全文获取类型
收费全文 | 13175篇 |
免费 | 1491篇 |
国内免费 | 1103篇 |
出版年
2024年 | 21篇 |
2023年 | 128篇 |
2022年 | 331篇 |
2021年 | 554篇 |
2020年 | 492篇 |
2019年 | 543篇 |
2018年 | 576篇 |
2017年 | 439篇 |
2016年 | 552篇 |
2015年 | 819篇 |
2014年 | 924篇 |
2013年 | 952篇 |
2012年 | 1119篇 |
2011年 | 1006篇 |
2010年 | 675篇 |
2009年 | 568篇 |
2008年 | 674篇 |
2007年 | 590篇 |
2006年 | 573篇 |
2005年 | 476篇 |
2004年 | 479篇 |
2003年 | 478篇 |
2002年 | 437篇 |
2001年 | 331篇 |
2000年 | 250篇 |
1999年 | 241篇 |
1998年 | 137篇 |
1997年 | 124篇 |
1996年 | 120篇 |
1995年 | 101篇 |
1994年 | 90篇 |
1993年 | 66篇 |
1992年 | 97篇 |
1991年 | 91篇 |
1990年 | 76篇 |
1989年 | 79篇 |
1988年 | 57篇 |
1987年 | 55篇 |
1986年 | 46篇 |
1985年 | 26篇 |
1984年 | 42篇 |
1983年 | 46篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The characteristics of the inducible galactose transport system in bakers' yeast were studied in uridine diphosphate, galactose-1-phosphate uridylyl-transferaseless cells. Transferaseless cells transport galactose at the same initial rate as wild-type cells and accumulate a mixture of free galactose and galactose-1-phosphate. The addition of 14C-labeled galactose to cells preloaded with unlabeled galactose and galactose-1-phosphate results in a higher rate of labeling of the free-sugar pool than of the galactose-1-phosphate pool. These results support other evidence that galactose uptake in bakers' yeast is a carrier-mediated, facilitated diffusion and that phosphorylation is an intracellular event after uptake of the free sugar. 相似文献
3.
4.
5.
6.
The accumulation of gentamicin by rat renal cortex and was not inhibited by probenecid, tetraethylammonium, cephalosporins nor α-aminoisobutyric acid, but was significantly blocked by other aminoglycosides (neomycin, tobramycin and kanamycin). The data suggest that specific binding sites for aminoglycosides are present on the surface or in cells of the renal proximal tubule. 相似文献
7.
Zhaohua Zhang LiLi Ge Shanshan Zhang Jue Wang Wen Jiang Qian Xin Yun Luan 《Journal of cellular and molecular medicine》2020,24(23):13938
The aim of the study was to explore the mechanism of mesenchymal stem cell‐derived exosomes (MSC‐EXO) to protect against experimentally induced pulmonary hypertension (PH). Monocrotaline (MCT)‐induced rat model of PH was successfully established by a single intraperitoneal injection of 50 mg/kg MCT, 3 weeks later the animals were treated with MSC‐EXO via tail vein injection. Post‐operation, our results showed that MSC‐EXO could significantly reduce right ventricular systolic pressure (RVSP) and the right ventricular hypertrophy index, attenuate pulmonary vascular remodelling and lung fibrosis in vivo. In vitro experiment, the hypoxia models of pulmonary artery endothelial cell (PAEC) and pulmonary vascular smooth muscle cell (PASMC) were used. We found that the expression levels of Wnt5a, Wnt11, BMPR2, BMP4 and BMP9 were increased, but β‐catenin, cyclin D1 and TGF‐β1 were decreased in MSC‐EXO group as compared with MCT or hypoxia group in vivo or vitro. However, these increased could be blocked when cells were transfected with Wnt5a siRNA in vitro. Taken together, these results suggested that the mechanism of MSC‐EXO to prevent PH vascular remodelling may be via regulation of Wnt5a/BMP signalling pathway. 相似文献
8.
J.C. Kuo Edward S. Yeung 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,229(2)
A separation and detection scheme is presented for the determination of free, esterified and total cholesterol in human serum. Separation is accomplished by reversed-phase high-performance liquid chromatography and the eluate is monitored by the laser-based optical activity detector. The method is simple, accurate and has the advantage of specificity and selectivity when compared with the many methods commonly used. 相似文献
9.
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
10.
D A Hartman S R Kuo T R Broker L T Chow R D Wells 《The Journal of biological chemistry》1992,267(8):5488-5494
A conformational distortion in the DNA duplex at the regulatory region of human papillomavirus type-11 next to an intermolecular triplex, formed with a synthetic oligonucleotide, was investigated with several chemical probes. The sequence targeted for triplex formation borders on the binding sites for the regulatory proteins encoded by the viral E2 open reading frame. Dimethyl sulfate, diethyl pyrocarbonate, and OsO4 all react to a greater extent with nucleotides in the duplex that are immediately adjacent to the triplex as compared to other bases throughout the duplex. This hypermodification was observed on both the polypurine and polypyrimidine strands of the duplex DNA. Similar hyperreactivity of bases flanking a triplex also was seen when the contiguous target polypurine tract was effectively extended by mutating interrupting pyrimidines in the human papillomavirus type-11 sequence to purines. We propose that this hyperreactivity is due to a structural distortion caused by the junction between the triplex and the duplex tracts. 相似文献