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   19191篇
  免费   1021篇
  国内免费   48篇
耳鼻咽喉   184篇
儿科学   505篇
妇产科学   796篇
基础医学   2544篇
口腔科学   503篇
临床医学   1719篇
内科学   3793篇
皮肤病学   415篇
神经病学   2017篇
特种医学   955篇
外国民族医学   3篇
外科学   2745篇
综合类   132篇
一般理论   38篇
预防医学   1230篇
眼科学   229篇
药学   1231篇
中国医学   28篇
肿瘤学   1193篇
  2022年   141篇
  2021年   227篇
  2020年   164篇
  2019年   233篇
  2018年   321篇
  2017年   232篇
  2016年   285篇
  2015年   313篇
  2014年   496篇
  2013年   619篇
  2012年   953篇
  2011年   995篇
  2010年   517篇
  2009年   525篇
  2008年   755篇
  2007年   860篇
  2006年   974篇
  2005年   842篇
  2004年   766篇
  2003年   800篇
  2002年   757篇
  2001年   674篇
  2000年   711篇
  1999年   508篇
  1998年   270篇
  1997年   230篇
  1996年   141篇
  1995年   149篇
  1994年   115篇
  1993年   155篇
  1992年   361篇
  1991年   315篇
  1990年   348篇
  1989年   332篇
  1988年   301篇
  1987年   306篇
  1986年   284篇
  1985年   258篇
  1984年   178篇
  1983年   166篇
  1979年   203篇
  1978年   123篇
  1977年   119篇
  1976年   119篇
  1975年   162篇
  1974年   174篇
  1973年   148篇
  1972年   149篇
  1971年   120篇
  1970年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
I contend that although the Luborsky et al. findings on the Dodo bird verdict are noteworthy, the methodology on which they are based is significantly delimited. Amplifying Luborsky et al.'s moderate recognition of that delimitation, I propose a qualitative complement to the extant research. I call this complement "amalgamated" qualitative research and propose that it will deepen, clarify, and contextualize Luborsky et al.'s enigmatic findings. Until this amalgam is implemented, therapy research will be relegated to impressions rather than fine-grained illuminations.  相似文献   
43.
In a retrospective study, 1.173 fractures of the proximal femur, which had been treated surgically, were analysed in two periods from 1975 to 1991 and from 1992 to 2000. The influence on mortality of preoperative risk factors and primary treatment with total hip replacement (THR), even in cases of pertrochanteric fractures, was analysed by stepwise logistic regression. In the later period, mortality within 90 days was 13.1%, and within 1 year 22.2%. Rejection of hemiendoprosthesis in high-risk patients with intracapsular fractures increased the mortality rate from 6.3% to 11.8%. The introduction of dynamic hip screws instead of Ender nails led to a reduction of mortality from 16.5 to 7.1%. Higher mortality after THR (27.6%) compared to osteosynthesis (15.5%) in pertrochanteric femur and lateral neck fractures was due to higher age and increased risk factors. Although the influence of some risk factors could be reduced, age, sex and morbidity influenced the outcome more than surgical treatment. THP, even after pertrochanteric fractures, is reasonable if it guarantees a quick and enduring mobilisation of the patient. Bicentric bipolar prostheses are recommended for high risk patients.  相似文献   
44.
GM1 ganglioside is believed to be important in promoting the recovery of neurons from injury. The present study assesses the ability of GM1 to repair or prevent the damage of dopamine neurons caused by the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Treatment of mesencephalic cell cultures with 2.5 μM MPP+ resulted in the loss of 30% of tyrosine hydoxylase (TH) immunoreactive neurons. In contrast, cultures administered 100 μM GM1 ganglioside for 3 days after toxin treatment contained nearly control numbers of TH+ neurons (97%). This reparative effect of GM1 was reflected in parallel increases in TH enzyme activity, dopamine and dopac levels. Cultures sustaining greater insult from higher doses of MPP+ (5.0–10.0 μM) did not benefit from ganglioside treatment, suggesting that rescue by GM1 depended on the degree of initial damage to cells. Moreover, the timing of ganglioside treatment was critical; pretreatment with GM1 alone did not prevent or attenuate the damage caused by subsequent incubation in 2.5 μM MPP+.  相似文献   
45.
46.
Data in the literature on the prevalence of hereditary deficiency of the natural coagulation inhibitors are conflicting. We conducted a prospective study on 680 consecutive patients with a history of venous thrombosis to determine the prevalence of hereditary deficiency of antithrombin III (AT III), protein C(PC) and protein S(PS) and to establish selection criteria for rational patient screening. The mean age of the patients at investigation was 44.3 +/- 15.4 years, while that at the first thrombotic event was 38.5 +/- 14.8 years. The total prevalence of inhibitor deficiency states was 48/680 (7.1%). 19/680 patients (2.8%) had AT III-deficiency, 17 (2.5%) PC-deficiency, nine (1.3%) PS-deficiency and three (0.4%) a combined deficiency. In 37/48 deficient patients family studies were performed and the hereditary nature was established in 19 cases (2.8% of total patient population, six with AT III-deficiency, eight with PC-deficiency, four with PS-deficiency and one with a combined deficiency). Family studies in these 19 patients revealed 46 additional individual patients with a hereditary deficiency state. A positive family history was found in 15/19 (79%) with a proven hereditary deficiency state, in 153/619 (25%) of non-deficient patients and in 11/29 (38%) of deficient patients without established hereditary nature. The mean age at the first thrombotic event was significantly lower in patients with a hereditary deficiency state (26.8 years) compared with the other two groups (39.0 and 39.7 years, respectively). In all patients with a hereditary deficiency the first thrombotic event occurred before the age of 45 years.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
47.
48.
Sporadic amyotrophic lateral sclerosis is an idiopathic human degenerative disease of spinal cord and brain motor neurons. Prior studies demonstrated that most patients with amyotrophic lateral sclerosis posses immunoglobulins that bind to purified L-type voltage-gated calcium channels, that titers of anti–voltage-gated calcium channel antibodies correlate with disease progression rates, and that amyotrophic lateral sclerosis patient-derived antibodies (ALS IgG) produce electrophysiological changes in the function of voltage-gated calcium channels. Using Western transfer immunoblots and enzyme-linked immunosorbent assays, the calcium ionophore–forming α1 subunig of the voltage-gated calcium channel is now identified as the major voltage-gated calcium channel antigen to which ALS IgG binds. Additionally, the binding of an L-type voltage-gated calcium channel α1 subunit–directed monoclonal antibody, which itself mimics the effects of ALS IgG on skeletal muscle voltage-gated calcium channel currents, is selectively prevented by preaddition of ALS IgG. Voltage-gated calcium channel–binding IgG from patients with Lambert-Eaton myasthenic syndrome appears to be differentiated from ALS IgG by the reactivity of the former to both α1 and β subunits of the calcium channel. These assays provide further evidence linking amyotrophic lateral sclerosis to an autoimmune process, and suggest one means to differentiate immunoglobulins from patients with amyotrophic lateral sclerosis from those of patients with another autoimmune disease expressing calcium channel antibodies.  相似文献   
49.
The effect of diuretics, mainly chlorthalidone, on serum cholesterol was studied in 7,006 of the Hypertension Detection and Follow-up Program (HDFP) hypertensive patients not on antihypertensive medication at baseline. Several investigators have reported that diuretic therapy increases serum cholesterol in treated subjects. However, data from two long-term studies indicated that no increase in cholesterol occurred after two years of diuretic treatment. In the present study, yearly changes in serum cholesterol in hypertensives treated with diuretics were observed. The results were in agreement with those reported from both short-term and long-term studies, in that a significant increase in cholesterol was observed in six months to one year into the study but not from the second to the fifth year of therapy. In fact, the serum cholesterol levels were the same as baseline values after two years of drug treatment and decreased slightly thereafter. In the untreated group, no change or a decrease in serum cholesterol was observed during the course of the study. The possible causes for changes in serum cholesterol concentration such as regression to the mean, change in body weight, baseline cholesterol concentration, and the action mechanism of diuretic drugs are discussed.  相似文献   
50.
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