全文获取类型
收费全文 | 1748篇 |
免费 | 225篇 |
国内免费 | 34篇 |
出版年
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 38篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 40篇 |
2017年 | 38篇 |
2016年 | 50篇 |
2015年 | 86篇 |
2014年 | 94篇 |
2013年 | 116篇 |
2012年 | 137篇 |
2011年 | 137篇 |
2010年 | 85篇 |
2009年 | 69篇 |
2008年 | 81篇 |
2007年 | 74篇 |
2006年 | 92篇 |
2005年 | 79篇 |
2004年 | 68篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 33篇 |
2000年 | 43篇 |
1999年 | 28篇 |
1998年 | 26篇 |
1997年 | 24篇 |
1996年 | 19篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 11篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1973年 | 7篇 |
1971年 | 6篇 |
1949年 | 5篇 |
排序方式: 共有2007条查询结果,搜索用时 15 毫秒
41.
The apparent incidence of hyperparathyroidism (HPT) is low in pregnancy but will likely increase now that more asymptomatic HPT is being diagnosed. However, since the serum calcium levels are decreased in pregnant women, mild primary HPT may go unrecognized. In untreated cases of HPT, complications during pregnancy or during the neonatal period have included spontaneous abortion, stillbirth, neonatal death, neonatal tetany and hypercalcemia. A review of the literature indicates a substantial improvement in fetal outcome when parathyroidectomy is done during pregnancy, as in the case reported here. Therefore, parathyroidectomy is the treatment of choice when the diagnosis is made during pregnancy, although oral phosphate therapy may be an alternative if surgery is contraindicated. 相似文献
42.
Previously we described a cell line OCI-LY3 derived from a patient with non-Hodgkin's lymphoma. The cell line produced interleukin-6 (IL-6) mRNA and protein and demonstrated an autocrine pattern of growth for IL-6. Southern blot analysis of the IL-6 gene did not reveal any rearrangement. To determine whether the production of IL-6 by OCI-LY3 was due to subtle changes in the promoter of IL-6 or due to the expression of trans-acting factors chloramphenicol acetyltransferase (CAT) reporter constructs containing from -1,180 to +13 to -112 to +13 of a normal IL-6 gene were electroporated into the cell line. When these constructs are transferred into unstimulated fibroblasts, no CAT activity is seen; however, CAT activity is induced when the cells are stimulated with either IL-1 alpha, lipopolysaccharide (LPS), or cyclic adenosine monophosphate (cAMP) analogues. When the cell line OCI-LY3 was transfected with these constructs, CAT activity was observed; it was not necessary to stimulate the cells with exogenous factors to observe this activity. No CAT activity was observed in a second lymphoma cell line, OCI-LY13.1, that does not produce IL-6. These results suggest that the constitutive production of IL-6 by the cell line OCI-LY3 is due to the presence of trans-acting factors that stimulate the expression of IL-6 and not due to a cis-acting mutation of the IL-6 promoter. 相似文献
43.
Plant thioredoxin h: an animal-like thioredoxin occurring in multiple cell compartments 总被引:8,自引:0,他引:8
F Marcus S H Chamberlain C Chu F R Masiarz S Shin B C Yee B B Buchanan 《Archives of biochemistry and biophysics》1991,287(1):195-198
Thioredoxin h has been purified to electrophoretic homogeneity from spinach roots using a procedure devised for leaves. The root thioredoxin (h2 form) differed from chloroplast and animal thioredoxins in showing an atypical active site (Cys-Ala-Pro-Cys) but otherwise resembled animal thioredoxin in structure. Sequence data for a total of 72 residues of spinach root thioredoxin h2 (about 69% of the primary structure) showed 43-44% identity with rabbit and rat thioredoxin. Analysis of cell fractions from the endosperm of germinating castor beans revealed that thioredoxin h occurs in the cytosol, endoplasmic reticulum, and mitochondria. The present findings demonstrate a similarity between plant thioredoxin h and animal thioredoxins in structure and intracellular location and raise the question of whether these proteins have similar functions. 相似文献
44.
T Yee 《BioTechniques》1991,10(6):786-789
A computer program for digital image processing is described which can be implemented using scanning densitometer hardware pre-existing in most biology departments plus computer video hardware which may either pre-exist in the biology department or would represent a moderate upgrade over an already planned computer purchase. The primary purpose of this computer program is to provide contrast enhancement of faint or low contrast autoradiograph images and to implement background subtraction and digital smoothing methods which permit visualization of blurry electrophoresis bands against noisy backgrounds. However, the program also has modest editing capabilities that allow its use in the routine preparation of images for publication. Finally, the program has facilities for deblurring, edge enhancement and multiple image averaging, which give it usefulness in other forms of photographic analysis. 相似文献
45.
46.
Normal and Rous sarcoma virus (RSV)-transformed chick embryo fibroblasts growing on plastic dishes were incubated with ATP (γ32P) in situ to detect external cell surface protein kinase activity. Under the conditions employed, 32P was incorporated exclusively into proteins, specifically those at the external cell surface, as radioactivity was removed by tryspin treatment of labeled whole cells. In addition, exogenous histones were phosphorylated when added to the reaction mixture. Cyclic nucleotides had virtually no effect on 32P incorporation, suggesting that little or no cyclic nucleotide-dependent protein kinase activity was present at the external cell surface. Cell surface protein kinase activity was higher in transformed than in normal cells, and, using a temperature-sensitive RSV src mutant, this difference was shown to be transformation-specific. Several differences were observed in the cell surface proteins phosphoryllated in normal and transformed cells and at least two of these were transformation-specific. These data suggest that changes in external cell surface protein physphorylation are associated with RSV transformation and thus could play a role in the formation of the transformed cell phenotype. 相似文献
47.
Bead rings at the endoplasmic reticulum-golgi complex boundary: morphological changes accompanying inihibition of intracellular transport of secretory proteins in arthropod fat body tissue 下载免费PDF全文
DA Brodie 《The Journal of cell biology》1981,90(1):92-100
Golgi complex beads are 10-nm particles arranged in rings on the smooth surface of rough endoplasmic reticulum (ER) makind the forming face of the Golgi complex (GC). In arthropod cells they stain specifically with bismuth. Their morphology has been studied after treatment with reagents known to interfere with GC function. Inhibitors of oxidative phosphorylation (antimycin A, cyanide, and anoxia), but not an inhibitor of glycolysis (iodoacetate), both cause the bead rings to collapse and the GC saccules to round up, and inhibit transition vesicle (TV) formation. Cycloheximide blocks protein synthesis on ribosomes but does not stop TV formation or disrupt bead rings, even after prolonged treatment (6 h) to allow emptying of the rough ER cisternae. Thus the collapse of bead rings is not attributable to inhibition of protein synthesis, and the ring structure of beads does not require continued protein synthesis and secretion for its maintenance. Valinomycin has effects on the GC similar to those of antimycin A, but , monensin, and lasalocid do not affect bead ring structure or TV formation. These results are consistent with valinomycin’s secondarily uncoupling mitochondria, which collapses bead rings and prevents TV formation. Thus inhibitors of oxidative phosphorylation do not influence the beads through cation movement. Because mononsin and lasalocid block secretion at the level of the condensing vacuoles, bead rings are not influenced by blocks in secretion distal to them or by the backup of secretory material. These experiments are consistent with inhibitors of oxidative phosphorylation collapsing bead rings by decreasing intracellular ATP. The concomitant block to TV formation and the collapse of bead rings suggests that integrity of the bead rings is essential for the transport of secretory material from the rough ER to the GC. A23187相似文献
48.
49.
50.
Enterobacteriaceae and Pseudomonas aeruginosa Recovered from Vegetable Salads 总被引:5,自引:4,他引:1 下载免费PDF全文
Klebsiella, Enterobacter, and Serratia were recovered frequently in high counts from vegetable salads. Pseudomonas aeruginosa, although isolated frequently, was in lower counts. 相似文献