全文获取类型
收费全文 | 2114篇 |
免费 | 149篇 |
专业分类
2263篇 |
出版年
2022年 | 28篇 |
2021年 | 38篇 |
2020年 | 31篇 |
2019年 | 46篇 |
2018年 | 54篇 |
2017年 | 42篇 |
2016年 | 60篇 |
2015年 | 97篇 |
2014年 | 84篇 |
2013年 | 151篇 |
2012年 | 180篇 |
2011年 | 143篇 |
2010年 | 84篇 |
2009年 | 71篇 |
2008年 | 113篇 |
2007年 | 130篇 |
2006年 | 103篇 |
2005年 | 94篇 |
2004年 | 109篇 |
2003年 | 91篇 |
2002年 | 80篇 |
2001年 | 24篇 |
2000年 | 26篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1981年 | 13篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1975年 | 13篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 7篇 |
1967年 | 11篇 |
排序方式: 共有2263条查询结果,搜索用时 15 毫秒
1.
L Brun-Samarcq S Gallina A Philippi F Demenais G Vaysseix E Barillot 《Bioinformatics (Oxford, England)》1999,15(4):345-346
SUMMARY: We developed a collaborative pedigree environment called CoPE. This environment includes a Java program for drawing pedigrees and a standardized system for pedigree storage. Unlike other existing pedigree programs, this software is particularly intended for epidemiologists in the sense that it allows customized automatic drawing of large numbers of pedigrees and remote and distributed consultation of pedigrees. AVAILABILITY: At http://www.infobiogen.fr/services/CoPE 相似文献
2.
3.
Two methods of measuring respiratory transfer impedance (Ztr) were compared in 14 normal subjects, from 4 to 30 Hz, 1) studying the relationship between transrespiratory pressure (Prs) and flow at the chest when varying pressure at the mouth (Ztrm) and 2) studying the relationship between Prs and flow at the mouth when varying pressure around the chest wall (Ztrw). The similarity of the two relationships was expected on the basis of a T-network model. Almost identical phase responses were obtained from the two methods. Pressure-flow ratios were slightly larger for Ztrw than for Ztrm, but differences did not exceed 2% on average in 11 of 14 subjects. When the data were analyzed with the six-coefficient model proposed by DuBois et al. (J. Appl. Physiol. 8: 587-594, 1956), similar values were found for tissue compliance and tissue inertance but slightly different values for gaseous inertance in the airways (1.97 +/- 0.35 X 10(-2) cmH2O X l-1 X s2 for Ztrw vs. 1.73 +/- 0.26 for Ztrm; P less than 0.01). Similar results were also found for total respiratory resistance but with a slightly larger contribution of airway resistance for Ztrw (64 +/- 14 vs. 57 +/- 10%; P less than 0.05). As a practical conclusion it is recommended to measure Ztrw, which is technically much easier. 相似文献
4.
J Stachura M Pietroń K Nowak Z Rudzki W Nowak 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1989,27(4):227-231
DAKO quick staining kits were used to immunostainings for Epithelial Membrane Antigen (EMA) Neuron Specific Enolase (NSE) and S-100 protein (S-100) in 18 carcinoid tumors of the gastrointestinal tract classified according to Soga and Tazawa. EMA was always absent in carcinoid tumors, being at the same time present within glandular epithelium. 88% of cases showed positive immunostaining for NSE. S-100 immunostaining showed immunopositive stellate cells present within the tumor especially within type A carcinoids. In addition in one carcinoid tumor thick, strongly S-100 positive bundles were noticed at the periphery of nests of tumor cells. Combined immunohistochemical and ultrastructural studies are needed to elucidate interrelation of neoplastic and neural elements within carcinoid tumorsa. 相似文献
5.
Anna Maria Greco Pasquale Gambardella Raffaella Sticchi Diego D'aponte Pietro De Franciscis 《Chronobiology international》1988,5(3):217-225
Circadian rhythms of serotonin (5HT), its precursors tryptophan (TP) and 5-hydroxy-tryptophan (5HTP) and its acid catabolite 5-hydroxy-indoleacetic acid (5HIAA), were determined in the hypothalamus of control rats and rats which had been treated continuously with subcutaneous imipramine (10 mg/kg/day) for 2 weeks.
Rats were individually housed and entrained to LD12:12. Controls showed the 5HT and TP peaks in the light and dark periods respectively, as reported in the literature, but no inverted correlation (antiphase) between SHT and 5HIAA rhythms.
Imipramine significantly modified circadian rhythm characteristics: the 5HT acrophase was advanced, that of TP and 5HIAA was delayed. Imipramine also significantly increased hypothalamic SHT and TP concentrations. 相似文献
Rats were individually housed and entrained to LD12:12. Controls showed the 5HT and TP peaks in the light and dark periods respectively, as reported in the literature, but no inverted correlation (antiphase) between SHT and 5HIAA rhythms.
Imipramine significantly modified circadian rhythm characteristics: the 5HT acrophase was advanced, that of TP and 5HIAA was delayed. Imipramine also significantly increased hypothalamic SHT and TP concentrations. 相似文献
6.
7.
Chemical modification of essential carboxyl group and histidine residue in the plasma-membrane 5'-nucleotidase 总被引:1,自引:0,他引:1
J Harb K Meflah A di Pietro S Bernard D C Gautheron 《Biochimica et biophysica acta》1986,870(2):320-326
An investigation, using specific chemical reagents, of the amino acids involved in the catalytic activity of the purified 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) from bovine liver plasma membranes, was carried out. The enzyme was irreversibly inactivated by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The inhibition kinetics were of the first-order type and decreased partially in the presence of nucleotides and divalent cations. These results indicate for the first time that a carboxyl group is essential for the catalytic process of 5'-nucleotidase. Moreover, chemical modification by diethylpyrocarbonate also produced inactivation of the enzyme and showed a differential spectrum with a peak at 240 nm characteristic of N-carbethoxyhistidine residues. This inactivation was efficiently released upon decarbethoxylation by hydroxylamine only when the extent of inactivation, due to low concentration of diethylpyrocarbonate, was limited. The time-dependent inactivation followed first-order kinetics and nucleotides afforded significant protection against diethylpyrocarbonate modification. The results indicate the involvement of the histidine residue in catalysis. 相似文献
8.
9.
10.
Walter Malorni Pietro L. Indovina Giuseppe Arancia Stefania Meschini Maria T. Santini 《In vitro cellular & developmental biology. Plant》1990,26(4):399-410
Summary This paper describes the microscopic evidence supporting a cesium-induced delay in the fusion of chick embryo myoblast membranes
during in vitro myogenic differentiation. We have recently demonstrated that the sharp decrease in the conductivity and permittivity
of the membranes of these myogenic cells at the time of fusion is delayed 30 h by the addition of cesium to the culture medium
(Santini et al., Biochim. Biophys. Acta 945:56–64; 1988). We report here that this delay in fusion is substantiated by direct
microscopic observation and that cesium also induces ultrastructural changes in the myoblast cells themselves. Possible mechanisms
by which cesium may cause both the delay in fusion as well as the ultrastructural changes observed are discussed.
This investigation was partially supported by an Italian Consiglio Nazionale delle Ricerche grant 85.00.304.02 (to P. L. I.). 相似文献