首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3201篇
  免费   217篇
  国内免费   1篇
  2023年   14篇
  2022年   37篇
  2021年   99篇
  2020年   53篇
  2019年   66篇
  2018年   77篇
  2017年   59篇
  2016年   95篇
  2015年   129篇
  2014年   187篇
  2013年   233篇
  2012年   248篇
  2011年   242篇
  2010年   210篇
  2009年   141篇
  2008年   142篇
  2007年   162篇
  2006年   147篇
  2005年   140篇
  2004年   99篇
  2003年   99篇
  2002年   104篇
  2001年   51篇
  2000年   60篇
  1999年   43篇
  1998年   25篇
  1997年   16篇
  1996年   14篇
  1995年   20篇
  1993年   16篇
  1992年   29篇
  1991年   14篇
  1990年   14篇
  1989年   20篇
  1988年   23篇
  1987年   13篇
  1986年   21篇
  1985年   23篇
  1984年   14篇
  1982年   15篇
  1981年   11篇
  1980年   18篇
  1979年   19篇
  1978年   17篇
  1977年   9篇
  1976年   10篇
  1973年   16篇
  1972年   12篇
  1971年   11篇
  1969年   9篇
排序方式: 共有3419条查询结果,搜索用时 31 毫秒
1.
Soy-based diets have been reported to protect against the development of atherosclerosis. However, the underlying mechanism(s) for this protection remains unknown. Although atherosclerosis was traditionally considered a disease associated with impaired lipid metabolism, in recent years the inflammatory components of atherosclerosis have been explored. Recent studies have convincingly delineated that uncontrolled chronic inflammation is the principal contributing factor for the initiation and progression of atherosclerosis. Interaction between activated monocytes and vascular endothelial cells is an early event in atherogenesis. The adhesion of leukocytes, including monocytes, to the inflamed-vascular endothelium and their transmigration into intima initiate the inflammatory processes. Following transmigration, monocytes in the intima are transformed to macrophages, which take up oxidized-LDL (oxLDL) to generate lipid-laden macrophages, also known as foam cells. Hence, in this review article the inflammatory processes associated with atherosclerosis and possible anti-inflammatory functions of soy-based diets contributing to the prevention of atherosclerosis are presented.  相似文献   
2.
Summary The sporophores of Pleurotus are gymnocarpous and continuously release spores in the atmosphere causing respiratory allergies like hay fever and farmer’s lung disease among workers. The allergy is caused by the antigens present on the walls of the spores. Apart from this, during commercial production, these spores settle on the fruit bodies, germinate and form a velvety film which gives an unpleasant appearance to the mushrooms. The spores emitted may include new genotypes likely to attack wood or trees. Spore allergy is one of the most important limiting factors for the large scale cultivation of this species. Different approaches are being adopted at IIHR for the production of commercial sporeless/low-sporing strains of Pleurotus to alleviate the spore allergy problem. Attempts were made during the present investigation to produce sporeless or low-sporing mutants through u.v. mutation. Mutation of the mycelium did not yield the desired results. Mutation of the spores of Pleurotus sajor-caju yielded an extremely low-sporing mutant after 75 min exposure. The character has been found to be stable for more than 10 generations of subculturing.  相似文献   
3.
The American College of Medical Genetics and Genomics (ACMG) recommends that clinical sequencing laboratories return secondary findings in 56 genes associated with medically actionable conditions. Our goal was to apply a systematic, stringent approach consistent with clinical standards to estimate the prevalence of pathogenic variants associated with such conditions using a diverse sequencing reference sample. Candidate variants in the 56 ACMG genes were selected from Phase 1 of the 1000 Genomes dataset, which contains sequencing information on 1,092 unrelated individuals from across the world. These variants were filtered using the Human Gene Mutation Database (HGMD) Professional version and defined parameters, appraised through literature review, and examined by a clinical laboratory specialist and expert physician. Over 70,000 genetic variants were extracted from the 56 genes, and filtering identified 237 variants annotated as disease causing by HGMD Professional. Literature review and expert evaluation determined that 7 of these variants were pathogenic or likely pathogenic. Furthermore, 5 additional truncating variants not listed as disease causing in HGMD Professional were identified as likely pathogenic. These 12 secondary findings are associated with diseases that could inform medical follow-up, including cancer predisposition syndromes, cardiac conditions, and familial hypercholesterolemia. The majority of the identified medically actionable findings were in individuals from the European (5/379) and Americas (4/181) ancestry groups, with fewer findings in Asian (2/286) and African (1/246) ancestry groups. Our results suggest that medically relevant secondary findings can be identified in approximately 1% (12/1092) of individuals in a diverse reference sample. As clinical sequencing laboratories continue to implement the ACMG recommendations, our results highlight that at least a small number of potentially important secondary findings can be selected for return. Our results also confirm that understudied populations will not reap proportionate benefits of genomic medicine, highlighting the need for continued research efforts on genetic diseases in these populations.  相似文献   
4.
5.
6.
Starvation, chilling, and injury of last instar Galleria mellonella larvae typically elicit extra larval molts or a delay in pupation. The primary sites of action and the nature of the signals by which these treatments affect development are not known. However, since the connections of the brain to the nerve cord are crucial for the effects of starvation and chilling, these signals apparently affect the brain-centered program of developmental regulation via the nerve cord. Chilling, and occasionally starvation, cause extra larval molts in last instar larvae treated prior to the nervous inhibition of their corpora allata; release of a cerebral allatotropin, which stimulates the production of juvenile hormone, appears to be involved in this effect. After this time, a delay in pupation is the principal effect of starvation and chilling, and is apparently due to a temporal inhibition of the release of the prothoracicotropic hormone. Chilling also appears to inhibit unstimulated ecdysteroid production by the prothoracic glands. The effect of injury is not mediated by the nerve cord, but appears to involve an inhibitory humoral factor that affects either the brain or the prothoracic glands themselves. Injury also stimulates juvenile hormone production, an effect which is enhanced when the brain is separated from the nerve cord and which is evidenced by a delay of ecdysis and the occasional retention of some larval features in the ecdysed insects. None of the effects of these various treatments on the brain and the endocrine glands persist when the brains or glands are implanted into untreated hosts.  相似文献   
7.
The cytochalasin B (CYB)-blocked binucleated cell assay has been explored to analyze micronuclei and cell cycle kinetics using 2 known mutagenic carcinogens in V79 Chinese hamster lung cells. To determine the optimum time to obtain the maximum number of binucleated cells for micronucleus analysis, duplicate cultures of exponentially growing cells were treated with 3 micrograms/ml CYB for varying durations (8-48 h). A peak appearance of binucleated cells at 16 h in the presence of CYB suggested this as an optimum time for micronucleus analysis in binucleated V79 cells. To evaluate the capacity for induction of micronuclei in V79 cells, 2 mutagenic carcinogens, mitomycin C (0.125-1.0 micrograms/ml) and cyclophosphamide (2-12 micrograms/ml) were tested in duplicate cultures. Mitomycin C, a direct-acting alkylating agent, caused approximately an 18-fold increase in micronucleus frequency over controls at the highest concentration tested (1.0 micrograms/ml), and this increase occurred in a dose-related manner (r = 0.92). The concentrations of mitomycin C tested also caused a significant dose-related cell cycle delay, thus suggesting cytotoxicity to V79 cells. Cyclophosphamide, an indirect-acting alkylating agent, requiring the presence of S9 mix, caused approximately a 17-fold increase in micronucleus frequency over controls at the highest tested concentration (12 micrograms/ml), with a clear dose response (r = 0.99). The various concentrations of cyclophosphamide also caused cytotoxicity in a dose-related fashion. Thus, this study demonstrates the usefulness of the cytokinesis-block method in V79 cells as a possible screen to analyze micronucleus induction and cytotoxicity. Because this approach is much less labor intensive than conducting a structural chromosomal analysis, this assay has great potential both as an initial screen for clastogenic activity and as a tool for investigating the underlying mechanisms for clastogenicity.  相似文献   
8.
By baiting litter soils with raw potatoes, species of bacilli producing thermostable amylases and raw starch-degrading amylase were selectively isolated.  相似文献   
9.
The amino acid sequence for the variant-3 (CsE-v3) toxin from the venom of the scorpion Centruroides sculpturatus Ewing contains eight aromatic residues. By use of 2D NMR spectroscopic methods, the resonances from the individual protons (NH, C alpha H, C beta H',H", and the ring) for each of the individual aromatic residues have been completely assigned. The spatial arrangement of the aromatic ring systems with respect to each other has been qualitatively analyzed by 2D-NOESY techniques. The results show that Trp-47, Tyr-4, and Tyr-42 are in close spatial proximity to each other. The NOESY contacts and the ring current induced shifts in the resonances of the individual protons of Tyr-4 and Trp-47 suggest that the aromatic ring planes of these residues are in an orthogonal arrangement. In addition, the spatial proximity of the rings in the pairs Tyr-4, Tyr-58; Tyr-42, Tyr-40; and Tyr-40, Tyr-38 has also been established. A comparison with the published crystal structure suggests that there is a minor rearrangement of the aromatic rings in the solution phase. No 2D-NOESY contacts involving Phe-44 and Tyr-14 to any other aromatic ring protons have been observed. The pH dependence of the aromatic ring proton chemical shifts has also been studied. These results suggest that the Tyr-58 phenolic group is experiencing a hydrogen-bonding interaction with a positively charged group, while Tyr-4, -14, -38, and -40 are experiencing through-space interactions with proximal negatively charged groups. The Trp-47 indole NH is interacting with the carboxylate groups of two proximal acidic residues. These studies define the microenvironment of the aromatic residues in the variant-3 neurotoxin in aqueous solution.  相似文献   
10.
Summary Incubation of acetates of geraniol, citronellol and linalool with Aspergillus niger resulted in their hydrolysis to corresponding alcohols which were further hydroxylated to their respective 8-hydroxy derivatives. In the case of linalyl acetate, besides linalool and 8-hydroxylinalool, small amounts of geraniol and -terpineol were also formed. Microsomes (105 000xg sediment) prepared from induced cells of A. niger were found to convert (1-3H)citronellol to 8-hydroxy citronellol in the presence of NADPH and O2. The pH optimum for the hydroxylase was found to be 7.6.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号