全文获取类型
收费全文 | 2184篇 |
免费 | 269篇 |
国内免费 | 3篇 |
出版年
2021年 | 18篇 |
2019年 | 19篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 57篇 |
2014年 | 67篇 |
2013年 | 105篇 |
2012年 | 118篇 |
2011年 | 86篇 |
2010年 | 55篇 |
2009年 | 57篇 |
2008年 | 90篇 |
2007年 | 91篇 |
2006年 | 80篇 |
2005年 | 85篇 |
2004年 | 71篇 |
2003年 | 74篇 |
2002年 | 66篇 |
2001年 | 77篇 |
2000年 | 74篇 |
1999年 | 85篇 |
1998年 | 34篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 33篇 |
1994年 | 19篇 |
1993年 | 31篇 |
1992年 | 55篇 |
1991年 | 52篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 34篇 |
1987年 | 41篇 |
1986年 | 35篇 |
1985年 | 28篇 |
1984年 | 26篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1979年 | 32篇 |
1978年 | 36篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 31篇 |
1974年 | 17篇 |
1973年 | 33篇 |
1971年 | 25篇 |
1968年 | 15篇 |
1967年 | 22篇 |
排序方式: 共有2456条查询结果,搜索用时 31 毫秒
91.
Infection of a continuous cell line of dog kidney origin (MDCK) with herpes simplex virus type 2 (HSV-2) resulted in production of little to no new infectious virus. Serial subculture of MDCK cells inoculated with HSV-2 did not permit establishment of carrier cell cultures, as assessed by negative results of plaque assays for infectious virus and radioimmunoassay (RIA) for viral antigens. Group- and type-specific antigens were detected in lysates of non-permissive MDCK cells inoculated with HSV-2 and tested by RIA at 24 hours post-inoculation. Polypeptides produced in permissive (Vero) and non-permissive (MDCK) cell systems were labeled with [14C]-amino acids and analyzed by polyacrylamide slab gel electrophoresis and autoradiography. During non-permissive infection, two polypeptides of large molecular weight, not found in uninfected MDCK cells, one of which commigrated with a major HSV-2 structural polypeptide, were synthesized and reproducibly detected. 相似文献
92.
Lanosterol and cycloartenol labelled with tritium at C-2, and 24-methylenecholesterol and fucosterol labelled with tritium at C-2 and C-4 were fed to actively growing cultures of Chlorella ellipsoidea. Lanosterol and cycloartenol were converted to each of the five desmethyl sterols of C. ellipsoidea. Lanosterol was more efficiently incorporated than cycloartenol.Although there was some evidence for the reduction of the 24-methylene group, it was apparent that 24-methylene-cholesterol was converted primarily to the C29 sterols, clionasterol and poriferasterol. Labelled fucosterol was reduced at the 24(28) double bond, producing clionasterol. 相似文献
93.
When Chlorella sorokiniana was grown in the presence of 4 ppm AY-9944 total sterol production was unaltered in comparison to control cultures. However, inhibition of sterol biosynthesis was shown by the accumulation of a number of sterols which were considered to be intermediates in sterol biosynthesis. The sterols which were found in treated cultures were identified as cyclolaudenol, 4α,14α-dimethyl-9β,19-cyclo-5α-ergost-25-en-3β-ol, 4α,14α-dimethyl -5α-ergosta-8,25-dien-3β-ol, 14α-methyl-9β,19-cyclo-5α-ergost-25-en-3β-ol, 24-methylpollinastanol, 14α-methyl-5α-ergost-8-en-3β-ol, 5α-ergost -8(14)-enol, 5α-ergost-8-enol, 5α-ergosta-8(14),22-dienol, 5α-ergosta-8,22-dienol, 5α-ergosta-8,14-dienol, and 5α-ergosta-7,22-dienol, in addition to the normally occurring sterols which are ergosterol, 5α-ergost-7-enol, and ergosta-5,7-dienol.The occurrence of these sterols in the treated culture indicates that AY-9944 is an effective inhibitor of the Δ8 → Δ7 isomerase and Δ14-reductase, and also inhibits introduction of the Δ22-double bond. The occurrence of 14α-dimethyl-5α-ergosta-8,25-dien-3β-ol and 14α-methyl-9β,19-cyclo-5α-ergost -25-en-3β-ol is reported for the first time in living organisms. The presence of 25-methylene sterols suggests that they, and not 24-methylene derivatives, are intermediates in the biosynthesis of sterols in C. sorokiniana. 相似文献
94.
W H Eschenfeldt R J Patterson 《Biochemical and biophysical research communications》1975,67(3):935-945
Specific binding of antibody directed against MOPC-21 myeloma protein to MOPC-21 polysomes has been demonstrated. It was also shown that this same antibody bound specifically to the ribosomal subunits of these polysomes, suggesting that the antibody is not binding exclusively to the nascent polypeptide chains on the polysomes. The antibody was bound specifically to polysomes of a nonproducing variant XC1 which had been isolated in the presence of MOPC-21 myeloma protein while the antibody was not bound to XC1 polysomes isolated in the absence of myeloma protein. This suggests that the myeloma protein is adsorbed to the polysomes during the isolation procedure. 相似文献
95.
J E Levasseur H A Kontos D W Richardson J L Patterson 《Journal of applied physiology》1976,40(4):549-558
Five chronically instrumented healthy dogs were exposed to a 5-day period of breathing 10% oxygen in a chamber. The response to hypoxia was found to be time dependent. During the first 24 h of hypoxia the circulatory response was characterized by increases in cardiac output, heart rate, pulmonary and systemic arterial blood pressures, and pulmonary vascular resistance. Systemic vascular resistance increased; left atrial pressure decreased. During the early part of hypoxia the animals became hypocapnic; the arterial blood pH rose significantly. During the rest of the hypoxic period cardiac output, heart rate, and arterial blood pH returned to the control values; pulmonary and systemic arterial pressures and pulmonary vascular resistance remained significantly elevated. Systemic vascular resistance rose; left atrial pressure remained below control. This response to hypoxia was not substantially modified when the experiment was repeated during the administration of the antihistamine promethazine, an H1-receptor blocking agent, in a dose which blocked the pulmonary vasoconstrictor response to small doses of exogenous histamine. The circulatory response to acute hypoxia in five anesthetized dogs was not modified by intravenous administration of metiamide, an H2-receptor blocking agent. 相似文献
96.
Ruck's componental analysis of the ocellar electroretinogram (ERG) has been reappraised using techniques of signal averaging and waveform subtraction. Components (1), (3), and (4) can readily be isolated in the locust ocellus but component (2) as recorded in the locust ocellus is probably an artefact. Component (1), produced by the receptor cells, only contributes significantly to the total ERG at higher light intensities and it is this contribution which changes most with the degree of light and dark adaptation employed in these experiments. Component (3), the response of the second-order neurones, indicates that the majority of second-order neurones hyperpolarize on illumination of the ocellus. Component (4), the afferent activity of the second-order cells, indicates that more than one afferent axon is involved in the production of off spikes in the locust ocellus. 相似文献
97.
SPINAL CORD LIPIDS AND MYELIN COMPOSITION IN BORDER DISEASE (HYPOMYELINOGENESIS CONGENITA) OF LAMBS 总被引:1,自引:1,他引:0
D. S. P. Patterson S. Terlecki J. A. Foulkes D. Sweasey E. M. Glancy 《Journal of neurochemistry》1975,24(3):513-522
Spinal cords from clinically affected newborn lambs, each with muscular spasms (‘shaking’) and a ‘hairy’ birth coat, were found to be deficient in DNA and to contain less myelin and various lipid components, suggesting retarded CNS development equivalent to about 124 days conceptual age. Cerebrosides were notably deficient in whole cord and isolated myelin and contained more saturated and less unsaturated fatty acids than normal. The rate of cerebroside synthesis assayed in vitro was enhanced and taken with the very low tissue concentrations this indicated faster cerebroside turnover and a less stable myelin in the spinal cords of lambs affected with Border Disease. Marked decreases in plasmalogen concentrations, the redistribution of phospholipid fractions, the presence of about 8 per cent cholesterol in the esterified form and the characteristic fatty acid composition of these esters strongly suggest that degeneration is concomitant with myelin immaturity. Hypocupraemia, low concentrations of copper in the cerebrum and increased concentrations in spinal cord myelin are additional features of the clinical disease. The latter result may be related to myelin immaturity. 相似文献
98.
99.
100.