全文获取类型
收费全文 | 2546篇 |
免费 | 136篇 |
出版年
2022年 | 11篇 |
2021年 | 20篇 |
2019年 | 19篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 37篇 |
2015年 | 47篇 |
2014年 | 55篇 |
2013年 | 103篇 |
2012年 | 98篇 |
2011年 | 108篇 |
2010年 | 87篇 |
2009年 | 68篇 |
2008年 | 116篇 |
2007年 | 128篇 |
2006年 | 108篇 |
2005年 | 120篇 |
2004年 | 119篇 |
2003年 | 124篇 |
2002年 | 115篇 |
2001年 | 99篇 |
2000年 | 100篇 |
1999年 | 97篇 |
1998年 | 31篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 23篇 |
1992年 | 72篇 |
1991年 | 47篇 |
1990年 | 62篇 |
1989年 | 50篇 |
1988年 | 42篇 |
1987年 | 38篇 |
1986年 | 45篇 |
1985年 | 50篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1979年 | 19篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 9篇 |
1973年 | 16篇 |
1972年 | 12篇 |
1970年 | 12篇 |
排序方式: 共有2682条查询结果,搜索用时 140 毫秒
81.
A wild bean weevil,Kytorhinus sharpianus Bridwell (Coleoptera: Bruchidae), has a multivoltine life cycle and enters a hibernal larval diapause at the fourth instar
under a short daylength (Shimada & Ishihara, 1991). Here, we investigated their diapause incidence under different photoperiods
at 24°C and 27°C. The critical photoperiods for diapause induction were 14.5 h at 24°C and 14 h at 27°C. The stages susceptible
to diapause-inducing stimuli were estimated by transferring larvae of various instars from long days to short days and vice
versa. Then we investigated the incidence of larval diapause. The sensitive stage was estimated to be from the third to early
fourth instar. Though larval diapause, which was induced under a short daylength, was terminated only by increasing the daylength,
the termination was more synchronized by an exposure to a low temperature followed by increasing temperature, irrespective
of photoperiod. 相似文献
82.
Hepatic dysfunction in primary hypothyroidism 总被引:1,自引:0,他引:1
Twenty-seven patients with primary hypothyroidism were studied to evaluate the relationship between hepatic function and thyroid hormone deficiency in this disorder. In hypothyroidism, hypergammaglobulinemia was found in 71%, elevated glutamic oxaloacetic transaminase (GOT) in 48%, high lactic dehydrogenase (LDH) in 58%, hypercholesteremia in 52% and low elimination rate constant of indocyanin green (KICG) in 44%. In each criterion of liver function, these patients were divided into two groups, normal level and abnormal level group, respectively. T3 and T4 in patients with abnormal levels of GOT, glutamic pyruvic transaminase (GPT), gamma-glutamyl transpeptidase (gamma-GTP), leucine aminopeptidase (LAP), alkaline phosphatase (ALP) and 45 minutes retention rate of bromsulphalein (BSP) were not different from those in the normal level group. However, T3 and T4 in patients with abnormal levels of LDH, cholesterol, cholinesterase (ChE) and KICG were lower than those in the normal level group. The abnormal KICG group had a statistically higher cardio-thoracic ratio (CTR) than the normal group (65.7 +/- 18.8% vs 50.4 +/- 8.3%, p less than 0.05). In patients with pericardial effusion, CTR was 65.9 +/- 14.6%, while that in patients without pericardial effusion was 49.9 +/- 7.5% (p less than 0.05). These abnormalities of liver function were normalized in all cases after hormone replacement therapy. Liver biopsy in three cases disclosed normal liver in two cases and mild infiltration of monocyte into Glisson's capsule in one case.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
83.
Bacterial dihydropyrimidinase was shown to catalyze the hydrolytic cleavage of various 5-substituted hydantoins to the corresponding N-carbamyl-D-amino acids under alkaline conditions. Therefore, an enzymatic method for preparing the D-forms of phenylglycine-related amino acids was developed using immobilized bacterial cells with high enzyme activity. Alkalophilic bacteria were a good enzyme source for this process. The process is simple and economical for use in the production of various amino acids with the D-configuration. 相似文献
84.
Troponin in embryonic chick skeletal muscle cells in vitro. An immunoelectron microscope study
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The fine structurel distribution of troponin on thin filaments in developing myofibrils was investigated by the use of immunoelectron microscopy. Embryonic chick skeletal muscle cells grown in vitro were treated with antibodies against each of the troponin components (troponin T, I, and C) from adult chicken muscles. Each antibody was distributed along the thin filaments with a period of 38 nm. It is concluded that these newly synthesized regulatory proteins are assembled at their characteristic position from the initial phases of myofibrillogenesis. 相似文献
85.
Masahisa Shimada 《Neurochemical research》1981,6(9):993-1003
Glucose uptake of individual structures within the brain was studied by dry-autoradiography with 2-deoxy-D-[14C(U)]glucose under mild hypoxic hypoxia (12% O288% N2 or 9% O291% N2 for 1 hr). Glucose consumption in the whole brain was estimated by combined gas chromatography-mass spectrometry (GC-MS). Mild hypoxia increased the optical density of the autoradiograph in all regions. The deuterated G-6-P (Glucose-6-phosphate) synthesized from deuterated glucose decreased significantly with 9% O2 hypoxia (P<0.05). The ratio of the deuterated G-6-P to deuterated glucose, a more appropriate indicator of glucose utilization than the concentration of deuterated G-6-P, decreased significantly with 12% O2 hypoxia (P<0.01). The hippocampus, white matter, colliculus superior, and corpus geniculatum laterale appeared to be particulary sensitive to hypoxia. 相似文献
86.
Isolation and characterization of a plaque-forming lambda bacteriophage carrying a ColE1 plasmid 总被引:3,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A plaque-forming lambdaimm434 bacteriophage carrying the entire genome of colicinogenic factor E1 has been isolated and characterized. This phage, lambdaimm434ColE1, can lysogenize as a stable plasmid within a recombination-deficient Escherichia coli cell that lacks the normal attachment site for lambda phage. Furthermore, it has been found that lambdaimm434ColE1 phage carrying amber mutations in the O and P genes of the lambda genome, i.e., lambdaimm434OamPamColE1, behaves as a plaque-forming phage, and this finding suggests that the ColE1 factor DNA permits replication of the DNA of the plaque-forming phage. 相似文献
87.
Fine structure of the recB and recC gene region of Escherichia coli 总被引:14,自引:0,他引:14
M Sasaki T Fujiyoshi K Shimada Y Takagi 《Biochemical and biophysical research communications》1982,109(2):414-422
88.
A 59-year-old woman with primary hyperparathyroidism was found to have a parathyroid adenoma behind the left clavicle. Preoperatively, it appeared as a hypoechoic mass on ultrasonography, as a hot nodule on thallium scintigraphy, and as a high signal on T2-weighted magnetic resonance imaging. Histological, immunohistochemical and ultrastructural studies of the surgically resected tumor revealed a parathyroid adenoma composed mainly of oxyphil cells with production of a parathyroid hormone. Moreover, a multilocular lesion of lymphangiectasia was contained. Hypercalcemia was alleviated postoperatively. These observations corroborated a functioning parathyroid oxyphil cell adenoma. This is the first case report of functioning oxyphil cell adenoma of the parathyroid gland with lymphangiectasia in Japan. 相似文献
89.
90.
A Pal T Ramamurthy R K Bhadra T Takeda T Shimada Y Takeda G B Nair S C Pal S Chakrabarti 《Applied and environmental microbiology》1992,58(8):2485-2489
A collection of 521 environmental isolates of Vibrio cholerae which were previously examined by the suckling mouse assay and found to be negative for the heat-stable enterotoxin NAG-ST were reassessed by a recently developed DNA probe for NAG-ST. A total of 12 (2.3%) of the isolates hybridized with the NAG-ST probe. By using a cholera toxin (CT) DNA probe, the CT gene was detected in six of the strains in the collection, although none of the isolates of V. cholerae non-O1 hybridized with both of the toxin probes. All of the NAG-ST and CT probe-positive strains were hemolysin positive. Thirty-fold-concentrated supernatants of the three representative NAG-ST DNA probe-positive V. cholerae non-O1 strains gave positive fluid accumulation ratios in the suckling mouse assay even after heating (100 degrees C for 5 min) and also inhibited the binding of a NAG-ST monoclonal antibody to the bound NAG-ST in a competitive enzyme-linked immunosorbent assay (ELISA). Likewise, all six CT probe-positive V. cholerae non-O1 strains produced in vitro CT when examined by the CT bead ELISA. HindIII digest patterns of chromosomal DNA from the representative NAG-ST gene-positive strains were visually indistinguishable. Between the groups of NAG-ST probe-positive strains examined, there was a variation in the hybridizable fragments, with one group of strains exhibiting a hybridizable fragment similar to that of the NRT 36 reference strain; a smaller HindIII fragment hybridized with the NAG-ST probe in the other group of strains.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献