全文获取类型
收费全文 | 33560篇 |
免费 | 1902篇 |
国内免费 | 207篇 |
专业分类
耳鼻咽喉 | 441篇 |
儿科学 | 674篇 |
妇产科学 | 768篇 |
基础医学 | 4087篇 |
口腔科学 | 1664篇 |
临床医学 | 2535篇 |
内科学 | 7933篇 |
皮肤病学 | 567篇 |
神经病学 | 3236篇 |
特种医学 | 1048篇 |
外国民族医学 | 1篇 |
外科学 | 4751篇 |
综合类 | 150篇 |
一般理论 | 8篇 |
预防医学 | 2308篇 |
眼科学 | 544篇 |
药学 | 2392篇 |
中国医学 | 136篇 |
肿瘤学 | 2426篇 |
出版年
2023年 | 300篇 |
2022年 | 753篇 |
2021年 | 1225篇 |
2020年 | 742篇 |
2019年 | 995篇 |
2018年 | 1155篇 |
2017年 | 869篇 |
2016年 | 945篇 |
2015年 | 1070篇 |
2014年 | 1369篇 |
2013年 | 1851篇 |
2012年 | 2558篇 |
2011年 | 2657篇 |
2010年 | 1448篇 |
2009年 | 1327篇 |
2008年 | 1993篇 |
2007年 | 1965篇 |
2006年 | 1751篇 |
2005年 | 1668篇 |
2004年 | 1537篇 |
2003年 | 1283篇 |
2002年 | 1161篇 |
2001年 | 527篇 |
2000年 | 466篇 |
1999年 | 396篇 |
1998年 | 251篇 |
1997年 | 222篇 |
1996年 | 176篇 |
1995年 | 155篇 |
1994年 | 138篇 |
1993年 | 124篇 |
1992年 | 256篇 |
1991年 | 226篇 |
1990年 | 230篇 |
1989年 | 189篇 |
1988年 | 159篇 |
1987年 | 124篇 |
1986年 | 155篇 |
1985年 | 119篇 |
1984年 | 106篇 |
1983年 | 95篇 |
1982年 | 82篇 |
1981年 | 62篇 |
1980年 | 64篇 |
1979年 | 101篇 |
1978年 | 55篇 |
1977年 | 53篇 |
1975年 | 52篇 |
1974年 | 50篇 |
1973年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
β-N-Acetylhexosaminadases in human cerebrospinal fluid and serum of patients with multiple sclerosis
Alessandro Datti Carla Emiliani Giuseppe Capocchi Aldo Orlacchio 《Clinica chimica acta; international journal of clinical chemistry》1991,200(2-3)
β-N-Acetylhexosaminidase activity and isoenzyme have been investigated in normal human cerebrospinal fluid and that of patients with multiple sclerosis. β-N-acetylhexosaminidase activity in normal cerebrospinal fluids has been resolved into five components. The major component was in a form that eluted from DEAE cellulose at the same salt concentration as hexosaminidase As, the isoenzyme previously identified in human serum. Cerebrospinal fluid from patients exhibited a different isoenzyme profile, showing a remarkable increase in a form having a pI which was more acidic than that of As. These changes have a potential use in the diagnosis and further biochemical characterization of multiple sclerosis. 相似文献
92.
Paolo Ambrosetto Stefano Zucchini Alessandro Cicognani Emanuele Cacciari 《Pediatric radiology》1998,28(5):288-289
A girl with Diamond-Blackfan syndrome and hypopituitarism was suspected of having pituitary haemosiderosis because of the
clinical picture and the long history of blood transfusions. On T1-weighted MR images the pituitary exhibited a markedly hypointense
anterior lobe (mimicking the empty sella), suggesting iron deposition, while on T2W MRI the low signal of the pituitary was
surrounded by the high signal of the CSF. MR may be considered the examination of choice for detecting iron overload in the
pituitary.
Received: 10 November 1997 Accepted: 21 November 1997 相似文献
93.
Emanuele Lezoche M.D. Alessandro M. Paganini M.D. Ph.D. Francesco Carlei M.D. Francesco Feliciotti M.D. Davide Lomanto M.D. Ph.D. Mario Guerrieri M.D. 《World journal of surgery》1996,20(5):535-542
n
= 2), port site infection (
n
= 2), and subumbilical hematoma (
n
= 1). Major morbidity was bile leakage from the cystic duct stump in two cases due to clips or transcystic duct drainage displacement,
respectively. One elderly, high risk patient died after being referred for several failed attempts of endoscopic clearance;
she died from cardiogenic shock 3 days after successful laparoscopic treatment. Laparoscopic CBD exploration is feasible and
safe in most patients, with short-term results that compare favorably with the results of sequential ES/LC reported in the
literature. 相似文献
94.
Teresa Coccini Luciano Maestri Francesco S. Robustelli della Cuna L. Bin Lucio G. Costa Luigi Manzo 《Archives of toxicology》1996,70(11):736-741
Styrene is stereoselectively oxidized by cytochrome P450 to its reactive metabolite, styrene oxide. The (R)- and (S)-enantiomers
of styrene oxide can be conjugated with glutathione (GSH) to both (R)- and (S)-diastereoisomers of the specific mercapturic
acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine (M1) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine (M2). Several investigations have indicated different toxic potential of the (R)- and (S)-configurations of styrene
oxide and its GSH- and N-acetyl-conjugates. In this study the mercapturic acid diastereoisomers were measured in the urine
of rats exposed to styrene in combination with ethanol, a good inducer of styrene metabolism. Male Sprague-Dawley rats were
given an isocaloric liquid diet containing ethanol (5% w/v) for 3 weeks. Starting from the 2nd week, the animals were also
exposed to styrene vapours (300 ppm, 6 h/day, 5 days/week) in a dynamic exposure chamber. Both the (R)- and (S)-diastereoisomers
of the M1 and M2 as well as the conventional biomarkers, mandelic acid (MA) and phenylglyoxylic acid (PGA) were measured in
urinary samples. Approximately 30 and 25% reduction of the levels of brain non-protein sulfhydryls (NPS) was observed in the
animals given styrene and ethanol, respectively, while the combined ethanol and styrene treatment resulted in a 60% decrease.
Ethanol consumption also resulted in higher urinary levels of the M1-R, M1-S and M2 metabolites associated with increased
M1-R/S ratio and higher urinary MA excretion compared to animals treated with styrene. These results suggest that the urinary
mercapturic acid diastereoisomers may be used as a noninvasive tool to examine stereoselective patterns of styrene metabolism
in vivo, as well as their alterations caused by ethanol. These compound-specific mercapturic acids may also be valuable indicators
of styrene-induced disorders of GSH homeostasis in nonaccessible organs.
Received: 19 December 1995/Accepted: 10 May 1996 相似文献
95.
Bongertz Costa Guimarães Grinsztejn The Hec/fiocruz Aids Clinical Research Group João Filho Galvão-Castro & Morgado 《Scandinavian journal of immunology》1998,47(6):603-608
Susceptibility to autologous and heterologous neutralization of primary human immunodeficiency virus (HIV)-1 isolates belonging to subtype B, to the B'-variant of subtype B or to subtype F from infected individuals residing in Rio de Janeiro was assayed. A lower infectivity of the B'- and F isolates when compared to the classical B-subtype HIV-1 isolates was observed. Comparisons of neutralization susceptibilities were carried out for 19 B-subtype, 11 B'-variant and two F-subtype HIV-1 isolates with plasma from autologous and heterologous samples. Frequency of autologous neutralization was slightly lower for B-subtype isolates in comparison to B'-variant isolates. Heterologous intra-subtype neutralization was significantly lower for B-subtype than for the B'-variant or the F-subtype isolates. While B-subtype isolates were neutralized by most anti-F-subtype plasma, F-subtype isolates, although most susceptible to F-subtype antibodies, were highly susceptible to neutralization by anti-B-subtype antibodies. Cross-neutralization for B'-variant and B-subtype isolates was not as extensive as observed for B- and F-subtype isolates. However, the results presented indicate a quite extensive cross-neutralization between Brazilian HIV-1 isolates. 相似文献
96.
Laura Santambrogio Maria Lipartiti Alessandro Bruni Roberto Dal Toso 《Journal of neuroimmunology》1993,45(1-2)
The presence of functional dopamine receptors on differentiated cells of the mammalian immune system is still under discussion. This study has utilized (-)-[3H]sulpride as a ligand to detect the presence of recognition sites of the dopamine D2 receptor family on human T- and B-lymphocytes. The (-)-[3H]sulpiride binding was of high affinity (Kd 0.9 nM ± 0.2 nM, specific, saturable (Bmax 10.2 ± 1.4 fmol/106 cells) and reversible. The pharmacological characterization of the recognition site suggests, similarities mainly with the D2 and D4 rather than D3 subtype of dopamine receptor. Furthermore, dopamine treatment was able to reduce the intracellular cAMP levels of lymphocytes stimulated with forskolin, thus suggesting a potential functional significance of this dopamine receptor in mediating neural-immune interactions. 相似文献
97.
R B Rothman V Bykov A Reid B R De Costa A H Newman A E Jacobson K C Rice 《Neuropeptides》1988,12(3):181-187
Norbinaltorphimine (nor-BNI) is a bifunctional reagent developed as a selective antagonist of the kappa opioid receptor. In this paper we examined the in vitro selectivity of nor-BNI, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY), and the enantiomer of cycloFOXY, among opioid receptor subtypes. Nor BNI exhibited the highest affinity for kappa binding sites labeled by 3H-U69593 (Ki = 1.8nM), and was 27- to 29-fold less potent at mu and delta binding sites. In contrast, cycloFOXY had the highest affinity for mu binding sites (Ki = 2.62 nM), and bound to kappa and delta binding sites with Ki's of 9.3 nM and 89 nM, respectively. The enantiomer of cycloFOXY, did not inhibit binding even at concentrations greater than 10 microM, validating in part the use of 18F-labeled (+)-cycloFOXY to estimate "non-specific binding" in positron emission tomography. Additionally, we report that (S,S)-U50 488 and (R.R)-U50 488 bind to kappa binding sites labeled by 3H-U69 593 with Ki's of 0.89 nM and 299 nM, respectively. 相似文献
98.
The no-scalpel vasectomy technique, introduced by a Chinese surgeon in 1974, is increasingly becoming the method of choice for permanent male sterilization. Conventional vasectomy is being challenged by the new procedure, which results in less pain, fewer infections, and a smaller wound. The use of 2 specially designed instruments lessens tissue damage from the procedure and reduces time required for the operation. In the United States, Dr. Mark Goldstein of Cornell Medical Center, New York City, has instructed surgeons in the no-scalpel technique. The Association for Voluntary Surgical Contraception has also promoted no-scalpel vasectomy, which is gaining popularity among urologists worldwide. The procedure was developed in China by Dr. Li Shunquiang of the Chongquing Family Planning Scientific Research Institute and has been performed on over 8 million men. Statistics reveal that this method produces a smaller singular incision and also reduces postoperative infection and hematoma. In China, the rate of hematoma in 179,741 men was 0.09% and the rate for infections was 0.91%. In a New York study, 238 men had no evidence of infection or hematoma following no-scalpel vasectomy. Since the technique was introduced in 1974, urologic surgeons have responded to the need to offer alternatives for male contraception. Under the direction of Dr. Shunquiang, surgeons received the necessary training to bring the no-scalpel vasectomy to their respective countries. Dr. Marc Goldstein was the first United States urologic surgeon to be trained in this method. By December 1990, data reported by the Association for Voluntary Surgical Contraception revealed that more than 125 United States physicians were trained in no-scalpel vasectomy. This new option is becoming an increasingly popular method for both patients and urologic surgeons. 相似文献
99.
100.
It was reviewed a series of 2860 cerebral computed tomography (CCT) in order to compare the main reasons at referral to investigation with the CCT results and the costs with normal and abnormal CCT. It was also studied the age and sex of the patients. Data were collected from one out of three diagnostic centers in Salvador, Brasil, for a three years period. The 2860 CCT exclude all investigation carried out for the follow-up of a previously diagnosed abnormality. CCT abnormalities were detected in 1152 (40.3%). The following reasons showed the highest proportion of abnormal CCT, for males and females respectively: demential syndrome (91.7 and 83.3%); cerebrovascular accidents (85.1 and 73.6%); infectious and parasitary diseases (76.5 and 78.6%); tumors (65.8 and 55.4%); and head injuries, 63.6% for males. In the female group, 65.0% of the CCT were normal, in a range of 65.0 to 80.0% for the age groups under 54 years old. In the male group, the highest proportion of normal CCT was found in the age groups: 25-34 (68.4%), < 15 (62.9%) and 35-44 (62.7%). The most common reasons for normal CCT for males and females were: headache (81.3 and 87.5%); dizziness/vertigo (79.3 and 78.6%); seizures (67.3 and 70.0%); psychomotor deficiency (72.0 and 67.7%) and "endocrine disorders", 75.0% for each sex. The highest proportion of normal CCT (65.3%) was requested by medical "convenios". The cost with normal CCT reached US$565,225 and with the abnormal ones, US$381,247. Costs with normal CCT were 2.2 higher for medical "convenios" as compared to those of the National Institute of Security requests and 2.8 more than those of private medicine. 相似文献