全文获取类型
收费全文 | 1751篇 |
免费 | 78篇 |
专业分类
1829篇 |
出版年
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 33篇 |
2015年 | 47篇 |
2014年 | 57篇 |
2013年 | 137篇 |
2012年 | 88篇 |
2011年 | 71篇 |
2010年 | 52篇 |
2009年 | 61篇 |
2008年 | 111篇 |
2007年 | 105篇 |
2006年 | 101篇 |
2005年 | 101篇 |
2004年 | 102篇 |
2003年 | 71篇 |
2002年 | 110篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 27篇 |
1998年 | 20篇 |
1997年 | 26篇 |
1996年 | 13篇 |
1995年 | 25篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 28篇 |
1991年 | 29篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 6篇 |
1984年 | 18篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有1829条查询结果,搜索用时 15 毫秒
91.
Phenanthropyran derivatives from Phalaenopsis equestris 总被引:1,自引:0,他引:1
Two phenanthropyran derivatives, 3-methoxy-2,7-dihydroxy-5H-phenanthro[4,5-bcd]pyran and 2,3,7-trihydroxy-5H-phenanthro[4,5-bcd]pyran were isolated from the orchid Phalaenopsis equestri. Their chemical structures were elucidated from spectroscopic (NMR, MS etc.) analyses. 相似文献
92.
Imai A Nashida T Shimomura H 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1999,124(4):206-403
We investigated phosphodiesterase (PDE) isozymes, which hydrolyze cAMP, in rodent parotid glands (mouse, hamster and guinea pig) in order to clarify the effects of cGMP and Ca/calmodulin on the regulation of cellular cAMP and compared them with those of the rat. More than 80% of the activities were in the supernatant fractions except for the hamster. The isozymes were fractionated using Mono Q ion-exchange column. The mouse parotid PDEs consisted of PDE1 (Ca/calmodulin-dependent), PDE2 (cGMP-stimulated), PDE3 (cGMP-inhibited) and PDE4 (cAMP-specific) similar to those of the rat. PDE3 was not detected in the hamster, and PDE4 was not detected in the guinea pig. PDE activities in the supernatant of the mouse and the hamster were stimulated by cGMP, and that of the guinea pig was stimulated by Ca/calmodulin. These results suggest that various PDE isozymes are present in the parotid gland of several species of order Rodentia. There seems to be differences among the species with regard to the PDE isozymes. 相似文献
93.
Paradoxical decrease of an adipose-specific protein, adiponectin, in obesity 总被引:189,自引:0,他引:189
94.
Ihara M Matsuda K Shimomura M Sattelle DB Komai K 《Bioscience, biotechnology, and biochemistry》2004,68(3):761-763
To compare the actions of clothianidin, a neonicotinoid acting on insect nicotinic acetylcholine receptors, and related compounds with that of imidacloprid, the compounds were tested on the Drosophila SAD-chicken beta2 nicotinic acetylcholine receptor expressed in Xenopus laevis oocytes using two-electrode voltage-clamp electrophysiology. The maximum response of the SAD beta 2 nicotinic receptor to clothianidin was larger than that observed for acetylcholine. Ring breakage of the imidazolidine ring of imidacloprid resulting in the generation of a guanidine group was critical for this super agonist action. 相似文献
95.
96.
Leah?C.?Solberg Amber?E.?Baum Nasim?Ahmadiyeh Kazuhiro?Shimomura Renhua?Li Fred?W.?Turek Gary?A.?Churchill Joseph?S.?Takahashi Eva?E.?RedeiEmail author 《Mammalian genome》2004,15(8):648-662
The Wistar–Kyoto (WKY) rat exhibits physiological and behavioral similarities to endophenotypes of human depression. In the forced swim test (FST), a well-characterized antidepressant-reversible test for behavioral despair in rodents, WKYs express characteristics of behavioral despair; increased immobility, and decreased climbing. To map genetic loci linked to behavior in the FST, we conducted a quantitative trait loci (QTL) analysis of the segregating F2 generation of a WKY × Fisher 344 (F344) reciprocal intercross. Using linear-model-based genome scans to include covariate (sex or lineage)-by-QTL interaction effects, four significant QTL influencing climbing behavior were identified. In addition, we identified three, seven, and two suggestive QTL for climbing, immobility, and swimming, respectively. One of these loci was pleiotropic, affecting both immobility and climbing. As found in human linkage studies, several of these QTL showed sex- and/or lineage-dependent effects. A simultaneous search strategy identified three epistatic locus pairs for climbing. Multiple regression analysis was employed to characterize the joint contributions of these QTL and to clarify the sex- and lineage-dependent effects. As expected for complex traits, FST behavior is influenced by multiple QTL of small effect, each contributing 5%–10%, accounting for a total 10%–30% of the phenotypic variance. A number of loci mapped in this study share overlapping candidate regions with previously identified emotionality QTL in mice as well as with susceptibility loci recognized by linkage or genome scan analyses for major depression or bipolar disorder in humans. The presence of these loci across species suggests that these QTL may represent universal genetic factors contributing to mood disorders. 相似文献
97.
98.
Funatogawa K Hayashi S Shimomura H Yoshida T Hatano T Ito H Hirai Y 《Microbiology and immunology》2004,48(4):251-261
Helicobacter pylori is a major etiological agent in gastroduodenal disorders. In this study, we isolated 36 polyphenols and 4 terpenoids from medicinal plants, and investigated their antibacterial activity against H. pylori in vitro. All hydrolyzable tannins tested demonstrated promising antibacterial activity against H. pylori. Monomeric hydrolyzable tannins revealed especially strong activity. Other compounds demonstrated minimal antibacterial activity with a few exceptions. A monomeric hydrolyzable tannin, Tellimagrandin I demonstrated time- and dose-dependent bactericidal activity against H. pylori in vitro. On the other hand, hydrolyzable tannins did not affect the viability of MKN-28 cells derived from human gastric epithelium. Hydrolyzable tannins, therefore, have potential as new and safe therapeutic regimens against H. pylori infection. Furthermore, we investigated effects of hydrolyzable tannins on lipid bilayer membranes. All the hydrolyzable tannins tested demonstrated dose-dependent membrane-damaging activity. However, it remains to be elucidated whether their membrane-damaging activity directly contributes to their antibacterial action. 相似文献
99.
Galassetti P Tate D Neill RA Morrey S Wasserman DH Davis SN 《American journal of physiology. Endocrinology and metabolism》2004,287(1):E16-E24
A marked sexual dimorphism exists in healthy individuals in the pattern of blunted neuroendocrine and metabolic responses following antecedent stress. It is unknown whether significant sex-related counterregulatory differences occur during prolonged moderate exercise after antecedent hypoglycemia in type 1 diabetes mellitus (T1DM). Fourteen patients with T1DM (7 women and 7 men) were studied during 90 min of euglycemic exercise at 50% maximal O(2) consumption after two 2-h episodes of previous-day euglycemia (5.0 mmol/l) or hypoglycemia of 2.9 mmol/l. Men and women were matched for age, glycemic control, duration of diabetes, and exercise fitness and had no history or evidence of autonomic neuropathy. Exercise was performed during constant "basal" intravenous infusion of regular insulin (1 U/h) and a 20% dextrose infusion, as needed to maintain euglycemia. Plasma glucose and insulin levels were equivalent in men and women during all exercise and glucose clamp studies. Antecedent hypoglycemia produced a relatively greater (P < 0.05) reduction of glucagon, epinephrine, norepinephrine, growth hormone, and metabolic (glucose kinetics) responses in men compared with women during next-day exercise. After antecedent hypoglycemia, endogenous glucose production (EGP) was significantly reduced in men only, paralleling a reduction in the glucagon-to-insulin ratio and catecholamine responses. In conclusion, a marked sexual dimorphism exists in a wide spectrum of blunted counterregulatory responses to exercise in T1DM after prior hypoglycemia. Key neuroendocrine (glucagon, catecholamines) and metabolic (EGP) homeostatic responses were better preserved during exercise in T1DM women after antecedent hypoglycemia. Preserved counterregulatory responses during exercise in T1DM women may confer greater protection against hypoglycemia than in men with T1DM. 相似文献
100.