全文获取类型
收费全文 | 87512篇 |
免费 | 4343篇 |
国内免费 | 3733篇 |
出版年
2023年 | 928篇 |
2022年 | 1126篇 |
2021年 | 2386篇 |
2020年 | 1803篇 |
2019年 | 2298篇 |
2018年 | 1870篇 |
2017年 | 1452篇 |
2016年 | 1995篇 |
2015年 | 3835篇 |
2014年 | 7552篇 |
2013年 | 7187篇 |
2012年 | 5642篇 |
2011年 | 6644篇 |
2010年 | 4903篇 |
2009年 | 4500篇 |
2008年 | 4748篇 |
2007年 | 4856篇 |
2006年 | 3453篇 |
2005年 | 2986篇 |
2004年 | 2095篇 |
2003年 | 1817篇 |
2002年 | 1507篇 |
2001年 | 1150篇 |
2000年 | 1025篇 |
1999年 | 946篇 |
1998年 | 869篇 |
1997年 | 749篇 |
1996年 | 735篇 |
1995年 | 889篇 |
1994年 | 776篇 |
1993年 | 813篇 |
1992年 | 766篇 |
1991年 | 716篇 |
1990年 | 635篇 |
1989年 | 594篇 |
1988年 | 575篇 |
1987年 | 500篇 |
1986年 | 425篇 |
1985年 | 748篇 |
1984年 | 1038篇 |
1983年 | 657篇 |
1982年 | 885篇 |
1981年 | 821篇 |
1980年 | 635篇 |
1979年 | 643篇 |
1978年 | 423篇 |
1977年 | 405篇 |
1976年 | 364篇 |
1974年 | 289篇 |
1973年 | 276篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Bong Jin Kim Kyung Seob Song Hyun-Hee Kong Hee-Jae Cha Meesun Ock 《The Korean journal of parasitology》2014,52(1):85-87
We encountered a patient with heavy Hymenolepis nana infection. The patient was a 44-year-old Korean man who had suffered from chronic hepatitis (type B) for 15 years. A large number of H. nana adult worms were found during colonoscopy that was performed as a part of routine health screening. The parasites were scattered throughout the colon, as well as in the terminal ileum, although the patient was immunocompetent. Based on this study, colonoscopy may be helpful for diagnosis of asymptomatic H. nana infections. 相似文献
2.
Mohamed M. Eid Samy I. El-Kowrany Ahmad A. Othman Dina I. El Gendy Eman M. Saied 《The Korean journal of parasitology》2015,53(1):51-58
Toxocariasis is a soil-transmitted helminthozoonosis due to infection of humans by larvae of Toxocara canis. The disease could produce cognitive and behavioral disturbances especially in children. Meanwhile, in our modern era, the incidence of immunosuppression has been progressively increasing due to increased incidence of malignancy as well as increased use of immunosuppressive agents. The present study aimed at comparing some of the pathological and immunological alterations in the brain of normal and immunosuppressed mice experimentally infected with T. canis. Therefore, 180 Swiss albino mice were divided into 4 groups including normal (control) group, immunocompetent T. canis-infected group, immunosuppressed group (control), and immunosuppressed infected group. Infected mice were subjected to larval counts in the brain, and the brains from all mice were assessed for histopathological changes, astrogliosis, and IL-5 mRNA expression levels in brain tissues. The results showed that under immunosuppression, there were significant increase in brain larval counts, significant enhancement of reactive gliosis, and significant reduction in IL-5 mRNA expression. All these changes were maximal in the chronic stage of infection. In conclusion, the immunopathological alterations in the brains of infected animals were progressive over time, and were exaggerated under the effect of immunosuppression as did the intensity of cerebral infection. 相似文献
3.
Water pollution from industrial Metro Łódź (ML), Poland, made the Ner River almost fishless in its middle-lower course for most of the 19th and 20th century. The new sewage treatment plant of ML and reduction of industry have caused pollution abatement there since the 1990s. As a result, the Ner became repopulated, which was shown by fish samples collected along its course in 2000–2012. Multivariate statistical methods helped distinguish unpolluted (I and II, in the upper course), and recovered (III, IV and V, in the middle-lower course) sections of the river. Historical and present data indicated that section III (downstream of ML) recovered least, both before and during the study. Section V (outflow one) recovered most and its fish fauna (almost exclusively native) now displays high and stable biomass, abundance and species richness, including those of obligatory riverine species. Non-native Prussian carp's dominance followed the river degradation gradient, i.e. was highest in section III, and in section V declined to almost absence. This study shows that the revival of native fish fauna seems to be a method of restricting the dominance of this highly tolerant species. Despite the abatement, storm events are very harmful to fish (mostly in section III), because the Ner discharge may then increase manifold and all storm water is drained by the ML combined sewer system to the Ner in several hours. Other stressors are numerous dams and desorption of pollutants from sediment in the middle Ner, and perhaps pollutant inflow from agriculture or local urban areas. Some moderation of storm impact on water entering the Ner from ML by constructing buffer reservoirs would probably cause further fish recovery in section III. 相似文献
4.
5.
Ana Rodríguez Takehiko Shimada Magdalena Cervera Ana Redondo Berta Alquézar María Jesús Rodrigo Lorenzo Zacarías Lluís Palou María M López Leandro Pe?a 《Plant signaling & behavior》2015,10(6)
Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores. 相似文献
6.
7.
Abstract: Age-related changes in the expression of Na,K-ATPase α1- and α3-isoform mRNAs were analyzed by in situ hybridization in the Fischer-344 rat hippocampus. Quantification of signal density with cRNA probes in rat hippocampus at 3 months of age showed (a) α1 content is 1.5 times higher in granule than in pyramidal cell layers, whereas α3 content shows the opposite ratio and (b) α3 label is found in large clusters related to mossy cells and basket cells and in medium clusters corresponding to interneurons within the dendritic fields of CA1–3. In the 24-month-old rats as compared with the young animals, the α1 signal is increased more than sevenfold in the dendritic fields and is not significantly changed in perikaryal layers. The α3 signal is reduced about threefold ( p < 0.0001, ANOVA, n = 6) in perikaryal layers, is almost completely absent over the interneurons, basket cells, and mossy cells, and is not significantly changed in dendritic fields. These data indicate age-related, cell- and isoform-specific alterations in pretranslational regulation of Na,K-ATPase α isoforms. The striking changes in the dendritic fields, mossy cells, and GABAergic basket cells and interneurons may constitute early and sensitive markers for age-related alterations in hippocampal function, before cell loss. 相似文献
8.
Alan Agresti Atalanta Ghosh Matilde Bini 《Biometrical journal. Biometrische Zeitschrift》1995,37(7):811-820
Several authors have noted the dependence of kappa measures of inter-rater agreement on the marginal distributions of contingency tables displaying the joint ratings. This paper introduces a smoothed version of kappa computed after raking the table to achieve pre-specified marginal distributions. A comparison of kappa with raked kappa for various margins can indicate the extent of the dependence on the margins, and can indicate how much of the lack of agreement is due to marginal heterogeneity. 相似文献
9.
Summary The location, number and size of the motoneurons innervating the ischiocavernosus muscle, identified by means of horseradish-peroxidase (HRP) retrograde transport, were studied (1) in adult untreated male rats, (2) in adult male rats castrated before puberty, and (3) in adult male rats castrated before puberty and injected with testosterone from the day of castration. After injection of HRP into the ischiocavernosus muscle, labeled motoneurons were found in the dorsolateral and dorsomedial columns of the lamina IX, at the level of L6 and S1 segments of the spinal cord. Morphometric analysis demonstrated that prepubertal castration induces a statistically significant reduction in the somatic and nuclear areas (40% and 35%, respectively, if compared to those of the control rats) of both the dorsolateral and dorsomedial motoneurons, but does not affect their number. The effects of castration are prevented by exogenous testosterone.Preliminary results were presented at the International Conference on Hormones, Brain and Behaviour, Liège, Belgium, August, 1989 相似文献
10.