全文获取类型
收费全文 | 158400篇 |
免费 | 5752篇 |
国内免费 | 911篇 |
专业分类
165063篇 |
出版年
2022年 | 453篇 |
2021年 | 925篇 |
2020年 | 590篇 |
2019年 | 698篇 |
2018年 | 12511篇 |
2017年 | 11326篇 |
2016年 | 8762篇 |
2015年 | 3180篇 |
2014年 | 3047篇 |
2013年 | 3982篇 |
2012年 | 8772篇 |
2011年 | 17120篇 |
2010年 | 14716篇 |
2009年 | 10718篇 |
2008年 | 13413篇 |
2007年 | 14991篇 |
2006年 | 4015篇 |
2005年 | 4279篇 |
2004年 | 4681篇 |
2003年 | 4512篇 |
2002年 | 4240篇 |
2001年 | 1039篇 |
2000年 | 752篇 |
1999年 | 860篇 |
1998年 | 991篇 |
1997年 | 713篇 |
1996年 | 691篇 |
1995年 | 691篇 |
1994年 | 678篇 |
1993年 | 721篇 |
1992年 | 636篇 |
1991年 | 592篇 |
1990年 | 461篇 |
1989年 | 472篇 |
1988年 | 477篇 |
1987年 | 419篇 |
1986年 | 392篇 |
1985年 | 469篇 |
1984年 | 534篇 |
1983年 | 448篇 |
1982年 | 546篇 |
1981年 | 485篇 |
1980年 | 427篇 |
1979年 | 291篇 |
1978年 | 342篇 |
1977年 | 331篇 |
1976年 | 270篇 |
1974年 | 277篇 |
1972年 | 409篇 |
1971年 | 434篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
Peter J. Robinson Michael Steinmetz Kazuo Moriwaki Kirsten Fischer Lindahl 《Immunogenetics》1984,20(6):655-665
To determine the distribution of beta-2 microglobulin (B2m) alleles in wild mice we have typed mice derived from natural populations in Europe, North Africa, South America, and East Asia. Mus musculus domesticus mice from Germany, France, Italy, and Peru were all B2m
a
as were most from the United Kingdom. M.m. musculus mice from Denmark and Czechoslovakia, several stocks of M.m. molossinus from Japan, and M.m. castaneus from China, Thailand, and the Philippines were of B2m
b
type. This is consistent with the notion that C57BL/6 may have obtained some of its genes, including B2m, from Eastern mice. A BgII restriction site characteristic of B2m
b
was also found in mice from Czechoslovakia and Japan, confirming that B2m
b
is a naturally occurring allele of B2m. A new type of
2m (
2mw1) was found in four stocks of M. spretus from Portugal, Spain, and Morocco. This molecule differs in apparent size and charge from the a and b types.
2mw2 was found together with
2 ma in one stock of M.m. domesticus (brevirostris) from Morocco.
2mw3 and
2mw4 were found in a few M. m. bactrianus from Pakistan. In all cases tested, these new
2m molecules associate with class I histocompatibility antigens.Abbreviations used in this paper
2m
beta-2 microglobulin
-
B2m
gene for beta-2 microglobulin
- IEF
isoelectric focusing
- SDS-PAGE
polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate
- MHC
major histocompatibility complex
- T. E.
Tris-EDTA buffer 相似文献
973.
Peter H. OBrien 《Applied animal behaviour science》1984,12(4):373-385
The daily range of feral goats varied in relation to social class and environmental variables. Mean daily ranges for 5 social classes were: male herd, 3.52 × 105 m2; female herd, 2.12 × 105 m2; composite herd, 1.86 × 105 m2; stayer female, 0.57 × 105 m2; creche group, 0.39 × 105 m2. Total recorded home range was male herd 14.8 × 105 m2 and female herd 9.65 × 105 m2. Female herd daily range varied seasonally in terms of size, location and habitat utilization. Female herd daily range area was correlated significantly with number of days since rain (r = 0.412), amount of rain in the past 30 days (r = ?0.296), maximum daily temperature (r = ?0.409), and minimum daily temperature (r = ?0.523), but not with wind velocity in the morning (r = ?0.064) or afternoon (r = ?0.137). 相似文献
974.
975.
Everett Anderson Peter C. Hoppe Gloria S. Lee 《Molecular reproduction and development》1984,9(4):451-467
Karyotypic and light and electron microscopical analyses were made of spontaneous preimplantation mouse parthenotes from the LT/Sv inbred strain. It was found that the activated oocyte and developing embryos were diploid. We believe that diploidization is achieved by the oogonium undergoing a premeiotic mitosis without cytokinesis followed by two meiotic divisions, thus producing diploid parthenotes. The developmental events with respect to membrane specialization, such as junctional complexes, were similar to those observed in fertilized embryos. A unique feature of the developing parthenote was the failure of the mitochondria to change during the morula stage. The mitochondria retained a few irregularly oriented cristae rather than many transversely oriented ones observed in morulae developing from fertilized eggs. The significance of this observation is discussed. 相似文献
976.
To avoid intracellular freezing and its usually lethal consequences, cells must lose their freezable water before reaching their ice-nucleation temperature. One major factor determining the rate of water loss in the temperature dependence of the water permeability,L p (hydraulic conductivity). Because of the paucity of water permeability measurements at subzero temperatures, that temperature dependence has usually been extrapolated from above-zero measurements. The extrapolation has often been based on an exponential dependence ofL p on temperature. This paper compares the kinetics of water loss based on that extrapolation with that based on an Arrhenius relation betweenL p and temperature, and finds substantial differences below ?20 to ?25°C. Since the ice-nucleation temperature of mouse ova in the cryoprotectants DMSO and glycerol is usually below ?30°C, the Arrhenius form of the water-loss equation was used to compute the extent of supercooling in ova cooled at rates between 1 and 8°C/min and the consequent likelihood of intracellular freezing. The predicted likelihood agrees well with that previously observed. The water-loss equation was also used to compute the volumes of ova as a function of cooling rate and temperature. The computed cell volumes agree qualitatively with previously observed volumes, but differ quantitatively. 相似文献
977.
Peter Singer Manfred Wirth Ute Gerike Wolfgang Gdicke Vera Moritz 《Prostaglandins & other lipid mediators》1984,27(3):375-390
The lipid content as well as the fatty acid pattern of triglycerides, free fatty acids (FFA), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were estimated in renal cortex and medulla of spontaneously hypertensive rats (SHR) and normotensive Wistar rats (WR) at 4,8,26 and 52 weeks of age. In general, the level of triglycerides in renal medulla appeared higher when compared with the cortex. On the other hand, PC and PE, increasing with age, were usually higher in the cortex. A decreased percentage of linoleic acid (LA) in triglycerides, of arachidonic acid (AA) in PC and of eicosapentaenoic acid (EPA) in triglycerides, FFA, PC and PE could be found in the kidneys of SHR at 8 weeks of age, i.e. during the development of hypertension. This was accompanied with a rise of AA in FFA of SHR at 8 weeks of age, which occurred with delay in WR (at 26 weeks of age). From the data presented it can be concluded that systematic alterations in the availability of individual polyunsaturated fatty acids (PUFA) in various renal lipids might be related to the onset of hypertension in SHR which should be elucidated in more detail. 相似文献
978.
979.
980.
In the presence of Cl?, the severity of ammonia-induced inhibition of photosynthetic oxygen evolution is attenuated in spinach thylakoid membranes (Sandusky, P.O. and Yocum, C.F. (1983) FEBS Lett. 162, 339–343). A further examination of this phenomenon using steady-state kinetic analysis suggests that there are two sites of ammonia attack, only one of which is protected by the presence of Cl?. In the case of Tris-induced inhibition of oxygen evolution only the Cl? protected site is evident. In both cases the mechanism of Cl? protection involves the binding of Cl? in competition with the inhibitory amine. Anions (Br? and NO?3) known to reactive oxygen evolution in Cl?-depleted membranes also protect against Tris-induced inhibition, and reactivation of Cl?-depleted membranes by Cl? is competitively inhibited by ammonia. Inactivation of the oxygen-evolving complex by NH2OH is impeded by Cl?, whereas Cl? does not affect the inhibition induced by so-called ADRY reagents. We propose that Cl? functions in the oxygen-evolving complex as a ligand bridging manganese atoms to mediate electron transfer. This model accounts both for the well known Cl? requirement of oxygen evolution, and for the inhibitory effects of amines on this reaction. 相似文献