全文获取类型
收费全文 | 2839篇 |
免费 | 322篇 |
国内免费 | 20篇 |
出版年
2023年 | 13篇 |
2021年 | 29篇 |
2020年 | 32篇 |
2019年 | 52篇 |
2018年 | 68篇 |
2017年 | 46篇 |
2016年 | 70篇 |
2015年 | 151篇 |
2014年 | 144篇 |
2013年 | 179篇 |
2012年 | 220篇 |
2011年 | 202篇 |
2010年 | 120篇 |
2009年 | 111篇 |
2008年 | 122篇 |
2007年 | 115篇 |
2006年 | 134篇 |
2005年 | 133篇 |
2004年 | 123篇 |
2003年 | 111篇 |
2002年 | 87篇 |
2001年 | 90篇 |
2000年 | 93篇 |
1999年 | 59篇 |
1998年 | 30篇 |
1997年 | 27篇 |
1996年 | 29篇 |
1994年 | 22篇 |
1993年 | 11篇 |
1992年 | 43篇 |
1991年 | 46篇 |
1990年 | 36篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 33篇 |
1986年 | 27篇 |
1985年 | 17篇 |
1984年 | 27篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 23篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 15篇 |
1972年 | 11篇 |
排序方式: 共有3181条查询结果,搜索用时 15 毫秒
1.
En-Chi Chiu Shu-Chun Lee Chian-Jue Kuo For-Wey Lung I-Ping Hsueh Ching-Lin Hsieh 《PloS one》2015,10(11)
A performance-based measure for assessing executive functions (EF) is useful to understand patients’ real life performance of EF. This study aimed to develop a performance-based measure of executive functions (PEF) based on the Lezak model and to examine psychometric properties (i.e., unidimensionality and reliability) of the PEF using Rasch analysis in patients with schizophrenia. We developed the PEF in three phases: (1) designing the preliminary version of PEF; (2) consultation with experts, cognitive interviews with patients, and pilot tests on patients to revise the preliminary PEF; (3) establishment of the final version of the PEF and examination of unidimensionality and Rasch reliability. Two hundred patients were assessed using the revised PEF. After deleting items which did not satisfy the Rasch model’s expectations, the final version of the PEF contained 1 practice item and 13 test items for assessing the four domains of EF (i.e., volition, planning, purposive action, and effective performance). For unidimensional and multidimensional Rasch analyses, the 4 domains showed good reliability (i.e., 0.77–0.85 and 0.87–0.90, respectively). Our results showed that the PEF had satisfactory unidimensionality and Rasch reliability. Therefore, clinicians and researchers could use the PEF to assess the four domains of EF in patients with schizophrenia. 相似文献
2.
3.
K N Pandey T Inagami P R Girard J F Kuo K S Misono 《Biochemical and biophysical research communications》1987,148(2):589-595
The effects of synthetic atrial natriuretic factor (ANF) on the state of protein phosphorylation in plasma membranes of bovine adrenal cortex have been studied in vitro. ANF (1x10(-8)M - 1x10(-7)M) specifically inhibited the phosphorylation of two distinct proteins of 78 kDa and 240 kDa. Immunoblotting with specific antiserum to protein kinase C produced evidence that 78 kDa protein is most likely the protein kinase C whose phosphorylation is inhibited by both ANF and cGMP. However, cGMP did not affect the phosphorylation of 240 kDa protein, indicating a new cGMP-independent mechanism of ANF action in the adrenal, which is compatible with the lack of action of cGMP and its analogs in ANF-induced inhibition of aldosterone secretion from adrenal cortex. The inhibition of phosphorylation of putative protein kinase C by ANF or cGMP indicates a hitherto unknown signal transduction mechanism of ANF. 相似文献
4.
Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (Mr 45,000, pI 5.15) and protein B (Mr 45,000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but inter-related manner, the effects of polyamines and TPA. 相似文献
5.
Isolation and characterization of proteinase inhibitor I from etiolated tobacco leaves 总被引:5,自引:0,他引:5
Proteinase Inhibitor I was induced to accumulate in tobacco (Nicotiana tabaccum) leaves by placing plants in darkness for 10 days at 27 degrees C. The inhibitor was isolated using ammonium sulfate precipitation, Sephadex G-75 chromatography, heating, and affinity chromatography with a chymotrypsin-Sepharose column. Inhibitor I was purified 232-fold with a yield of 34 mg from 2.5 kg of leaves. Affinity-purified tobacco Inhibitor I was shown to be homogeneous by gel electrophoresis in both nondissociating and dissociating buffers. The inhibitor has a molecular weight of 39,000 +/- 1000 determined by gel filtration and, like its potato and tomato counterparts, is composed of five subunits of molecular weight 8100. The tobacco Inhibitor I strongly inhibits chymotrypsin and weakly inhibits trypsin. The chemical, physical, and immunological properties of tobacco Inhibitor I indicate that it is structurally very similar to potato tuber Inhibitor I and tomato leaf Inhibitor I, although the synthesis and accumulation of the three inhibitors in their respective tissues are all under different developmental or environmental regulation. 相似文献
6.
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
7.
Several benzyloxybenzaldehyde analogues were prepared and found to have significant inhibitory activity toward neutrophil superoxide formation. Consequently, these compounds were evaluated for cAMP-elevating capability. Among them, benzyloxybenzaldehyde (7), exhibiting activity equivalent to forskolin, was determined as an adenylyl cyclase activator since it elevates cAMP levels by activation of adenylyl cyclase but not by inhibition of phosphodiesterase. Having a chemical structure very different from known adenylyl cyclase activators, compound 7 is recommended by us for use as a new lead compound in the future development of adenylyl cyclase activators. 相似文献
8.
J M Dener K D Rice W S Newcomb V R Wang W B Young A R Gangloff E Y Kuo L Cregar D Putnam M Wong 《Bioorganic & medicinal chemistry letters》2001,11(13):1629-1633
A survey of charged groups and linkers for a series of symmetrical and unsymmetrical dibasic inhibitors is described, leading to several classes of potent and selective inhibitors. In particular, the benzamidine functionality was identified as the most potent charged group investigated. 相似文献
9.
Yung-Shun Su Ming-Jen Cheng Ming-Der Wu Chee-Yin Chai Aij-Lie Kwan Sheng-Han Su Yueh-Hsiung Kuo 《化学与生物多样性》2021,18(8):e2100211
Cultivation of the actinobacteria strain Isoptericola chiayiensis, a mangrove - derived actinobacteria that was isolated from a mangrove soil collected in Chiayi County, resulted in the isolation of one new 2-furanone derivative, isopterfuranone ( 1 ), one new sesquiterpenoid, isopterchiayione ( 2 ), one new benzenoid derivative, isopterinoid ( 3 ), five new flavonoids, chiayiflavans A−E ( 4 – 8 ), and 4 metabolites isolated for the first time from nature source, methyl 3-(4-methyl-2,5-dioxopyrrolidin-3-yl)propanoate ( 9 ), 3-ethyl-4-methylpyrrolidine-2,5-dione ( 10 ), chiayiensol ( 11 ) and chiayiensic acid ( 12 ). Their structures were determined through in-depth spectroscopic and mass-spectrometric analyses. Most of the isolates showed potent inhibitory effects on NO production in LPS-stimulated RAW 264.7 murine macrophages cells with IC50 values ranging from 9.36 to 40.02 μM. Of these isolates, 4 and 5 showed NO inhibitory activity with IC50 values of 17.14 and 9.36 μM, stronger than the positive control quercetin (IC50=36.95 μM). This is the first report on flavan metabolites from the genus Isoptericola. 相似文献
10.
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