全文获取类型
收费全文 | 2797篇 |
免费 | 223篇 |
国内免费 | 1篇 |
专业分类
3021篇 |
出版年
2022年 | 38篇 |
2021年 | 60篇 |
2020年 | 50篇 |
2019年 | 47篇 |
2018年 | 77篇 |
2017年 | 68篇 |
2016年 | 83篇 |
2015年 | 111篇 |
2014年 | 141篇 |
2013年 | 188篇 |
2012年 | 214篇 |
2011年 | 223篇 |
2010年 | 133篇 |
2009年 | 107篇 |
2008年 | 119篇 |
2007年 | 133篇 |
2006年 | 136篇 |
2005年 | 115篇 |
2004年 | 108篇 |
2003年 | 68篇 |
2002年 | 70篇 |
2001年 | 59篇 |
2000年 | 44篇 |
1999年 | 40篇 |
1998年 | 22篇 |
1997年 | 31篇 |
1996年 | 24篇 |
1995年 | 28篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 26篇 |
1989年 | 23篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 25篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 22篇 |
1974年 | 13篇 |
1973年 | 14篇 |
1972年 | 12篇 |
1967年 | 10篇 |
排序方式: 共有3021条查询结果,搜索用时 31 毫秒
41.
The activation of the carotene biosynthetic pathway in Blakeslea trispora was found to occur by trisporic acid and many other compounds such as abscisic acid, β-ionone, α-ionone and vitamin A which share significant structural similarity with trisporic acid. The magnitude of stimulatory activities of these effectors was in the order trisporic acid > abscisic acid > β-ionone > α-ionone > vitamin A. Comparison of structures and stimulatory activities of all the effectors indicated that the short length of the side chain and the presence of a keto group in the ring structure of the trisporic acid molecule contributed significantly to the biological activity towards carotenogenesis. 相似文献
42.
Madhavi Ratnam Prakash Najma Zaheer Baquer 《Biochemical and biophysical research communications》1980,94(3):849-854
The effect of intraperitoneal injection of imipramine hydrochloride on the activity of gamma-aminobutyric acid transaminase was determined in three regions of the rat brain.The cerebral hemispheres did not show a significant change in the activity of gamma-aminobutyric acid transaminase. Cerebellum and brain stem, both, however, showed a very significant decrease in the activity of the enzyme at 15 and 30 minutes after drug administration. At 90 minutes after drug administration, the activity of gamma-aminobutyric acid transaminase had returned to nearly control values. 相似文献
43.
44.
The present study was carried out to determine the detailed histological and cytological features of the excurrent ducts of
the male reproductive system in the rhesus monkey. The excurrent ducts show a regional difference in their histological features.
The use of some of these features as histological markers and their possible functional significance are discussed.
The epithelial cells in the different components of the excurrent duct system possess cytological features which suggest their
involvement in absorption and the secretion of different products into the lumen. 相似文献
45.
Acharya Balkrishna Sudeep Verma Vallabh Prakash Mulay Ashish Kumar Gupta Swati Haldar Anurag Varshney 《PLoS neglected tropical diseases》2022,16(6)
Chronic topical cases of Sporotrichosis, a chronic fungal infection caused by the ubiquitously present cryptic members of the Sporothrix species complex, are treated with oral administrations of itraconazole. However, severe pulmonary or disseminated cases require repeated intra-venous doses of amphotericin B or even surgical debridement of the infected tissue. The unavoidable adverse side-effects of the current treatments, besides the growing drug resistance among Sporothrix genus, demands exploration of alternative therapeutic options. Medicinal herbs, due to their multi-targeting capacity, are gaining popularity amidst the rising antimicrobial recalcitrance. Withania somnifera is a well-known medicinal herb with reported antifungal activities against several pathogenic fungal genera. In this study, the antifungal effect of the whole plant extract of W. somnifera (WSWE) has been explored for the first time, against an itraconazole resistant strain of S. globosa. WSWE treatment inhibited S. globosa yeast form growth in a dose-dependent manner, with IC50 of 1.40 mg/ml. Minimum fungicidal concentration (MFC) was found to be 50 mg/ml. Sorbitol protection and ergosterol binding assays, revealed that anti-sporotrichotic effects of WSWE correlated well with the destabilization of the fungal cell wall and cell membrane. This observation was validated through dose-dependent decrease in overall ergosterol contents in WSWE-treated S. globosa cells. Compositional analysis of WSWE through high performance liquid chromatography (HPLC) exhibited the presence of several anti-microbial phytochemicals like withanone, withaferin A, withanolides A and B, and withanoside IV and V. Withanone and withaferin A, purified from WSWE, were 10–20 folds more potent against S. globosa than WSWE, thus, suggesting to be the major phytocompounds responsible for the observed anti-sporotrichotic activity. In conclusion, this study has demonstrated the anti-sporotrichotic property of the whole plant extract of W. somnifera against S. globosa that could be further explored for the development of a natural antifungal agent against chronic Sporotrichosis. 相似文献
46.
47.
With the aim to explore the possible role of phosphate-solubilizing bacteria (PSB) in phosphorus (P) cycling in agricultural soils, we isolated PSB inhabiting naturally in the sandy loam soils under chickpea cropping of Patiala (Punjab State). A total of 31 bacterial isolates showing solubilizing activities were isolated on Pikovskaya agar plates. The potent phosphate solubilizers were selected for further characterization. These isolates were shown to belong to the genera Pseudomonas and Serratia by partial sequencing analysis of their respective 16S rDNA genes. ERIC-PCR based fingerprinting was done for tracking the survival of introduced populations of the PSB during mass inoculation of these strains under chickpea plots. The results showed positive correlation (r2 = 0.853) among soil phosphatase activity and phosphate solubilizers population, which was also positively correlated (r2 = 0.730) to available phosphorus. Identification and characterization of soil PSB for the effective plant growth-promotion broadens the spectrum of phosphate solubilizers available for field application. 相似文献
48.
Kapoor V Paliwal D Baskar Singh S Mohanti BK Das SN 《Biochemical and biophysical research communications》2012,422(4):764-769
Autophagy is a physiologically regulated and evolutionary conserved process that plays a critical role in degradation of cytoplasmic proteins and other macromolecules within the lysosomes. Beclin-1, the mammalian orthologue of yeast Atg6, is an important mediator of autophagy that has been studied in many human cancers. However, the expression of Beclin-1 has not yet been investigated in oral cancer. We for the first time investigated the expression of Beclin-1 in serum and tissues and correlated it with the clinic-pathological features of oral cancer patients. m-RNA expression of Beclin-1 was evaluated in tumor and normal areas of surgical specimens from 10 oral cancer patients by real-time PCR. Approximately, 8-fold lower expression (p<0.001) of Beclin-1 mRNA was observed in tumor tissue as compared to the normal tissue. Serum levels of Beclin-1 were evaluated by SPR and ELISA. No significant difference was observed in serum Beclin-1 levels in patients as compared to healthy subjects, similarly no correlation was found between serum levels and clinic-pathological parameters such as stage, lymph node involvement and tumor size. Our results demonstrate that down-regulation of Beclin-1 may play an important role in the development and progression of oral cancer possibly by dysregulation of autophagy in tumor cells. 相似文献
49.
GMF-Knockout Mice are Unable to Induce Brain-Derived Neurotrophic Factor after Exercise 总被引:2,自引:0,他引:2
We earlier reported that overexpression of glia maturation factor (GMF) in cultured astrocytes enhances the production of brain-derived neurotrophic factor (BDNF). The current study was conducted to find out whether BDNF production is impaired in animals devoid of GMF. To this end GMF-knockout (KO) mice were subjected to exercise and the neurotrophin mRNAs were determined by real-time RT-PCR. Compared to wild-type (WT) mice, there is a decrease in exercise-induced BDNF in the KO mice. The observation was correlated with the finding that, in WT mice, exercise increases GMF expression. The results are consistent with the hypothesis that GMF is necessary for exercise-induction of BDNF, and that GMF may promote neuroprotection through BDNF production. 相似文献
50.