全文获取类型
收费全文 | 2228篇 |
免费 | 197篇 |
国内免费 | 251篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 6篇 |
妇产科学 | 5篇 |
基础医学 | 47篇 |
口腔科学 | 12篇 |
临床医学 | 54篇 |
内科学 | 79篇 |
皮肤病学 | 17篇 |
神经病学 | 23篇 |
特种医学 | 17篇 |
外科学 | 30篇 |
综合类 | 325篇 |
预防医学 | 20篇 |
眼科学 | 4篇 |
药学 | 926篇 |
中国医学 | 1066篇 |
肿瘤学 | 44篇 |
出版年
2024年 | 11篇 |
2023年 | 43篇 |
2022年 | 60篇 |
2021年 | 82篇 |
2020年 | 69篇 |
2019年 | 86篇 |
2018年 | 83篇 |
2017年 | 119篇 |
2016年 | 114篇 |
2015年 | 103篇 |
2014年 | 154篇 |
2013年 | 237篇 |
2012年 | 184篇 |
2011年 | 213篇 |
2010年 | 117篇 |
2009年 | 106篇 |
2008年 | 91篇 |
2007年 | 101篇 |
2006年 | 81篇 |
2005年 | 73篇 |
2004年 | 69篇 |
2003年 | 77篇 |
2002年 | 46篇 |
2001年 | 38篇 |
2000年 | 24篇 |
1999年 | 26篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 9篇 |
1995年 | 16篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有2676条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
目的 研究四逆汤中乌头类生物碱的溶出平衡和水解平衡。方法 利用电喷雾质谱分析,比较了制附子、四逆汤、四逆汤药渣和含有3种双酯型生物碱的混合对照品体系中的乌头碱类二萜生物碱。结果 在煎煮过程中双酯型生物碱溶解并发生水解反应,而脂类生物碱则难溶于水。乌头碱、中乌头碱、次乌头碱水溶性相近,但是次乌头碱在水中的热稳定性更高,C19二萜骨架上C3取代基(—OH或—H)的变化影响生物碱的稳定性。结论四逆汤中的乌头碱类生物碱的种类及含量由其溶解性和化学稳定性共同决定。 相似文献
5.
6.
T. foenum-graecum seed extract (100 mg/day/rat) was fed orally to male albino rats for 60 days. The sperm count and motility of cauda spermatozoa declined significantly leading to negative fertility tests. The organ weights as well as androgen dependent parameters (protein, sialic acid and fructose) were lower, revealing the reduction in circulating androgen. Cholesterol is a precursor of androgen. The increase in testicular and serum cholesterol may be co-related with its nonutilization by the system, leading to a fall in circulating androgen and hence the altered histoarchitecture observed. Therefore T. foenum-graecum extract exerts both antifertility and antiandrogenic activities. 相似文献
7.
8.
In order to identify genes which are expressed during alkaloid synthesis in an axenic culture of Claviceps sp. (strain ATCC 26245), a cDNA library from a producing culture was differentially screened with cDNA from producing (cDNA+)
and non-producing (cDNA–) cultures, respectively. Altogether, ten cDNA clones were obtained, the alkaloid-synthesis-correlated
expression of which was confirmed by Northern analyses. Evaluation of their nucleotide and derived amino-acid sequences identified
one gene unequivocally, coding for dimethylallyltryptophan-synthase (DMAT-S), the initial enzyme of the specific alkaloid
pathway. For two other genes significant homologies to known fungal genes were detected: one clone showed homology to the
Neurospora crassa ccg1 gene, coding for a clock-regulated putative general stress protein; seven cDNA clones, derived from the same gene, which
is highly expressed under these conditions, contained typical hydrophobin domains and long stretches of asparagine/glycine
repeats (like QID3 from Trichoderma harzianum), thus probably representing a cell-wall constituent. These data show that this is not only a successful approach to clone
genes specific for the alkaloid-pathway of C. purpurea, but also of genes which might be involved in the differentiation of sclerotial hyphae, the prerequisite for alkaloid synthesis.
Received: 22 November 1996 相似文献
9.
Elizabeth Knyihar-Csillik Laszlo Vecsei Andras Mihaly Robert Fenyo Ibolya Farkas Beata Krisztin-Peva Bertalan Csillik 《Annals of anatomy》2007,189(1):39-45
Vinpocetine, a derivate of vincamine, is widely used in the clinical pharmacotherapy of cerebral circulatory diseases. Herewith we report on a novel effect of vinpocetine: inhibition of retrograde axoplasmic transport of nerve growth factor (NGF) in the peripheral nerve. Blockade of retrograde transport of NGF results in transganglionic degenerative atrophy (TDA) in the segmentally related ipsilateral superficial spinal dorsal horn, which is characterized by depletion of the marker enzymes fluoride-resistant acid phosphatase (FRAP) and thiamine monophosphatase (TMP). At the same time, pain-related neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP), are depleted from lamina I-III from the segmentally related, ipsitateral Rolando substance of the spinal cord. On the basis of these experiments it is suggested that vinpocetine may result in a locally restricted decrease of nociception, that might be useful in clinical treatment of intractable pain. Pilot self-experiments support this assumption. 相似文献
10.
Elisabet Kaa 《International journal of legal medicine》1987,99(2):87-94
Summary Hundred thirty-eight samples of heroin weighing more than 0.1g seized between 1981 and 1986 were characterized according to their contents of opium alkaloids, adulterants, and diluents together with their form and color. The chemical fingerprint was used to establish a change in the heroin during the period. As compared to the first few years covered by the survey, a predominant number of the samples at the end of the period were in the base form and contained the opium alkaloids papaverine and noscapine. In particular, the concentration of noscapine as related to the heroin content of each sample had increased considerably, indicating Pakistan or Iran as being the places of origin of most of the heroin seized in Denmark at the end of the period. 相似文献