全文获取类型
收费全文 | 13585篇 |
免费 | 1149篇 |
国内免费 | 9篇 |
出版年
2022年 | 73篇 |
2021年 | 165篇 |
2020年 | 102篇 |
2019年 | 133篇 |
2018年 | 172篇 |
2017年 | 179篇 |
2016年 | 266篇 |
2015年 | 417篇 |
2014年 | 499篇 |
2013年 | 772篇 |
2012年 | 747篇 |
2011年 | 745篇 |
2010年 | 460篇 |
2009年 | 465篇 |
2008年 | 697篇 |
2007年 | 697篇 |
2006年 | 705篇 |
2005年 | 690篇 |
2004年 | 663篇 |
2003年 | 634篇 |
2002年 | 612篇 |
2001年 | 375篇 |
2000年 | 400篇 |
1999年 | 390篇 |
1998年 | 160篇 |
1997年 | 120篇 |
1996年 | 125篇 |
1995年 | 128篇 |
1994年 | 122篇 |
1993年 | 140篇 |
1992年 | 306篇 |
1991年 | 204篇 |
1990年 | 218篇 |
1989年 | 218篇 |
1988年 | 316篇 |
1987年 | 186篇 |
1986年 | 165篇 |
1985年 | 148篇 |
1984年 | 125篇 |
1983年 | 97篇 |
1982年 | 70篇 |
1981年 | 72篇 |
1980年 | 47篇 |
1979年 | 85篇 |
1978年 | 65篇 |
1977年 | 51篇 |
1976年 | 51篇 |
1975年 | 50篇 |
1974年 | 63篇 |
1972年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Effect of lard and corn oil intake on serum lipids in young men 总被引:2,自引:0,他引:2
M Imaki T Miyoshi S Tanada T Nakamura Y Yamada R Yamasaki H Terada 《Acta biologica Hungarica》1989,40(3):271-282
An experimental diet with lard (30 g/day for 7 days) and corn oil (30 g/day for 7 days) on high carbohydrate (basal diet) was given to four healthy Japanese young men and the effect of diets containing different fat on serum lipids was examined. Serum total cholesterol was increased significantly from a basal diet of 106 +/- 23 to 141 +/- 26 mg/dl on lard diet, and then decreased significantly (p less than 0.05) to 111 +/- 22 mg/dl on corn oil diet. Serum triglycerides increased significantly (p less than 0.01) from 66 +/- 38 to 173 +/- 32 mg/dl on basal diet. Serum HDL-cholesterol was decreased significantly (p less than 0.01) from 41.9 +/- 1.6 to 31.2 +/- 3.8 mg/dl on lard diet and increased significantly (p less than 0.05) to 41.9 +/- 4.6 mg/dl on corn oil diet. Serum HDL-cholesterol fraction was decreased significantly (p less than 0.01) from 41.6 +/- 4.9 to 28.1 +/- 3.2% on basal diets, but increased significantly (p less than 0.05) to 44.3 +/- 3.1% on lard diet, and then decreased to 36.3 +/- 2.5% on corn oil diet. Serum HDL phospholipid fraction decreased significantly (p less than 0.05) from 62.5 +/- 6.7 to 50.7 +/- 1.8% on basal diet and increased significantly (p less than 0.05) to 60.4 +/- 1.0% on lard and corn oil diet. Serum phospholipids did not change by experimental diets. It is concluded that lard and corn oil have different and specific roles in lipid metabolism. 相似文献
72.
Summary Distribution of molluscan cardio-excitatory tetrapeptide Phe—Met—Arg—Phe—NH2 (FMRFamide) was determined by means of immunohistochemistry in the brain and neurohypophysis of the lamprey, Lampetra japonica. Many FMRFamide-like immunoreactive neurons were found in the periventricular nuclear region and in a region near the mammillary recess. Neurons situated in the former region were larger. The immunoreactive cell groups were shown to be located at sites differing from those of the AF-positive cell groups. The fibers of immunoreactive neurons extended in all directions within the brain and towards the spinal cord, some reaching the third ventricle and capillaries. Thus, FMRFamide-like immunoreactive peptides appear to function as neurotransmitters or neuromodulators and possibly also as neurohormones. FMRFamide-like immunoreactive material was rarely observed in the posterior neurohypophysis (neural lobe), but was noted to be present to a limited extent in the caudal part of the anterior neurohypophysis (median eminence). It would thus follow that FMRFamide-like immunoreactive neurons may not necessarily be related to the hypothalamo-neural lobe system, but may possibly be associated with the hypothalamoadenohypophysial system. The pineal body showed no FMRFamide-like immunoreactivity. 相似文献
73.
Dr. Shigeru Sakiyama Yohko Nakamura Katsuo Tokunaga Hiroshi Takazawa Yoshinori Ohwaki Toshio Nagano 《Cell and tissue research》1989,258(2):225-231
Summary In-situ hybridization experiments have been performed using isoactin ( and )-specific riboprobes in various tissues of the rat and mouse. Distribution of the grains of actin mRNAs for both and types was similar throughout sections of the rat testis. Although both mRNAs were evenly distributed in the seminiferous tubule, extremely heavy labeling was observed in about 10% of the seminiferous tubules that could be identified as stage XII of spermatogenesis. At high magnification, grains of the mRNA were found in the cytoplasm of elongating spermatids and in the Sertoli cell cytoplasm at the adluminal side. Much higher density of the grains of mRNA was observed in the neck region of the spermatids at stage XII. Thus, the dense distribution of cytoskeletal actin mRNAs is stage-specific in the tubule during spermatogenesis in the rat. The high expression of both and actin mRNAs was also observed in the epithelial cells of the intestinal crypts. 相似文献
74.
75.
76.
77.
We measured the intra-platelet content of human epidermal growth factor (hEGF) and beta-thromboglobulin (beta-TG) and the quantities of these released from platelets during in vitro aggregation. The intra-platelet amounts of hEGF and beta-TG in 10(8) platelets were 104.9 +/- 18.9 (Mean +/- SEM) pg and 2920.9 +/- 149.9 ng, respectively. During platelet aggregation elicited by 9, 11-epithio-11, 12-methano-thromboxane A2, a stable thromboxane A2 agonist, hEGF and beta-TG were released in amounts about 50% and 40% of the respective content in platelets. Also during arachidonate-induced aggregation, hEGF and beta-TG were released at about 60% and 50%, respectively. Various concentrations of thromboxane A2 antagonist, (9, 11), (11, 12)-di-deoxa-9, 11-dimethyl-methano-11, 12-methano-13, 14-dihydro-13-aza-14-oxo-15-cyclopentyl-16, 17, 18, 19, 20-pentanor-15-epi-thromboxane A2, suppressed both aggregation and release reactions in a dose-dependent manner. There were good correlations between the platelet aggregation rate and released beta-TG (r = 0.9368, p less than 0.01) or hEGF (r = 0.8931, p less than 0.01) and between released beta-TG and hEGF (r = 0.9385, p less than 0.01). These results suggest that hEGF is released from platelets in a similar fashion to beta-TG in vitro. 相似文献
78.
F Suzuki S Miyazaki M Uozumi N Okamoto S Yamashita K Murakami Y Nakamura 《FEBS letters》1989,256(1-2):47-50
The release of prorenin as well as renin from rat renal slices was confirmed by a rat prorenin-prosegment ELISA system and an assay system for determining the renin activity. A significant increase of the prorenin release was found by adding rat submandibular gland extract to the slice medium, indicating the existence of a prorenin-releasing stimulator (PRS) in the extract. The pI and molecular mass of PRS were 8.5-8.7 and 28-30 kDa, respectively. The PRS was completely inactivated by boiling or a proteinase treatment. 相似文献
79.
T Nakahara A Shiraishi M Hirano T Matsumoto T Kuroki Y Tatebayashi T Tsutsumi K Nishiyama H Ooboshi K Nakamura 《Analytical biochemistry》1989,180(1):38-42
A highly sensitive assay for guanine was developed using high-performance liquid chromatography with electrochemical detection (ECD). Guanine was susceptible to the electrochemical oxidation, and ECD response was proportional to the amount of guanine in the range 0.25-4 pmol of guanine. The ECD of guanine was applicable to the analysis of nucleic acids. DNA and RNA were hydrolyzed in 0.03 and 3 M HCl, respectively, and guanine liberated from the nucleic acids was separated on a reverse-phase column and determined by ECD. The method allowed detection of 0.2 ng of calf thymus DNA or tRNA. An application of the method is shown for DNA and RNA assays in trichloroacetic acid extracts of rat adrenal and liver. 相似文献
80.
H R Prasanna K D Nakamura S F Ali M H Lu W Slikker R W Hart 《Biochemical and biophysical research communications》1989,160(1):217-221
The microsomal activation of the potent hepatocarcinogen aflatoxin B1 (AFB1) and the expression of selected protooncogenes were investigated in the livers of rats exposed to delta 9-tetrahydrocannabinol (THC). At equimolar levels of cytochrome P-450, the microsome-mediated binding of AFB1 to DNA was significantly lower (56% of the controls) in preparations from drug exposed rats. Hepatic expression of the c-k-ras protooncogene was 3-fold higher in THC exposed animals. These results suggest the possible occurrence of long lasting residual effects in the rats exposed to THC. 相似文献