全文获取类型
收费全文 | 21348篇 |
免费 | 2125篇 |
国内免费 | 2193篇 |
专业分类
25666篇 |
出版年
2024年 | 57篇 |
2023年 | 281篇 |
2022年 | 735篇 |
2021年 | 1059篇 |
2020年 | 838篇 |
2019年 | 966篇 |
2018年 | 968篇 |
2017年 | 747篇 |
2016年 | 931篇 |
2015年 | 1338篇 |
2014年 | 1568篇 |
2013年 | 1671篇 |
2012年 | 1922篇 |
2011年 | 1684篇 |
2010年 | 1158篇 |
2009年 | 1003篇 |
2008年 | 1168篇 |
2007年 | 1040篇 |
2006年 | 926篇 |
2005年 | 787篇 |
2004年 | 770篇 |
2003年 | 729篇 |
2002年 | 669篇 |
2001年 | 456篇 |
2000年 | 301篇 |
1999年 | 319篇 |
1998年 | 213篇 |
1997年 | 159篇 |
1996年 | 163篇 |
1995年 | 159篇 |
1994年 | 139篇 |
1993年 | 103篇 |
1992年 | 96篇 |
1991年 | 90篇 |
1990年 | 72篇 |
1989年 | 78篇 |
1988年 | 45篇 |
1987年 | 39篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 26篇 |
1982年 | 27篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Evidence that the intestinal microbiota is intrinsically linked with overall health, including cancer risk, is emerging. Moreover, its composition is not fixed but can be influenced by several dietary components. Dietary modifiers, including the consumption of live bacteria (probiotics) and indigestible or limited digestible food constituents such as oligosaccharides (prebiotics) and polyphenols or both (synbiotics), are recognized modifiers of the numbers and types of microbes and have been reported to reduce colon cancer risk experimentally. Microorganisms also have the ability to generate bioactive compounds from food components. Examples include equol from isoflavones, enterodiol and enterolactone from lignans and urolithins from ellagic acid, which have also been demonstrated to retard experimentally induced cancers. The gastrointestinal microbiota can also influence both sides of the energy balance equation, namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Because of the link between obesity and cancer incidence and mortality, this complex complexion deserves greater attention. Overall, a dynamic interrelationship exists between the intestinal microbiota and colon cancer risk, which can be modified by dietary components and eating behaviors. 相似文献
3.
Xiao-Guo Xiang Wei-Tao Jin De-Zhu Li André Schuiteman Wei-Chang Huang Jian-Wu Li Xiao-Hua Jin Zhen-Yu Li 《PloS one》2014,9(1)
Collabieae (Orchidaceae) is a long neglected tribe with confusing tribal and generic delimitation and little-understood phylogenetic relationships. Using plastid matK, psaB, rbcL, and trnH-psbA DNA sequences and morphological evidence, the phylogenetic relationships within the tribe Collabieae were assessed as a basis for revising their tribal and generic delimitation. Collabieae (including the previously misplaced mycoheterotrophic Risleya) is supported as monophyletic and nested within a superclade that also includes Epidendreae, Podochileae, Cymbidieae and Vandeae. Risleya is nested in Collabiinae and sister to Chrysoglossum, a relationship which, despite their great vegetative differences, is supported by floral characters. Ania is a distinct genus supported by both morphological and molecular evidence, while redefined Tainia includes Nephelaphyllum and Mischobulbum. Calanthe is paraphyletic and consists four clades; the genera Gastrorchis, Phaius and Cephalantheropsis should be subsumed within Calanthe. Calanthe sect. Ghiesbreghtia is nested within sect. Calanthe, to which the disputed Calanthe delavayi belongs as well. Our results indicate that, in Collabieae, habit evolved from being epiphytic to terrestrial. 相似文献
4.
5.
6.
7.
Hyperthermic treatment at 43 degrees C suppressed the growth of Ehrlich ascites tumor (EAT) cells in vitro. Incubation of EAT cells at 43 degrees C for as little as 1.5 h totally abolished the transplantability of the tumor. At the same time, the rate of cellular glucose uptake, the density of glucose transporter on the cells as well as the extent of thymidine, uridine and leucine incorporation were significantly reduced. 相似文献
8.
K B Choo K Y Chong H F Chou L N Liew C C Liou 《Biochemical and biophysical research communications》1989,158(1):334-340
The structure of the c-myc oncogene in 17 cervical tumors and patient-matched nontumor tissues from Chinese patients residing in Taiwan was analysed. In contrast to recent reports on Mexican patients, none of the samples showed rearrangements and sequence amplification in the c-myc gene. The discrepancy may be explained by different carcinogenesis mechanisms being in operation in different geographic regions. Although no structural alterations in the c-myc gene were found in seven cervical carcinoma cell lines analysed, Northern blot analysis indicated different levels of c-myc gene expression which may be related to the presence of human papillomavirus (HPV) sequence in the cell and suggests a possible c-myc-hpv interaction in some stages of the transformation process. 相似文献
9.
10.