全文获取类型
收费全文 | 223993篇 |
免费 | 14986篇 |
国内免费 | 49篇 |
专业分类
239028篇 |
出版年
2021年 | 1774篇 |
2018年 | 3126篇 |
2017年 | 3024篇 |
2016年 | 3666篇 |
2015年 | 3201篇 |
2014年 | 4439篇 |
2013年 | 6324篇 |
2012年 | 7544篇 |
2011年 | 8063篇 |
2010年 | 5721篇 |
2009年 | 4878篇 |
2008年 | 7197篇 |
2007年 | 7479篇 |
2006年 | 7179篇 |
2005年 | 6705篇 |
2004年 | 6849篇 |
2003年 | 6568篇 |
2002年 | 6524篇 |
2001年 | 9274篇 |
2000年 | 8954篇 |
1999年 | 6987篇 |
1998年 | 2123篇 |
1997年 | 1953篇 |
1996年 | 1819篇 |
1992年 | 5467篇 |
1991年 | 5679篇 |
1990年 | 5650篇 |
1989年 | 5622篇 |
1988年 | 5212篇 |
1987年 | 4862篇 |
1986年 | 4443篇 |
1985年 | 4678篇 |
1984年 | 3697篇 |
1983年 | 3025篇 |
1982年 | 2013篇 |
1981年 | 1723篇 |
1980年 | 1725篇 |
1979年 | 3342篇 |
1978年 | 2577篇 |
1977年 | 2376篇 |
1976年 | 2330篇 |
1975年 | 2826篇 |
1974年 | 3118篇 |
1973年 | 3087篇 |
1972年 | 2746篇 |
1971年 | 2604篇 |
1970年 | 2212篇 |
1969年 | 2158篇 |
1968年 | 2031篇 |
1967年 | 1797篇 |
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
881.
T P Kliushnik S G Voloshchuk M V Aksenova G Sh Burbaeva 《Biulleten' eksperimental'no? biologii i meditsiny》1985,99(2):179-180
IEA of brain specific antigen 10-40-4 in human and animal organs and tissues was elaborated. The method permits measuring the concentration of the antigen within the range from 1 to 120 ng/ml. The use of the method made it possible to confirm brain specificity of protein 10-40-4, since its brain content is 1500 to 2000 times higher than in other organs, and to estimate the percentage of cross-reaction between antigenic determinants of brain specific antigen 10-40-4 from different species of animals. 相似文献
882.
In shigellosis caused by Sh. sonnei and Sh. flexneri the epidemic process was found to have considerable difference in the tendencies and pace of its development. Shigellosis which dominated in the etiological structure at the period following 1966 was dysentery caused by Sh. sonnei; it showed the tendency towards a decrease in morbidity rate. Dysentery caused by Sh. flexneri was second in respect to the frequency of its occurrence after 1966 and showed the tendency towards increase. The simultaneous circulation of Sh. sonnei and Sh. flexneri, the differences in the epidemiology of these types of shigellosis make it imperative that they be studied separately, taking into ccount their etiological selectivity to the main routes of transmitting the infection. 相似文献
883.
884.
885.
V. A. Zhukov 《Neurophysiology》1980,12(1):60-68
The position of on- and off-discharge centers in class 1 and 3 receptive fields of the frog retina was determined with the aid of moving bars of different lengths. On- and off-centers of receptive fields of the first group coincide, those of the second are spatially separate, and in fields of the 3rd group the discharge center of one contrast sign occupies the central position and discharge centers of the opposite sign are located at the periphery, to its right and left. Receptive fields of the frog retina thus have features which approximate them to the concentric receptive fields of geniculate neurons and the fields of the cat visual cortex. Asymmetry in the responses was found: during movement in opposite directions the distance between the discharge centers changed, during movement to one side only one of the peripheral centers was revealed, whereas during movement to the other side the second center was revealed on the opposite side of the receptive field. This asymmetry of spatiotemporal relations in the receptive fields is similar to that found in the fields of cortical neurons and is connected with their directional properties.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gor'kii. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 75–85, January–February, 1980. 相似文献
886.
BRYANT SUSAN V.; HOLDER NIGEL; TANK PATRICK W. 《Integrative and comparative biology》1982,22(1):143-151
SYNOPSIS. A current model concerning the process of limb regenerationin vertebrates is examined. According to this model (Bryantet al, 1981), new positional values in the proximal-distal limbaxis are laid down as a result of local interactions betweencells in the limb circumference. Cells with disparate circumferentialpositional values come together at the site of future outgrowthand intercalation between them generates more distal levelsof the pattern. The results of a number of experiments on surgicallycreated symmetrical limb stumps are discussed in relation tothis model. In addition, an extension of this model to accountfor digit formation is presented, and the implications of thisformulation for limb evolution are discussed. 相似文献
887.
A. V. Bazhin E. N. Grigoryan N. K. Tikhomirova V. A. Poplinskaya P. P. Filippov 《Biology Bulletin》2002,29(4):348-355
The presence and localization of the calcium-binding protein recoverin, initially found in photoreceptors of the bovine eye, were immunochemically studied in retina of the new Pleurodeles waltl. Polyclonal monospecific antibodies against recoverin were raised and the methods of immunoblotting and indirect immunofluorescence were used. A protein with an apparent molecular mass of 26 kDa was found in the retina extract, which was specifically stained by the antibodies against recoverin. Localization of recoverin was studied on the retina sections: an intense reaction was found in the inner segments and a weak reaction was found in the basal part of the outer segments of photoreceptors and in Landolt's clubs of displaced bipolars. The results we obtained suggest for the first time the presence of recoverin in the retina of a representative of the Urodeles and indicate to interspecific conservativeness of this protein and differences of its localization in the retina photoreceptors in different species. The data obtained open a possibility of using recoverin as a marker protein of photoreceptors and displaced bipolars in studies of retina regeneration in newts. 相似文献
888.
V V Vysotski? I Sh Vaisman O G Efimova N V Chemurzieva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(9):54-60
The characteristic feature of replicas obtained from the freeze-fractures of B. pertussis unfixed cultures developing on casein charcoal agar for 1-7 days is the associative growth of highly polymorphic cells, ensured by the ramified system of intercellular connections (IC) formed by the derivatives of the outer layers of the cell wall. This proves that the associative location of bacterial cells, linked by numerous IC, in the preparation is not the artefact appearing in the process of their chemical fixation. In replicas obtained from the freeze-fractures of B. pertussis cultures, previously fixed with glutaraldehyde, osmic acid and uranyl acetate, oval cells with the cytoplasm having a relatively homogeneous structure and with the smoothed-out three-layer cell wall prevail. As a rule, IC are limited to the sites of direct contacts between individual cells. 相似文献
889.
890.
Six new antigenic specificities (designated SLB-2 to SLB-7) detectable with polyclonal reagents in the complement-dependent lymphocytotoxic test were determined in the SLB alloantigenic system of pigs. The SLB specificities (including the previously described SLB-1) are controlled by 13 alleles. An analysis of a further 121 double backcross matings (with 817 offspring) confirmed that the products of SLB alleles segregated independently of the SLA haplotypes (swine MHC). In addition, in 112 families of the same mating type (with 746 progeny) the map distance of the SLB locus and the highly polymorphic L blood group locus was found to be 7.82 centimorgans in the heterogametic sex and 12.57 centimorgans in the homogametic sex. 相似文献