全文获取类型
收费全文 | 5052篇 |
免费 | 524篇 |
出版年
2022年 | 40篇 |
2021年 | 102篇 |
2020年 | 50篇 |
2019年 | 55篇 |
2018年 | 79篇 |
2017年 | 58篇 |
2016年 | 110篇 |
2015年 | 196篇 |
2014年 | 230篇 |
2013年 | 267篇 |
2012年 | 339篇 |
2011年 | 376篇 |
2010年 | 236篇 |
2009年 | 212篇 |
2008年 | 288篇 |
2007年 | 303篇 |
2006年 | 239篇 |
2005年 | 276篇 |
2004年 | 261篇 |
2003年 | 253篇 |
2002年 | 266篇 |
2001年 | 71篇 |
2000年 | 54篇 |
1999年 | 81篇 |
1998年 | 84篇 |
1997年 | 57篇 |
1996年 | 43篇 |
1995年 | 42篇 |
1994年 | 52篇 |
1993年 | 59篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 62篇 |
1989年 | 38篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 33篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1978年 | 23篇 |
1977年 | 31篇 |
1976年 | 31篇 |
1975年 | 27篇 |
1974年 | 26篇 |
1973年 | 31篇 |
1972年 | 24篇 |
排序方式: 共有5576条查询结果,搜索用时 156 毫秒
131.
132.
The binding of soybean agglutinin to human and rabbit erythrocytes, before and after treatment with trypsin, was reinvestigated with special emphasis on measurements at very low lectin concentrations. This communication presents two features of the binding that are observed only at the low concentrations used. (1) The trypsinized erythrocytes bind more lectin molecules than untreated cells at low concentrations (0.1–1.0 μg/ml), even though the total number of binding sites appears to be the same for both treated and untreated cells. It is suggested that this difference could explain, at least in part, the much higher susceptibility of the trypsin-treated cells to agglutination by soybean agglutinin. (2) At low site occupancy the binding of soybean agglutinin exhibits positive cooperativity, indicating a conformational change in the membrane. Trypsin-treated cells exhibit this effect at much lower lectin concentrations than untreated cells. 相似文献
133.
Robert Belmaker Helmut Beckmann Frederick Goodwin Dennis Murphy William Pollin Monte Buchsbaum Richard Wyatt Roland Ciaranello Friedhelm Lamprecht 《Life sciences》1975,16(2):273-279
The activity of dopamine-B-hydroxylase in blood has recently been demonstrated to be under genetic control and to correlate closely with urinary catecholamine excretion. The results of the present study did not demonstrate any relationship between a major catecholamine metabolite in urine, 3-methoxy-4-hydroxy phenylglycol, and dopamine-B-hydroxylase activity in plasma, monoamine oxidase activity in platelets, or monoamine oxidase activity in plasma. Differences in the origin of urinary catecholamines and urinary 3-methoxy-4-hydroxy phenyglycol may be responsible for these divergent results. 相似文献
134.
—A mass fragmentographic procedure is described for the simultaneous quantification of a number of deaminated metabolites derived from tyramine, octopamine, dopamine, and norepinephrine. With this method, several of the metabolites were measured in normal rat brain. The results support the central nervous system origin of tyramine, octopamine and their metabolites. The concentration of the dopamine metabolite, homovanillic acid, in the rat brain was found to be about 15% higher than that of dihydroxyphenylacetic acid. As for the metabolites of norepinephrine, vanilmandelic acid concentration was found to be about 5% that of 3-methoxy-4-hydroxyphenylglycol. The possible role of vanilmandelic acid in the CNS metabolism of norephrine is discussed. 相似文献
135.
Severe infection with Eimeria acervulina, Eimeria maxima, Eimeria necatrix, and Eimeria tenella increased the prothrombin times in broilers compared with the times in uninfected birds. Recalcification time was not affected. The increase in prothrombin time was related to the severity of infection (as measured by lesion score), and was significant (P less than or equal to 0.05) only in the most severely infected birds. The increase was of short duration, lasting only 1 or 2 days, and first appeared on day 5 or 6 postinoculation. Restricting the feed intake of uninoculated birds to the amount of feed consumed by infected birds showed that the reduction in feed intake with coccidiosis was not responsible for the increase in prothrombin time. 相似文献
136.
137.
Profiling of apoptotic changes in human breast cancer cells using SELDI-TOF mass spectrometry. 总被引:2,自引:0,他引:2
Sharon Leong Richard I Christopherson Robert C Baxter 《Cellular physiology and biochemistry》2007,20(5):579-590
Apoptosis is a key process in the response of tumours to chemotherapeutic agents. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in many tumor cells, while sparing most normal cells. Several chemotherapeutic drugs synergize with TRAIL in reducing tumor growth and inducing apoptosis. Because some tumour cells respond poorly to these treatments, biomarkers that predict clinical responsiveness are needed. This study used surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to identify novel apoptotic markers in TRAIL and etoposide (T+E)-treated MDA-MB-231 and ZR-75-1 breast cancer cells and MCF-10A non-transformed breast cells. T+E induced apoptosis, increasing caspase-3 activity at 4-8h, in all cell lines. Protein profiles revealed two prominent peaks, m/z 10090 and 8560, which decreased significantly during apoptosis. Mass spectrometry sequencing of tryptic peptides identified these proteins as S100A6 (confirmed immunologically) and ubiquitin (confirmed against a purified standard), respectively. Caspase inhibition prevented the decrease in both proteins during T+E-induced apoptosis whereas proteasome inhibition combined with T+E further decreased ubiquitin, possibly by preventing its recycling. Using SELDI-TOF MS we have identified S100A6 and ubiquitin as potential protein markers of apoptosis. Further validation using patient samples is required to confirm their potential utility in monitoring the effectiveness of anti-cancer drugs in inducing tumour cell apoptosis. 相似文献
138.
Wu Changwei W. Tsai Pei-Jung Chen Sharon Chia-Ju Li Chia-Wei Hsu Ai-Ling Wu Hong-Yi Ko Yu-Ting Hung Pai-Chuan Chang Chun-Yen Lin Ching-Po Lane Timothy J. Chen Chia-Yuen 《Sleep and biological rhythms》2019,17(4):423-431
Sleep and Biological Rhythms - Neurovascular coupling (NVC), the transient regional hyperemia following the evoked neuronal responses, is the basis of blood oxygenation level-dependent techniques... 相似文献
139.
Subregional variability in the response of New England vegetation to postglacial climate change
下载免费PDF全文
![点击此处可从《Journal of Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
140.