全文获取类型
收费全文 | 379716篇 |
免费 | 24924篇 |
国内免费 | 2825篇 |
专业分类
耳鼻咽喉 | 5206篇 |
儿科学 | 8233篇 |
妇产科学 | 10104篇 |
基础医学 | 53293篇 |
口腔科学 | 11839篇 |
临床医学 | 30204篇 |
内科学 | 78615篇 |
皮肤病学 | 8554篇 |
神经病学 | 27265篇 |
特种医学 | 13946篇 |
外国民族医学 | 82篇 |
外科学 | 60760篇 |
综合类 | 9958篇 |
现状与发展 | 1篇 |
一般理论 | 64篇 |
预防医学 | 17498篇 |
眼科学 | 9453篇 |
药学 | 31048篇 |
1篇 | |
中国医学 | 2196篇 |
肿瘤学 | 29145篇 |
出版年
2021年 | 2652篇 |
2019年 | 2744篇 |
2018年 | 4534篇 |
2017年 | 3459篇 |
2016年 | 3546篇 |
2015年 | 4051篇 |
2014年 | 5731篇 |
2013年 | 7411篇 |
2012年 | 10080篇 |
2011年 | 10262篇 |
2010年 | 6224篇 |
2009年 | 5880篇 |
2008年 | 9508篇 |
2007年 | 10351篇 |
2006年 | 10283篇 |
2005年 | 9347篇 |
2004年 | 8885篇 |
2003年 | 8575篇 |
2002年 | 8270篇 |
2001年 | 28308篇 |
2000年 | 28815篇 |
1999年 | 23697篇 |
1998年 | 5178篇 |
1997年 | 4260篇 |
1996年 | 3838篇 |
1995年 | 3487篇 |
1994年 | 3108篇 |
1993年 | 2852篇 |
1992年 | 16065篇 |
1991年 | 14832篇 |
1990年 | 14168篇 |
1989年 | 13975篇 |
1988年 | 12600篇 |
1987年 | 12075篇 |
1986年 | 11116篇 |
1985年 | 10338篇 |
1984年 | 6919篇 |
1983年 | 5612篇 |
1982年 | 2721篇 |
1979年 | 5482篇 |
1978年 | 3352篇 |
1977年 | 2974篇 |
1975年 | 2646篇 |
1974年 | 3073篇 |
1973年 | 2868篇 |
1972年 | 2833篇 |
1971年 | 2779篇 |
1970年 | 2516篇 |
1969年 | 2550篇 |
1968年 | 2257篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Autonomic Regulation of Voltage-Gated Cardiac Ion Channels 总被引:3,自引:0,他引:3
ERWIN F. SHIBATA Ph.D. TRACY L.Y. BROWN M.D. Ph.D. ZACHARY W. WASHBURN B.S. JING BAI M.S. THOMAS J. REVAK B.S. CAROL A. BUTTERS M.A. 《Journal of cardiovascular electrophysiology》2006,17(S1):S34-S42
Altering voltage-gated ion channel currents, by changing channel number or voltage-dependent kinetics, regulates the propagation of action potentials along the plasma membrane of individual cells and from one cell to its neighbors. Functional increases in the number of cardiac sodium channels (NaV 1.5) at the myocardial sarcolemma are accomplished by the regulation of caveolae by β adrenergically stimulated G-proteins. We demonstrate that NaV 1.5, CaV 1.2a, and KV 1.5 channels specifically localize to isolated caveolar membranes, and to punctate regions of the sarcolemma labeled with caveolin-3. In addition, we show that NaV 1.5, CaV 1.2a, and KV 1.5 channel antibodies label the same subpopulation of isolated caveolae. Plasma membrane sheet assays demonstrate that NaV 1.5, CaV 1.2a, and KV 1.5 cluster with caveolin-3. This may have interesting implications for the way in which adrenergic pathways alter the cardiac action potential morphology and the velocity of the excitatory wave. 相似文献
993.
Fumonisins as a possible contributory risk factor for primary liver cancer: A 3-year study of corn harvested in Haimen, China, by HPLC and ELISA 总被引:13,自引:0,他引:13
Y. Ueno K. Iijima S.-D. Wang Y. Sugiura M. Sekijima T. Tanaka C. Chen S.-Z. Yu 《Food and chemical toxicology》1997,35(12):1143-1150
Employing HPLC fluorometry, gas-liquid chromatography (GLC) and a novel enzymelinked immunosorbent assay (ELISA) based on a monoclonal antibody, 40 corn samples, each collected in 1993 from agricultural stocks for human consumption in Haimen (Jiangsu County) and Penlai (Shandong Province), high- and low-risk areas for primary liver cancer (PLC) in China, respectively, were analysed for fumonisins (FBs), aflatoxins (AFs) and trichothecenes. Levels and positive rates of FBs and deoxynivalenol (DON) were significantly higher in Haimen than in Penlai. ELISA of the 40 corn samples harvested in the two areas in 1994 revealed that FB contamination levels and rates in these areas were comparable to those observed in 1993 in Haimen. ELISA analysis of 1993 and 1994 products revealed a wide occurrence of AFB1 but the positive rates as well as levels were not significantly different between these areas. ELISA of the same sample number of corn harvested in 1995 revealed that FB contamination in Haimen was significantly higher than in Penlai. These 3-yearly surveys of corn samples (240 in total) demonstrated that corn harvested in Haimen was highly contaminated with FBs and that the contamination level, as well as positive rate in 1993 and 1995, were 10–50-fold higher than those in Penlai, suggesting FBs as a risk factor for promotion of PLC in endemic areas, along with the trichothecene DON. Co-contamination with AFs, potent hepatocarcinogens, was assumed to play an important role in the initiation of hepatocarcinogenesis. 相似文献
994.
Benyam Asefa Paul Kauler Denis Cournoyer Shirley Lehnert T. Y.-K. Chow 《Current genetics》1998,34(5):360-367
The deoxyribonucleases (DNases) have been shown genetically to be important in the vital processes of DNA repair and recombination.
The NUD1 gene, which codes for an endo-exonuclease of Saccharomyces cerevisiae, was analyzed for its role in the DNA double-strand break (DSB) repair processes. While the nud1 strain is only slightly sensitive to ionizing radiation, expression of the HO-endonuclease to introduce a DSB at the MAT locus in that strain results in cell death. Cell survival is inversely proportional to the duration of HO-endonuclease expression.
Analysis of the surviving colonies from the nud1 strain indicated that many of the survivors are sterile and that the proportion of these sterile survivors increases with
the time of HO-endonuclease expression. On the other hand, the surviving colonies from the isogenic NUD1 strain are mating-proficient. Interestingly, double mutants of nud1 rad52 are more resistant to ionizing irradiation than the rad52 strain and have a cell-survival fraction of 32% for rad52-1 nud1 and 9% for rad52::URA3 nud1 following prolonged HO-endonuclease expression, indicating that nud1 has a suppressor effect on the DSB-induced lethality in rad52. Polymerase chain reaction analysis showed that many of the nud1 survivors contained small alterations within the MAT locus, suggesting that the survivors arose through the process of non-homologous end-joining. These results suggest that
the endo-exonuclease acts at a DSB to promote DNA repair via the homologous recombination pathway.
Received: 20 July / 20 September 1998 相似文献
995.
The rate of development and time of transfer play different roles in influencing the viability of human blastocysts 总被引:7,自引:6,他引:1
Shoukir Y; Chardonnens D; Campana A; Bischof P; Sakkas D 《Human reproduction (Oxford, England)》1998,13(3):676-681
Improved embryo culture protocols now render more feasible the possibility
of obtaining human blastocysts after in-vitro fertilization. In this study
we present: (i) results of blastocyst development from supernumerary
embryos after co-culture on green monkey kidney epithelial cells and (ii)
pregnancy rates after transfer of frozen blastocysts. In addition, we have
examined the influence of the day of blastocyst freezing and the day of
transfer after the luteinizing hormone (LH) peak on pregnancy and
implantation rates. Of 423 supernumerary embryos, 200 developed to the
blastocyst stage (47.3%). By days 5 and 6, 67% of the blastocysts had
reached the blastocyst stage, and were frozen, compared to 28.5% by day 7.
When we compared the cases where only blastocysts frozen on days 5 and 6
were transferred compared to those frozen and transferred on or after day 7
the pregnancy rates were 7/18 (38.9%) and 1/16 (6.2%) respectively. In
contrast, when we examined the influence of the day of transfer we found
that pregnancies were established from day 5 up to day 9 post LH peak.
Based on these results, we suggest that every attempt should be made to
increase the development rate of supernumerary embryos to the blastocyst
stage, as it appears that the quality of blastocysts transferred, as shown
in this study by rate of development, plays a more crucial role than the
timing of transfer.
相似文献
996.
Association of angiotensin II type 1 receptor gene polymorphism with essential hypertension 总被引:15,自引:0,他引:15
The renin-angiotensin system is involved in control of blood pressure and salt and fluid homeostasis. Genes for components of this system have been of major focus in research on the causation of the common, complex, polygenic trait, essential hypertension (HT). Association of an A→C variant at nucleotide 1166 of the angiotensin II type 1 receptor (AT1 R) gene with HT, but an absence of linkage of this locus with this disease, has been reported recently. Since confirmation in a different setting is imperative, we performed a cross-sectional case-control study of the A1166C variant in a well-characterized group of 108 Caucasian HT subjects with a strong family history (two affected parents) and early onset disease. Genotyping was by mismatch polymerase chain reaction/ Bfr I restriction fragment length polymorphism analysis. Frequency of the C1166 allele was 0.40 in HTs and 0.29 in normotensives. The difference in genotype (χ2 = 13, P = 0.0015) and allele (χ2 = 5.3, P = 0.02) frequencies between the two groups was significant (odds ratio for CC vs AA+AC = 7.3 [95% CI, 1.9–31.9). The present results implicate the AT1 R gene, or a locus in linkage disequilibrium with the variant tested, in the causation of essential HT. 相似文献
997.
Effects of acetaminophen on adverse effects of influenza vaccination in health care workers. 总被引:1,自引:1,他引:0 下载免费PDF全文
F Y Aoki A Yassi M Cheang C Murdzak G W Hammond L H Sekl B Wright 《Canadian Medical Association journal》1993,149(10):1425-1430
OBJECTIVE: To evaluate the effects of acetaminophen on the incidence of adverse effects to, and the immunogenicity of, whole-virus influenza vaccine in health care workers. DESIGN: Prospective, randomized, double-blind placebo-controlled trial. SETTING: Health Sciences Centre, an acute care teaching hospital in Winnipeg. PARTICIPANTS: Of 474 hospital personnel who agreed to undergo influenza vaccination during the 1990-91 season 262 volunteered to participate in the study. INTERVENTIONS: A dose of 0.5 mL of inactivated trivalent whole-virus influenza vaccine was injected into the deltoid muscle. Volunteers were randomly assigned to ingest two capsules of acetaminophen in a half dose (162.5 mg per capsule) or a full dose (325 mg per capsule) or two identical placebo capsules. Capsules were to be taken at vaccination and at 4, 8 and 12 hours afterward. Subjects were asked to answer questions regarding six symptoms in a diary for the 3 days after vaccination and to record their ingestion of the study medication. MAIN OUTCOME MEASURES: Incidence of local (sore arm) and systemic (headache, fever, muscle ache, nausea and diarrhea) side effects as well as serum titres of hemagglutination inhibition (HAI) antibody to vaccine antigens before vaccination and 2 weeks and 6 months afterward. RESULTS: A total of 87, 87 and 88 subjects received the half dose, full dose and placebo respectively; 96% returned the diaries, 83% ingested all four doses of medication, and 87% volunteered all blood samples. Compared with the placebo group the incidence of sore arm was 25% to 28% lower in the half-dose and full-dose groups respectively at 24 hours after vaccination, and the rate of nausea was 90% lower in the full-dose group. The HAI titres were similar among the groups at the three test times. CONCLUSIONS: The full dose of acetaminophen significantly reduced the incidence of sore arm and nausea without affecting the antibody response. Acetaminophen use may increase the acceptance of influenza vaccine by health care workers in whom concern about side effects is an impediment to vaccination. 相似文献
998.
We recorded neurons sensitive to depth movement from the inferior parietal lobule (area 7a) of alert behaving monkeys, and studied their response to changing sizes of retinal images and to changing binocular disparity. The size of the stimulus was changed by changing both the height and width of a slit in the same way, and the disparity change was produced by varying distances between a pair of polarized stimuli on a screen. Of 227 purely visual neurons recorded from 11 hemispheres of 7 monkeys, 32 neurons responded to the change of either the size or disparity, or both. Some of the neurons sensitive to size change could be activated by changing length on only one axis, but the optimal stimulus for most of them was a uniform change of size in all directions. The neurons sensitive to disparity change responded weakly to monocular stimuli, but showed clear selectivity in the direction of change of disparity when binocular stimuli were applied. We also found a group of depth movement sensitive neurons that responded maximally to the simultaneous change of size and disparity. This type of neurons may signal real depth movement by integrating the signals of size change and disparity change. 相似文献
999.
Squamous cell carcinoma of the thyroid--a report of three cases 总被引:1,自引:0,他引:1
A Tsuchiya S Suzuki T Nomizu Y Yamaki R Abe S Katayama 《The Japanese journal of surgery》1990,20(3):341-345
Three cases of squamous cell carcinoma of the thyroid are reported herein. In all cases, the carcinoma occurred in old age and was characterized by a rapidly growing tumor, usually associated with dyspnea and dysphagia. The prognosis of all 3 cases was poor, with a mean survival of only 6.3 months. Although squamous metaplasia is an accepted etiology of this disease, clinical investigation of the cases presented here does not favor it in consideration of the clinical features of papillary carcinoma of the thyroid with squamous metaplasia. The histological findings of our cases revealed areas of cystic formation, suggesting that some of these carcinomas may be derived from remnants of embryonic origin. 相似文献
1000.