全文获取类型
收费全文 | 1609860篇 |
免费 | 149626篇 |
国内免费 | 2056篇 |
专业分类
1761542篇 |
出版年
2021年 | 18192篇 |
2019年 | 16328篇 |
2018年 | 19121篇 |
2017年 | 17815篇 |
2016年 | 29123篇 |
2015年 | 43483篇 |
2014年 | 51575篇 |
2013年 | 78066篇 |
2012年 | 45688篇 |
2011年 | 36635篇 |
2010年 | 47065篇 |
2009年 | 47495篇 |
2008年 | 33577篇 |
2007年 | 32531篇 |
2006年 | 36061篇 |
2005年 | 36925篇 |
2004年 | 36153篇 |
2003年 | 33403篇 |
2002年 | 31313篇 |
2001年 | 45717篇 |
2000年 | 43414篇 |
1999年 | 40497篇 |
1998年 | 27030篇 |
1997年 | 26966篇 |
1996年 | 26212篇 |
1995年 | 24408篇 |
1994年 | 24066篇 |
1993年 | 23286篇 |
1992年 | 35348篇 |
1991年 | 33870篇 |
1990年 | 32876篇 |
1989年 | 33245篇 |
1988年 | 30774篇 |
1987年 | 29044篇 |
1986年 | 27722篇 |
1985年 | 29557篇 |
1984年 | 27801篇 |
1983年 | 24422篇 |
1982年 | 23090篇 |
1981年 | 21963篇 |
1980年 | 20569篇 |
1979年 | 24005篇 |
1978年 | 21555篇 |
1977年 | 20441篇 |
1976年 | 19512篇 |
1975年 | 19800篇 |
1974年 | 20789篇 |
1973年 | 20974篇 |
1972年 | 18275篇 |
1971年 | 16765篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
P S Simavorian D A Gevorkian I L Saakian A B Iordanian 《Biulleten' eksperimental'no? biologii i meditsiny》1987,103(3):310-312
It has been experimentally and clinically established that the determination of leucine-aminotransferase activity in the blood serum and abdominal exudate may serve as a marker for the early determination of pancreonecrosis and edematous (serous) pancreatitis. 相似文献
992.
Renal transport and metabolism of nicotinic acid 总被引:1,自引:0,他引:1
993.
994.
Leslie A. Holladay Phillip Wilder 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,629(1):156-167
The effect of cationic, anionic and nonionic detergents on the EPR spectrum of spin-labeled somatostatin has been studied. At detergent concentrations well above the critical micelle concentration, nonionic detergents do not alter the EPR spectrum. Sodium dodecyl sulfate markedly alters both the line height ratio and the hyperfine splitting constant, whilst dodecyltrimethylammonium bromide alters only slightly the hyperfine splitting constant and line height ratio. The somatostatin-sodium dodecyl sulfate complex appeared monodisperse by sedimentation equilibrium with about 17 g bound detergent per g peptide. Circular dichroic and difference spectra of the dodecyl sulfate-somatostatin complex show that the tryptophanyl residue is buried in a nonpolar environment and that the secondary and tertiary structure of the peptide is markedly altered. Sedimentation equilibrium studies suggest that two types of dodecyltrimethylammonium-somatostatin complex exist. One type resembles the dodecyl sulfate-peptide complex, whilst the other appears to include several peptide units with only about one gram bound detergent per gram peptide. 相似文献
995.
P Kendall-Taylor K Hall D G Johnston R W Prescott 《BMJ (Clinical research ed.)》1982,285(6340):465-467
The effect of pergolide mesylate was studied in two previously untreated men with large prolactinomas and exceptionally high prolactin concentrations. The study was designed to determine whether pergolide would be effective in alleviating symptoms, correcting hormonal abnormalities and shrinking the tumour. Starting with 50 micrograms daily the dose of pergolide was slowly increased over 10 weeks to 1 mg once daily, when repeat assessment was performed. Both patients reported complete relief of symptoms, with no side effects. Serum prolactin concentration was suppressed to normal in both subjects, and evidence to suggest tumour shrinkage was observed. Pergolide appears to be effective treatment for men with large prolactinomas. 相似文献
996.
997.
The effect of estradiol on the brain concentration of immunoreactive beta-endorphin (beta-EP) and C-terminal ACTH (CLIP) was studied in ovariectomized rats. Dopamine, a known inhibitor of pituitary intermediate lobe pro-opiomelanocortin (POMC), was examined as a possible mediator of the estradiol induced changes in brain POMC. Animals were treated for 1 or 3 weeks with either 1) saline; 2) silastic estradiol implants; or 3) estradiol implants plus haloperidol 1 mg/kg/day. After one week of treatment no significant change in hypothalamic beta-EP content was noted in any group compared to the control level of 4.13 +/- .33 (SEM) pmoles although in the neurointermediate lobe beta-EP increased from 566 +/- 72 to 942 +/- 73 pmoles after haloperidol (p less than .005). After 3 weeks, however, hypothalamic beta-EP decreased from 3.96 +/- .28 to 2.74 +/- .19 pmoles (p less than .005) and C-terminal ACTH decreased from 3.78 +/- .33 to 2.82 +/- .18 pmoles (p less than .02) in the estradiol treated rats. This estradiol induced decrease in the hypothalamic content of beta-EP and C-terminal ACTH was not blocked by haloperidol. We conclude that estradiol lowers the hypothalamic content of beta-EP and CLIP and that this effect does not appear to be mediated by dopamine. 相似文献
998.
999.
A G Buiavykh O S Medvedev A F Stukanov 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(7):28-30
The effect of low-frequency magnetic field (MF) on systemic blood pressure has been studied in chronic experiments on 21 spontaneously hypertensive rats. The animals' kidney area was exposed to MF (induction value 30T). Direct blood pressure measurements have revealed an antihypertensive effect. 相似文献
1000.
A possible virus cryptic in carnation 总被引:1,自引:0,他引:1
Small isometric virus-like particles were found in low concentration in apparently healthy carnations of the Mediterranean, miniature and Chinese type but not in eleven Sim cultivars tested. Most carnations containing these particles were from Italy but some were from France and the USA. The particles were not transmitted by grafting or by mechanical inoculation but were seed-transmitted to a large proportion of seedlings. Antisera to partially purified particles were obtained. The particles did not react with antisera to twenty-eight isometric plant viruses or virus-like particles but were serologically related to similar particles found in carnations in England, Holland and Israel. When negatively stained, the particles were isometric with a diameter of about 29 nm and a rounded rather than angular profile, but without clear substructure; some particles were penetrated by the stain. The particles remained intact in neutral sodium phosphotungstate. After isopycnic centrifugation in CsCl solution, preparations of particles formed a main band of mean density 1.377 g/ml and other fainter bands that varied in intensity and position in different preparations. In thin sections of carnations, no virus-like particles or cytological abnormalities were observed. 相似文献