全文获取类型
收费全文 | 4728篇 |
免费 | 266篇 |
国内免费 | 3篇 |
专业分类
4997篇 |
出版年
2023年 | 40篇 |
2022年 | 69篇 |
2021年 | 132篇 |
2020年 | 79篇 |
2019年 | 95篇 |
2018年 | 128篇 |
2017年 | 117篇 |
2016年 | 147篇 |
2015年 | 233篇 |
2014年 | 207篇 |
2013年 | 344篇 |
2012年 | 369篇 |
2011年 | 340篇 |
2010年 | 238篇 |
2009年 | 190篇 |
2008年 | 268篇 |
2007年 | 258篇 |
2006年 | 234篇 |
2005年 | 223篇 |
2004年 | 160篇 |
2003年 | 148篇 |
2002年 | 150篇 |
2001年 | 65篇 |
2000年 | 50篇 |
1999年 | 47篇 |
1998年 | 45篇 |
1997年 | 31篇 |
1996年 | 20篇 |
1995年 | 29篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 26篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1979年 | 18篇 |
1977年 | 20篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1974年 | 13篇 |
1972年 | 14篇 |
1971年 | 12篇 |
排序方式: 共有4997条查询结果,搜索用时 15 毫秒
141.
The paper records the presence of sixteen species of aquatic oligochaetes, belonging to the Aeolosomatidae (1 species). Naididae (13 species) and Tubificidae (2 species), living in association with the floating roots of the water hyacinth, Eichhornia crassipes Solms., from a tank in Vizianagaram town in Andhra Pradesh, India. Of these, Aeolosoma hyalinum Bunke, 1967 and Dero obtusa D'Udekem, 1855 are new records for the Indian sub-continent. 相似文献
142.
143.
144.
Choudhary Renuka Sharma Anil Kumar Sudarshan Upadhyay Ramesh Chandra Singh Sohan Vir Mohanty Ashok 《Molecular and cellular biochemistry》2020,465(1-2):141-153
Molecular and Cellular Biochemistry - Ultraviolet radiations (UVR) are responsible for a wide variety of acute and chronic effects on the animal skin. However, the effect of UVR-induced oxidative... 相似文献
145.
Nanobiotechnology provides novel set of tools to manipulate and enhance crop production using nanoparticles, nanofibres, nanoemulsions, and nanocapsules. Nanomaterials provide a platform to deliver agrochemicals and various macromolecules needed for plant growth enhancement and resistance to stresses. Smart delivery of agrochemicals increases the yield by optimizing water and nutrient conditions. Another added advantage is controlled release and site-directed delivery of agrochemicals. Further enhancement in quality and quantity in agriculture can be achieved by nanoparticle-mediated gene transformation and delivery of macromolecules that induces gene expression in plants. Various types of nanomaterials have been tested so far and the results have been promising in terms of productivity and quality enhancement. 相似文献
146.
S. Raj V. Vinod J. Jayakumar P. Suresh A. Kumar R. Biswas 《Letters in applied microbiology》2021,73(1):31-38
Candida species are opportunistic human fungal pathogens that cause acute and chronic infections against which only few antifungal agents are available. Here we have elucidated the antifungal effect of Syzygium samarangense leaf extracts (SSLE). Antifungal activity of SSLE was studied against Candida albicans, C. krusei, C. parapsilosis, C. glabrata, C. auris and C. tropicalis. Following experiments were performed: minimum fungicidal concentration (MFC) determination, agar well disc diffusion assays, fungal morphology analysis using scanning electron microscope (SEM), ex vivo fungal survival assays on porcine tongue and skin and in vivo fungal survival assays using Drosophila melanogaster fly model. Results demonstrated MFC of SSLE ranges between 100 and 125 mg ml−1. SEM images showed cell wall degradation of C. albicans when treated with SSLE. Around 75% decrease in C. albicans viability was observed when infected porcine tongue and skin were treated using SSLE. The C. albicans infected D. melanogaster when fed with SSLE showed significant decrease (around 80%) of fungal count than the infected control. Furthermore, agar plate disc diffusion assays demonstrated that the antifungal activity of SSLE could be due to chalcone, which is one of the active constituents in SSLE. Our study demonstrated that SSLE could be used for the topical treatment of Candida infections. 相似文献
147.
Association of active caspase 8 with the mitochondrial membrane during apoptosis: potential roles in cleaving BAP31 and caspase 3 and mediating mitochondrion-endoplasmic reticulum cross talk in etoposide-induced cell death 下载免费PDF全文
Chandra D Choy G Deng X Bhatia B Daniel P Tang DG 《Molecular and cellular biology》2004,24(15):6592-6607
It was recently demonstrated that during apoptosis, active caspase 9 and caspase 3 rapidly accumulate in the mitochondrion-enriched membrane fraction (D. Chandra and D. G. Tang, J. Biol. Chem.278:17408-17420, 2003). We now show that active caspase 8 also becomes associated with the membranes in apoptosis caused by multiple stimuli. In MDA-MB231 breast cancer cells treated with etoposide (VP16), active caspase 8 is detected only in the membrane fraction, which contains both mitochondria and endoplasmic reticulum (ER), as revealed by fractionation studies. Immunofluorescence microscopy, however, shows that procaspase 8 and active caspase 8 predominantly colocalize with the mitochondria. Biochemical analysis demonstrates that both procaspase 8 and active caspase 8 are localized mainly on the outer mitochondrial membrane (OMM) as integral proteins. Functional analyses with dominant-negative mutants, small interfering RNAs, peptide inhibitors, and Fas-associated death domain (FADD)- and caspase 8-deficient Jurkat T cells establish that the mitochondrion-localized active caspase 8 results mainly from the FADD-dependent and tumor necrosis factor receptor-associated death domain-dependent mechanisms and that caspase 8 activation plays a causal role in VP16-induced caspase 3 activation and cell death. Finally, we present evidence that the OMM-localized active caspase 8 can activate cytosolic caspase 3 and ER-localized BAP31. Cleavage of BAP31 leads to the generation of ER- localized, proapoptotic BAP20, which may mediate mitochondrion-ER cross talk through a Ca(2+)-dependent mechanism. 相似文献
148.
PknH, a transmembrane Hank's type serine/threonine kinase from Mycobacterium tuberculosis is differentially expressed under stress conditions 总被引:1,自引:0,他引:1
Sharma K Chandra H Gupta PK Pathak M Narayan A Meena LS D'Souza RC Chopra P Ramachandran S Singh Y 《FEMS microbiology letters》2004,238(1):107-113
149.
A wheat basic protein (WBP) was purified to homogeneity from wheat germ by a protocol involving extraction, centrifugation, batchwise elution from carboxymethylcellulose (CM-52), acidification with trifluoroacetic acid, neutralization and HPLC on a SP5PW cation exchange column. WBP is a 10 kDa protein and is phosphorylated on serine residues by wheat germ Ca(2+)-dependent protein kinase (CDPK). [32P]phosphoWBP exactly comigrates with WBP on SDS-PAGE. WBP does not inhibit either wheat germ CDPK or calmodulin-dependent myosin light chain kinase. Apart from histone H1, WBP is the best endogenous substrate yet found for wheat embryo CDPK. A 12 kDa pine basic protein (PBP) was purified to homogeneity from seeds of stone pine (Pinus pinea L.) by a simple procedure involving batchwise elution from carboxymethylcellulose and cation exchange HPLC. PBP is also a good substrate for CDPK and is phosphorylated on Ser residues. N-terminal sequencing of WBP and PBP revealed that these proteins are homologous to a family of small basic plant proteins having a phospholipid transfer function. 相似文献
150.
A fundamental difference between normal cells and tumor cells is the proliferative activity of the nucleus and nucleolus, which increases progressively from normal to oral dysplastic mucosa to oral squamous cell carcinoma (OSCC). This activity is evaluated routinely using hematoxylin and eosin (H & E) staining, but in some cases, inter-observer variability occurs among pathologists. We evaluated cellular proliferation by staining sections with the methyl green-pyronin Y procedure and the Feulgen reaction. We also compared the efficacy of methyl green-pyronin Y and Feulgen staining for studying nuclear and nucleolar features in oral dysplastic mucosa and in different grades of OSCC. Sections cut from formalin fixed, paraffin embedded blocks of five normal mucosa, 15 dysplastic mucosa, 10 well-differentiated OSCC, 10 moderately differentiated OSCC and five poorly differentiated OSCC cases were stained with Hematoxylin and Eosin, methyl green-pyronin Y and the Feulgen reaction. The mean diameters of the nuclei and number of nucleoli showed significant differences. A progressive increase in diameter of the nucleus and number of nucleoli was observed from normal mucosa through poorly differentiated OSCC. We observed that methyl green-pyronin Y stain is more useful than Feulgen and hematoxylin and eosin for simultaneous quantitative assessment of both RNA and DNA. The simplicity of this technique makes it a valuable tool even for daily routine examination. 相似文献