全文获取类型
收费全文 | 103858篇 |
免费 | 8183篇 |
国内免费 | 32篇 |
出版年
2021年 | 887篇 |
2018年 | 1371篇 |
2017年 | 1269篇 |
2016年 | 1723篇 |
2015年 | 1871篇 |
2014年 | 2243篇 |
2013年 | 3306篇 |
2012年 | 3548篇 |
2011年 | 3658篇 |
2010年 | 2660篇 |
2009年 | 2268篇 |
2008年 | 3363篇 |
2007年 | 3291篇 |
2006年 | 3152篇 |
2005年 | 2971篇 |
2004年 | 2955篇 |
2003年 | 2844篇 |
2002年 | 2667篇 |
2001年 | 4684篇 |
2000年 | 4430篇 |
1999年 | 3452篇 |
1998年 | 1134篇 |
1997年 | 1118篇 |
1996年 | 985篇 |
1995年 | 903篇 |
1994年 | 887篇 |
1993年 | 904篇 |
1992年 | 2601篇 |
1991年 | 2620篇 |
1990年 | 2605篇 |
1989年 | 2348篇 |
1988年 | 2203篇 |
1987年 | 2096篇 |
1986年 | 1918篇 |
1985年 | 1898篇 |
1984年 | 1597篇 |
1983年 | 1373篇 |
1982年 | 974篇 |
1981年 | 916篇 |
1979年 | 1530篇 |
1978年 | 1194篇 |
1977年 | 1088篇 |
1976年 | 1010篇 |
1975年 | 1197篇 |
1974年 | 1298篇 |
1973年 | 1380篇 |
1972年 | 1225篇 |
1971年 | 1071篇 |
1970年 | 945篇 |
1969年 | 985篇 |
排序方式: 共有10000条查询结果,搜索用时 937 毫秒
991.
A Rethwilm G Baunach K O Netzer B Maurer B Borisch V ter Meulen 《Nucleic acids research》1990,18(4):733-738
992.
993.
994.
DNA ploidy pattern and amplification of ERBB and ERBB2 genes in human gastric carcinomas 总被引:1,自引:0,他引:1
N Oda T Tsujino T Tsuda K Yoshida H Nakayama W Yasui E Tahara 《Virchows Archiv. B, Cell pathology including molecular pathology》1990,58(4):273-277
The DNA ploidy pattern and amplification of ERBB and ERBB2 genes were examined in paraffin-embedded tissue from gastric carcinomas using flow cytometry and a slot-blot hybridization technique. The incidence of aneuploidy in well differentiated adenocarcinomas (56%) was significantly higher (p less than 0.05) than that in poorly differentiated adenocarcinomas (21%). The DNA ploidy pattern was not remarkably different between the primary tumors and metastatic deposits in lymph nodes. Of the nine specimens having an aneuploid stem cell line in the primary tumor and/or in metastases, three showed ERBB2 gene amplification and one showed ERBB gene amplification. The incidence of epidermal growth factor (EGF) immunoreactivity in tumor cells showed no difference between diploid and aneuploid tumors. These findings indicate that aneuploidy is frequently associated with amplification of ERBB and ERBB2 genes. 相似文献
995.
The effects of Zn2+ on the activity of the angiotensin-converting enzyme from bovine lung towards the substrates, FA-Phe-Gly-Gly and Cbz-Phe-His-Leu, have been studied. At pH below 7.0 zinc ions added to the reaction mixture increase the enzyme activity; this stimulating effect is changed to inhibition with a further rise in Zn2+ concentration. It was shown that the dissociation constant for the enzyme--Zn2+ complex and the "optimal" concentrations of Zn2+ needed for the manifestation of the maximal enzymatic activity depend on the nature of the substrate at all pH values studied. 相似文献
996.
Masanori Ito Kazuhiro Yoshida Eikai Kyo Ayse Ayhan Hirofumi Nakayama Wataru Yasui Hisao Ito Eiichi Tahara 《Virchows Archiv. B, Cell pathology including molecular pathology》1990,59(1):173-178
We have examined the expression of mRNAs for epidermal growth factor (EGF), transforming growth factor-alpha (TGF-α), EGF
receptor (EGFR), PDGF-A chain (PDGFA), PDGF-B chain (PDGFB) and PDGF receptor (PDGFR) genes in seven human colorectal carcinoma
cell lines and 18 human colorectal carcinomas.
In surgically resected specimens of the 18 colorectal tumors, TGF-α, EGFR, PDGFA, PDGFB and PDGFR mRNAs were detected at various
levels in 15 (83%), 9 (50%), 18 (100%), 8 (44%) and 12 (67%), respectively. They were also detected in normal tissues. Interestingly,
EGF mRNA was detected in only five (28%) of the tumors, but not in normal mucosa. Expression of EGF was also confirmed immunohistochemically
in tumor cells. Of the five tumors expressing EGF, four expressed EGFR mRNA and showed a tendency to invade veins and lymphatics.
All the colorectal carcinoma cell lines expressed TGF-α mRNA, and five cell lines expressed EGFR mRNA simultaneously. Production
of TGF-α protein by DLD-1 and CoLo320DM cells was confirmed by TGF-α specific monoclonal antibody binding assay. The spontaneous3H-thymidine uptake by DLD-1 was suppressed by an anti-TGF-α monoclonal antibody. PDGFA and PDGFB mRNA were also expressed
in four cell lines, but PDGFR and EGF mRNA was not detected. These results suggest that human colorectal carcinomas express
multi-loops of growth factors and that TGF-α produced by tumor cells functions as an autocrine growth factor in human colonic
carcinoma. 相似文献
997.
Studies on DNA markers (D4S10 and D4S43/S127) genetically linked to Huntington's disease in Japanese families 总被引:1,自引:0,他引:1
Ichiro Kanazawa Ikuko Kondo Joh-E Ikeda Teruaki Ikeda Yuichior Shizu Mitsuo Yoshida Hirotaro Narabayashi Shigetoshi Kuroda Hisayuki Tsunoda Eiji Mizuta Yoko Okuno Kiyotaka Sugawara Miho Murata Mafuyu Takahashi James F. Gusella 《Human genetics》1990,85(3):257-260
Summary This is the first full report on the genetic linkage between Japanese Huntington's disease and the DNA markers D4S10 and D4S43/S127. With use of the HindIII, BglI, and EcoRI polymorphisms detected at D4S10, and the combination of all these polymorphisms to give composite haplotypes, nine Japanese Huntington's disease families were found to be informative. Three recombinants for D4S10 were detected in these families, giving a maximum lod score of 1.662 at a of 0.10. Similarly, when we used the MspI and PvuII polymorphisms detected by D4S43/S127, five families gave informative results. No recombinant was detected in these families, giving a maximum lod score of 3.348 at a of 0.00. These results clearly support the view that the Japanese Huntington's disease gene may be identical with the Western gene, in spite of the lower prevalence rate in Japan. 相似文献
998.
Organization and nucleotide sequence of the genes for ribosomal protein S2 and elongation factor Ts in Spirulina Platensis 总被引:2,自引:0,他引:2
Anna Maria Sanangelantoni Raffaele C. Calogero Francesca R. Butarelli Caludio O. Gualerzi Orsola Tiboni 《FEMS microbiology letters》1990,66(1-3):141-146
A 6.5 kb region from the genome of the cyanobacterium Spirulina platensis was cloned using as a probe the Escherichia coli gene for ribosomal protein S2. Sequence analysis revealed, in this region, the presence of the gene for ribosomal protein S2 and part of the gene for the elongation factor Ts (EF-Ts). The arrangement rpsB-spacer-tsf resembles that reported for E. coli. The deduced amino acid sequences of the platensis S2 and EF-Ts show significant homology with the E. coli counterparts. 相似文献
999.
The enzymatic mechanism and the kinetic parameters of GABA-transaminase extracted from cultured mouse cerebral cortex neurons and astrocytes were studied. Neuronal as well as astrocytic GABA-transaminase obeyed a bi bi ping-pong reaction mechanism. The estimated Km-values for -ketoglutarate and GABA were significantly lower for astroglial GABA-transaminase compared to the neuronal enzyme suggesting a possible existence of cell specific isozymes of GABA-transaminase. The observed enzymatic mechanism and the magnitude of the estimated kinetic parameters imply that GABA-transaminase synthesized in the two types of cultured neural cells is mechanistically and kinetically equivalent to the enzyme synthesized in the brainin vivo. 相似文献
1000.
O N Serova 《Biulleten' eksperimental'no? biologii i meditsiny》1990,109(3):215-217
Taste receptor organ activity and preference of sodium chloride solution in rats with deficit of substance P (SP) were studied. Total impulse activity of chorda tympani nerve of 7-8 week old rats was recorded under nembutal anesthesia. The taste responses to four solutions (sucrose, quinine sulfate, sodium chloride and citric acid) were decreased in rats injected with capsaicin in comparison with rats injected with vehicle. The rats injected with capsaicin preferred water to sodium chloride (two-bottle technique). On the contrary the rats injected with capsaicin preferred the salt solution. These data together with previous studies show the important role of peptide SP in taste receptor activity and "salt appetite". 相似文献