全文获取类型
收费全文 | 770529篇 |
免费 | 87731篇 |
国内免费 | 871篇 |
出版年
2018年 | 6871篇 |
2017年 | 6775篇 |
2016年 | 9396篇 |
2015年 | 13131篇 |
2014年 | 15249篇 |
2013年 | 21612篇 |
2012年 | 24904篇 |
2011年 | 25451篇 |
2010年 | 16978篇 |
2009年 | 15636篇 |
2008年 | 22711篇 |
2007年 | 23221篇 |
2006年 | 22027篇 |
2005年 | 20993篇 |
2004年 | 20944篇 |
2003年 | 19899篇 |
2002年 | 19353篇 |
2001年 | 32991篇 |
2000年 | 33175篇 |
1999年 | 26768篇 |
1998年 | 9966篇 |
1997年 | 10141篇 |
1996年 | 9775篇 |
1995年 | 9064篇 |
1994年 | 8984篇 |
1993年 | 8877篇 |
1992年 | 22523篇 |
1991年 | 22080篇 |
1990年 | 21701篇 |
1989年 | 21295篇 |
1988年 | 19598篇 |
1987年 | 18605篇 |
1986年 | 17534篇 |
1985年 | 17457篇 |
1984年 | 14336篇 |
1983年 | 12487篇 |
1982年 | 9521篇 |
1981年 | 8549篇 |
1980年 | 8102篇 |
1979年 | 13694篇 |
1978年 | 10851篇 |
1977年 | 9754篇 |
1976年 | 9286篇 |
1975年 | 10373篇 |
1974年 | 11096篇 |
1973年 | 10904篇 |
1972年 | 9822篇 |
1971年 | 8909篇 |
1970年 | 7679篇 |
1969年 | 7350篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
941.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells. 相似文献
942.
Fire has historically been an important ecological component of forests in the Intermountain Region of the northwestern United States. This study is set in a small biogeographically disjunct mountain range. Our research objectives were to (1) investigate the historical frequency, severity, size, and spatial pattern of fire; (2) determine if and how fire regimes have changed since Euro-American settlement; and (3) compare how fire regimes of a small isolated range compare to nearby, but considerably larger, mountain agglomerations. Our findings suggest that this mountain range has historically supported fires typified by small size and high frequency, resulting in a high degree of spatial pattern complexity compared to mountain agglomerations. We also found disparity in size and burn severity solely within the study area based on the bisecting Continental Divide. Since the advent of Euro-American settlement in the 1870s, fire frequency and sizes of individual fires in the West Big Hole Range have significantly decreased resulting in an estimated 87% reduction in area burned. We discuss potential relationships of mountain range isolation and fire regimes in the Intermountain Region. Furthermore, we suggest that the relative small size of this mountain range predisposes it to greater anthropogenic effects upon fire occurrence. 相似文献
943.
944.
945.
C K?nig Y L Yan J Postlethwait S Wendler J A Campos-Ortega 《Mechanisms of development》1999,86(1-2):17-28
We describe the characterization of the zebrafish homologue of the human gene DLG3. The zebrafish dlg3 gene encodes a membrane-associated guanylate kinase containing a single PDZ domain. This gene was cloned using a gene-trap construct inserted in the gene's first intron. The insertion co-segregates with a viable mutation called humpback (hmp), which leads to formation of ankylotic vertebrae in adult fishes. Insertion and mutation have both been mapped to chromosome 12, in a segment which is syntenic with region p12 to q12 of human chromosome 17. The hmp mutant phenotype, however, appears to be due to two point mutations in the guanylate kinase domain rather than to the transgene insertion itself. The results of this study are discussed in the light of the possible function of the guanylate kinase domain. 相似文献
946.
R G Pankov A A Uschewa B T Tasheva P T Petrov G G Markov 《Cell biology international reports》1985,9(11):1003-1011
A dominating protein fraction (p45) having molecular weight of 45000 and pI 5.45 was found in the intermediate filaments pellet obtained from rat liver besides the present cytokeratins. Peptide mapping and radioimmunological assays with antibodies against this protein and muscle actin proved that the p45 protein belongs to the actin group. Immunoelectron microscopy revealed that this protein is located on the liver intermediate filaments. By melting of the cytokeratin complexes in urea it was established that p45 protein is complexed with the low molecular weight cytokeratin. 相似文献
947.
A strain of 1,507 typised donors enables 15.97 average donors to be selected for a thrombocyte transfusion in one of 75 patients selected at random with HLA antibodies being previously determined (1 to 66 donors per patient). HLA compatible donors were found for 72 patients (97.33 per cent). More than 5 HLA compatible donors could be found for 58 patients. The high number of compatible donors is based on the fact that among 1,507 donors there were 156 HLA homozygotes and 556 donors with 3 HLA-A or B-antigens respectively. Compatibility in the ABO-system was not taken into account. 相似文献
948.
Synthesis of intrathecal interferon in systemic lupus erythematosus with neurological complications.
Intrathecal synthesis of interferon in the absence of viral or bacterial infection was detected during the occurrence of neurological complications in two patients with systemic lupus erythematosus. The interferons displayed characteristics similar to those observed in the sera of patients with the disease. No interferon inducing activity was detected in the cerebrospinal fluid or serum of the two patients. These observations support the hypothesis of a localised mechanism of interferon induction in systemic lupus erythematosus which includes the interaction of lymphocytes with damaged tissues. 相似文献
949.
950.