全文获取类型
收费全文 | 5674篇 |
免费 | 328篇 |
出版年
2022年 | 26篇 |
2021年 | 55篇 |
2019年 | 32篇 |
2018年 | 68篇 |
2017年 | 53篇 |
2016年 | 94篇 |
2015年 | 163篇 |
2014年 | 171篇 |
2013年 | 326篇 |
2012年 | 291篇 |
2011年 | 307篇 |
2010年 | 187篇 |
2009年 | 174篇 |
2008年 | 313篇 |
2007年 | 294篇 |
2006年 | 263篇 |
2005年 | 306篇 |
2004年 | 287篇 |
2003年 | 297篇 |
2002年 | 278篇 |
2001年 | 164篇 |
2000年 | 144篇 |
1999年 | 151篇 |
1998年 | 83篇 |
1997年 | 71篇 |
1996年 | 73篇 |
1995年 | 86篇 |
1994年 | 47篇 |
1993年 | 55篇 |
1992年 | 121篇 |
1991年 | 84篇 |
1990年 | 86篇 |
1989年 | 76篇 |
1988年 | 78篇 |
1987年 | 73篇 |
1986年 | 58篇 |
1985年 | 53篇 |
1984年 | 46篇 |
1983年 | 46篇 |
1982年 | 41篇 |
1981年 | 33篇 |
1980年 | 24篇 |
1979年 | 32篇 |
1978年 | 33篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1975年 | 31篇 |
1973年 | 22篇 |
1970年 | 24篇 |
1968年 | 19篇 |
排序方式: 共有6002条查询结果,搜索用时 15 毫秒
21.
The fluorescent body (F-body) was identified with quinacrine mustard (Q-M) staining in spermatozoon and lymphocyte of canine. Well washed sperm suspension was treated with protease (125 mg/ml) or dispase (2000p. u./ml) and staining with Q-M (final dilution 50 micrograms/ml) for 15 min to 24 hr at 37 degrees C. The lymphocyte cultures from whole blood were prepared as routine human investigation. The chromosomal preparation made by air dry method was stained with Q-M (final dilution 0.5 to 50 micrograms/ml) after pretreatment of enzyme digestion. The examination using a reflected fluorescent microscope revealed that the same F-body in human was present in both spermatozoon (20.1-39.7%) and interphase of lymphocyte (0.37.2%) of male origin. 相似文献
22.
Isolation and Characterization of an Enterobacter cloacae Strain That Reduces Hexavalent Chromium under Anaerobic Conditions 总被引:12,自引:6,他引:6
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pi-Chao Wang Tsukasa Mori Kohya Komori Masanori Sasatsu Kiyoshi Toda Hisao Ohtake 《Applied microbiology》1989,55(7):1665-1669
An Enterobacter cloacae strain (HO1) capable of reducing hexavalent chromium (chromate) was isolated from activated sludge. This bacterium was resistant to chromate under both aerobic and anaerobic conditions. Only the anaerobic culture of the E. cloacae isolate showed chromate reduction. In the anaerobic culture, yellow turned white with chromate and the turbidity increased as the reduction proceeded, suggesting that insoluble chromium hydroxide was formed. E. cloacae is likely to utilize toxic chromate as an electron acceptor anaerobically because (i) the anaerobic growth of E. cloacae HO1 accompanied the decrease of toxic chromate in culture medium, (ii) the chromate-reducing activity was rapidly inhibited by oxygen, and (iii) the reduction occurred more rapidly in glycerol- or acetate-grown cells than in glucose-grown cells. The chromate reduction in E. cloacae HO1 was observed at pH 6.0 to 8.5 (optimum pH, 7.0) and at 10 to 40°C (optimum, 30°C). 相似文献
23.
Molecular cloning and nucleotide sequence of human pancreatic prechymotrypsinogen cDNA 总被引:4,自引:0,他引:4
N Tomita Y Izumoto A Horii S Doi H Yokouchi M Ogawa T Mori K Matsubara 《Biochemical and biophysical research communications》1989,158(2):569-575
The cDNA clone encoding human prechymotrypsinogen was isolated from a human pancreas cDNA library and its nucleotide sequence was determined. The sequence consists of a 16 bp 5' non-coding region, a 789 bp amino acid coding region and a 60 bp 3' non-coding region. The predicted product consists of 263 amino acids, including 18 amino acids for a signal peptide and 15 amino acids possible for an activation peptide. Southern blot analyses using the cloned cDNA as a probe revealed that human genomic DNA carries at least two genes that are related to chymotrypsinogen. 相似文献
24.
The growth inhibitor of African green monkey (BSC-1) cells is transforming growth factors beta 1 and beta 2 总被引:1,自引:0,他引:1
The growth inhibitory activity in conditioned medium of African green monkey kidney epithelial (BSC-1) cells that has been shown to arise, at least in part, from transforming growth factor beta 2 (TGF-beta 2) [Hanks, S. K., Armour, R., Baldwin, J. H., Maldonado, F., Spiess, J., & Holley, R. W. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 79-82] was tested for growth inhibitory activity prior to and following acidification. Similar to TGF-beta 1 from human platelets, the inhibitory activity from BSC-1 cells demonstrated an 8-10-fold stimulation following acidification, showing that the activity was secreted from the cells in latent form. Conditioned medium from BSC-1 cells was collected, acidified, and fractionated by procedures that separate TGF-beta 1 and -2. Biological activity was assayed by using the BSC-1 cell proliferation assay. Two active proteins with properties similar to known TGF-beta 1 and TGF-beta 2 were identified. Identity was confirmed by using immunological and amino acid sequencing techniques. These results were consistent with Northern blot analysis of total BSC-1 RNA, using cDNA probes for TGF-beta 1 and TGF-beta 2, which demonstrated strong signals for both mRNAs. Metabolic labeling in conjunction with two-dimensional gel electrophoresis revealed that the cells secrete approximately 10% TGF-beta 1 and 90% TGF-beta 2. 相似文献
25.
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
26.
Identification of a novel alpha-amylase by expression of a newly cloned human amy3 cDNA in yeast 总被引:1,自引:0,他引:1
A novel amylase gene (amy3) that differs in nucleotide sequence from salivary amylase gene (amy1) and pancreatic amylase gene (amy2) has been described [Tomita et al., Gene 76 (1989) 11-18], but whether this gene can ever code for an active enzyme has not been shown. We prepared cDNA of this gene from an mRNA obtained from lung carcinoid tissue, and expressed it in Saccharomyces cerevisiae under the control of an acid phosphatase promoter. The product was secreted into culture media, and showed enzymatic activity, demonstrating that this novel alpha-amylase gene (amy3) can code for a functional isozyme. We purified this enzyme, and compared its biological properties with those of salivary and pancreatic human amylases similarly expressed in yeast. We observed that the novel amylase isozyme is more heat-sensitive than others, and that its substrate specificity is different from the other two isozymes. 相似文献
27.
Summary An attempt at cytochemical demonstration of acidification proton-translocating ATPase (H+-ATPase) of Golgi complex in rat pancreatic acinar cells has been made by using p-nitrophenylphosphatase (NPPase) cytochemistry
which is used for detecting of Na+-K+-ATPase (Mayahara et al. 1980) and gastric H+-K+-ATPase (Fujimoto et al. 1986). K+-independent NPPase activity was observed on the membrane of the trans cisternae of Golgi complex, but not inside of cisternae. The localization of NPPase activity is different from that of acid
phosphatase activity where reaction products were seen on the inside of the trans Golgi cisternae. Since this activity was insensitive to vanadate, ouabain and independent of potassium ions, it was distinct
from plasma membranous ATPases such as Na+-K+-ATPase and Ca2+-ATPase. The K+-independent NPPase activity was diminished by the inhibitors of H+-ATPase such as N-ethylmaleimide (NEM) and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS). The NPPase reaction products
were also seen on the membranes of other acidic organelles, i.e., lysosomes, endosomes, autophagosomes and coated vesicles.
These results suggest that NPPase activity on the membrane of the Golgi complex and other acidic organelles corresponds with
H+-ATPase which plays a role in acidification. 相似文献
28.
Dr. Kazuo Tamura Masanori Takeuchi Nobuyuki Hirakawa Kiyokazu Toyoda Masaru Minoda 《Biotherapy》1990,2(3):223-226
The 35-year-old man with myelodysplastic syndrome (MDS) and granulocytopenia with dry cough and high fever was eventually found to have a left perinephric abscess ofStaphylococcus aureus. He underwent left nephrectomy and drainage of perinephric space in conjunction with appropriate antibiotics. However, because of persistent granulocytopenia,Staph. aureus never cleared up with formation of only poor granulation. Recombinant human granulocyte colony-stimulating factor (G-CSF) was added to the above treatment leading to prompt improvement in granulocytopenia and emergence of the good granulation tissue. G-CSF will probably become one of the important agents in treating MDS with granulocytopenia. 相似文献
29.
The embryo splitting technique was applied to pig embryos, and the developmental ability of the split embryos was examined by means of in vitro culture and transfer. Morulae, early blastocysts and blastocysts were collected from Landrace x Large White F(1) gilts which had been mated to Duroc boars. The embryos were bisected with a fine glass or alloy (PtIr) needle after the softening of zonae pellucidae. The halved-embryos, which had either been placed in zonae pellucidae or not, were transferred to recipient gilts immediately after the micromanipulation (Experiment 1) or after cultivation for 15 to 20 h (Experiment 2). In Experiment 1, two fetuses were obtained from one of three recipients which had received 12 half-embryos. In Experiment 2, three of five recipients became pregnant, and in one recipient, seven piglets of a litter were obtained from 12 zona-free half-embryos produced from the original seven blastocysts. The results obtained indicate that a simple method not requiring the encasing of split embryos into zonae pellucidae is satisfactory to produce viable half-embryos. 相似文献
30.