全文获取类型
收费全文 | 4558篇 |
免费 | 243篇 |
国内免费 | 274篇 |
专业分类
5075篇 |
出版年
2023年 | 67篇 |
2022年 | 75篇 |
2021年 | 104篇 |
2020年 | 128篇 |
2019年 | 135篇 |
2018年 | 90篇 |
2017年 | 111篇 |
2016年 | 113篇 |
2015年 | 128篇 |
2014年 | 219篇 |
2013年 | 298篇 |
2012年 | 177篇 |
2011年 | 228篇 |
2010年 | 155篇 |
2009年 | 170篇 |
2008年 | 223篇 |
2007年 | 224篇 |
2006年 | 202篇 |
2005年 | 182篇 |
2004年 | 184篇 |
2003年 | 161篇 |
2002年 | 131篇 |
2001年 | 126篇 |
2000年 | 116篇 |
1999年 | 124篇 |
1998年 | 77篇 |
1997年 | 70篇 |
1996年 | 76篇 |
1995年 | 82篇 |
1994年 | 75篇 |
1993年 | 66篇 |
1992年 | 59篇 |
1991年 | 53篇 |
1990年 | 43篇 |
1989年 | 49篇 |
1988年 | 43篇 |
1987年 | 45篇 |
1986年 | 51篇 |
1985年 | 52篇 |
1984年 | 32篇 |
1983年 | 33篇 |
1982年 | 43篇 |
1981年 | 26篇 |
1980年 | 43篇 |
1979年 | 31篇 |
1978年 | 36篇 |
1977年 | 20篇 |
1976年 | 18篇 |
1975年 | 24篇 |
1972年 | 16篇 |
排序方式: 共有5075条查询结果,搜索用时 31 毫秒
61.
Forty-eight intact and eight splenectomized cattle were used to evaluate different systems of coinfectious immunization against Babesia bigemina, Babesia argentina, and Anaplasma marginale. Coinfectious immunity was induced by two methods: (1) blood of cattle acutely infected with B. bigemina, B. argentina and A. marginale was used as the source of inoculum and the post vaccination reactions were chemotherapeutically controlled with Imidocarb, Ganaseg, Gloxazone, and Liquamycin, and (2) by artificially inducing babesiosis with the blood of carrier cattle with chronic infections of B. bigemina and B. argentina without chemotherapy. The degree of resistance was determined by bloodborne and tick-borne challenges. Ticks were collected from cattle and identified as Boophilus microplus and Dermacentor nitens. Vaccinated cattle demonstrated a high degree of resistance to babesiosis and anaplasmosis; however, cattle without coinfectious immunity were treated chemotherapeutically to prevent death losses. 相似文献
62.
63.
Piotr Popik Martyna Krawczyk Krystyna Golembiowska Gabriel Nowak Aaron Janowsky Phil Skolnick Arnold Lippa Anthony S. Basile 《Cellular and molecular neurobiology》2006,26(4-6):855-871
Summary 1. The molecular and behavioral pharmacology of DOV 102,677 is characterized.2. This characterization was performed using radioligand binding and neurotransmitter uptake assays targeting the monoamine neurotransmitter receptors. In addition, the effects of DOV 102,677 on extracellular neurotransmitter levels were investigated using in vivo microdialysis. Finally, the effects of DOV 102,677 in the forced swim test, locomotor function, and response to prepulse inhibition was investigated.3. DOV 102,677 is a novel, “triple” uptake inhibitor that suppresses [3H]dopamine (DA), [3H]norepinephrine (NE) and [3H]serotonin (5-HT) uptake by recombinant human transporters with IC50 values of 129, 103 and 133 nM, respectively. Radioligand binding to the dopamine (DAT), norepinephrine (NET), and serotonin (SERT) transporters is inhibited with k
i values of 222, 1030, and 740 nM, respectively. DOV 102,677 (20 mg/kg IP) increased extracellular levels of DA and 5-HT in the prefrontal cortex to 320 and 280% above baseline 100 min after administration. DA levels were stably increased for the duration (240 min) of the study, but serotonin levels declined to baseline by 200 min after administration. NE levels increased linearly to a maximum of 348% at 240 min post-dosing. Consistent with these increases in NE levels, the density of β-adrenoceptors was selectively decreased in the cortex of rats treated with DOV 102,677 (20 mg/kg per day, PO, 35 days).4. DOV 102,677 dose-dependently reduced the amount of time spent immobile by rats in the forced swim test, a model predictive of antidepressant activity, with a minimum effective dose (MED) of 20 mg/kg and a maximal efficacy comparable to imipramine. This decrease in immobility time did not appear to result from increased motor activity. Further, DOV 102,677 was as effective as methylphenidate in reducing the amplitude of the startle response in juvenile mice, without notably altering motor activity.5. In summary, DOV 102,677 is an orally active, “balanced” inhibitor of DAT, NET and SERT with therapeutic versatility in treating neuropsychiatric disorders beyond depression. 相似文献
64.
Continuous light can be used as a tool to understand the diurnal rhythm of plants and it can also be used to increase the plant production. In the present research, we aimed to investigate the photosynthetic performance of V. radiata under continuous light as compared with the plants grown under normal light duration. Chlorophyll a fluorescence transient (OJIP test) technique was used to understand the effect on various stages of photosynthesis and their consequences under continuous light condition. Various Chl a Fluorescence kinetic parameters such as Specific energy fluxes (per QA-reducing PSII reaction center (RC)) (ABS /RC; TR0/RC; ET0/RC; DI0/RC), phenomenological fluxes, leaf model, (ABS/CSm; TR/CSm; ETo/CSm), Quantum yields and efficiencies (φPo; φEo; Ψo) and Performance index (PIabs) was extracted and analysed in our investigation. Conclusively, our study has revealed that continuous light alters the photosynthetic performance of V. radiata at a different point but also improve plant productivity. 相似文献
65.
66.
甲真菌病是皮肤科的常见病,是由皮肤癣菌、酵母菌和非皮肤癣菌性霉菌侵犯甲板和(或)甲床所致的病变,其中由皮肤癣菌感染引起的甲真菌病称为甲癣。人甲板中角蛋白硬、厚且致密,从而形成一个完美屏障。针对甲板的特殊解剖结构,需要局部治疗药物具备穿透指甲屏障,体现高活性抗皮肤癣菌的特质。目前,甲癣的局部用药体外药效学研究没有统一的标准,缺乏指导依据。本文查阅近年来文献报道,综述甲癣局部治疗药物的体外药敏实验、药物与甲板内角蛋白亲和力实验以及药物在甲板内的渗透等,并阐述上述实验方法的模型选择、方式方法及方法间的比较,以推荐适合化合物筛选的方法。 相似文献
67.
虚拟仿真实验是一种现代信息化和智慧教学的重要方法,对高等医学院校教学质量的发展起到重要的推进作用。我们自主开发建设的“霍乱弧菌检测与防控虚拟仿真实验”,既弥补了因生物安全问题不能开展的实验教学,也解决了微生物学检验实验教学中存在的操作标准化问题。采用“三步进阶”混合教学模式,实现以“学生为中心”的师生互动模式,创建“设计性实验报告”,与育人元素有机结合,培育医学生的职业使命感。细化考核标准,实现过程性评价。探索课前启发铺垫、课中内化升华、课后巩固拓展混合式实验教学模式,有效提高学生的实验技能,实现知行合一、素能共育的教学目标。 相似文献
68.
Yamaguchi T Yamazaki T Inoue M Mashida C Kawagoe K Ogawa M Shiga S Nakagawa Y Kishimoto T Kurane I Ouchi K Ohzeki T 《FEMS immunology and medical microbiology》2005,43(1):21-27
Simkania negevensis has been associated with bronchiolitis in infants and community-acquired pneumonia in adults. Reports of exposure to this microorganism are only available from Israel, North America and Western Europe. Currently, no standard method for diagnosis of S. negevensis infection has been established nor have prevalence rates been shown in Japan. For the first time we demonstrated the ability of the microimmunofluorescence (MIF) test to detect S. negevensis-specific immunoglobulin G and exposure to S. negevensis in Japan. The positive rate in healthy volunteers was 4.3% (25/588), with rates increasing with age. Results indicate the usefulness of the MIF test as a serological method for detecting S. negevensis-specific antibodies. A standard serological test for infection with S. negevensis is needed. 相似文献
69.
Apple replant disease (ARD) is common to all major apple-growing regions in the world. It occurs when new apple trees are replanted on sites where previously the same or closely related crop species were grown. Biotic (fungi, bacteria and nematodes) and abiotic soil factors (poor soil structure, nutrition) contribute to the development and severity of ARD. However, the aetiology of ARD and effects on higher trophic levels are still unknown. In that sense, Collembola might play an important role, since they are one of the dominant mesofauna groups in many soils. They act as decomposer, fungivores and predators, representing different trophic levels in soil food webs. Therefore, any effect of ARD on the occurrence of Collembola could have ecological impacts on the soil quality and health. Here, we examined the colonization behaviour of two Collembolan species, Folsomia candida and Sinella curviseta, in choice tests and population growth tests using Apple Replant Diseased soil (ARD) and non-ARD soil samples from different field sites and standardized laboratory bioassays. Additionally, Collembola behaviour was quantified by continuous video observations to investigate short-term behavioural changes. Results showed that both Collembolan species significantly preferred colonization of the non-ARD soils compared with ARD soils, independent of the origin of the soil samples or specific disinfection treatments. Moreover, the detailed video analysis of the foraging behaviour indicates rapid colonization of soil samples and low dispersal rates. Most likely, volatile compounds and to a lesser extent feeding stimulants play a vital role for the colonization process for both Collembolan species. Finally, results showed negative effects of ARD on population growth of both Collembolan species already after an 8-week period, implying strong nutritional deficiencies in ARD affected soils. The hypothesis that ARD causing microorganisms directly affected orientation, colonization and population development of Collembola is discussed. 相似文献
70.
BackgroundTo examine changes in prostate cancer incidence and mortality rates, and 5-year relative survival, in relation to changes in the rate of prostate specific antigen (PSA) screening tests and the use of radical prostatectomy (RP) in the Australian population.MethodsProstate cancer stage-specific incidence rates, 5-year relative survival and mortality rates were estimated using New South Wales Cancer Registry data. PSA screening test rates and RP/Incidence ratios were estimated from Medicare Benefits Schedule claims data. We used multiple imputation to impute stage for cases with “unknown” stage at diagnosis. Annual percentage changes (APC) in rates were estimated using Joinpoint regression.ResultsTrends in the age-standardized incidence rates for localized disease largely mirrored the trends in PSA screening test rates, with a substantial ‘spike’ in the rates occurring in 1994, followed by a second ‘spike’ in 2008, and then a significant decrease from 2008 to 2015 (APC −6.7, 95% CI −8.2, −5.1). Increasing trends in incidence rates were observed for regional stage from the early 2000s, while decreasing or stable trends were observed for distant stage since 1993. The overall RP/Incidence ratio increased from 1998 to 2003 (APC 9.6, 95% CI 3.8, 15.6), then remained relatively stable to 2015. The overall 5-year relative survival for prostate cancer increased from 58.4% (95% CI: 55.0–61.7%) in 1981–1985 to 91.3% (95% CI: 90.5–92.1%) in 2011–2015. Prostate cancer mortality rates decreased from 1990 onwards (1990–2006: APC −1.7, 95% CI −2.1, −1.2; 2006–2017: APC −3.8, 95% CI −4.4, −3.1).ConclusionsOverall, there was a decrease in the incidence rate of localized prostate cancer after 2008, an increase in survival over time and a decrease in the mortality rate since the 1990s. This seems to indicate that the more conservative use of PSA screening tests in clinical practice since 2008 has not had a negative impact on population-wide prostate cancer outcomes. 相似文献