全文获取类型
收费全文 | 2145篇 |
免费 | 217篇 |
国内免费 | 2篇 |
专业分类
2364篇 |
出版年
2023年 | 14篇 |
2022年 | 30篇 |
2021年 | 32篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 24篇 |
2017年 | 23篇 |
2016年 | 43篇 |
2015年 | 99篇 |
2014年 | 113篇 |
2013年 | 134篇 |
2012年 | 156篇 |
2011年 | 160篇 |
2010年 | 99篇 |
2009年 | 81篇 |
2008年 | 103篇 |
2007年 | 88篇 |
2006年 | 126篇 |
2005年 | 92篇 |
2004年 | 88篇 |
2003年 | 74篇 |
2002年 | 72篇 |
2001年 | 66篇 |
2000年 | 70篇 |
1999年 | 56篇 |
1998年 | 19篇 |
1997年 | 25篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 24篇 |
1991年 | 32篇 |
1990年 | 13篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 19篇 |
1986年 | 31篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 9篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1975年 | 15篇 |
1973年 | 9篇 |
1966年 | 6篇 |
排序方式: 共有2364条查询结果,搜索用时 15 毫秒
101.
102.
Chen GS Chen CS Chien TC Yeh JY Kuo CC Talekar RS Chern JW 《Nucleosides, nucleotides & nucleic acids》2004,23(1-2):347-359
The Mitsunobu reaction was applied to prepare, in one step, purine N(3),5'-cyclonucleosides 10a-d. A subsequent ring opening in the ribose moiety of the resultant N(3),5'-nucleosides by sodium periodate led to the corresponding N(3),5'-cyclo-2',3'-seconucleosides. These products consist of 5-, 6-, and 7-membered tricyclic system which is the basic skeleton of TIBO derivatives, known antiviral agents. 相似文献
103.
Chiu-Chung Young Ta-Chen Lin Mao-Song Yeh Fo-Ting Shen Jo-Shu Chang 《World journal of microbiology & biotechnology》2005,21(8-9):1409-1414
Summary An indigenous strain Gordonia alkanivorans CC-JG39 was isolated from oil-contaminated sludge of a local gas station located in central Taiwan. The bacterial isolate
was able to grow on diesel-containing Bushnell–Haas medium and also tolerate various chemical additives frequently used in
petroleum products (e.g. BETX, methyl-tert-butyl ether, and naphthalene). Kinetics of diesel-limited cell growth and biodegradation
of diesel followed a Monod-type model. The kinetic constants for cell growth (μmax and KS,G) were 0.158 h−1 and 3196 mg/l, respectively, while those for biodegradation of diesel (vmax, diesel and KS,D) were 3.59 mg/h/mg cell and 2874 mg/l, respectively. G. alkanivorans CC-JG39 produced extracellular surface-active material, leading to a low surface tension of nearly 33 mN/m. The CC-JG39 strain
also possessed the ability to float towards the oil/water interface. These features might play some roles in enhancing the
mass transfer efficiency between oil substrate and the bacterial cells. Therefore, G. alkanivorans CC-JG39 may have potential applications in bioremediation of oil pollution sites. 相似文献
104.
Molecular cloning and characterization of human AOS1 and UBA2, components of the sentrin-activating enzyme complex 总被引:10,自引:0,他引:10
Sentrin-1/SUMO-1 is a novel ubiquitin-like protein, which can covalently modify a limited number of cellular proteins. Here we report the identification of the sentrin-activating enzyme complex, which consists of two proteins AOS1 and UBA2. Human AOS1 is homologous to the N-terminal half of E1, whereas human UBA2 is homologous to the C-terminal half of E1. The human UBA2 gene is located on chromosome 19q12. Human UBA2 could form a beta-mercaptoethanol-sensitive conjugate with members of the sentrin family, but not with ubiquitin of NEDD8, in the presence of AOS1. Identification of human UBA2 and AOS1 should allow a more detailed analysis of the enzymology of the activation of ubiquitin-like proteins. 相似文献
105.
106.
The rate of DNA synthesis in the parotid salivary gland of adult mice is very low. We have purified about 5 000-fold a mitogen from the aceIlular ascitic fluid of the Ehrlich ascites carcinoma which stimulates DNA synthesis in the parotid salivary gland in vivo. This stimulation of DNA synthesis was produced with a protein concentration of this mitogen of 3 μg per 25 g of body weight. The purification procedure included ammonium sulfate fractionation and DEAE Sephacel column chromatography. This potent, heat-labile mitogen is presumed to be a protein with a mol.wt, of 3.5×103 to 1.3×104. The data indicate that this new factor is quite different from epidermal growth factor and tumor growth factor. Hypophysectomy did not prevent the stimulatory effect of this mitogen on the parotid salivary gland, indicating that the pituitary gland is not involved directly in mediating the mitogenic effect. 相似文献
107.
Jung-Yong Yeh 《BMC veterinary research》2014,10(1):1-4
Background
The importance of the wild boar as a reservoir of Lawsonia intracellularis was assessed by investigating the seroprevalence of this pathogen among wild boars in the Republic of Korea. The extent of exposure to L. intracellularis among wild boars (Sus scrofa coreanus) was monitored by a country-wide serological survey using an immunoperoxidase monolayer assay.Results
In this study, antibodies to L. intracellularis were observed in 165 of 716 clinically healthy wild boars tested. The overall apparent prevalence calculated directly from the sample and the true prevalence calculated based on the accuracy of the test method were 23.0% (95% confidence interval: 20.0-26.3%) and 25.6% (95% confidence interval: 23.9-27.2%), respectively. Serologically positive animals were found in all the tested provinces.Conclusions
Our results confirm that L. intracellularis is present in the wild boar population worldwide, even in Far East Asia. Despite the high seroprevalence shown in wild boars, further studies are warranted to evaluate their potential as a reservoir species because seroprevalence does not prove ongoing infection nor shedding of the bacteria in amounts sufficient to infect other animals. It should also be determined whether the wild boar, like the domestic pig, is a natural host of L. intracellularis. 相似文献108.
109.
Y C Huang B N Wu J L Yeh S J Chen J C Liang Y C Lo I J Chen 《Bioorganic & medicinal chemistry》2001,9(7):1739-1746
A series of vanilloid-type beta-adrenoceptor blockers derived from antioxidant traditional Chinese herbal medicines were synthesized and tested for their antioxidant and adrenoceptor antagonistic activities. They all possessed significant beta-adrenoceptor blocking activities under in vitro experiments and radioligand binding assays. In addition, some compounds were further examined in in vivo tests and produced antagonist effects matching that of propranolol and labetalol by measurements of antagonism toward (-)isoproterenol-induced tachycardia and (-)phenylephrine-induced pressor responses in anesthetized rats. Furthermore, all of the compounds had antioxidant effects inherited from their original structures. In conclusion, compound 11 had the most potent beta-adrenoceptors blocking activity, 12 and 13 possessed high cardioselectivity, whereas 14, 15 and 16 possessed additional alpha-adrenoceptor blocking activity and 15 is the most effective antioxidant of all. The antioxidant activity may be due to their alpha and beta unsaturated side chain at position 1 and ortho-substituted methoxy moiety on 4-phenoxyethylamine. 相似文献
110.
The F-box protein SKP2 binds to the phosphorylated threonine 380 in cyclin E and regulates ubiquitin-dependent degradation of cyclin E 总被引:7,自引:0,他引:7
Yeh KH Kondo T Zheng J Tsvetkov LM Blair J Zhang H 《Biochemical and biophysical research communications》2001,281(4):884-890
Cyclin E is required for S phase entry. The subsequent ubiquitin-dependent degradation of cyclin E contributes to an orderly progression of the S phase. It has been shown that phosphorylation of threonine 380 (Thr380) in cyclin E provides a signal for its ubiquitin-dependent proteolysis. We report that SKP2, an F-box protein and a substrate-targeting component of the SCF(SKP2) ubiquitin E3 ligase complex, mediates cyclin E degradation. In vitro, SKP2 specifically interacted with the cyclin E peptide containing the phosphorylated-Thr380 but not with a cognate nonphosphorylated peptide. In vivo, expression of SKP2 induced cyclin E polyubiquitination and degradation. Conversion of Thr380 into nonphosphorylatable amino acids caused significant resistance of cyclin E to SKP2. The presence of the CDK inhibitor p27(Kip1) also prevented the SKP2-dependent degradation of cyclin E. Our findings suggest that SKP2 regulates cyclin E stability, thus contributing to the control of S phase progression. 相似文献