全文获取类型
收费全文 | 14248篇 |
免费 | 240篇 |
国内免费 | 445篇 |
专业分类
系统科学 | 349篇 |
丛书文集 | 443篇 |
教育与普及 | 249篇 |
理论与方法论 | 146篇 |
现状及发展 | 158篇 |
研究方法 | 1篇 |
综合类 | 13581篇 |
自然研究 | 6篇 |
出版年
2024年 | 33篇 |
2023年 | 61篇 |
2022年 | 102篇 |
2021年 | 108篇 |
2020年 | 114篇 |
2019年 | 112篇 |
2018年 | 100篇 |
2017年 | 110篇 |
2016年 | 140篇 |
2015年 | 272篇 |
2014年 | 532篇 |
2013年 | 488篇 |
2012年 | 727篇 |
2011年 | 937篇 |
2010年 | 708篇 |
2009年 | 817篇 |
2008年 | 893篇 |
2007年 | 1144篇 |
2006年 | 1030篇 |
2005年 | 945篇 |
2004年 | 804篇 |
2003年 | 754篇 |
2002年 | 674篇 |
2001年 | 576篇 |
2000年 | 488篇 |
1999年 | 393篇 |
1998年 | 227篇 |
1997年 | 233篇 |
1996年 | 220篇 |
1995年 | 200篇 |
1994年 | 174篇 |
1993年 | 133篇 |
1992年 | 127篇 |
1991年 | 111篇 |
1990年 | 107篇 |
1989年 | 96篇 |
1988年 | 94篇 |
1987年 | 74篇 |
1986年 | 41篇 |
1985年 | 18篇 |
1984年 | 10篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
英国维多利亚时期"家庭天使"的内涵和特点 总被引:3,自引:0,他引:3
曾亚英 《达县师范高等专科学校学报》2005,15(4):120-121,124
英国维多利亚时期伴随工业化的深入,强大的中产阶级不仅创造了这一时期的时代价值观,而且还形成了与以往不同的妇女观."家庭天使"成为他们心目中完美的女性形象. 相似文献
72.
实践使自然世界分化出人化世界,实践是人类社会形成的基础。而且实践又是构成人类社会发展的动力,实践的这个作用一直被低估。本文着重就实践在人类社会形成和构成人类社会发展的动力方面,进行再思考和分析。 相似文献
73.
刘晓红 《西安联合大学学报》2005,8(5):75-77
20世纪上半叶中国社会经历了剧烈的变迁。农村的婚姻制度并没有在择偶方式即“父母之命,媒妁之言”上发生根本的变化。“父母之命”依然代表着农村择偶方式的主流。而在一些交通便利、距离大城市较近的农村,尤其是沿海、沿江的农村地区出现了一些新变化。择偶方式要产生根本的变化将是一个长期的过程。 相似文献
74.
对苯胺、乙醇气相N-乙基化反应催化剂的制备及其活性进行了评述,特别是对近十年来的发展作出了较详细而深入的论述,指出研制这类反应催化剂的重要性和今后的发展方向。 相似文献
75.
D. Porquet M. Appel T. Fournier O. Bertaux D. Biou J. Féger 《Cellular and molecular life sciences : CMLS》1992,48(3):257-261
Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model. 相似文献
76.
林凤彩 《沈阳大学学报:自然科学版》1992,(3)
本文主要阐述了生产净产值指标在评价企业经济效益时的弊病,并从理论上和实践上论述了在商品经济条件下采用实现净产值指标评价企业经济效益的重要性和必要性。同时介绍了实现净产值指标的两种计算方法。即:生产法、分配法。 相似文献
77.
Summary The suitability of urethane anesthesia for physiopharmacological investigations is reviewed. Total dose administered and route of administration are recognized as factors having a great influence on both resting parameters and biological responses to drugs. A peculiar characteristic of urethane is represented by its ability to induce a surgical plane of anesthesia without affecting neurotransmission in various subcortical areas and the peripheral nervous system. This makes urethane a suitable general anesthetic for studying neural function in both central and peripheral nervous systems and accounts for the preservation of a number of reflex responses in urethane-anesthetized animals. 相似文献
78.
M. -P. Sauviat J. -M. Chesnais J. Diacono J. -F. Biard J. -F. Verbist 《Cellular and molecular life sciences : CMLS》1994,50(10):926-930
Bistramide A, a new toxin isolated from the UrochordateLissoclinum bistratum Sluiter, was applied to rat auricular heart muscle bundles. At a stimulation frequency of 0.2 Hz, the toxin induces a dose-dependent reduction of the stimulated twitch tension force; it decreases
and shortens the duration of the plateau and the slow repolarizing phase of the action potential. In the control solution, switching from a stimulation frequency of 0.2 Hz to 1 Hz decreases the force with which a positive potentiation develops either at a maintained high frequency or after switching from 1 Hz to 0.2 Hz. Bistramide A reduces both the force evoked at 1 Hz and the potentiation. The data suggest that Bistramide A blocks Na+ conductance; inhibits Ca++ channels in a time-and frequency-dependent manner; reduces Na+–Ca++ exchange activity; but does not modify the ability of the sarcoplasmic reticulum to be refilled although the rate of Ca++ accumulation is decreased. 相似文献
79.
The in vivo expression of the globin genes of theβ cistron in γ-,δ-, andδβ-thalassemia heterozygotes
A. J. Dimovski A. D. Adekile T. H. J. Huisman 《Cellular and molecular life sciences : CMLS》1994,50(2):167-170
There is considerable evidence suggesting that the switch from to and chain production after birth is due, in part, to silencing of the genes by stage-specific factors which bind to their promoters and to the competition from the adult ( and ) genes for a common enhancer element located in the locus control region. As a consequence one can expect that the increased Hb F production in adults with hereditary persistence of fetal hemoglobin or -thalassemia is directed mainly by -globin genes in cis to the deletion(s) responsible for these conditions. Here we review data on heterozygotes with -, -, or -thalassemia, who also had anAT mutation, in cis or in trans, which was used as a marker of gene expression. The results show that a deletion affecting adult genes favors the expression of genes in cis, while the deletion of a single gene does not affect the expression of the gene in cis but leads to a faster switch postnatally. 相似文献
80.
Highly active metabolites have been detected in the hemolymph of the lepidopteranSpodoptera exigua infected with the mycopathogen,Beauveria bassiana. A combination of phenyl sepharose and CM ion exchange chromatography was utilized to extract the active metabolites from infected hemolymph samples. The active in vivo metabolites, having a molecular mass greater than 10 KDa, were thermolabile and were inactivated by proteinase K. These metabolites were characterized by their ability to disrupt metamorphosis, killing treated larvae at the wandering or pupal stage. Additionally, injection ofS. exigua larvae with active samples caused a reduction in the number of filopodial-producing hemocytes. The biological activities and biochemical properties suggest that novel compounds are produced duringB. bassiana mycosis. 相似文献