全文获取类型
收费全文 | 9306篇 |
免费 | 732篇 |
国内免费 | 437篇 |
出版年
2023年 | 67篇 |
2022年 | 177篇 |
2021年 | 391篇 |
2020年 | 275篇 |
2019年 | 283篇 |
2018年 | 318篇 |
2017年 | 259篇 |
2016年 | 376篇 |
2015年 | 567篇 |
2014年 | 622篇 |
2013年 | 715篇 |
2012年 | 808篇 |
2011年 | 738篇 |
2010年 | 468篇 |
2009年 | 340篇 |
2008年 | 480篇 |
2007年 | 399篇 |
2006年 | 385篇 |
2005年 | 315篇 |
2004年 | 273篇 |
2003年 | 232篇 |
2002年 | 227篇 |
2001年 | 170篇 |
2000年 | 190篇 |
1999年 | 139篇 |
1998年 | 85篇 |
1997年 | 82篇 |
1996年 | 82篇 |
1995年 | 59篇 |
1994年 | 63篇 |
1993年 | 48篇 |
1992年 | 91篇 |
1991年 | 76篇 |
1990年 | 77篇 |
1989年 | 61篇 |
1988年 | 47篇 |
1987年 | 67篇 |
1986年 | 45篇 |
1985年 | 37篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1980年 | 22篇 |
1979年 | 26篇 |
1978年 | 19篇 |
1977年 | 21篇 |
1975年 | 18篇 |
1973年 | 21篇 |
1972年 | 17篇 |
1968年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Microscopic structure and properties changes of cassava stillage residue pretreated by mechanical activation 总被引:1,自引:0,他引:1
This study has focused on the pretreatment of cassava stillage residue (CSR) by mechanical activation (MA) using a self-designed stirring ball mill. The changes in surface morphology, functional groups and crystalline structure of pretreated CSR were examined by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) under reasonable conditions. The results showed that MA could significantly damage the crystal structure of CSR, resulting in the variation of surface morphology, the increase of amorphous region ratio and hydrogen bond energy, and the decrease in crystallinity and crystalline size. But no new functional groups generated during milling, and the crystal type of cellulose in CSR still belonged to cellulose I after MA. 相似文献
942.
943.
Macronutrients, such as protein or amino acid, not only supply calories but some components may also play as signaling molecules
to affect feeding behavior, energy balance, and fuel efficiency. Leucine, a branched-chain amino acid is a good example. After
structural roles are satisfied, the ability of leucine to function as signal and oxidative substrate is based on a sufficient
intracellular concentration. Therefore, leucine level must be sufficiently high to play the signaling and metabolic roles.
Leucine is not only a substrate for protein synthesis of skeletal muscle, but also plays more roles beyond that. Leucine activates
signaling factor of mammalian target of rapamycin (mTOR) to promote protein synthesis in skeletal muscle and in adipose tissue.
It is also a major regulator of the mTOR sensitive response of food intake to high protein diet. Meanwhile, leucine regulates
blood glucose level by promoting gluconeogenesis and aids in the retention of lean mass in a hypocaloric state. It is beneficial
to animal nutrition and clinical application and extrapolation to humans. 相似文献
944.
Pantothenate synthetase (PS) catalyzes the final step of the pantothenate pathway, in which pantothenate is formed from pantoate and β-alanine in an ATP-dependent reaction. Mycobacterium tuberculosis PS (MTB PS) is functionally a dimer and a potential target for novel antitubercular drugs. Molecular dynamics simulations show that the functional dynamics of the enzyme are dominated by motions of a flexible gate loop in the N-terminal domain and of the C-terminal domain. The gate loop motions dominate in MTB PS while the C-terminal domain motion dominates in Escherichia coli PS. Simulations also show that the correlated motions of the domains are severely compromised in the monomeric forms. Mutations that reduce the mobility of the gate loop in MTB PS and increased it in E. coli PS were designed and validated through simulations. 相似文献
945.
946.
Firooznia F Cheung AW Brinkman J Grimsby J Gubler ML Hamid R Marcopulos N Ramsey G Tan J Wen Y Sarabu R 《Bioorganic & medicinal chemistry letters》2011,21(7):1933-1936
The highly potent but modestly selective N-(2-amino-4-methoxy-benzothiazol-7-yl)-N-ethyl-acetamide derivative 2 was selected as the starting point for the design of novel selective A2B antagonists, due to its excellent potency, and good drug-like properties. A series of compounds containing nonaromatic amides or ureas of five- or six-membered rings, and also bearing an m-trifluoromethyl-phenyl group (shown to impart superior potency) was prepared and evaluated for their selectivity against the A2A and A1 receptors. This work resulted in the identification of compound 30, with excellent potency and high selectivity against both A2A and A1 receptors. 相似文献
947.
Jamaluddin MF Bailey UM Tan NY Stark AP Schulz BL 《Protein science : a publication of the Protein Society》2011,20(5):849-855
Asparagine-linked glycosylation is a common and vital co- and post-translocational modification of diverse secretory and membrane proteins in eukaryotes that is catalyzed by the multiprotein complex oligosaccharyltransferase (OTase). Two isoforms of OTase are present in Saccharomyces cerevisiae, defined by the presence of either of the homologous proteins Ost3p or Ost6p, which possess different protein substrate specificities at the level of individual glycosylation sites. Here we present in vitro characterization of the polypeptide binding activity of these two subunits of the yeast enzyme, and show that the peptide-binding grooves in these proteins can transiently bind stretches of polypeptide with amino acid characteristics complementary to the characteristics of the grooves. We show that Ost6p, which has a peptide-binding groove with a strongly hydrophobic base lined by neutral and basic residues, binds peptides enriched in hydrophobic and acidic amino acids. Further, by introducing basic residues in place of the wild type neutral residues lining the peptide-binding groove of Ost3p, we engineer binding of a hydrophobic and acidic peptide. Our data supports a model of Ost3/6p function in which they transiently bind stretches of nascent polypeptide substrate to inhibit protein folding, thereby increasing glycosylation efficiency at nearby asparagine residues. 相似文献
948.
Francesca ParatiRoberto Altieri Alessandro EspositoArianna Lobianco Milva PepiLorenzo Montesi Tan Nair 《International biodeterioration & biodegradation》2011,65(1):160-163
The production of a substrate containing destoned olive mill solid waste for the cultivation of Agaricus bisporus (Lange) Imbach on an industrial scale was studied. A standard mushroom compost (C) mainly made from straw and poultry manure was compared with the experimental compost (EC) containing the same ingredients as (C) but with added olive mill solid waste (10.6% w/w). Microbial indicators such as counts of heterotrophic microbes and actinomycetes were higher in EC than in C. In addition, compost selectivity as indicated by higher mushroom yield and biological efficiency of EC was higher than that of C. Market quality of the mushrooms produced in both C and EC were comparable. These findings support our work that olive mill solid waste can be used safely in thermal composting process to produce a selective substrate for industrial-scale cultivation of A. bisporus. This study also demonstrates an environmentally sustainable system to manage solid waste from olive oil extraction processes thus overcoming environmental pollution brought about by irrational disposal of the waste on farm lands. 相似文献
949.
950.
Chen SB Tan JH Ou TM Huang SL An LK Luo HB Li D Gu LQ Huang ZS 《Bioorganic & medicinal chemistry letters》2011,21(3):1004-1009
Discovery of potent and selective ligands for telomeric G-quadruplex DNA is a challenging work. Through a combination approach of pharmacophore model construction, model validation, database virtual screening, chemical synthesis and interaction evaluation, we discovered and confirmed triaryl-substituted imidazole TSIZ01 to be a new telomeric G-quadruplex ligand with potent binding and stabilizing activity to G-quadruplex DNA, as well as a 8.7-fold selectivity towards telomeric G-quadruplex DNA over duplex DNA. 相似文献