全文获取类型
收费全文 | 5755篇 |
免费 | 507篇 |
国内免费 | 4篇 |
专业分类
6266篇 |
出版年
2023年 | 30篇 |
2022年 | 49篇 |
2021年 | 108篇 |
2020年 | 82篇 |
2019年 | 89篇 |
2018年 | 108篇 |
2017年 | 87篇 |
2016年 | 175篇 |
2015年 | 225篇 |
2014年 | 236篇 |
2013年 | 332篇 |
2012年 | 381篇 |
2011年 | 344篇 |
2010年 | 229篇 |
2009年 | 213篇 |
2008年 | 273篇 |
2007年 | 294篇 |
2006年 | 238篇 |
2005年 | 223篇 |
2004年 | 201篇 |
2003年 | 199篇 |
2002年 | 200篇 |
2001年 | 155篇 |
2000年 | 154篇 |
1999年 | 158篇 |
1998年 | 67篇 |
1997年 | 58篇 |
1996年 | 70篇 |
1995年 | 52篇 |
1994年 | 61篇 |
1993年 | 44篇 |
1992年 | 75篇 |
1991年 | 96篇 |
1990年 | 78篇 |
1989年 | 80篇 |
1988年 | 86篇 |
1987年 | 65篇 |
1986年 | 61篇 |
1985年 | 60篇 |
1984年 | 54篇 |
1983年 | 41篇 |
1982年 | 25篇 |
1981年 | 27篇 |
1980年 | 29篇 |
1979年 | 48篇 |
1977年 | 29篇 |
1976年 | 22篇 |
1975年 | 29篇 |
1974年 | 31篇 |
1971年 | 23篇 |
排序方式: 共有6266条查询结果,搜索用时 15 毫秒
21.
22.
An abnormal terminal X-Y interchange accounts for most but not all cases of human XX maleness 总被引:14,自引:0,他引:14
To determine if human XX maleness results from an abnormal chromosomal X-Y interchange, we studied the inheritance of the paternal pseudoautosomal region in nine patients. Those six patients in whom Y-specific DNA was found (Y(+)) inherited the entire pseudoautosomal region from the paternal Y chromosome and lost that of the paternal X chromosome. Moreover, in three Y(+) cases, we observed the deletion of a paternal Xp locus tightly linked to the pseudoautosomal region. These results definitively show that an abnormal and terminal X-Y interchange during paternal meiosis causes Y(+)XX maleness. In contrast, no abnormal X-Y interchange was observed in any of the three Y(-) cases analyzed, suggesting that maleness can occur in the absence of any Y-specific DNA. 相似文献
23.
I Lalowicz J Cie?la A Kozaczka W Poborski K Rozek-Lesiak M Machalski 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1989,44(25-26):603-6, 613
The results of multidrug therapy of 44 male patients with non-seminomatous testicular tumours are discussed. The diagnosed tumours were of all stages of the clinical advances and were treated with combined chemotherapy (surgery and PVP regimen). Thirty two patients (73%) are followed up between 7 and 103 months and survived, complete remission is noted in 29 patients (66%) including 6 patients who survived over 5 years. Symptoms of the tumour are found in 3 patients. Twelve patients (27%) died. The treatment did not produce life-threatening complications. The obtained results have been compared with those reported by other authors. 相似文献
24.
Summary A basic procedure was developed to produce high-protein amaranth flour (HPAF) using a commercial preparation of heat-stable alpha-amylase. Slurries (20%, w/v) of gelatinized whole flour were liquefied at 70 and 90°C, pH 6.5, 0.1% (w/v) enzyme concentration and 30 min hydrolysis time. Protein content of raw flour was increased from 15 to 29.6 or 39.3% at liquefaction temperatures of 70 or 90°C, respectively. Some physicochemical and functional properties of HPAF were assessed. HPAF might be used as a dry milk extender. 相似文献
25.
A study of the monomeric chromophore of the oligopeptides netropsin (1), distamycin III (2), and distamycin V (3) by polarization spectroscopy techniques and molecular orbital calculations is reported. Linear dichroism spectra of the monomeric model compounds 1-methyl-2(ethylcarbamoyl)-4-acetamido-pyrrole (4) and 1-methyl-2(ethylcarbamoyl)-pyrrole (5) dissolved and oriented in lyotropic and thermotropic liquid crystals provide, together with the magnetic CD spectra, experimental checks of the theoretical calculations. The polarization directions of the investigated transition obtained by these means in this study allow us to build up in the following paper the exciton states of (1)-(3) and these provide a stereochemical interpretation of the flow linear dichroism spectra of the complexes of DNA with (2) and (3). 相似文献
26.
Evidence for the formation of covalent bonds between macromolecules in the domain of the wall of Candida albicans mycelial cells 总被引:9,自引:0,他引:9
V Elorza S Mormeneo F Garcia de la Cruz C Gimeno R Sentandreu 《Biochemical and biophysical research communications》1989,162(3):1118-1125
An O-glycosylated mannoprotein, after its incorporation into the wall, showed an increase in its molecular weight, due at least to its association with N-glycosidic sugar chain(s). This was shown by rendering the material soluble after partial degradation of the wall structure. At present it is unknown whether this phenomenon is due to an additional transglycosylation process or whether the partial degradation of the wall solubilizes a supramolecular structure formed between the original O-glycosylated protein which becomes linked either directly or indirectly through a protein to the N-sugar chain(s). 相似文献
27.
Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae 总被引:1,自引:0,他引:1
The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text. 相似文献
28.
Summary A new type of multistage fluidised-bed reactor was constructed to avoid the fluidisation irregularities by slow stirring of the bed. Aminoacylase immobilized on a polyacrylamide type bead polymer was used as biocatalyst for resolution of racemic amino acids. The efficiency was considerably higher than that of a traditional packed-bed reactor. 相似文献
29.
A new technique for the treatment of palpebral bags 总被引:13,自引:0,他引:13
A new technique for the treatment of palpebral bags is presented. The technique consists of returning fat to the orbital cavity and retaining it by means of a continuous suture (with nonabsorbable filament) of the capsulopalpebral fascia to the periosteum of the lower orbital rim. The anatomic basis for the technique, after examination of the relevant literature and dissection on fresh cadavers, is analyzed. The procedure followed and results obtained are described in detail. Evaluation of the results suggests to the authors that this might be the method to be applied in the majority of patients. 相似文献
30.