全文获取类型
收费全文 | 7791篇 |
免费 | 946篇 |
国内免费 | 4篇 |
专业分类
8741篇 |
出版年
2021年 | 83篇 |
2020年 | 61篇 |
2019年 | 87篇 |
2018年 | 90篇 |
2017年 | 84篇 |
2016年 | 123篇 |
2015年 | 248篇 |
2014年 | 247篇 |
2013年 | 276篇 |
2012年 | 399篇 |
2011年 | 418篇 |
2010年 | 234篇 |
2009年 | 214篇 |
2008年 | 346篇 |
2007年 | 395篇 |
2006年 | 347篇 |
2005年 | 334篇 |
2004年 | 321篇 |
2003年 | 302篇 |
2002年 | 330篇 |
2001年 | 197篇 |
2000年 | 197篇 |
1999年 | 164篇 |
1998年 | 106篇 |
1997年 | 96篇 |
1996年 | 87篇 |
1995年 | 87篇 |
1994年 | 79篇 |
1993年 | 84篇 |
1992年 | 112篇 |
1991年 | 134篇 |
1990年 | 112篇 |
1989年 | 119篇 |
1988年 | 133篇 |
1987年 | 96篇 |
1986年 | 93篇 |
1985年 | 102篇 |
1984年 | 138篇 |
1983年 | 91篇 |
1982年 | 97篇 |
1981年 | 89篇 |
1980年 | 70篇 |
1979年 | 89篇 |
1978年 | 80篇 |
1977年 | 71篇 |
1976年 | 70篇 |
1974年 | 88篇 |
1973年 | 82篇 |
1971年 | 66篇 |
1968年 | 59篇 |
排序方式: 共有8741条查询结果,搜索用时 15 毫秒
51.
52.
53.
Meiheng Yang Howard Allen Hisao Fukushima Richard A. DiCioccio 《Glycoconjugate journal》1984,1(1):15-19
Fucosidosis is an autosomal recessive lysosomal storage disease resulting from the absence of -l-fucosidase activity. Two natural missense mutations (G197A) and (A860G) within the -l-fucosidase gene have been reported to be homozygous in four patients with fucosidosis. Expression of wild-type and mutated -l-fucosidase cDNAs in COS-1 cells revealed complete deficiency of -l-fucosidase for the G197A transition and a normal level of enzyme for A860G. We therefore conclude that the change of G197A is responsible for fucosidosis in the patients while A860G is a normal polymorphic variant of -l-fucosidase. 相似文献
54.
Structure and gel formation in pig gastric mucus 总被引:1,自引:0,他引:1
55.
Determination of betaxolol, a new beta-blocker, by gas chromatography mass spectrometry: application to pharmacokinetic studies 总被引:1,自引:0,他引:1
Betaxolol, a beta selective adrenoceptor antagonist recently approved for the treatment of hypertension, was determined by monitoring in chemical ionization mode with ammonia the [MH]+ ions of the trimethylsilyl derivatives of the drug and of its internal standard [2H5)betaxolol). Its pharmacokinetic profile obtained following administration of a 20 mg oral dose was characterized by a half-life of 22 h and a bioavailability of 85%. The main acid metabolite formed by elimination of the isopropylamino group may also be determined as the methyl TMS derivative but methylation with BF3-methanol should be used with caution since it may induce the opening of the cyclopropyl group. The routine electron capture determination procedure was compared to this mass spectrometric method and an excellent correlation was found (r = 0.9974). Both procedures have the same sensitivity (1 ng ml-1). Finally it was observed that under electron impact mode betaxolol trimethylsilyl side chain rearranged to lose TMS-O-CH=CH2; this elimination was confirmed by deuterium labelling studies. 相似文献
56.
57.
The changes in concentrations of a number of trace elements have been determined by neutron activation analysis in tumor, liver, and blood serum of host animals, following local irradiation of a solid tumor (3924A Morris hepatoma). These trace element changes are compared to the changes observed in a parallel study of the effects of the chemotherapeutic agent 5-fluorouracil on the same tumor. Since the changes in some of the trace elements parallel the changes in pathological and biochemical factors resulting from the insult of radiation on the tumor, these trace elements may be valuable markers in the clinical evaluation of therapeutic response and as monitors of the long term effects of cancer therapy. 相似文献
58.
Corticotrophin releasing factor (CRF) decreases food intake after starvation and during the nocturnal feeding phase in rats. This decrease appears to be associated with CRF producing a marked increase in grooming. The effects of CRF on food intake and grooming are independent of its effects on the pituatary. CRF is a putative mediator of stress-induced anorexias. 相似文献
59.
Graham S. Baldwin Alphonse Galdes H.Allen O. Hill Stephen G. Waley Edward P. Abraham 《Journal of inorganic biochemistry》1980,13(3):189-204
β-Lactamase II has two metal-binding sites. The electronic spectra of Cd(II)- and Co(II)-substituted β-lactamase II have been investigated. It is suggested that a thiol ligand is involved in metal binding at the first site. The stoichiometric dissociation constants for Co(II) binding to β-lactamase II were estimated to be 0.13 and 2.66 mM (pH 6.0, 4°C, 1 M NaCl) by equilibrium dialysis. Competition between Zn(II) and Co(II) for the first metal binding site suggests a value of 0.7 μM (pH 6.0, 30°C, 1 M NaCl) for the dissociation constant o Zn(II).The electronic spectra of the Co(II) enzyme lead to the suggestion that the coordination geometries around the metal ions in the first and second sites are related to those of a distorted tetrahedron and octahedron, respectively. 相似文献
60.
Richard L. Rapport II George A. Ojemann Allen R. Wyler Arthur A. Ward Jr. 《The Western journal of medicine》1977,127(3):185-189
Therapy with anticonvulsant drugs reduces the frequency and severity of seizures in many but not all epileptic patients. Unfortunately, in a significant number control remains poor even when maximal doses of multiple anticonvulsant drugs are given. Some of these patients are candidates for surgical treatment of epilepsy. The operative management of convulsive disorders is a well-established technique and is available in some centers. In selected cases, such operations are both safe and effective, with good longterm improvement or complete control in 76 percent of patients. We have summarized the 24-year experience with surgical operation for epilepsy at the University of Washington Medical Center. 相似文献