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   4667篇
  免费   321篇
  国内免费   16篇
耳鼻咽喉   71篇
儿科学   134篇
妇产科学   98篇
基础医学   663篇
口腔科学   411篇
临床医学   350篇
内科学   953篇
皮肤病学   88篇
神经病学   288篇
特种医学   166篇
外科学   596篇
综合类   35篇
预防医学   576篇
眼科学   61篇
药学   318篇
中国医学   52篇
肿瘤学   144篇
  2023年   43篇
  2022年   111篇
  2021年   178篇
  2020年   104篇
  2019年   149篇
  2018年   174篇
  2017年   108篇
  2016年   141篇
  2015年   175篇
  2014年   232篇
  2013年   236篇
  2012年   375篇
  2011年   420篇
  2010年   217篇
  2009年   172篇
  2008年   290篇
  2007年   244篇
  2006年   214篇
  2005年   206篇
  2004年   182篇
  2003年   143篇
  2002年   139篇
  2001年   113篇
  2000年   89篇
  1999年   56篇
  1998年   25篇
  1997年   17篇
  1996年   12篇
  1995年   15篇
  1994年   22篇
  1992年   42篇
  1991年   30篇
  1990年   26篇
  1989年   25篇
  1988年   25篇
  1987年   28篇
  1986年   16篇
  1985年   21篇
  1984年   18篇
  1983年   20篇
  1982年   14篇
  1981年   7篇
  1980年   9篇
  1979年   16篇
  1978年   12篇
  1973年   11篇
  1971年   8篇
  1970年   10篇
  1968年   8篇
  1967年   6篇
排序方式: 共有5004条查询结果,搜索用时 62 毫秒
51.
R Dias  J N Ward 《Urology》1978,11(4):393-394
When suspected ectopic ureters cannot be visualized by conventional methods, such as excretory urogram, nephrotomograms, or by intravenous indigo carmine, then direct injection of vaginal, suburethral, or paraurethral "swellings," which are in effect dilated terminal ureters, may confirm the diagnosis.  相似文献   
52.
The effectiveness of all presently employed cancer therapies is limited by tumour cell heterogeneity. In patients with rhabdomyosarcomas (RMS), differentiation seemed to be associated with poor prognosis and vice versa. In order to confirm the validity of this observation, we have developed in vitro and in vivo models of RMS wherein the degree of tumour cell differentiation could be manipulated. On subcutaneous implantation in nude mice, 4 of 8 alveolar rhabdomyosarcomas (A-RMS), produced tumours. In 3 of these 4 tumours the N- myc gene was amplified. In contrast, 2 embryonal (E-RMS) lacked N-myc amplification and also failed to grow in nude mice. Two cell lines from E-RMS formed tumours in nude mice. In vitro, a reduction in bovine serum concentration or supplementation of the medium with horse serum induced marked differentiation in an A-RMS but not in an E-RMS. In vivo, subcutaneous xenografts of undifferentiated A-RMS could be induced to differentiate by intratumoural injection of horse serum or transplantation into the peritoneal cavity of rats. This dramatic degree of differentiation was detected by histology and immunocytochemical staining using 3 different markers, viz, desmin, vimentin and myoglobin. Somewhat remarkably, when these differentiated A-RMS growing in the peritoneal cavities of rats, were reinplanted into peritoneal cavities of other rats they failed to grow. On the other hand, if they were reimplanted subcutaneously in other rats they grew well and reverted to an undifferentiated morphology. In contrast, the E-RMS could not be induced to undergo differentiation by horse serum and also failed to grow in the peritoneal cavity of rats.  相似文献   
53.
The evolution of the concepts and practice of occupational medicine, occupational health and workers' health is tentatively reviewed. An attempt is made to answer the following questions: what were the major characteristics of occupational medicine throughout its evolution? How and why did occupational medicine evolve into occupational health? Why has the "occupational health model" become inadequate? Within what context did workers' health arise? What are the principal characteristics of workers' health?  相似文献   
54.
This is an assessment of three different outcome measures for the hand: the Hand Clinic Questionnaire (HCQ); the Patient Evaluation Measure (PEM); and the Hand Outcome Survey Sheet (HOSS). Each measure has been tested for its reliability and validity. The results suggest that the PEM and the HCQ are comparably consistent but the PEM is more reproducible. Both the PEM and HOSS are valid questionnaires. The PEM is suitable for use in an outpatient clinic and as a postal questionnaire. The HOSS may be used for research or audit especially when the injury has been measured using the Hand Injury Severity Score.  相似文献   
55.
Long-term exposure to low levels of organophosphate pesticides (OP) may produce neuropsychiatric symptoms. We performed clinical, neuropsychiatric, and laboratory evaluations of 37 workers involved in family agriculture of tobacco from southern Brazil who had been exposed to OP for 3 months, and in 25 of these workers, after 3 months without exposure to OP. Plasma acetylcholinesterase activity levels of all subjects were within the normal range (3.2 to 9.0 U/l) and were not different between on- and off-exposure periods (4.7 +/- 0.9 and 4.5 +/- 1.1 U/l, respectively). Clinically significant extrapyramidal symptoms were present in 12 of 25 subjects, which is unexpected in such a population. There was a significant reduction of extrapyramidal symptoms after 3 months without exposure to OP, but 10 subjects still had significant parkinsonism. Mini-mental and word span scores were within the expected range for this population and were not influenced by exposure to OP. Eighteen of the 37 subjects (48%) had current psychiatric diagnoses in the first interview (13 with generalized anxiety disorder and 8 with major depression). Among the 25 subjects who completed both evaluations, the total number of current psychiatric diagnoses, after 3 months without using OP, dropped from 24 to 13 and the number of affected individuals with any psychiatric diagnosis dropped from 11 to 7. In conclusion, this study reinforces the need for parameters other than acetylcholinesterase activity to monitor for chronic consequences of chronic low-dose OP exposure, and it suggests that subjects have not only transient motor and psychiatric consequences while exposed, but may also develop enduring extrapyramidal symptoms.  相似文献   
56.
57.
Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) have been implicated in promoting solid tumor growth and metastasis via stimulating tumor-associated angiogenesis. We recently showed that certain 'liquid' tumors such as leukemia not only produce VEGF, but also express functional VEGFR, resulting in an autocrine loop for tumor growth and propagation. A chimeric anti-VEGFR2 (or kinase insert domain-containing receptor, KDR) antibody, IMC-1C11, was shown to be able to inhibit VEGF-induced proliferation of human leukemia cells in vitro, and to prolong survival of nonobese diabetic-severe combined immune deficient (NOD-SCID) mice inoculated with human leukemia cells. Here we produced two fully human anti-KDR antibodies (IgG1), IMC-2C6 and IMC-1121, from Fab fragments originally isolated from a large antibody phage display library. These antibodies bind specifically to KDR with high affinities: 50 and 200 pM for IMC-1121 and IMC-2C6, respectively, as compared to 270 pM for IMC-1C11. Like IMC-1C11, both human antibodies block VEGF/KDR interaction with an IC(50) of approximately 1 nM, but IMC-1121 is a more potent inhibitor to VEGF-stimulated proliferation of human endothelial cells. These anti-KDR antibodies strongly inhibited VEGF-induced migration of human leukemia cells in vitro, and when administered in vivo, significantly prolonged survival of NOD-SCID mice inoculated with human leukemia cells. It is noteworthy that the mice treated with antibody of the highest affinity, IMC-1121, survived the longest period of time, followed by mice treated with IMC-2C6 and IMC-1C11. Taken together, our data suggest that anti-KDR antibodies may have broad applications in the treatment of both solid tumors and leukemia. It further underscores the efforts to identify antibodies of high affinity for enhanced antiangiogenic and antitumor activities.  相似文献   
58.
The incidence of atherosclerosis can be modified by diet, and plant-derived proteins have a beneficial effect, but the underlying mechanisms remain unclear. It has been suggested that oxidized LDL (oxLDL) and autoantibodies against oxLDL are important in the development of atherosclerosis. We analyzed these factors in rabbits fed a nonpurified diet supplemented with high cholesterol (10.0 g/kg) containing either 270.0 g/kg casein (CAS, n = 10) or 270.0 g/kg soy protein isolate (SPI, n = 10) for 2 mo. Plasma and purified serum LDL from rabbits were analyzed at d 0, 15, 30, 45 and 60 of treatment, and the size of atherosclerotic lesions was evaluated at d 60 of treatment. CAS-fed rabbits had significantly higher plasma cholesterol at d 15-45 and LDL cholesterol levels at d 15 and 30. Levels of trilinolein and phosphatidylcholine hydroperoxides were higher in the LDL fraction of rabbits fed CAS than in those fed SPI. Also, CAS-fed rabbits had higher levels of highly oxidized LDL [monoclonal antibody (mAb) 24-reactive oxLDL] in plasma at d 60, whereas SPI-fed rabbits had higher levels of minimally oxidized LDL (mAb 28-reactive oxLDL) at d 45. These results were consistent with the earlier formation of anti-oxLDL antibodies and the presence of a larger area of atherosclerotic lesion in rabbits fed the CAS diet. These data indicate the importance of both the type of dietary protein used in the induction of atherosclerosis and the relevance of immunologic mechanisms in addition to biochemical and physiologic factors in the pathogenesis of atherosclerosis.  相似文献   
59.
OBJECTIVE: To determine the coverage and focus of cervical cancer screening (Pap smears) in a population-based sample in Brazil. METHODS: Cross-sectional cluster survey covering 1730 women aged 20 years or older with a history of sexual activity. Information was collected on social, demographic and behavioral variables, knowledge of and use of the Pap test. RESULTS: Of women aged 25-59 years, who are the target population of the national cervical cancer screening program, 78.7% had had at least one Pap test in their lifetime, and 68.8% had had a Pap test in the last 3 years. Statistics for focus of the program showed that of the 637 women who reported having a Pap test in the last year, only 20.6% actually required one. The remainder were either outside the age range or had had another test less than 30 months previously. Prevalence of not having been tested in the previous 3 years was highest among black (41.7%) and low-income women (64.3%), and among those at greatest risk for cervical cancer (62.3% for women with three or more risk factors). Focus was inversely related to socioeconomic status. CONCLUSION: Coverage rates were similar to those reported in other national studies, but this is the first report to examine the focus of the national program. We show that 8 of every 10 Pap tests were not necessary. Coverage levels remain unacceptably low among women of low socioeconomic status and those at greatest risk for cervical cancer.  相似文献   
60.
1. 1. This case report of a Chinese male schizophrenic patient describes new side effects that have not been documented previously for patients treated with clozapine. At certain doses of clozapine, the patient showed direct adverse reactions, which include a combination of hyperglycemia, hyperlipemia, and periodic paralysis.
2. 2. In a four-year study of this patient who had no previous episodes of diabetes in his or his family history, the authors found that these symptoms disappeared upon withdrawal of clozapine and relapsed with re-treatment of the drug.
3. 3. This study indicates that hyperglycemia, hyperlipemia, and periodic paralysis may need to be monitored on patients treated with clozapine.
  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