全文获取类型
收费全文 | 1052651篇 |
免费 | 126402篇 |
国内免费 | 584篇 |
出版年
2016年 | 11842篇 |
2015年 | 17544篇 |
2014年 | 20238篇 |
2013年 | 28655篇 |
2012年 | 32263篇 |
2011年 | 32474篇 |
2010年 | 22078篇 |
2009年 | 20789篇 |
2008年 | 29497篇 |
2007年 | 30247篇 |
2006年 | 28378篇 |
2005年 | 27290篇 |
2004年 | 26870篇 |
2003年 | 26096篇 |
2002年 | 25329篇 |
2001年 | 44800篇 |
2000年 | 45349篇 |
1999年 | 36342篇 |
1998年 | 14113篇 |
1997年 | 14897篇 |
1996年 | 14238篇 |
1995年 | 13502篇 |
1994年 | 13216篇 |
1993年 | 13215篇 |
1992年 | 31061篇 |
1991年 | 30286篇 |
1990年 | 29609篇 |
1989年 | 28921篇 |
1988年 | 26698篇 |
1987年 | 26082篇 |
1986年 | 24281篇 |
1985年 | 24369篇 |
1984年 | 20281篇 |
1983年 | 17745篇 |
1982年 | 14054篇 |
1981年 | 12686篇 |
1980年 | 12125篇 |
1979年 | 19731篇 |
1978年 | 15841篇 |
1977年 | 14425篇 |
1976年 | 13661篇 |
1975年 | 14893篇 |
1974年 | 15843篇 |
1973年 | 15556篇 |
1972年 | 14054篇 |
1971年 | 12988篇 |
1970年 | 11115篇 |
1969年 | 10616篇 |
1968年 | 9513篇 |
1967年 | 8531篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
851.
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
852.
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
853.
The phenotype of a ouabain-resistant Aedes albopictus cell line has been partially characterized. Treatment of ouabain-sensitive cells with 0.005-1.0 mM ouabain resulted in an 80% reduction in the uptake of 86rubidium (86Rb+), an ion with an affinity for the K+ pump binding site; ouabain-resistant cells showed only a 40% reduction with 1.0 mM ouabain. When ouabain-sensitive cells were incubated in the presence of ouabain (0.1 mM) for one and one-half to three hours, the molar ratio of intracellular Na+/K+ rose from 0.2 to 4.2. In ouabain-resistant cells, a similar treatment had very little effect. Based on [3H] ouabain-binding studies, ouabain-resistant cells were estimated to have 60% fewer binding sites per cell than ouabain-sensitive cells. The spontaneous mutation rate from ouabain sensitivity to ouabain resistance was calculated to be 1-6 x 10(-8) mutations/cell/generation, a value similar to that reported for mammalian cells at the analogous locus. 相似文献
854.
855.
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
856.
Energy-dispersive X-ray microanalysis of membrane-associated inclusions in hydrogenosomes isolated from Trichomonas vaginalis 总被引:1,自引:0,他引:1
Energy-dispersive X-ray microprobe analysis of electron-dense inclusions in hydrogenosomes isolated from the aerotolerant anaerobic protozoal human parasite Trichomonas vaginalis, Bushby strain, indicated the presence of high levels of Mg, P and Ca. This suggested that divalent cation (e.g. Ca2+ or Mg2+) accumulation by hydrogenosomes may be important in the regulation of intracellular ion concentrations. 相似文献
857.
858.
Differences in chemical composition of plants grown at constant relative growth rates with stable mineral nutrition 总被引:11,自引:0,他引:11
R. H. Waring A. J. S. McDonald S. Larsson T. Ericsson A. Wiren E. Arwidsson A. Ericsson T. Lohammar 《Oecologia》1985,66(2):157-160
Summary Leaf chemistry of a willow clone (Salix aquatica Smith) differed significantly when grown at constant relative growth rates depending upon the relative availability of nutrients and light. Concentration of amino acids and nitrate were high in plants grown with a relative surplus of nutrients. Concentrations of starch, tannin, and lignin, on the other hand, were high in plants grown with a relative surplus of carbon. Photosynthetic rates, expressed per unit leaf area, were similar when plants were grown under high light conditions, regardless of nutrient availability. Dark respiration was much higher in plants supplied with abundant nutrients than in those with a more limited supply, reflecting differences in nitrogen concentration of the tissue. The experimental approach allows plants to be grown to a standard size with differing, but highly uniform chemistry. Plants grown in such a manner may provide good experimental material to evaluate interactions between herbivores or pathogens and their hosts. 相似文献
859.
860.
Ultrasonographic assessment of the endometrium in rhesus monkeys during the normal menstrual cycle 总被引:1,自引:0,他引:1
This study was undertaken to determine whether cyclical changes in the endometrium of the rhesus monkey could be observed by using ultrasound. Three indices of endometrial size were examined: the antero-posterior (or ventro-dorsal), longitudinal, and transverse diameters. Changes in the ultrasonic reflectivity of the endometrium were also assessed. We have attempted to correlate these endometrial parameters with the hormonal status of the animal. Ultrasonography was performed for an average of 12 consecutive days during 19 menstrual cycles. All ultrasonic recordings were normalized to the day of the estradiol (E2) peak (Day 0). We found that the reflectivity of the endometrium was dependent on the stage of the cycle: during the follicular phase, the endometrium appeared less echogenic (darker) compared to the myometrium; in the luteal phase, the endometrium was more echogenic (lighter). During the follicular phase (Days -9 to 0), there was a linear increase in the antero-posterior (p less than 0.001), longitudinal (p less than 0.05), and transverse (p less than 0.001) diameters. In the luteal phase (Days 1-15), no significant changes were observed in these diameters. An estimated endometrial volume (EEV) was obtained by the product of the antero-posterior, longitudinal, and transverse diameters. Each animal observed during the follicular phase (n = 14) exhibited a peak in the EEV, which correlated with the day of the E2 peak (p less than 0.01). From this study, we conclude that the sonographic appearance of the endometrium of the rhesus monkey reflects the cyclical changes that occur during the menstrual cycle.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献