全文获取类型
收费全文 | 19203篇 |
免费 | 1201篇 |
国内免费 | 150篇 |
专业分类
耳鼻咽喉 | 226篇 |
儿科学 | 549篇 |
妇产科学 | 677篇 |
基础医学 | 2180篇 |
口腔科学 | 532篇 |
临床医学 | 1492篇 |
内科学 | 3691篇 |
皮肤病学 | 394篇 |
神经病学 | 974篇 |
特种医学 | 694篇 |
外国民族医学 | 11篇 |
外科学 | 3399篇 |
综合类 | 361篇 |
现状与发展 | 3篇 |
一般理论 | 12篇 |
预防医学 | 1660篇 |
眼科学 | 542篇 |
药学 | 1766篇 |
中国医学 | 150篇 |
肿瘤学 | 1241篇 |
出版年
2023年 | 235篇 |
2022年 | 223篇 |
2021年 | 1053篇 |
2020年 | 645篇 |
2019年 | 798篇 |
2018年 | 1067篇 |
2017年 | 626篇 |
2016年 | 653篇 |
2015年 | 670篇 |
2014年 | 924篇 |
2013年 | 1089篇 |
2012年 | 1593篇 |
2011年 | 1714篇 |
2010年 | 975篇 |
2009年 | 724篇 |
2008年 | 1043篇 |
2007年 | 1034篇 |
2006年 | 942篇 |
2005年 | 903篇 |
2004年 | 783篇 |
2003年 | 722篇 |
2002年 | 652篇 |
2001年 | 146篇 |
2000年 | 113篇 |
1999年 | 96篇 |
1998年 | 87篇 |
1997年 | 78篇 |
1996年 | 61篇 |
1995年 | 69篇 |
1994年 | 59篇 |
1993年 | 49篇 |
1992年 | 47篇 |
1991年 | 56篇 |
1990年 | 54篇 |
1989年 | 47篇 |
1988年 | 49篇 |
1987年 | 45篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 42篇 |
1983年 | 37篇 |
1982年 | 36篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The larvicidal activity of the juvenile hormone mimic pyriproxyfen was evaluated against the 4th larval instar of Culex pipiens under 5 constant temperatures in the laboratory. Toxicity of this insect compound increased with temperature. The 50% lethal concentrations ranged between 0.00111 ppm at 20 degrees C and 0.00013 ppm at 32 degrees C. A similar trend was observed for the 90% lethal concentrations, which varied from 0.00379 ppm to 0.00024 ppm at the 2 temperatures, respectively. Some effects of the compound were observed on the ultrastructure of the 4th-stage larval integument, where electron micrographs revealed the destruction of procuticle lamellae, formation of cuticular vacuoles, deformed mitochondria, and destruction of nuclear envelopes and the epidermal layer, in addition to an increase in electron-dense lysosomelike bodies. 相似文献
992.
Rodanant N Friberg TR Cheng L Aurora A Bartsch D Toyoguchi M Corbin PS El-Bradey MH Freeman WR 《American journal of ophthalmology》2002,134(4):577-585
PURPOSE: To determine the predictors of drusen reduction in eyes with nonexudative age-related macular degeneration (ARMD) treated with subthreshold infrared (810 nm) diode laser macular grid photocoagulation. Additionally, to determine the relationship of laser-induced drusen reduction and best-corrected visual acuity (BCVA) 18 months after laser treatment.DESIGN: Randomized controlled clinical trial.METHODS: Fifty patients (100 eyes) with bilateral nonexudative ARMD were enrolled at two centers. One eye of each patient was randomized to the observation; the other eye was treated with 48 subthreshold (invisible end point) applications of infrared (810 nm) diode laser in a macular grid pattern. The eyes that received subthreshold laser treatment were compared with the eyes that received no treatment. The baseline fundus characteristics (number, size, and distribution of drusen, as well as focal hyperpigmentation) from two macula areas (central 1500 micro diameter, pericentral 1500 micro ring area) on stereo color photographs, the number of laser-induced lesions, and the area of laser induced retinal pigment epithelial (RPE) lesions on fluorescein angiography 3 months after treatment were studied as predictors of major drusen reduction (> or = 50% drusen reduction from baseline) 18 months after laser treatment. BCVA at baseline and 18 months later was compared in observation eyes and in laser-treated eyes.RESULTS: Eighteen months after randomization, 24 (48%) of 50 eyes treated with subthreshold laser had major drusen reduction compared with three (6%) of 50 observation eyes (P =.00001). At 3 months post-treatment in laser-treated eyes with major drusen reduction, the mean number of laser-induced lesions on fluorescein angiography was 30.7 and the mean area of RPE change was 0.81 mm(2) compared with 14.8 laser-induced lesions and 0.35 mm(2) area of RPE change in eyes without major drusen reduction (P =.0001 and P =.0003, respectively). At baseline, fundus characteristics were not significantly different between observation eyes and laser-treated eyes or between the major drusen reduction group and the nonmajor drusen reduction group. At 18 months after treatment, BCVA was not significantly different in laser-treated eyes and in observation eyes.CONCLUSIONS: Subthreshold infrared (810 nm) diode laser macular grid photocoagulation in eyes with nonexudative ARMD significantly reduced drusen 18 months after laser treatment. Both the number of subthreshold laser lesions and the area of RPE changes visible on fluorescein angiography 3 months after treatment appeared to be predictors for major drusen reduction 18 months after treatment. However, it remains to be determined whether laser-induced drusen reduction is beneficial for visual acuity or reduces the incidence of choroidal neovascularization (CNV) in eyes with nonexudative ARMD. 相似文献
993.
Hilal L Nandrot E Belmekki M Chefchaouni M El Bacha S Benazzouz B Hajaji Y Gribouval O Dufier J Abitbol M Berraho A 《Ophthalmic genetics》2002,23(4):199-208
Autosomal dominant cerulean cataracts (ADCC) have previously been mapped to two loci: one on chromosome 17q24 and the other on chromosome 22q11.2-q12.2, which includes the beta-B2 crystallin (CRYBB2) candidate gene. Using polymorphic markers in these regions (D17S802, D17S836, D17S1806 and CRYBB2, D22S258) for linkage analysis, we excluded these loci in a large Moroccan family presenting with an unusual form of ADCC with early onset of lens opacities and rapid evolution. This finding confirms the clinical and genetic heterogeneity of autosomal dominant congenital cerulean cataracts. 相似文献
994.
Khayyal MT el-Ghazaly MA Abdallah DM Nassar NN Okpanyi SN Kreuter MH 《Arzneimittel-Forschung》2002,52(11):797-802
A specially prepared olive leaf extract (EFLA 943) has been tested for its blood pressure lowering activity in rats rendered hypertensive by daily oral doses of L-NAME (NG-nitro-L-arginine methyl ester, 50 mg/kg) for at least 4 weeks. Oral administration of the extract at different dose levels at the same time as L-NAME for a period of 8 weeks showed a dose dependent prophylactic effect against the rise in blood pressure induced by L-NAME, best effects being induced by a dose of 100 mg/kg of the extract. In rats previously rendered hypertensive by L-NAME for 6 weeks and then treated with that dose of the extract for a further 6 weeks without discontinuation of L-NAME, normalisation of the blood pressure was observed. The findings confirm previous reports on the hypotensive effects of olive leaf. The special extract, EFLA 943, was shown to give consistent results with little individual variability. The antihypertensive effect of the extract may be related to a variety of factors involving reversal of vascular changes involved in the L-NAME induced hypertension. 相似文献
995.
Ahmed AA Mohamed Ael-H Tzakou O Gani A Yannitsaros A El-Maghraby MA Hassan ME Zeller KP 《Planta medica》2002,68(7):664-666
Three new pyrone glucosidic derivatives, together with the known pyromeconic acid glucoside, three acytelenes and two eudesmanes, were obtained from the aerial parts of Conyza albida. The structures were elucidated by high field NMR spectroscopy. 相似文献
996.
Weick JK Crowley JJ Hussein MA Moore DF Barlogie B;Southwest Oncology Group 《Investigational new drugs》2002,20(1):117-121
Gemcitabine is a cytosine arabinoside(Ara-C) analog with activity in many humantumor systems. We evaluated the drug'sactivity in resistant or relapsing multiplemyeloma. Gemcitabine 1000 mg/m2 wasadministered as a 30 minute infusion ondays 1, 8, and 15 of a 28-day cycle. Nodose escalations were permitted and dosereductions were scheduled for hematologictoxicity. Twenty-nine eligible patientswere entered into Southwest Oncology Group(SWOG)-9803. One patient received notreatment and 5 patients had inadequateresponse assessments. The major toxicitywas hematologic with grade 3/4 neutropeniain 9 and grade 3/4 thrombocytopenia in 15patients. No responses were seen. Stabledisease was confirmed in sixteen patients(57%). Median survival was eight months. Gemcitabine as utilized in this trial hasshown little activity and is not to bestrongly considered for future multiplemyeloma trials. 相似文献
997.
A series of benzimidazole Schiff's bases, thiosemicarbazides were synthesized, azole ring systems as 1,3,4-triazole, 1,3,4-oxadiazole were prepared. 1-Methylbenzimidazole incorporated to substituted dithio-carbamate, thiophenol, diethylamine via acetamido group were synthesized. A series of pyrimidinobenzimidazoles, triazinobenz-imidazoles, and 2-(acetonylamino)-1-methylbenzimidazole were prepared. The antimicrobial and molluscicidal activities of some newly prepared compounds were carried out. 相似文献
998.
Recently, several studies have reported on the health and environmental consequences of the use of depleted uranium. Depleted uranium is a heavy metal that is also radioactive. It is commonly used in missiles as a counterweight because of its very high density (1.6 times more than lead). Immediate health risks associated with exposure to depleted uranium include kidney and respiratory problems, with conditions such as kidney stones, chronic cough and severe dermatitis. Long-term risks include lung and bone cancer. Several published reports implicated exposure to depleted uranium in kidney damage, mutagenicity, cancer, inhibition of bone, neurological deficits, significant decrease in the pregnancy rate in mice and adverse effects on the reproductive and central nervous systems. Acute poisoning with depleted uranium elicited renal failure that could lead to death. The environmental consequences of its residue will be felt for thousands of years. It is inhaled and passed through the skin and eyes, transferred through the placenta into the fetus, distributed into tissues and eliminated in urine. The use of depleted uranium during the Gulf and Kosovo Wars and the crash of a Boeing airplane carrying depleted uranium in Amsterdam in 1992 were implicated in a health concern related to exposure to depleted uranium. 相似文献
999.
Omran AA Kitamura K Takegami S Kume M Yoshida M El-Sayed AA Mohamed MH Abdel-Mottaleb M 《Journal of pharmaceutical and biomedical analysis》2002,30(4):1087-1092
A simple 19F NMR spectrometric method was proposed for the determination of the partition coefficients of fluorinated psychotropic drugs, trifluoperazine (TFPZ), flunitrazepam (FNZ) and flurazepam (FZ) between phosphatidylcholine (PC) bilayer of small unilamellar vesicles (SUVs) and water (buffer). Each 19F NMR spectrum of these drugs in the presence of PC SUV showed a single signal accompanying a PC concentration-depending shift change and broadening, which indicated a fast exchange of these drugs between the water phase and the PC bilayer of SUV. From the relationship between the 19F chemical shift change (Deltadelta) of each drug and the PC concentration, the molar partition coefficients (K(p)'s) were calculated and obtained with a good precision of RSD below 6%. The fractions of the partitioned drugs calculated by using the obtained K(p)-values were in a good agreement with the experimental values. The results demonstrate that the 19F NMR method can be usefully applied to the determination of partition coefficients of many drugs having fluorine atom(s) without any separation procedure, especially for drugs which do not have absorption in the ultraviolet or visible region, or those having absorption but show insignificant spectral changes according to their incorporation to PC bilayers (e.g. FNZ). 相似文献
1000.
Rural health care in Malaysia 总被引:1,自引:0,他引:1
ABSTRACT: Malaysia has a population of 21.2 million of which 44% resides in rural areas. A major priority of healthcare providers has been the enhancement of health of 'disadvantaged' rural communities particularly the rural poor, women, infants, children and the disabled. The Ministry of Health is the main healthcare provider for rural communities with general practitioners playing a complimentary role. With an extensive network of rural health clinics, rural residents today have access to modern healthcare with adequate referral facilities. Mobile teams, the flying doctor service and village health promoters provide healthcare to remote areas. The improvement in health status of the rural population using universal health status indicators has been remarkable. However, differentials in health status continue to exist between urban and rural populations. Malaysia's telemedicine project is seen as a means of achieving health for all rural people. 相似文献