全文获取类型
收费全文 | 2160篇 |
免费 | 193篇 |
出版年
2023年 | 16篇 |
2022年 | 37篇 |
2021年 | 90篇 |
2020年 | 55篇 |
2019年 | 74篇 |
2018年 | 83篇 |
2017年 | 56篇 |
2016年 | 87篇 |
2015年 | 136篇 |
2014年 | 149篇 |
2013年 | 161篇 |
2012年 | 171篇 |
2011年 | 168篇 |
2010年 | 89篇 |
2009年 | 69篇 |
2008年 | 120篇 |
2007年 | 93篇 |
2006年 | 79篇 |
2005年 | 83篇 |
2004年 | 74篇 |
2003年 | 68篇 |
2002年 | 66篇 |
2001年 | 25篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 19篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1979年 | 11篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1968年 | 6篇 |
1967年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有2353条查询结果,搜索用时 31 毫秒
1.
Emma Bricchi Marco Fornaciari Claudia Giannoni Francesca Greco Daniela Fascini Giuseppe Frenguelli Gianfranco Mincigrucci Bruno Romano 《Aerobiologia》1992,8(3):401-406
Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria. 相似文献
2.
A Bobba I Munno B Greco N M Pellegrino P Riccio E Jirillo E Quagliariello 《Biochemical and biophysical research communications》1991,180(2):1125-1129
We have applied a double tagging system in order to study whether purified myelin basic protein is able to adhere to normal human peripheral T lymphocytes without the need to purify cells. Evaluation of myelin basic protein adherence to peripheral blood mononuclear cells was determined with biotinylated myelin basic protein and fluoresceinated avidin, and lymphocyte population was identified by the corresponding phycoerythrinated monoclonal antibody. The observed adherence of myelin basic protein to T lymphocytes was found to depend on protein conformation. 相似文献
3.
The possibility of aromatization of androgen in human prostate 总被引:1,自引:0,他引:1
Y Kaburagi M B Marino R Y Kirdani J P Greco J P Karr A A Sandberg 《Journal of steroid biochemistry》1987,26(6):739-742
Aromatase in human prostate tissue was determined in homogenized human prostate (three BPH and two normal specimens) incubated with [1-beta-3H]androstenedione (radiometric method) or [1,2,6,7-3H]androstenedione (estrogen production analysis method) in the presence of NADPH. Using the former procedure, significant amounts of 3H2O, resulting from the release of 3H at the C-1 position during aromatization, were measured and these increased with incubation time and amount of tissue, whereas the amount of estrone and estradiol-17 beta resulting from the latter method and calculated from the 3H/14C ratio in preparations of purified crystal was very small. The preliminary results, which suggest that an androgen aromatase system exists in the human prostate, point to the need to further investigate the identity and properties of the metabolic products resulting from the conversion of androgen to estrogens and other metabolites. 相似文献
4.
Vittorio de Franciscis Vittorio E. Avvedimento Giulia Colletta Vincenzo Zimarino Valeria M. Ursini Fortunato Ciliberto Giancarlo Vecchio 《Experimental cell research》1987,171(2):483-491
We have exploited a recently characterized system of rat thyroid epithelial cells transformed by the wild-type (wt) and a temperature-sensitive (ts) mutant strain of the Kirsten murine sarcoma virus (Ki-MSV) in order to study the effects of the K-ras oncogene on the gene expression of differentiated thyroid epithelial cells. By using cDNAs isolated from normal thyroid glands as probes, we were able to identify three sets of cellular sequences whose expression is influenced by the v-K-ras oncogene. The first set of genes is irreversibly repressed by transformation with both the wt and the ts viruses. The second set of genes is repressed in the ts-Ki-MSV-transformed cells but not in the same cells grown at the nonpermissive temperature. A third set of genes is present at higher levels at the nonpermissive temperature than at the permissive temperature. This system has allowed us to isolate and characterize a number of cDNA clones belonging to each of these three sets of genes. These specific cDNAs are suitable probes to study phenotypical changes during transformation of epithelial cells. 相似文献
5.
6.
7.
The circadian rhythm of the N-terminus and C-terminus of the atrial natriuretic factor prohormone 总被引:1,自引:0,他引:1
D L Vesely E L Kanabrocki R B Sothern L E Scheving T H Tsai J Greco D L Bushell E Kaplan J Rumbyrt R P Sturtevant 《Chronobiology international》1990,7(1):51-57
Circadian variation in the circulating concentrations of the N-terminal and C-terminal portions of the atrial natriuretic factor prohormone (pro ANF) was evaluated in 8 men, ages 41-47, who have been followed for 19 years with respect to circadian variation in physiological variables including blood pressure and clinical chemistries. The N-terminus of the ANF prohormone contains two peptides consisting of amino acids 1-30 and 31-67 while the C-terminus contains 1 peptide (amino acids 99-126) of this 126 amino acid prohormone which lower blood pressure and have natriuretic properties. To determine if either the N-terminus and/or the C-terminus of the prohormone have a circadian variation in their circulating plasma concentrations these 8 men had blood samples obtained for radiommunoassay every 3 hr during a 24-hr period. Three radiommunoassays which immunologically recognize (1) the whole N-terminus (i.e. amino acids 1-98), (2) the midportion of the N-terminus (amino acids 31-67) and (3) the C-terminus (amino acids 99-126) of the ANF prohormone were utilized. The whole N-terminus, the midportion of the N-terminus which circulates after being proteolytically cleaved from the rest of the N-terminus, and the C-terminus each had a peak circulating concentration between 0400 and 0700 which were significantly (P less than 0.001) higher than their concentrations at any other time throughout the 24-hr period.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
8.
E. L. Kanabrocki R. B. Sothern L. E. Scheving F. Halberg J. E. Pauly J. J. Greco B. A. Nemchausky M. Debartolo E. Kaplan J. B. McCormick J. H. Olwin G. E. Marks T. Bird D. P. Redmond R. C. Graeber A. Ferrara W. J. M. Hrushesky 《Chronobiology international》1988,5(3):237-284
At 3-hr intervals over a 24-hr span, 36 systemic, serologic and urinary variables were examined in 7 men in their mid 20's in the Spring of 1969, and again in the same 7 men in the Spring of 1979 under a similar chronobiologic protocol, using the same chemical and numerical analytical procedures. The variables examined for rhythms by cosinor were: vital signs--blood pressure (systolic, diastolic, pulse pressure and mean arterial pressure), heart rate, intraocular pressure (left and right), oral temperature; serum components--albumin, albumin/globulin ratio, total bilirubin, calcium, carbon dioxide, chlorides, bilirubin, cholesterol, globulin, glucose, potassium, sodium, sodium/potassium ratio, transaminase, triglycerides, total protein, urea nitrogen; and urine components--calcium, calcium/magnesium ratio, creatinine, magnesium, pH, potassium, sodium, sodium/potassium ratio, urea clearance, urea nitrogen, volume and zinc. Although all subjects appeared clinically healthy in 1969 and in 1979, certain inter-study differences were observed in a number of rhythm parameters of different variables. Statistically significant increases in mesor for the group as a whole were observed for serum Ca, cholesterol, Cl, CO2, K, Na, and while statistically significant mesor decreases for a group as a whole were noted in serum glucose and transaminase. Statistically significant increases in amplitude for the group as a whole were observed in serum chloride and urinary Na/K ratio, while statistically significant decreases were observed in amplitude for blood pressure, heart rate, serum albumin, A/G ratio, globulin, glucose, protein, sodium and transaminase.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
9.
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
10.
M H Carstens R J Greco D J Hurwitz D E Tolhurst 《Plastic and reconstructive surgery》1991,87(4):615-626
The anatomic boundaries and vascular supply of the subgaleal fascia have been described previously. The thin and malleable subgaleal fascia was selected for difficult reconstructive problems in seven patients. This flap has been based on either the supraorbital or the superficial temporal vascular leash. The subgaleal fascia is readily dissected from superficial galea and deep periosteum, leaving behind a well-vascularized scalp and a skin-graftable calvarium. The flap conforms to a cartilage framework for ear reconstruction. It takes a skin graft well. The subgaleal fascia can patch dural defects and fill sinus dead space. It has been used to augment facial contour. Free vascularized transfer of the subgaleal fascia has included the temporoparietal fascia, which was partially split from the subgaleal fascia for bilobed flap resurfacing of the hand. The subgaleal fascial flap should be considered when ultrathin, vascularized coverage is needed. 相似文献