全文获取类型
收费全文 | 96747篇 |
免费 | 7060篇 |
国内免费 | 149篇 |
专业分类
103956篇 |
出版年
2023年 | 462篇 |
2022年 | 588篇 |
2021年 | 1227篇 |
2020年 | 952篇 |
2019年 | 1155篇 |
2018年 | 1901篇 |
2017年 | 1786篇 |
2016年 | 2568篇 |
2015年 | 3751篇 |
2014年 | 4067篇 |
2013年 | 5177篇 |
2012年 | 6320篇 |
2011年 | 5869篇 |
2010年 | 3763篇 |
2009年 | 3211篇 |
2008年 | 4816篇 |
2007年 | 4764篇 |
2006年 | 4479篇 |
2005年 | 4051篇 |
2004年 | 4038篇 |
2003年 | 3655篇 |
2002年 | 3577篇 |
2001年 | 2682篇 |
2000年 | 2678篇 |
1999年 | 2211篇 |
1998年 | 1005篇 |
1997年 | 795篇 |
1996年 | 741篇 |
1995年 | 716篇 |
1994年 | 680篇 |
1993年 | 619篇 |
1992年 | 1281篇 |
1991年 | 1244篇 |
1990年 | 1170篇 |
1989年 | 1111篇 |
1988年 | 996篇 |
1987年 | 948篇 |
1986年 | 893篇 |
1985年 | 848篇 |
1984年 | 719篇 |
1983年 | 677篇 |
1982年 | 571篇 |
1981年 | 531篇 |
1979年 | 693篇 |
1978年 | 524篇 |
1977年 | 466篇 |
1975年 | 526篇 |
1974年 | 541篇 |
1973年 | 494篇 |
1972年 | 493篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
Fabián Michelangeli Dalia M. Sulcas Marie-Christine Ruiz 《Cell and tissue research》1987,250(2):413-419
Summary This study is concerned with electron-microscopic observations on endocrine or paracrine cells in the fundic gastric mucosa of the bullfrog. Also, an attempt was made to identify the histamine-releasing cells involved in the secretagogue response. At least three distinct endocrine-like cell types were found. The classification is based on the appearance of secretory granules and other organelles, and the relationship of endocrine-like cells with other cells in the tissue. The amphibian endocrine-like cells resemble the ECL, D and EC cells of mammals. Type-I (ECL) cells showed degranulation after repeated stimulation with tetragastrin (TG), acetylcholine (ACh) and K+ depolarizing solution, all of which release histamine. 相似文献
105.
106.
Production of vanillic acid from vanillin by resting cells of Serratia marcescens. 总被引:2,自引:2,他引:0 下载免费PDF全文
Resting-cell suspensions of Serratia marcescens were able to convert, quantitatively, 0.3% vanillin to vanillic acid. The vanillic acid-producing activity reached a maximum after 28 h of incubation with 0.01% vanillin as an inducer. 相似文献
107.
Direct selection for curing and deletion of Rhizobium plasmids using transposons carrying the Bacillus subtilis sacB gene 总被引:13,自引:0,他引:13
We have constructed derivatives of the transposon Tn5 carrying the mob site (oriT) of plasmid RP4, and an nptI-sacB-sacR cassette [Ried and Collmer, Gene 57 (1987) 239-246]. The mob site, in conjunction with the antibiotic-resistance markers carried on the transposons, allows identification of transposon inserts in cryptic plasmids by mobilisation to other strains. The sacB-sacR genes allow direct selection for the loss or curing of plasmids, because only strains which no longer contain an active sacB gene are able to grow on media containing sucrose. We have tested these transposons in four strains of Rhizobium leguminosarum and two strains of Rhizobium meliloti, and have been able to demonstrate curing of several large cryptic plasmids, and generation of large deletions in many other plasmids. This method has enabled us to show that the R. leguminosarum plasmids pRL12JI and pR1eVF39f carry auxotrophic markers, and that the plasmid pR1eVF39c carries genes which affect colony morphology. 相似文献
108.
H. Wieler H. W. Hoffmanns A. Kippels S. Huhndorf A. Düx 《Radiation and environmental biophysics》1987,26(3):219-226
Summary The simultaneous use of intraarterial Cis-Platinum and Radiotherapy (CP/RT) was found to be a very effective and relatively little burdened treatment for a palliative treatment concept. This affects life quality as well as the remission - and survival times. The fast and continual remission with low CP/RT concentrations, even in extreme palliative cases, is surprising. CP/RT treatment shows additive and synergistic effects which are not explainable by the single effects of the cis-platinum dose used (60 mg/1.73 m2 in our case) or the total irradiation dose (e.g., 5 Gy TD) or the fractionation (e.g., 5 × 1 Gy), especially since the doses of each which were used are by themselves without therapeutic relevance. Only the combination of the modalities with a low dose two-day preradiation program induced the described effects.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday 相似文献
109.
110.
R. Brändén T. Nilsson S. Styring 《Biochemical and biophysical research communications》1980,92(4):1297-1305
A sensitive and reliable method to determine the stereochemical composition of 3-phosphoglyceric acid is presented. Results obtained with this method show that 3-phosphoglyceric acid formed in the ribulose-1,5-bisphosphate carboxylase reaction is a mixture of 10% L-3-PGA and 90% D-3-PGA. 相似文献