全文获取类型
收费全文 | 1634篇 |
免费 | 136篇 |
国内免费 | 187篇 |
专业分类
1957篇 |
出版年
2024年 | 12篇 |
2023年 | 49篇 |
2022年 | 90篇 |
2021年 | 145篇 |
2020年 | 78篇 |
2019年 | 112篇 |
2018年 | 99篇 |
2017年 | 74篇 |
2016年 | 81篇 |
2015年 | 133篇 |
2014年 | 130篇 |
2013年 | 143篇 |
2012年 | 140篇 |
2011年 | 109篇 |
2010年 | 41篇 |
2009年 | 48篇 |
2008年 | 54篇 |
2007年 | 50篇 |
2006年 | 47篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 31篇 |
2002年 | 28篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 12篇 |
1997年 | 17篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有1957条查询结果,搜索用时 0 毫秒
51.
52.
53.
Jiao Yan Zhao Dandan Gao Fuhua Hu Xiaoyan Hu Xinxin Li Mei Cui Ying Wei Xiaoqing Xie Ce Zhao Ying Gao Ying 《Journal of physiology and biochemistry》2021,77(1):47-61
Journal of Physiology and Biochemistry - Endothelial injury, which can cause endothelial inflammation and dysfunction, is an important mechanism for the development of atherosclerotic plaque. This... 相似文献
54.
Zilan Lv Dandan Yang Jie Li Min Hu Min Luo Xiaoqin Zhan Peipei Song Chen Liu Huili Bai Baolin Li Yang Yang Yingying Chen Qiong Shi Yaguang Weng 《Molecules and cells》2013,36(2):119-126
Transforming growth factor-β (TGF-β) is known to promote tumor migration and invasion. Bone morphogenetic proteins (BMPs) are members of the TGF-β family expressed in a variety of human carcinoma cell lines. The role of bone morphogenetic protein 9 (BMP9), the most powerful osteogenic factor, in osteosarcoma (OS) progression has not been fully clarified. The expression of BMP9 and its receptors in OS cell lines was analyzed by RT-PCR. We found that BMP9 and its receptors were expressed in OS cell lines. We further investigated the influence of BMP9 on the biological behaviors of OS cells. BMP9 overexpression in the OS cell lines 143B and MG63 inhibited in vitro cell migration and invasion. We further investigated the expression of a panel of cancer-related genes and found that BMP9 overexpression increased the phosphorylation of Smad1/5/8 proteins, increased the expression of ID1, and reduced the expression and activity of matrix metalloproteinase 9 (MMP9) in OS cells. BMP9 silencing induced the opposite effects. We also found that BMP9 may not affect the chemokine (C-X-C motif) ligand 12 (CXCL12)/C-X-C chemokine receptor type 4 (CXCR4) axis to regulate the invasiveness and metastatic capacity of OS cells. Interestingly, CXCR4 was expressed in both 143B and MG63 cells, while CXCL12 was only detected in MG63 cells. Taken together, we hypothesize that BMP9 inhibits the migration and invasiveness of OS cells through a Smad-dependent pathway by downregulating the expression and activity of MMP9. 相似文献
55.
Granulation of activated sludge in a continuous flow airlift reactor by strong drag force 总被引:1,自引:0,他引:1
Dandan Zhou Mengyuan Liu Jun Wang Shuangshi Dong Ning Cui Linlin Gao 《Biotechnology and Bioprocess Engineering》2013,18(2):289-299
Most aerobic granule cultivation has been based on the sequencing batch reactor (SBR) and then the factors that affect aerobic granulations were developed in the SBR. However, little work has been done to cultivate aerobic granules in a continuous-flow bioreactor with simple structure that is realistic for engineering. This work is the first to cultivate aerobic granules in a continuous flow airlift fluidized bed reactor (CAFB) possesses a very simple structure and without settling time and starvation time controlling. The configuration of CAFB was the simplest continuous-flow aerobic granular bioreactor reported by now. The majority of granules could be formatted in the CAFB after 12 days cultivation. The effluent COD concentration maintained at 50 ± 10 mg/L for the variable COD loading rate of 3.5 g COD/L/d and 4.8 g COD/L/d, which confirmed that the CAFB performed good anti-shock abilities. CAFB performed good nitrification ability, however, little denitrification was found under the operating conditions of this study. The shear stress acting on the solid phase were hundreds of times stronger in the CAFB than in the SBR at the same aeration strength. It seems CAFB is very efficient for granulation due to the strong shear-force exertion, which is promising for continuous-flow aerobic granular bioreactor. Protein, positive to the hydrophobicity, was predominant in extracellular polymeric substances in the granules, and favored the granules formation in the CAFB combined with the polysaccharides. However, filamentous bulking always happened in 35 days operation of the CAFB, thus further study on the stability of this bioreactor is urgently necessary. 相似文献
56.
Cell-based high throughput proliferation and cytotoxicity assays are increasingly used in drug screening and bioprocess development. However, online monitoring of cell proliferation, pH, and dissolved oxygen (DO) has been a challenge in 3D cell-based assays. In this work, a 40-microwell bioreactor (40-MBR) system was developed from a 384-well plate for real-time, noninvasive monitoring of pH, DO, and cell proliferation in 3D microenvironments. Chinese hamster ovary (CHO) and MCF-07 breast cancer cells cultured in 40-MBR confirmed that the 40-MBR was capable of simultaneously monitoring DO and cell proliferation based on culture fluorescence and pH by measuring the absorbance of phenol red. Cytotoxicity studies of sodium butyrate on CHO cells demonstrated that 40-MBR with dynamic background fluorescence correction gave more reliable and highly reproducible growth kinetic data compared to conventional multiwells with static background correction. Furthermore, the dosage effects of two new anticancer drug candidates, 5,7-dihydroxy-2-(4-hydroxyphenyl)-8-[(E)-2-phenylethenyl]-3,4-dihydro-2H-1-benzopyran-4-one (DH-8P-DB) and 5,7-dihydroxy-2-(4-hydroxyphenyl)-6-[(E)-2-phenylethenyl]-3,4-dihydro-2H-1-benzopyran-4-one (DH-6P-DB), on HT-29 colon cancer cells were assessed using the 40-MBR, and the results indicated that DH-6P-DB would be a more potent drug in treating colon cancer than DH-8P-DB. These studies demonstrated that 40-MBR could serve as a high throughput platform for screening potential cancer drugs in early-stage drug discovery. 相似文献
57.
A simple, reliable, high-throughput screening method was developed and used to assess the pharmaceutical effects of extracts of traditional Chinese herbal medicines (TCHMs). This method is based on 3-dimensional (3-D) cultures of mouse embryonic stem (mES) and human colon cancer and breast cancer cells expressing enhanced green fluorescent protein (EGFP) in polyethylene terephthalate (PET) fibrous scaffolds on modified 384-well plates with online monitoring of culture fluorescence for dynamic responses of cells to drugs present in culture media. Cell responses to deoxycholic acid and the extracts of 3 TCHMs (Ganoderma lucidum spores, Ginkgo biloba, and Epimedium brevicornum) at various concentrations were investigated for their effects on proliferation and cytotoxicity. The screening results, i.e., the growth responses of cancer cells to those drugs, were consistent with what have been reported in the literature, confirming the reliability of the new screening approach. Different from previous screening methods for both TCHMs and western medicines that used animal models or 2-D cell-based assays with single cell lines, this 3-D cell-based screening method employs both cancer and normal cells and thereby provides a way for quick, direct evaluation of the anticancer effects of TCHMs. This method also offers assessment on the side effects of TCHMs. 相似文献
58.
Effect of the primary host for production of both sexes on the mating interaction in an autoparasitoid species 总被引:2,自引:0,他引:2
Encarsia sophia (Girault and Dodd) is an autoparasitoid in the hymenopteran family Aphelinidae. The females develop as primary parasitoids on whitefly nymphs (primary hosts), whereas the males develop as hyperparasitoids on their own species or on other primary parasitoid species (secondary hosts). The autoparasitoids not only parasitise whiteflies but also kill them with strong host-feeding capacity. In this study, female and male E. sophia were reared on the primary hosts Trialeurodes vaporariorum and Bemisia tabaci ‘Q’, and the host-feeding and parasitism of wasps on both whitefly species were determined for the four possible different mating combinations: (i) E. sophia females reared on B. tabaci (ESF-BT) mated with E. sophia males from B. tabaci (ESM-BT), (ii) E. sophia females reared on T. vaporariorum (ESF-TV) mated with E. sophia males from T. vaporariorum (ESM-TV), (iii) ESF-BT mated with ESM-TV, and (iv) ESF-TV mated with ESM-BT. ESF-TV mated with ESM-TV killed the largest percentage of whitefly nymphs through host feeding. The ESF-TV with larger body size mating with larger ESM-TV killed more whitefly nymphs through host feeding than those mating with smaller ESM-BT. Whether B. tabaci or T. vaporariorum were used as hosts, ESF-TV mated with ESM-TV and ESM-BT and ESF-BT mated with ESM-BT significantly parasitised more whitefly nymphs than ESF-BT mated with ESM-TV. In general, ESF-BT mated with ESM-TV killed significantly fewer whitefly nymphs through parasitism and host feeding than the other three mating combinations on both whitefly species. These results indicated that the performance of autoparasitoids on insect pests was not only dependent on females but was also affected by mating with males from different primary host species. 相似文献
59.
60.
Dandan Chen Fengxia Ma Shuxia Xu Shaoguang Yang Fang Chen Lijuan Rong Ying Chi Qinjun Zhao Shihong Lu Zhibo Han Aiming Pang Zhongchao Han 《Cytotherapy》2013,15(4):423-433
Background aimsToll-like receptors (TLRs) play an important role in innate and adaptive immunity by recognizing pathogen-associated molecular patterns (PAMPs).MethodsIn the present study, we investigated the expression and role of TLRs on human umbilical cord mesenchymal stromal cells (UC-MSCs). The proliferation, differentiation and immunoregulatory activity of UC-MSCs primed with or without TLR ligands were determined.ResultsAt the RNA level, the expression of TLR2, 4, 6 and 9 was relatively higher than that of other TLRs. However, TLR3 and TLR4 expression were relatively higher at the protein level. UC-MSCs expressed functional TLRs by nuclear factor-κB activation and cytokine expression assay. Poly-inosinic acid:cytidylic acid [Poly(I:C)] stimulation inhibited the proliferation of UC-MSCs, but the ligand of other TLRs had no significant effect. Poly(I:C) stimulation enhanced the adipogenic differentiation capability of UC-MSCs, but lipopolysaccharide inhibited the adipogenic differentiation. Poly(I:C) and CpG-oligonucleotide promoted the immunosuppressive potentiality of UC-MSCs, accompanied with the phosphorylation of interferon regulatory factor 3 (IRF3) and increased expression of indoleamine 2,3-dioxygenase and interferon β, whereas activation of other TLR ligands (synthetic analog fibroblast-stimulating lipopeptide-1 and lipopolysaccharide) failed to affect the immunoregulatory activity of UC-MSCs.ConclusionsTaken together, our data demonstrated that TLR activation influenced the function of UC-MSCs, which might have important implications in future efforts to explore the clinical potentials of UC-MSCs. 相似文献