin (aplog-1) as an activator of protein kinase C (PKC) with anti-proliferative activity like bryostain 1. To identify sites in aplog-1 that could be readily modified to optimize therapeutic performance and to develop a molecular probe for examining the analog’s mode of action, substituent effects on the phenol ring were systematically examined. Whereas hydrophilic acetamido derivatives were less active than aplog-1 in inhibiting cancer cell growth and binding to PKCδ, introduction of hydrophobic bromine and iodine atoms enhanced both biological activities. The anti-proliferative activity was found to correlate closely with molecular hydrophobicity, and maximal activity was observed at a log P value of 4.0–4.5. On the other hand, an induction test with Epstein–Barr virus early antigen demonstrated that these derivatives have less tumor-promoting activity in vitro than aplog-1 regardless of the hydrophobicity of their substituents. These results would facilitate rapid preparation of molecular probes to examine the mechanism of the unique biological activities of aplog-1. 相似文献
957.
Flavonoids are plant phenolic secondary metabolites that are widely distributed in the human diet. These antioxidants have received much attention because of their neuroprotective, cardioprotective, and chemopreventive actions. While a major focus has been on the flavonoids’ antioxidant properties, there is an emerging view that many of the potential health benefits of flavonoids and their in vivo metabolites are due to modulatory actions in cells through direct interactions with proteins, and not necessarily due to their antioxidant function. This view relies on the observations that flavonoids are present in the circulation at very low concentrations, which are not sufficient to exert effective antioxidant effects. The enzyme paraoxonase 1 (PON1) is associated with high-density lipoprotein (HDL), and is responsible for many of HDLs’ antiatherogenic properties. We previously showed that the flavonoid glabridin binds to rePON1 and affects the enzyme’s 3D structure. This interaction protects the enzyme from inhibition by an atherogenic component of the human carotid plaque. Here, we broadened our study to an investigation of the structure–activity relationships (SARs) of 12 flavonoids from different subclasses with rePON1 using Trp-fluorescence quenching, modeling calculations and Cu2+-induced low-density lipoprotein (LDL) oxidation methods. Our findings emphasize the ‘protein-binding’ mechanism by which flavonoids exert their beneficial biological role toward rePON1. Flavonoids’ capacity to interact with the enzyme’s rePON1 hydrophobic groove mostly dictates their pro/antioxidant behavior. 相似文献
958.
Yoshihiro Kato Motoji Kawasaki Tomohiro Nigo Shunya Nakamura Akira Fusano Yasuhiro Teranishi Mari N. Ito Takaaki Sumiyoshi 《Bioorganic & medicinal chemistry》2013,21(18):5851-5854
A series of 2,3-disubstituted pyridines were synthesized and evaluated for their PDE4 inhibitory activity. We successfully modified undesirable cyano group of initial lead compound 2 to 4-pyridyl group with improvement of in vitro efficacy and optimized the position of nitrogen atoms in pyridine moiety and alkylene linker. The most potent compound showed significant efficacy in animal models of asthma and inflammation. 相似文献
959.
Stefanie Zimmermann Mouhssin Oufir Alejandro Leroux R. Luise Krauth-Siegel Katja Becker Marcel Kaiser Reto Brun Matthias Hamburger Michael Adams 《Bioorganic & medicinal chemistry》2013,21(22):7202-7209
In mice cynaropicrin (CYN) potently inhibits the proliferation of Trypanosoma brucei—the causative agent of Human African Trypanosomiasis—by a so far unknown mechanism. We hypothesized that CYNs α,β-unsaturated methylene moieties act as Michael acceptors for glutathione (GSH) and trypanothione (T(SH)2), the main low molecular mass thiols essential for unique redox metabolism of these parasites. The analysis of this putative mechanism and the effects of CYN on enzymes of the T(SH)2 redox metabolism including trypanothione reductase, trypanothione synthetase, glutathione-S-transferase, and ornithine decarboxylase are shown. A two step extraction protocol with subsequent UPLC–MS/MS analysis was established to quantify intra-cellular CYN, T(SH)2, GSH, as well as GS-CYN and T(S-CYN)2 adducts in intact T. b. rhodesiense cells. Within minutes of exposure to CYN, the cellular GSH and T(SH)2 pools were entirely depleted, and the parasites entered an apoptotic stage and died. CYN also showed inhibition of the ornithine decarboxylase similar to the positive control eflornithine. Significant interactions with the other enzymes involved in the T(SH)2 redox metabolism were not observed. Alongside many other biological activities sesquiterpene lactones including CYN have shown antitrypanosomal effects, which have been postulated to be linked to formation of Michael adducts with cellular nucleophiles. Here the interaction of CYN with biological thiols in a cellular system in general, and with trypanosomal T(SH)2 redox metabolism in particular, thus offering a molecular explanation for the antitrypanosomal activity is demonstrated. At the same time, the study provides a novel extraction and analysis protocol for components of the trypanosomal thiol metabolism. 相似文献
960.
J. Malcolm East 《Molecular membrane biology》2013,30(5-6):327-328
AbstractHuman lipocalin-1 interacting membrane receptor (LIMR) was the first lipocalin receptor to be identified, as a specific receptor for lipocalin-1 (Lcn1). Subsequently LIMR has been reported to interact with other ligands as well, notably with the bovine lipocalin β-lactoglobulin (BLG) and with the unrelated secretoglobin uteroglobin (UG). To study the ligand-binding behaviour of this prototypic lipocalin receptor in more detail, a system was developed for the recombinant expression of LIMR in Drosophila Schneider 2 (S2) cells, and for the subsequent solubilization and purification of the protein. The receptor forms dimers or larger oligomers when solubilized in n-dodecyl β-D-maltoside (DDM). The full-length, functional receptor was captured onto a surface plasmon resonance (SPR) chip via an α-V5 antibody, and the binding of various potential ligands was followed in time. In this way, LIMR was shown to be highly specific for Lcn1, binding the lipocalin with low micromolar to high nanomolar affinity. No interactions with any of the other putative ligands could be detected, raising doubts about the physiological relevance of the reported binding of BLG and UG to the receptor. 相似文献