全文获取类型
收费全文 | 957769篇 |
免费 | 107056篇 |
国内免费 | 602篇 |
专业分类
1065427篇 |
出版年
2018年 | 8778篇 |
2017年 | 8327篇 |
2016年 | 11644篇 |
2015年 | 15445篇 |
2014年 | 18345篇 |
2013年 | 26359篇 |
2012年 | 29515篇 |
2011年 | 29954篇 |
2010年 | 20174篇 |
2009年 | 18710篇 |
2008年 | 26431篇 |
2007年 | 27371篇 |
2006年 | 25819篇 |
2005年 | 24871篇 |
2004年 | 24309篇 |
2003年 | 23440篇 |
2002年 | 22884篇 |
2001年 | 47456篇 |
2000年 | 47832篇 |
1999年 | 37187篇 |
1998年 | 12196篇 |
1997年 | 12845篇 |
1996年 | 12103篇 |
1995年 | 11179篇 |
1994年 | 10878篇 |
1993年 | 10880篇 |
1992年 | 30379篇 |
1991年 | 29476篇 |
1990年 | 28436篇 |
1989年 | 27687篇 |
1988年 | 25779篇 |
1987年 | 24129篇 |
1986年 | 22227篇 |
1985年 | 21999篇 |
1984年 | 18031篇 |
1983年 | 15498篇 |
1982年 | 11541篇 |
1981年 | 10346篇 |
1980年 | 9848篇 |
1979年 | 17129篇 |
1978年 | 13120篇 |
1977年 | 12113篇 |
1976年 | 10934篇 |
1975年 | 12331篇 |
1974年 | 13224篇 |
1973年 | 12902篇 |
1972年 | 11750篇 |
1971年 | 10617篇 |
1970年 | 9310篇 |
1969年 | 8867篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Degeneracy of antibody specificity 总被引:2,自引:0,他引:2
Evidence was obtained, by direct binding assays (radioimmunoassays) and by inhibition of binding assays, that after immunization some of the antibody molecules produced are degenerate in that they bind not only the immunizing antigen, but also unrelated ligands. It can be concluded that the exquisite specificity of the immune response is not necessarily a property of any given antibody molecule but is, at least to some extent, due to the summation of specificities held in common by the population of antibody molecules produced during the response. 相似文献
972.
Fusarium oxysporum f. sp. lycopersici and Rhizoctonal solani were grown in a complete 1.0 mM nutrient solution, and in solutions where Ca, Fe, K, Mg, N, P, and S were either excluded (0.0 mM) or included at depleted levels (0.1 mM) while all other constituents were maintained at 1.0 mM levels. Dry weight of both fungi were determined. For both fungi some of the lowest dry weights were recorded for samples grown in the complete solution. Exclusion of K, Mg, and S significantly increased dry weight of Fusarium. Inclusion at the 0.1 mM level of most components significantly increased Fusarium dry weight over values for both the complete and corresponding excluded nutrient solutions. The exception was S where there was no difference between excluded and 0.1 mM solutions. For Rhizoctonia dry weights in Fe excluded solutions were less than the complete solution, while dry weights in S excluded solutions were greater than the complete solution. At the 1.0 mM level Fe, K, and Mg dry weights were significantly increased over the dry weights produced in both the complete and deficient solutions. 相似文献
973.
S V Khabarov 《Biulleten' eksperimental'no? biologii i meditsiny》1987,103(6):715-717
Beta-adrenoceptors have been discovered on the surface of cells of leukaemia L1210 and its variant resistant to sarcolysine (D, L-melphalan). One type of functionally active receptors with dissociation constant Kd for L-[3H] dihydroalprenolol about 0.02 nM and 360 receptors per cell have been revealed in leukaemia L1210 cells. In the resistant cells two types of functionally inactive receptors with Kd1 approximately 0.02 nM (420 receptors per cell) and Kd2 approximately 2.5 nM (3000 receptors per cell) have been revealed. This property of beta-adrenoceptors may be one of the causes of tumour cell resistance to sarcolysine. 相似文献
974.
M.S. Blake K.H. Johnston G.J. Russell-Jones E.C. Gotschlich 《Analytical biochemistry》1984,136(1):175-179
A rapid, sensitive method has been developed to detect antibody-antigen complexes on “Western blots.” The methods of H. Towbin, T. Staehlin, and J. Gordon were used to separate and blot the antigens onto nitrocellulose. The remaining sites of attachment were blocked and the nitrocellulose was washed with polyoxyethylenesorbitan monolaurate (Tween 20). The blot was then reacted with the antiserum or hybridoma supernate to be tested. After the antigen-antibody reaction was completed, the blot was washed and treated with anti-antibody which has been conjugated to alkaline phosphatase. The alkaline phosphatase was detected by the reduction of the tetrazolium salt to diformazan by the hydrogen ions released in the formation of indigo by the reaction of the phosphatase on the indoxyl phosphate. The advantages of this method over previously described techniques are (1) use of Tween 20 allows the blot to be stained with Coomassie blue, (2) the substrates of the alkaline phosphatase reaction are stable for long periods of time, (3) the reaction products form an intense blue color which does not fade, (4) the resolution is extremely good with little to no band broadening, (5) the reaction is sensitive to picogram quantities of antigen, and (6) the reaction is quantitative. 相似文献
975.
976.
977.
New mutation affecting the synthesis of some membrane proteins and sporulation in Bacillus subtilis. 总被引:2,自引:1,他引:1 下载免费PDF全文
A new mutation, mpo, which affects the synthesis of some membrane proteins and sporulation in Bacillus subtilis was identified. The mpo mutation was tightly linked to the overproduction of membrane proteins MP32 and MP18 (molecular weights of 32,000 and 18,000, respectively) and the temperature-sensitive sporulation phenotype. Genetic analysis showed that the mpo mutation maps between the spoIIIB and lys loci. 相似文献
978.
979.
R Foa M T Fierro M Giovarelli P Lusso G Benetton M Bonferroni G Forni 《Blood cells》1987,12(2):399-412
Several phenotypic and functional defects have been described within the residual T-lymphocyte population of patients with B-cell chronic lymphocytic leukemia (B-CLL), particularly in those in the more advanced stages of the disease. In this study, we review these abnormalities and discuss their possible effects on the course of the illness. Particular emphasis is devoted to the role of interleukin 2 (IL-2) in B-CLL. Evidence is provided that the IL-2 released by B-CLL T-lymphocytes may be utilized by the neoplastic B-cell clone that expresses the IL-2 receptor and that decreased availability of IL-2 may play a contributory role in some of the T-cell defects encountered in B-CLL. 相似文献
980.
Studies on larval population densities and adult emergence rates of the Brugian filariasis vectors Mansonia bonneae Edwards and Ma. dives Schiner were conducted in freshwater swamp forest bordering the Sadong River, Serian District, Sarawak, East Malaysia, during 1984-85. Three species of aquatic host-plants in the Family Araceae were identified as supporting immature stages of the Ma. bonneae/dives complex. Proportions of positive plants were 4.7%, 6.5% and 3.4% with 6.4 +/- 2.6, 7.3 +/- 2.8 and 10.1 +/- 1.1 larvae per positive plant, respectively, for the plant species Homalomena cordata Schott, H. rostrata Griffiths and Hydrostemma motleyi (Hook. f.) Mabberley. These data indicate no significant preferences between the three types of host-plant. Detailed monitoring of the host-plant H. cordata revealed no significant monthly fluctuations in larval density per plant nor the proportion of positive plants. 11.6% of larvae were Ma. dives and 88.4% were Ma. bonneae. Mean daily yields of Ma. bonneae/dives adults per square metre of H. cordata vegetated water surface were 0.45 males plus 0.57 females during the wet season (December-February) compared with 0.2 males plus 0.31 females during the dry season (June-August). Thus output of adults per plant was approximately halved, and suitable breeding areas were further reduced, during the dry season. By extrapolation from these rates, a crude mean estimate for productivity of Ma. bonneae/dives females is 1.6 million per hectare per annum in swamp forest habitats vegetated with any of the host-plants studied. 相似文献