首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   53383篇
  免费   4345篇
  国内免费   1586篇
耳鼻咽喉   621篇
儿科学   670篇
妇产科学   1116篇
基础医学   8258篇
口腔科学   1415篇
临床医学   4435篇
内科学   10335篇
皮肤病学   1017篇
神经病学   3874篇
特种医学   1765篇
外国民族医学   6篇
外科学   7506篇
综合类   3971篇
现状与发展   1篇
一般理论   6篇
预防医学   3038篇
眼科学   1398篇
药学   4745篇
中国医学   756篇
肿瘤学   4381篇
  2023年   198篇
  2022年   331篇
  2021年   569篇
  2020年   357篇
  2019年   646篇
  2018年   1159篇
  2017年   884篇
  2016年   880篇
  2015年   989篇
  2014年   1314篇
  2013年   1620篇
  2012年   2198篇
  2011年   2160篇
  2010年   1296篇
  2009年   1277篇
  2008年   1890篇
  2007年   2001篇
  2006年   1865篇
  2005年   1537篇
  2004年   1410篇
  2003年   1379篇
  2002年   1316篇
  2001年   4668篇
  2000年   4586篇
  1999年   3957篇
  1998年   1382篇
  1997年   1004篇
  1996年   616篇
  1995年   508篇
  1994年   457篇
  1993年   418篇
  1992年   1952篇
  1991年   1691篇
  1990年   1550篇
  1989年   1504篇
  1988年   1310篇
  1987年   1206篇
  1986年   1078篇
  1985年   907篇
  1984年   589篇
  1983年   471篇
  1982年   250篇
  1981年   181篇
  1980年   144篇
  1979年   285篇
  1978年   80篇
  1974年   78篇
  1973年   97篇
  1972年   74篇
  1969年   68篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
In order to ascertain the adequacy of ovarian stimulation protocols with a type of follicular puncture, 126 women undergoing in vitro fertilization received either combination clomiphene/hMG or hMG alone according to a randomized test protocol. Within both groups patients for whom a pelvic examination was required had laparoscopies, while others had transvaginal ultrasonically guided punctures as far as possible. Clomiphene/hMG was more efficient than hMG alone as assessed from the cleavage rate (68% vs. 54%; p less than 0.01) and the pregnancy per attempt rate (16% vs. 5%; p less than 0.05). Laparoscopic punctures were more efficient than ultrasonically guided punctures (mean number of recovered oocytes: 4.8 +/- 2.6 vs. 3 +/- 2.5; p less than 0.001), but slightly better results were achieved by this latter method in ongoing pregnancy per puncture rate (18% vs. 8%; NS). With ultrasonically guided punctures, stimulation by clomiphene/hMG allowed better oocyte recoveries (3.8 +/- 2.5 vs. 2.3 +/- 1.9, p less than 0.05). Such results constitute an argument for preferential use of the clomiphene/hMG stimulation protocol with ultrasonically guided punctures.  相似文献   
12.
The effects of intracellular Ca2+ (Ca2+i) on K+ currents in hippocampal cells were examined using acutely isolated cells obtained from adult guinea pigs. Whole-cell voltage-clamp recordings were carried out in a configuration that allowed a continuous perfusion of the intracellular medium. Recording media were made to block inward currents and allowed selective activation of K(+)-dependent outward currents. Voltage-dependent outward currents consisted of an initial rapidly decaying component followed by a sustained component. The time constant of decay of the transient current was about 25 msec, and previous studies (Numann et al., 1987) showed that the kinetic and pharmacological properties of this current closely resembled the A current recorded in invertebrate neurons (Connor and Stevens, 1971; Thompson, 1982). Intracellular perfusion of hippocampal cells with a solution containing elevated Ca2+ (about 4.5 x 10(-4) M) elicited outward currents at the holding potential (-45 to -55 mV) and produced changes in voltage-dependent K+ currents. The transient outward current (IA) activated by depolarization was suppressed with increases in Ca2+i. Delayed, sustained K+ currents were greatly potentiated. Data also showed that, among the 3 effects elicited by Ca2+i, suppression of IA was most sensitive to Ca2+i elevation. Previous results (Numann et al., 1987) showed that IA had a lower threshold (about -45 mV) than sustained currents (about -40 mV). By using low levels of depolarization (-40 mV), IA can be selectively activated, and the suppressive effect of Ca2+i on IA was confirmed on the kinetically isolated IA.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
13.
14.
Experience in the treatment of 30 cases with gas gangrene from war wounds   总被引:1,自引:0,他引:1  
Z Y Li  X L Wang  X S Wang 《中华外科杂志》1986,24(10):580-1, 637
  相似文献   
15.
When blood flow through the internal and external carotid arteries is completely interrupted by ipsilateral common carotid artery occlusion, the arterial orbital circulation may be more compromised than the brain supply. We studied a pure and extreme example of this situation in a patient who presented with acute orbital infarction, but no cerebral ischemia on clinical, CT and single-photon emission computerized tomography (SPECT) grounds. Ipsilateral blindness corresponded to retinal, choroidal and optic nerve infarction. The pattern of ophthalmoplegia, with relative sparing of adduction, was more compatible with a muscle than a nerve dysfunction, but a reactive dilated pupil, corneal anesthesia, and orbital pain suggested that the intraorbital branches of the ocular motor nerves and ophthalmic division of the trigeminal nerve were not spared. In addition, signs of widespread ocular ischemia were present. Sequential examinations documented the evolution pattern over 1 year. The absence of an orbital collateral supply from the contralateral external carotid and muscular cervical arteries systems, which contrasted with an adequate middle cerebral artery supply via the contralateral internal carotid artery, may explain this isolated and complete form of orbital ischemia due to common carotid artery occlusion.  相似文献   
16.
17.
X Dong  M He  X Song  B Lu  Y Yang  S Zhang  N Zhao  L Zhou  Y Li  X Zhu  R Hu 《Diabetic medicine》2007,24(12):1482-1486
AIMS: Our aim was to assess performances of the Cockcroft-Gault and simplified Modification of Diet in Renal Disease (MDRD) formulae in estimating glomerular filtration rate (GFR) in Chinese diabetic populations and their association with vascular risks. METHODS: A total of 1009 patients with Type 2 diabetes were categorized into low estimated GFR groups (GFR < 60 ml/min/1.73 m(2)) and control groups by the two equations. The performances of these formulae were assessed at different stages of kidney function. Carotid artery intima-media thickness (IMT) and the prevalence of diabetic retinopathy or albuminuria were compared among the groups. The ability of these formulae to identify established vascular risk markers using sensitivity, specificity, positive and negative predictive values were also compared. RESULTS: The prevalence of low estimated GFR was 32.7% with the Cockcroft-Gault formula and 5.2% with the MDRD formula, respectively. In low estimated GFR subjects by the MDRD formula, IMT was significantly thicker than those by the Cockcroft-Gault formula (1.2 mm vs. 1.0 mm; P < 0.05), with a higher prevalence of albuminuria (78.4 vs. 52.8%, P < 0.05) and diabetic retinopathy (46.5 vs. 30.5%; P < 0.05). The Cockcroft-Gault formula gave a specificity of 71.7% and a sensitivity of 37.0%, and the MDRD formula gave a specificity of 96.6% and a sensitivity of 7.9% in estimating low GFR relevant for established vascular risks. CONCLUSIONS: These formulae performed differently in Chinese diabetic populations. The simplified MDRD formula is minimally superior to the Cockcroft-Gault formula for its high specificity and positive predictive values in estimating low GFR relevant for vascular risks.  相似文献   
18.
The authors reviewed the radiographic manifestations of 17 cases of parosteal osteosarcoma, with pathologic correlation in 15. There were two types of parosteal osteosarcoma radiologically. The majority of cases were type I with uniformly dense masses which had regular borders. They often adhered to the cortex and showed no evidence of soft-tissue invasion which correlated with low-grade pathologic malignancy and a relatively benign clinical course. Type II involved the bone, soft-tissue and the medullary cavity. These lesions were poorly differentiated and frequently accompanied by metastatic lesions.
  相似文献   
19.
20.
The effects of some antirheumatics on the formation and retraction of collagen lattices seeded with fibroblasts have been studied. Among the antirheumatics, diclofenac was the most active inhibitor of lattice retraction, then tropesin and to a lesser extent indomethacin. Ibuprofen which is known as a very slight inhibitor of protein synthesis was able to significantly enhance lattice retraction when 10 micrograms/ml (48.5 microM) and 50 micrograms/ml (242 microM) were used.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号